Water Quality Testing in RO Systems – MyronLMeters.com

Tweet Water quality testing is vital to the design of an efficient, cost-effective RO system, and is one of the best ways to preserve system life and performance. Using an accurate Total Dissolved Solids (TDS) measurement to assess the system load prevents costly mistakes up front. The TDS measurement gives users the information they need [...]

Water quality testing is vital to the design of an efficient, cost-effective RO system, and is one of the best ways to preserve system life and performance.

Using an accurate Total Dissolved Solids (TDS) measurement to assess the system load prevents costly mistakes up front. The TDS measurement gives users the information they need to determine whether or not pretreatment is required and the type of membrane/s to select. Ultrameter™ and ULTRAPEN PT1™ Series TDS instruments feature the unique ability to select from 3 industry standard solution models: 442 Natural Water™ NaCl; and KCl. Choosing the model that most closely matches the characteristics of source water yields measurements accurate enough to check and calibrate TDS monitor/controllers that can help alert to system failures, reducing downtime and increasing productivity. The same instruments provide a fast and accurate test for permeate TDS quality control. Measuring concentrate values and analyzing quality trends lets users accurately determine membrane usage according to the manufacturer’s specifications so they can budget consumption correctly. These daily measurements are invaluable in detecting problems with system performance where changes in the ionic concentration of post-filtration streams can indicate scaling or fouling. System maintenance is generally indicated if there is either a 10-15% drop in performance or permeate quality as measured by TDS.

Thin-film composite membranes degrade when exposed to chlorine. In systems where chlorine is used for microbiological control, the chlorine is usually removed by carbon adsorption or sodium bisulfite addition before membrane filtration. The presence of any chlorine in such systems will at best reduce the life of the membrane, thus, a target of 0 ppm free chlorine in the feedwater is desirable.

ORP gives the operator the total picture of all chemicals in solution that have oxidizing or reducing potential including chlorine, bromine, chloramines, chlorine dioxide, peracetic acid, iodine, ozone, etc. However, ORP can be used to monitor and control free chlorine in systems where chlorine is the only sanitizer used. ORP over +300 mV is generally considered undesirable for membranes. Check manufacturer’s specifications for tolerable ORP levels.

An inline ORP monitor/controller placed ahead of the RO unit to automatically monitor for trends and breakthroughs coupled with spot checks by a portable instrument will prevent equipment damage and failure. Myron L 720 Series II™ ORP monitor/controllers can be configured with bleed and feed switches as well as visible and audible alarms.

Ultrameter and ULTRAPEN portable handhelds are designed for fast field testing and are accurate enough to calibrate monitor/controllers. Our measurement methods are objective and have superior accuracy and convenience when compared to colorimetric methods where determination of equivalence points is subjective and can be skewed by colored or turbid solutions.

Monitoring pH of the source water will allow users to make adjustments that optimize the performance of antiscalants, corrosion inhibitors and anti-foulants. Using a 720 II Series Monitor/controller to maintain pH along with an Ultrameter Series or ULTRAPEN PT2™ handheld to spot check pH values will reduce consumption of costly chemicals and ensure their efficacy.

Most antiscalants used in chemical system maintenance specify a Langelier Saturation Index maximum value. Some chemical manufacturers and control systems develop their own proprietary methods for determining a saturation index based on solubility constants in a defined system. However, LSI is still used as the predominant scaling indicator because calcium carbonate is present in most water. Using a portable Ultrameter III 9PTKA™ provides a simple method for determining LSI to ensure the chemical matches the application.

The Ultrameter III 9PTKA computes LSI from independent titrations of alkalinity and hardness along with electrometric measurements of pH and temperature. Using the 9PTKA LSI calculator, alterations to the water chemistry can be determined to achieve the desired LSI. Usually, pH is the most practical adjustment. If above 7, acid additions are made to achieve the pH value in the target LSI. Injections are made well ahead of the RO unit to ensure proper mixing and avoid pH hotspots. A Myron L 720 Series II pH Monitor/controller will automatically detect and divert solution with pH outside the range of tolerance for the RO unit. ULTRAPEN PT2, TechPro II and Ultrameter Series instruments can be used to spot check and calibrate the monitor/controller as part of routine maintenance and to ensure uniform mixing.

Water hardness values indicate whether or not ion exchange beds are required in pretreatment. Checking hardness values directly after the softening process with the Ultrameter III 9PTKA ensures proper functioning and anticipates the regeneration schedule.

Alkalinity is not only important in its effect on the scaling tendency of solution, but on pH maintenance. Additions of lime are used to buffer pH during acid injection. Use a 9PTKA to measure alkalinity values for fast field analysis where other instrumentation is too cumbersome to be practical.

Though testing and monitoring pressure is a good way to evaluate system requirements and performance over time, measuring other water quality parameters can help pinpoint problems when troubleshooting. For example, if the pressure differential increases over the second stage, the most likely cause is scaling by insoluble salts. This means that any degradation in performance is likely due to the dissolved solids in the feed. Using a 9PTKA to evaluate LSI and calculate parameter adjustments is a simple way to troubleshoot a costly problem.

Myron L Meters saves you 10% on all Ultrameters and Ultrapens when you order online at MyronLMeters.com, where you can find the complete selection of Myron L meters, including the Ultrameter III 9PTKA.

Original story from International Filtration News V 32, no. 2

 

Myron L Meters Water Industry Resources – MyronLMeters.com

TweetSoon Myron L Meters will be adding a Water Industry Resources page to MyronLMeters.com.  The page will feature links to water industry events, water industry associations, and related technical resources.  Please look over our draft page below and  suggest anything we might be missing. Be sure to check back with us periodically for new features [...]

Soon Myron L Meters will be adding a Water Industry Resources page to MyronLMeters.com.  The page will feature links to water industry events, water industry associations, and related technical resources.  Please look over our draft page below and  suggest anything we might be missing. Be sure to check back with us periodically for new features and changes, including our upcoming Myron L Meters Users Forum.

Myron L Meters Water Industry Resources

 Blog

http://blog.myronlmeters.com/

 

Manuals and MSDS

http://www.myronlmeters.com/Articles.asp?ID=263

 

Video Channel

http://www.youtube.com/myronlmeters

 

Application Bulletins

https://www.myronlmeters.com/Articles.asp?ID=265

 

Users Group

 

Water Industry News

http://waterindustrynews.com/

 

Pinterest

http://pinterest.com/myronlmeters/boards/

 

Twitter

https://twitter.com/MyronLMeters

 

Water Science and Conservation

 

Water Conservation News - Science Daily

http://www.sciencedaily.com/news/earth_climate/water/

 

U.S. Department of the Interior | Bureau of Reclamation

http://www.usbr.gov/WaterSMART/

 

Environmental Protection Agency

http://www2.epa.gov/science-and-technology/water-science

 

Clean Water Network

http://www.cleanwaternetwork.org/

 

Soil and Water Conservation Society

http://www.swcs.org/

 

Partnership for Water Conservation

http://www.partners4water.org/

 

Nature Conservancy Conservation Gateway

http://www.conservationgateway.org/Pages/default.aspx

 

 

Water Products Suppliers

 

Pumps:                                  PulsafeederPumps

                                             http://www.pulsafeederpumps.com/

 

Storage Tanks:                       PeabodyStorageTanks

                                             http://www.peabodystoragetanks.com/Default.asp

 

Water Industry Events
Apr 14 – Apr 18, 2013

Miscellaneous | Miscellaneous

23th Annual Practical Membrane / Filtration & Separations Technologies Short Course

College Station, TX
Apr 16 – Apr 18, 2013

AWWA Section | Section Conference

New York Section 2013 Annual Conference

Saratoga Springs, NY
Apr 16 – Apr 18, 2013

Miscellaneous | Seminar

HEC-HMS

Chicago, IL
Apr 22 – Apr 24, 2013

AWWA | Seminar

SOLD OUT Financial Management Seminar, San Diego, California

San Diego, CA
Apr 23 – Apr 25, 2013

AWWA Section | Section Conference

Pennsylvania Section 2013 Annual Conference

Hershey, PA
Apr 25 – Apr 25, 2013

Miscellaneous | Miscellaneous

Native Landscape Design for Stormwater

Milwaukee, WI
Apr 29 – May 02, 2013

AWWA Section | Annual Meeting

Alaska Section 2013 Annual Conference

Anchorage, AK
May 01 – May 03, 2013

AWWA Section | Section Conference

Arizona Section 2013 Annual Conference

Glendale, AZ
May 06 – May 07, 2013

Miscellaneous | Miscellaneous

17th Annual Water Reuse & Desalination Research Conference

Phoenix, AZ
May 06 – May 08, 2013

Miscellaneous | Speciality Conferences

2013 ABPA Education Conference & Trade Show

Phoenix, AZ
May 06 – May 10, 2013

Miscellaneous | Miscellaneous

2013 West Regional Conference

Seattle, WA
May 07 – May 09, 2013

AWWA Section | Annual Meeting

Montana Section 2013 Annual Conference

Great Falls, MT
May 07 – May 07, 2013

Miscellaneous | Speciality Conferences

SCMA SWAT Training For Operators Workshop

Granbury, TX
May 08 – May 10, 2013

AWWA Section | Annual Meeting

Hawaii Section 2013 Annual Conference

Honolulu, HI

 

May 08 – May 10, 2013

AWWA Section | Section Conference

Pacific Northwest Section 2013 Annual Conference

Spokane, WA
May 08 – May 10, 2013

Miscellaneous | Seminar

Inspection and Assessment of Dams

Seattle, WA
May 09 – May 09, 2013

Miscellaneous | Miscellaneous

Watershed Planning – Putting the Pieces Together

Milwaukee, WI
May 09 – May 09, 2013

Miscellaneous | Miscellaneous

Smart Water for Smart Cities – A Workshop

Ellicot City, MD
May 09 – May 09, 2013

Miscellaneous | Speciality Conferences

SCMA I Scream, You Scream, We All Scream For Membranes Workshop

Tuttle, OK
May 16 – May 17, 2013

Miscellaneous | Annual Meeting

Water and Agriculture

Palos Verdes, CA
May 19 – May 22, 2013

AWWA Section | Section Conference

West Virginia Section 2013 Annual Conference

Daniels, WV
May 20 – May 20, 2013

Miscellaneous | Speciality Conferences

AMTA/SEDA Joint Technology Transfer Workshop “Application of Membrane Technologies in the Chesapeake Region”

Chesapeake, VA
May 21 – May 23, 2013

Miscellaneous | Miscellaneous

Appalachian Underground Corrosion Short Course (AUCSC 2013)

Morgantown, WV
May 22 – May 24, 2013

AWWA Section | Annual Meeting

Connecticut Section 2013 Annual Conference

Saratoga Springs, NY
May 30 – May 30, 2013

Miscellaneous | Miscellaneous

Water Law for Sustainable Management

Milwaukee, WI
Jun 09 – Jun 13, 2013

AWWA | Annual Meeting

2013 Annual Conference & Exposition

Denver, CO
Jun 24 – Jun 25, 2013

Miscellaneous | Speciality Conferences

2013 AWRA Summer Specialty Conference Environmental Flows

Hartford, CT
Jul 09 – Jul 10, 2013

AWWA | Speciality Conferences

NWMOA MBR Operator Training Workshop

Pendleton, OR
Aug 04 – Aug 04, 2013

Miscellaneous | Annual Meeting

Association of Clean Water Administrators

Sante Fe, NM
Sep 08 – Sep 12, 2013

Miscellaneous | Speciality Conferences

Dam Safety 2013

Providence, RI
Sep 09 – Sep 12, 2013

AWWA Section | Annual Meeting

Virginia Section 2013 Annual Conference

Richmond, VA
Sep 10 – Sep 13, 2013

AWWA Section | Section Conference

Michigan Section 2013 Annual Conference

Lansing, MI
Sep 11 – Sep 13, 2013

AWWA Section | Section Conference

Intermountain Section AWWA

Sun Valley, Idaho
Sep 15 – Sep 18, 2013

Miscellaneous | Symposium

North American Membrane Society 23rd Annual Meeting

Denver
Sep 15 – Sep 18, 2013

Miscellaneous | Symposium

28th Annual WateReuse Symposium

Denver, Colorado
Sep 15 – Sep 18, 2013

AWWA | Speciality Conferences

2013 DSS/Emergency Preparedness and Security Conf.

Itasca, IL
Sep 22 – Sep 25, 2013

Miscellaneous | Annual Meeting

World Congress 2013

Las Vegas, NV
Sep 23 – Sep 25, 2013

Miscellaneous | Annual Meeting

NWMOA 1st Annual Symposium – “Getting the Best from Your Membrane Treatment Plant”

Vancouver, WA
Sep 29 – Oct 03, 2013

Miscellaneous | Speciality Conferences

84th Annual Education and Business Conference

Kansas City, MO
Oct 01 – Oct 03, 2013

Miscellaneous | Speciality Conferences

NRWA WaterPro Conference

Seattle, WA
Oct 02 – Oct 04, 2013

Miscellaneous | Speciality Conferences

6th WaterSmart Innovations Conference and Exposition

Las Vegas, NV
Oct 13 – Oct 15, 2013

AWWA Section | Section Conference

Alabama-Mississippi Annual Conference

Tunica Resorts, MS
Nov 03 – Nov 07, 2013

AWWA | Speciality Conferences

2013 Water Quality Technology Conference

Long Beach, CA
Nov 04 – Nov 08, 2013

Miscellaneous | Miscellaneous

2013 Irrigation Show & Education Conference

Austin

 

 

Water Industry Associations

 

American Fisheries Society

2. The Chlorine Institute
3. Conservation International
4. Environmental Assessment Association
5. Environmental Council of the States
6. Environmental Law Institute
7. The Groundwater Foundation
8. Ground Water Protection Council
9. Institute of Professional Environmental Practice

10.Irrigation Association

11.NARUC Committee on Water

12.National Association of Conservation Districts

13.National Association of Counties

14.National Association of Environmental Professionals

15.National Association of Pipe Fabricators

16.National Association of Water Companies

17.National Council for Science and the Environment

18.National Drinking Water Clearinghouse

19.National Drought Mitigation Center

20.National Federation of Municipal Analysts

21.National Fire Protection Association

22.National Ground Water Association
National Institute for the Environment

23.National Institutes for Water Resources

24.National Rural Water Association

25.National Small Flows Clearinghouse

26.National Water Research Institute - Canada.

27.National Water Resources Association

28.Renewable Natural Resources Foundation

29.Soil and Water Conservation Society

30.State Water Resources Research Institutes

31.Water and Wastewater Equipment Manufacturers Association

 

 

American Filtration and Separations Society (AFS)
The premier organization in North America dedicated to R&D, problem solutions and technology transfer in fluid-particle separation for the benefit of industrial processes, individual health and a clean environment.

 

American Ground Water Trust is a nonprofit educational organization dedicated to promoting efficient and effective ground water management and provides educational information about ground water issues that are important to well owners.www.agwt.org

 

American Institute of Hydrology

 

American Public Works Association

 

American Society of Irrigation Consultants

 

American Water Resources Association

 

American Water Works Association (AWWA)

 

Association of Metropolitan Water Agencies

 

Association of Metropolitan Sewerage Agencies

 

Association of State Drinking Water Administrators

 

Association of State and Interstate Water Pollution Control Administrators

 

Association of Water Technologies

 

AWWA Research Foundation

California Water Operators Association (CWOA)
A professional association dedicated to helping water and wastewater operators in California thru education, public policy, wages, benefits, training.

Caribbean Water and Wastewater Association (CWWA)
The CWWA encourages the study, research and development in water supply and wastewater disposal, and the publication of the results of such work, so as to provide for appropriate and dynamic technological advances in the Caribbean.

Florida Water and Pollution Control Operators Association, Region 8
One of the leading water and wastewater professional training organizations in Florida for over 5,000 professionals that work in the public, private and government utilities.

