Modifications of a simple clogging and back-washing efficiency model for arsenic filters

Abstract

After continuous use of any filtration device, clogging of the filter media becomes apparent, which eventually causes poor performance of the filtration process. Back-washing is a common technique that is used for the recovery of the filtration capacity of clogged filter media. This paper presents the development of a simple clogging and back-washing efficiency model for a special filter medium. The ‘third-generation IHE family filter’ was developed by the Unesco-IHE Institute for Water Education and is widely used for treating arsenic-contaminated water in many countries, including Bangladesh. Several field tests were conducted at three different sites in Bangladesh having different qualities of influent water. The model coefficients developed were derived using the collected data on flow measurements through the device during successive clogging and back-washing periods of up to 4 months. The developed model with the selected model coefficients can simulate field measurements on flow retardation and recovery with good accuracy. Eventually, selected model coefficients (clogging factors) for the three sites were correlated with the respective ammonium and iron contents in the influent water. It was found that the clogging factor linearly varies with the ammonium and iron contents of the inflow water.