Abstract
A modified jar-test method, comprising a rapid mixing process with a time of 5 minutes and a filtration process with glass fiber filters or membrane filters, was used to evaluate the quality of filtered water in direct sand filtration of surface water with low turbidity and relatively high color content. The results showed that with the application of this method, the time needed for evaluating the quality of filtered water in direct sand filtration was greatly shortened (of several minutes), compared to about one hour with the conventional jar-test method. Furthermore, the estimation of the efficiency of several different types of coagulants in direct sand filtration by the modified jar-test method made clear that PACI (Poly-aluminum chloride) was more effective than alum, and the cationic polymer performed much better than either the nonionic or the anionic polymer.
