Effect of Media Intermixing on Dual Media Filtration

Five practical suspensions were filtered through dual media filters with and without intermixing. The results show that: (1) Interfacial intermixing does not in itself affect filter performance as measured by both headloss development and effluent quality; (2) mixed interface filter media produced better filtrate quality than did the sharp interface filter media for all suspensions filtered due to substantially finer sand in the mixed interface media; (3) mixed interface filter media produced higher headlosses than the sharp interface filter media for all suspensions due to greater suspended solids removal; (4) intermixing at the interface of dual media filters is an unavoidable phenomenon that results when current media material are used and the sizes are selected to achieve coarse to fine filter media in the direction of flow; and (5) a modest amount of interfacial intermixing is desirable in dual and multimedia filters from the standpoint of filtrate quality.