Soil Aeration Zone And Constructed Wetland River Pollution Reduction Technology Of Water Source Area

Aiming at the terrain characteristics and economic development of South-to-north Water Diversion Project water source area, the situation of large gap between urban sewage treatment plant of tail water and the target water quality, and a lot of untreated water which was out of sewage treatment plants pipe network area being directly discharged into the river, water quality protection of water source area was confronted with a serious threat. This paper mainly studied on the low investment, low energy consumption, low processing cost, highly efficiency Soil Aeration Zone and Constructed Wetland technology which can intercept and reduction of point source and non-point source pollution, including:Soil Aeration zone-Filler Buffer Barrier technology, Horizontal Subsurface Flow Constructed Wetlands Technology and Free Water Surface Flow Constructed Wetland technology.On small scale test, using soil and sand as horizontal subsurface flow constructed wetland fillers, to treat urban sewage treatment plant effluent. The results show that, the COD, NH3-N, TN and TP of constructed wetland effluent has a very good removal effect, the average removal rates were73.4%、94.6%、70.7%and94.4%. The secretion of oxygen and absorption of plant roots in subsurface flow constructed wetlands, with little effect on the removal of low concentration of COD, significantly promoting the ammonia removal, certain extent the removal of TN, and limited influent of TP removal. Transplanting aquatic plants and doing experiments, screened three species which is most efficiency on TN removal are Acorus calamus L, Kalimeris indica L, Acorus tatarinowii, and three species which is most efficiency on TP removal are Kalimeris indica L, Hemerocallis fulva L, Acorus calamus L.The experiment of treating the country wastewater in pilot-scale demonstration project shows that, the COD, ammonia nitrogen, TN and TP average removal rates of Soil-aeration zone-filler-type buffer barrier were78.2%,77.9%,60.7%and84.4%. When the HRT is20hours, the COD, ammonia nitrogen, TN and TP average removal rates of horizontal subsurface flow wetland were66.7%,68.8%,48.1%and48.4%. When the HRT is10hours, the COD, ammonia nitrogen, TN and TP average removal rates of horizontal subsurface flow wetland were63.8%、65.9%、43.6%and39.9%. When the HRT is27hours, the COD, ammonia nitrogen, TN and TP average removal rates of free water surface flow constructed wetland were39.2%、50.1%、32.1%and42%. When the HRT is13.5hours, the COD, ammonia nitrogen, TN and TP average removal rates of free water surface flow constructed wetland were38.8%、42.3%、28.5%and36.3%. Adding wood chips into the soil-aeration zone-filler-type buffer barrier as sustained release carbon, plays a significant role of improving TN the removal rate and denitrification. By doing comparison parallel experiments, the TN and TP removal effect of horizontal subsurface flow constructed wetland is better when the HRT is longer. On the other hand, the COD and ammonia nitrogen removal overall efficiency of horizontal subsurface flow constructed wetland is better when the HRT is shorter. When the HRT is longer, the ammonia nitrogen and TP of free water surface flow constructed wetland removal efficiency has improved greatly, meanwhile, the improving of COD and TN removal efficiency is not so much. And the three processes were not strong on resistance to TN and TP shock loading.The study on pollution reduction combination technology of Soil Aeration Zone and Constructed Wetland, not only provide low-cost, high-efficiency wastewater treatment combination process, but also offer technical support to meet the quality requirements of South-to-north Water Diversion Project water source area. Therefore, it is great significance to protecting water quality of water source area.