Study On The Performance And Sludge Characteristics Of Rural Domestic Sewage Treatment By Hybridized Anaerobic Baffled Reactor

With the economic development of China,living standard of rural residents has been significantly improved,along with growing discharge of rural domestic sewage.Focusing on rural domestic sewage treatment,the enhancement of nitrogen removal by hybridized ABR,and the performance and operating characteristics of hybridized ABR-vegetation buffer strip were investigated in this study.The C/N removing features of hybridized ABR were analyzed through EPS content measurement and EEM fluorescence spectrometry,and the identification of microbial community.The results were as followed:The hybridized ABR was started under fixed HRT and organic loading.The CODcr removing rate remained stable after the 45th day.With intermittent aeration,high nitrogen removing efficiency was attained through raising ammonia loading and prolonging HRT.Then the ammonia loading was changed back to 50 mg/L with the HRT adjustment accordingly,which led to the effective nitrogen removal from rural domestic sewage.The hybridized ABR had been runned for 384 days.The effluent from hybridized ABR-vegetation buffer strip met the first grade A discharge standard of pollutants for municipal wastewater treatment plant in China.Besides,for synthetic rural domestic sewage,the operating parameters were finally determined as follows:the HRT in aerated compartments was 16 h(the HRT of hybridized ABR was 48 h),the DO concentration was 0.7?1.5 mg/L(the aeration circle was aerating for 30 s and none-aerating for 4-5 min),the temperature in the hybridized ABR was 31?,the HRT of vegetation buffer strip was 96 h.Under these parameters,the CODCr and TN concentration in the effluent from hybridized ABR were 17.05 mg/L and 15.01 mg/L with no TP removal,and the TN and TP concentration decreased to 0.78 mg/L and 0.40 mg/L in the final effluent from vegetation buffer strip.In addition,The CODCr removing rate in hybridized ABR remained beyond 90%,with most organics degraded in compartment I.The TN removing rate finally leveled out around 62%.The denitrification in the hybridized ABR might be mainly ascribed to simultaneous nitrification-denitrification or simultaneous shortcut nitrification-denitrification.Furthermore,the vegetation buffer strip could remove 95%TN and 92%TP in the effluent from hybridized ABR.The nutrient condition was better in front compartments than rear ones in the hybridized ABR,which led to larger sludge floc size and higher organic content in front,while severe sludge disruption occurred at rear.Floc size in each compartment decreased as the operating period extension.Besides,due to lack of organic carbon source,EPS was consumed by denitrification in rear compartments,and the EPS content was obviously lower than front compartments.The concentrations of typical organics in EPS were found to be increasing in the order of protein,humic acid,and polysaccharide,with most organics concentrated in TB-EPS rather than LB-EPS and slime.Based on the FRI analysis,the concentrations of typical organics in EPS were found to be increasing in the order of tyrosine,tryptophan,soluble microbial byproducts,fulvic acid,and humic acid.In addition,Ca,Al,and Fe contents were high in sludge of each compartments,and the total element content in sludge of compartment ? remained the highest in the hybridized ABR.The varieties of bacteria were more abundant than archaea in the hybridized ABR.The main kinds of bacteria were Proteobacteria,Chloroflexi and Bacteroidetes,including many denitrifying bacteria(14%were autotrophic denitrifying bacteria).The highest relative abundance of denitrifying bacteria was observed in compartment ? and ? around 50%.These identification results of bacterial community supported the occurrence of simultaneous nitrification-denitrification or simultaneous shortcut nitrification-denitrification,and autotrophic denitrification also contributed.Besides,obvious differences of bacterial community were observed between aerated compartments and anaerobic compartments,and some methanogenic archaea were found in anaerobic compartments.In addition,many filamentous bacteria such as 021N and methanothrix soehngenii were observed in the hybridized ABR due to low DO concentration,along with clostridium,Thiobacillus and some coccus.The amounts of filamentous bacteria decreased from the front compartments to the rear,with coccus and bacillus mainly distributed at rear.The species of microbes were most abundant in the aerated compartments among the hybridized ABR.Furthermore,many disrupted microbes were observed in each compartment,especially compartments ? and ?.Based on the lab-scale experiment result,the hybridized ABR-vegetation buffer strips process has been designed for treating rural domestic sewage from individual families(3?6 people)or small hotels(40 people)in the surrounding areas of Erhai Lake,and the corresponding drawings and calculation manuals for every operational unit of hybridized ABR and vegetation buffer strips have been provided in Appendix of this thesis.