Prediction of Temporal Changes of Head Loss in Sand Filter

Abstract

Granular media including rapid gravity sand filters are used in water and wastewater treatments. When sand filters are clogged due to deposits of particles and particul-bound pollutants, it will lead to head loss and under this situation it is necessary to perform filter backwashing. Prediction of sand filter head loss is the major focus of this study. To meet the primary ojective of this study, a single-layer rapid gravity filter with sandy media was tested with inflow water containing different concentrations of lead (Pb). The amount of deposited sediments and the resulting head loss were simulated in the filter media by combination of Karman-Cozeny, Rose and Gregory equations under different discharges. The maximum time to reach the various amounts of head loss was obtained when the inflow lead concentration was lowest (25 ppm) and the surface filter leading was the highest (6.22 m3/m2/hr). The highest lead removal efficiency (92%) was obtained when the input lead concentration was 25 ppm and filter surface loading was 3.11m3/m2/hr. Comparing the specific head loss under different operating condition it has been shown that the time difference is less under lower head losses of 5 and 7 centimeters. In addition, the slopes of filtration discharge under similar operating condition showed to be steeper verifying a higher filtration performance when the concentration of input lead and filter surface loading was lower.