| With the continuous improvement of environmental standards,the energy consumption in wastewater treatment is increasing,so the energy saving and consumption reduction of wastewater treatment is particularly important.However,the traditional sewage treatment process has the problems of high energy consumption,the need for an additional carbon source,and difficulty in sludge disposal.In recent years,the emerging energy-saving sewage treatment process has attracted more and more attention,especially the anaerobic ammonia oxidizing bacteria.The main autotrophic denitrification process,the autotrophic denitrification technology mainly based on anaerobic ammonia oxidation,can save a large amount of aeration and carbon source.However,the low concentration and temperature changes of urban sewage have inhibited the engineering application of autotrophic denitrification process.A biological filter with biological interception function was used to start the autotrophic denitrification process,and the operational status of gas-water ratio and other parameters were studied.As the front-end pretreatment of autotrophic denitrification process to remove organic matter in water,anaerobic treatment process with the advantages of low energy consumption,less residual sludge,simple operation and maintenance can convert organic matter into clean energy methane,and realize the transformation of sewage from energy consumption to production capacity.A biofilter treating actual municipal sewage was applied to research the anaerobic methanogenesis in a pilot-scale reactor.The method of the rapid start-up,the influence of temperature and HRT and the change of the microbial structure on reactor were investigated in the pilot-scale study.The results showed that the rapid start-up of biofilter reactor was achieved by the combination of intermittent and continuous operation.And the effluent concentration of SCOD was about 60mg/L at the stable operation stage.The biofilter was operated steadily at the temperature higher than 14℃,the accumulation of volatile fatty acids(VFA)was low,and the effluents of SCOD and TCOD were 69mg/L and 90mg/L,repectively.In addition,the metabolism of hydrolysis and methanogenesis tended to balance under such condition.However,the abundances of microorganism that can hydrolytze organic matter and product methane both decreased.The abundances of Peptostreptococcaceae increased even temperature was lower to 10℃,which can produce VFA.Therefore,the concentration of effluent VFA and TCOD was incerased,but the methane productionwas decreased.And the effluent concentration of SCOD is relatively.The microbial abundance and diversity were richest at the temperature of 19°C in the reactor.And the acetoclastic methanogen were the dominant methanogens at low temperature.HRT was 8h and 4h,and the removal of SCOD and TCOD by anaerobic biological filter system was stable.HRT was 3h,and the effluent quality of the anaerobic biological filter fluctuated.After 10 days of operation,the effluent COD and SCOD gradually recovered to 70mg/L and 100mg/L.The metabolism of hydrolytic acidizing bacteria and methanogenic bacteria is relatively balanced,and the system runs well.Methanosaetaceae is the dominant genus.When HRT was 4h,the anaerobic biofilter system had the best effect on SCOD and TCOD removal,and the methanogenic capacity of the system increased with the decrease of HRT.The methanogenic pathway is mainly based on the acetic acid type methanogenic pathway.The autotrophic nitrogen removal biological filter was started in a step-by-step manner,and the anaerobic ammonia oxidation(An AOB)biological filter was started at room temperature.In the anaerobic ammonia oxidation stage,the total nitrogen removal rates at different periods were 55%,24%and 75%,respectively.Then,a small amount of nitrification sludge was inoculated to achieve autotrophic nitrogen removal,and the total nitrogen removal rate was maintained at 60%.When the gas-water ratio was 1:1 and HRT was 5h,the removal rate of ammonia nitrogen in the autotrophic filter decreased to 48%,but the effluent nitrate concentration decreased to 2mg/L,the total nitrogen removal rate remained at 48%,and the activity of AOB bacteria in the system decreased.Gas-water ratio is a key operating parameter in the operation of the autotrophic nitrogen removal filter.When the gas-water ratio is 4:1,the ammonia removal effect of the filter is better,and the total nitrogen removal rate increases to60%.The pilot anaerobic-autotrophic combined biological filter was used to treat the actual sewage of the urban sewage treatment plant.The feasibility of the anaerobic-autotrophic combined biological filter to treat urban sewage was studied.The anaerobic filter mainly removes organic matter in the sewage,and the autotrophic nitrogen removal filter mainly removal nitrogen.The average SCOD concentration of the effluent is 42 mg / L,and the average total nitrogen removal rate is 60%.The operating parameters of the combined filter are optimized under low temperature conditions.With the decrease of temperature,the HRT of the anaerobic biological filter was 4h,5h and 8h,and the HRT of the autotrophic filter was 5h,6h and 10 h,respectively.When the temperature was above 10℃,the effluent SCOD was 42mg/L,the total nitrogen removal rate could reach 75%,and the effluent ammonia nitrogen was less than 10mg/L.However,when the temperature continues to drop below 10℃,it is difficult to maintain the stability of the system operation.Low temperature conditions inhibit the nitrification reaction,and the effluent ammonia nitrogen concentration increased.The main An AOB genus in the system is Candidatus＿Brocadia,the main genus of AOB is Nitrosomonas,and the main genus of NOB is Nitrospira.The changes of AOB and NOB are related to the filter treatment effect.Methyloparacoccus methanogens may be involved in the nitrogen removal pathway,which is the reason for the lower nitrate output in the system. |
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