DO浓度对EBPR耦合SND处理低C/N污水的影响

Effect of DO concentration on the combination of EBPR and SND for low C/N sewage treatment

为了解厌氧/好氧运行的序批式反应器(SBR)中,强化生物除磷(EBPR)与同步硝化反硝化(SND)的耦合脱氮除磷特性,以实际低C/N(约为3.5)生活污水为处理对象,先通过调控进水C/N考察其对EBPR启动和聚磷菌(PAOs)富集情况的影响,再通过调控好氧段DO浓度考察其对系统脱氮除磷性能、SND率及碳源转化特性的影响.结果表明,DO浓度为2.0mg/L,当进水C/N由3.2提高至7.5并降至3.8时,反应器出水PO_4^(3-)-P浓度由3.9mg/L逐渐降至0.5mg/L以下,且厌氧释磷量(PRA)由3.3mg/L逐渐升高至约30mg/L.此后,当DO浓度逐渐降至约1.0mg/L时,SND现象愈加明显,且其与EBPR耦合使得系统总氮(TN)和PO_4^(3-)-P去除率分别提高至85%和94%.但当DO浓度约为0.5mg/L时,硝化过程进行不完全,亚硝酸盐积累较为明显,耦合系统中存在同步短程硝化反硝化现象.DO浓度为约1.0mg/L时,系统具有最高的脱氮除磷性能.此外,当DO浓度由2.0mg/L降至0.5mg/L时,PAOs较聚糖菌(GAOs)在厌氧内碳源储存中的贡献逐渐减小(PPAO,An由30.3%逐渐降至20.2%),PRA降低约7mg/L.DO浓度为1.0~1.5mg/L最有利于系统厌氧段内碳源PHA的合成.

This study focused on investigating the nitrogen （N） and phosphorus removal characteristics of a combined enhanced phosphorus removal （EBPR） with simultaneous nitrification and denitrification （SND） process. An anaerobic/aerobic operated sequencing batch reactor （SBR）, fed with actual domestic sewage at a low carbon/nitrogen ratio （C/N, around 3.5）, was studied firstly for the start-up of EBPR and the enrichment of phosphorus accumulating organisms （PAOs） by adjusting the influent C/N, and lately for the nutrient removal performance, SND efficiency, and carbon sources conversion by adjusting the dissolved oxygen （DO） concentrations at the aerobic stage. Results showed that at DO concentration of around 2.0mg/L and influent C/N increased from 3.2 to 7.5and then recovered to 3.8, effluent PO43--P concentration gradually decreased from 3.9mg/L to below 0.5mg/L accompanied by the increase of anaerobic phosphorus release amount （PRA） from 3.3mg/L to approximately 30mg/L. Hereafter, when DO concentration gradually decreased to about 1.0mg/L, SND became obvious, and its coupling with EBPR increased the total nitrogen （TN） and PO43--P removal efficiencies to 85% and 94%, respectively. But when the DO concentration was continued decreased to about 0.5mg/L, nitrification became incomplete and nitrite accumulation became obvious, indicating the existence of simultaneous partial nitrification and denitrification. The results indicated that the combined system has the highest nitrogen and phosphorus removal performance at DO concentration of about 1.0mg/L. In addition, when DO concentration decreased from 2.0mg/L to 0.5mg/L, the contribution of PAOs to the storage of anaerobic intracellular carbon sources （PPAO,An） gradually reduced from 30.3% to 20.2%, resulted in a decrease of PRA for about 7mg/L. DO concentration of 1.0~1.5mg/L was the most conducive to the synthesis of carbon source PHA in the anaerobic stage of the combined system.