Study On Groundwater Recharge With Reclaimed Municipal Wastewater And Health Risk Assessment

Groundwater recharge with reclaimed municipal wastewater disposed by tertiary treatment is an efficient approach to solve water shortage problems in China. In the process of artificial groundwater recharge with secondary effluent from wastewater treatment plant, the remove and transfer of the pollutant and the health risks caused by potentially health hazardous compands were the focus in this study.Three soil columns in series were used to simulate the recharge process in laboratory. Secondary effluent from wastewater treatment plant disposed by tertiary treatment was dripped into the column by peristaltic pump. The column was operated in a wet-dry cyclical pattern, nitrogen,phosphorus,heavy mentals and organic pollutant were discussed.NH₄⁺-N was adsorbed by topsoil, and then conversed to NO₃^--N by nitrobacteria under aerobic condition, NO₂^--N was removed by nitrobacteria too, and the nitrification of NH₄⁺-N and NO₂^--N occurred in the depth of 0.5m. NO₃^--N was removed through dinitrification. Different wet-dry cyclical pattern had a more pronounced effect to transformation of nitrogen. Heavy mentals and phosphorus had a less effect to groundwater in practical projects. Organic compand was the emphasis which must contralled during the process of artificial groundwater recharge. Results indicated the simulating soil column could remove organic matter effectively and steadily, the removal efficiency of TOCand BDOC5 were 50% and 94.33% during 1.5m recharging process. Removal of organic pollutant mainly occurred in the depth of 0～0.5m of soil layer and most organic pollutant was eliminated through biodegradation, the removal efficiency of TOC and BDOC5 in 0.5m effluent was 42% and 62.02%. DOC in the effluent from the column contained a mass of nonbiodegradable fraction. The refractory DOC concentration of secondary effluent after 5 days BDOC test was 6.4～7mg/L, higher then the mature column effluent which was 2～4mg/L because of different mechanism. Aerobic microorganism could utilize humus and aromatics to remove trace organic matter in the unsaturated zone, the average removal efficiency of UV-254 was 39.44%, and SUVA values increased with the increase of the soil...