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MOST COMMON WATER CONTAMINANTS
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( Its SOURCES and METHOD OF TREATMENT) |
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Source -
Manganese (Mn+4, Mn+2) is present in many soils and sediments as well as in rocks whose structures have been changed by heat and pressure. As essential to plant and animal life it can be derived from such foods as corn, spinach, and whole wheat products. Manganese may be found in deep well waters at concentrations as high as 2 - 3 mg/l. High levels of manganese in the water produces an unpleasant odor and taste. Organic materials can tie up manganese in the same manner as they do iron, therefore destruction of the organic matter is a necessary part of manganese removal. |
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Treatment - Removal of manganese can be done by ion exchange (sodium form cation - softener) or chemical oxidation - retention - filtration. Removal with a water softener dictates that the pH be 6.8 or higher and is beneficial to use countercurrent regeneration with brine make-up and backwash utilizing soft water. It takes 1 ppm of oxygen to treat 1.5 ppm of manganese. Greensand filter with potassium will remove up to 10 ppm if pH is above 8.0. Birm filter with air injection will reduce manganese if pH is 8.0 to 8.5. Chemical feed (chlorine, potassium permanganate, or hydrogen peroxide) followed by 20 minutes retention and then filtered with birm, greensand, carbon, or Filter Ag will also remove the manganese. |
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MERCURY |
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Source – Mercury (Hg) is one of the least abundant elements in the earth's crust. It exists in two forms, an inorganic salt or an organic compound (methyl mercury). Mercury detected in drinking water is of the inorganic type. Organic mercury inters the food chain through fish and comes primarily from industrial chemical manufacturing waste or from the leaching of coal ash. If inorganic mercury inters the body, it usually settles in the kidneys. Whereas organic mercury attacks the central nervous system.
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(Ammonia is not found in well water supplies because the bacteria in the soil converts its nitrates ) |
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Treatment–Activated carbon filtration is very effective for the removal of mercury. Reverse osmosis will remove 95 - 97 % of it.
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METHANE |
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Source – Methane (CH4), often called marsh gas, is the primary component of natural gas. It is commonly found where land fills once existed and is generated from decaying of plants or other carbon based matter. It can also be found in and around oil fields. Methane is colorless, odorless, nearly invisible, highly flammable, and often found in conjunction with other gases such as hydrogen sulfide. Even though methane gas gives water a milky appearance which makes it aesthetically unpleasant, there are no known health effects.
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Treatment –Aeration or degasification is the only way to eliminate the problem of methane gas. Venting the casing and/or the cap of the well will reduce the problem of methane in the water, but may not completely eliminate it. Another method is to provide an atmospheric holding tank where the methane laden water can be vented to allow the gas to dissipate. This method may not be 100% effective either. An aerator or degasifier is the proper piece of equipment to utilize for the removal of methane. Water is introduced through the top, sometimes through spray nozzles, and allowed to percolate through a packing material. Air is forced in the opposite direction to the water flow. The water is then collected in the bottom of the unit and repressurized. |
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