Coupling Process And Control Of Mediation-intensified Sludge In-situ Fermentation And Denitrification

The combined process of nitrification-denitrification process is an effective method to achieve efficient nitrogen removal from wastewater,but it still faces two major problems:(1)insufficient carbon source and lower nitrogen removal efficiency;(2)low denitrification rate and low carbon source utilization.The produced fermentation liquid from wasted activated sludgecid can be used as a efficient carbon source for biological nitrogen removal.However,the ectopic fermentation pretreatment process is difficult and the operation cost is high.In addition,the higher NH4+-N concentration in the fermentation liquid increases the nitrogen loading rate of the influent.In this study,a sequential batch experimental system(SBR)was developed for the sludge in-situ fermentation and biological denitrification coupling process of medium-enhanced(riboflavin),and the main functions and operating conditions of the four reactors LO(control),LI(exogenous mud added),L2(exogenous mud and riboflavin added),L3(intermediate:riboflavin added)were constructed.Under the conditions of low temperature(T=8-15℃),mesotherm(T=30℃)and lean carbon source(C/N=2-4),the effect of redox mediator on in-situ fermentation of acid-extracting denitrification and denitrification was studied.The mechanism of enhanced denitrification process was explored and a high-efficiency nitrogen removal regulation strategy was proposed.At the same time,analyzed the microbial population structure and the coupling process mechanism from the perspective of microbiology in the reaction system.The main conclusions of this study are as follows:(1)Under the low temperature(8-15℃)and the in-situ fermentation sludge system,the mediator does not significantly improve the nitrogen removal efficiency.However,under moderate temperature and lean carbon sources,the mediator can strengthen the in-situ fermentation of sludge in the coupled system,and can also enhance the denitrification efficiency and carbon source utilization through electron mediation.During the stationary phase of the A/O/A sequence batch operation process(69 d),NO3--N removal percent was 62.43%,71.5%,76.63%,and 71.75%and TN removal percent was 52.43%,64.13%,73.4%,and 61.68%of LO,LI,L2 and L3,respectively.In the stable period of the whole process of anoxic sequencing(173 d),NO3--N removal percent were 26.68%,63.15%,79.97%and 57.72%and the removal percent of TN were 35.38%,67.45%,78.15%,and 47.32%of L0,L1,L2 and L3,respectively.The whole process of anaerobic is more conducive to the simultaneous fermentation of sludge and biological nitrogen removal.(2)The in-situ fermentation process of mediator-enhanced sludge did not significantly increase the concentration of COD and NH4+-N in the system effluent.The effluent COD concentration was around 40 mg/L,and the NH4+-N concentration was close to 0 mg/L.Real-time control and feedback of DO(1-2 mg/L)is of great significance for ensuring effluent and reducing the concentration of COD,NO2--N and NH4+-N.During the stable operation period of the whole process of anoxic process,the concentration of NO2--N in the effluent did not accumulate,and the NO2--N produced by incomplete denitrification could be removed by anaerobic ammonium oxidation.(3)Proteobacteria and Chloroflexi are relatively abundant abundances in the system,and β-proteobacteria are the most important class involved in the denitrification process.In the Genus level,Pseudomonas is the main acid-producing bacteria in the system,and Denitistia,Anammox and Thauera are the main denitrifying bacteria.The copy number of the genus Nitrospira,Denitotisoma,genus and Thauera in L2 was 2.3-folds than that in the control group(L1),and the mediator promoted the coupling system.Mediator promotes the growth of denitrifying bacteria in the coupled system.