Instrument Society of America (ISA)
The international society for measurement, control, instrumentation and automation.

 

International Bottled Water Association is the authoritative source of information about all types of bottled waters.

www.bottledwater.org

Regional Bottled Water Associations:
NEBWA – Northeastern Bottled Water Association
SEBWA – Southeastern Bottled Water Association
MABWA – Mid-America Bottled Water Association
CSBWA – Central States Bottled Water Association
NWBWA – Northwestern Bottled Water Association
CBWA – Canadian Bottled Water Association

International Private Water Association (IPWA)
Promoting private sector participation in water utilities.

The Irrigation Association (IA)
Formed more than 50 years ago to improve the products and practices used to manage water resources and to help shape the worldwide business environment of the irrigation industry.

Kentucky Water & Wastewater Operators Association (KWWOA)
A not-for-profit association organized in the fall of 1958.  The KWWOA was created by a group of operators from the drinking and wastewater industry.

Maine Lagoon Systems
The mission of the Maine Lagoon Systems website is to promote clean water resources through the enhanced communication of wastewater lagoon system operators in the state of Maine and beyond.

Maine Wastewater Control Association (MWCA)
An association of over 650 members consisting of municipal and industrial operators, consultants, students, and regulatory officials. The purpose is to facilitate communication of ideas and the preservation of Maine’s waterways.

Measurement, Control and Automation Association   (MCAA)

NAWC (National Association of Water Companies)

http://www.nawc.org/

 

National Ground Water Association (NGWA) is a trade association for ground water professionals including well drillers, pump installers, geologists and other scientists to promote responsible development, use and management of ground water resources. www.ngwa.org

 

National Institute for the Environment

 

National Institutes for Water Resources

 

National Rural Water Association
National Small Flows Clearinghouse
Helping America’s small communities meet their wastewater needs.

 

National Water Research Institute - Canada.

 

National Water Resources Association
Northeast Rural Water Association (NeRWA)
Started in 1982, a nonprofit association of water and wastewater systems in Massachusetts, New Hampshire, and Vermont. Among its many services, We offer training and onsite technical assistance to operators, managers, owners and boards.

South Carolina Rural Water Association (SCRWA)
Providing free training to water and wastewater operators in South Carolina, through cooperative agreements with NRWA and USEPA. Offering vendors opportunities to network with utility companies in our state. Offering utilities assistance with water & wastewater issues from an operational to a managerial level.

 

Water and Wastewater Equipment Manufacturers Association

http://www.wwema.org/

Water Design-Build Council (WDBC)
The Water Design-Build Council supports the development and rehabilitation of the nation’s municipal water and wastewater systems by using the design-build project delivery method.  Our mission is to promote best practices for design-build to facilitate productive and collaborative relationships between service providers and governments.

 

Water Education Foundation

 

Water Environment Federation (WEF)
Founded in 1928, the Water Environment Federation (WEF) is a not-for-profit technical and educational organization with members from varied disciplines who work toward the WEF vision of preservation and enhancement of the global water environment.

 

Water Environment Research Foundation

 

Water Environment WEB - Water Environment Federation

 

Water Industry Council

 

Water Organizations - [UWIN]

 

Water Quality Association (WQA)
A not-for-profit international trade association representing the residential, commercial, industrial, and small community water treatment industry. WQA maintains a close dialogue with other organizations representing different aspects of the water industry in order to best serve consumers, government officials, and industry members.

 

 

 

Regional Water Quality Associations:
EWQA – Eastern Water Quality Association
FWQA – Florida Water Quality Association
Missouri WQA – Missouri Water Quality Association
PWQA – Pacific Water Quality Association
TWQA – Texas Water Quality Association

 

 

 

Water Utility Benchmarking Association

 

The Watershed Management Council

 

Industry Publications:

Water Quality Products
www.wqpmag.com

Water Technology
www.watertechonline.com

Water Conditioning and Purification
www.wcponline.com

Food Processing Magazine
www.foodprocessing.com

ALN Magazine
www.alnmag.com

The Bottled Water Reporter
www.ibwa.org

 

Journal of Hydroinformatics

Journal of Water and Health

Journal of Water and Climate Change

Journal of Water Reuse and Desalination

Journal of Water Sanitation and Hygiene for Development

Journal of Water Supply: Research and Technology-AQUA

Hydrology Research

Water21

Water Asset Management International

Water Practice and Technology

Water Policy

Water Quality Research Journal of Canada

Water Research

Water Science and Technology

Water Science and Technology: Water Supply

 

Water Systems Council is a national nonprofit organization focused solely on household wells and small water well systems.

www.watersystemscouncil.org

Water Utility Management International

Water Intelligence Online
Government Information Sources

EPA Safe Drinking Water Act List of Primary and Secondary Contaminants, Health Effects, and Sources:

www.epa.gov/safewater/mcl.html

 

US Water Partnership: Department of State

http://www.state.gov/e/oes/rls/fs/2012/186581.htm

 

US Department of the Interior: Water Challenges

http://www.doi.gov/whatwedo/water/index.cfm

 

US Army Corps of Engineers: Water Resources Development

http://www.usace.army.mil/About/History/BriefHistoryoftheCorps/WaterResourcesDevelopment.aspx

 

Water Resources of the United States
http://water.usgs.gov

 

USGS Water Data for the Nation
http://waterdata.usgs.gov/nwis

 

National Water Quality Assessment Program
http://water.usgs.gov/nawqa/

 

US Bureau of Reclamation
http://www.usbr.gov

 

United States Environmental Protection Agency Water Resources
http://water.epa.gov

 

National Climatic Data Center
http://www.ncdc.noaa.gov/

 

National Water and Climate Center
http://www.wcc.nrcs.usda.gov/

 

US Drought Portal
http://www.drought.gov/drought/

 

CDC Healthy Water Portal
http://www.cdc.gov/healthywater/

 

 

Water Industry Training

 

Water Industry Whitepapers and Information

NAWC

http://www.nawc.org/knowledge-center/documents-and-publications/all-document.aspx

 

The Water and Wastewater Online Training Center is a virtual campus providing quality and targeted online training to meet the information needs of the water and wastewater treatment professional.

http://www.waterandwastewater.com/online_training/

 

Texas A&M Engineering Extension Service (Water and Wastewater)

http://www.teex.org/teex.cfm?pageid=EUprog&area=EU&templateid=1268

 

EPA Small Water Systems Training & Technical Assistance Grant

NO-COST EPA Safe Drinking Water Act Training

http://teexweb.tamu.edu/teex-third.cfm?area=EU&templateid=478

 

The Office of Water Programs at the California State University, Sacramento, College of Engineering and Computer Science provides distance learning courses for persons interested in the operation and maintenance of drinking water and wastewater facilities.

http://www.owp.csus.edu/courses/catalog.php

 

Kansas Basics Course for Small Public Drinking Water Systems

http://www.waterhelp.org/ks/kdhe/

 

WEF offers online education and webcasts here:

http://www.wef.org/onlineeducation/default.aspx

 

Water Industry Training Specialists are a California Corporation in the business of training and certifying Backflow Technicians and Cross-Connection Control Inspectors. 

https://www.backflowschool.com/

 

Environmental-Expert.com hosts several courses from different companies in industrial wastewater, water treatment, and environmental engineering.

http://www.environmental-expert.com/training/keyword-industrial-wastewater-182

 

Plumbing Engineer

http://www.plumbingengineer.com/white.php

 

Bitpipe.com

http://www.bitpipe.com/tlist/Utilities-Industry.html

 

Water-Technology.net

http://www.water-technology.net/downloads/whitepapers/

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pool Draining Tips to Protect Water Quality – MyronLMeters.com

TweetMyronLMeters.com has the most advanced lineup of pool analysis meters for the professional pool maintenance technician from the Ultrapen to the PoolPro PS9. Pool Draining Tips to Protect Water Quality With summer right around the corner, many swimming pool owners will be readying their swimming pools in anticipation of the season’s heat. As part of [...]

MyronLMeters.com has the most advanced lineup of pool analysis meters for the professional pool maintenance technician from the Ultrapen to the PoolPro PS9.

Pool Draining Tips to Protect Water Quality

With summer right around the corner, many swimming pool owners will be readying their swimming pools in anticipation of the season’s heat. As part of this process, some pool owners like to drain old swimming pool water which has been sitting all winter. Though not a necessary task, the following tips are provided for you to properly drain pool water in order to protect the water resources in your community.

Whenever possible, it is best to drain your pool onto your landscape. This recycles your pool water, conserves irrigation water, and avoids the environmental risks associated with draining your pool to the street. Before draining your pool water to the street or to your landscape, be sure to follow the guidelines outlined below.

While draining pool water to the street is a common practice, it can prove harmful to the environment if the pool owner does not properly plan and prepare prior to draining. When pool water is drained to the street, it can carry other pollutants such as oil, grease, sediment, bacteria and trash down the storm drain and into the nearest creek, river, or the ocean. Swimming pool water also often contains harmful additives and chemicals. If the water is not properly treated to remove these pollutants prior to draining, they can cause further damage to the health of our waterways and to the plants and animals that live there.

Also, prior to draining to the street, residents are asked to sweep the curb and gutter between the discharge point from their yard to the storm drain down hill from their home. This will remove any pollutants from the gutter that may be carried up by the drained pool water to the storm drain.

For chlorine pools, chlorine levels must be lowered to less than 1 part per million prior to draining. This can be done naturally, by simply allowing the pool water to sit in the sun for a minimum of three days. Alternatively, de-chlorination kits can be purchased at home supply stores at a very reasonable cost. These kits have the tools you need to reach the appropriate chlorine levels before draining your pool to the curb and gutter.

Some people have salt water pool systems which may be preferred due to the lower amount of chemicals required for their operation. However, these pools must not be drained to the storm drain system due to their high salt content relative to the fresh water systems they drain into. Total dissolved solids (TDS) must be below 500 parts per million in order to drain into the street.

“Green pools,” which are pools in which algae is growing, also must not be drained to the street. In these instances, algae must first be killed and removed. This is usually done by chlorinating the swimming pool until the algae is gone, then lowering chlorine to the allowable discharge level. Cartridge filters or diatomaceous earth (DE) filters should be rinsed onto a pervious surface such as landscaped areas or grass. While DE is actually beneficial in your garden, it can build up in storm drains and clog them. DE residues can be scooped up and simply thrown in the trash or put to use fending off worms in your garden.

For more information on how to reach acceptable chemical and TDS levels, call your pool maintenance specialist.

If you are a pool maintenance specialist, consider the PoolPro PS9TKA from MyronLMeters.com – the most advanced and comprehensive pool water analysis meter on the market.

 

 

 

 

 

 

 

 

 

Pool Pro PS9TK

Measures 9 Parameters: Conductivity, Mineral/Salts, TDS, Alkalinity, Hardness, LSI, pH, ORP/Free Chlorine, Temperature
LSI Calculator for hypothetical water balance calculations
Wireless data transfer capability with bluDock option
Auto-ranging delivers increased resolution across diverse applications
Adjustable Temperature Compensation and Cond/TDS conversion ratios for user-defined solutions
Nonvolatile memory of up to 100 readings for stored data protection
Date & time stamp makes record-keeping easy
pH calibration prompts alert you when maintenance is required
Auto-off minimizes energy consumption
Low battery indicator
(Includes instrument with case and solutions)

The thermal conductivity enhancement of nanofluids – MyronLMeters.com

TweetThe thermal conductivity enhancement of nanofluids  Abstract Increasing interests have been paid to nanofluids because of the intriguing heat transfer enhancement performances presented by this kind of promising heat transfer media. We produced a series of nanofluids and measured their thermal conductivities. In this article, we discussed the measurements and the enhancements of the thermal [...]

The thermal conductivity enhancement of nanofluids

 Abstract

Increasing interests have been paid to nanofluids because of the intriguing heat transfer enhancement performances presented by this kind of promising heat transfer media. We produced a series of nanofluids and measured their thermal conductivities. In this article, we discussed the measurements and the enhancements of the thermal conductivity of a variety of nanofluids. The base fluids used included those that are most employed heat transfer fluids, such as deionized water (DW), ethylene glycol (EG), glycerol, silicone oil, and the binary mixture of DW and EG. Various nanoparticles (NPs) involving Al₂O₃ NPs with different sizes, SiC NPs with different shapes, MgO NPs, ZnO NPs, SiO₂ NPs, Fe₃O₄ NPs, TiO₂ NPs, diamond NPs, and carbon nanotubes with different pretreatments were used as additives. Our findings demonstrated that the thermal conductivity enhancements of nanofluids could be influenced by multi-faceted factors including the volume fraction of the dispersed NPs, the tested temperature, the thermal conductivity of the base fluid, the size of the dispersed NPs, the pretreatment process, and the additives of the fluids. The thermal transport mechanisms in nanofluids were further discussed, and the promising approaches for optimizing the thermal conductivity of nanofluids have been proposed.

More efficient heat transfer systems are increasingly preferred because of the accelerating miniaturization, on the one hand, and the ever-increasing heat flux, on the other. In many industrial processes, including power generation, chemical processes, heating or cooling processes, and microelectronics, heat transfer fluids such as water, mineral oil, and ethylene glycol always play vital roles. The poor heat transfer properties of these common fluids compared to most solids is a primary obstacle to the high compactness and effectiveness of heat exchangers[1]. An innovative way of improving the thermal conductivities of working media is to suspend ultrafine metallic or nonmetallic solid powders in traditional fluids since the thermal conductivities of most solid materials are higher than those of liquids. A novel kind of heat transfer enhancement fluid, the so-called nanofluid, has been proposed to meet the demands [2].

“Nanofluid” is an eye-catching word in the heat transfer community nowadays. The thermal properties, including thermal conductivity, viscosity, specific heat, convective heat transfer coefficient, and critical heat flux have been studied extensively. Several elaborate and comprehensive review articles and books have addressed thermal transport properties of nanofluids [1,3-6]. Among all these properties, thermal conductivity is the first referred one, and it is believed to be the most important parameter responsible for the enhanced heat transfer. Investigations on the thermal conductivity of nanofluids have been drawing the greatest attention of the researchers. A variety of physical and chemical factors, including the volume fraction, the size, the shape, and the species of the nanoparticles (NPs), pH value and temperature of the fluids, the Brownian motion of the NPs, and the aggregation of the NPs, have been proposed to play their respective roles on the heat transfer characteristics of nanofluids [7-19]. Extensive efforts have been made to improve the thermal conductivity of nanofluids [7-19] and to elucidate the thermal transport mechanisms in nanofluids [20-23].

The authors have carried out a series of studies on the heat transfer enhancement performance of nanofluids. A variety of nanofluids have been produced by the one- or two-step method. The base fluids used include deionized water (DW), ethylene glycol (EG), glycerol, silicone oil, and the binary mixture of DW and EG (DW-EG). Al₂O₃ NPs with different sizes, SiC NPs with different shapes, MgO NPs, ZnO NPs, SiO₂ NPs, Fe₃O₄ NPs, TiO₂ NPs, diamond NPs (DNPs), and carbon nanotubes (CNTs) with different pretreatments have been used as additives. The thermal conductivities of these nanofluids have been measured by transient hot wire (THW) method or short hot wire (SHW) technique. In this article, the experimental results that elucidate the influencing factors for thermal conductivity enhancement of nanofluids are presented. The thermal transport mechanisms in nanofluids and promising approaches for optimizing the thermal conductivity of nanofluids are further presented.

Two techniques have been applied to prepare nanofluids in our studies: two- and one-step techniques. Most of the studied nanofluids were prepared by the two-step technique. During the procedure of two-step technique, the dispersed NPs were prepared by chemical or physical methods first, and then the NPs were added into a specified base fluid, with or without pretreatment and surfactant based on the need. In the preparation of nanofluids containing metallic NPs, one-step technique was employed.

