摘要
亚硝酸盐型反硝化除磷工艺具有运行周期短,吸磷速率快的特点。联合亚硝酸盐型硝化技术,就可以实现两段活性污泥系统—短程反硝化除磷工艺。而目前将亚硝酸盐作为反硝化除磷过程的电子受体尚存在诸多问题,如亚硝态氮对缺氧吸磷的抑制程度,亚硝酸态氮对缺氧吸磷的抑制机理,亚硝酸型反硝化除磷的反应动力学等都是亟待研究的课题。本研究采用SBR反应器,对比采用不同方式培养驯化短程反硝化除磷污泥的效果,并启动间歇式短程反硝化除磷工艺;考察了污泥龄(SRT)、亚硝酸盐浓度、碳源有机物和pH值等对短程反硝化除磷工艺的影响,同时测定了间歇式短程反硝化除磷动力学参数。主要研究成果如下:
1)采用PAOs启动短程反硝化除磷工艺的方法未能获得理想的脱氮除磷效果。采用厌氧/沉淀排水/缺氧/沉淀排水的方式以亚硝酸盐为电子受体直接驯化与富集短程反硝化除磷污泥,经58d成功富集短程反硝化除磷污泥,COD去除率达75.4%,PO_4~(3-)-p去除率达81.8%,NO_2~--N去除率达97.4%,此时污泥呈黑褐色絮状污泥,污泥状态良好,对反应器内较高的亚硝酸盐环境适应性好。
2)通过测定缺氧段电子受体的产能氧化效率k_(NO)、呼吸效率η_(NO)与除磷量/亚硝酸盐消耗量可评估系统的反硝化除磷能力,判别反硝化除磷工艺运行的可行性。采用PAOs所诱导驯化获得的短程反硝化除磷菌缺氧段电子受体的平均产能氧化效率(?)为27.1%,平均呼吸效率(?)为9.4%。采用亚硝酸盐直接驯化富集的短程反硝化除磷菌平均产能氧化效率(?)为39.3%,平均呼吸效率(?)为9.2%。在适当的工艺运行条件下,后者可保证系统长期稳定的脱氮除磷效果。
3)以亚硝酸盐为电子受体进行同步反硝化除磷是可以实现的。利用富集的短程反硝化除磷污泥在SBR反应器内31d完成了短程反硝化除磷工艺的启动,COD去除率达69.6%、PO_4~(3-)-p去除率达79.2%、NO_2~--N去除率达98.9%,其除磷量与亚硝酸盐的消耗量的比值为1.39mgP/mgN。
4)污泥龄(SRT)、亚硝酸盐浓度、碳源有机物与pH值等因素均会影响短程反硝化除磷工艺的稳定运行,本试验中污泥龄(SRT)宜控制在16～20d,当进水NO_2~--N浓度达到于45mg/l时,没有对聚磷菌产生抑制作用;当进水COD、NO_2~- -N和PO_4~(3-)-p的质量比约为350:35:8.50时,反硝化聚磷效果最佳;为充分保证厌氧段的高效释磷作用,应将进水NO_2~--N浓度控制在2mg/L以下;本试验中短程反硝化除磷系统的进水COD浓度应控制在300～400mg/L。不同碳源为条件下进行基质转化规律存在较大差异,乙酸钠与丁酸的降解途径相似,而与葡萄糖的降解途径不同;本试验结果表明厌氧段最佳pH值为8.0,缺氧段最佳pH值为7.0。
5)通过改进型SBR动力学模型分析得出厌氧段有机物与磷酸盐之间的化学计量系数γ为0.206,有机物吸收常数k为0.0613 h~(-1),有机物去除饱和浓度k_s为97.087mg/L,缺氧段磷酸盐最大比消耗速率(?)_p为0.435 d~(-1),磷酸盐去除饱和浓度K_(s,PO_4~(3-))为49.648 mg/L,短程反硝化除磷菌最大产率系数Y_(max,p)为0.906,短程反硝化除磷菌的衰减系数b_p为0.0015 d~(-1),缺氧段反硝化速率常数k_(NO_2~-)为3.108 mg/(gMLSS·h)。通过对短程反硝化除磷菌与常规反硝化除磷菌动力学参数的比较,发现前者厌氧段对有机物的吸收能力、释磷能力及吸磷能力较后者强,但缺氧段反硝化能力远小于后者。
The process of denitrifying phosphorus removal using nitrite as electron acceptor has the characteristics of short cycling period and rapid phophorus uptake rate, combined with the short-cut nitrification can realize two stages activated sludge systems together—short-cut nitrification-denitrifying phosphorus removal using nitrite,but at present there are many problems in the denitrifying phosphorus removal technique using nitrite,such as the inhibitory degree of nitrite nitrogen on the anoxic phosphorus uptake,the inhibitory mechanism of nitrite nitrogen on the anoxic phosphorus uptake and the kinetics of denitrifying phosphorus removal using nitrite, and so on,all the problems are critical issues which should be studied.The effect of different start-up modes starting up a batch denitrifying phosphorus removal process using nitrite was contrasted,and adopting sequencing batch reactor(SBR);the effect of sludge retention time(SRT)、nitrite concentration、carbon resource organism and pH Value on denitrifying phosphorus removal technique using nitrite was explored, respectively;meanwhile the kinetic parameters of a batch denitrifying phosphorus removal process using nitrite were determined.The main results were as follows:
1) The start-up of denitrifying phosphorus removal technique using nitrite by adopting PAOs can't achieve the perfect result.After anaerobic/sedimentation and displacement/anoxic/sedimentation and displacemen stages,the denitrifying phosphorus removal sludge using nitrite was successfully enriched in 58d by directly putting nitrite into the system,the removal rates of COD,PO_4~(3-)-P and NO_2~--N reached 75.4%,81.8%and 97.4%,respectively,the activated sludge had the color of black and brown and a good adaptability for higher nitrite concentration in the reactor, it was in good condition.
