| At present,excess sludge treatment has been the improtant restriction for solving in wastewater biological treatment technology.The way to solve the problem also has been one of the urgent problems in wastewater treatment industry.Sludge reduction techology,the best choice for solving the problem at the source,has been gained great attentions.Anoxic-oxic-settling-anaerobic?A-OSA?process could reduce the sludge production and remove pollutants of wastewater without chemicals,but not ideal for removal of nitrogen and phosphorus.In the paper,the A-OSA process strengthened by the composite humic biological filler is A-OHASA process.With the reference of A-OSA process,the efficiency of sludge reduction and wastewater treatment of A-OHASA process were studied.The operation efficiency and sludge characteristics were studied at various operating conditions.The effect of the composite humic biological filler and the microbiological mechanisms was studied in A-OHASA process.In order to improve the operation and control of A-OHASA process,the operation efficiency of A-OHASA process at various conditions was studied.The results showed that the A-OHASA process can reduce the excess sludge and get a good effect on the nitrogen and phosphorus removal with the effect of composite humic biological filler.When the hydraulic retention time of the slduge anaerobic reaction tank was 5.5h,the result of the A-OHASA process was the best.The sludge observed yield was 0.13 g MLSS/g COD,the sludge production reduced by 23.18%.The average removal efficiencies of COD,NH4+-N,TN and TP was 92.69%,91.90%,76.69% and 92.19%,respectively.The slduge production and removal efficiency of COD were not affected by variation of water temperature and organic loading.The sludge retention time?SRT?made no effect on the removal efficiencies of COD.The negative correlation was between the SRT and excess sludge production.When pH is lower for restricting microbial synthesis and leading to less sludge production.When the pH increased from 5.5 to 8.5,the removal efficiency of COD stayed above 85%.The removal efficiency of NH4+-N and TN increased by 9.57% and 18.89%,respectively.The removal efficiency of TP increased from 86.15% to 92.92%,and then decreased to 90.75%.In order to investigate the mechanisms of sludge reduction in A-OHASA process,the humic-activated sludge characteristics was studied.The reserach results showed that SVI and CST of A-OHASA process was 72.1mL/g and 15.9s,reduced by 21.0% and 26.7%,respectively.Settleability and dehydration property of humic-activated sludge in A-OHASA process was improved.The results of SEM-EDS showed that the frame work of activated sludge was filamentous bacteria in A-OHASA process,and was closer than the A-OSA process.The sludge microstructure and elemental composition was improved with the effect of composite humic biological filler.They all were more beneficial to improving the settleability and dehydration property of humic-activated sludge in A-OHASA process.The analysis results of EPS showed that the EPS proportions of the main reaction tanks in A-OHASA process were lower than A-OSA process.It indicated that the activated sludge elments,performances and microbial community structures,metabolic pathways were changed with the effect of composite humic biological filler.It was beneficial to improving the sludge reduction efficiency and settleability.According to the law of conservation of mass and energy,sludge calorific values,sludge production and COD variation of influent and effluent at various conditions showed that decay rate and degree of sludge was higher in A-OHASA process than A-OSA process at the sludge anaerobic reaction tank.Energy uncoupling was effected at the sludge anaerobic reaction tank in A-OHASA process.So,the sludge reduction efficiency of A-OHASA process was better than A-OSA process.In order to study the the effect of composite humic biological filler on sludge reduction,nitrogen and phosphorus removal in A-OHASA process with the Miseq high-throughput sequencing technology.The reserach results showed that the OTU of the anoxic,oxic and sludge anaerobic reaction tank in A-OHASA process were 798,553 and 453,respectively.Chao indexes were 945.01,668.81 and 517.88,respectively.Shannon indexes were 4.82,4.48 and 4.23,respectively.So microbial abundance and diversity of A-OHASA process were changed with the effect of composite humic biological filler.The microorganisms of both processes were attributable to 11 phylums,and Proteobacteria,Bacteroidetes,Chloroflexi and Spirochaetae were dominant floras.Burkholderiales and Flavobacteriales proportions of A-OHASA process were higher than A-OSA process.It indicated that nitrogen and phosphorus removal capacities were improved and sludge production reduced in A-OHASA process with the effect of composite humic biological filler.The lower Saprospiraceae proportion was beneficial to improving the settleability of humic-activated sludge in A-OHASA process.The higher Hydrogenophaga and Flavobacterium proportions leaded to improve the pollutants removal capacities at low temperature in A-OHASA process. |
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