TweetChlorine Residuals The presence of free chlorine in drinking water indicates that: 1) a sufficient amount of chlorine was added to the water to inactivate most of the bacteria and viruses that cause diarrheal disease; and, 2) the water is protected from recontamination during transport to the home, and during storage of water in the [...]
The presence of free chlorine in drinking water indicates that: 1) a sufficient amount of chlorine was added to the water to inactivate most of the bacteria and viruses that cause diarrheal disease; and, 2) the water is protected from recontamination during transport to the home, and during storage of water in the household. Because the presence of free residual chlorine in drinking water indicates the likely absence of disease-causing organisms, it is used as one measure of the potability of drinking water.
When chlorine is added to water as a disinfectant, a series of reactions occurs. These reactions are graphically depicted later in this article. The first of these reactions occurs when organic materials and metals present in the water react with the chlorine and transform it into compounds that are unavailable for disinfection. The amount of chlorine used in these reactions is termed the chlorine demand of the water. Any remaining chlorine concentration after the chlorine demand is met is termed total chlorine. Total chlorine is further subdivided into: 1) the amount of chlorine that then reacts with nitrates present in the water and is transformed into compounds that are much less effective disinfectants than free chlorine (termed combined chlorine); and, 2) the free chlorine, which is the chlorine available to inactivate disease-causing organisms, and is thus a measure used to determine the potability of water.
For example, when chlorine is added to completely pure water the chlorine demand will be zero, and there will be no nitrates present, so no combined chlorine will be formed. Thus, the free chlorine concentration will be equal to the concentration of chlorine added. When chlorine is added to natural waters, especially water from surface sources such as rivers, organic material will exert a chlorine demand, and combined chlorine will be formed by reaction with nitrates. Thus, the free chlorine concentration will be less than the concentration of chlorine initially
Chlorine Addition Flow Chart
Testing Free Chlorine in Drinking Water
Testing free chlorine is recommended in the following circumstances:
• To conduct dosage testing in project areas
• To monitor and evaluate projects by testing stored drinking water in households
The goal of dosage testing is to determine how much sodium hypochlorite solution to add to water that will be used for drinking to maintain free chlorine residual in the water for the average time of storage of water in the household (typically 24 hours). This goal differs from the goal of infrastructure-based (piped) water treatment systems, whose aim is effective disinfection at the endpoints (i.e., water taps) of the system. The WHO recommends “a residual concentration of free chlorine of greater than or equal to 0.5 mg/litre after at least 30 minutes contact time at pH less than 8.0.” This definition is only appropriate for users who obtain water directly from a flowing tap. A free chlorine level of 0.5 mg/L can maintain the quality of water through a distribution network, but is not optimal to maintain the quality of the water when it is stored in the home in a bucket or jerry can for 24 hours.
1. At 1 hour after the addition of sodium hypochlorite solution to water there should be no more than 2.0 mg/L of free chlorine residual present (this ensures the water does not have an unpleasant taste or odor).
2. At 24 hours after the addition of sodium hypochlorite to water in containers that are used by families for water storage there should be a minimum of 0.2 mg/L of free chlorine residual present (this ensures microbiologically clean water).
This methodology is approved by the World Health Organization (WHO), and is graphically depicted below. The maximum allowable WHO value for free chlorine residual in drinking water is 5 mg/L. The minimum recommended WHO value for free chlorine residual in treated drinking water is 0.2 mg/L. CDC recommends not exceeding 2.0 mg/L due to taste concerns, and chlorine residual decays over time in stored water.
1. Free Chlorine as an Indicator of Sanitizing Strength
Chlorine, which kills bacteria by way of its power as an oxidizing agent, is the most popular germicide used in water treatment. Chlorine is not only used as a primary disinfectant, but also to establish a sufficient residual level of Free Available Chlorine (FAC) for ongoing disinfection.
FAC is the chlorine that remains after a certain amount is consumed by killing bacteria or reacting with other organic (ammonia, fecal matter) or inorganic (metals, dissolved CO2, Carbonates, etc) chemicals in solution. Measuring the amount of residual free chlorine in treated water is a well accepted method for determining its effectiveness in microbial control.
The Myron L Company FCE method for measuring residual disinfecting power is based on ORP, the specific chemical attribute of chlorine (and other oxidizing germicides) that kills bacteria and microbes.
2. FCE Free Chlorine Unit
The 6PIIFCE is the first handheld device to detect free chlorine directly, by measuring ORP. The ORP value is converted to a concentration reading (ppm) using a conversion table developed by Myron L Company through a series of experiments that precisely controlled chlorine levels and excluded interferants.
