Inveatigation Of Enhanced Technology Of In-situ Side-stream Sludge Reduction System

The side-stream reactor coupled membrane bioreactor?SSR-MBR?process is an improved process of aerobic/settled/anaerobic?OSA?,based on which the coupled physical methods?ultrasonic coupled packing carriers and micro-aerobic conditions?were used to enhance sludge reduction.Through the combination of batch experiment and laboratory-scale continuous experiment,the mechanism of sludge reduction,the release and utilization of secondary matrix,the characteristics of sludge,the membrane fouling and the relationship with microbial population structure were studied.?1?Effects of ultrasonic pretreatment and packing carriers on sludge reduction,settleability,dewaterability and microbial community structure in the anaerobic side-stream reactor?ASSR?were investigated with three anaerobic reactors operated in parallel.Ultrasonic pretreatment increased sludge reduction from 3.65%in the ASSR to 5.08%,and packing carriers further enhanced the efficiency to 19.2%.Ultrasonic pretreatment of sludge decreased oxidation-reduction potential in ASSR and enhanced the release of intracellular substances,while packing carriers played more important roles for enhancing sludge reduction.The deterioration of sludge settleability and dewaterability in the ASSR after ultrasonic pretreatment was improved by packing carriers.Illumina-MiSeq sequencing showed that microbial richness and diversity increased after ultrasonic pretreatment and packing carriers in the ASSR.Packing carriers favored the growth of slow grower?Dechloromonas?,fermentative bacteria?Draconibacteriaceae,Fusibacter,Acidaminobacter?and floc-forming bacteria?Zoogloea?,while hydrolytic and predatory bacteria?Saprospiraceae_unculture?and slow grower?Thauera?was enriched in the ASSR.?2?Through the optimization of ultrasonic conditions,it was found that the effect of sludge lysis was best under conditions with ultrasound intensity of0.2 W/ml and ultrasonic time of 10 min.Besides,The sludge in ASSR coupled with packing carrier?PASSR?which was fed by the sludge under ultrasound intensity of 0.2 W/ml and ultrasonic time of 10 min had a a higher degree of sludge lysis.The analysis of extracellular polymeric substances?EPS?components and characteristics showed that soluble microbial products?SMP?content of PASSR sludge was the highest among 0-2 h under the conditions,and more degradation of SMP between 2-24 h.The three-dimensional fluorescence analysis also showed that proteins of PASSR sludge had more dissolution at 0 h,and effect of degradation was best at 12 h?5.3%and13.9%?.Besides,the increase of humic substances was the highest at 12 h.The disintegration kinetics of MLSS and MLVSS and the dissolution kinetics of TKN show that the kinetic equation had the highest degree of fitting and disintegration and hydrolysis coefficients under the condition with ultrasound intensity of 0.2 W/ml and ultrasonic time of 10 min.?3?The optimal ultrasonic conditions of batch experiment screening were applied to the SSR-MBR system and found that inserting of ASSR with different pretreatment did not affect COD and NH₄-N removal of the system.The sludge reduction rates of ASSR-MBR?A-MBR?,ASSR coupled packing carrier?AP-MBR?and ASSR with ultrasound coupled packing carrier?AUP-MBR?were 22.4%,31.9%and 40.6%,respectively.AUP-MBR promoted dissolved organic matters?DOM?release and utilization by enriching hydrolytic,fermentative bacteria in the main reactor and slow growers on the surface of the packing carriers.And it obtained the highest nitrogen removal?57%?,and enriched denitrifiers were found in ASSR_AUP.In addition,the enrichment of filamentous bacteria in AUP-MBR led to the deterioration of sludge dewaterability,and it accelerated the membrane fouling rate.AP-MBR also promoted DOM release and utilization by enriching hydrolytic,fermentative bacteria in the main reactor and slow growers on the surface of the packing carriers.But the lowest relative abundance of filamentous bacteria improved the sludge dewaterability,and it reduced the membrane fouling.Besides,the enrichment of dominant polyphosphate bacteria was found in anoxic/oxic MBR?AO-MBR?.Furthermore,the microbial diversity and richness increased after ultrasonic pretreatment and packing carriers,respectively.?4?A micro-aerobic side-stream reactor?MSSR?was inserted in returned sludge line of the membrane bioreactor?MBR?for sludge reduction.Three MSSR coupled MBRs?M-MBRs?and an AO-MBR were operated in parallel to investigate effects of micro-aerobic condition and hydraulic retention time of MSSR?HRT_M?on process performance.M-MBRs and AO-MBR were equally effective in COD and NH₄-N removal.Rising HRT_M from 3.3 to 6.7 h increased sludge reduction from 10.8%to 47.5%,and promoted DOM release and utilization by enriching hydrolytic,fermentative and predatory bacteria.M-MBR at HRT_M of 3.3 h obtained the highest nitrogen removal,and enriched denitrifiers?Thauera and Hyphomicrobium?in the MSSR.The highest relative abundance of polyphosphate-accumulating organisms was observed in M-MBR at HRT_M of 5.0 h,which achieved the highest phosphorus removal.Prolonging HRT_M to 6.7 h improved sludge dewaterability by enriching floc-formation bacteria?Nannocystis?and inhibiting filamentous bacteria?Candidatus_Alysiosphaera?.