The process was quite simple in the preparation of nanofluids containing oxide NPs like Al₂O₃, ZnO, MgO, TiO₂, and SiO₂ NPs. The NPs were obtained commercially and were dispersed into a base fluid in a mixing container. The NPs were deagglomerated by intensive ultrasonication after being mixed with the base fluid, and then the suspensions were homogenized by magnetic force agitation.

Two-step method was used to prepare graphene nanofluids. The first step was to prepare graphene nanosheets. Functionalized graphene was gained through a modified Hummers method as described elsewhere [24]. Graphene nanosheets were obtained by exfoliation of graphite in anhydrous ethanol. The product was a loose brown powder, and it had good hydrophilic nature. The graphene nanosheets could be dispersed well in polar solvents, like DW and EG, without the use of surfactant. For liquid paraffin (LP)-based nanofluid, oleylamine was used as the surfactant. The fixed quality of graphene nanosheets with different volume fractions was dispersed in the base fluids.

Severe aggregation always takes place in the as-prepared CNTs (pristine CNTs: PCNTs) because of the non-reactive surfaces, intrinsic Von der Waals forces, and very large specific surface areas, and aspect ratios [25]. In CNT nanofluid preparations, surfactant addition is an effective way to enhance the dispersibility of CNTs [26-28]. However, surfactant molecules attaching on the surfaces of CNTs may enlarge the thermal resistance between the CNTs and the base fluid [29], which limits the enhancement of the effective thermal conductivity. The steps involved in the preparation of surfactant-free CNT nanofluids include (1) disentangling the nanotube entanglement and introducing hydrophilic functional groups on the surfaces of the nanotubes by chemical treatments; (2) cutting the treated CNTs (TCNTs) to optimal length by ball milling; and (3) dispersing the treated and cut CNTs into base fluids. CNTs including single-walled CNTs (SWNTs), double-walled CNTs (DWNTs), and multi-walled CNTs (MWNTs) were obtained commercially. Two chemical routes for treating CNTs were used for this study. One is oxidation with concentrated acid, and the other is mechanochemical reaction with potassium hydroxide (KOH). The detailed treatment processes have been described elsewhere [8,30].

Phase transfer method was used to prepare stable kerosene-based Fe₃O₄ magnetic nanofluid. The first step is to synthesize Fe₃O₄ NPs in water by coprecipitation. Oleic acid was added to modify the NPs. When kerosene is added to the mixture with slow stirring, the phase transfer process took place spontaneously. There was a distinct phase interface between the aqueous and kerosene. After the removal of the aqueous phase using a pipette, the kerosene-based Fe₃O₄ nanofluid was obtained [31].

Nanofluids containing copper NPs were prepared using direct chemical reduction method. Stable nanofluids were obtained with the addition of poly(vinylpyrrolidone) (PVP). The diameters of copper NPs prepared by chemical reduction procedure are in the range of 5-10 nm, and copper NPs disperse well with no clear aggregation [32].

Surface modification is always used to enhance the dispersibility of NPs in the preparation of nanofluids. For example, diamond NPs (DNPs) were purified and surface modified by acid mixtures of perchloric acid, nitric acid and hydrochloric acid according to the literature [33] before being dispersed into the base fluids. SiC NPs were heated in air to remove the excess free carbon and their surfaces modified to enhance their dispersibility.

Inconsistent experimental results and controversial arguments arise unceasingly from different groups conducting research on nanofluids, indicating the complexity of the thermal transport in nanofluids. Through an investigation, a large degree of randomness and scatter have been observed in the experimental data published in the open literature. Given the inconsistency in the data, it is impossible to develop a convincing and comprehensive physical-based model that can predict all the trends. To clarify the suspicion on the scattered and wide-ranging experimental results of the thermal conductivity obtained by different groups, it is preferred to screen the measurement technique and procedure to guarantee the accuracy of the obtained results.

Several researchers observed the “time-dependent characteristic” of thermal conductivity [34-36], that is to say, thermal conductivity was the highest right after nanofluid preparation, and then it decreased considerably with elapsed time. We believe that the “time-dependent characteristic” does not represent the essence of thermal conduction capability of nanofluids. The following two factors may account for this phenomenon. The first one is the motion of the remained particle caused by the agitation during the nanofluid preparation. To make a nanofluid homogeneous and long-term stable, it is always subjected to intensive agitation including magnetic stirring and sonication to destroy the aggregation of the suspended NPs. In very short time after nanofluid preparation, the NPs still keep moving in the base fluid (different from Brownian motion). The motion of the remained particle would cause convection and enhance the energy transport in the nanofluids. Second, when a nanofluid is subjected to long-time sonication, its temperature would be increased. The temperature goes down gradually to the surrounding temperature (thermal conductivity measurement temperature). In very short time after the sonication stops, the process has been remaining. Although the temperature decrease is not severe, the thermal conductivity obtained is very sensitive to the temperature decrease when the transient hot-wire technique is used to measured the thermal conductivity. In our measurements, this phenomenon would be observed. When measuring the thermal conductivity at an unequilibrium state, it was found that the measured data might be very different for a nanofluid even at a specific temperature (see 25°C) if the process to reach this temperature is different. If the temperature is increasing, then the datum obtained of the thermal conductivity would be lower than the true value. While the temperature is decreasing, the datum obtained of the thermal conductivity would be higher than the true value. Therefore, keeping a nanofluid stable and initial equilibrium is very important to obtain accurate thermal conductivity data in measurements.

A transient short hot-wire method was used to measure the thermal conductivities of the base fluids (k₀) and the nanofluids (k). The detailed measurement principle, procedure, and error analysis have been described in [37]. In our measurements, a platinum wire with a diameter of 50 μm was used for the hot wire, and it served both as a heating unit and as an electrical resistance thermometer. The platinum wire was coated with an insulation layer of 7-μm thickness. Initially the platinum wire immersed in media was kept at equilibrium with the surroundings. When a regulation voltage was supplied to initiate the measurement, the electrical resistance of the wire changed proportionally with the rise in temperature. The thermal conductivity was calculated from the slope of the rise in the wire’s temperature against the logarithmic time interval. The uncertainty of this measurement is estimated to be within ± 1.0%. A temperature-controlled bath was used to maintain different temperatures of the nanofluids. Instead of monitoring the temperature of the bath, a thermocouple was positioned inside the sample to monitor the temperature on the spot. When the temperature of the sample reached a steady value, the authors waited for further 20 min to make sure that the initial state is at equilibrium. At every tested temperature, measurements were made three times and the average values were taken as the final results. A 20-min interval was needed between two successive measurements. After the above-mentioned careful check on the measurement condition and procedure, the authors could gain confidence on the experimental results.

In the experiment of the study, it was found that the thermal conductivity enhancements of nanofluids might be influenced by multi-faceted factors including the volume fraction of the dispersed NPs, the tested temperature, the thermal conductivity of the base fluid, the size of the dispersed NPs, the pretreatment process, and the additives of the fluids. The effects of these factors are presented in this section.

Particle loading

The idea of nanofluid application originated from the fact that the thermal conductivity of a solid is much higher than that of a liquid. For example, the thermal conductivity of the most used conventional heat transfer fluid, water, is about 0.6 W/m · K at room temperature, while that of copper is higher than 400 W/m · K. Therefore, particle loading would be the chief factor that influences the thermal transport in nanofluids. As expected, the thermal conductivities of the nanofluids have been increased over that of the base fluid with the addition of a small amount of NPs. Figure 1 shows the enhanced thermal conductivity ratios of the nanofluids with NPs at different volume fractions [7,8,38-42]. (k - k₀)/k₀ and φ refer to the thermal conductivity enhancement ratio of nanofluids and the volume fraction of NPs, respectively, in this article. Figure1a presents oxide nanofluids, while Figure 1b presents nonoxide nanofluids. The results show that all the nanofluids have noticeable higher thermal conductivities than the base fluid without NPs. In general, the thermal conductivity enhancement increases monotonously with the volume fraction. For the graphene nanofluid with a volume fraction of 0.05, the thermal conductivity can be enhanced by more than 60.0%. There is an approximate linear relationship between the thermal conductivity enhancement ratios and the volume fraction of graphene nanosheets. The nanofluids containing graphene nanosheets show larger thermal conductivity enhancement than those containing oxide NPs. It demonstrates that graphene nanosheet is a good additive to enhance the thermal conductivity of base fluid. However, the enhancement ratios of nanofluids containing graphene nanosheets are less than those of CNTs with the same loading. Many factors have direct influence on the thermal conductivity of the nanofluid. One of the important factors is the crystal structure of the inclusion in the nanofluid. Graphene is a one-atom-thick planar sheet of sp²-bonded carbon atoms that are densely packed in a honeycomb crystal lattice. The perfect structure of graphene is damaged when graphite is chemically oxidized by treatment with strong oxidants. There is no doubt that the high thermal conductivity is diminished by defects, and the defects have direct influence on the heat transport along the 2-D structure.

Figure 1. Thermal conductivity enhancement ratios of the nanofluids as a function of nanoparticle loading. (a) Oxide nanofluids: MgO-EG [38]; Al₂O₃-EG [7]; ZnO-EG [39]; (b) Nonoxide nanofluids: CNT-EG [8]; DNP-EG [40]; Graphene-EG [41]; Cu-EG [42].

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Temperature

Some studies have demonstrated that the temperature has a great effect on the enhancement of the thermal conductivity for nanofluids. However, there is considerable disagreement in the literature with respect to the temperature dependence of their thermal conductivity. For example, Das et al. reported strong temperature-depended thermal conductivity for water-based Al₂O₃ and CuO nanofluids [43]. The thermal conductivity enhancements of nanofluids containing Bi₂Te₃nanorods in FC72 and in oil had been experimentally found to decrease with increasing temperature [44]. Micael et al. measured the thermal conductivities of EG-based Al₂O₃ nanofluids at temperatures ranging from 298 to 411 K. A maximum in the thermal conductivity was observed at all mass fractions of NPs [45].

Figure 2 shows our measured temperature-depended thermal conductivity enhancements of nanofluids [8,38-42]. For EG-based nanofluids containing MgO, ZnO, SiO₂, and graphene NPs, the thermal conductivity enhancements almost remain constant when the tested temperature changes (see Figure 2a), which means that the thermal conductivity of the nanofluid tracks the thermal conductivities of the base liquid in the experimented temperature range of this study. The thermal conductivity enhancements of DW-EG-based nanofluids containing MgO, ZnO, SiO₂, Al₂O₃, Fe₂O₃, TiO₂, and graphene NPs also appear to have the same behavior. It was further found that kerosene-based Fe₃O₄ nanofluids presented temperature-independent thermal conductivity enhancements. Patel et al. [46] reported that the thermal conductivity enhancement ratios of Cu nanofluids are enhanced considerably when the temperature increases. The experimental results of this study shown in Figure 2b demonstrated similar tendency. At 10°C, the thermal conductivity enhancement of EG based Cu nanofluid with 0.5% nanoparticle loading is less than 15.0%. When the temperature is increased to 60°C, the enhancement reaches as large as 46.0%. Brownian motion of the NPs has been proposed as the dominant factor for this phenomenon. For the EG-based CNT nanofluids, cylindrical nanotubes with large aspect ratios were used as additions. The effect of Brownian motion will be negligible. Typical conduction-based models will give (k - k₀)/k₀, independent of the temperature. However, results shown in Figure 2b illustrate that (k - k₀)/k₀increases, though not drastically, with the temperature. CNT aggregation kinetics may contribute to the observed differences [21]. It is worthy of bearing in mind that the temperatures of the base fluid and the nanofluid should be the same when compared with the thermal conductivities between them. Comparison of the thermal conductivities between the nanofluid at one temperature and the base at another one is meaningless.

Figure 2. Thermal conductivity enhancement varying with the tested temperatures. (a) Oxide nanofluids: MgO-EG [38]; ZnO-EG[39]; Graphene-EG [41]; (b) Nonoxide nanofluids: Cu-EG [42]; CNT-EG[8]; DNP-EG [40].

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Base fluid

Figure 3 shows the relation between the enhanced thermal conductivity ratios of the nanofluids and the thermal conductivities of the base fluids [7,8,40,41]. It is clearly seen that no matter what kind of nanoparticle was used, the thermal conductivity enhancement decreases with an increase in the thermal conductivity of the base fluid. For pump oil (PO)-based Al₂O₃ nanofluid with 5.0% nanoparticle loading, the thermal conductivity can be enhanced by more than 38% compared to that of PO. When the base fluid is substituted with water, the thermal conductivity enhancement achieved is only about 22.0% [7]. A greater dramatic improvement in thermal conductivity of CNT nanofluid is seen for a base fluid with lower thermal conductivity. At 1.0% nanoparticle loading, the thermal conductivity enhancements are 19.6, 12.7, and 7.0% for CNT nanofluids in decene, EG, and DW, respectively. No matter what kind of base fluid is used, the thermal conductivity enhancement of CNT nanofluids is much higher than that for Al₂O₃ nanoparticle suspensions [8] at the same volume fraction. The reason would lie in the substantial difference in thermal conductivity and morphology between alumina nanoparticle and carbon nanotube.

Figure 3. Thermal conductivity enhancement ratios as a function of the thermal conductivities of the base fluids: Al2O3 NFs [7]; CNT NFs [8]; Graphene NFs [41]; DNP NFs [40].

Particle size

Figure 4 presents the thermal conductivity enhancement of the nanofluids as a function of the specific surface area (SSA) of the suspended particles [7]. It is seen that the thermal conductivity enhancement increases first, and then decreases with an increase in the SSA, with the largest thermal conductivity at a particle SSA of 25 m² · g^-1. We ascribe the thermal conductivity change behavior to twofold factors. First, as particle size decreases, the SSA of the particle increases proportionally. Heat transfer between the particle and the fluid takes place at the particle-fluid interface. Therefore, a dramatic enhancement in thermal conductivity is expected because a reduction in particle size can result in large interfacial area. Second, the mean free path in polycrystalline Al₂O₃ is estimated to be around 35 nm, which is comparable to the size of the particle that was used. The intrinsic thermal conductivity of nanosized Al₂O₃ particle may be reduced compared to that of bulk Al₂O₃ due to the scattering of the primary carriers of energy (phonon) at the particle boundary. It is expected that the suspension’s thermal conductivity is reduced with an increase in the SSA. Therefore, for a suspension containing NPs at a particle size much different from the mean free path, the thermal conductivity increases when the particle size decreases because the first factor is dominant. However, when the size of the dispersed NPs is close to or smaller than the mean free path, the second factor will govern the mechanism of the thermal conductivity behavior of the suspension.

Figure 4. Enhanced thermal conductivity ratios as a function of the SSAs: Al2O3-EG [7]; Al2O3-PO [7].

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 5 depicts the thermal conductivity enhancements of nanofluids containing CNTs with different sizes [47]. The base fluid is DW, and the volume fraction of the CNTs is 0.0054. It is observed from Figure 5 that the thermal conductivity enhancements show differences among these three kinds of nanofluids containing SWNTs, DWNTs, and MWNTs as the volume fraction of CNTs is the same. Two influencing factors may be addressed. The first one is the intrinsic heat transfer performance of the CNTs. It is reported that the thermal conductivity of CNTs decreases with an increase in the number of the nanotube layer. The tendency of the thermal conductivity enhancement of the obtained CNT nanofluids accords with that of the heat transfer performance of the three kinds of CNTs. The second one is the alignment of the liquid molecules on the surface of CNTs. There are greater number of water molecules close to the surfaces of CNTs with smaller diameter due to the larger SSA if the volume fractions of CNTs are the same. These water molecules can form an interfacial layer structure on the CNT surfaces, increasing the thermal conductivity of the nanofluid [47].

