Coagulation Combined With ASBR System For Treatment Of Mechanical Dewatering Wastewater From Municipal Gabarge

Mechanical dewatering wastewater?MDW?is squeezed by high-pressure mechanical process from fresh municipal solid waste?MSW?that is not subjected to ferment.This MDW is characterized as a complex mixture with high organic,suspended solids?SS?and ammonia content,and large flow-rate fluctuation.In the present work,a hybrid process involving alkali treatment,coagulation-sedimentation,and anaerobic treatment,was developed to remove organic substances and SS from MDW,during which the effects of operational condition parameters were evaluated to optimize the process operation.The obtained results are important to guide the treatment of MDW and its practical application.The effectiveness of alkali-coagulation process on the removal of SS and organic matter from MDW was investigated.The results displayed that the optimum p H for alkali treatment was 9.0,and more than 82% SS and 11% COD were removed stably.Polyaluminum chloride?PAC?was selected as an effective coagulant to enhance organics and SS removal,and the optimal operational condition parameters were 200 mg/L Ca?OH?₂,10.0 p H,800 mg/L PAC addition respectively,and the stirring condition of 250 r/min for 1 min followed by 50 r/min for 10 min,which resulted to the maximum SS and COD removal efficiency of 87% and 15%,respectively.Moreover,the combination o f alkali-coagulationsedimentation process could also remove a certain amount of heavy metals from MDW.The removal efficiency of the organic matter and methane production capability in the mesothermal anaerobic sequencing batch reactor?ASBR?to treat MDW was also evaluated.The ASBR could be quickly start-up after more than 28 days with a synthetic influent COD of 12 000 mg/L,after which the maximum COD removal efficiency of above 97% could be obtained.Upon the steady-state of the ASBR,with a real MDW as inlet with the COD concentration ranged from 9 000 to 20 000 mg/L,the COD removal efficiency could be stably kept around 94%,and the p H and generated volatile fatty acids within the ASBR bulk was maintained at a relative low concentration that have in significant effect onto the system performance.The methane yield in ASBR fed with real MDW positively correlated with the influent COD,and the average biomass yield of the mesothermal ASBR was about 0.09 kg VSS/kg COD.It was estimated that up to 13 m³ biogas would be produced stably as treating one cubic meter of wastewater.Thus,the optimum operational condition parameters of ASBR could be achieved as an operational temperature of 35?,an intermittent stirring mode of 5 min/30 min and an organic loading rate of 6.0 kg COD/?L·d?.Meanwhile,it was observed that the existence of high ammonia and a certain amount of heavy metal in MDW influent did not affect the ASBR treatment capability and the activities of anaerobic microbes.The characteristic of microbial community structure and bacterial population in the ASBR treating MDW,and their changes under varied operational temperature were examined by using q PCR and high-throughput sequencing.It was observed that the proportion of archaea in mesothermal ASB R increased with the increase of organic loading rate and temperature,and the accumulation rate of functional microbes in ASBR was significant that is beneficial to the system stability and effectiveness,indicating the ASBR is a feasible process to treat MDW with a stably high organic removal and methane generation rate.