| Effluent from municipal wastewater treatment plant (WWTP) can be reused inmultiple ways, which can effectively alleviate the problem of water shortage inBeijing.For the poor denitrogenation of wastewater, the WWTP effluent still containsa certain amount of nitrogen, and the discharge of nitrogen components intoenvironment through wastewater reclamation can lead to a number of public healthand environmental concerns. Therefore, it’s urgent to find effective approach forWWTP effluent further denitrification.For the water quality of WWTP effluent and less demand of organic carbon of3BER, a coupled system of3BER and sulfur autotrophic denitrification technology(3BER-S) was tested in this article to strengthening the nitrogen removal efficiency of3BER for wastewater with low C/N. The denitrogenation mechanism of3BER-S wasexplained by a comparative test between it and3BER, and the molecular biologytechnology was also applied.The impact of C/N、current intensity、pH and HRT on3BER-S were studied; and the variety of denitrifying bacteria of the biofilm in3BER-S under different C/N ratio and current intensity was also indicted.Furthermore,the microbial community structure and surface morphology were studied.Theoperating characteristics and nitrogen removal mechanism were discussed both fromthe macroscopic and microscopic view, which provide application reference for thefurther denitrification of WWTP effluent.The findings indicate that3BER-S is superior to3BER in TN removal efficiency,buffering pH and nitrite nitrogen accumulation.3BER-S is more suitable for thedenitrification of WWTP effluent with low C/N, and TN and NO3--N removalefficiency are35%and40%higher than3BER.Both of C/N ratio and current intensityhave little impact on nitrate and total nitrogen removal efficiency of3BER-S. Theaccumulation of SO42-per liter of the effluent was increased as the C/N ratio andcurrent intensity was decreased, and the maximum and minimumvalue was140mgand20mg respectively which meet the environmental quality standard for surfacewater. Single variable tests showed the most appropriate pH and HRT for3BER-Swas7.0~7.5and4h respectively.The quantitative analysis based on experimentalresult indicated that the sulfur autotrophic denitrification process was complementary to the hydrogenotrophic and heterotrophic denitrification process in3BER-S whichcould reduce the consumption of orgnic carbon effectively. The sulfur autotrophicdenitrification process can also balance alkalinity of the system which offerappropriate environmental conditions for denitrification.The16SrDNA clone library of3BER-S indicated that Betaproteobacteria is thedominant microorganism, and denitrifying bacteria take43.65percentrges in the clonelibrary.The results of scanning electron microscope (SEM) showed bacteria on thesurface of activated carbon particles and sulfur granules are mainly denitrifyingbacteria.NirS-based clone library of biofilm in3BER-S under different C/N andcurrent intensity indicated that both of C/N ratio and current intensity have greaterinfluence on biodiversity of denitrifying bacteria community in the biofilm.And thebiodiversity of denitrifying bacteria community is higher when C/N is low,whichillustrate high ecological stability. C/N ratio and current intensity also had certaininfluence on the proportion of denitrifing bacteria with different nutritive type.Theproportion of heterotrophic denitrifying bacteria is decreased as C/N is decreased;theproportion of sulfur autotrophic denitrifying bacteria is increased as C/N isdecreased;the hydrogen autotrophic denitrifying bacteria is increased as currentintensity is increased.The proportion of these three kinds of denitrifying bacteriachanged as the reaction condition changed,which ensure the high nitrogen removalefficiency of3BER-S under different reaction conditions.This study provide theoretical guidance for the application of3BER-S，and is ofgreate significance for improving the high levels of nitrogen in WWTP effluent aswell as the quality of the reclaime dwater. |
PDF Full Text Request