Experimental Study On The Treatment Of Rural Domestic Sewage By Improved Constructed Wetland

As of 2019,the centralized treatment rate of domestic sewage in Chinese organized townships was only 12.27%.Most of the rural domestic sewage is directly discharged into the receiving water body,which has a serious impact on the ecological environment.Because the rural domestic sewage has the characteristics of source dispersing and great variation of water quantity and quality,it is not advisable to adopt the technology of urban sewage treatment directly.Therefore,in combination with the actual situation of rural economy and population,adopting decentralized sewage treatment facilities that are easy to manage,low cost and stable in operation will have broad application prospects in rural areas.The traditional constructed wetland system to treat domestic sewage has the characteristics of low investment and simple operation and maintenance,which is suitable for rural areas in my country,but it has problems such as poor hydraulic performance,low treatment efficiency,and easy blockage.To this end,the thesis conducts an improvement study on the basis of the traditional constructed wetland system,adopts four types of water in and out of the waveform upper and lower folded plate subsurface flow constructed wetland system to conduct indoor tests on rural domestic sewage treatment,and based on the results of the experimental research,preliminary analysis of the system to deal with rural life Degradation law of sewage.The following conclusions are drawn:1.The system started up after 35 days of trial operation.The removal effects of the four indicators of effluent COD_Cr,total phosphorus,ammonia nitrogen and total nitrogen were all relatively stable,and the removal rates reached 61.19%,69.74%,43.08%,and44.15%respectively.2.Three hydraulic loads and four water inlet and outlet position tests were carried out.The results showed that:the hydraulic load was 0.1 m/d,and the COD_Cr,total phosphorus,ammonia nitrogen and total nitrogen of the effluent reached the first level of the Pollutant Discharge Standard for Urban Sewage Treatment Plants.Level standard,and the treatment effect of the lower water inlet-upper water outlet conditions is better.Their average removal rates are:67.66%,67.93%,43.82%,42.78%,respectively.3.Using reflux operation to improve the optimal basic working conditions,12 sets of reflux operation tests were carried out.The results of the reflux test showed that the COD_Cr,total phosphorus,ammonia nitrogen and total nitrogen indicators of the effluent of the reflux test decreased compared with those before the reflux,and the ammonia nitrogen index decreased.The most obvious;the comprehensive treatment effect is better under the condition of 0.5 d of collected water for reflux operation;the average removal rate of COD_Cr,total phosphorus,ammonia nitrogen and total nitrogen are 71.74%,70.20%,56.04%,45.67%,respectively.4.The intermittent operation mode with an interval of 0.5 d was compared with the reflux operation,and 6 groups of intermittent operation tests were conducted.The results showed that the average removal rates of COD_Cr,total phosphorus,ammonia nitrogen and total nitrogen were 68.97%,73.12%,60.15%and 39.58%,respectively.The removal effect of ammonia nitrogen by intermittent operation is the best,but the removal effect of total nitrogen is decreased.