PURIFICATION OF AERATED GROUND-WATER USING RAPID SAND FILTERS

Abstract

Most of arid and rural areas in Egypt depend on groundwater as a main source of drinking water. The main problem in this source of water is the appearance of iron salts which affects the water potability. Several studies had been applied to solve the iron problem in water. Aeration is considered the best and cheapest way to remove iron salts from groundwater. Aeration depends on oxidation of soluble iron (II) to the insoluble iron (III) form which it can be removed by using filtration following sedimentation or filtration only depending on iron concentration on the raw water. This study is conducted to investigate the success of a proposed technique using aeration followed by filtration without chemical additions for iron removal. The effect of different filtration of sand depths, filtration rates and raw iron concentrations on the efficiency of removal of iron and turbidity are considered. The research is applied on tap water with different values of iron concentrations. The predetermined values of iron concentrations were 1.5, 2, and 3.33 mg/l which chosen to give different values of turbidity after aeration (13, 20, and 30 NTU respectively) and to cover the range of the average values (about 1 to 5 mg/l) which appear in the most of water wells in Upper Egypt. Results indicated that, for all values of iron concentrations and effluent turbidity less than 1 NTU, the economical sand depth is 40 cm when the influent turbidity 70 cm when the influent turbidity < 30 NTU and filtration rate in the rang from 80 to 200 m 3 /m 2 / day.