The Simulation Study Of The Land Treatment Process Of Domestic Wastewater

With the regard to the problem of the domestic wastewater land treatment at the discharge area in northeast of BaiCheng City, I take the soil column experiment to simulate the domestic wastewater land treatment system in laboratory at the basic of the local soil sample investigation and groundwater quality monitoring at discharge area. I studied transport pattern about organic material and eutrophication component (Phosphorus) of domestic wastewater in the vadose zone. Through the simulation experiment, I take the discharge area to establish the hydrogeology concept model for the fist time, and then gradually take theoretical research. With the help of the hydrogeology concept model, I fist exactly simulated the polluting process which polluted matters of domestic wastewater pass through the vadose zone and reach the underwater environment, whereafter predicted the polluted plume of the discharge area. In the final, I put forward some reasonable suggestions, such as improving domestic wastewater soil-filter treatment efficiency and groundwater environment. The research results are significant for alleviating the status of polluted vadose zone and protecting the local ecological environment.There are some major research results in my dissertation: (1) the process that contaminated material pass through vadose zone can be divided into three phases: interception phase, alternating absorption phase, dissolution and deposition phase. In the soil-filter system, the colloidal particles and impurities of domestic wastewater can be intercepted by surface soil. Therefore, the interception reduced the surface soil's permeability, so that percolation velocity of substratum decreased and also the contamination's migration velocity declined. The greater retardation capability that polluted pattern passed through soil medium, the longer transition zone that contamination of domestic wastewater transferred in soil medium. The majority of contamination was intercepted by surface soil. the contamination's transference is greatly influenced by infiltrated water's velocity in soil medium. The capability that sand retarded contamination of domestic wastewater arrayed from strong to weak with silver sand, original sand and rough sand. With the increase of the sand medium's depth, the capability which sand retarded contamination's movement is gradually strengthened. (2) The soil medium of discharge area had been polluted, and the polluted degree is responsible for the capability which contamination be retarded by soil medium. However, If surface soil medium was demolished, organic pollution matters permeated vadose zone and reached groundwater aquifer by 9 days, While phosphorus did that by 108 days. In the case of continuous rainfall, the polluted saturation interface gradually moved downward, the velocity is positively related to the infiltration capability of soil medium. The monitoring result declared that groundwater was seriously polluted, and with the passage of time, the scope of pollution has been gradually expanding. Whereas pollution halo mainly spread southeast from the prediction chart. The provision process is slow in the north of the discharge drain but faster in the southeast of the sewage outfall. The contamination of groundwater is in higher level with the influence of paddy fields irrigation near ZhenLai city.