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近年来,随着经济建设的高速发展,城镇人口急剧增加,污水排放量和污染负荷不断增大,从而导致污水处理厂出水排放的受纳水体水质不断恶化[1-3]。2015年4月,国务院印发的《水污染行动防治计划》中明确要求,敏感区域城镇污水处理设施应全面达到一级A排放标准[4]。因此,提标改造已成为污水处理厂满足愈发严格的出水排放标准的必然选择之一[5]。然而,在实际污水处理厂提标改造过程中,由于对运行参数变化导致的运行效率改变机制认识不清,盲目选择微生物种群结构作为响应指标,导致在提标改造关键参数及工艺的选择上也存在一定的盲目性[6-7]。因此,明确运行参数变化对运行效率产生影响的根本原因,对目前污水处理厂提标改造具有重要的理论意义。
从污染物降解途径来看,限速酶是物质转化最根本的原因之一。如在氮素转化过程中,氨单加氧酶(AMO)和羟胺氧化还原酶(HAO)是硝化反应的限速酶[8],硝酸盐原酶(NR)和亚硝酸盐还原酶(NIR)是反硝化反应的限速酶[9-11]。一直以来,关于生物脱氮过程中关键酶的研究主要集中在酶的纯化和反应机理上[12-14],近年来,对于酶活性在污水处理过程中的作用才逐步展开。LI等[15]初步分析了与TN去除相关的关键酶种类;CALDERON等[16]阐述了酶活性水平与运行参数变化之间的关系;PAN等[17]探讨了污水处理系统脱氮过程中NR和NIR的特性。然而,这些研究主要集中在实验室小试规模。事实上,实际污水处理厂运行过程比实验室小试装置更加复杂。因此,有必要对实际污水处理厂关键酶活性与污染物去除率之间的关系进行深入研究。
氧化沟是城市污水处理的3大典型工艺之一[18],在中国,从20世纪80年代以来,氧化沟工艺一直被广泛采用[19]。本研究以Orbal氧化沟为研究对象,分析2种运行模式下活性污泥中微生物种群结构、功能微生物含量、关键酶活性及污染物去除效率,并对其相互关系进行了探讨,目的是揭示影响实际污水处理厂污染物去除率的根本原因,以期为实际污水处理厂提标改造提供参考。
Orbal氧化沟工艺污水厂中关键酶活性对污水处理效率的影响
Effect of key enzyme activities on the operating efficiency in wastewater treatment plant with Orbal oxidation ditch
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摘要: 针对实际污水处理厂提标改造过程中运行参数变化对运行效果产生影响机制不明确的问题,选取以Orbal氧化沟为核心工艺的某实际污水处理厂,设置2种运行模式,采用PCR-DGGE分析、实时荧光定量PCR分析、酶活性分析等方法研究了不同运行模式下活性污泥中微生物种群结构、功能微生物含量、关键酶活性的特征;分析了微生物种群、关键酶活性与污染物去除率之间的关系;探讨了Orbal氧化沟工艺中运行参数变化对运行效果产生影响的机制。结果表明:适当减少Orbal氧化沟外侧沟道内转刷的开启数量,其沟道内溶解氧分布将发生明显变化;沿水流方向,厌氧或缺氧段将明显延长;长期运行结果显示,进水水质稳定时,减少转刷开启数量没有对生物处理工段内微生物种群结构产生影响。同时,外侧沟道内硝酸还原酶(nitrate reductase, NR)活性(以羟胺计)在夏季和冬季却均有显著增加,分别由模式Ⅰ的1.58 mg·(g·h)−1和0.80 mg·(g·h)−1增加到了模式Ⅱ的2.27 mg·(g·h)−1和1.07 mg·(g·h)−1;相关分析表明,HAO和NR活性与氨氮和总氮去除率呈显著相关,斯皮尔曼相关系数r分别为0.99(P=0.01)和0.88(P=0.12)。在实际污水处理厂中,关键酶活性是运行参数改变对运行效率产生影响的根本原因。Abstract: During the upgrade processes of full-scale wastewater treatment plant (WWTP), the effect mechanism of operation parameters variations on WWTP performance is still unclear. A WWTP with Orbal oxidation ditch was selected and two operation modes were set up. Molecular biological methods e.g. polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), real-time quantitative PCR and enzyme activity analysis were used to study the microbial population, functional microbial content and key enzyme activity in activated sludge under different operation modes, and the relationships between the microbial population, key enzyme activity and pollutant removal efficiency were analyzed. The effect mechanism of the parameters on the Orbal oxidation ditch performance was also discussed. The results showed that an obvious change in the dissolved oxygen (DO) distribution in the outer channel occurred when properly reducing the number of operating brushes in Orbal oxidation ditch. As a result, the anaerobic or anoxic zone extended significantly along the direction of water flow. The results of long-term operation indicated that the number reduction of operating brushes did not affect the microbial population structure in the biological treatment section when the water quality of influent was stable. At the same time, the nitrate reductase (NR) activities in outer channel (calculated by hydroxylamine) in summer and winter increased significantly from 1.58 mg·(g·h)−1 and 0.80 mg· (g·h)−1 under mode I to 2.27 mg·(g·h)−1 and 1.07 mg·(g·h)−1 under mode II, respectively. Correlation analysis indicated that the activities of hydroxylamine oxidoreductase (HAO) and NR had positive relationship with removal efficiencies of
${\rm{NH}}_4^ + $ -N and TN, and the corresponding correlation coefficients were 0.99(P=0.01) and 0.88(P=0.12), respectively. In the full-scale WWTP, the key enzyme activity was the fundamental reason of parameters variations on the operating efficiency. -
表 1 Orbal氧化沟的进水水质
Table 1. Influent quality of Orbal oxidation ditch
模式 COD/(mg·L−1) ${\rm{NH}}_4^ + $ -N/(mg·L−1)TN/(mg·L−1) TP/(mg·L−1) SS/(mg·L−1) pH I 492~734 35.25~48.52 42.56~61.25 2.25~4.15 100~325 6.80~7.20 II 490~684 36.75~47.56 45.75~60.25 2.65~4.75 120~280 6.70~7.20 -
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