Figure 5. Thermal conductivity enhancements of nanofluids containing CNTs with different sizes: SWNT-DW [47]; DWNT-DW[47]; MWNT-DW [47].

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pretreatment

In the preparation of nanofluids, solid additives are always subjected to various pretreatment procedures. The initial incentive is to tailor the surfaces of the NPs to enhance their dispersibility, thereby to enhance the stability of the nanofluids. The morphologies would be significantly changed when CNTs were subjected to chemical or mechanical treatments. Theoretical research into the thermal conductivity of composites containing cylindrical inclusions has demonstrated that the morphologies, including the aspect ratio, have influence on the effective thermal conductivity of the composites. Therefore, it can be expected that the thermal conductivity of CNT contained nanofluids would be affected by the pretreatment process.

Figure 6 shows the dependence of the thermal conductivity enhancement on the ball milling time of CNTs suspended in the nanofluids [48]. From theoretical prediction, the thermal conductivity of a composite increases with the aspect ratio of the included solid particles [49-51]. Intuition suggests that increasing the milling time should therefore decrease (k - k₀)/k₀ because of the reduced aspect ratio. Figure 6, however, shows clear peak and valley values in the thermal conductivity enhancement with respect to the milling time for all the studied CNT loadings. For nanofluid at a volume fraction of 0.01, the thermal conductivity enhancements present a peak value of 27.5% and a valley value of 10.4% when the milling times are 10 and 28 h, respectively. The maximal enhancement is intriguingly more than two and half times as the minimal one. Interestingly, when further increased the milling time from 28 to 38 h, (k - k₀)/k₀ increases from the valley value of 10.4 to 12.8%. Though the increment is not pronounced, it illustrates a difference in tendency from that in the milling time range from 10 to 28 h. Temperature-dependent thermal conductivity enhancement data further indicate that, at all the measured temperatures, nanofluid with CNTs milled for 10 h has the largest increment in thermal conductivity. Glory et al. [52] reported that the enhancement of the thermal conductivity noticeably increases when the nanotube aspect ratio increases. However, the thermal conductivity enhancement behavior of our CNT nanofluid is very different and cannot be explained only by the effect of the aspect ratio.

Figure 6. Dependence of the thermal conductivity enhancement on the ball milling time of CNTs suspended in the nanofluids [48].

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The above results suggest other dominant factors that have the influence over the thermal conductivity of the CNT nanofluids. The authors proposed that the nonstraightness and the aggregation would play significantly roles. As is known, the walls of CNTs have similar structure of graphene sheet, and the thermal conductivity of CNTs shows greatly anisotropic behavior. Heat transports substantially quicker through axial direction than through radial direction [53]. For a nonstraight CNT, the high thermal anisotropy of CNTs induces a unique property that individual CNTs are nearly perfect one-dimensional thermal passages with negligibly small heat flux losses during long distance heat conductions [54]. For a nonstraight CNT with length L under a two-end temperature difference, the heat flux q goes through a curled passage. This CNT can be regarded as an equivalent straight thermal passage with a distance of L^e. The same heat flux q is conducted between the two ends of this straight passage. Obviously, the equivalent length L^e depends on the curvature of the actual nanotube in the nanofluid. A concept, straightness ratio η (η = L^e/L), can be adopted to describe the straightness of a curled CNT. The lowest straightness ratio arises when a suspended nanotube forms ring closure [55].

When subjected to ball milling, CNTs were broken and cut short with appropriate average length. The straightness ratio was significantly increased and heat transports more effectively through the CNTs and across the interfaces between the CNT tips and the base fluid, resulting in the highest thermal conductivity enhancement in a nanofluid containing CNTs milled for 10 h. For nanofluids containing relatively straight nanotubes, the influence of the aspect ratio will surpass that of straightness ratio. Therefore, by further treatment on nanotubes with relatively high straightness ratio, the excessive deterioration of the aspect ratio would decrease the thermal conductivity of nanofluids, causing (k - k₀)/k₀ decrease from 10 to 28 h. Recent theoretical analysis has revealed that the aggregation of nanoparticle plays a significant role in deciding (k - k₀)/k₀ [21]. Percolation effects in the aggregates, as highly conducting nanotubes touch each other in the aggregate, help in increasing the thermal conductivity. Our experiments demonstrate that aggregates are the dominant appearance of CNTs when the ball-milling time is increased to 38 h. The aggregation accounts for the increment of thermal conductivity enhancement when the ball-milling time is increased from 28 to 38 h. This result implies that the positive influence of the aggregation surpasses the negative influence of the aspect ratio deterioration.

pH value

For some nanofluids, the pH values of the suspensions have direct effects on the thermal conductivity enhancement. Figure 7 presents the thermal conductivity enhancement ratios at different pH values [7,40]. The results show that the enhanced thermal conductivity increases with an increase in the difference between the pH value of aqueous suspension and the isoelectric point of Al₂O₃ particle [7]. When the NPs are dispersed into a base fluid, the overall behavior of the particle-fluid interaction depends on the properties of the particle surface. For Al₂O₃ particles, the isoelectric point (pH_iep) is determined to be 9.2, i.e., the repulsive forces among Al₂O₃ particles is zero, and Al₂O₃ particles will coagulate together under this pH value. Therefore, when pH value is equal or close to 9.2, Al₂O₃ particle suspension is unstable according to DLVO theory [56]. The hydration forces among particles increase with the increasing difference of the pH value of a suspension from the pH_iep, which results in the enhanced mobility of NPs in the suspension. The microscopic motions of the particles cause micro-convection that enhances the heat transport process. Wensel’s study showed that the thermal conductivity of nanofluids containing oxide NPs and CNTs with very low percentage loading decreased when the pH value is shifted from 7 to 11.45 under the influence of a strong outside magnetic field [14].

Figure 7. Thermal conductivity enhancement ratios at different pH values: Al2O3-DW [7]; DNP-EG [40].

 

 

 

 

 

 

 

 

 

 

 

 

 

 

For DNP-EG nanofluids, it is observed from Figure 7 that the thermal conductivity enhancement increases with pH values in the range of 7.0-8.0. When pH value is above 8.0, there is no obvious relationship between pH value and the thermal conductivity enhancement. In our opinion, the influence of pH value on thermal conductivity is that pH value has a direct effect on the stability of nanofluids. When pH value is below 8.5, the suspension is not very stable, and DNPs are easy to form aggregations. The alkalinity of the solution is helpful to the dispersion and the stability of the nanofluids. In order to verify the above statement, the influence of settlement time on the thermal conductivity enhancement was further investigated. It is found that the thermal conductivity enhancement decreases with elapsed time for DNP-EG nanofluid when pH is 7.0. However, for the stable DNP-EG nanofluids with pH of 8.5, there is no obvious thermal conductivity decrease for 6 months [40].

Surfactant addition

Surfactant addition is an effective way to enhance the stability of nanofluids. Kim’s study revealed that the thermal conductivity decreased rapidly for the instable nanofluids without surfactants after preparation. However, no obvious changes in the thermal conductivity of the nanofluids with sodium dodecyl sulfate (SDS) as surfactant were observed even after 5-h settlement [57]. Assael et al. investigated the thermal conductivities of the aqueous suspension of CNTs. When Sodium dodecyl sulfate (SDS) was employed as the dispersant, the maximum thermal conductivity enhancement obtained was 38.0% for a nanofluid with 0.6 vol% CNT loadings [58]. When the surfactant is substituted with hexadecyltrimethyl ammonium bromide (CTAB), the maximum thermal conductivity enhancement obtained was 34.0% for same fraction of CNT loading [26]. Liu et al. reported that the thermal conductivity of carbon nanotube-synthetic engine oil suspensions is higher compared with that of same suspensions without the addition of surfactant. The presence of surfactant as stabilizer has positive effect on the carbon nanotube-synthetic engine oil suspensions[59].

We used cationic gemini surfactants (12-3(4,6)-12,2Br^-1) to stabilize water-based MWNT nanofluids. These surfactants were prepared following the process described in [60]. Figure 8presents the thermal conductivity enhancement ratios of the CNT-contained nanofluids with different surfactant concentrations. The volume fraction of the dispersed CNTs is 0.1%. The critical micelle concentration of 12-3-12, 2Br^-1 is reported as 9.6 ± 0.3 × 10^-4 mol/l [61]. Ten times critical micelle concentration of 12-3-12, 2Br^-1 is 0.6 wt%. Solutions of 12-3-12, 2Br^-1 with different concentrations (0.6, 1.8, and 3.6 wt% at room temperature) were selected to prepare CNT nanofluids. It is observed that at all the measured temperatures the thermal conductivity enhancement decreases with the surfactant addition. The surfactant added in the nanofluids acts as stabilizer which improves the stability of the CNT nanofluids. However, excess surfactant addition might hinder the improvement of the thermal conductivity enhancement of the nanofluids.

Figure 8. Thermal conductivity enhancement ratios with different surfactant concentrations.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The effect of the structures of cationic gemini surfactant molecules on the thermal conductivity enhancement is shown in Figure 9. The fractions of the dispersed CNTs and the cationic gemini surfactants is 0.1 vol% and 0.6 wt%, respectively. The spacer chain length of the cationic gemini surfactant increase from 3 methylenes to 6 methylenes. It is seen that the thermal conductivity enhancement ratio increases with the decrease of spacer chain length of cationic gemini surfactant. Zeta potential analysis indicates that the CNT nanofluids stabilized by gemini surfactant with short spacer chain length have better stabilities. Increase of spacer chain length of surfactant might give rise to sediments of CNTs in the nanofluids, resulting in the decrease of thermal conductivity enhancement of the nanofluids.

Figure 9. Effect of surfactant structures on the thermal conductivity enhancement ratio.

Nanofluids have great potential for heat transfer enhancement and are highly suited to application in practical heat transfer processes. This provides promising ways for engineers to develop highly compact and effective heat transfer equipments. More and more researchers have paid their attention to this exciting field. When addressing the thermal conductivity of nanofluids, it is foremost important to guarantee the accuracy in the measurement of the thermal conductivity of nanofluids. Two aspects should be considered. The first one is to prepare homogeneous and long-term stable nanofluids. The second one is to keep the initial equilibrium before measuring the thermal conductivity. In general, the thermal conductivity enhancement increases monotonously with the particle loading. The effect of temperature on the thermal conductivity enhancement ratio is somewhat different for different nanofluids. It is very important to note that the temperatures of the base fluid and the nanofluid should be the same while comparing the thermal conductivities between them. With an increase in the thermal conductivity of the base fluid, the thermal conductivity enhancement ratio decreases. Considering the effect of the size of the inclusion, there exists an optimal value for alumina nanofluids, while for the CNT nanofluid, the thermal conductivity increases with a decrease of the average diameter of the included CNTs. The thermal characteristics of nanofluids might be manipulated by means of controlling the morphology of the inclusions, which also provide a promising way to conduct investigation on the mechanism of heat transfer in nanofluids. The additives like acid, base, or surfactant play considerable roles on the thermal conductivity enhancement of nanofluids.

CNTs: carbon nanotubes; DNPs: diamond NPs; DW: deionized water; DWNTs: double-walled CNTs; EG: ethylene glycol; KOH: potassium hydroxide; LP: liquid paraffin; MWNTs: multi-walled CNTs; NPs: nanoparticles; PVP: poly(vinylpyrrolidone); SDS: sodium dodecyl sulfate; SHW: short hot wire; SSA: specific surface area; SWNTs: single-walled CNTs; THW: transient hot wire; TCNTs: treated CNTs.

The authors declare that they have no competing interests.

HQ supervised and participated all the studies. He wrote this paper. WY carried out the studies on the nanofluids containing copper nanoparticles, graphene, diamond nanoparticles, and several kinds of oxide nanoparticles. YL carried out the studies on the nanofluids containing other oxide nanoparticles. LF carried out the studies on the nanofluids containing carbon nanotubes.

This study was supported by the National Science Foundation of China (50876058), Program for New Century Excellent Talents in University (NCET-10-883), and the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning.

1. Daungthongsuk W, Wongwises S: A critical review of convective heat transfer of nanofluids.

Renewable Sustainable Energy Rev 2007, 11:797. Publisher Full Text

1. Jang S, Choi SUS: Effects of Various parameters on nanofluid thermal conductivity.

J Heat Transf 2007, 129:617-623. Publisher Full Text

1. Yu WH, France DM, Routbort JL, Choi SUS: Review and comparison of nanofluid thermal conductivity and heat transfer enhancements.

Heat Transf Eng 2008, 29:432-460. Publisher Full Text

1. Li Y, Zhou J, Tung S, Schneider E, Xi S: A review on development of nanofluid preparation and characterization.

Powder Technol 2009, 196:89-101. Publisher Full Text

1. Wang L, Fan J: Nanofluids research: key issues.

Nanoscale Res Lett 2010, 5:1241-1252. PubMed Abstract | Publisher Full Text |PubMed Central Full Text

1. Zerinc SÖ, Kakac S, Güvenc A: Enhanced thermal conductivity of nanofluids: a state-of-the-art review.

Microfluid Nanofluid 2010, 8:145-170. Publisher Full Text

1. Xie H, Wang J, Xi T, Ai F: Thermal conductivity enhancement of suspensions containing nanosized alumina particles.

J Appl Phys 2002, 91:4568. Publisher Full Text

1. Xie H, Lee H, Youn W, Choi M: Nanofluids containing multi-walled carbon nanotubes and their enhanced thermal conductivities.

J Appl Phys 2003, 94:4971.

1. Patel HE, Das SK, Sundararajan TA, Nair S, George B, Pradeep T: Thermal conductivity of naked and monolayer protected metal nanoparticles based nanofluids: manifestation of anomalous enhancement and chemical effects.

Appl Phys Lett 2003, 83:2931. Publisher Full Text

1. Wen D, Ding Y: Experimental investigation into the pool boiling heat transfer of γ-alumina nanofluids.

J Nanoparticle Res 2005, 7:265. Publisher Full Text

1. Li CH, Peterson GP: Size effect on the effective thermal conductivity of Al₂O₃/Di water nanofluids.

J Appl Phys 2006, 99:084314. Publisher Full Text

1. Wright B, Thomas D, Hong H, Groven L, Puszynski J, Duke E, Ye X, Jin S: Magnetic field enhanced thermal conductivity in heat transfer nanofluids containing Ni coated single wall carbon nanotubes.

Appl Phys Lett 2007, 91:173116. Publisher Full Text

1. Garg J, Poudel B, Chiesa M, Gordon JB, Ma JJ, Wang JB, Ren ZF, Kang YT, Ohtani H, Nanda J, McKinley GH, Chen G: Enhanced thermal conductivity and viscosity of copper nanoparticles in ethylene glycol nanofluid.

J Appl Phys 2008, 103:074301. Publisher Full Text

1. Wensel , Wright B, Thomas D, Douglas W, Mannhalter B, Cross W, Hong H, Kellar J, Smith P, Roy W: Enhanced thermal conductivity by aggregation in heat transfer nanofluids containing metal oxide nanoparticles and carbon nanotubes.

Appl Phys Lett 2008, 92:023110. Publisher Full Text

1. Xie H, Yu W, Li Y: Thermal performance enhancement in nanofluids containing diamond nanoparticles.

J Phys D 2009, 42:095413. Publisher Full Text

1. Shima PD, Philip J, Raj B: Magnetically controllable nanofluid with tunable thermal conductivity and viscosity.

Appl Phys Lett 2009, 95:133112. Publisher Full Text

1. Yu W, Xie H, Chen W: Experimental investigation on thermal conductivity of nanofluids containing graphene oxide nanosheets.

J Appl Phys 2010, 107:094317. Publisher Full Text

1. Kole M, Dey TK: Thermal conductivity and viscosity of Al₂O₃ nanofluid based on car engine coolant.

J Phys D 2010, 43:315501. Publisher Full Text

1. Yeganeh M, Shahtahmasebi N, Kompany A, Goharshadi EK, Youssefi A, Šiller L: Volume fraction and temperature variations of the effective thermal conductivity of nanodiamond fluids in deionized water.

