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.
MyronLMeters.com today announced the arrival of a new Myron L product, the Myron L Ultrameter III, a reliable, easy-to-use meter that measures 9 parameters – conductivity, resistivity, TDS, alkalinity, hardness, saturation index, ORP/free chlorine, pH and temperature.
MyronLMeters.com today announced the arrival of a new Myron L product, the , Myron L Ultrameter III 9P , a reliable, easy-to-use meter that measures 9 parameters – conductivity, resistivity, TDS, alkalinity, hardness, saturation index, ORP/free chlorine, pH and temperature.
“The Ultrameter III is available right now at MyronLMeters.com,” said James Rutan, president. “We’ve made it easy to order, offer great training videos, technical bulletins, manuals, and a 10% discount…just for ordering online. In addition, all Myron L Meters in stock will ship the next business day. The quality of the Ultrameter III and the company’s great reputation for reliable meters is sure to make this a big hit. Don’t forget – this new Ultrameter has wireless data transfer capability when you buy the bluDock. Expect about a 10 day lead time for a week or so.”
MyronLMeters.com carries the full line of Ultrameter III accessories, including the Ultrameter III 9PTK AHL Titration kit, soft protective case, replacement sensors, and the full line of standard solutions and buffers – all at a 10% discount when you order online.
Myron L meters are renowned for their accuracy, reliability, and ease of use, and have applications in automatic rinse tank controls, boiler and cooling towers, circuit board cleanliness testing, deionized water, environmental applications, fountain solutions, dialysis, horticulture, hydroponics, ORP (oxidation reduction potential)/Redox, pool and spa, reverse osmosis, textiles.
MyronLMeters.com has a well-established web presence on Facebook, Gravatar, Twitter, Squidoo, LinkedIn, and WordPress. MyronLMeters.com encourages customers to join them on these sites for special offers and discounts.
Tags: MyronLMeters.com, Myron L, Myron L meters, Ultrameter III, conductivity, resistivity, TDS, alkalinity, hardness, saturation index, ORP/free chlorine, pH and temperature, automatic rinse tank controls, boiler and cooling towers, circuit board cleanliness testing, deionized water, environmental applications, fountain solutions, dialysis, horticulture, hydroponics, ORP (oxidation reduction potential)/Redox, pool and spa, reverse osmosis, textiles
TweetIn order to test the swimming pool water quality, you need to know what you’re testing. Some of the basic parameters that are measured for pools include pH, Chlorine, Total Alkalinity, Calcium Hardness, and Total Dissolved Solids. A balanced swimming pool really only needs to have the pH and chlorine levels checked and corrected on [...]
In order to test the swimming pool water quality, you need to know what you’re testing. Some of the basic parameters that are measured for pools include pH, Chlorine, Total Alkalinity, Calcium Hardness, and Total Dissolved Solids.
Many swimming pool and spa professionals use portable instruments to test the water quality during treatment. If you are a homeowner with a pool, you may want to consider using an instrument as opposed to the simple test kits with liquid droplets or tablets. If you need an instrument, check out the selection here: MyronLMeters.com. The instruments are much more accurate and can provide immediate, reliable results. If you are using the test kits, there are a few things to note. Expired tablets/ test liquids (reagents) should be thrown out as they very often give inaccurate readings, resulting in improper treatment, wasting expensive chemicals and possibly damaging the pool and filtration equipment. Always keep the test kit in a cool dry place out of the sun and out of the reach of children.
When testing the pool water, rinse the cell cups of your instrument or test kit thoroughly before filling them with water from at least 20-30 cm below the surface of the swimming pool. When you’re finished testing the water be sure not to pour the samples back into the pool.
As a general rule of thumb, tests for pH and chlorine should be done weekly. If there are no obvious problems in your swimming pool (algae growth, cloudy water, lime scale buildup, etc) then you can test for Total Alkalinity, Calcium Hardness, and Total Dissolved Solids approximately every month.
Swimming pool chemistry can seem intimidating, so consulting a swimming pool professional is not a bad idea. Some will visit your pool and perform the test or you can take a sample directly to your local pool supply store and they may be able to test it for you.
If the water in your area is free from any metals and your swimming pool shows none of the symptoms of iron or copper presence, the test for these metals is unnecessary. If, however, you notice staining on the walls and floor of the swimming pool, you should have the levels of these metals checked and treated if necessary.
For a more in-depth study of pool water testing, visit the link below:
The Association of Pool and Spa Professionals (APSP) is a great resource for individuals and companies that want to learn more about water treatment for pools and spas.