Development And Application Of Rural Domestic Sewage Treatment Equipment Based On Moving Bed-biological Filter

Rural living sewage treatment is one of the important contents of promoting the strategy of rural revitalization and the construction of ecological civilization.However,due to the limitations of natural,economic and management conditions,rural sewage network and treatment are difficult to construct,operation and maintenance funds are insufficient,and technical difficulties are high.Therefore,this study developed a new type of integrated treatment equipment for rural domestic sewage based on the photovoltaic direct drive mobile bed-biological filter treatment process.This study studied the removal effect of integrated equipment on COD,NH₃-N,TN and TP of sewage after stable operation through indoor simulation test and field pilot test,explored the influence of different influencing factors on the operation efficiency of integrated equipment,and evaluated its applicability,economy and ecology.The main research results are as follows:（1）The integrated processing equipment adopts the combination process of moving bed biofilm and biofilter,which can adapt to different loads and has strong adjustability without clogging phenomenon.The effective volume of the processing equipment is designed to be100 L,and the solar power supply set can ensure the normal operation in more than four consecutive rainy days.The integrated equipment covers a small area,the investment and operation cost is low,the sewage purification degree is high,and the recycling rate is high after treatment.（2）In the laboratory simulation test,the average influent concentrations of COD,NH₃-N,TN and TP are 144.68 mg·L^-1,13.95 mg·L^-1,17.09 mg·L^-1 and 1.76 mg·L^-1,respectively.The average pollutant concentration of effluent was 37.06 mg·L^-1,1.60 mg·L^-1,5.14 mg·L^-1,0.60mg·L^-1,and the average removal rate was 74.77%,88.68%,70.06%,66.04%,respectively.The water quality indexes were all in line with the first-level standard of"Discharge Standard of Water Pollutants for Rural Domestic Sewage Treatment and Disposal Facilities"（DB37/3693–2019）of Shandong Province.The average influent COD,NH₃-N,TN and TP concentrations are 294.07 mg·L^-1,28.29 mg·L^-1,31.61 mg·L^-1 and 3.64 mg·L^-1,respectively.The average pollutant concentration of effluent was 31.29 mg·L^-1,3.41 mg·L^-1,17.97 mg·L^-1,2.01 mg·L^-1,and the average removal rates were 89.31%,88.32%,43.21%and 41.81%,respectively.Except TP,Other pollutant indicators meet the first level of the above standards.The average removal rates of NH₃-N and TN decreased to 59.64%and 38.61%,respectively,after the C/N ratio（C/N）of high concentration rural domestic sewage was reduced from 10:1to 5:1.In the combined process,the average contribution rate of the moving bed biofilm process unit to the removal of COD,NH₃-N and TN is above 85%,and the average contribution rate of the biological filter process unit to the removal of TP is 45.60%.（3）In the field pilot test,the optimal process condition of the equipment is 2 L·min^-1aeration(dissolved oxygen content is between 3.0 and 4.0 mg·L^-1).The decrease of aeration（dissolved oxygen）results in the average removal rates of NH₃-N and TP decreased from86.66%and 74.05%to 55.91%and 55.98%,respectively.The increase of organic load contributed to denitrification,and the average TN removal rate increased from 24.91%to37.55%.In winter,the average removal rates of NH₃-N,TN and turbidity decreased from94.41%,49.39%and 98.80%to 57.32%,21.24%and 94.82%,respectively,indicating that low temperature inhibited nitrification and denitrification.（4）The integrated treatment equipment designed according to the characteristics of water quality,water quantity and discharge of rural domestic sewage is especially suitable for rural areas which are not easy to lay a large area of pipe network.The one-time investment of decentralized treatment mode of this equipment only accounts for 48.34%and 52.43%of that of pipe network and new sewage station and that of pipe network and new collection pool,and its operating cost within 30 years is only 16.41%and 29.47%of that of sewage station treatment mode and collection pool treatment mode.Compared with traditional sewage treatment in sewage treatment stations,the equipment can reduce CO₂ emissions by 1.31 kg per ton of water treated during operation.The application of the integrated treatment equipment in rural areas has good social,economic and environmental benefits.