Change Of Microbial Community Structure And Ecology Reponse Mechanism Of Aerobic Granular Sludge Under Salt Stress

Aerobic granular sludge (AGS) is a special form of microbial immobilization, withdense structure, good settling performance, strong bio-collaboration and good pollutantremoval effect. High salinity organic wasterwater treated by the AGS had become a hotresearch field. The study of microbial community structure changing and the ecologyreponse mechanism of AGS under salt stress would have a great significance in thefuture.In this paper, the AGS was stressed by the Simulative salinity organic wastewater(the salt concentration calculated by NaCl) in sequencing batch reactor (SBR). With thestudy of the change of AGS characters and pollutant removal effect, it utilized denaturinggradient gel electrophoresis (DGGE) to study on microbial community structure. Thecomponents of Na+、K+and Ca2+content changing in AGS microorganisms were analyzedby atomic absorption spectroscopy (AAS). The related proteins of AGS under salt stresswere identified by two-dimensional electrophoresis (2-DE) and mass spectrometry (MS),and managed to come to the following conclusions.(1) Under normal circumstances, mature aerobic granular sludge was orange, regularshape, smooth and dense structure. However, with the salinity rising, the AGS color wouldgradually turn white, while the structure became loose, and tended to produce a poorsettling performance. The MLSS and SVI changed from4593mg/L and48.73mL/g to2880mg/L and95.28mL/g, while sedimentation rate also dropped to48.86m/h from93.42m/h, this showed that the particle size did not change significantly. The AGS wascomposed of filamentous bacteria, bacilli and cocci. There were many pores and channel inthe AGS, which could be related to the microorganisms growth and metabolism andpollutant removal.(2) Mature aerobic granular sludge had a good removal effect for COD, NH3-N, TNand TP in normal environment. High salinity had a significant impact on the removal ofCOD and TN. When the salinity was15g/L, the removal rate of COD and TN declined to59.9%and55.9%. The NH3-N removal was not affected by the salinity with the removalrate always above70%during salt stress. TP removal was rarely by low salinityenvironment, but it had severely affected by high salinity, the removal rate was only57%when the salinity was15g/L.(3) PCR-DGGE was used to analyse the change of microbial community structure in aerobic granular sludge under salt stress. The results showed that microbial communitystructure of the AGS were different in different salinity. Dominant microorganismpopulations of the AGS in high salinity environment were Hydrogenophaga,Corynebacterium, Actinobacterium, Beta proteobacterium, Streptomyces、 Anaerobicbacterium, Psychrobacter, Bacillus, etc.(4) The concentration of Na+in the aerobic granular sludge microorganism decreasedduring salt stress, but K+and Ca2+were on upward trend. Microorganism was able totolerate high salinity through absorption of K+and discharging Na+with Na+-K+pump,Na+/H+antiporter protein and K+channel. Ca2+could keep the membrane stability,permrability and completeness, and as the second messenger adjusted microbialphysiological and biochemical reactions.(5) The six kinds of related proteins were identified by2-DE and MS.Under highsalinity expressed membrane protein, porin, EthB and ABC transporter substrate-bindingprotein, which paly a significant role to tolerate high salinity.