A review of anaerobic granulation under high-salinity conditions: Mechanisms, influencing factors and enhancement strategies

Anaerobic biological treatment of high-salinity wastewater has attracted much attention due to its environmental and economic benefits. However, the granulation can be significantly inhibited by a certain concentration of high salinity, which leads to the poor reactor performance and process stability. The presence of high salinity can also alter the structure of microbial communities and reshape the bacteria-archaea community. In this paper, the effects of high salinity on microbial communities in up-flow anaerobic sludge blanket (UASB) and the inhibition on the anaerobic granulation were reviewed. The effects of different salinities, substrate species and acclimation on the performance for treating high-salinity wastewaters were discussed. In this context, researches have adopted a variety of improvement and enhancement strategies, such as inoculation of adaptive sludge, addition of exogenous substances, addition of conductive materials, etc., which could improve microbial community structure, promote methane production, and enhance granulation to a certain extent. Finally, this paper offered prospects for some specific research topics, such as the culture of salt-tolerant microorganisms and the addition of exogenous substances, to provide theoretical direction for achieving better engineering applications.