Other test methods typically rely on the user visually or digitally interpreting a color change resulting from an added reagent-dye. The reagent used radically alters the sample’s pH and converts the various chlorine species present into a single, easily measured species. This ignores the effect of changing pH on free chlorine effectiveness and disregards the fact that some chlorine species are better or worse sanitizers than others.
The Myron L Company 6PIIFCE avoids these pitfalls. The chemistry of the test sample is left unchanged from the source water. It accounts for the effect of pH on chlorine effectiveness by including pH in its calculation. For these reasons, the Ultrameter II’s FCE feature provides the best reading-to-reading picture of the rise and fall in sanitizing effectivity of free available chlorine.
The 6PIIFCE also avoids a common undesirable characteristic of other ORP-based methods by including a unique Predictive ORP value in its FCE calculation. This feature, based on a proprietary model for ORP sensor behavior, calculates a final stabilized ORP value in 1 to 2 minutes rather than the 10 to 15 minutes or more that is typically required for an ORP measurement.
Tweet If you’re like Veolia, you have locations in 69 countries. Nalco operates in 130 countries. Why should they have to ship Ultrameters to their employees? They shouldn’t – it’s so fast, cheap, and easy to use Myron L Meters worldwide shipping. It’s easy – just click the Secure International [...]
If you’re like Veolia, you have locations in 69 countries. Nalco operates in 130 countries. Why should they have to ship Ultrameters to their employees? They shouldn’t – it’s so fast, cheap, and easy to use Myron L Meters worldwide shipping. It’s easy – just click the Secure International Checkout button when you check out and follow the instructions. You’ll be surprised by our low rates.
How much does it cost to ship an Ultrameter II 6P to…
Rio de Janeiro?
With the 10% discount you receive at MyronLMeters.com, you can ship an Ultrameter II 6P to China for less than most American companies pay for it. So…now what’s stopping you?
Please visit us on the web at:
TweetWhat is pH? pH measures the activity of the (solvated) hydrogen ion. Pure water has a pH very close to 7 at 25°C. Solutions with a pH less than 7 are acidic and solutions with a pH greater than 7 are basic or alkaline. The pH scale is traceable to a set of standard solutions [...]
What is pH?
pH measures the activity of the (solvated) hydrogen ion. Pure water has a pH very close to 7 at 25°C. Solutions with a pH less than 7 are acidic and solutions with a pH greater than 7 are basic or alkaline. The pH scale is traceable to a set of standard solutions whose pH is established by international agreement. Measuring pH for aqueous solutions can be done with a glass electrode and a pH meter, or using indicators.
Measuring pH is important in water treatment, medicine, biology, chemistry, agriculture, forestry, food science, environmental science, oceanography, civil engineering, chemical engineering, and many other applications.
p[H] was first introduced by Danish chemist Søren Peder Lauritz Sørensen at the Carlsberg Laboratory in 1909 and revised to the modern pH in 1924 to accommodate definitions and measurements in terms of electrochemical cells. According to the Carlsberg Foundation pH stands for “power of hydrogen”.
pH is defined as the decimal logarithm of the reciprocal of the hydrogen ion activity, aH+, in a solution.
A pH meter is an electronic device used for measuring the pH (acidity or alkalinity) of a liquid (though special probes are sometimes used to measure the pH of semi-solid substances). A typical pH meter consists of a special measuring probe (a glass electrode) connected to an electronic meter that measures and displays the pH reading.
The pH probe measures pH as the activity of the hydrogen cations surrounding a thin-walled glass bulb at its tip. The probe produces a small voltage (about 0.06 volt per pH unit) that is measured and displayed as pH units by the meter. For more information about pH probe care or replacement, please consult your Myron L meter operations manual.
Calibration and use
*Please consult your Myron L meter operations manual before calibrating.
