An Experimental Study on the Clogging of Sand Filter in a Model Filtration-Pond

Abstract : A pilot-scale sand-box experiment was performed in order to investigate the effect of cross-flow velocity on the clogging of the filter sand in a model filtration pond. The clogging phenomenon was observed during the operation with the cross-flow varied in stages in a range of 0~40 cm/sec, and the experimental result was analyzed using a numerical code. Results showed that the cross- flow velocity in this range had no influence on the development of clogging and that clogging occurred mostly on the filter-surface. It was found that while the production rate decreased from 5 m 3 /m 2 -day to 3 m 3 /m 2 -day the clogging coefficient of the top 50 cm layer increased up to about 30,000 sec, which corresponded to 87% of the clogging coefficient of the total 2.4 m layer. Of the clogging coefficient of the top 50 cm layer, surface clogging constituted 90% while the other 10% was intermediate clogging. It was also found that the surface clogging increased while the intermediate clogging remained constant as the operation continued, and that filtrate turbidity along the filtration depth remained constant in spite of the increase in clogging.