Research On Groundwater Vulnerability Experiment Of Reclaimed Wastewater District And Irrigation Allocation

The objective of ths study is to ascertain the transport and change of main pllutants in the typical vadose zone of Beijing plain based on groundwater investigation, field experiment. The indexs and weight of DRASTIC model is improved by quatifying the relation of human activities and grounderwater pollution, and the allocation map of grounderwater vulnerability and feasible allocation map of reclaimed wastewater irrigation in Beijing plain is drawn out.The time-spatical changes of groundwater quality in the southeast of Beijing plain is determined by carbonate balance, oxidation and deoxdation, concentration, etc.. The groundwater quality has improved in recent years. Reclaimed wastewater irrigation has not negative influence on groundwater from the investigation. Nitrite, nitrogen, ammonia, chloride, potassium permanganate and hardness are the six parameters signifantly affected by human activities.There are no signifance changes of heavy metals and PAHs in vadose profile under treatment 7 (simulation of 167-years reclaimed wastewater irrigation). The nitrogen is easier to transport compared to ammonia, and soil ammonia has high relation of clay particles content. The 12 meter and 18 meter of vadose thichness can remove 83% of total nitrogen, 99% of total phosphorus and 95% of PAHs. soil salt and sodicity is increased under treatment 7, which is still in the feasible range for irrigation(0≤SAR≤10). In the infiltration process of reclaimed wastewater from surface to groundwater (12 meter depth), the pH changes little, chloride increases 1.5%~16.1% and TDS increases 21%~30%, but there is no signifant difference in groundwater quality between treatment and control. There is no difference for salt changes between reclaimed wastewater and other water sources. The PAHs content is close to environmental background value, the pollutant is originated from a mixture of burning of natural gas and gasoline and coal combustion. Nap, Phe, Fla, Pyr is easier to transport compared to others. The typical vadose has low vulnerability.The relation between land use, water table decrese and groundwater pollution and the weight have been ascertained to improve DRASTIC model, the DRASILE model based on human activities has been established to research the feasibility of Beijing plain of reclaimed wastewater irrigation, the threshold to classify groundwater vulnerability for reclaimed wastewater irrigation is ascertained, Beijing plain bas been divided into priority area, feasible area and forbidden area for reclaimed wastewater irrigation with the area of 116 thousand hm2, 48 thousand hm2 and 15.8 thousand hm2 respectively.