For very precise work the pH meter should be calibrated before each measurement. For normal use calibration should be performed at the beginning of each day. The reason for this is that the glass electrode does not give a reproducible e.m.f. over longer periods of time. Calibration should be performed with at least two standard buffer solutions that span the range of pH values to be measured. For general purposes buffers at pH 4 and pH 10 are acceptable. The pH meter has one control (calibrate) to set the meter reading equal to the value of the first standard buffer and a second control (slope) which is used to adjust the meter reading to the value of the second buffer. A third control allows the temperature to be set. Standard buffer solutions, which can be obtained from MyronLMeters.com here:
usually state how the buffer value changes with temperature. For more precise measurements, a three buffer solution calibration is preferred. As pH 7 is essentially, a “zero point” calibration (akin to zeroing a scale), calibrating at pH 7 first, calibrating at the pH closest to the point of interest ( e.g. either 4 or 10) second and checking the third point will provide a more linear accuracy to what is essentially a non-linear problem. Some meters will allow a three point calibration and that is the preferred scheme for the most accurate work, and is recommended by Myron L Meters. Higher quality meters will have a provision to account for temperature coefficient correction, and high-end pH probes have temperature probes built in. The calibration process correlates the voltage produced by the probe (approximately 0.06 volts per pH unit) with the pH scale. After each single measurement, the probe is rinsed with distilled water or deionized water to remove any traces of the solution being measured, blotted with a scientific wipe to absorb any remaining water which could dilute the sample and thus alter the reading, and then quickly immersed in another solution.
Storage conditions of the glass probes
When not in use, the glass probe tip must be kept wet at all times to avoid the pH sensing membrane dehydration and the subsequent dysfunction of the electrode. You can get your sensor storage solution here:
A glass electrode alone (i.e., without combined reference electrode) is typically stored immersed in an acidic solution of around pH 3.0. In an emergency, acidified tap water can be used, but distilled or deionised water must never be used for longer-term probe storage as the relatively ionless water “sucks” ions out of the probe membrane through diffusion, which degrades it.
Combined electrodes (glass membrane + reference electrode) are better stored immersed in the bridge electrolyte (often KCl 3 M) to avoid the diffusion of the electrolyte (KCl) out of the liquid junction.
Cleaning and troubleshooting of the glass probes
Occasionally (about once a month), the probe may be cleaned using pH-electrode cleaning solution; generally a 0.1 M solution of hydrochloric acid (HCl) is used, having a pH of one.
In case of strong degradation of the glass membrane performance due to membrane poisoning, diluted hydrofluoric acid (HF < 2 %) can be used to quickly etch (< 1 minute) a thin damaged film of glass. Alternatively a dilute solution of ammonium fluoride (NH4F) can be used. To avoid unexpected problems, the best practice is however to always refer to the electrode manufacturer recommendations or to a classical textbook of analytical chemistry.
Types of pH meters
A pH meter for every industry
pH meters range from simple and inexpensive pen-like devices to complex and expensive laboratory instruments with computer interfaces and several inputs for indicator and temperature measurements to be entered to adjust for the slight variation in pH caused by temperature. Specialty meters and probes are available for use in special applications, harsh environments, etc. Myron L Meters offers a simple pen-style pH meter, analog handheld meters, digital handheld multiparameter meters, and inline monitor/controllers.
ULTRAPEN PT2 pH and Temperature Pen
Accuracy of +/- 0.01 pH
Reliable Repeatable Results
Automatic Temperature Compensation
Durable, Fully Potted Circuitry
Comes with 2oz bottle of pH Storage Solution
Agri-Meter – Ag-6: 0-5 millimhos; 2-12 pH
Instant and accurate TDS tests
Electronic Internal Standard for easy field calibration
Fast Auto Temperature Compensation
Rugged design for years of trouble-free testing
Simple to use
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
The advanced “isolated” circuitry of the 720 Series II pH/ORP Monitor/ controllers guarantees accurate and reliable measurements — completely eliminating ground-loop and noise issues.
The unique sensor preamp allows for longer distances between the sensor and the Monitor/controller without the loss of accuracy or reliability.
All Myron L Monitor/controllers feature a highly refined and precise Temperature Compensation circuit. This feature perfectly matches the NERNST equation correcting the displayed reading to 25′C. The TC may be disabled to conform to USP requirements.
TweetContamination of circuit boards can bring about severe degradation of insulation resistance and dielectric strength. Cleanliness of completed circuit boards is, therefore, of vital interest. For those companies who have established circuit board cleaning procedures, the MIL Spec P-28809 has been used as a guideline for control. Now a simple “on line” test for the [...]
Contamination of circuit boards can bring about severe degradation of insulation resistance and dielectric strength. Cleanliness of completed circuit boards is, therefore, of vital interest.
For those companies who have established circuit board cleaning procedures, the MIL Spec P-28809 has been used as a guideline for control. Now a simple “on line” test for the relative measurement of ionic contamination has been developed.
