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Abstract:
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Iron is objectionable constituent when present in drinking and process water more than the desired limit. Different iron removal methods and their modifications have been applied for iron removal. However, conventional methods are found expensive and there isan increasing tendency against the use of chemicals in watertreatment. Dry filter is one of the alternatives that can be applied for iron removal and the process uses the self-purificationcapacities of iron bacteria. These micro-organisms are found to adapt themselves to the prevailing conditions provided the enviroment is made favourable for them, such as ventilation, provision of surface media for their growth, raw water supply etc. Investigations made on the pilot plants showed that iron removal process by dy filtration depends on the hydraulic load, filter depth, size of filter material, the development of the micro-organisms, and iron concentration in the raw water. Dry filter does not only remove iron but it also removes manganese, ammonia, carbon dioxide and provides sufficient oxygen supply to the treated water. The results obtained from the test plants were not below the standard limits except from the full scale production plant. However, complete removal of iron by dry filter is feasible provided the best possible favourable combinations of the factors on which iron removal depends are found. Micro-biological water treatment is certainly more appropriate to natural drinking water than production of chemically treated "water" in water treatment works. The biological process as to how these micro-organisms remove iron is stilla unanswered. /Kir09 |