Int J Heat Mass Transf 2010, 53:3186. Publisher Full Text

1. Prasher R, Bhattacharya P, Phelan PE: Thermal conductivity of nanoscale colloidal solutions (nanofluids).

Phys Rev Lett 2005, 94:025901. PubMed Abstract | Publisher Full Text

1. Prasher R, Phelan PE, Bhattacharya P: Effect of aggregation kinetics on the thermal conductivity of nanoscale colloidal solutions (nanofluid).

Nano Lett 2006, 6:1529. PubMed Abstract | Publisher Full Text

1. Gao JW, Zheng RT, Ohtani H, Zhu DS, Chen G: Experimental investigation of heat conduction mechanisms in nanofluids clue on clustering.

Nano Lett 2009, 9:4128. PubMed Abstract | Publisher Full Text

1. Eapen J, Rusconi R, Piazza R, Yip S: The classical nature of thermal conduction in nanofluids.

J Heat Transf 2009, 132:102402. Publisher Full Text

1. Xu YX, Bai H, Lu GW, Li C, Shi GQ: Flexible graphene films via the filtration of water-soluble noncovalent functionalized graphene sheets.

J Am Chem Soc 2008, 130:5856. PubMed Abstract | Publisher Full Text

1. Park C, Qunaies Z, Watson K, Crooks R, Smith J, Lowther S, Connell J, Siochi E, Harrison J, Clair T: Dispersion of single wall carbon nanotubes by in situ polymerization under sonication.

Chem Phys Lett 2002, 364:303. Publisher Full Text

1. Assael MJ, Metaxa IN, Arvanitidis J, Christofilos D, Lioutas C: Thermal conductivity enhancement in aqueous suspensions of carbon multi-walled and double-walled nanotubes in the presence of two different dispersants.

Int J Thermophys 2005, 26:647. Publisher Full Text

1. Ding Y, Alias H, Wen D, Williams RA: Heat transfer of aqueous suspensions of carbon nanotubes (CNT nanofluids).

Int J Heat Mass Transf 2005, 49:240. Publisher Full Text

1. Wen D, Ding Y: Experimental investigation into convective heat transfer of nanofluids at the entrance region under laminar flow conditions.

Int J Heat Mass Transf 2004, 47:5181. Publisher Full Text

1. Huxtable T, Cahill DG, Shenogin S, Xue LP, Ozisik R, Barone P, Usrey M, Strano MS, Siddons G, Shim M, Keblinski P: Interfacial heat flow in carbon nanotube suspensions.

Nat Mater 2003, 2:731. PubMed Abstract | Publisher Full Text

1. Chen LF, Xie HQ, Li Y, Yu W: Surface chemical modification of multiwalled carbon nanotubes by wet mechanochemical reaction.

J Nanomater 2008, 783981.

1. Yu W, Xie HQ, Chen LF, Li Y: Enhancement of thermal conductivity of kerosene-based magnetic nanofluids prepared via phase-transfer method.

Colloids Surf A 2010, 355:109. Publisher Full Text

1. Yu W, Xie HQ, Chen LF, Li Y, Zhang C: Synthesis and characterization of monodispersed copper colloids in polar solvents.

Nanoscale Res Lett 2009, 4:465. PubMed Abstract | Publisher Full Text |PubMed Central Full Text

1. Jang T, Xu K: FTIR study of ultradispersed diamond powder synthesized by explosive detonation.

Carbon 1995, 33:1663. Publisher Full Text

1. Liu MS, Lin MCC, Tsai CY, Wang CC: Enhancement of thermal conductivity with Cu for nanofluids using chemical reduction method.

Int J Heat Mass Transf 2006, 49:3028. Publisher Full Text

1. Das SJ, Putra N, Roetzel W: Pool boiling characteristics of nanofluids.

Int J Heat Mass Transf 2003, 46:851. Publisher Full Text

1. Hong KS, Hong TK, Yang HS: Thermal conductivity of Fe nanofluids depending on the cluster size of nanoparticles.

Appl Phys Lett 2006, 88:031901. Publisher Full Text

1. Xie HQ, Gu H, Fujii M, Zhang X: Short hot wire technique for measuring thermal conductivity and thermal diffusivity of various materials.

Meas Sci Technol 2006, 17:208. Publisher Full Text

1. Yu W, Xie H, Li Y, Chen L: Investigation of thermal conductivity and viscosity of ethylene glycol based ZnO nanofluid.

Thermochimica Acta 2009, 491:92. Publisher Full Text

1. Xie H, Yu W, Li Y, Chen L: MgO nanofluids: higher thermal conductivity and lower viscosity among ethylene glycol based nanofluids containing oxide nanoparticles.

J Exp Nanosci 2010, 5:463. Publisher Full Text

1. Yu W, Xie H, Li Y, Chen L: Experimental investigation on the thermal transport properties of ethylene glycol based nanofluids containing low volume concentration diamond nanoparticles.

Colloids Surf A

1. Yu W, Xie H, Bao D: Enhanced thermal conductivities of nanofluids containing graphene oxide nanosheets.

Nanotechnology 2010, 21:055705. PubMed Abstract | Publisher Full Text

1. Yu W, Xie H: Investigation on the thermal transport properties of ethylene glycol-based nanofluids containing copper nanoparticles.

Powder Technol 2010, 197:218. Publisher Full Text

1. Das SK, Putra N, Thiesen P, Roetzel W: Temperature dependence of thermal conductivity enhancement for nanofluids.

J Heat Transf 2003, 125:567. Publisher Full Text

1. Yang B, Han ZH: Thermal conductivity enhancement in water-in-FC72 nanoemulsion fluids.

Appl Phys Lett 2006, 89:083111. Publisher Full Text

1. Michael PB, Tongfan S, Amyn ST: The thermal conductivity of alumina nanoparticles dispersed in ethylene glycol.

Fluid Phase Equilibria 2007, 260:275. Publisher Full Text

1. Patel HE, Das SK, Sundararajan TA, Nair S, George B, Pradeep T: Thermal conductivity of naked and monolayer protected metal nanoparticles based nanofluids: manifestation of anomalous enhancement and chemical effects.

Appl Phys Lett 2003, 83:2931. Publisher Full Text

1. Chen LF, Xie HQ: Surfactant-free nanofluids containing double- and single-walled carbon nanotubes functionalized by a wet-mechanochemical reaction.

Thermochimica Acta 2010, 497:67-71. Publisher Full Text

1. Xie HQ, Li Y, Chen LF: Adjustable thermal conductivity in carbon nanotube nanofluids.

Phys Lett A 2009, 373:1861. Publisher Full Text

1. Nan C, Liu G, Lin Y, Li M: Interface effect on thermal conductivity of carbon nanotube composites.

Appl Phys Lett 2004, 85:3549. Publisher Full Text

1. Xue QZ: Model for the effective thermal conductivity of carbon nanotube composites.

Nanotechnology 2006, 17:1655. Publisher Full Text

1. Gao L, Zhou X, Ding Y: Effective thermal and electrical conductivity of carbon nanotube composites.

Chem Phys Lett 2007, 434:297. Publisher Full Text

1. Glory J, Bonetti M, Helezen M, Mayne-L’Hermite M, Reynaud C: Thermal and electrical conductivities of water-based nanofluids prepared with long multiwalled carbon nanotubes.

J Appl Phys 2008, 103:094309. Publisher Full Text

1. Ajayan PM, Terrones M, de la Guardia A, Huc V, Geobert N, Wei BQ, Lezec H, Ramanath G, Ebbesen TW: Nanotubes in a flash-ignition and reconstruction.

Science 2002, 296:705. PubMed Abstract | Publisher Full Text

1. Deng F, Zheng QS, Wang LF, Nan CW: Effects of anisotropy, aspect ratio, and nonstraightness of carbon nanotubes on thermal conductivity of carbon nanotube composites.

Appl Phys Lett 2007, 90:021914. Publisher Full Text

1. Sano M, Kamino A, Okamura J, Shinkai S: Ring closure of carbon nanotubes.

Science 2001, 293:1299. PubMed Abstract | Publisher Full Text

1. Russel WB, Saville DA, Schowwalter WR: Colloidal Suspensions. Cambridge, UK: Cambridge University Press; 1989.
2. Kim SH, Choi SR, Kim DS: Thermal conductivity of metal-oxide nanofluids: particle size dependence and effect of laser irradiation.

J Heat Transf 2007, 129:298. Publisher Full Text

1. Assael MJ, Chen CF, Metaxa I, Wakeham WA: Thermal conductivity of suspensions of carbon nanotubes in water.

Int J Thermophys 2004, 25:971. Publisher Full Text

1. Liu MS, Lin CC, Huang IT, Wang CC: Enhancement of thermal conductivity with carbon nanotube for nanofluids.

Int Commun Heat Mass Trans 2005, 32:1202-1210. Publisher Full Text

1. Chen QB, Wei YH, Shi YH, Liu HL, Hu Y: Measurement of surface tension and electrical conductivity of cationic gemini surfactants.

J East China Univ Sci Technol 2003, 29:33-37.

1. Zana R, Benrraou M, Rueff R: Alkanediyl-α, ω-bis (dimethylalkylammonium bromide) surfactants. 1. effect of the spacer chain length on the critical micelle concertration and micelle ionization degree.

Langmuir 1991, 7:1072-1075. Publisher Full Text

Huaqing Xie^*, Wei Yu, Yang Li and Lifei Chen

• *Corresponding author: Huaqing Xie hqxie@eed.sspu.cn

Author Affiliations

School of Urban Development and Environmental Engineering, Shanghai Second Polytechnic University, Shanghai 201209, China

For all author emails, please log on.

Nanoscale Research Letters 2011, 6:124 doi:10.1186/1556-276X-6-124

The electronic version of this article is the complete one and can be found online at:http://www.nanoscalereslett.com/content/6/1/124

 

Received:	3 September 2010
Accepted:	9 February 2011
Published:	9 February 2011

 

© 2011 Xie et al; licensee Springer.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Screening and evaluation of innate coagulants for water treatment: a sustainable approach – MyronLMeters.com

TweetAbstract Access to safe drinking water is important as a health and development issue at national, regional, and local levels. About one billion people do not have healthy drinking water. More than six million people (about two million children) die because of diarrhea which is caused by polluted water. Developing countries pay a high cost [...]

Abstract

Study of Physico-Chemical Characteristics of Wastewater in an Urban Agglomeration in Romania – MyronLMeters.com

TweetStudy of Physico-Chemical Characteristics of Wastewater in an Urban Agglomeration in Romania Abstract This study investigates the level of wastewater pollution by analyzing its chemical characteristics at five wastewater collectors. Samples are collected before they discharge into the Danube during a monitoring campaign of two weeks. Organic and inorganic compounds, heavy metals, and biogenic compounds [...]

Study of Physico-Chemical Characteristics of Wastewater in an Urban Agglomeration in Romania

Abstract

This study investigates the level of wastewater pollution by analyzing its chemical characteristics at five wastewater collectors. Samples are collected before they discharge into the Danube during a monitoring campaign of two weeks. Organic and inorganic compounds, heavy metals, and biogenic compounds have been analyzed using potentiometric and spectrophotometric methods. Experimental results show that the quality of wastewater varies from site to site and it greatly depends on the origin of the wastewater. Correlation analysis was used in order to identify possible relationships between concentrations of various analyzed parameters, which could be used in selecting the appropriate method for wastewater treatment to be implemented at wastewater plants.

Sources of wastewater in the selected area are microindustries (like laundries, hotels, hospitals, etc.), macroindustries (industrial wastewater) and household activities (domestic wastewater). Wastewater is collected through sewage systems (underground sewage pipes) to one or more centralized Sewage Treatment Plants (STPs), where, ideally, the sewage water is treated. However, in cities and towns with old sewage systems treatment stations sometimes simply do not exist or, if they exist, they might not be properly equipped for an efficient treatment. Even when all establishments are connected to the sewage system, the designed capacities are often exceeded, resulting in a less efficient sewage system and occasional leaks.

Studies of water quality in various effluents revealed that anthropogenic activities have an important negative impact on water quality in the downstream sections of the major rivers. This is a result of cumulative effects from upstream development but also from inadequate wastewater treatment facilities. Water quality decay, characterized by important modifications of chemical oxygen demand (COD), total suspended solids (TSSs), total nitrogen (TN), total phosphorous (TP), iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), lead (Pb), and so forth [11] are the result of wastewater discharge in rivers. Water-related environmental quality has been shown to be far from adequate due to unknown characteristics of wastewater . Thus an important element in preventing and controlling river pollution by an effective management of STP is the existence of reliable and accurate information about the concentrations of pollutants in wastewater. Studies of wastewater in Danube basins can be found, for instance, in central and eastern European countries, but we are not aware of extensive studies of wastewater quality at regional/national level in Romania.

This paper analyses the chemical composition of wastewater at several collectors/stations in an important Romanian city, Galati, before being discharged into natural receptors, which in this case are the Danube and Siret Rivers. No sewage treatment existed when the monitoring campaign took place, except the mechanical separation. The study presented here is part of a larger project aiming at establishing the best treatment technology of wastewater at each station. Presently this project is in the implementation stage at all stations. Possible relationships between concentrations of various chemical residues in wastewater and with pollution sources are also investigated. The study is based on daily measurements of chemical parameters at five city collectors in Galati, Romania, during a two-week campaign in February 2010.

2.1. Location of Sampling Sites

Galati-Braila area is the second urban agglomeration in Romania after Bucharest, which is located in Romania at the confluence of three major rivers: Danube, Siret, and Prut. The wastewater average flow is about 100000 m³/day . The drainage system covers an area of 2300 ha, serving approximately 99% of the population (approximately 300000 habitants). The basic drainage system is very old, dating back to the end of the 19th century, and was extended along with the expansion of the city due to demographic and industrial evolution. There are several collectors that collect wastewater and rainwater from various areas with very different characteristics, according to the existing water-pipe drainage system. There is no treatment at any station, except for simple mechanical separation. However, industrial wastewater is pretreated before being discharged in the city system. The five wastewater collectors are denoted in the following as S 1 , S 2 , … , S 5. Four of them discharge in the Danube River and the fifth discharges in the Siret River (which is an affluent of Danube River). Figure 1 shows the distribution of the monitoring sites and highlights the type of collecting area (domestic, industrial, or mixed). For the sake of brevity, these stations will be named in the present paper as “domestic,” “mixed,” and “industrial” stations, according to the type of collected wastewater. The mixture between domestic and industrial water at the two mixed collectors is the result of changes in city planning and various transformations of small/medium enterprises.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 1: Monitoring sampling sites of wastewater from Galati city.

Technical details about each collector/station can be found in Table 1. The first station, S1, collects 10% of the total quantity of wastewater. A high percentage of the water collected at this station comes from domestic sources from the south part of the city (more than 96%). Station S2 collects 64% of the total daily flow of wastewater, out of which 30% comes from domestic sources and the rest (70%) is industrial. Most of the industrial sources in this area are food-production units (milk, braid, wine) while the domestic sources include 20 schools, 4 hospitals, and important social objectives. Station S3 is located in the old part of the city and collects 5% of the total wastewater and has domestic sources. At the fourth station, S4, 11% of the quantity of wastewater is collected from domestic (70%) and industrial (30%) sources. The last collector, S5, collects wastewater from the industrial area of the city, where the most important objectives are a shipyard, metallurgical, and mechanical plants and transport stations.

Table 1: Characteristics of collectors S 1 , … , S 5.

