Research On Domestic Sewage With Multi-Grading Drop-Aeration Biofilm Process

It is an urgent task to harness the mountainous area's sewage when our country is facing serious water pollution. According to the condition of our country, low energy cost and simple flow wastewater treatment technological processes are needed badly in there. The paper does experimental and theoretical research for the sewage which is small discharge and has simple component.This paper is divided into two parts. The recent progress and its application in wastewater treatment by drop-aeration and biofilm reactor is reviewed in the first part. The adaptability of the treatment of low concentration sewage wastewater by drop-aeration biofilm process is also presented. In the second part, the treatment for sewage wastewater of a septic tank near environment department in HUST was studied in a drop-aeration biofilm process. After observation and experimentations, conclusions can be drawn by analyzing the data:The oxygen transfer efficiency by drop-aeration biofilm process was studied. The aperture of distributor and board was decided through the experimental test with tap water. There were 1.3mm,1.2mm respectively. The gap between foramens in board were 1cm.Through the sewage experimentation, we found that: the influence of velocity of flow was more important than water's height of drop in the condition without board,and the DO was increased by 0.81mg/L～2.54mg/L. DO was increase greatly when a board was used. With the height rise (0.3~1.2m) ,the DO was increased by 1.16mg/L～4.65mg/L.The factors which influence the biofilm tank was discussed. Conclusions can be drawn by the three tank's treatment results. Fibrous carrier was better than elastic filler, because it use less time for membrane's completion and stable effluent quality .Superior bacteria's addition can reduce the time of membrane's completion, and the rate of COD removal was 81.3%.The process can resist the loading fluctuation. The suitable concentration of DO was 2.5～4mg/L.The treatment of domestic sewage by the drop-aeration biofilm process was preliminarily investigated. The experiment results indicated that , under experimental condition with HRT for 3.6 hours, and the range of influent wastewater concentrations which were 103～162mg/L,78.16～116.57mg/L,36～66NTU for COD,NH4+-N,turbidity,respectively , the corresponding average removal rates were 64.79%,14.2%,84.81%。The average concentration of DO in the effluent wastewater was 3.9 mg/L.It is the first time to use drop-aeration biofilm process to treat low concentration sewage wastewater. It had the feather of simple flow,consumes relatively less energy,manage simply and automatically. etc. ,and the use of it on the treatment of sewage of mountainous regions will improve our country's river environment.The capacity of pollutants removal and the design of reactor is essential to be studied further. The techniques for low concentration sewage wastewater should be developed.