Study On A/O-MBR+ Worm Bed Reactor Combined Process For Sewage And Sludge Treatment

In the process of purifying sewage by the activated sludge method,a large amount of remaining sludge as a by-product not only increases the cost of sewage treatment,but also has the risk of secondary pollution caused by improper treatment.For a long time,under the influence of the mainstream concept of "heavy water and light sludge",issues related to sludge treatment costs and hazards have become increasingly obtrusive.Compared with other sludge reduction technologies,it has low construction and operation costs,ecological Notable features such as environmental friendliness.In the preliminary study of the in-situ reduction technology of biological predation sludge,the research group designed and manufactured different configurations of biological predation sludge reduction reactors at the pilot level,and coupled it with different sewage treatment process systems,To achieve efficient collaboration between sewage treatment and sludge reduction,and has a certain effect in membrane pollution control and sludge property improvement.In this study,at the pilot level,the anoxic/aerobic-membrane bioreactor was coupled with the worm bed reactor to form an A/O-MBR+ worm bed combined process to explore the optimization of its operating mode and operating parameters.In order to investigate the efficiency of sewage treatment,sludge reduction,membrane pollution control and residual sludge property improvement,and finally to explore the mechanism of sludge reduction of the combined process in the form of sequential batch experiments.The results of beaker experiments with temperature as a single factor variable determined that the optimum working range of worms was 20?25 ?.When the temperature exceeded 30 ?,the growth and reproduction ability of worms and sludge predation capacity decreased greatly.Taking the daytime average temperature of 30 ? as the boundary,the operation mode of the worm bed in the combined process is divided into the high temperature(?30?)anaerobic sidestream reactor(ASSR)operation mode and the moderate temperature(<30 ?)sidestream worm reactor(SSWR)operating mode,select key parameters such as ORP,SRT,DO to optimize the two operating modes.After optimizing the operation mode of the worm bed,the A/O-MBR control system and the A/O-MBR+ worm bed combination system were run in parallel.During the 160-day continuous operation,the worm bed reactor of the combination system went through three successively.Stages: high temperature ASSR mode,transition mode,and moderate temperature SSWR mode.During continuous operation,the removal rate of COD and ammonia nitrogen by the control system andthe combined system is equivalent,and the removal effect of COD and ammonia nitrogen by the combined system at each stage is not much different,and the first-grade A compliance rate of the two effluent water quality indicators is 100 %.The combined system has the best total nitrogen removal effect(53.17%)in the third stage and the best total phosphorus removal effect(86.70%)in the first stage.The total nitrogen removal efficiency during the continuous operation of the combined system was 45.86%,and the total phosphorus removal efficiency was80.97%,which was a significant improvement over the control system.The effluent quality of the sewage treatment system was improved through the coupling of the worm bed reactor.During continuous operation,compared with the control system,the overall sludge reduction rate of the combined system reached 54.76%.The sludge reduction effect of each stage is different under different operating conditions.Compared with the second stage of the worm bed reactor that is also not inoculated with worms,the sludge reduction of the combined system in the anaerobic operation state of the first stage worm bed reactor The volume rate was 49.20%,an increase of 26.00% from the second stage.Compared with the second stage under the same operating parameters of the worm bed,the sludge reduction rate of the combined system inoculated with worms in the third stage worm bed reactor was 71.59%,an increase of 48.39% over the second stage.Under different temperature conditions,enhanced uncoupling(first stage)and enhanced biological predation(third stage)both bring significant sludge reduction effects to the combined system.The coupling of the worm bed reactor effectively reduced the membrane contamination of the A/O-MBR membrane pool.There was no membrane contamination in the combined system that was difficult to remove by chemical cleaning in the control system.In the first stage,the TMP growth rate of the combined system is reduced by 10.70% compared with the control system;in the third stage,the TMP growth rate of the combined system is reduced by 79.11%compared with the control system.It shows that the anaerobic environment and the predation of worms can effectively slow down the membrane pollution.The residual sludge removed by the combined system is superior to the control system in terms of settling performance and dewatering performance.The combined system reduces the difficulty of subsequent concentration and dewatering of the remaining sludge while achieving less sludge discharge.Through a series of sequential batch experiments,the sludge reduction mechanism of the A/O-MBR+worm bed combination process was studied in terms of worm predation,metabolic uncoupling,sludge attenuation,and micro-animal community structure.The direct ingestion of worms on sludge and the enhancement of recessive growth by sludge cracking after ingestion constituted the reduction ofworm predation on sludge.The sludge reduction effect caused by worm predation was 174mg/L/d,accounting for 51.9% of the total sludge reduction effect of the worm bed reactor.The high temperature ASSR mode of the worm bed in the first stage effectively strengthened the metabolic decoupling,and the special aeration mode in the worm bed reactors in the second and third stages also promoted the formation of uncoupling.In the sludge attenuation experiment,it was found that the sludge attenuation phenomenon in A/O-MBR was the most significant in the third stage,and the sludge attenuation phenomenon sent in the worm bed was the most significant in the first stage.Under the long sludge age and low load conditions of worm beds,the types and numbers of other micro-animals that have the ability to feed on sludge have increased to some extent in the combined system.The increase of worms has enhanced this growth effect.In summary,the combined process of A/O-MBR + worm bed realizes the synchronization of sewage treatment and sludge reduction at the pilot level,and it has a lot of room for development in further actual project expansion production.