Tweet In water remote sensing, or ‘ocean color‘, people extract water quality parameters from satellite imagery. Probably the most interesting parameter is chlorophyll-a concentration, which can be related to the phytoplankton (algae, cyanobacteria) biomass in the water. Applications are quite diverse, ranging from harmful algal […]
In water remote sensing, or ‘ocean color‘, people extract water quality parameters from satellite imagery. Probably the most interesting parameter is chlorophyll-a concentration, which can be related to the phytoplankton (algae, cyanobacteria) biomass in the water. Applications are quite diverse, ranging from harmful algal blooms early warning systems, eutrophication assessment to climate change research – to name a few.
The same algorithms are used on spectra taken directly in the field to calibrate/validate remotely sensed concentrations. However, spectrometers used for these field measurements are quite expensive (>20k USD) and often not trivial to operate. This hampers the use of ‘water color’ by a wider audience, e.g. water managers, fisheries and especially the public that might want to know what the water quality in their pond is.
Spectra from cheap, open source spectrometers can potentially bridge this gap.
From my experience with the foldable spectrometer and the desktop kit I see three main issues: sensitivity, spectral resolution and calibration.
- Sensitivity Water appears often very dark, especially if only little scattering substance is present. In contrast, the reflection of the direct sun light on the water surface is extremely bright. Thus, to resolve the ‘true’ water color, the instrument has to be relatively sensitive.
- Spectral Calibration and Calibration Pigment absorption, other optically active substances and the water itself cause the water’s color. Pigments in phytoplankton, such as the main photosynthetic pigment chlorophyll-a, have very sharp absorption features. In order to resolve those peaks, the spectral resolution has has to be sufficiently high and the calibration sufficiently accurate.
These days I had the opportunity to take the desktop kit out on a fieldwork campaign on Lake Peipsi and Lake Vortsjarv in Estonia. Fortunately, this little Baltic country has one of the best 3G-networks worldwide and so I could use the spectral workbench to upload my spectra straight from the boats – pretty cool! However, an offline version of the workbench is essential (couldn’t get the local webserver running so far). The spectra are available here: Lake Peipsi (R_sky, R_water), Lake Vortsjarv (R_sky, R_water).
- Preparations / Calibration The initial wavelength calibration with fluorescent light line peaks is pretty brilliant. Still, at least a rudimentary intensity calibration is necessary to interpret the shape of the spectra. I can use our calibration lab for this purpose and give some feedback to the community on how the spectral response curve of at least my desktop kit’s webcam looks like. For public use, I’m thinking of using daylight spectra as a reference, as the shape is rather stable (not the intensity, due to atmospheric conditions). Maybe we can find a better solution for that.
- Measurements We need at least two measurements in order to run a spectral unmixing algorithm: upwelling radiance (light from the water) and downwelling irradiance (complete skylight). As we most likely won’t be able to build a cheap spectrometer that has even vaguely defined entry optics (e.g. 9deg field of view for the radiance and a perfect cosine response for the irradiance), some improvisation is needed. For the irradiance measurement I’m thinking of using a white table-tennis ball on top of the slit as a diffusor. The radiance measurement is mainly hampered by water surface reflections. To avoid those, I’d like to measure either just underneath the water surface (–> how to make the spectrometer water tight) or to use a sun shade (such as for camera lenses). For now, a black bucket with a hole in the bottom should do the job.
- Postprocessing The current procedure to extract a spectrum from the webcam-video is pretty smart and straightforward but probably not optimal if sensitivity is a priority. Currently, as I understand, only one row of the ‘stitched spectral image’ is used to extract the spectrum (‘set sample row’ in the workbench). Skylight, as well as the water leaving radiance are stable on the timescales of a measurement. Therefore I’d suggest to average over all rows to improve the signal to noise ratio. If that is not enough, one could think about extracting not only one line from the webcam’s video stream but e.g. ten and save the average in the stitched spectral image. In a last desperate step, one could use the whole webcam image and correct for the curvature caused by the DVD, however, I don’t think this will be necessary.
