Research On Mariculture Wastewater Treatment And Microbial Diversity In SMBR Process

Along with the rapid development of Chinese marine aquaculture industry,the problems of mariculture wastewater treatment are increasingly outstanding in conventional activated sludge process,such as large area,more sludge production and so on.There was not suitable for mariculture wastewater treatment technology promotion.Based on the above problems,submerged membrane bioreactor（SMBR）was used to treat mariculture wastewater in the research.The effect of salinity in the period of acclimated salt-tolerant activated sludge on conventional pollutants remove which employs the conventional activated sludge MBR process（CAS-MBR）and Anoxic-Oxic MBR process（A/O-MBR）of SMBR process was respectively analyzed,operation conditions were optimized based on HRT and SRT,the elements and structures of the effluent in the best operation conditions were analyzed,and the PCR-DGGE and similarity analysis were applied on biological diversity.The dominant strains were determined and the similarity among bacteria was analyzed.Operating conditions of SMBR were DO=0.5¹.0 mg/L in CAS-MBR,DO=4.0⁵.0 mg/L in Oxic and DO=0⁰.5 mg/L in anoxic and reflux ratio was 150% in A/O-MBR in the period of acclimated salt-tolerant activated sludge.Hydraulic retention time（HRT）were 24 h and were no sludge discharge in the MBRs.When salinity was 0¹6 g/L,the removal rates of CODMn and ammonia nitrogen were more 80% and 90% and kept stable in the continuous aeration SMBR.But the nitrite accumulation was serious in every early period with the increment of salt concentration.The bacteria activity was gradually inhibited,and the inhibition level was positively correlated with the salinity in the earily period（within 10 h）.SOUR decreased 6.71 mg/（g·h）and 14.52 mg/（g·h）in 16 g/L compared with 0 g/L in autotrophic and heterotrophic bacteria.Meanwhile,the amount of protein and polysaccharide in SMP and EPS significantly raised as the salinity increased,showing that the release of NH₄⁺-N due to the protein hydrolyzed and organic matters in the sludge system was also the reason for the decline of the removal rates of COD and ammonia nitrogen.When salinity was 0⁶.4 g/L,microbial activity inhibition was dominated;high salt environment（6.4¹6 g/L）organic matter release was dominated.The best operating conditions of SMBR in the nitrogen and phosphorus removal were HRT=18 h,SRT=7 d and MLVSS=3400 mg/L in CAS-MBR and HRT=14 h,SRT=12 d and MLVSS=4500 mg/L in A/O-MBR.The effelent quality of SMBR in the best operating conditions were CODMn≤30.0 mg/L,NH₄⁺-N≤1.0 mg/L,NO₃^--N≤2.5 mg/L,NO₂^--N≤0.06 mg/L,TP≤2.4 mg/L in CAS-MBR;A/O-MBR:CODMn≤18.0 mg/L,NH₄⁺-N≤0.6 mg/L,NO₃^--N≤1.5 mg/L,NO₂^--N≤0.04 mg/L,TP≤1.5 mg/L in A/O-MBR.Marine aquaculture wastewater DOM fluorescence was two categories,class fluorescent protein and class humic acid fluorescence.The removal rate of high excitation wavelength tryptophan of protein-like fluorescence in the best operating conditions was only not effective.The organic matter effluent was mostly difficult degradation microbial metabolites that were the structure of olefin and aromatic in SMBR,especially low excitation wavelength tryptophan,fulvic acids and Hu Min acids.And the removal effect of TP needed to be improved in SMBR.The depth processing needed to be carried out.In order to research environmental microbial community diversity in the period of stable operation of SMBR,PCR-DGGE technique was used in this paper.The cultivation of sludge was a sequencing process,which was due to the self-modualation of the microorgannisms to the environment changes in different period of time.The microbes were widely distributed after salt acclimation,and the dominant species were widely distributed in different genera or genera.The majority of clone sequences belonged to Alphaproteobacteria 、 Betaproteobacteria 、 Gammaproteobacteria 、Bacteroidete and Chloroflexi,especially Betaproteobacteria in SMBR to treat mariculture wastewater.