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随着人们环境保护意识的增强和国家环境保护政策的严格落实,城镇污水处理厂的数量逐年上升。现有城镇污水处理厂中,约90%采用活性污泥法,其中微生物对污水中氮磷的高效去除需有充足的有机物[1]。由于我国污水存在低C/N的特点,为保证出水氮磷达标排放,污水处理厂需投加大量外部碳源与除磷药剂,从而提高了污水处理厂的运行成本[2]。此外,日益严格的出水标准也进一步提高了污水处理厂的运行成本。因此,低运行成本的污水处理工艺成为研究热点。
生物絮凝系统内污泥微生物分泌的胞外蛋白,可有效将污水中悬浮态和颗粒态COD等难降解有机物絮凝,最终被截留的有机物和污泥可用于厌氧消化,转化为资源与能源物质[3-4]。张闻多等[5]研究发现,经热碱处理后的高有机质含量的剩余污泥厌氧发酵后,挥发性脂肪酸平均浓度为7.93 g·L−1。该挥发性脂肪酸可作为优质碳源,投加至厌氧池或缺氧池,从而降低污水处理厂的外部碳源消耗量,同时可保障污水处理工艺对氮磷污染物的高效去除。此外,生物絮凝系统可减小后续工艺因进水急剧变化而受到的影响,并为后续工艺提供稳定的低C/N进水。
低C/N的进水是反硝化除磷工艺的必要前提,其主要原因为:反硝化除磷工艺通过自养反硝化脱氮除磷,可节约50%的碳源消耗[6-8]。此外,反硝化除磷工艺可减少50%的污泥产量,并降低30%的曝气能耗[9],因此,反硝化除磷工艺的运行成本低于传统工艺。反硝化除磷工艺可分为单污泥工艺与双污泥工艺2类[10-11]。与双污泥工艺相比,单污泥工艺具有操作简便、应用范围广的特点,且与传统AAO工艺相比,AAAO工艺进水COD首先被用于缺氧反硝化过程,确保厌氧条件下释磷不受硝态氮(dissolved nitrates,
$ {\rm{NO}}_3^{-}$ -N)影响。此外,污泥厌氧消化后所产碳源可分点投加至该工艺厌氧池或缺氧池,从而强化脱氮除磷效能,降低污水处理过程外部碳源的使用量。因此,生物絮凝工艺与AAAO工艺相结合可降低污水处理过程中的能源消耗。本研究以城镇污水为对象,考察了中试规模下的生物絮凝-AAAO工艺对实际污水的去除效果。将模拟生物絮凝系统污泥厌氧发酵所产碳源投加至AAAO系统中,以期培养DPAO并强化该中试系统的污染物去除效能,进而为污水处理厂节能降耗与污泥资源化利用提供可借鉴的经验。
生物絮凝-AAAO中试系统污染物去除特性及反硝化除磷菌的培养
Contaminant removal characteristics of bioflocculation-AAAO pilot system and cultivation of denitrifying polyphosphate-accumulating organisms
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摘要: 为降低污水处理成本并实现出水稳定达标,采用中试规模生物絮凝-AAAO工艺处理城镇生活污水,并模拟生物絮凝污泥厌氧消化所产生的碳源,用于强化反硝化除磷菌(DPAO)驯化效果。实验结果表明:生物絮凝系统抗冲击负荷能力较强,化学需氧量(COD)、总氮(TN)和总磷(TP)平均去除率可达67.23%、27%与68.93%。将模拟厌氧消化后产生的碳源投加至厌氧池促进DPAO的驯化后,AAAO系统对COD、TN和TP去除率分别提升31.53%、37.67%和26.37%,反硝化吸磷率最高可达62.97%,二沉池出水COD、TN均满足一级A出水标准,TP可低于0.30 mg·L−1。生物絮凝-AAAO工艺脱氮除磷效果较好,可为污水处理厂节能降耗运行奠定基础并有望得到广泛应用。Abstract: In order to reduce the operation cost and achieve good effluent, the pilot-scale bioflocculation-anoxic-anaerobic-anoxic-oxic(AAAO) process was established to cultivate denitrifying polyphosphate-accumulating organisms(DPAOs) and further enhance phosphorus removal by adding simulative carbon source from bioflocculation sludge through anaerobic digestion(AD) process. The experimental results showed that the bioflocculation process presented good resistance to shock loads, and the average removal rates of chemical oxygen demand(COD), total nitrogen(TN) and total phosphorus(TP) were 67.23%, 27% and 68.93%, respectively. After dosing carbon source produced from simulative anaerobic digestion to anaerobic tank, and DPAO acclimation was promoted, then the COD, TN and TP removal rates of AAAO system increased by 31.53%, 37.67% and 26.37%, respectively. In addition, the maximum phosphorus uptake rate during denitrification process was up to 62.97%, and the TN and COD in effluent of secondary tank could meet the Class A of National Effluent Standard, the effluent TP even decreased to below 0.30 mg·L−1. The pilot-scale bioflocculation-AAAO process demonstrated a good nitrogen and phosphorus removal capacity, which can lay a foundation for energy-saving and cost-reducing operation of wastewater treatment plants, and is expected to be widely promoted.
