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已有研究[1-2]表明,生活污水中包含一定量的潜在致病微生物(大肠埃希氏菌、沙门氏菌、志贺氏菌等)。因此,在污水处理系统末端需增加消毒,处理达标之后方可排放。近2年,随着新冠疫情的全球肆虐,不同层面的生物安全问题受到了广泛关注。我国于2021年4月15日起全面实施《生物安全法》,标志着我国生物安全问题进入了依法治理的新阶段[3]。目前,我国现行城市污水生物处理过程中已全部覆盖消毒工艺。但是,对于卫生设施相对薄弱的农村地区,污水中潜在致病微生物的分布、相应污水处理设施的消毒效果等仍存在认识不清、运维不稳等问题,从而对农村地区居民身体健康及区域生态安全造成了极大的潜在风险。
截至2020年,全国共有约5.1亿农村人口,占全国总人口的36%,生活污水排放量很大,而目前针对已有农村污水处理设施的监测重点仍然为COD、NH3-N、TP等基础水质排放控制指标[4-5]。农村生活污水主要来源于厨房污水、生活洗涤污水和冲厕水等,其具有分散性强、水质水量变化大等特点;同时,我国农村区域相对城市而言,经济水平比较低。因此,成本低廉、高度集成、占地面积较小、施工工程量小、运行维护简便的小型化、装备化污水处理设施在农村地区得到广泛应用,净化槽即是其中一种[6-10]。基于其在单户或联用处理中的优势,目前净化槽已经在上海、江苏、云南、山东、黑龙江等地多数农村投入实际使用[11]。调研发现,目前市场上销售的净化槽在工艺单元是配有消毒设施的。但在实际运用中,由于消毒工艺投入成本高,投入的化学消毒试剂如次氯酸钠等在维护不当时可能会造成泄露而引起二次污染,因此,大部分农村地区一体化污水处理设备的消毒设施处于闲置状态,农村污水处理后,未经消毒就直接排放[10]。基于以上研究现状,本研究选取江苏省常熟市虞山街道(N 120°40′48″,E 31°40′48″)处理量为1 m3·d−1的一体化污水处理设施,解析不同工段潜在致病微生物的分布特征,为后续村镇小型污水处理设施运行过程中的健康风险评估研究提供参考。
农村分散式污水处理设施潜在致病细菌分布特征
Characterization of the potential pathogenic bacteria distribution in rural decentralized wastewater treatment facilities
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摘要: 污水是病原微生物传播的重要介质之一。目前我国大多数农村地区生活污水经生化处理后,极少进行消毒就直接排放至自然水体,这是否会造成农村地区污水中病原微生物的传播尚不明确。为此,以未开消毒设施的一体化污水净化槽为研究对象,在其稳定运行阶段,分析了不同处理单元、尤其是出水中细菌种群及潜在致病性细菌种类的特征。结果表明,与进水相比,净化槽各单元均包含一定量的潜在致病细菌,尤其是出水中,检出了20种潜在致病细菌,以Flavobacterium、Pseudomonas等为主。其中部分潜在致病菌随着污水处理流程其丰度呈现上升趋势。例如,Aeromonas、Klebsiella、Arcobacter和Bacteroides在进水中几乎未检出,其相对丰度分别为0%、0%、0.01%和0.21%,但其在出水中检出的相对丰度则为1.26%、0.70%、0.24%和2.63%。以上研究结果初步表明,在农村地区生活污水生物处理设施各工段中,均存在一定的潜在致病性微生物;尤其值得注意的是,在不进行消毒的状态下,出水中也包含多种潜在致病性微生物,其排放对周边环境及人体健康可能存在一定影响。本研究结果可为后续村镇小型污水处理设施的健康风险评估提供参考。Abstract: Wastewater is considered as one of the important transmission media of pathogenic microorganisms. At present, most domestic wastewater in rural areas of China is discharged directly to natural water after biochemical treatment with rare disinfection, and it is not clear whether this causes the transmission of pathogenic microorganisms in wastewater in rural areas. In this study, the characteristics of bacterial populations and potentially pathogenic bacterial species in different treatment units, especially in effluent, were analyzed at the stable operation stage of integrated Johkasou without running disinfection facility. The results showed that compared with the influent, each unit of the Johkasou contained a certain amount of potential pathogenic bacteria. Especially in the effluent, 20 species of potential pathogenic bacteria were detected, mainly were Flavobacterium and Pseudomonas. The relative contents of some potential pathogens showed an increasing trend along the wastewater treatment process. For example, Aeromonas, Klebsiella, Arcobacter and Bacteroides were almost not detected in the influent, and their relative abundances were 0%, 0%, 0.01% and 0.21%, respectively, but their relative abundances detected in the effluent were 1.26%, 0.70%, 0.24% and 2.63%, respectively. The preliminary results of this study show that there are certain potential pathogenic microorganisms in all sections of domestic wastewater biological treatment facilities in rural areas. And it is especially noteworthy that the effluent also contained a variety of potential pathogenic microorganisms without disinfection, and its discharge may have certain effects on the surrounding environment and human health. The results of this study will provide a basis for the health risk assessment of subsequent small-scale wastewater treatment facilities in rural areas.
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表 1 不同处理单元微生物群落丰度和多样性
Table 1. Microbial community abundance and diversity in different treatment units
处理单元 Ace Chao1 覆盖率/% Shannon Simpson A1 1 252.21 1 025.01 99.30 2.25 0.26 A2 1 986.92 1 965.48 98.93 4.13 0.15 A3 2 396.72 2 404.32 98.75 5.49 0.01 A4 2 260.19 2 221.75 98.95 5.01 0.02 A5 1 910.35 1 841.82 99.16 4.92 0.02 A6 2 029.49 1 981.27 98.68 5.06 0.03 -
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