Study On Acid Accumulation And Recovery In Anaerobic Baffle Reactor

Acidification is the common issue of anaerobic wastewater treatment process,which should be overcome in the practical engineering applications. Recent year, it hasbeen a hot topic that to illustrate the effect of acidification on performance efficiencyand microorganisms distributions, to improve the anti-acidification ability of anaerobicreactors, and to develop the rapid recovery protocols from acidification. Previousstudies on the acidification of ABR reactor mianly focused on the acidification causedby high organic loadings. Studies on recovery method were limited to physical chemicalmethod such as reducing organic loadings, increasing the alkalinity and so on. Seldomstudies have been carried out on the acidifications caused by other problems, such asmicroorganism activity inhibitors, also studies on the corresponding recovery methodwas still limited. Additionally, there have been some controversies on the traditionalacidification recovery methods, e.g. whether recirculation is a effective protocol toimprove the anti-acidification ability of anaerobic bioreactor, it is still not clear.In this study, the feasibility of backflow as an potential anti-acidification methodfor ABR was investigated. The influence of2-bromoethane sulfonate (BES) onpollutant removal efficiencies of ABR was studied, And three different kinds ofacidification recovery method was developed for comparison.The results show that:(1) Recirculation did not affect the COD removal of the ABR significantly.However, recirculation can stabilize the mixed liquid pH within the bioreactor.Additionally, recirculation can effictively relieve the accumulation rate of organic acidin ABR by1/3, which could benefit the anti-acidification abilities of ABR. Thedominant microorganisms in the recirculated reactor were Brevibacterium, Coccus, Streptococcus, Bacteroides, etc. And, the microorganisms diversity was enhanced byrecirculation. The average relative abundance of Eubacteria, Archaeahydrogen-producing acetogenic bacteria, and homoacetogenic bacteria in recirculatedreactor was8.5%,4.5%,3.5%and3%higher than in the non-recirculated reactor,respectively. PCR-DGGE results also showed that recirculation can improve themicrobial diversity and richness within the bioreactor, thus improving the stability ofthe microorganism communities structure. In conclusion, recirculation could effectivelycontrol pH, improve organic acid concentration and microorganism communitystructure, thus enhancing the anti-acidification ability of the ABR.(2) FISH and PCR-DGGE techniques were used to analyze the effect of2-bromoethane sulfonate (BES) on ABR performance. As the influent BES increasedfrom0to0.27mmol/L, the COD removal efficiency was decreased from95%to10%correspondingly. The mixed liquid pH value dropped as well as the organic acidaccumulated remarkably. The effluent organic acid reached up to around15.3mmol/L,in which acetic, pentanoic acid and hexanoic acid account for more than36%. Theaddition of BES caused significant acidification of ABR. when BES was added，therelative abundance of methanogens decreased by25%, and the relative abundance ofhydrogen-producing acetogenic bacteria and homoacetogenic bacteria increased by9%and7%, respectively. The PCR-DGGE results and diversity index analysis also showedthat the bacteria population diversity and richness decreased remarkably with theaddition of BES. And, the dominant species were changed from Firmicutes andbacterium to Bacteroidetes, δ-proteobacteria and Spirochaetes.(3) comparison of three different kinds of recovery method should that, in theinitial15days, sludge seeding method was the more efficient in the recovery of CODremoval. After15d, The COD removal of spontaneous recovery method was moresignificant. The COD removal recovery time of spontaneous recovery, sludge seedingand seeding granular sludge methods were30days,42days and50days, respectively.For pH recovery, no significant difference was shown among three recovery methods.All the effluent pH values reached above6.5within10days. As for effluent organicacid, The recovery time of spontaneous method was18d, while28days was taken forboth sludge seeding method and seeding granular sludge method.