| Against the backdrop of global water resource shortages,obtaining clean water,nutrients,and energy from wastewater has gradually become a trend.As a wastewater treatment process that combines anaerobic digestion and membrane distillation,Ana MDBR has the above three functions and high potential for wastewater resource utilization.Currently,the research on An MDBR mainly focuses on the efficiency of wastewater treatment,while the research accumulation on membrane fouling and microorganisms in the reactor is still insufficient,which will directly affect the effectiveness of membrane distillation and anaerobic digestion processes;In addition,as a heat treatment process,the temperature of An MDBR has a significant impact on its operating efficiency.Therefore,in this study,temperature was used as a single variable to evaluate the wastewater treatment efficiency of An MDBR,focusing on systematic investigation and analysis of membrane fouling behavior during the operation of the reactor.In addition,biological analysis was conducted on the structural characteristics of microbial communities in the reactor to investigate the methanogenic functional bacteria and methanogenic pathways in An MDBR at different temperatures.In this study,An MDBR was operated at medium and high temperatures(45 °C,55 °C,65 °C)to investigate the wastewater treatment effect of the process through monitoring the concentration of COD,ammonia nitrogen,and phosphorus in the reactor.At the same time,the impact of temperature on energy recovery and clean water production of the process was investigated by measuring methane production and membrane flux.The results showed that An MDBR had excellent removal efficiency for COD,ammonia nitrogen,and phosphorus(removal rates were >98 %,50.11-99.46 %,and >99 %,respectively)and was not affected by temperature.In contrast,methane recovery efficiency and membrane flux were significantly affected by temperature.Increasing the operating temperature of the reactor could increase methane production and the proportion of methane in biogas,while achieving higher membrane flux.However,membrane fouling was more severe and membrane flux decreased faster.Subsequently,the characteristics of membrane fouling during the initial and final stages of An MDBR operation were analyzed.The results showed that organic contamination appeared on the membrane at the initial stage of operation,and increased with the increase of operating temperature,resulting in a rapid decline in membrane flux at the initial stage;At the end of operation,membrane fouling consists of a combination of organic and inorganic contaminants.In addition,the morphology and distribution of pollutants on the membrane change with temperature,i.e.,as the operating temperature increases,organic pollutants change from aggregation to dispersion,and inorganic pollutants grow from blocky to flaky.The increased temperature promotes the fusion of the two to form a denser pollution layer,resulting in a significant decrease in membrane flux.Finally,the characteristics of microbial communities in An MDBR were analyzed.The results showed that temperature significantly affects the population structure and species composition of microorganisms in the reactor.At experimental temperatures,microorganisms in the reactor have a certain degree of heat resistance,but the differences in heat resistance still lead to significant species differences between reactors at higher temperatures.Despite this,the metabolic functions of microorganisms in the reactor are similar,with hydrogen producing fermentation bacteria(Defluviitoga,Pseudomonas,Caldicobacter,etc.)and hydrogen type methanogens(Methanobacter and Methanotherobacter)predominating.Therefore,the methanogenic pathway of An MDBR at medium and high temperatures is a hydrogen type methanogenic pathway. |
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