Performance of Crushed Coconut Shell Dual Media Filter

Filtration accounts for a substantial portion of water treatment cost. The dual media filter, by operating at a higher filtration rate than the conventional rapid sand filter, can reduce the cost of filtration considerably. Use of the dual media filter in Kenya, however, is limited by lack of suitable material for use as coarse media. In this study, pilot plant filtration tests are carried out to investigate the performance of crushed coconut shell as coarse media in dual media filters. Filtration rate, size and relative depth of crushed coconut shell media are investigated. A dual media filter with equal depths of 0.42 and 1.20 mm effective size sand and crushed coconut shell media respectively is found to give the best performance. The filter was operated at 12m/h (2.4 times the filtration rate of the rapid sand filter) while maintaining the same effluent quality and length of filter runs as ordinarily obtained with rapid sand filters.