Study On Urban Domestic Sewage Treatment With UASB Reactor At Normal Temperature

In recent years,the discharge of urban domestic sewage is increasing,but the capacity of urban sewage treatment is still slowly growing because of the constraints of technology and funds.In China,many large-scale sewage treatment plants have been built in large and medium-sized cities,while there is not enough capital and operational management personnel to build and run the complex aerobic sewage treatment plants in small town.Compared with the biological aerobic treatment,the anaerobic biological treatment has the advantages of less energy consumption,flexible structure,high load and less sludge.Especially,the upper flow anaerobic sludge bed?UASB,Up-flow Anaerobic Sludge Bed/Blanket?has the characteristics of simple structure and easy operation and management,which makes it possible to replace the traditional aerobic biological treatment being of advantage to solve the difficulties encountered in the wastewater treatment at the present stage.In this paper,the start-up and operation of the UASB reactor is the main object.The reactor can start quickly and have good treatment effect on the organic matter by providing the appropriate proportion of C,N and P,a suitable amount of trace elements,suitable p H,temperature and other external environment so that.The results showed that the UASB reactor could successfully start on the ninetieth day when the constant temperature was 35?and the influent COD_Crr concentration was 300mg/L,and the removal rate of COD_Crr was over 80%at HRT of 4h.After operating,large granular black granular sludge could be formed and 73.64%of the sludge size was larger than 0.25mm in the end.The reactor still has good treatment effect on COD_Crr when it is returned to normal temperature.After stable operation,when HRT is 3h and the temperature is 16²1.1?,the removal rate of COD_Crr is between 86.35%and 94.60%,the average removal rate is 91.05%,and the COD_Crr value of the effluent is lower than 43mg/L.The max biogas production rate of the system is 0.144L/g COD at the HRT of 8h,and the biogas can be recovered to reduce energy consumption.This paper also investigated the ability of the reactor to treat municipal sewage at normal temperature.The results showed that the effluent of the reactor could reach a good water quality during the adaptation period of 15 days in a stable environment.When the reactor HRT is ranging from 12h to 4h,the effluent concentration of COD_Crr is below 50mg/L meeting the first class A standard of the Discharge standard of pollutants for municipal wastewater treatment plant?GB 18918-2002?.After resuming normal load,the effluent can be recovered quickly and the stability of the system is high.The reactor also has good treatment effect on suspended solid?SS?,and the average effluent SS is3.89mg/L.However,the removal efficiency of nitrogen and phosphorus is not good,and the effluent cannot meet the Discharge standard of pollutants for municipal wastewater treatment plant.It is necessary to remove nitrogen and phosphorus with other treatments if UASB reactor is used to treat municipal sewage.