Study On The Pilot Trial Of Denitrification With Anoxic RBCs

Nowadays,the city wastewater treatment developed well in China,while the medium and small town wastewater treatment still has considerable room to improve,because of the awareness of environment protection started late and the economic development was underdeveloped.The town wastewater has characteristics such as small amount of wastewater,large change coefficient of pollution,underdeveloped economic,shortage of land area,weak technical force and management difficulties.Compared with activated sludge process,rotating biological contactor(RBC)is more suitable for town wastewater treatment,on account of its advantages,such as good treatment effect,a small amount of residual sludge,small footprint,simple operation,low installation and running costs.Improving biological nitrogen removal efficiency has become the core problem in the field of wastewater treatment.At present,most of the engineering applications in our country are confined to aerobic RBCs,but nitrification is the primary reaction in aerobic RBCs while denitrification is always not sufficient.The experiment results of anoxic RBCs showed that the denitrification effect was significant,but the actual application was rarely reported,even the pilot tests.The treatment effect of the submerged anoxic RBC on different pollutants in domestic wastewater was studied by using a 3-dimensional structure RBC in this pilot test,also the denitrification kinetic model was derived.Biofilm and microbial community structure were investigated by the method of 16S rRNA gene sequencing.Research results indicated that:(1)When the concentration of the influent nitrate was 6mg/L,to make sure the remove efficence no less than 90%,the HRT must longer than 2h.The optimum operating load of nitrate nitrogen in denitrification was 1.54 g/(m~2·d).Changes in nitrite nitrogen kept pace with nitrate nitrogen.The removal of COD is about 6 to 10 times of the removal of nitrate nitrogen.Anoxic RBCs had no obvious effect on removal of ammonia and TP.(2)The actual denitrification in anoxic RBC fit mostly with half-step kinetic model,there is no significant difference between the theoretical value calculated by the experimental value and the deduced half-step reaction kinetic equation.The required disk area can be calculated according to the model,while the design flow,influent and effluent nitrate concentrations is known.This can effectively guide actual engineering design.(3)Biofilm and microbial community structure were investigated by the method of16S rRNA gene sequencing.After the long-term operation,there was a big difference between anoxic RBC and aerobic RBC,microorganisms in anoxic environment is more diverse.However,the homogeneity of microbial populations in aerobic organisms was higher,and the grade of biological and the difference of microbiologic is more significant in aerobic RBC.