| Municipal wastewater treatment plants produce a large amount of sludge to meet the standard treatment of wastewater,and the sludge actually enriches a large amount of pollutants in the wastewater,which must be treated;advanced anaerobic technology has good sludge stabilisation,harmless and resource recovery effects,but at present the anaerobic digestion stage is still a CSTR(Continuous Stirred Tank Reactor)mode of operation,with long hydraulic residence time and large reactor volume,is difficult to adapt to the inconsistent degradation rate of soluble/insoluble organic matter.In this study,anaerobic digestion was upgraded with ASBR(Anaerobic Squencing Batchreactor)mode and further enhanced with AMBR(Aerobic Membrane Bioreactor)to improve the physicochemical properties of sludge,enhance the methane production effect,system stability and municipal sludge treatment efficiency.Firstly,the thermal hydrolysis temperatures of 150℃,160℃,170℃ and 180℃ and the thermal hydrolysis times of 15 min,30 min,45 min and 60 min were set to investigate the modification effect of different conditions of thermal hydrolysis treatment on mixed sludge and to screen the best thermal hydrolysis treatment conditions.The study showed that the dissolved solids,continuous hydrolysis of organic matter,improved rheological properties,settling performance and methane production performance of the sludge were significantly better after the thermal hydrolysis treatment,in which the DS(Dissolved Solids)content was 3.64～6.4 times higher than that of the sludge without thermal hydrolysis treatment,and the COD(Chemical Oxygen Demand)leaching rate increased by 21.3%～30%compared to the non-pyrolysed sludge,and the direct digestion and gas production rate increased by 32%～59%respectively after the sludge was treated with thermal hydrolysis compared to the pre-dewatered sludge,and the effect of thermal hydrolysis modification was further improved with the increase of thermal hydrolysis temperature and thermal hydrolysis time,and the thermal hydrolysis temperature was the main factor compared to the thermal hydrolysis time.Secondly,the study of ASBR operation effect under different conditions was carried out to optimize the operation parameters.The results showed that the ASBR reaction mode had different degrees of gas production enhancement under different feed solids content conditions,different thermal hydrolysis temperature feed conditions and different OLR(Organic Load Rate)conditions,with the maximum gas production enhancement of 10～15%and SCOD(Solluted Chemical Oxigen Demand)removal rate.The ASBR model has a significant settling effect at lower feed solids rates,which is conducive to the development of AMBR,and the ASBR model has a greater load tolerance.The AMBR reactor was then constructed and the operational parameters were verified and the operational effects were studied.The study showed that the AMBR had good retention of SS,the TCOD removal rate was greater than 90%under AMBR operating conditions,the gas production rate was 6%higher compared to ASBR and the effluent properties were stable.Finally,the microbial communities in the CSTR and ASBR reactors were observed and analysed to reveal the microscopic changes of the systems.The study showed that methanogenic octococci gradually accumulated in the ASBR reactor and their relative abundance was higher than that in the CSTR reactor,and that the dominant bacterial group changed during anaerobic digestion,with the function gradually specialising from a parthenogenic,multi-metabolic phylum to a hydrolytic acidifying and specialized methanogenic group. |
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