Performance And Microbial Communities For Pollutant Removal In A Novel Distributed-inflow Biological Reactor(DBR) For Treating Piggery Wastewater

During the last three decades,with the development of economy and pig breeding in China,correspondingly,piggery wastewater has become the main component of agricultural pollutants,and seriously harmed the water environmental safety.The public is becoming increasingly concerned with the piggery wastewater potential impact on the water environment.Piggery wastewater is characterized by high concentrations of COD,ammonia,total nitrogen,and suspended solids,as well as intricate components(salts and heavy metals),but a low ratio of C/N.In order to reduce or solve the pollution,a novel distributed-inflow biological reactor(DBR)was developed to treat piggery wastewater.First,the removal efficiency of organic matter and nitrogen in piggery wastewater by DBR was investigated when the influent bypass rates varied from 0.2 to 0.5.Second,under the optimal influent bypass rate,the elimination of antibiotics in wastewater by DBR was studied.In addition,the fluorescence excitation-emission matrix spectra(3D-EEM)coupled with parallel factor analysis(PARAFAC)were used to illuminate the organic components in piggery wastewater and DBR effluent.Finally,during the spring and winter,the high throughput sequencing technology was applied to reveal the microbial community structure of seed sludge(wastewater treatment plant,WWTP),DBR,and Anoxic/aerobic system(A/O),and the relationship between the key microbial populations and the removal of the pollutants.Draw the following the conclusions:(1)Results of lab-scale experiments showed that when DBR(composed of DBR-1 and DBR-2)was applied to eliminate pollutants from piggery wastewater,the bypass flow rates(x=0.2-0.5)had no significant effect on the removal of COD and ammonia,and the removal efficiencies of COD and NH4+-N were 86.6%and 96.8%,respectively.However,the total nitrogen(TN)removal was apparently influnced by the bypass flow rate,and a bypass flow rate in the range 0.3-0.4 could be regarded as the optimal bypass rate,yielding TN removal efficiencies in the range 80.6%-86.2%.In order to identify the real-time variations of organic and nitrogen in DBR,track studies of SET 2-3 were conducted in a full cycle of the reactor.Results showed that the COD concentrations in DBR-1 and DBR-2 remained stable during one complete cycle,and the primary reason was the efficient elimination of aerobic heterotrophic bacteria and heterotrophic denitrifiers.Although the concentrations of NH4+-N,NO2-N and NO3--N fluctuated periodically,the effluent COD and TN in DBR remains stable.In addition,during the aerobic phase,nitrification rate and the variation rate of pH had a good correlationship in the DBR.Finally,compared to traditional A/O system,DBR was found to be more efficient to remove TN and reduce energy consumption and simplify the management in this study.(2)The biodegradation of oxytetracycline(OTC)by intermittent-inflow one-stage anoxic-aerobic process(A/O)in piggery wastewater was studied.When the influent was added with 0.1 and 1 mg/L concentration of OTC,the removal rate of OTC in A/O process were 81%-89.8%and 96%-98%,respectively,and the biodegradation of OTC by anoxic microorganisms could be the principal pathway.And when the concentration of OTC was 0.1 mg/L in influent,it had no effect on the performance of A/O process,but the concentration increased to 1 mg/L,the nitrification and denitrification were clearly affected.And both of these concentrations had no effect on COD removal.Moreover,the removal of OTC and Tetracycline(TC)in piggery wastewater by DBR were 84.1%and 63.6%,respectively,the removal of OTC and TC by continuous-inflow two-stage A/O system were 76.6%and 61,5%,respectively.The removal difference of two antibiotics may be related to their physicochemical properties.(3)3D-EEM was used to characterize the organic components in piggery wastewater and effluent of biological systems,and PARAFAC was applied to extract the pure spectra from the overlapped spectra.Three main components,C1(240,305/415nm,humic-like substances),C2(275/320nm,tyrosine-like matter),C3(220/300-350nm,tryptophan-like matter),were identified from the piggery wastewater.Meanwhile,three mains components,C1(240,330/420 nm,humic-like substances),C2(265,370/490 nm,humic-like substances),C3(235,280/350 nm,tryptophan-like matter),were identified from effluent of DBR and A/O system.Although there were the same components in effluent of DBR and A/O system,the fluorescence intensities of C1-C3 in effluent of A/O system were lower than those of DBR.Besides,results of fluorescence index(FI)and autotrophic productivity(β/α)demonstrated that the refine organic matters in effluent of DBR and A/O system composed of terrestrial plants and metabolic organics of microbial bacteria.(4)Results of high throughtput sequencing illustrated that the intricate components of piggery wastewater had an obviously effect on the community diversity.Compared to the DBR and A/O system,there are more excellent diversity and richness of microbial community in WWTP.In phylum level,the Proteobacteria and Bacteroidetes were the most dominant microorganisms of three biological systems.And in class level,theβ-Proteobacteria was the predominant order for degrading and eliminating carbon,nitrogen and aromatic organic matters from wastewater.At genus level,the aerobic heterotrophic bacteria(Chryseolinea,Filimonas and Fluviicola)were mainly responsible for the organic removal in the DBR and A/O system.Besides,high content nitrogen in wastewater was eliminated by the Ammonia oxidizing bacteria(AOB,Nitrosomonas)and denitrifiers(Comamonas,Thauera).Above three functional bacteria were the most important in DBR and A/O system.Additionally,anaerobic heterotrophic bacteria(Ignavibacterium and Bacteroides),facultative bacteria(Lautropia and Perlucidibaca),and others bacteria may assist and favor the elimination of intricate pollutants in wastewater.It’s worthy that although the removal efficiency of ammonia and TN was excellent,the nitrite oxidizing bacteria(NOB)were not detected in the DBR and A/O system in spring and winter.As for WWTP,in spring and winter,the relative abundances of most of functional bacteria were steady except denitrifiers.And as for DBR and A/O system,the abundances of AOB and phosphorus accumulating organisms(PAOs)were lower than those in winter,however,the abundances of the other functional bacteria were affected apparently by season changes.Finally,the metabolomics analysis of three systems demonstrated that the metabolites of bacteria in DBR and A/O system consisted mostly of amino acids,carbohydrates,polyols,and so on,while the metabolites in WWTP were constitutive of ketones,amines,acids,esters,and so on.