| Driven by the strategy of"carbon peaking and carbon neutral"and wastewater resource utilization,the traditional wastewater treatment model of exchanging energy consumption for water quality is changing to a new model of deep pollution reduction,high-efficiency capacity,emission reduction and carbon synergy.Anaerobic membrane bioreactor（An MBR）can achieve complete separation of hydraulic retention time（HRT）and sludge age,retaining sufficient biosolids in the reactor,making it possible for efficient and stable energy recovery of municipal wastewater.An MBR technology has high efficiency in chemical oxygen demand（COD）removal and methanogenic performance,which has a broad development prospect and is an ideal technology for anaerobic biological treatment of wastewater.At present,An MBR has been applied in other fields such as industrial wastewater,but the treatment of municipal wastewater is still mainly based on laboratory pilot studies.Due to the characteristics of municipal wastewater with large water volume and low temperature,the methanogenic efficiency and membrane fouling of An MBR applied to municipal wastewater treatment still need to be further evaluated at the engineering scale.Based on this,this study constructed a submerged pilot anaerobic membrane bioreactor system for municipal wastewater treatment,and studied the pollutant removal and methanogenic performance of the system,membrane filtration characteristics and influencing factors,as well as energy consumption and carbon emission during the treatment process,with the following main findings:（1）The process performance of An MBR for municipal wastewater treatment was studied,and the pollutant removal,methane production performance and COD flow were analyzed.An MBR can remove COD stably and efficiently with a COD removal rate of 83.3±3.1%,in which the membrane has a significant retention effect on SMP,and the membrane retention rate can reach more than 80%.The methane production rate ranged from 0.25-0.31 L/g CODr,and 52-63%of COD in the feed water was converted to CH4,of which more than 80%of CH4 existed in the form of biogas,and methane production was the main pathway for COD removal.The low temperature suppressed the methanogenic activity,and the activity values of acetic acid nutrient and hydrogen nutrient type active were reduced by 80%and 93%,respectively.With the shortening of HRT and the increase of temperature,the sludge electron transfer system activity was enhanced and the methanogenic performance was improved.（2）The membrane fouling rate,sludge mixture characteristics and different operating parameters were investigated to reveal the core influencing factors of membrane filtration performance.The membrane fouling rate ranged from 0.02-2.3k Pa/d.The membrane fouling rate tended to increase with the shortening of HRT,and its magnitude was related to the operating temperature and sludge concentration.When the operating temperature increased,the sludge activity increased and the sludge filtration specific resistance decreased from 3.12±0.189×1014to 0.92±0.003×1014m/Kg MLVSS,and the membrane filtration performance improved.The membrane filtration performance at different specific gas aeration（SGA）per unit area showed a significant positive correlation between SGA and TMP,with low membrane fouling operation at an SGA of 0.7 m3/m2/h at a membrane flux of 14.4 LMH（HRT=10 h）.As the membrane filtration performance decreases with lower operating temperature,it is necessary to improve the filtration performance by adjusting the SGA and sludge removal（maintaining MLSS at approximately 9 g/L）.（3）The energy consumption,optimal operating conditions and environmental impact of the An MBR process for municipal wastewater treatment were studied based on energy consumption calculations and LCA carbon emission analysis.The total energy consumption was 0.350-0.611 k Wh/m3,with the biogas cycle being the main energy expenditure（47.3-70.5%）.When dissolved methane is recovered,electricity consumption is the main source of total carbon emissions;when dissolved methane is not recovered,direct carbon emissions in the effluent are significantly higher than when dissolved methane is recovered.The direct carbon emissions in the effluent without dissolved methane recovery increased significantly compared to the dissolved methane recovery,and the effluent was the main source.The carbon emission decreases with the shortening of HRT,and the smallest carbon emission is 0.172 kg CO2-eq/m3 at HRT=10h（when dissolved methane is recovered）.Combining the organic removal and membrane filtration performance,HRT=10 h is the best operating condition to be selected. |
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