Effect of Fine Sand Size in a Decentralized Household Drinking Water Purification Svstem

Slow sand filtration has been recognized as one of the effective methods of drinking water production in the rural areas of developing countries. In this study, a series of laboratory scale experiments was carried out to study the effects of fine sand size on water filter performance. Two kinds of fine sand, sand A (diameter: 0.5 to 1.l8mm) and sand B (diameter: < l.18mm), were employed during the experiments. The basic experimental unit was an acrylic rectangular tank, 60cm in length, 20cm in width and70 cm in height. Five compartments were arranged in away to maximize waterpurificatio n.Significantimp rovementwasmadeb yusingsandB(diam eter:< compared to using sand A (diameter: 0.5 to l.18mm). It was found that a water filter using sand B was capable of removing more than 85 o% suspended solids and 81% turbidity, which were remarkably higher than those by using sand A. Good removal efficiencies for color, iron, manganese, chemical oxygen demand (COD), bacteria and fecal coliform were achieved by using sand B in the unit. The removal for them was 82oh,9lo/o,93oh,85o/o,93o/o and 100% respectively. Further investigation on the removal efficiency at different stages of unit processes with sand B demonstrated that most of turbidity, color, iron, manganese and fecal coliform were effectively removed after sand bag screening and slow sand filtration. Average removal efficiency was 72oh, 640A, 79o , 78% and 93oh, respectively. Activated carbon fibre (ACF) played an important role for removing the remaining portion of the contaminants. The resulting removal efficiencies after ACF adsorption for turbidity, color, iron and manganese were 12oh,27.3o , 1306 andlTo/o respectively.