- This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
Research by philippg
TweetDrinking water quality standards describes the quality parameters set for drinking water. Despite the truism that every human on this planet needs drinking water to survive and that water can contain many harmful compounds, there are no universally recognized and accepted international standards for drinking water. Even where standards exist and are applied, the permitted […]
Drinking water quality standards describes the quality parameters set for drinking water. Despite the truism that every human on this planet needs drinking water to survive and that water can contain many harmful compounds, there are no universally recognized and accepted international standards for drinking water. Even where standards exist and are applied, the permitted concentration of individual constituents may vary by as much as ten times from one set of standards to another.
Many developed countries specify standards to be applied in their own country. In Europe, this includes the European Drinking Water Directive and in the USA the United States Environmental Protection Agency (EPA) establishes standards as required by the Safe Drinking Water Act. For countries without a legislative or administrative framework for such standards, the World Health Organization publishes guidelines on the standards that should be achieved. China adopted its own drinking water standard GB3838-2002 (Type II) enacted by Ministry of Environmental Protection in 2002.
Where drinking water quality standards do exist, most are expressed as guidelines or targets rather than requirements, and very few water standards have any legal basis or are subject to enforcement. Two exceptions are the European Drinking Water Directive and the Safe Drinking Water Act in the USA, which require legal compliance with specific standards.
In Europe, this includes a requirement for member states to enact appropriate local legislation to mandate the directive in each country. Routine inspection and, where required, enforcement is enacted by means of penalties imposed by the European Commission on non-compliant nations.
Countries with guideline values as their standards include Canada which has guideline values for a relatively small suite of parameters, New Zealand where there is a legislative basis but water providers have to make “best efforts” to comply with the standards in Australia.
Range of standards
Although drinking water standards are frequently referred to as if they are simple lists of parametric values, standards documents also specify the sampling location, sampling methods, sampling frequency, analytical methods and laboratory accreditation AQC. In addition, a number of standards documents also require calculation to determine whether a level exceeds the standard, such as taking an average. Some standards give complex, detailed requirements for the statistical treatment of results, temporal and seasonal variations, summation of related parameters, and mathematical treatment of apparently aberrant results.
A parametric value in this context is most commonly the concentration of a substance, e.g. 30 mg/l of Iron. It may also be a count such as 500 E. coli per litre or a statistical value such as the average concentration of copper is 2 mg/l. Many countries not only specify parametric values that may have health impacts but also specify parametric values for a range of constituents that by themselves are unlikely to have any impact on health. These include colour, turbidity, pH and the organoleptic (aesthetic) parameters (taste and odor).
It is possible and technically acceptable to refer to the same parameter in different ways that may appear to suggest a variation in the standard required. For example, nitrite may be measured as nitrite ion or expressed as N. A standard of “Nitrite as N” set at 1.4 mg/l equals a nitrite ion concentration of 4.6 mg/l – an apparent difference of nearly threefold.
Drinking water quality standards in Australia have been developed by the Australian Government National Health and Medical Research Council (NHMRC) in the form of the Australian Drinking Water Guidelines. These guidelines provide contaminant limits (pathogen, aesthetic, organic, inorganic and radiological) as well as guidance on applying limits for the management of drinking water in Australian drinking water treatment and distribution.
European Union standards
The following parametric standards are included in the Drinking Water directive and are expected to be enforced by appropriate legislation in every country in the European Union. Simple parametric values are reproduced here but in many cases the original directive also provides caveats and notes about many of the values given.
