Experimental Research on Constructed Rapid Infiltration System Treating Wastewater of Regenerated-Paper Making

Constructed rapid infiltration system ( CRI ) is simulated through two groups of 3 soil columns with the height of 30 cm, 55 cm and 80 cm respectively. After pretreatment, the mixed wastewater of regenerated-paper making is put into the six soil columns. There are 16 kinds of hydraulic loading cycles made of 4 kinds of flooding-drying ratios (1:6, 1:4, 1:2, 1:1) and 4 kinds of flooding time (4 h, 8 h, 12 h, 16 h). As a result, the systems adsorb ions periodically, adsorption is mild while release is rapid, and the periods of adsorption and release are about 40 hours, respectively. The removal of COD mainly depends on aerobic biodegradation in the aerobic-anaerobic alternate zone. The COD removal of unit height is more because of better reoxygenation effect when the soil column is shorter. Blocking mainly exists in the shallow surface of the system.