REMOVAL OF HEPATITIS-A VIRUS (HAV), POLIOVIRUS AND MS2 COLIPHAGE BY COAGULATION AND HIGH-RATE FILTRATION

Filtration is considered a mandatory operation unit for the production of pathogen free drinking water from surface sources. This study was undertaken to determine the removal efficiency of enteric pathogenic v iruses (hepatitis A virus and poliovirus) by high rate filtration and to determine the suitability of F+bacteriophages as index for the remo val of these pathogens. Ajar test was used to determine the optimal fl occulation dose to be used in the high rate filtration experiments. At an alum concentration of 30 mg/l, the greatest reduction was observed for HAV (88.4%) as compared with poliovirus 1 (47%) and turbidity (61 %). Addition of 1 mg/l cationic polyelectrolyte improved the reduction of HAV to 98.3% by flocculation, while the removal of polio 1 and tur bidity was not improved, The presence of humic acid at a concentration of 15.3 mg/l interfered with flocculation performance of HAV and turb idity, while the addition of the cationic polyelectrolyte reduced the interference appreciably. High rate filtration (20 m/hr) using a 100 c m long sand column, resulted in reduction of 99%, 93% and 80% of turbi dity, MS2 and poliovirus 1, respectively. Addition of polyelectrolyte enhanced the removal of viruses and turbidity. In the presence of humi c acid no virus removal was observed by high rate filtration, whereas turbidity removal was unaffected. The removal of MS2 was similar to th at of HAV rather than poliovirus 1. High rate filtration was found eff icient for the removal of pathogenic viruses and turbidity from surfac e water. Under all conditions tested the removal of turbidity was grea ter than that of viruses.