Pollutants Removal from First Flush by Filtration through Four Filter Media

The effect of pollutants removal from first flush by filtration through four filter media was investigated by measuring turbidity, SS, COD, TP and TN. The four filter media were selected from familiar and available materials, including slag, geotextile, nylon net and wiry net. Experiments were conducted in an elaborate channel with raw water obtained by mixing tap water with some sludge to simulate the quality of early rainwater runoff. Results showed that 30cm-thick slag was the most effective filter media, and its removal rates for turbidity, SS, COD, TN and TP was up to 89.2%, 77.0%, 18.4% ,6.4% and 13.5% respectively. As for pollutants removal rate, the order from high to low was 30cm-thick slag, 20cm-thick slag, 10cm-thick slag, geotextile, wiry net, nylon net and a combination of both wiry net with nylon net. The experiment about geotextile, which was applied extensively in construction field, showed that removal efficiencies for turbidity, SS and COD were 79.4%, 66.4% and 14.8% respectively. The geotextile was proved to be one type of excellent material for pollutants removal from first flush and could be used in storm drain inlet.