| The right and large-scale centralized sewage disposal establishments have been constituted in the course of city plan being executed, that haves made the city sewage be treated, but the decentralized wastewater does not be treated out of the area is still not be controlled effectively, and the discharge amount is increasing gradually year by year. The land treatment included in the nature disposal system is an effective disposal technology that is fit for the decentralized wastewater, as well as needs fewer investment and lower energy consumption ,compared with the traditional activated sludge process. In this thesis, the subsurface wastewater inflitration that a technology has been rapidly developed and wildly applied in the land treatment was discussed, through date analysed and synthesized some features of the traditional submerged filter and a new submerged filter structure and tester that based on the betterment study of some subsurface wastewater inflitration was built up. Then some researches and experiments were carried out for sewage treatment and the removal mechanism about some contaminations was superficial analysed in this new system .The major results are as follows:(1) examined the startup time of subsurface wastewater inflitration, included compared experiment between two inflow modes , the results indicated ,when the COD of sewage is between 250-400mg/L, and NH4+-N is between 70-100mg/L, the new system startup time is 18d in the mode of interim inflow. When the hydraulic residence time is 6h, the COD removal efficiency can reach about 80% after the system is started up.(2) The study to the hydraulic loading of new system indicated that the removal efficiency of COD and NH4+-N will decrease by increasing of system hydraulic loading, and below the 10L per time , the removal efficiency can be up to 60%;when the COD contamination loading is between 300-400mg/L, COD removal efficiency can reach 75% and higher, and when the NH4+-N contamination loading is below 50mg/L, its removal efficiency can reach 80% and higher.(3) the results of the diffluence experiment show that diffluence have few effect to theremoval rate about NH4+-N, but a litte effect to the removal rate about TN ,as well as when the diffluence ratio is 1:3 ( under layer inflow amount : upper layer inflow amount), the removal efficiency of TN is 52.48% and better than the other.(4) The forced aeration has little contribution to increasing the removal efficiency of COD and TP on the condition of aeration flux below 640L per time, the removal efficiency of TN get a better result on the condition of aeration flux between 180L-480L per time.(5) The plant can not grow normally by reason of deficient sunshine in the whole experiment. From the data analyzed to plants grown on the system, that plants' contribution to the pollution removal rate can be confirmed below 10%, and its ability is limited.(6) the results that this new system run by using optimized parameters indicated that contaminations' removal effect is close on hydraulic residence time between 10-15h and more than 35h. Under this condition , removal efficiency of NH4+-N and TP can reach 90% and higher, and the removal efficiency of COD can reach 75% and higher,as well as the TN can reach 45% and higher.(7) The conclusion about the removal route of COD shows that the function of filtration is the major contribution to removal rate of COD, the next is the function of microbe's decompose, and the last one is plant's assimilation; the result from the analysis to removal route of N indicated that the function of removal to NH4+-N depends on soil's adsorption and system oxidation, and new system has a good nitration effect ,but has a bad denitrification effect, that lead a low removal efficiency of TN.The function of biologic assimilation has few contribution to removal for TN;in the betterment subsurface wastewater infiltration the removal of the TP mainly depends on soil's adsorption and chemical deposition, and the function of plant's assimilation is smaller. |
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