Study Of SBBR Process Performance And Affectting Factors Under Low Temperature Condition

In cold regions,the biological treatment processes used in municipal wastewater treatment plants face the problem of difficult nitrogen removal under low temperature conditions in winter,making it difficult to achieve long-term stable discharge standards.In order to improve the nitrogen removal capacity of the biological treatment system under low temperature conditions,this project constructs a dual sludge SBBR system with the coexistence of biofilm sludge and activated sludge by adding biofilm filler to the intermittent sequencing batch reactor（SBR）,and selects influencing factors such as filling rate,influent organic matter concentration,influent ammonia nitrogen concentration,influent TP concentration and pH value to investigate the influence of each influencing factor on the SBBR process under low temperature conditions.The effect of the factors on the pollutant removal efficiency of the SBBR process under low temperature conditions was investigated,and the changes of microbial community structure and their dominant groups in the SBBR reactor under low temperature conditions were also investigated with the help of high-throughput sequencing technology.The aim is to provide a theoretical basis and scientific guidance for the design of the SBBR process under low temperature conditions,and to provide a comprehensive understanding of the diversity and degradation characteristics of microorganisms in the SBBR process under low temperature conditions.After comparing the three types of fillers,namely polyurethane sponge filler,polyethylene filler and multi-faceted hollow sphere filler,the polyurethane sponge filler was better than the other two fillers in terms of pollutant removal and biofilm properties,and the removal efficiency of the system was better when the filling rate was 15%,and the removal rate could reach more than 90%,and the nitrification rate of the system was faster,the degradation rate of the NH₄⁺-N was 0.26mg/（L·min）.It was observed by SEM that at 15%filling rate,the spatial sense of suspended sludge was obvious,and there was pore structure in the sludge,which was conducive to the transfer of dissolved oxygen and organic matter,and the number of biofilm sludge flora increased significantly and the flora was dense.The abundance of Dechloromonas increased with increasing filling rate and became the dominant genus.The SBBR system has a high resistance to shock loading at different concentrations of organic matter in the influent water and has a high degradation rate of COD,with a degradation rate of over 85%.At the same time,the system also has a good effect on the removal of TP,with the removal rate reaching more than 87%.However,the nitrogen removal capacity is obviously different under different influent organic matter concentrations.When the influent organic matter concentration is300mg/L and 800mg/L,the NH₄⁺-N and TN removal rates are above 90%,and the system has the fastest nitrogen degradation rate when the influent organic matter concentration is 800mg/L.However,the NH₄⁺-N and TN removal rates were only73.49%and 64.56%at the influent organic matter concentration of 150 mg/L.By SEM,it was observed that the activated sludge structure was compact and spherical bacteria were the dominant flora at influent organic matter concentrations of 300mg/L and 800 mg/L,and the spherical bacteria increased at influent organic matter concentration of 800 mg/L.In combination with high-throughput sequencing analysis,the abundance of Dechloromonas increased gradually with the increase of influent organic matter concentration and became the absolute dominant genus,which was conducive to improving the denitrification and phosphorus removal capacity of the system.The system has good degradation effect on both COD and TP at different influent ammonia nitrogen concentrations,and the removal rate of COD can reach more than90%,and the removal rate of TP ranges from 88%to 93%.However,the removal rates of NH₄⁺-N and TN by the system decreased with the increase of influent ammonia nitrogen concentration.When the influent ammonia nitrogen concentration was 15mg/L,24mg/L and 32mg/L,the removal rates of NH₄⁺-N and TN were 99.70%,99.78%,77.97%and 93.71%,91.96%and 72.38%respectively.The presence of some bacilli in the activated sludge was observed by SEM at influent ammonia nitrogen concentrations of 24 mg/L and 32 mg/L.Combined with high-throughput sequencing analysis,the relative abundance of Rhodoferax bacteria gradually increased with increasing influent ammonia nitrogen concentration and became the dominant genus.At different influent TP concentrations,the SBBR system had good removal efficiency for both COD and NH₄⁺-N.The COD degradation rate could reach over90%and NH₄⁺-N removal rate could reach over 98%.However,when the influent TP concentration increased from 4.5mg/L to 8mg/L,the system’s TP removal rate decreased from 92.58%to 48.44%.Meanwhile,the removal rate of TN by the system decreased with the increase of influent TP concentration,and the removal rate decreased from 93.71%to 88.15%.It was observed by SEM that the activated sludge had a dense structure with pore structure and the number of rod-shaped bacteria increased with increasing influent TP concentration,and Rhodoferax became the absolute dominant genus with increasing influent TP concentration.The SBBR system was highly adaptable to pH changes,and the degradation rate of all pollutants was around 90%at different pH values.However,the degradation rate of NH₄⁺-N was slightly higher at pH 8 and 9 than at pH 7.It was observed by SEM that at pH 8,the activated sludge had a compact structure with obvious spatial structure and cavity structure in the sludge.Combined with high throughput sequencing analysis,the abundance of denitrifying phosphorus removing bacteria Rhodoferax was significantly increased at pH 8 and was the absolute dominant genus.