• Acrylamide 0.10 μg/l
• Antimony 5.0 μg/l
• Arsenic 10 μg/l
• Benzene 1.0 μg/l
• Benzo(a)pyrene 0.010 μg/l
• Boron 1.0 mg/l
• Bromate 10 μg/l
• Cadmium 5.0 μg/l
• Chromium 50 μg/l
• Copper 2.0 mg/l
• Cyanide 50 μg/l
• 1,2-dichloroethane 3.0 μg/l
• Epichlorohydrin 0.10 μg/l
• Fluoride 1.5 mg/l
• Lead 10 μg/l
• Mercury 1.0 μg/l
• Nickel 20 μg/l
• Nitrate 50 mg/l
• Nitrite 0.50 mg/l
• Pesticides 0.10 μg/l
• Pesticides – Total 0.50 μg/l
• Polycyclic aromatic hydrocarbons 0.10 μg/l Sum of concentrations of specified compounds;
• Selenium 10 μg/l
• Tetrachloroethene and Trichloroethene 10 μg/l Sum of concentrations of specified parameters
• Trihalomethanes — Total 100 μg/l Sum of concentrations of specified compounds
• Vinyl chloride 0.50 μg/l
United States standards
In the USA, the federal legislation controlling drinking water quality is the Safe Drinking Water Act (SDWA) which is implemented by the EPA, mainly through state or territorial primacy agencies. States and territories must implement rules at least as stringent as EPA’s to retain primary enforcement authority (primacy) over drinking water. Many states also apply their own state-specific standards which may be more rigorous or include additional parameters. Standards set by the EPA in the USA are not international standards since they apply to a single country. However, many countries look to the USA for appropriate scientific and public health guidance and may reference or adopt USA standards.
World Health Organisation (WHO) guidelines
The WHO guidelines include the following recommended limits on naturally occurring constituents that may have direct adverse health impact:
• Arsenic 0.010 mg/l
• Barium 10μg/l
• Boron 2400μg/l
• Chromium 50μg/l
• Fluoride 1500μg/l
• Selenium 40μg/l
• Uranium 30μg/l
For man-made pollutants potentially occurring in drinking water, the following standards have been proposed:
• Cadmium 3μg/l
• Mercury 6μg/l For inorganic mercury
• Benzene 10μg/l
• Carbon tetrachloride 4μg/l
• 1,2-Dichlorobenzene 1000μg/l
• 1,4-Dichlorobenzene 300μg/l
• 1,2-Dichloroethane 30μg/l
• 1,2-Dichloroethene 50μg/l
• Dichloromethane 20μg/l
• Di(2-ethylhexyl)phthalate 8 μg/l
• 1,4-Dioxane 50μg/l
• Edetic acid 600μg/l
• Ethylbenzene 300 μg/l
• Hexachlorobutadiene 0.6 μg/l
• Nitrilotriacetic acid 200μg/l
• Pentachlorophenol 9μg/l
• Styrene 20μg/l
• Tetrachloroethene 40μg/l
• Toluene 700μg/l
• Trichloroethene 20μg/l
• Xylenes 500μg/l
Comparison of parameters
The following table provides a comparison of a selection of parameters concentrations listed by WHO, the European Union, EPA and Ministry of Environmental Protection of China.
” indicates that no standard has been identified by editors of this article and ns indicates that no standard exists. μg/l -> Micro grams per litre or 0.001 ppm, mg/L -> 1 ppm or 1000 μg/l (Text made available under the Creative Commons Attribution-ShareAlike License: original found here: http://en.wikipedia.org/wiki/Drinking_water_quality_standards
World Health Organization
|Antimony||ns||5.0 μg/l||6.0 μg/l||“|
|Benzene||10μg/l||1.0 μg/l||5 μg/l||“|
|Benzo(a)pyrene||“||0.010 μg/l||0.2 μg/l||0.0028 μg/l|
|Bromate||“||10 μg/l||10 μg/l||“|
|Cadmium||3 μg/l||5 μg/l||5 μg/l||5 μg/l|
|Chromium||50μg/l||50 μg/l||0.1 mg/L||50 μg/l (Cr6)|
|Copper||“||2.0 mg/l||TT||1 mg/l|
|Cyanide||“||50 μg/l||0.2 mg/L||50 μg/l|
|1,2-dichloroethane||“||3.0 μg/l||5 μg/l||“|
|Fluoride||1.5 mg/l||1.5 mg/l||4 mg/l||1 mg/l|
|Lead||“||10 μg/l||15 μg/l||10 μg/l|
|Mercury||6 μg/l||1 μg/l||2 μg/l||0.05 μg/l|
|Nitrate||50 mg/l||50 mg/l||10 mg/L (as N)||10 mg/L (as N)|
|Nitrite||“||0.50 mg/l||1 mg/L (as N)||“|
|Pesticides (individual)||“||0.10 μg/ l||“||“|
|Pesticides — Total||“||0.50 μg/l||“||“|
|Polycyclic aromatic hydrocarbons l||“||0.10 μg/||“||“|
|Selenium||40 μg/l||10 μg/l||50 μg/l||10 μg/l|
|Tetrachloroethene and Trichloroethene||40μg/l||10 μg/l||“||“|
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
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  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. Experimental Analysis
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 , 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 . 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  and Romanian law .