This fast and economical method for testing circuit board cleanliness uses an Ultrameter II™ 4P or 6P, a suitable container, and a mixture of Dl (deionized) water and alcohol. The procedure is as follows:
1. Mix a stock quantity of solution using 25 parts by volume of Dl water and 75 parts by volume of 99% isopropyl alcohol. The conductivity, measured with the Ultrameter II 4P or 6P should be a maximum of 0.166 micromhos/microseimens/cm.
2. Measure out an amount of the water/alcohol mixture equal to 100 ml per 10 square inches of circuit board surface to be tested (considering both sides of the board but not components), and add 60 ml additional. In other words: 2(L X W) (10 ml) + 60 ml = total solution needed.
3. Fill a poly “zip-lock” bag or other suitable plastic or glass container with the measured water/alcohol solution.
4. Using the measured water/alcohol solution in the poly bag, rinse out the Ultrameter II’s cell cup three (3) times, discarding the rinse solution each time. Fill the instrument cell cup a fourth time and take a meter reading. This value should be 0.166 micromhos/microseimens/cm or less and is the very clean control (or “comparison”) reading for the test.
5. Being very careful not to contaminate the PCB, totally immerse the circuit board in the solution. Seal bag. Allow it to soak for three (3) minutes with mild agitation.
6. At the conclusion of the soaking, pour the solution directly into the instruments cell cup four (4) times; take the fourth reading.
7. Compare the control reading in Step 4 with the reading taken in Step 6 (The higher the difference between the two readings, the greater the ionic contamination). Record this final extract reading for comparison with other boards tested in the same manner.
The level of cleanliness needed can be determined by each individual company.
Mil Spec P-28809 can be used as a guideline, or standards can be established based upon available data. In either event, the comparative method using the Myron L Ultrameter II will assist in the determination of that level of cleanliness.
The United States has the most comprehensive system of assistance for veterans of any nation in the world. This benefits system traces its roots back to 1636, when the Pilgrims of Plymouth Colony were at war with the Pequot Indians. The Pilgrims passed a law which stated that disabled soldiers would be supported by the colony.
The Continental Congress of 1776 encouraged enlistments during the Revolutionary War by providing pensions for soldiers who were disabled. Direct medical and hospital care given to veterans in the early days of the Republic was provided by the individual States and communities. In 1811, the first domiciliary and medical facility for veterans was authorized by the Federal Government. In the 19th century, the Nation’s veterans assistance program was expanded to include benefits and pensions not only for veterans, but also their widows and dependents.
After the Civil War, many State veterans homes were established. Since domiciliary care was available at all State veterans homes, incidental medical and hospital treatment was provided for all injuries and diseases, whether or not of service origin. Indigent and disabled veterans of the Civil War, Indian Wars, Spanish-American War, and Mexican Border period as well as discharged regular members of the Armed Forces were cared for at these homes.
Congress established a new system of veterans benefits when the United States entered World War I in 1917. Included were programs for disability compensation, insurance for service persons and veterans, and vocational rehabilitation for the disabled. By the 1920s, the various benefits were administered by three different Federal agencies: the Veterans Bureau, the Bureau of Pensions of the Interior Department, and the National Home for Disabled Volunteer Soldiers.
The establishment of the Veterans Administration came in 1930 when Congress authorized the President to “consolidate and coordinate Government activities affecting war veterans.” The three component agencies became bureaus within the Veterans Administration. Brigadier General Frank T. Hines, who directed the Veterans Bureau for seven years, was named as the first Administrator of Veterans Affairs, a job he held until 1945.
The VA health care system has grown from 54 hospitals in 1930, to include 152 hospitals; 800 community based outpatient clinics; 126 nursing home care units; and 35 domiciliaries. VA health care facilities provide a broad spectrum of medical, surgical, and rehabilitative care. The responsibilities and benefits programs of the Veterans Administration grew enormously during the following six decades. World War II resulted in not only a vast increase in the veteran population, but also in large number of new benefits enacted by the Congress for veterans of the war. The World War II GI Bill, signed into law on June 22, 1944, is said to have had more impact on the American way of life than any law since the Homestead Act of 1862. Further educational assistance acts were passed for the benefit of veterans of the Korean Conflict, the Vietnam Era, Persian Gulf War, Iraq and Afghanistan wars.
In 1973, the Veterans Administration assumed another major responsibility when the National Cemetery System (except for Arlington National Cemetery) was transferred to the Veterans Administration from the Department of the Army. The Agency was charged with the operation of the National Cemetery System, including the marking of graves of all persons in national and State cemeteries (and the graves of veterans in private cemeteries, upon request) as well and administering the State Cemetery Grants Program. The Department of Veterans Affairs (VA) was established as a Cabinet-level position on March 15, 1989. President Bush hailed the creation of the new Department saying, “There is only one place for the veterans of America, in the Cabinet Room, at the table with the President of the United States of America.”