2.2. Physico-Chemical Parameters and Methods of Analysis

The physico-chemical parameters which were measured are the following:(i)pH;(ii)chemical oxygen demand (COD) and dissolved oxygen (DO);(iii)nutrients such as nitrate (N-NO₃) and phosphate (P-PO₄) (these were included due to their impact on the eutrophication phenomenon);(iv)metals such as aluminum (Al⁺³), soluble iron (Fe⁺²), and cadmium (Cd⁺²).

The pH and DO were determined in situ using a portable multiparameter analyzer. Other chemical parameters such as COD, metals and nutrients were determined according to the standard analytical methods for the examination of water and wastewater .

The COD values reflect the organic and inorganic compounds oxidized by dichromate with the following exceptions: some heterocyclic compounds (e.g., pyridine), quaternary nitrogen compounds, and readily volatile hydrocarbons. The concentration of metals (Al⁺³, Cd⁺², Fe⁺²) was determined as a result of their toxicity.

The value of pH was analyzed according to the Romanian Standard using a portable multiparameter analyzer, Consort C932.

COD parameter was measured using COD Vials (COD 25–1500 mg/L, Merck, Germany). The digestion process of 3 mL aliquots was carried out in the COD Vials for 2 h at 148°C. The absorbance level of the digested samples was then measured with a spectrophotometer at λ = 605 nm (Spectroquant NOVA 60, Merck, Germany), the method being analogous to EPA methods [20], US Standard Methods, and Romanian Standard Methods.

The DO parameter was analyzed according to Romanian Standard using a portable multiparameter analyzer, Consort C932.

Aluminum ions (Al⁺³) were determined using Al Vials (Aluminum Test 0.020–1.20 mg/L, Merck, Germany) in a way analogous to US Standard Methods. The absorbance levels of the samples were then measured with a spectrophotometer (Spectroquant NOVA 60; Merck, Germany) at λ = 550 nm. The method was based on reaction between aluminum ions and Chromazurol S, in weakly acidic-acetate buffered solution, to form a blue-violet compound that is determined spectrophotometrically. The pH of the sample must be within range 3–10. Where necessary, the pH will be adjusted with sodium hydroxide solution or sulphuric acid.

Iron concentration (Fe⁺²) was determined using Iron Vials (Iron Test 0.005–5.00 mg/L, Merck, Germany) and their absorbance levels were then measured using a spectrophotometer (Spectroquant NOVA 60; Merck, Germany) at λ = 565 nm. The method was based on reducing all iron ions (Fe⁺³) to iron ions (Fe⁺²). In a thioglycolate-buffered medium, these react with a triazine derivative to form a red-violet complex which is spectrophotometrically determined. The pH must be within range 3–11. Where necessary the pH was adjusted with sodium hydroxide solution or sulphuric acid.

Cadmium ions (Cd⁺²) were determined using Cadmium Vials (Cadmium Test 0.005–5.00 mg/L, Merck, Germany), their absorbance levels being measured with a spectrophotometer (Spectroquant NOVA 60; Merck, Germany) at λ = 525 nm. The method was based on the reaction of cadmium ions with a cadion derivative (cadion-trivial name for 1-(4-nitrophenyl)-3-(4-phenylazophenyl)triazene), in alkaline solution, to form a red complex that is determined spectrophotometrically. The pH must be within the range 3–11, and, if not, the pH will be adjusted with sodium hydroxide solution or sulphuric acid.

Nitrogen content was determined using Nitrate Vials (Nitrate Cell test in seawater 0.10–3.00 mg/L NO₃-N or 0.4–13.3 mg/L N O3 −, Merck, Germany). The method being based on the reaction of nitrate ions with resorcinol, in the presence of chloride, in a strongly sulphuric acid solution, to form a red-violet indophenols dye that is determined spectrophotometrically. The absorbance levels of the samples were then measured with a spectrophotometer (Spectroquant NOVA 60; Merck, Germany) at λ = 500 nm.

Phosphorous content was determined using Phosphate Vials (Phosphate Cell Test 0.5–25.0 mg/L PO₄-P or 1.5–76.7 mg/L P O4 − 3, Merck, Germany) with a method that was analogous to the US Standard Methods [17]. The method was based on the reaction of orthophosphate anions, in a sulphuric solution, with ammonium vanadate and ammonium heptamolybdate to form orange-yellow molybdo-vanado-phosphoric acid that is determined spectrophotometrically (“VM” method). The absorbance levels of the samples were then measured with a spectrophotometer (Spectroquant NOVA 60; Merck, Germany) at λ = 410 nm.

All results were compared with standardized levels for wastewater quality found in accordance with European Commission Directive [23] and Romanian law [24].

3.1. The Acidity (pH)

The results for pH for all the investigated five collectors are shown in Figure 2.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 2: Daily variation of pH at all sites.

Generally, the wastewater collected at the monitored sites is slightly alkaline. The pH varies between 6.8 and 8.3—average value 7.82—thus the pH values are within the accepted range for Danube River according to the Romanian law, which is between 6.5 and 9.0. The pH variation is relatively similar at collectors S1–S4 (domestic and/or mixed domestic-industrial contribution). Lower pH values are observed at S5, which is dominated by industrial wastewater, originating from major enterprises and heavy industry. However, these values are not too low, since usually pH values for industrial wastewater are smaller than 6.5.

A significant decrease in the pH value was observed during the 8th day of the analyzed period at each station. Interestingly, a heavy snowfall took place at that particular time, thus the decrease could be attributed to the mixing between wastewater and a high quantity of low pH water, resulted from the melting of snow . One could speculate that the snowfall, which has an acidic character, might have affected the pH of the wastewater through “run off” phenomena.

No other snowfall took place during the monitoring campaign, thus no definite conclusion can be drawn for a possible relationship between pH and snowfalls.

3.2. Results for Chemical Oxygen Demand (COD)

Detection of COD values in each sampling site of wastewater is presented in Figure 3.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 3: Daily variation of COD at all sites.

All COD values are higher than the maximum accepted values (125 mg O₂/L) of the Romanian Law . Both organic and inorganic compounds have an effect on urban wastewater’s oxidability since COD represents not only oxidation of organic compounds, but also the oxidation of reductive inorganic compounds. That means some inorganic compounds interfere with COD determination through the consumption of C r2O7 − 2. Two different behaviors can be observed, which are associated with the type of the collected wastewater as follows.(i)The first group consists of stations S2, S4 and S5 where the wastewater has an important industrial component. At these stations, COD values are approximately between 150 and 300 mg O₂/L, smaller, for instance, than COD values found by in the raw wastewater produced by an industrial coffee plant where COD values were between 4000 and 4600 mg O₂/L. Also, the temporal variation of COD values at all three stations is similar with no significant deviations from the average value, which is about 250 mg O₂/L. Interestingly, the lowest COD level can be seen, on the average, at S5, which has the highest percentage of industrial wastewater. The second group comprises the “domestic” stations S1 and S3. The COD levels are higher, with values of 500 mg O₂/L or more. Also, the variability is clearly higher than at the industrial-type stations. No clear association between the variations at the two sites can be seen. A peak in COD was measured in the 14th day of the study at site S1 (1160 mg O₂/L). Since S1 is a domestic type station, it is unlikely that some major discharge led to such a high variation of COD. Unfortunately, no other information exists that might indicate a possible cause for this increase.

3.3. Results for Dissolved Oxygen (DO)

The amount of DO, which represents the concentration of chemical or biological compounds that can be oxidized and that might have pollution potential, can affect a sum of processes that include re-aeration, transport, photosynthesis, respiration, nitrification, and decay of organic matter. Low DO concentrations can lead to impaired fish development and maturation, increased fish mortality, and underwater habitat degradation . No standards are given by Romanian or European Law for DO in wastewater. The DO values for the analyzed wastewater at all five sites are shown in Figure 4.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 4: Daily variation of DO at all sites.

Concentration of DO varies at all sampling sites and has values between 0.96 (at S2) and 11.33 (at S4) mg O₂/L with a mean value of 6.39 mg O₂/L. These are clearly higher than DO values measured, for instance, in surface natural waters in China, where the Taihu watershed had the lowest DO level (2.70 mg/L), while in other rivers DO varied from 3.14 to 3.36 mg O₂/L [34]. On the other hand, such high values of DO (9.0 mg O₂/L) could be found, for instance, in the Santa Cruz River , who argued that discharging industry and domestic wastewater induced serious organic pollution in rivers, since the decrease of DO was mainly caused by the decomposition of organic compounds. Extremely low DO content (DO < 2 mg O₂/L) usually indicates the degradation of an aquatic system .

The DO levels vary similarly for all selected sampling sites. The DO levels cover a wide range, with a minimum value of 1.0 mg O₂/L at S1 and S3 and a maximum value of 11.33 mg O₂/L at S4. There is a drop in DO at all stations, observed is in the 8th day of the monitoring interval, which coincides with the day when a similar decrease in pH took place. The lowest values of DO are observed for S1, one of the two “domestic” stations. It is interesting to note that DO at S5 is low although the wastewater here comes only from industry sources.

3.4. Metals

The variation of Al⁺³, Fe⁺², and Cd⁺² concentrations in wastewater are shown in Figures 5, 6, and 7. Al⁺³ concentrations (Figure 5) were mostly within the 0.05–0.20 mg/L range at all the sampling sites. However, during the beginning and the end of the monitoring campaign, Al⁺³ concentration at station S2 is high (reaching even 0.65 mg/L), nonetheless below the limit imposed by the Romanian law, which is 5 mg/L . The fact that in the beginning of the time interval, the concentration of Al⁺³ is high at two neighboring stations (S1 and S2) suggests that some localized discharge affecting both runaway and waste water, might have happened in the southern part of the city, which led to the increase of Al⁺³concentration in the collected wastewater. This is supported by the fact that the concentration gradually decreases at S2.

 

Figure 5: Daily variation of Al at all sites.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 6: Daily variation of Fe at all sites.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 7: Daily variation of Cd at all sites.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The variation of Fe⁺² concentrations is shown in Figure 6. Fe⁺² concentration is within the 0.07–0.4 mg/L interval, below 5.0 mg/L, which is the maximum accepted value of the Romanian law . Two higher values were observed at S2 and S4 (both with industrial component) during the third and fourth days of the monitoring campaign.

Besides Al⁺³ and Fe⁺², concentrations of Cd⁺² were determined and the variations at the five stations are shown in Figure 7. Cd⁺² is a rare pollutant, originating from heavy industry. Leakages in the sewage systems can also lead to Cd⁺². Except for two days, Cd⁺² varies between 0.005 and 0.04 mg/L. The two high values of 0.11 mg/L were observed in the first and fourth days at S5, which collects industrial wastewater. However, Cd⁺² concentrations do not exceed the maximum accepted values of the Romanian law [24] for the monitoring interval which is 0.2 mg/L.

3.5. Nutrients

Water systems are very vulnerable to nitrate pollution sources like septic systems, animal waste, commercial fertilizers, and decaying organic matter [37]. Important quantities of nutrients, which are impossible to be removed naturally, can be found in rivers and this leads to the eutrophication of natural water (like Danube River). As a result, an increase in the lifetime of pathogenic microorganisms is expected. Measurement of nutrient (different forms of nitrogen (N) or phosphorous (P)) variations in domestic wastewater is strongly needed in order to maintain the water quality of receptors [36]. Nitrogen by nitrate (Figure 8) and phosphorous by phosphate (Figure 9) are considered as representative for nutrients.

Figure 8: Daily variation of N-NO₃ at all sites.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 9: Daily variation of P-PO₄ at all sites.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 8 shows that N-NO₃ concentrations vary, on the average, between 0 and 5.0 mg/L.

At all four stations with a domestic component, S1, S2, S3 and S4, the concentration of N-NO₃ is low (between 0 and 1.5 mg/L) and the daily variation is relatively similar at all sites. Noticeable drops of the N-NO₃ concentration are observed at all stations in the 8th day of the monitoring interval, coinciding with pH (Figure 2) and DO strong variations (Figure 4). This supports the conclusion that the heavy snowfall recorded at that period had an important impact on wastewater quality most likely due to the runoff joining the sewage system.

The behavior of N-NO₃ clearly differs at station S5, which collects only industrial wastewater. Significantly higher values of N-NO₃, ranging from 2.0 to 5.0 mg/L, were detected. However, the mean concentration of N-NO₃ remained below the maximum concentration given by the Romanian law [24]. Obviously, if treatment stations have to be set up, the priority for this particular nutrient component should concentrate on stations where industrial wastewater is collected.

Another nutrient that was analyzed for our study was orthophosphate expressed by phosphorous. The P-PO₄ concentration varies, on the average, between 1.0 and 6.0 mg/L (Figure 9). For this component, concentrations are higher at domestic stations, S1 and S3, than at the other three stations. P-PO₄ is expected to increase in domestic wastewater because of food, more precisely meat, processing, washing, and so forth. The lowest values were observed at S5, which has a negligible domestic component. Peaks in the P-PO₄ concentration are observed at S1. Interestingly enough, P-PO₄ temporal variations correlated pretty well at stations S2, S4, and S5 (which collect industrial wastewater). Unlike most of the other analyzed compounds, for which the concentrations were within the accepted ranges, the maximum level of P-PO₄ is exceeded at all five collectors. Both Romanian law  and the European law  stipulate 2.0 mg/L total phosphorous for 10000–100000 habitants, and for more than 100000 habitants (as in Galati City’s case) 1.0 mg/L total phosphorus. Interestingly, domestic stations seem to require more attention with respect to the quality of water then industrial stations.

Our results regarding the variation and levels of the analyzed parameters are grouped below as the following.(1)The values of pH are within the accepted range for Danube, and their daily variations are relatively similar for both domestic and mixed wastewater. Significantly smaller pH values were measured in the wastewater with a high industrial load. A clear minimum was observed at all sites in the 8th day of the monitoring period, when a heavy snowfall took place. One could speculate that the snowfall, which has an acidic character, might have affected the pH of the wastewater through “run off” phenomena. However, a clear connection cannot be established relying on one event only.(2)The COD level clearly depends on the type of wastewater. Higher values were observed for domestic wastewater, while “pure” industrial wastewater has the lowest COD. This might be explained by the fact that industrial wastewater benefits from some treatment before being discharged into the city sewage system. However, COD does exceed the maximum accepted values according to the Romanian law [24] at all sites thus additional treatment is required at all stations.(3)Concentrations of all analysed metals, Al⁺³, Cd⁺² and Fe⁺², are within the limit of the Romanian law. No association with the type of wastewater could be inferred. Isolated peaks could not be linked with any specific polluting factors, except for Cd⁺², for which accidental concentration increases are observed for pure industrial wastewater.(4)The level of P-PO₄, one of the two nutrients that were analyzed, was high at all stations; however, the highest concentrations are associated with domestic loads.(5)Opposingly, the N-NO₃ level is the highest, by far, in wastewater with a high industrial contribution.

3.6. Possible Relationships between Various Parameters

The experimental results have shown that some parameters might be related and that their behavior greatly depends on the type of collected wastewater. Differences between the behavior of physico-chemical parameters at the domestic sites (S1 and S3), on one hand, and at the other sites, on the other, was observed. Pearson correlation coefficients have been calculated between all parameters at all the selected five sites and corresponding significances. Although most of correlations were not significant, some interesting connections between various parameters at sites with similar characteristics were revealed. Table 2 shows correlation coefficients between various parameters for all five stations. Significant correlations at different types of stations are denoted as follows: italicized fonts for domestic stations, boldface italicized fonts for the industrial station and boldface fonts for mixed stations.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 2: Correlation coefficients calculated for station S1 to S5. Significant correlations at each type of stations are identified as follows: boldface italicized fonts for industrial station (S5), italicized fonts for domestic stations (S1 and S3) and boldface fonts for mixed stations (S2 and S4).