3. Results and Discussion
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 . 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.
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  for the monitoring interval which is 0.2 mg/L.
Water systems are very vulnerable to nitrate pollution sources like septic systems, animal waste, commercial fertilizers, and decaying organic matter . 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 . 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 . 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  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 , 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-PO4, 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/
TweetEnvironmental Applications Keeping the water in our lakes, rivers, and streams clean requires monitoring of water quality at many points as it gradually makes its way from its source to our oceans. Over the years ever-increasing environmental concerns and regulations have heightened the need for increased diligence and tighter restrictions on wastewater quality. Control of […]
Keeping the water in our lakes, rivers, and streams clean requires monitoring of water quality at many points as it gradually makes its way from its source to our oceans. Over the years ever-increasing environmental concerns and regulations have heightened the need for increased diligence and tighter restrictions on wastewater quality. Control of water pollution was once concerned mainly with treating wastewater before it was discharged from a manufacturing facility into the nation’s waterways. Today, in many cases, there are restrictions on wastewater that is discharged to city sewer systems or to other publicly owned treatment facilities. Many jurisdictions even restrict or regulate the runoff of storm water — affecting not only industrial and commercial land, but also residential properties as well.
In its simplest form, water pollution management requires impoundment of storm water runoff for a specified period of time before being discharged. Normally, a few simple tests such as pH and suspended solids must be checked to verify compliance before release. If water is used in any way prior to discharge, then the monitoring requirements can expand significantly. For example, if the water is used for once-through cooling, testing may include temperature, pH, total dissolved solids (TDS), chemical oxygen demand (COD), and biochemical oxygen demand (BOD), to name a few.
Once water is used in a process, some form of treatment is often required before it can be discharged to a public waterway. If wastewater is discharged to a city sewer or publicly owned facility, and treatment is required, the quality is often measured and the cost is based not only on the quantity discharged, but also the amount of treatment required. As a minimum requirement suspended solids must be removed. Filtering or using clarifiers often accomplishes such removal. Monitoring consists of measuring total suspended solids (TSS) or turbidity.
If inorganic materials have been introduced into the water, their concentration must be reduced to an acceptable level. Inorganics, such as heavy metals, typically are removed by raising the pH to form insoluble metal oxides or metal hydroxides. The precipitated contaminants are filtered or settled out. Afterward, the pH must be adjusted back into a “normal” range, which often requires continuous monitoring of pH.
Organic materials by far require the most extensive treatment. Many different methods have been devised to convert soluble organic compounds into insoluble inorganic matter. Most of these involve some form of biological oxidation treatment. Bacteria are used to metabolize the organic materials into carbon dioxide and solids, which can be easily removed. To insure that these processes work smoothly and efficiently requires regular monitoring of the health of the biological organisms. The level of food (organic material), nutrients (nitrogen and phosphorous), dissolved oxygen, and pH are some of the parameters that must be controlled. After bio-oxidation the wastewater is filtered or clarified. Often the final effluent is treated with an oxidizing compound such as chlorine to kill any remaining bacterial agents, but any excess oxidant normally must be removed prior to discharge. Oxidation Reduction Potential (ORP)/Redox is ideal for monitoring the level of oxidants before and after removal. The final effluent stream must be monitored to make sure it meets all regulatory requirements.