In 2009, President Obama appointed Secretary Eric K. Shinseki to lead a massive transformation of the VA into a high-performing 21st century organization that can better serve Veterans. Under the leadership of Secretary Shinseki, the VA has adopted three guiding principles to govern the changes underway, namely being people-centric, results-driven, and forward-looking. These principles are reflected in the 16 major initiatives that serve as a platform from which transformation is being executed.
The 16 major initiatives are:
Eliminating Veteran homelessness
Enabling 21st century benefits delivery and services
Automating GI Bill benefits
Creating Virtual Lifetime Electronic Record
Improving Veterans’ mental health
Building Veterans Relationship Management capability to enable convenient, seamless interactions
Designing a Veteran-centric health care model to help Veterans navigate the health care delivery system and receive coordinated care
Enhancing the Veteran experience and access to health care
Ensuring preparedness to meet emergent national needs
Developing capabilities and enabling systems to drive performance and outcomes.
Establishing strong VA management infrastructure and integrated operating model
Transforming human capital management
Performing research and development to enhance the long-term health and well-being of Veterans
Optimizing the utilization of VA’s Capital portfolio by implementing and executing the Strategic Capital Investment Planning (SCIP) process
Improving the quality of health care while reducing cost
Transforming health care delivery through health informatics
Myron L Meters is proud to do business with the VA.
Please visit us on the web at:
Tweet Testimonials -I have been using your handheld conductivity meters forever, and they are the benchmark. J. Engel, Wastewater Treatment Technician ‘ -We are getting constant replies from our customers about the Ultrameter II’s very accurate measurements and water resistance. T. Abaci, Water Analysis Professional -I was so impressed with the Ultrameter II and its ability to hold [...]
-We are getting constant replies from our customers about the Ultrameter II’s very accurate measurements and water resistance.
T. Abaci, Water Analysis Professional
-The Agri-Meter is a good product, not overpriced, works great and is dependable, too.
D. Atkins, Landscape Professional
-We have started replacing our NEO-STAT+ conductivity meters with Myron L D-1 meters in our dialysis centers.
R. Kaune, Biomedical Engineer
-You guys make a great product and I can’t live without it.
J. Dusek, Professional Greenhouse Grower
TweetMeasuring the pH of pure DI water is easy when you know what to expect. In theory, pure water should have a pH of 7. When you actually measure the pH, it will most likely fall between 5.5 and 7 due to its absorption of CO2 from the atmosphere. This natural occurrence forms carbonic acid [...]
Measuring the pH of pure DI water is easy when you know what to expect. In theory, pure water should have a pH of 7. When you actually measure the pH, it will most likely fall between 5.5 and 7 due to its absorption of CO2 from the atmosphere. This natural occurrence forms carbonic acid in the water, lowering the pH. Since DI water is pure, there is nothing to buffer it and stabilize the pH. Below are a few tips to increase the accuracy of your pH measurements.
Tips for accurate pH readings
- First and foremost, use a high quality ph meter and ensure that it is properly calibrated with pH buffer solution. Check the manufacturer’s recommendations for calibration. The Ultrameter II 6P and the Techpro II TPH1 are portable pH meters that are extremely accurate and easy to use.
- When using a portable pH meter, avoid cross-contamination by thoroughly rinsing with the DI water that you will be sampling. If a glass beaker or cup is to be used, rinse that as well.
- Use small samples and minimize exposure to air, as this will lower the pH value. Taking samples from an open-air drum or tank will typically give erroneous readings. Collect samples from a sample port if possible.
- If you have access to high-purity reagent grade KCl (Potassium Chloride) salts, then you can buffer the DI water to stabilize the pH. Adding a tiny amount to the pure DI water sample will increase the ionic strength and reduce the absorption of CO2 from the atmosphere. Be careful not to contaminate the KCl salts. Use proper tools/utensils to add the KCl salts
- If no salt is available and all you need is a quick check of your system, you can flow the water from a sample port into your portable pH meter to measure the pH values. This will take slightly longer to stabilize. Be sure to use an accurate, waterproof pH meter and hold it closely to the sample port.
- Changes in temperature can affect the pH. Use a pH meter that is temperature compensated to remedy this issue.
If you need pH buffer solution, you can find it here at an affordable price.