Research On Start-up And Treatment Efficiency Of A Down-flow Anaerobic Biofilm Reactor

Traditional anaerobic reactors are susceptible to loss of organisms under impact loads.It is necessary to develop an anaerobic reactor that can maintain high biomass in the system while meeting the requirements for efficient and stable operation,providing new technical ideas and theoretical basis.In this study,a down-flow anaerobic biofilm reactor based on suspended packing was selected as the research object,and highconcentration sucrose wastewater was used as test water to examine the treatment efficiency of the anaerobic reactor under different startup conditions,and the effects of the hydraulic retention time(HRT),the reflux ratio,alkalinity,temperature on the operating performance of the reactor were investigated.The research found that the reactor has good treatment efficiency for highconcentration organic wastewater in the form of pushing flow and exhibits better impact load resistance,which is more convenient than traditional anaerobic process in start-up and operation management.The anaerobic biofilm formed on the surface of the filler has obvious succession pattern to adapt to different substrates and environmental factors.It was found that the use of aerobic precoating can speed up the biofilm culturing process,for an improved filler surface was formed by microbial communities.In the start-up of reactor in low volumetric loading,the initial volume load was 0.8kg COD/(m3·d),and the final volume load achieved 9.66 kg COD/(m3·d),and the average effluent COD was 566.05 mg/L,COD removal rate stabilized at 80%~85%.In the secondary start-up of the reactor in volumetric loading,the initial volume load was 4.49 kg COD/(m3·d),and the volume load can be restored to 8.99 kg COD/(m3·d)or more in 2 weeks.During the study period,the reactor showed good impact load capacity.The best operating parameter are: the influent COD?3000mg/L,T=30°C,HRT=8h,R=1:1,and the total alkalinity of influent is 20mmol//L.Under this operating condition,the average COD removal rate is 89.73%,and the average COD removal load rate is 8.10 kg COD/(m3·d),and the average p H of the effluent is 6.985,and the average total alkalinity is 20.475 mmol/L,and the average bicarbonate alkalinity is 8.352mmol/L,and the average VFA is 5.049mmol/L,and the average methane yield is 0.24LCH4/kg COD.The fillers in different positions in the reactor diversed in morphology and appearance,and the biomass on the fillers gradually increased from top to bottom.The microbial community structure analysis of the biofilm showed that upper fillers had fewer microbial communities but higher population diversity,while the biofilm of lower fillers grew significantly better.Further study found that,compared with inoculated sludge,the Methanothrix and Methanospirillum became dominant bacteria in the biofilm,and their abundance increased respectively from 20.37% and 5.27% to 58.43% and 33.64%,both of which coordinate the use of substrates to jointly complete the methanogenesis process.Compared top fillers,the abundance of acid nutritional methanogen in biofilms of bottom fillers decreased,while the abundance of hydrogenotrophic methanogen increased,which changed respectively from 63.28% and 32.20% to 58.43% and 36.63%.