Pilot Study On Treatment Of Rural Domestic Sewage By A/O Biological Filter

In recent years,the disorderly discharge of rural domestic sewage has led to more serious water environmental pollution in rural areas.Although the state has continuously introduced relevant policies to promote the development of rural domestic sewage treatment,compared with urban areas,the level of rural domestic sewage treatment is still low.Although some rural domestic sewage treatment technologies at home and abroad have achieved good results,they are difficult to be popularized and applied due to poor economic conditions and lack of management personnel in rural areas.According to the characteristics of rural areas,this paper developed a set of biological treatment process based on anaerobic aerobic(A/O)process and biological filter as the aerobic treatment unit.The overall process energy consumption equipment only has one sewage lift pump,which is convenient for operation and management and suitable for popularization and application in rural areas.This experiment studied the operation effect of the process,focused on the removal effect and influencing factors of pollutants by biological filter unit,and established the dynamic model of biological filter.The main results are as follows:The experimental results show that the enhanced aeration mode of ventilation and water drop can keep the dissolved oxygen concentration in the effluent of the filter at about 5.6mg/L.COD volume load has a certain influence on the treatment performance of biological filter.With the increase of COD volume load,the treatment effect of biological filter is reduced.The volume load of ammonia nitrogen has a great influence on the nitrification performance of biological filter.With the increase of ammonia nitrogen volume load,the removal rate of ammonia nitrogen decreases and the nitrification performance becomes worse.The COD removal rate and ammonia nitrogen removal rate of the biofilter will decrease with the increase of hydraulic load.Under the operating conditions of water temperature 13～20℃and hydraulic load 3.84m~3/(m~2·d),the average removal rates of COD,ammonia nitrogen and total nitrogen were80.1%,77.60%and 57.98%,respectively.The average effluent concentrations were 61.5mg/L,5.9mg/L and 13.0mg/L,respectively.The concentrations of ammonia nitrogen and total nitrogen could reach the first-level standard of Discharge Standard of Water Pollutants for Rural Domestic Sewage Treatment Facilities(DB41/1820-2019)in Henan Province,and the COD concentration could reach the second-level standard,which was very close to the first-level standard.According to the experimental data,the pollutant degradation model of biological filter is established,which is the relationship between the concentration of organic matter and ammonia nitrogen along the filter and the filter height.It can be used to approximate estimate the pollutant concentration along the filter and determine the appropriate filter height.It provides a theoretical basis for the popularization and application of the process in the future,and has great practical value.