Study on iron removal from groundwater for potable water supply

Abstract

Excessive amount of iron content in groundwater creates a major problem in many regions for potable water supply. To characterize the iron problem in groundwater of Bangladesh with respect to depth and location, water quality data are collected from different organizations. Average iron contents in groundwater are represented on iron iso-concentration maps of four subdivided regions of Bangladesh. The subdivided regions are North-West(NW), North-East(NE), South- East(SE) and South-West(SW). Based on the available data, areas where iron content above 2 mg/L are identified as iron problem towns in those regions. To overcome this problem, recently four iron removal plant have been constructed in Hobiganj, Gopalganj, Serajganj and Chandpur. Two older plants are in operation at Faridpur and Chittagong. These plants have been designed to serve a fixed number of people and may require expansion in future to meet growing need for potable water. Detailed design principle with operation and maintenance problems of all existing plants were investigated and studied to develop an economic iron removal process. It is seen that working principles of four recently constructed plants are almost same and differ in minor ways from the two. The feasibility of constructing the proposed iron removal plant at Satkhira is studied by comparing the scheme with a potential alternative of transporting good quality grC:;undwater from a distance of 5 km. The capacity of the plant is determined to serve 83,853 persons at 550 ml/h with 19 hours supply per day. This will serve 45% town population in 2010. By cost analysis, it is ,seen that investment cost of transporting water from a 5 km distance by a single line of 350 mm PVC pipe is less than the same of two lines of 250 mm PVC pipe and three lines of 200 mmPVC pipe. It is also seen that the investment cost of water supply system when water is transported from a 5 km distance by 350 mm PVC pipe is less than the same of water supply system with IRP of capacity 550 ml/h. Operation and maintenance costs of water supply system with an IRP are also less than the same of water supply system when water transported from a 5 km distance. Based on study of aeration and filtration hydraulics, the scope of high filtration velocity use have been justified and finally, an attempt to design the proposed iron removal plant at Satkhira is made.