The monitoring of wastewater pollution does not end there. Scientists are continuously testing water in streams, ground water, lakes, lagoons, and other bodies of water to determine if and what effects any remaining contamination is having on the receiving waters and its associated aquatic life. Measurements may include pH, conductivity, TDS, temperature, dissolved oxygen, TSS and organic levels (COD and BOD).
Environmental testing is not limited to monitoring of wastewater systems. Control of air emissions often includes gas-cleaning systems that involve the use of water. Wet scrubbers and wet electrostatic precipitators are included in this group. A flue gas desulfurization (FGD) system is one type of wet scrubber that uses slurry of lime, limestone, or other caustic material to react with sulfur compounds in the flue gas. The key to reliable operation of these units is proper monitoring of solids levels and pH. After use, the water in these systems must be treated or added to other wastewater from the plant, where it is treated by one of the methods previously discussed.
With proper monitoring, systems that maintain cleaner air and water can be operated efficiently and effectively. Such operation will go a long way toward maintaining a cleaner environment for future generations.
Myron L Meters offers a full line of handheld instruments and in-line monitor/controllers that can be used to measure or monitor many of the parameters previously mentioned. The following table lists some of the model numbers for measuring, monitoring, or controlling pH, conductivity, TDS and ORP. For additional information, please refer to our data sheets or Ask An Expert at MyronLMeters.com.
Note: When using a monitor/controller to measure pH in streams that contain heavy metals, sulfides, or other materials that react with silver, Myron L Meters recommends using a double junction pH sensor with a potassium nitrate (KNO3) reference gel to avoid fouling the silver electrode. See our 720II Sensor Selection Guide for pH and ORP Monitor/controllers for more information.
Ultrameter II 6P
Multi-Parameter: Conductivity, TDS, Resistivity, pH, ORP, Temperature, Free Chlorine (FCE)
+/-1% Accuracy of Reading
Memory Storage: Save up to 100 samples w/ Date & Time stamp
Wireless Download Module Optional
Tweet http://www.sciencedaily.com/releases/2011/03/110310070455.htm ScienceDaily (2011-03-10) — Researchers in Spain have developed an irrigation telecontrol system which will enable saving up to 20 percent of water for each harvest, compared to traditional irrigation methods. More at http://www.blog.MyronLMeters.com
ScienceDaily (2011-03-10) — Researchers in Spain have developed an irrigation telecontrol system which will enable saving up to 20 percent of water for each harvest, compared to traditional irrigation methods.
More at http://www.blog.MyronLMeters.com
TweetWater quality is the physical, chemical and biological characteristics of water. It is a measure of the condition of water relative to the requirements of the application. It is most frequently used by reference to a set of standards against which compliance can be assessed. The most common standards used to assess water quality relate […]
Water quality is the physical, chemical and biological characteristics of water. It is a measure of the condition of water relative to the requirements of the application. It is most frequently used by reference to a set of standards against which compliance can be assessed. The most common standards used to assess water quality relate to drinking water, safety of human contact and for the health of ecosystems.
Water quality is a very complex subject, in part because water is a complex medium intrinsically tied to the ecology of the Earth. Industrial pollution is a major cause of water pollution, as well as runoff from agricultural areas, urban stormwater runoff and discharge of treated and untreated sewage (especially in developing countries).
The complexity of water quality as a subject is reflected in the many types of measurements of water quality indicators. The list below represents some of the simple measurements that can be made on-site in direct contact with the water source in question:
- Total Dissolved Solids (TDS)
- Oxidation Reduction Potential (ORP)
- Dissolved oxygen
More complex measurements that must be made in a lab setting require a water sample to be collected, preserved, and analyzed at another location. Making these complex measurements can be expensive. Because direct measurements of water quality can be expensive, ongoing monitoring programs are typically conducted by government agencies. However, there are local volunteer programs and resources available for some general assessment. Tools available to the general public can be found here.
TweetThe need for proper dialysis water quality tests Kidney failure is a big problem in the U.S. and it is only growing. More than 350,000 Americans receive dialysis treatment through private clinics, independent centers, and hospitals, while 8% of U.S. dialysis patients treat themselves at home. As more and more Americans develop a need for […]
The need for proper dialysis water quality tests
Kidney failure is a big problem in the U.S. and it is only growing. More than 350,000 Americans receive dialysis treatment through private clinics, independent centers, and hospitals, while 8% of U.S. dialysis patients treat themselves at home.
