| The direct discharge of rural domestic sewage in China has a great impact on the rural water environment.According to the characteristics of the quality and quantity of rural domestic sewage in Sichuan,this paper designs and conducts a multi soil layering system at the laboratory level to simulate the treatment of rural domestic sewage.In the experimental study,through the combined experiments under various conditions such as different water inflow methods,different hydraulic loads,different initial p H,different initial DO concentrations,different soil module layer structures,and different soil module layer fillers,the optimal operating parameters,the optimal soil module layer structure and the optimal soil module layer filling of the filter system were obtained,and the in-depth mechanism analysis of the microbial community in the system was carried out,providing some reference for the practical application of multi soil layering system to purify rural domestic sewage.The main conclusions are as follows:(1)In the continuous water intake stage,the organic matter removal rate of the straw-based multi-stage soil infiltration system was low,the removal rate of chemical oxygen demand was 0 in 60% of the operating time,and the removal rates of ammonia nitrogen,total nitrogen and total phosphorus were stable,83.33 The effluent concentration of % operating time meets the third-level standard limit requirements of "Water Pollutant Discharge Standard for Rural Domestic Sewage Treatment Facilities"(DB51/ 2626-2019)(total nitrogen meets the first-level standard limit requirements),and it is determined that the hydraulic load The optimum operating parameters were 300L/(m2·d),initial p H of6.8-7.2,and initial DO concentration of 4.5-5.5mg/L.(2)Further experiments under the conditions of intermittent water inflow and optimal operating parameters showed that the organic matter removal rate of the straw-based multi-stage soil infiltration system was significantly improved,and the treatment effect of the U-shaped soil module layer multi-stage soil infiltration system was better.excellent.The chemical oxygen demand removal rate of the U-shaped soil module layer multi-stage soil infiltration system remained above 40% during 86.67% of the operation time,the removal rate of all ammonia nitrogen during the operation period was maintained above 90%,and the total nitrogen removal rate was maintained at 87%.% above,the total phosphorus removal rate is maintained at above 94%,and the effluent ammonia nitrogen,total nitrogen and total phosphorus concentrations all meet the three-level limit limits of the "Water Pollutant Discharge Standards for Rural Domestic Sewage Treatment Facilities"(DB51/2626-2019).(Total nitrogen meets the first-level standard limit).(3)Under the condition of intermittent water inflow,the effect of fillers on the treatment effect of U-shaped soil infiltration layer multi-stage soil infiltration system was compared.The results showed that the removal effect of biochar filler multi-stage soil infiltration system was significantly better than that of straw filler.,the average removal rates of chemical oxygen demand,ammonia nitrogen,total nitrogen and total phosphorus of the biochar-filled multi-stage soil infiltration system are 83.43%,94.97%,94.77% and96.97%,respectively,and the effluent concentration meets the requirements of "Water for Rural Domestic Sewage Treatment Facilities".Pollutant Emission Standard(DB51/2626-2019)the first-level standard limit requirements(chemical oxygen demand meets the third-level standard limit),the results of quantitative PCR and high-throughput sequencing show that the biochar filler multi-level soil infiltration The microbial abundance of the system is better.At the phylum level,the two systems have similar dominant flora.At the genus level,the abundance and diversity of microorganisms related to pollutant removal in the biochar-filled multi-stage soil infiltration system are stronger.,which makes its removal effect better. |
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