CLOGONG OF POROUS MEDIA BY FINE SEDIMENTS

Abstract

Groundwater is an important source of drinking water. Riverbank Filtration (RBF) system is one of the most widely used system across the world for water supply purposes. In this system, filtration wells are located at some specified distance from the bank of river. The earth portion available between bank of river and the well acts as a filter which purifies the water by reducing bacterial as well as suspended impurities. Clogging of porous media at the RBF sites is one of the major problems faced in RBF system. The hydraulic conductivity of the porous media between river bank and well goes on reducing with time as the suspended sediments which enter into the media get accumulated inside the media adding to the resistance to flow offered by the media. Hence it becomes necessary to study the mechanisms of clogging of porous media. The clogging phenomenon is governed by many factors viz. initial hydraulic conductivity, flow velocity, suspended load concentration, grain size of the filter media, and concentration and grain size of the suspended load. This study is directed towards learning the impact of concentration of suspended load, initial hydraulic conductivity and flow rate over the reduction in conductivity for a selected grain size of fines and the filter media. A laboratory model is set and experiments are conducted to record the change in conductivity, by varying the suspended load concentration and flow velocity for different grain sizes of the soil sample, with time.