Experimental Study On The Treatment Of Urban Domestic Sewage By Compound Bacteria Intensified Biological Turntable-AAO Process

In recent years,with the development of new urbanization in China,the amount of urban sewage discharge is increasing,and water pollution has become an urgent ecological problem.However,the winter temperature in north China is relatively low,and the traditional Aao and oxidation ditch biological treatment processes are affected by the low temperature environment,as a result,the efficiency of biological treatment is low,the quality of effluent is unstable,and it is difficult to meet the discharge standard for some indexes in Sewage Treatment.Therefore,the traditional sewage treatment process can not meet the requirements of high water quality,adding microbial agent provides a new method to improve the traditional sewage treatment effect.However,many microbial agents are faced with the problems of weak impact resistance,easy loss and poor pollutant removal effect.In this paper,we choose Bacillus compound bacterial agent and combine the immobilized microorganism technology with the traditional process,which provides the theoretical basis and thinking for the practical application of the combined process.Aiming at the characteristics of low water temperature and low c/n ratio in winter,the AAO process enhanced by compound bacteria agent was constructed,the start-up time method,influencing factors,treatment efficiency of low temperature and low c/n municipal wastewater and the optimization strategy of stable operation are summarized.Under normal load condition,the process of bio-rotating disk-AAO was enhanced by compound bacteria agent,and the natural and artificial membrane forming methods were used to start the reticular bio-rotating disk.The experimental results show that after 16 days,the color of the biofilm on the disc is brown-black and the thickness is ≥0.2 mm.The removal rate of COD is about 86%,and the removal rate of NH4+-N is over 90%,biofilm formation in rotating biological contactor.On the 22nd day after the start-up of the process,the sludge concentration in the bioreactor and AAO process increased from 2546 mg/1 to 5008 mg/1,which satisfied the normal operation conditions of the process system.Therefore,the stable operation of the process takes about 22 days.The removal efficiency of pollutants in municipal wastewater was investigated by controlling single-factor variable method under normal loading after the mixed biofilm formation of sludge and microbial agent was completed in a reticulated rotating biological contactor.The results show that the removal efficiency of COD,NH4+-N,TN and TP is better when the rotating speed of the rotating biological disk is 6r/min,HRT is 12h,the reflux ratio of the mixed liquid is 200%and the sludge reflux ratio is 70%.The efficiency of the bio-rotating disk-AAO process enhanced by complex bacteria agent was analyzed to treat low temperature and low c/n ratio domestic wastewater,and the optimization strategy of stable operation was discussed.It was found that the process had little effect on the removal of pollutants at low temperature and had low temperature adaptability in a certain range,but the influent low c/n ratio had great effect on the removal of TN and TP in the effluent of the process.Therefore,in order to solve the problem of poor nitrogen and phosphorus removal efficiency under low c/n ratio,the operation stability optimization was studied,and the operation strategy of low c/n ratio municipal wastewater treatment was obtained:increasing sludge reflux ratio by 80%;The carbon-nitrogen ratio of 7:1 can meet the high standard of discharge by extending the sludge discharge period to 24 days,and the concentration of COD,NH4+-N and TP in the effluent of the bio-rotary table-AAO process enhanced by complex bacteria agent can meet the four water standards of surface standard,the concentration of TN in effluent reaches grade a standard.Through the study of this paper,it is shown that the immobilization of Bacillus complex bacteria on the network-shaped rotating biological tray combined with the traditional process has a good effect on the treatment of municipal sewage,the ability of wastewater treatment under low temperature and low c/n condition can be improved to some extent by adjusting the parameters,and the idea and method are provided for the application of compound bacteria agent,especially Bacillus compound bacteria agent in wastewater treatment.