Filler improvement and purification effects of constructed rapid infiltration facility.

Purification effects of constructed rapid infiltration system with two main fillers (coarse sand or medium coarse sand) and different addition proportion (5%, 10%, or 15%) modifiers (sponge iron, blast furnace slag, or zeolite) on rainwater runoff were studied through filter column tests. A set of constructed rapid infiltration system test device was designed, which included 9 rainwater filter columns. The test results showed that the permeability of artificial fillers blended with modifiers could have the promotion with varying degrees. There were differences in the characteristics of the modifiers, so the artificial fillers blended with different modifiers had a significant difference for the purification effects on each pollutant. In view of the overall situations, the pollutant removal effects of artificial fillers with two or more modifiers had a smaller gap, and the reduction effects were good, ranging from 38.95 to 46.25% when the main filler is coarse sand and from 46.29 to 49.46% while main filler is medium coarse sand. It was worth noting that the artificial fillers blended with sponge iron showed a slight harden after prolonged used; however, it had little influence on the permeability and water purification effects.