进水C/P对SNEDPR系统脱氮除磷性能的影响

为了解不同进水C/P条件下同步硝化内源反硝化除磷(SNEDPR)的脱氮除磷特性.以实际城市污水为处理对象,采用延时厌氧(180 min)/低氧(溶解氧0.5~1.0 mg·L~(-1))运行的序批式反应器(SBR),考察了进水C/P(分别为60、30、20、15、10)对系统C、N、P去除特性的影响.结果表明:适当降低进水C/P(由60降至30)有利于提高系统内PAOs竞争优势.当C/P为30时系统除磷性能最高,厌氧段释磷速率(PRR)和好氧段吸磷速率(PUR,以P/MLSS计,下同)分别高达3.5mg·(g·h)-1和4.2 mg·(g·h)-1,出水PO3-4-P浓度均低于0.3 mg·L~(-1),且PPAO,An高达88.1%;但进一步降低进水C/P至10时,PO3-4-P去除率和PPAO,An分别由38.1%和82.4%降低至3.1%和5.3%,PRR和PUR分别仅为0.2 mg·(g·h)-1和0.24mg·(g·h)-1,系统表现出较差的除磷性能.降低C/P对系统COD去除性能没有影响,COD去除率稳定在85%左右.此外,当C/P由60降低至20时,系统硝化性能变差,表现为出水NH+4-N和NO-2-N浓度分别由0和6.9 mg·L~(-1)升高至5.1 mg·L~(-1)和16.2 mg·L~(-1);而当C/P进一步降低至10时,系统硝化性能得以恢复,但亚硝积累特性遭到破坏,表现为出水NH+4-N和NO-2-N浓度逐渐降低为0,但出水NO-3-N浓度由0.08 mg·L~(-1)升高至14.1 mg·L~(-1).SNED率先由62.1%降低为36.4%后又逐渐提高至56.4%.C/P低于15时,有利于提高GAOs的竞争优势,且C/P由20降至10时系统脱氮性能得以恢复,原因在于GAOs内源反硝化作用的增强.

Effect of the Influent C/P Ratio on the Nutrient Removal Characteristics of the SNEDPR System

This study focuses on the nitrogen (N) and phosphorus (P) removal characteristics in a simultaneous nitrification-endogenous denitrification and phosphorus removal (SNEDPR) system at different influent C/P ratios. An extended anaerobic/low aerobic (dissolved oxygen:0.5-1.0 mg·L^-1) sequencing batch reactor (SBR) fed with municipal sewage was studied by adjusting different C/P ratios (10, 15, 20, 30, and 60). The experimental results show that the proper reduction of the influent C/P ratio (C/P ratio reduced from 60 to 30) enhances the competitive advantages of phosphorus-accumulating organisms (PAOs) in the SNEDPR system. The highest phosphorus removal efficiency was achieved at a C/P ratio of 30, with the anaerobic phosphorus release rate (PRR) and aerobic phosphorus uptake rate (PUR, used as P/MLSS) reaching 3.5 mg·(g·h)^-1 and 4.2 mg·(g·h)^-1 respectively, and an average effluent PO₄^3--P concentration below 0.3 mg·L^-1. The percentage of PAOs contributing to the storage of endogenesis carbon (P_{PAO, An}) reached 88.1%. However, a poor phosphorus removal performance was observed with further reduction of the influent C/P ratios to 10; both the PO₄^3--P removal efficiency and P_{PAO, An} decreased from 38.1% and 82.4% to 3.1% and 5.3%, respectively. The PRR and PUR were 0.2 mg·(g·h)^-1 and 0.24 mg·(g·h)^-1, respectively. The COD removal performance was not affected by the decreasing influent C/P ratios; the average COD removal efficiency stabilized at 85%. In addition, the nitrification performance became worse with decreasing C/P ratios (from 60 to 20) because the effluent NH₄⁺-N and NO₂^--N concentrations increased from 0 and 6.9 mg·L^-1 to 5.1 mg·L^-1 and 16.2 mg·L^-1, respectively. The nitrificaton performance recovered when the C/P ratios further decreased to 10, but the nitrite accumulation was disturbed as both the effluent NH₄⁺-N and NO₂^--N concentrations reduced to 0. The effluent NO₃^--N concentration increased from 0.08 mg·L^-1 to 14.1 mg·L^-1. The SNED efficiency first decreased from 62.1% to 36.4% and then increased to 56.4%. The advantageous competition of glycogen accumulating organisms (GAOs) improved when the influent C/P ratio was lower than 15. The enhancement of the endogenous denitrification ability of GAOs might explain the recovery denitrification performance of the system when the influent C/P ratios decreased from 20 to 10.