Performance Of SBR Reactor Treating Domestic Wastewater Under Low Temperature With Bioaugmentation

Low temperature is a key environmental factor which affects the treatment efficiency of wastewater biological nitrogen removal by restraining the growth and metabolic activity of nitrifying consortium and denitrifying consortium in activated sludge. Many wastewater treatment plants in Chinese northern area failed in the initialization phase in winter which caused the effluent quality could not meet the emission standard of China. In view of characteristics of sewage biological nitrogen removal under low temperature, this article focused on the bioaugmentation method and the biological nitrogen removal efficiency under low temperature. Psychrotolerant nitrogen removal consortiums which have outstanding performance of nitrogen removal were obtained by continuous enrichment and domestication under 10? for long periods.Then autotrophic bioaugmentation method and heterotrophic bioaugmentation method were used separately to investigate the efficiency influence and the transformation rule of bioaugmentation technology using in SBR treating the domestic sewage under low temperature. It can provide us a new idea to solve the choke point of biological nitrogen removal under low temperature at this stage.The autotrophic inoculant consisted of a psychrotolerant ammonia oxidizing consortium and a psychrotolerant nitrite oxidizing consortium, which were successfully obtained by continuous orientation enrichment and domestication from activated sludge.They had well performance of psychrotolerant growing ability and outstanding performance of degrading property of treating ammonia nitrogen and nitrite nitrogen under low temperature which could adapt to diverse concentrations of target objects.The heterotrophic inoculant consisted of a psychrotolerant domestication consortium which had outstanding performance of heterotrophic nitrifying and aerobic denitrification ability. It was obtained by an exclusive domestication device and its removal rate of the ammonia nitrogen, total nitrogen and TOC in the domestication medium reached over 99%,over 90% and over 98% respectively while there was no nitrite nitrogen accumulation happening in the effluent.By adding the activated sludge directly, two identical SBRs completed their initialization phase successfully after 45 days and they kept in stable effluent quality which were ammonia nitrogen 8-9 mg/L, nitrite nitrogen 0 mg/L, nitrate nitrogen 10-12 mg/L, total nitrogen 18-20 mg/L and CODcr 40-45 mg/L. With the autotrophic bioaugmentation method applied into the 2#SBR for a period of 40 days while the 1#SBR was kept as a control, the removal rate of ammonia nitrogen rose by 5%-6%, the nitrite nitrogen showed no accumulation, the nitrate nitrogen concentration rose by 3-6 mg/L while the removal rate of total nitrogen and CODcr both showed an obvious decline which made them fail to meet the emission standard. After the bioaugmentation stopped,the previous added inoculants were washed out gradually which caused effluent qualities of the two SBRs were nearly the same. It indicated that the autotrophic bioaugmentation method could promote the removal of ammonia nitrogen but could not meet the need of removal of nitrogen and organic pollutants.With the heterotrophic bioaugmentation method applied into the 2#SBR for a period of 40 days while the 1#SBR was kept as a control, the removal rate of ammonia nitrogen rose by 10%-15%, the nitrite nitrogen showed no accumulation, the nitrate nitrogen concentration declined by 4-7 mg/L, the removal rate of total nitrogen rose by 25%-30% while the concentration of CODcr declined by 5-10 mg/L, which the ammonia nitrogen, the total nitrogen and CODcr could all meet the emission standard. After the bioaugmentation stopped, the previous added inoculants could also remain in the system and had a bioaumentation effect which improved the effluent qualities of the 2#SBR for a long time. It indicated that the heterotrophic bioaugmentation innoculant could overcome the shortages of directly adding the pure bacterial strain such as losing through the effluent easily and growing with a declined activity, which consisted of psychrotolerant hetrotrophic nitrfying and aerobic denitrification domestication consortium and polyurethane foam which acted as immobilization carriers. Finally the heterotrophic bioaugmentation method had a promising potential to improve the treat effiency of wastewater treatment application.