Experimental Study On Treatment Of Domestic Sewage By EGSB Reactor At Ambient Temperature

In this paper,the start-up and operational efficiency of anaerobic expanded granular sludge bed?EGSB?reactor treating domestic sewage was studied.In order to provide reference for the application of anaerobic biological process in low concentration sewage treatment,by tracing and analysising the characteristics of water quality and granular sludge,the effects of process parameters such as HRT,reflux ratio and rising velocity on the removal of pollutants were investigated,it showed that the influent load would increase the mass transfer reaction of microorganisms in the reactor.According to the specific structure and flow condition of EGSB,by gradually shortening HRT?14 h,7 h and 4 h?,the removal of pollutants in low concentration domestic sewage was enhanced,In the hydraulic retention time?HRT?for 4h,the average removal rate of COD,NH₃-N,TN and TP was 9.7%?47.2%?58.2%and28.7%,the effects of reflux ratio of 2:1,2.5:1 and 3:1 on the treatment efficiency of EGSB were investigated,the results showed that,with the increase of flow velocity and microbial increased activity in the column,the removal rate of each pollutant was further upgraded to 76.4%?57.3%?64.8%and 45.7%.At the same time,the inoculated biogas fermentation sludge bacame the status of the coexistence of dark brown and a small amount of granular sludge from the initial brown flocculent.Sludge concentration increased from 18g/L to 27 g/L,VSS/SS=0.78.This showed that in the process of treating domestic sewage,HRT shortening and effluent reflux are favorable for the granulation of sludge,the start-up and stable operation of the reactor at high flow rate and low load were realized.The performance of reactor's restart by inoculating anaerobic granular sludge of papermaking wastewater after EGSB outage was investigated.The reactor has successful start-up in 16 days.The average removal rate of COD,TN and NH₃-N was65.0%?47.4%and 40.0%,characteristics of granular sludge was analysised before and after domestication,the sludge concentration is reduced from 45.8g/L to23.2g/L,VSS/SS decreased from 0.91 to about 0.85.In the upper layer of the reactor,the concentration of sludge is increased,and the biological activity is enhanced,and the granular sludge is effectively expanded.The ratio of sludge in0.8¹.25 mm and 2³ mm range increased from 17.64%to 27.99%,reduced from41.05%to 13.25%respectively.In addition,the settling velocity of granular sludge was in the range of 10.2¹27.4 m/h,most of which was above 50 m/h.SEM analysis showed that there were many holes and points in the granular sludge,there has many baculovirus,filamentous bacteria and some spherical bacteria in the sludge too.