AWWA JAW71201

Slow sand filtration, a single-step complete water purification system for low-turbidity waters, is easy to operate and maintain, and therefore suitable in rural areas that lack skilled personnel. One question that has persisted in slow sand filtration design, particularly for tropical countries, is whether filters need to be covered. Studies were conducted to assess slow sand filtration performance under sun, shaded, and covered conditions. The presence of algae in the raw water filters marginally affected the length of filter run and did not affect the filtrate quality in turbidity under all modes of operation. No significant differences were observed in functioning of slow sand filters in terms of organic matter removal in the sun, shaded, or covered filters, and the total throughput of all the filters was comparable. These results suggest that slow sand filtration systems can be designed without a roof in tropical countries, thus reducing construction costs. Includes 14 references, tables, figures.