An important relationship seems to exist between pH and N-NO₃ at all stations except for the industrial wastewater collecting site, S5 (i.e., at all stations collecting wastewater resulting from domestic activities). Similarly, pH correlates well with DO at all stations except the industrial one.

COD correlates with two metals, Cd⁺² and soluble Fe⁺², which is expected [30], but only at S1 and S3, where the daily variations of the concentration for these two metals (Cd⁺² and soluble Fe⁺²) were similar.

No conclusion can be drawn for the industrial wastewater collector that was analyzed, where both positive and negative correlations were observed. The lack of correlation between the two metals and COD at the industrial wastewater collectors suggests that other processes, that alter the chemical equilibrium between the two chemical compounds, must be taken into account. For example some metals are complexed by organic compounds that are present in the water and the pH values can influence these phenomena.

DO correlates with pH and N-NO₃ at all four sampling stations with domestic component (S1–S4) but the relationship vanish at S5 (industrial). There is also a negative correlation between DO and Fe⁺² and Cd⁺² only for domestic wastewater, which is expected because of the natural oxidation of metals. The correlation vanishes at the other three stations which collect wastewater from industrial areas.

Heavy metals, Fe⁺² and Cd⁺² correlate only at domestic stations and no relationships can be defined to link the concentration of Al⁺³ with other components.

The P-PO₄ variation is linked to the variation of soluble Fe⁺² at the two stations that collect domestic wastewater. Interestingly, these two elements exist together in reductive domestic systems because these are dominated by proteins, lipids, degradation products. This relationship disappears at the other stations, where the industrial load is significant. The other metals, Al⁺³, seems to be linked with P-PO₄at stations S5 and S2, which collect wastewater with the highest industrial load. No link is observed for the rest of stations and for Cd⁺² which can be explained by a higher probability of iron (II) orthophosphate to form in wastewater compared to Al⁺³ or Cd⁺² orthophosphates.

Positive correlations can also be seen between P-PO₄ and COD for all sampling sites except S1, where the relationship is still positive but less significant. The other nutrient, N-NO₃, is anticorrelated with COD but only at S3 and is well correlated with pH and DO at all four stations with domestic component. The only exception is station S5, which collects mostly industrial wastewater.

Concluding, positive correlations were observed between the following parameters.(1)pH and N-NO₃ everywhere except “purely” industrial water.(2)COD and soluble Fe⁺² at domestic stations.(3)DO and pH, on the one hand, and DO and N-NO₃ at domestic stations.(4)P-PO₄ and soluble Fe⁺² at domestic stations.(5)P-PO₄ and COD everywhere, which, taking into account the high level of P-PO₄ at domestic stations, might suggest that one important contributor to water quality degradation are household discharges.(6)Al⁺³ and P-PO₄.

In the present paper we have analyzed the daily variation of several physico-chemical parameters of the wastewater (pH, COD, DO, Al⁺³, Fe⁺², Cd⁺², N-NO₃, and P-PO₄) at five collectors that have been characterized as domestic, industrial and mixed, according to the type of collecting area. Different results have been obtained for domestic and industrial wastewater. Most of the chemical parameters are within accepted ranges. Nevertheless, their values as well as their behavior depend significantly on the type of collected wastewater.

The overall conclusion is that wastewater with a high domestic load has the highest negative impact on water quality in a river. On the other hand, industrial wastewater brings an important nutrient load, with potentially negative effect on the basins where it is discharged. Our results suggested that meteorological factors (snow) might modify some characteristics of wastewater, but a clear connection cannot be established relying on one event only.

Significantly smaller pH values were measured in the wastewater with a high industrial load. The COD level clearly depends on the type of wastewater. Higher values were observed for wastewater with domestic sources, while “pure” industrial wastewater has the lowest COD. This might be explained by the fact that industrial wastewater benefits from some treatment before being discharged into the city sewage system. COD does exceed the maximum accepted values according to the Romanian law at all sites thus additional treatment is required at all stations. Accidental increases of Cd⁺² concentrations are observed for pure industrial wastewater. The highest concentrations of P-PO₄ are associated with domestic loads. Opposing, the N-NO₃ level is clearly the highest in wastewater with a high industrial contribution.

Correlation analysis has been used in order to identify possible relationships between various parameters for wastewater of similar origin.

Positive correlations between various physico-chemical parameters exist for the domestic wastewater (DO, pH and N-NO₃, on the one hand, and P-PO_4, COD and soluble Fe⁺², on the other hand). Except for two cases, these relationships break when the industrial load is high. Some of the existing correlations are expected as discussed above, thus any removal treatment should be differentiated according to the type of collector, before discharging it into the natural receptors in order to be costly efficient. Correlations between DO and COD and nutrient load suggest that the most important threat for natural basins in the studied area, are domestic sources for the wastewater.

The different percentages of industrial and domestic collected wastewater vary at each station, which has a clear impact on concentrations of the selected chemical components. Our results show that domestic wastewater has a higher negative impact on water quality than wastewater with a high industrial load, which, surprisingly, seems to be cleaner. This might be related to the fact that most industries are forced, by law, to apply a pretreatment before discharging wastewater into the city sewage system. Industrial wastewater affects the nutrient content of natural water basins. Although the time period was relatively short, our study identified specific requirements of chemical treatment at each station. An efficient treatment plan should take into account the type of wastewater to be processed at each station. Results presented here are linked with another research topic assessing the level of water quality in the lower basin of the Danube before and after implementing the complete biochemical treatment plants.

The work of Catalin Trif was supported by Project SOP HRD-EFICIENT 61445/2009.

Copyright © 2012 Paula Popa et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited – original found here: http://www.hindawi.com/journals/tswj/2012/549028/

 

 

Application Bulletin: POOL & SPA Water – MyronLMeters.com

Tweet                 Anyone responsible for operating and maintaining a swimming pool or spa has to test, monitor, and control complex, interdependent chemical factors that affect the quality of water. Additionally, aquatic facilities operators must be familiar with all laws, regulations, and guidelines governing what these parameters should be. [...]

SALTWATER SANITATION

A relatively new development, saltwater pools use regular salt, sodium chloride, to form chlorine with an electrical current much in the same way liquid bleach is made. As chlorine – the sanitizer – is made from the salt in the water, it is critical to maintain the salt concentration at the appropriate levels to produce an adequate level of sanitizer. It is even more important to test water parameters frequently in these types of pools and spas, as saltwater does not have the ability to respond adequately to shock loadings (superchlorination treatments).

Most saltwater chlorinators require a 2,500 – 3,000 ppm salt concentration in the water (though some may require as high as 5,000-7,000 ppm).* This can barely be tasted, but provides enough salt for the system to produce the chlorine needed to sanitize the water.

(It is important to have a good stabilizer level – 30 – 50 ppm* – in the pool, or the sunlight will burn up the chlorine. Without it, the saltwater system may not be able to keep up with the demand regardless of salt concentration.)

Taste and salt shortages are of little concern to seawater systems that maintain an average of 32,000 ppm. In these high-salt environments, you need to beware of corrosion to system components that can distort salt level and other parameter readings.

Additionally, incorrect salt concentration readings can occur in any saltwater system. The monitoring/controlling components can and do fail or become scaled— sometimes giving a false low salt reading. Thus, you must test manually for salt concentration with separate instrumentation before adding salt.

You must also test salt concentration manually with separate instrumentation to re-calibrate your system. This is critical to system functioning and production of required chlorine. Both the PoolPro and PT1 conveniently test for salt concentration at the press of a button as a check against automatic controller systems that may have disabled equipment or need to be re-calibrated.

Though no one instrument or method can be used to determine ALL of the factors that affect the comfort and sanitation of pool and spa water, PoolPro is a comprehensive water testing instrument that is reliable durable, easy-to-use and easy-to-maintain and calibrate. As a pool professional, a PoolPro will not only simplify your life, it will save you time and money.

 RECORD KEEPING – WHAT TO DO WITH ALL THOSE MEASUREMENTS …

Data handling should be done objectively, and data recorded in a common format in the most accurate way. Also, data should be stored in more than one permanent location and made available for future analysis. Most municipalities require commercial aquatic facilities to keep permanent records on site and available for inspection at any time.

PoolPro makes it easy to comply with record keeping requirements. The PoolPro is an objective means to test free chlorine, ORP, pH, TDS, temperature and the mineral/salt content of any pool or spa. You just rinse and fill the cell cup by submerging the waterproof unit and press the button of the parameter you wish to measure. You immediately get a standard, numerical digital readout –  no interpretation required – eliminating all subjectivity. And model PS9TK features the added ability to perform in-cell conductometric titrations for Alkalinity, Hardness and LSI on the spot. Up to 100 date-time-stamped readings can be stored in memory and then later transferred directly to a computer wirelessly using the bluDock™ accessory package. Simply pair the bluDock with your computer, then open the U2CI software application to download data. The user never touches the data, reducing the potential for human error in transcription. The data can then be imported into any program necessary for record-keeping and analysis. The bluDock is a quick and easy way to keep records that comply with governing standards.*

*Consult your governing bodies for specific testing, chemical concentrations, and all other guidelines and requirements. The ranges and methods suggested here are meant as general examples.

Save 10% when you order online here at MyronLMeters.com.

Frequently Asked Questions – MyronLMeters.com

TweetHow long will my Standard Solutions and Buffers last? The warranty on all standards and buffers is one year from the date it is manufactured (see the label on the bottle). If the standards and buffers become contaminated by the user pouring test samples back into the bottle or inserting the probe into the bottle [...]

How long will my Standard Solutions and Buffers last?

The warranty on all standards and buffers is one year from the date it is manufactured (see the label on the bottle). If the standards and buffers become contaminated by the user pouring test samples back into the bottle or inserting the probe into the bottle the solution will not be accurate and should be discarded. The life of standards and buffers can exceed 1 year if the bottle is stored tightly capped and is not exposed to direct sunlight or freezing temperatures. If the solution becomes frozen, do not remove the cap – allow the standard or buffer solution to thaw completely and shake the bottle vigorously before opening.

How do I clean the conductivity cell cup on the handheld units?

With everyday sampling, the cell cup may build up a residue or film on the cell walls that may cause the readings to become erratic. Use a 50/50 mixture of a common household cleaner (i.e. Lime-A-Way, CLR, Tilex, etc) and DI water. Pour into conductivity cell cup and scrub with a q-tip. Be sure to get around all the electrodes and the thermistor probe. On the DS handheld unit, use an acid brush to scrub the cell cup. Let it set for about 10 minutes. Rinse the cell cup thoroughly with tap water, then a final rinse with DI water.

The display on my Ultrameter II 6P reads “Error 1″. What does that mean?

This is possibly caused by contamination to the circuit board. One or more of the traces on the PCB have been jumped/bridged and there is a contamination. Possible moisture, condensation, dirt, dried salts or other condensation inside is a potential cause for this display.

Where can I get an operations manual for my meter?

Go to MyronLMeters.com. Click on Manuals and Literature at the top of the page. Once on the Manuals and Literature page, you’ll find application bulletins, operations manuals, material safety data sheets, and product datasheets.  All are free, downloadable pdf files.

How do I pick the correct range module for my Monitor or Monitor/Controller?

Pick a range module that covers 2/3 of your operating range. If you pick a range module that is too broad, then your accuracy will suffer or it will not show a number on the display. For example, if your operating range is 100-150 microsiemens, a range module of 0-200 microsiemens (-115) would be a good choice. A range module of 0- 5,000 microsiemens (-123) would not be a good choice for this application

Got questions? Visit us at MyronLMeters.com and Ask An Expert.

 

 

 

 

Coming in 2013: The Myron L PoolPro PS9TK – MyronLMeters.com

Tweet                            For Pool Professionals The PoolPro is a comprehensive high performance tool designed to simplify pool and spa water quality control for the pool professional. Both PoolPro models – the PS6 and the PS9TK feature innovative user-friendly features and functions that make [...]

 

 

 

 

 

 

 

 

 

 

 

 

 

 

For Pool Professionals

The PoolPro is a comprehensive high performance tool designed to simplify pool and spa water quality control for the pool professional. Both PoolPro models – the PS6 and the PS9TK feature innovative user-friendly features and functions that make it easy to manage parameters critical to disinfection, water balance, system maintenance and compliance.

New! Fce FAC Readings

FCE function reports FAC quickly and accurately by measuring ORP, the chemical characteristic of chlorine that directly reflects its effectiveness, cross referenced with pH. Both DPD kits and colorimeters may tell the user the FAC value of the sample in the test tube, but since the chemistry of that sample is quite different from the source water being analyzed, the results are imprecisely related to actual disinfection power.

FCE function measures the real, unaltered chemistry of source water, including moment-to-moment changes in that chemistry.

FCE can be used for other types of oxidizing germicides and will track the effect of additives, such as cyanuric acid, that degrade chlorine effectively without changing the actual concentration of free available chlorine present.

In-Cell Titration Functions

The PS9TK adds the ability to perform in-cell conductometric titrations that provides a convenient way to determine alkalinity, hardness and LSI in the field. This eliminates the need to collect and transport samples to another location for analysis. User intuitive display prompts guide you through titration procedures from start to finish. All required reagents and equipment are included in the PS9 titration kit.

Water Balance Analysis

The PS9TK features both an LSI Calculator and an LSI Titration measurement mode. The Calculator allows you to perform what-if scenarios to predict how changes in solution parameters would affect the water balance of a system. The titration measurement function allows you to accurately calculate a saturation index value of a specific solution to determine whether the solution is balanced, scaling or corrosive.

Hardness Unit Conversion The Hardness and LSI Titrations and LSI Calculator functions allow you to set the hardness unit preference to either grains of hardness or ppm CaCO3 according to your needs.

System Validation & Calibration

The PoolPro provides a fast, precise, easy-to-use method of obtaining Oxidation Reduction Potential (ORP or REDOX) mV readings to check the true level of effectiveness of ALL sanitizers in any pool or spa. ORP objectively and precisely measures sanitizer ability to burn up, or oxidize, organic matter in the water. ORP can only be determined by an electronic instrument.

PoolPro ORP mV readings serve as a necessary check to ensure automatic ORP control systems are working properly. PoolPro also provides independent readings for recalibration and to detect system failure.

Saltwater Chlorine Generation

PoolPro provides a convenient one-touch test for Mineral/Salt concentration. This is ideal for saltwater systems where manual testing with separate instrumentation is necessary to ensure the proper amount of sodium chloride is present for chlorine generation in quantities specified for microbial disinfection. PoolPro can also be used to recalibrate equipment as part of regular maintenance.

Wireless Benefits

The optional bluDock™ accessory package is an integrated data solution for your record keeping requirements, eliminating the need for additional hardware, wires and hassle. Because the user never touches the data, there is little opportunity for data tampering and human error. bluDock software has an easy to use interface with user intuitive functions for storing, sorting and exporting data.

Simply the Best

PoolPro is lightweight, portable, buoyant, waterproof, easy-to-calibrate, and easy-to-use. Simply rinse and fill the cell cup by dipping the PoolPro in the water, then press the button of the parameter you wish to measure. You immediately get a standard, numerical digital readout — eliminating all subjectivity. And you can store up to 100 date-time-stamped readings in PoolPro’s non-volatile memory.

Watch for the product launch later this year.

 

Recent Papers in Water Treatment for Small/Decentralized Systems – MyronLMeters.com

TweetRecent Papers in Water Treatment for Small/Decentralized Systems Content Table Recent Papers in Water Treatment for Small/Decentralized Systems  Turbidity and chlorine demand reduction using locally available physical water clarification mechanisms before household chlorination in developing countries Appropriate wastewater treatment systems for developing countries: criteria and indictor assessment in Thailand A new paradigm for low-cost urban [...]

