Treatment Of Saline Sewage By SBR-ultrafiltration And Analysis Of Microbial Community

In this paper,the domestic sewage from ships and offshore platforms was treated by SBR-UF technology.The activated sludge in SBR reactor was domesticated at five different salinity levels from 2wt%to 4wt%by adding seawater to increase salinity.After five domestication cycles with different salinity,the SBR reactor operated steadily,the effluent quality was good,and the domesticated sludge remained high activity all the time.No sludge bulking occurred during the sludge domestication.The COD_Cr removal rate of effluent can reach 92.34%,the NH₄⁺-N removal rate of effluent can reach 88.96%,and the TP removal rate of effluent can reach 84.27%.External Ultrafiltration Membrane Module was used to treat the effluent of SBR system.The turbidity and chroma of effluent of SBR reactor system were greatly improved after the treatment of Ultrafiltration Membrane Module,and the removal rate of organic pollutants in effluent of SBR reactor system was slightly increased.The final effluent COD_Cr of SBR-UF technology is 34.10 mg/L,NH₄⁺-N is 2.07 mg/L,TP is 0.77 mg/L,and the effluent pH is 7.5,which meets the existing standards for domestic sewage discharge from ships and offshore platforms.The increase of salinity in domesticated sludge shows strong selectivity to microbial population.The increase of salinity in domesticated sludge will gradually eliminate microorganisms that are not suitable for high salinity environment,and the remaining dominant microbial population in domesticated sludge will become the key bacteria for treating saline domestic sewage in high salinity environment.After a long-term use of sea water in domesticated sludge,the relationship between activated sludge and seawater bacteria in domestication stage is closer than that of other inland or coastal sewage treatment plants.After a long period of sea water domestication,a new salt-tolerant activated sludge with both salt tolerance and degradation of organic pollutants was obtained.The domesticated sludge combines a small part of microbial community in activated sludge of traditional sewage treatment plant and most of seawater bacteria,which can ensure high removal rate of organic pollutants in sewage under the condition of high salinity tolerance.Flavobacteriia on the Class level;Flavobacteriales,Rhodobacterales,Propionibacteriales on the Order level;Winogradskyella,unclassified_fFlavobacceae,unclassified_fRhodobacteraceae on the Genus level;all of these bacteria can maintain high population abundance under high salinity conditions and simultaneously treat organic pollutants in SBR reactor,and these bacteria are the key bacteria for the treatment of domestic sewage from ships and offshore platforms.