Study on Purification Effect and Long-Term Management of Bio-Ecological Combined Process for Rural Domestic Sewage
Compared with urban areas,rural domestic sewage discharge is scattered,basic treatment facilities are weak,and the management and maintenance are difficult.Therefore,in this study,the combined process of"anaerobic tank+biological filter+subsurface flow constructed wetland(referred to as"artificial wet-land")+oxidation pond"was used to investigate and analyze the removal characteristics of each treatment u-nit of the combined process on various pollutants in rural areas of Guilin,Guangxi.The results showed that the biological filter had the best removal effect on Chemical Oxygen Demand(COD)and Ammonia Nitrogen(NH3-N)in the combined process.The removal contribution rates were 75.36%and 66.46%in summer,and 67.96%and 57.13%in winter,respectively.The artificial wetland had the highest contribution rates to the removal of Total Nitrogen(TN)and Total Phosphorus(TP),with removal contribution rates of 65.08%and 63.97%in summer and 53.15%and 62.87%in winter,respectively.Moreover,regardless of whether it was summer or winter,the reed mixed canna wetland and the calamus mixed iris wetland had good removal effects on COD,TN,NH3-N and TP,and their effluent concentrations both could meet the first level B emis-sion standard.As the final treatment unit,the oxidation pond deeply removed pollutants in various ecological purification functional areas.Among them,the aquatic plant area had the highest average removal rate for TN,TP,and NH3-N,while the aquatic animal area had obvious advantages in COD removal.The average ef-fluent concentration of the oxidation pond in summer and winter could reach the first level A emission stand-ard stably.In addition,in view of the phenomenon that the removal rate of pollutants in rural sewage facili-ties decreased with the increase of operating years,long-term management suggestions for strengthening anti-clogging and timely harvesting of plant animals in each processing unit of the combined process were proposed to provide reference for ensuring the long-term pollution control effect of sewage treatment facili-ties.
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