Recent Papers in Water Treatment for Small/Decentralized Systems

Content Table

• Recent Papers in Water Treatment for Small/Decentralized Systems 
  • Turbidity and chlorine demand reduction using locally available physical water clarification mechanisms before household chlorination in developing countries
  • Appropriate wastewater treatment systems for developing countries: criteria and indictor assessment in Thailand
  • A new paradigm for low-cost urban water supplies and sanitation in developing countries
  • Faecal bacterial indicators removal in various wastewater treatment plants located in Almendares River watershed (Cuba)
  • Treatment of low and medium strength sewage in a lab-scale gradual concentric chambers (GCC) reactor
  • Use of modelling for optimization and upgrade of a tropical wastewater treatment plant in a developing country
  • Ceramic silver-impregnated pot filters for household drinking water treatment in developing countries: material characterization and performance study
  • Ceramic membranes for direct river water treatment applying coagulation and microfiltration
  • Related Publications

Turbidity and chlorine demand reduction using locally available physical water clarification mechanisms before household chlorination in developing countries

Journal of Water and Health Vol 07 No 3 pp 497–506 © IWA Publishing 2009 doi:10.2166/wh.2009.071

Link to Summary Page

Nadine Kotlarz, Daniele Lantagne, Kelsey Preston and Kristen Jellison

Department of Civil and Environmental Engineering, Lehigh University, 13 East Packer Avenue, Bethlehem, PA 18015, USA
Enteric Diseases Epidemiology Branch, US Centers for Disease Control and Prevention, 1600 Clifton Road, MS-A38, Atlanta, GA 30333, USA Tel.:             +1 404 639 0231       Fax: +1 404 639 2205 E-mail: dlantagne@cdc.gov

Abstract

Over 1.1 billion people in the world lack access to improved drinking water. Diarrhoeal and other waterborne diseases cause an estimated 1.9 million deaths per year. The Safe Water System (SWS) is a proven household water treatment intervention that reduces diarrhoeal disease incidence among users in developing countries. Turbid waters pose a particular challenge to implementation of SWS programmes; although research shows that a 3.75 mg l^-1 sodium hypochlorite dose effectively treats turbid waters, users sometimes object to the strong chlorine taste and prefer to drink water that is more aesthetically pleasing. This study investigated the efficacy of three locally available water clarification mechanisms—cloth filtration, settling/decanting and sand filtration—to reduce turbidity and chlorine demand at turbidities of 10, 30, 70, 100 and 300 NTU. All three mechanisms reduced turbidity (cloth filtration -1–60%, settling/decanting 78–88% and sand filtration 57–99%). Sand filtration (P=0.002) and settling/decanting (P=0.004), but not cloth filtration (P=0.30), were effective at reducing chlorine demand compared with controls. Recommendations for implementing organizations based on these results are discussed.

Appropriate wastewater treatment systems for developing countries: criteria and indictor assessment in Thailand

Water Science & Technology—WST Vol 59 No 9 pp 1873–1884 © IWA Publishing 2009 doi:10.2166/wst.2009.215

Link to Summary Page

W. Singhirunnusorn and M. K. Stenstrom

Faculty of Environment and Resource Studies, Mahasarakham University, Kantharawichai District, Maha Sarakham Province 44150, Thailand E-mail: swichitra@gmail.com
Department of Civil and Environmental Engineering, UCLA, Los Angeles CA 90095, USA E-mail: stenstro@seas.ucla.edu

Abstract

This paper presents a comprehensive approach with factors to select appropriate wastewater treatment systems in developing countries in general and Thailand in particular. Instead of focusing merely on the technical dimensions, the study integrates the social, economic, and environmental concerns to develop a set of criteria and indicators (C&I) useful for evaluating appropriate system alternatives. The paper identifies seven elements crucial for technical selection: reliability, simplicity, efficiency, land requirement, affordability, social acceptability, and sustainability. Variables are organized into three hierarchical elements, namely: principles, criteria, and indicators. The study utilizes a mail survey to obtain information from Thai experts—academicians, practitioners, and government officials—to evaluate the C&I list. Responses were received from 33 experts on two multi-criteria analysis inquiries—ranking and rating—to obtain evaluative judgments. Results show that reliability, affordability, and efficiency are among the most important elements, followed by sustainability and social acceptability. Land requirement and simplicity are low in priority with relatively inferior weighting. A number of criteria are then developed to match the contextual environment of each particular condition. A total of 14 criteria are identified which comprised 64 indicators. Unimportant criteria and indicators are discarded after careful consideration, since some of the indicators are local or site specific.

A new paradigm for low-cost urban water supplies and sanitation in developing countries

Water Policy Vol 10 No 2 pp 119–129 © IWA Publishing 2008 doi:10.2166/wp.2008.034

Link to Summary Page

Duncan Mara^a and Graham Alabaster^b

^aCorresponding author. School of Civil Engineering, University of Leeds, Leeds LS2 9JT UK. Fax: +44-113-343-2243 E-mail: d.d.mara@leeds.ac.uk
^bUnited Nations Human Settlements Programme, PO Box 30300, Nairobi, Kenya

Abstract

To achieve the Millennium Development Goals for urban water supply and sanitation ~300,000 and ~400,000 people will have to be provided with an adequate water supply and adequate sanitation, respectively, every day during 2001–2015. The provision of urban water supply and sanitation services for these numbers of people necessitates action not only on an unprecedented scale, but also in a radically new way as “more of the same” is unlikely to achieve these goals. A “new paradigm” is proposed for low-cost urban water supply and sanitation, as follows: water supply and sanitation provision in urban areas and large villages should be to groups of households, not to individual households. Groups of households would form (even be required to form, or pay more if they do not) water and sanitation cooperatives. There would be standpipe and yard-tap cooperatives served by community-managed sanitation blocks, on-site sanitation systems or condominial sewerage, depending on space availability and costs and, for non-poor households, in-house multiple-tap cooperatives served by condominial sewerage or, in low-density areas, by septic tanks with on-site effluent disposal. Very poor households (those unable to afford to form standpipe cooperatives) would be served by community-managed standpipes and sanitation blocks.

Faecal bacterial indicators removal in various wastewater treatment plants located in Almendares River watershed (Cuba)

Water Science & Technology—WST Vol 58 No 4 pp 773–779 © IWA Publishing 2008 doi:10.2166/wst.2008.440

Link to Summary Page

Tamara Garcia-Armisen, Josué Prats, Yociel Marrero and Pierre Servais

Ecologie des Systèmes Aquatiques, Université Libre de Bruxelles, Brussels, Belgium *Present address: MINT, Vrije Universiteit Brussel, Building E, Pleinlaan 2, 1050, Brussels, Belgium Tel.:            +3226291918       E-mail: tgarciaa@vub.ac.be
Dpto. de Microbiología, Facultad de Biología, Universidad de La Habana, La Habana, Cuba
Instituto Superior Politécnico José Antonio Echeverría, La Habana, Cuba

Abstract

The Almendares River, located in Havana city, receives the wastewaters of more than 200,000 inhabitants. The high abundance of faecal bacterial indicators (FBIs) in the downstream stretch of the river reflects the very poor microbiological water quality. In this zone, the Almendares water is used for irrigation of urban agriculture and recreational activities although the microbiological standards for these uses are not met. Improvement of wastewater treatment is absolutely required to protect the population against health risk. This paper compares the removal of FBIs in three wastewater treatment plants (WWTPs) located in this watershed: a conventional facility using trickling filters, a constructed wetland (CW) and a solar aquatic system (SAS). The results indicate better removal efficiency in the two natural systems (CW and SAS) for all the measured parameters (suspended matters, biological oxygen demand, total coliforms, E. coli and enterococci). Removals of the FBIs were around two log units higher in both natural systems than in the conventional one. A longitudinal profile of the microbiological quality of the river illustrates the negative impact of the large conventional WWTP. This case study confirms the usefulness of small and natural WWTPs for tropical developing countries, even in urban and periurban areas.

Treatment of low and medium strength sewage in a lab-scale gradual concentric chambers (GCC) reactor

Water Science & Technology—WST Vol 57 No 8 pp 1155–1160 © IWA Publishing 2008 doi:10.2166/wst.2008.093

Link to Summary Page

L. Mendoza, M. Carballa, L. Zhang and W. Verstraete

Experimental Reproduction Centre (CEYSA), Agricultural Faculty, Technical University of Cotopaxi, Latacunga, Ecuador E-mail: lauramen_2000@yahoo.com
Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, Coupure Links 653, B-9000, Ghent, Belgium E-mail: willy.verstraete@ugent.be; marta.carballa@ugent.be; lezhanghua@hotmail.com

Abstract

One of the major challenges of anaerobic technology is its applicability for low strength wastewaters, such as sewage. The lab-scale design and performance of a novel Gradual Concentric Chambers (GCC) reactor treating low (165±24 mg COD/L) and medium strength (550 mg COD/L) domestic wastewaters were studied. Experimental data were collected to evaluate the influence of chemical oxygen demand (COD) concentrations in the influent and the hydraulic retention time (HRT) on the performance of the GCC reactor. Two reactors (R₁ and R₂), integrating anaerobic and aerobic processes, were studied at ambient (26°C) and mesophilic (35°C) temperature, respectively. The highest COD removal efficiency (94%) was obtained when treating medium strength wastewater at an organic loading rate (OLR) of 1.9 g COD/L·d (HRT = 4 h). The COD levels in the final effluent were around 36 mg/L. For the low strength domestic wastewater, a highest removal efficiency of 85% was observed, producing a final effluent with 22 mg COD/L. Changes in the nutrient concentration levels were followed for both reactors.

Use of modelling for optimization and upgrade of a tropical wastewater treatment plant in a developing country

Water Science & Technology Vol 56 No 7 pp 21–31 © IWA Publishing 2007 doi:10.2166/wst.2007.675

Link to Summary Page

D. Brdjanovic^*, M. Mithaiwala^**, M.S. Moussa^***, G. Amy^* and M.C.M. van Loosdrecht^****

*Department of Urban Water and Sanitation, UNESCO-IHE Institute for Water Education, Westvest 7, PO Box 3015, 2061 DA , Delft, The Netherlands (E-mail: d.brjanovic@unesco-ihe.org)
**Drainage Department, Surat Municipal Corporation, Muglisara, Surat , Gujarat, 395003, India (Email: mayank_heena6143@yahoo.com)
***Civil Engineering Department, Faculty of Engineering Mataria, Helwan , University, Egypt (Email: m.moussa@delft-environment.com)
****Department of Biochemical Engineering, Delft University of Technology, Julianalaan 67, 2628 BC , Delft, The Netherlands (Email: m.c.m.vanloosdrecht@tudelft.nl)

Abstract

This paper presents results of a novel application of coupling the Activated Sludge Model No. 3 (ASM3) and the Anaerobic Digestion Model No.1 (ADM1) to assess a tropical wastewater treatment plant in a developing country (Surat, India). In general, the coupled model was very capable of predicting current plant operation. The model proved to be a useful tool in investigating various scenarios for optimising treatment performance under present conditions and examination of upgrade options to meet stricter and upcoming effluent discharge criteria regarding N removal. It appears that use of plant-wide modelling of wastewater treatment plants is a promising approach towards addressing often complex interactions within the plant itself. It can also create an enabling environment for the implementations of the novel side processes for treatment of nutrient-rich, side-streams (reject water) from sludge treatment.

Ceramic silver-impregnated pot filters for household drinking water treatment in developing countries: material characterization and performance study

Water Science & Technology: Water Supply Vol 7 No 5-6 pp 9–17 © IWA Publishing 2007 doi:10.2166/ws.2007.142

Link to Summary Page

D. van Halem^*, S.G.J. Heijman^*, A.I.A. Soppe^**, J.C. van Dijk^* and G.L. Amy^***

*Delft University of Technology, Stevinweg 1, 2628 CN , Delft, The Netherlands (E-mail: d.vanhalem@tudelft.nl; j.c.vandijk@tudelft.nl)
**Delft University of Technology & Kiwa Water Research, Groningenhaven 7, 3433 PE , Nieuwegein, The Netherlands (E-mail: s.g.j.heijman@tudelft.nl)
***Aqua for All Foundation, Groningenhaven 7, 3433 PE , Nieuwegein, The Netherlands (E-mail: gsoppe@planet.nl)
****UNESCO-IHE Institute for Water Education, Westvest 7, 2611 AX , Delft, The Netherlands (E-mail: g.amy@unesco-ihe.org)

Abstract

The ceramic silver-impregnated pot filter (CSF) is a low-cost drinking water treatment system currently produced in many factories worldwide. The objective of this study is to gather performance data to provide a scientific basis for organisations to safely scale-up and implement the CSF technology. Filters from three production locations are included in this study: Cambodia, Ghana and Nicaragua. The microstructure of the filter material was studied using mercury intrusion porosimetry and bubble-point tests. Effective pores were measured with a mean of 40 mm, which is larger than many pathogenic microorganisms. The removal efficiency of these microorganisms was measured by using indicator organisms; total coliforms naturally present in canal water, sulphite reducing Clostridium spores, E.coli K12 and MS2 bacteriophages. The removal of these organisms was monitored during a long-term study of several months in the laboratory. Ceramic silver impregnated pot filters successfully removed total coliforms and sulphite reducing Clostridium spores. High concentrations of Escherichia coli K12 were also removed, with log(10) reduction values consistently higher than 2. MS2 bacteriophages were only partially removed from the water, with significantly better results for filters without an impregnation of colloidal silver. During this study the main deficiency of the filter system proved to be the low water production; after 12 weeks of use all filter discharges were below 0.5 Lh^-1, which is insufficient to provide drinking water for a family

Ceramic membranes for direct river water treatment applying coagulation and microfiltration

Water Science & Technology: Water Supply Vol 6 No 4 pp 89–98 © IWA Publishing 2006 doi:10.2166/ws.2006.906

Link to Summary Page

A. Loi-Brügger^*, S. Panglisch^*, P. Buchta^*, K. Hattori^**, H. Yonekawa^**, Y. Tomita^** and R. Gimbel^*,***

*IWW Water Center, Moritzstr. 26, 45476 Mülheim, , Germany (E-mail: a.loi@iww-online.de)
**NGK Insulators Ltd., 2-56 Suda-cho, Nagoya, Aichi, , 467-8530, Japan (E-mail: kohji-h@ngk.co.jp)
***Institut für Energie- und Umweltverfahrenstechnik, Universität Duisburg-Essen Bismarckstr. 90, 47057 Duisburg, , Germany (E-mail: gimbel@uni-duisburg.de)

Abstract

A new ceramic membrane has been designed by NGK Insulators Ltd., Japan, to compete in the drinking water treatment market. The IWW Water Centre, Germany, investigated the operational performance and economical feasibility of this ceramic membrane in a one year pilot study of direct river water treatment with the hybrid process of coagulation and microfiltration. The aim of this study was to investigate flux, recovery, and DOC retention performance and to determine optimum operating conditions of NGK’s ceramic membrane filtration system with special regards to economical aspects. Temporarily, the performance of the ceramic membrane was challenged under adverse conditions. During pilot plant operation river water with turbidities between 3 and 100 FNU was treated. Membrane flux was increased stepwise from 80–300 l/m²h resulting in recoveries between 95.9 and 98.9%. A DOC removal between about 20–35% was achieved. The pilot study and the subsequent economical evaluation showed the potential to provide a reliable and cost competitive process option for water treatment. The robustness of the ceramic membrane filtration process makes it attractive for a broad range of water treatment applications and, due to low maintenance requirements, also suitable for drinking water treatment in developing countries.

Related Publications

Public Private Partnerships in the Water Sector - Cledan Mandri-Perrott and David Stiggers
Publication Date: Mar 2013 – ISBN – 9781843393207

Designing Wastewater Systems According to Local Conditions - David M Robbins
Publication Date: Jan 2014 – ISBN – 9781780404769

Water Services Management and Governance - Tapio Katko, Petri S. Juuti, and Klaas Schwartz
Publication Date: Oct 2012 – ISBN – 9781780400228