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在中国,农村污水约占全国污水总量的30%以上[1]。与城市污水相比,农村污水具有来源分散,总量较小,缺少对污水设施的专业维护和定期监测等特点,因此,农村污水需要节能、简单、可分散化的处理方法[2]。农村污水有许多处理方法,如化粪池、人工湿地、稳定塘等,然而这些技术因占地面积大,污染物去除效率低,限制了其广泛应用。活性污泥法普遍应用于农村污水处理,但其主要存在以下问题:一是污泥膨胀,这是活性污泥工艺中普遍的问题;二是能源消耗,活性污泥工艺处理城市污水过程中曝气能耗大[3]。相较于传统活性污泥法,序批式活性污泥法(sequencing batch reactor,SBR)具有抗冲击负荷、占地面积小、污泥易于沉淀不易发生污泥膨胀等优点,但该工艺的推广与应用仍面临着曝气能耗大、氮磷去除率低等技术瓶颈。
近年来一些研究表明,使用微藻-活性污泥共生体系作为活性污泥工艺的替代方案,可以降低曝气成本[4]、同时去除氮磷等污染物且可产生有价值的生物质[5]。在SBR中引入光源可形成光序批式反应器(photosequencing batch reactors,PSBR),活性污泥和藻类协同处理污水,可以提高PSBR中氮磷等污染物的去除效率[6]。SU等[7]利用泥藻共生体系处理生活污水,当蛋白核小球藻与污泥质量比为5:1时,氮和磷去除率最高分别为(91.0±7.0)%和(93.5±2.5)%。LIANG等[8-9]利用一种含有小球藻和地衣芽孢杆菌的藻类-细菌共培养系统处理合成废水,研究结果表明,NH4+-N和TP的去除率分别可达86%和91%~93%。
然而,共培养的PSBR体系受溶解氧(dissolved oxygen,DO)、C/N、水力停留时间(hydraulic retention time,HRT)等环境条件的影响,例如溶解氧含量过低易引起污泥膨胀,若过高则能耗升高[10]。本研究在低溶解氧(DO为(0.4±0.1) mg·L−1)和短停留时间(HRT为6 h)的条件下,设置3组体系:污泥体系、藻体系、泥藻共培养体系,考察了3组体系的污染物去除效果和微生物群落特性差异,进一步揭示了体系的脱氮机理,以期为泥藻PSBR节能减排提供参考。
低溶解氧条件下泥藻共生SBR对农村污水处理效果与微生物特性
Performance and microbial characteristics of co-culture of activated sludge and algae in SBR for rural sewage treatment under low dissolved oxygen conditions
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摘要: 针对序批式活性污泥法(sequencing batch reactor,SBR)曝气大、能耗高等问题,采用光序批式反应器(photosequencing batch reactors,PSBR)处理模拟农村生活污水,对比了污泥体系、藻体系、泥藻体系中污染物去除效果及微生物特性差异。结果表明,与污泥体系相比,泥藻体系中TN和TP的去除率分别提高了48.72%和39.18%;与单独的藻体系相比,泥藻体系中TN和COD的去除率分别提高了16.80%和77.35%。在低溶解氧DO为(0.4±0.1) mg·L−1、停留时间(HRT)为6 h条件下,模拟农村污水经泥藻体系处理后,出水达到《城镇污水处理厂排放标准》一级A标。高通量测序结果表明,泥藻体系和污泥体系的优势菌属具有显著性差异,在泥藻体系中存在Aeromonas7.07%、Runella6.94%等除磷优势菌属和异养硝化-好氧反硝化菌Aeromonas7.07%、Rhodobacter2.70%、Thauera4.58%。功能酶和功能基因预测结果表明,在泥藻体系中铁氧还蛋白-硝酸还原酶含量比泥体系和藻体系分别提高了0.015%和0.023 7%。泥藻体系亚硝酸还原酶含量比泥体系提高了0.010 8%,表明蛋白核小球藻加入污泥后可减少亚硝酸盐对生物的毒害作用,反应体系脱氮性能增强。以上研究结果可为泥藻共生体系处理农村污水提供理论参考。Abstract: Aiming at the problems of high aeration and energy consumption of sequencing batch reactor (SBR), photoSequencing Batch Reactors (PSBR) were used to treat the simulated rural domestic sewage, and the efficiency of pollutant removal and microbial characteristics of sludge system, algae system and sludge-algae system were compared. The results showed that compared with the sludge system, the removal rates of TN and TP in the sludge-algae systems increased by 48.72% and 39.18%, respectively. Compared with the algae system, the removal rates of TN and COD in the sludge-algae system increased by 16.80% and 77.35%, respectively. Under the conditions of low dissolved oxygen (DO=(0.4±0.1) mg·L−1) and hydraulic retention time of 6 hours, the effluent of the sludge-algae system could reach the Class A standard of Discharge Standard of Urban Sewage Treatment Plant. The high-throughput sequencing results showed that the dominant bacterial in the sludge-algae system and sludge system were significantly different, in sludge-algae system, the phosphorus removal dominant bacteria Aeromonas of 7.07%, Runella of 6.94% and the heterotrophic nitrification- aerobic denitrification bacteria Aeromonas of 7.07%, Rhodobacter of 2.70%, and Thauera of 4.58% appeared. Compared with sludge system and algal system, the prediction results of functional enzymes and functional genes showed that the content of ferroxyroxin-nitrate reductase in the sludge-algae system increased by 0.015% and 0.0237%, respectively. The content of nitrite reductase in the sludge-algae system increased by 0.0148% compared with that in the sludge system, indicating that the addition of Chlorella pyrenoidosa to the sludge could reduce the toxic effect of nitrite on organisms, and the denitrification performance of the reaction system was enhanced. The research results can provide a theoretical reference for rural sewage treatment by sludge-algae system.
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表 1 多样性指数表
Table 1. Diversity index table
反应器 Ace指数 Chao指数 覆盖率% Shannon指数 Simpson指数 R1 638.69 633.63 99.72 4.09 0.05 R2 449.26 472.60 99.78 3.04 0.20 R3 637.72 639.34 99.70 4.26 0.04 -
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