| As for urban sewage with low C/N, the in-depth study of the impact and its constraints of particulate organic matter in nitrogen and phosphorus removal system is practical significant for using the existing particulate organic matter in sewage efficiently, reducing external carbon dosing, reducing the operating costs and improving the efficiency of nitrogen and phosphorus removal in sewage treatment plant. This paper mainly used SBR process to treat low carbon-nitrogen ratio sewage (C/N=2.5,particulate organic matter concentration is 150-200mg/L), by adjusting the primary sedimentation time, concentration and type of organic matter, to analyze the effect of particulate organic matter on nitrogen and phosphorus removal, the impact on the amount of sludge and apparent sludge yield under different conditions, as well as the impact of the primary sedimentation time on microbial communities, and to provide some theoretical basis of reasonable application and optimal control with particulate organic carbon. The result showed that:1.Particulate organic matter has beneficial effect to improve the effluent quality in SBR reactor for low carbon-nitrogen ratio sewage(C/N=2.5,particulate organic matter concentration is 150-200mg/L). Specific studies are as follow:(1) The change of the primary sedimentation time had no significant effect on the removal of soluble COD,however it impacted on the removal of TN and TP significantly in SBR reactor, which is obvious when the time are 10min and 30min. The results show that:The change of the particle size distribution had no significant effect on the removal of soluble COD; the TN removal rates as the primary sedimentation time were Omin, 10min,30min, 1h,2h of TN removal rate increased by 20%,23%,25%,10%,10% than the control group respectively, and TP removal rate increased by 18%,22%,20%,8%,3%. But with the extension of the settling time, the increase of TN,TP removal rate than the control group were decreasing.(2) The effects of different types of organic on the removal of nitrogen and phosphorus in SBR reactor were different, particulate organic matter can increase the TN, TP removal efficiency distinctly, but the rate increases gradually reduced with the increased concentration of particulate organic matter. The results showed that:when there are different types organic matters and concentrations of POM changed with certain regularity, its soluble COD concentration in effluent remained at about 30mg/L basically.when there were DOM+POM, only DOM, only POM in Influent, the removal rate of TN were 38.36%,36.59%,12.46% and the removal rate of TP were 65.38%,54.56%,53.23% approximately.2.Particulate organic matter has double effects on sludge properties in SBR reactor for low carbon-nitrogen ratio sewage(C/N=2.5,particulate organic matter concentration is 150-200mg/L). that is the adverse effects of the amount of sludge and beneficial effects on the settling properties. Specific studies are as follow:(1) The cumulative production and the specific yield coefficient of sludge increases with the short of influent primary settling time,the average daily amount of sludge increase from 276.22mg to 740.36mg and the specific yield coefficient from 0.520 to 0.562mgMLSS/mgCODcr, while the settling time is shortened from 120min to Omin. After subtracting the corresponding components of the control group, the organic particles adsorbed increments were 0.572g,0.647g,0.827g,1.147g, 2.023g, which accounts 12.59%,14.24%,18.19%,25.23%,44.52% for the MLSS of the control group,as primary sedimentation time were 120min,60min,30min, 10min,0min,As the primary sedimentation time shorted, nitrogen and phosphorus removal is improved in the system, and sludge settling performance has been enhanced,but the amount of sludge also increased at the same time,which was most obvious as the primary sedimentation between Omin and 10min.(2) The presence of dissolved organic matter limited the use of particulate organic matter to a certain extent, so that more unused particulate organic matter present as a whole that directly result of MLSS increases, when there were DOM, DOM+POM, POM, average daily amount of sludge were 114.88mg,367.81mg,205.3mg, in which case they contained Ma+Me 53.76mg,148.81 mg, 93.39mg,and Mi Omg,50.47mg,16.35mg.(3) Regardless of the presence or absence of dissolved organic matter in the water, the higher concentration of particulate organic matter, the more particulate organic matters are adsorbed, the flocs formation are closer and the settling performance are better, but also its daily average of sludge are higher than only DOM in the water,and increase with the increase of POM concentration, when the water is no DOM exist, the Mi increase from 0.383g to 0.823g then to 1.568g,8.0%,which accounts 14.70%,23.5% for the MLSS of the control group respectively as increasing of POM concentration.3.Particulate organic matter was easier to promote enriching microorganisms. Microorganisms In the stable systems cultured by different influent was richer than the original wastewater from treatment plant sludge, the similarity between microorganisms cultured and the original sludge is not high with large changes; Although it was in the same condition, the particulate organic matter in influent was different, bacterial community structure had obvious changes, the microbial similarity was between 43.7% and 86%, and in the similar sedimentation time, the microbial community had higher similarity.4.The distribution of particle size in sewage changed with the primary settling time, primary settling resulted in high removal capacity on COD and SS,the distribution of particle size changed obviously within 30 min and then become relatively slow after 30 min.COD and SS removal rates were 50.15% and 64.23% respectively after 2h precipitation. |
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