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| :. ABOUT WATER |
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WATER CONTAMINANTS
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MOST COMMON WATER CONTAMINANTS
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( Its SOURCES and METHOD OF TREATMENT) |
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Source - Nitrate (NO3) comes into water supplies through the nitrogen cycle rather than via dissolved minerals. It is one of the major ions in natural waters. Most nitrate that occurs in drinking water is the result of contamination of ground water supplies by septic systems, feed lots, and agricultural fertilizers. Nitrate is reduced to nitrite in the body. The US EPA's MCL for nitrate is 10 mg/l. |
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Treatment -
Reverse Osmosis will remove 92 - 95% of the nitrates and/or nitrites. Anion exchange resin will also remove both as will distillation. |
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ODOR |
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Source – Taste and odor problems of many different types can be encountered in drinking water. Troublesome compounds may result from biological growth or industrial activities. The tastes and odors may be produced in the water supply, in the water Treatment plant from reactions with Treatment chemicals, in the distribution system, and/or in the plumbing of consumers. Tastes and odors can be caused by mineral contaminants in the water, such as the "salty" taste of water when chlorides are 500 mg/l or above, or the "rotten egg" odor caused by hydrogen sulfide. Odor in the drinking water is usually caused by blue-green algae. Moderate concentrations of algae in the water can cause it to have a "grassy", "musty" or "spicy" odor. Large quantities can cause the water to have a"rotten", "septic", "fishy" or "medicinal" odor. Decaying vegetation is probably the most common cause for taste and odor in surface water supplies. In treated water supplies chlorine can react with organics and cause odor problems .
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Treatment– Odor can be removed by oxidation-reduction or by activated carbon adsorption. Aeration can be utilized if the contaminant is in the form of a gas, such as H2S (hydrogen sulfide). The most effective oxidizers for treating taste and odor, are chlorine dioxide and ozone. Activated carbon has an excellent history of success in treating taste and odor problems. The life of the carbon depends on the presence of organics competing for sites and the concentration of the odor causing compound.
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ORGANICS |
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Source – Organic matter makes up a significant part of the soil, therefore water soluble organic compounds are present in all water supplies. Organic matter is reported on a water analysis as carbon, as it is in the TOC (total organic carbon) determination. Three major sources of organics are (1) Breakdown of naturally occurring organic materials which is comprised of humic materials, microorganisms, and petroleum-based aliphatic and aromatic hyrdrocarbons. (2) Domestic and commercial chemical wastes include wastewater discharges, agricultural runoff, urban runoff, and leaching from contaminated soils (3) Chemical reactions that occur during Water Treatment Process include disinfection by-products such as THM’s (Trihalomethanes), or undesirable components of piping assembly such as joint adhesives. |
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Treatment – Activated carbon is generally used to remove organics, color, and taste-and-odor causing compounds. The contact time and service flow rate dictate the size of the carbon filter. When removing organics, restrict flow rates to 2 gpm per square foot of the filter bed. Reverse Osmosis will remove 98 to 99% of the organics in the water. Ultrafiltration (UF) and nanofiltration (NF) have both been proven to remove organics. Anion exchange resin also retains organics, but periodically needs cleaning. |
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