DEVELOPMENT OF A PRESSURE CHEMICAL DOSER

Abstract

Survey of Water treatment plants in India by Central Public Health Research Institute Nagpur has revealed that chemical feeding is the weakest link in the Treatment process, Propriety equipment available for the purpose are very costly to purchase, operate, maintain and are generally found out of order. A simple and sturdy device for chemical feedirg is an immediate need for our country, specially for rural areas. A simple chemical solution doser, consisting of a plastic painted steel pressure vessel placed on a branch from the main flow has been experimented upon for feeding bleaching powder solution and alum both for gravity flow and for flow under pressure. A part of the water flows through the branch takes chemical from the solution holder and feeds it back to the main flow. It can be operated on saturated solution for the chemicals easily soluble in water leaving no sediment such as alum by keeping excess chemical in the vessel, In case of chemicals leaving sediment such as bleaching powder it has to be operated with a concentrated solution of known strength which gradually gets diluted within preset limit The results obtained on the laboratory model and prototype are quite satisfactory. The doser ensures reliability of chemical feed with reasonable accuracy and needs little skill for operation and maintenance. It is cheap and can be fabricated locally. The model can be further improved by providing a calibrated valve of good quality for regulating the dose.