As more and more Americans develop a need for dialysis treatment, water quality instrumentation manufacturers are looking for a way to help clinics improve their quality standards and efficiency.
Part of the problem
If you are constantly recalibrating your instruments, performing a decontamination process, or sending the meter in for repair, then you’re wasting time. As the number of dialysis patients increases, delays in the water quality testing add up. Today, you have options when it comes to testing dialysis water quality and dialysate composition.
Some instruments require annual calibration or an inconvenient decontamination process after each use. Using an instrument that requires direct contact with fluid means you have to decontaminate the meter before helping the next patient. If done incorrectly, the water treatment system and distribution piping can become contaminated, putting lives at risk.
More downtime occurs when dialysis meters have to be sent back to the manufacturer for annual calibration. If you are a clinician or biomedical equipment technician at a dialysis clinic, then you know how frustrating it is to work with problem instruments.
Make your job easier with the Digital Dialysate Meter™ D-6
MyronLMeters.com features the new Myron L Digital Dialysate Meter™ D-6.
Unlike other instruments, this meter does NOT have issues with holding calibration or giving consistently accurate readings. It does NOT have an inconvenient decontamination process or require any annual factory calibration. The meter does NOT use paper strips or reagents that expire or allow for subjective interpretation of results.
The D-6 simplifies testing in a variety of clinical applications: dialysate testing, water quality control, system disinfection, equipment calibration and effluent monitoring.
The D-6 tests both acetate and bicarbonate dialysate quality. It measures conductivity, pH and temperature to ensure proper mixing during dialysate preparation and as a final check of dialysate quality before hemodialysis treatment.
Order a bluDock™ Bluetooth Wireless Communication Package and your meter can communicate wirelessly with your computer to download your saved measurements. Say goodbye to clipboards, data entry, and human error.
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Tweet If you are a greenhouse grower then you are most likely familiar with the importance of proper water quality for your crops. Water quality can easily be determined by taking measurements periodically. It is important to use accurate and reliable equipment to perform the measurements. A wide selection of high quality conductivity testers and […]
If you are a greenhouse grower then you are most likely familiar with the importance of proper water quality for your crops. Water quality can easily be determined by taking measurements periodically. It is important to use accurate and reliable equipment to perform the measurements. A wide selection of high quality conductivity testers and hydroponic pH testers can be found here at an affordable price.
To determine the suitability of water for irrigation you can easily take measurements of the Electrical Conductivity (EC) and the Sodium Adsorption Ratio (SAR). In general, the higher the EC and SAR, the less suitable the water is for irrigation. Irrigation using water with high sodium adsorption ratio may require soil amendments to prevent long-term damage to the soil.
SAR measurements are provided with laboratory analysis of the water. However, EC measurements can be made using a portable EC meter. The Myron L AG6/pH was specifically designed as a pH and conductivity tester for greenhouse crops.
As a rule of thumb, the water is considered borderline and its use can present problems if conductivity values are higher than 0.8 millisiemens/cm (mS) and SAR is over 4. If the conductivity measurement is below 0.8 mS and the SAR measurement is below 4, the water is suitable for greenhouse irrigation. Particular management practices should be used when water is outside the acceptable limits. This might include using a growing medium with excellent drainage, leaching with every watering and compensating the sodium with calcium and magnesium.
If galvanized steel is used throughout the greenhouse and water is reclaimed for irrigation, it is a good idea to check the amount of Zinc in the water and make nutrient correction accordingly.
Many greenhouses use drip irrigation systems, which are efficient and low maintenance, but nozzles can become clogged by hard water. Check for high levels of bicarbonates (above 100 ppm) in the water and neutralize with the appropriate acids.
There are many factors that affect water quality and greenhouse crop growth. Consult your fertilizer manufacturer for recommendations on proper nutrient levels.