Study On Sewage Treatment With Activated Sludge-biofilter Integrative Reactor

The aim of this experiment is to research the properties of activated sludge-biofilter integrative reactor to the municipal wastewater. To ascertain the optimum operation condition, DO and cycle duration of the biofilter and the different carbon course added into biofilter at different temperatures were studies in this treatise, especially nitrogen removal rate of the reactor.The process of activated sludge, in the forepart of the reactor, has the function of removal of organisms and suspended substances and nitrification. Under the condition of HRT=4.7h, MLSS=3000mg/L, SRT=15~20d, DO>2.0mg/L and the loading rate of 0.4gCOD/gMLSS-d, the average removal rate of SS, COD and NH3-N of activated sludge process was 67.6%, 76.5% and 88.3% respectively. It has a good efficiency of nitrification that the average concentration NO3~-N is increased from l.0mg/L of the influent to 35.8mg/L of the effluent. But the removal rate of TP is only about 15.1%.The nitrification rate is obviously increased as the temperature increases from 13 to 20 In dissolved oxygen (DO) single factor experiment, the biofilter operates under three DO levels of 0.3mg/L, Img/L and 2mg/L, and ascertain the optimum DO is 1.0mg/L. Under this level of DO, the average removal rate of SS, COD and NH3-N of the reactor was 92.0%, 87.0% and 85.0% respectively. The average removal rate of NO3--N was 32.1%, and TP was 29.0%.Under the temperature of 13 and 20, the experiments of adding different quantity of carbon course were conducted. The experiment showed that the effluent quality is increased at 20 compare to 13, the removal rate of SS, COD, NH3-N, NO3--N and TP is 91.7%, 82.5%, 84.8 %, 60.6% and 11.0% respectively, and the optimum quantity of carbon course was 121/h.The aeration/unaeration time, 2h/lh, 2h/2h and 3h/2h, was also studied. When aeration/unaeration time of 2h/lh, the effect of the reactor is almost without change and meet the code for wastewater discharge with saving energy 30%. Under this experiment condition, the removal rate of SS, COD, NH3-N, NO3--N and TP is 91.9%, 86.0%, 90.5%, 60.3% and 9.2% respectively in one cycle duration.According to the model of Eckenfelder, the dynamics model of degradation organisms of activated sludge-biofilter integrative reactor was deduced.The reactor of activated sludge-biofilter integrative has a high ability of removal oforganisms, suspended substances and nitrogen to municipal wastewater treatment. The advantages of the reactor is requiring a smaller land area, low investment, saving energy and convenient management. So it is a integrative reactor with high efficiency and low consumption and can be widely used in small town.