Laboratory simulation of the effect of wastewater recharge on the transfer of phosphate contamination to aquifer (Case study: Arak Plain)

In this research, Gavkhaneh area located in the north of Arak was selected to investigate the effect of wastewater recharge on aquifer contamination. For this purpose, layers in the unsaturated zone of the region were simulated to the surface of the ground using cylindrical columns made of PVC with a diameter of 25 cm. Three columns of soil were considered at 2, 2 and 1 meters respectively.Also, to study the effect of zeolite filter, the first column of soil was considered in two treatments of without Zeolite and with Zeolite. For implementation of artificial recharge with wastewater, two strategies of permanent submerging for 20 days and submerging-dryness for 40 days (one day of submerging and one day of drying) were used. The amount of phosphate for the input and output of wastewater was measured. The results show a high percentage of removal of phosphate in soil layers up to 75%. Also, better removal of phosphate in the second layer with heavier soil was done than the other two layers. The application of zeolite also has no effect on the reduction of phosphate levels. Finally, studies have shown that the submerging-dryness strategy is more effective than permanent submerging to remove phosphate. So that final absorption increased in the first layer up to 15% and in the third layer up to 16% than to permanent submerging. But in the second layer with a heavier texture, no change in final absorption was achieved.