2) By measuring anoxic productivity oxidation efficiency of nitrite k_(NO)、η_(NO) and the ratio of quantity of phosphorus uptaken/consumption of nitrite,the denitrifying phosphorus removal ability can be evaluated,and the feasibility of denitrifying phosphorus removal technique can be determined.The average values of anoxic productivity oxidation efficiency of nitrite and anoxic respiration efficiency were 27.1%,9.4%for denitrifying phosphorus removing bacteria using nitrite induced by PAOs,and were 39.3%,9.2%for denitrifying phosphorus removing bacteria using nitrite enriched by directly putting nitrite into the system.In the suitable operating conditions,the latter could ensure the long-term stable effect of denitrogenation and dephosphorization.
3) Denitrifying dephosphatation process using nitrite as electron acceptor could be realized fully,the short-cut denitrifying phosphorus removal system was successfully started up in 31d based on the enriched denitrifying dephosphatation sludge using nitrite,and adopting sequencing batch reactor(SBR).The removal rates of COD,PO_4~(3-)-P and NO_2~--N reached 69.6%,79.2%and 98.9%,respectively,the ratio of phosphorus uptake to nitrite consumption was 1.39mgP/mgN under anoxic condition.
4) The steady operation of denitrifying phosphorus removal technique using nitrite as electron acceptor was affected by the factors of sludge retention time(SRT)、nitrite concentration、carbon resource organism and pH Value,the sludge retention time should be restricted within 16～20d,the system was not disturbed when the NO_2~--N concentration reached as high as 45 mg/L,the effect of denitrifying phosphorus removal was the best if influent COD,NO_2~--N and PO_4~(3-)-P were about 350、35 and 8.50.In order to ensure high efficient phosphorus release,the NO_2~--N concentration was kept below 2mg/L.Too high or too low inlet COD concentration has great impact on denitrifying phosphorus removal technique using nitrite,the inlet COD concentration should be restricted within 300～400mg/L in this experiment. There was great difference of the transformaing rule of medium in different carbon sources,the degradation pathway of acetic sodium was similar to that of butyric acid, and was different from that of glucose,nitrogen and phosphorus removal effect was better acetic sodium or butyric acid as carbon source than that of glucose,pH Value has great influence on phosphorus release and uptake,the results showed that the optimum pH value of 8.0 in anaerobic stage,the optimum pH value of 7.0 in anoxic stage.
5) Through analysising on the mathematics model of SBR,we could obtain the stoichiometric coefficient between organic matter and phosphate(γ) 0.206,the absorption constant of organic matter(k) 0.0613h~(-1),the organic removal saturated concentration(k_s) 97.087mg/L in anaerobic stage,the maximum phosphate specific consumption rate((?)) 0.435d~(-1),the phosphate removal saturated concentration(K_(s,PO_4~(3-)))49.648 mg/L,the maximum yield coefficient of denitrifying phosphate accumulating organisms using nitrite(Y_(max,p))0.906,the sludge decay coefficient of denitrifying phosphate accumulating organisms using nitrite(b_p) 0.0015d~(-1),the denitrification rate coefficient(k_(NO_2~-))3.108 mg/(gMLSS·h) in anoxic stage.By comparing the kinetic parameters of denitrifying phosphate accumulating organisms using nitrite and denitrifying phosphate accumulating organisms using nitrate,the absorption capacity of the organic matter,the anaerobic phosphorus release ability and the phosphorous absorbing ability of the former were stronger than them of the latter,but denitrifying capacity was opposite.
引文
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