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表 1 中试系统进水水质及污泥发酵液成分
Table 1. Pilot system influent water quality details and composition of sludge fermentation broth
统计值 COD TN NH4+-N TP SS Al Fe 进水浓度范围 245~852 34.46~54.99 26.95~41.31 6~32 400~2 400 2~10 2~8 进水平均浓度 417.50±177.89 44.17±6.20 33.48±4.03 14.04±6.96 1 362.50±740.54 5±0.12 3±0.15 -
[1] 戴晓虎. 我国城镇污泥处理处置现状及思考[J]. 给水排水, 2012, 38(2): 1-5. doi: 10.3969/j.issn.1000-4602.2012.02.001 [2] LEE W S, CHUA A S M, YEOH H K, et al. A review of the production and applications of waste-derived volatile fatty acids[J]. Chemical Engineering Journal, 2014, 235(1): 83-99. [3] 郝晓地, 李季, 曹达啟. 污水处理碳中和运行需要污泥增量[J]. 中国给水排水, 2016, 32(12): 1-6. [4] 潘宁, 石淑倩, 柯崇宜, 等. 吸附生物降解法(AB工艺)A段反应机理分析[J]. 环境工程, 2000, 18(4): 21-23. doi: 10.3969/j.issn.1000-8942.2000.04.006 [5] 张闻多, 余雷, 刘和, 等. 工程规模下碱类型对污泥预处理效果及发酵产酸的影响[J]. 环境工程学报, 2018, 12(5): 1517-1527. [6] KUBA T, LOOSDRECHT M C M V, HEIJNEN J J. Biological dephosphatation by activated sludge under denitrifying conditions pH influence and occurrence of denitrifying dephosphatation in a full-scale wastewater treatment plant[J]. Water Science & Technology, 1997, 36(12): 75-82. [7] ZENG W, WANG X, LI B, et al. Nitritation and denitrifying phosphorus removal via nitrite pathway from domestic wastewater in a continuous MUCT process[J]. Bioresource Technology, 2013, 143: 187-195. doi: 10.1016/j.biortech.2013.06.002 [8] ZHANG Y, LI M, ZHANG Q, et al. Start-up performance of anaerobic/aerobic/anoxic-sequencing batch reactor (SBR) augmented with denitrifying polyphosphate-accumulating organism (DPAO) and their gene analysis[J]. Water Science Technology, 2018, 78(3/4): 523-533. [9] ZHANG M, YANG Q, ZHANG J, et al. Enhancement of denitrifying phosphorus removal and microbial community of long-term operation in an anaerobic anoxic oxic-biological contact oxidation system[J]. Journal of Bioscience and Bioengineering, 2016, 122(4): 456-466. doi: 10.1016/j.jbiosc.2016.03.019 [10] 张淼, 彭永臻, 张建华, 等. 进水C/N对A2/O-BCO工艺反硝化除磷特性的影响[J]. 中国环境科学, 2016, 36(5): 1366-1375. doi: 10.3969/j.issn.1000-6923.2016.05.014 [11] LIU H, CHEN P, CHEN Z. Role of influent split ratio in a two-line BNR process performing denitrifying phosphorus removal[J]. Chemical Engineering Journal, 2015, 267: 266-273. doi: 10.1016/j.cej.2015.01.036 [12] 国家环境保护总局. 水和废水监测分析方法[M]. 4版. 北京: 中国环境科学出版社, 2002. [13] SUN L, ZHAO X, ZHANG H, et al. Biological characteristics of a denitrifying phosphorus-accumulating bacterium[J]. Ecological Engineering, 2015, 81(1): 82-88. [14] LU Q, QIAN W, LIU W, et al. A fluorescence in situ hybridization method for the measurement of denitrifying phosphorus-accumulation organisms and study on the metabolisms of activated sludge[J]. Journal of Cleaner Production, 2017, 152(1): 28-37. [15] 黄剑明, 赵智超, 郑隆举, 等. 低温下A2/O-BAF反硝化除磷脱氮特性[J]. 环境科学, 2018, 39(10): 4621-4627. [16] CECH J S, HARTMAN P. Competition between polyphosphate and polysaccharide accumulating bacteria in enhanced biological phosphate removal system[J]. Water Research, 1993, 27(7): 1219-1225. doi: 10.1016/0043-1354(93)90014-9 [17] 宋志伟. 水污染控制工程[M]. 北京: 中国矿业大学出版社, 2013. [18] LV X, LI J, SUN F, et al. Denitrifying phosphorus removal for simultaneous nitrogen and phosphorus removal from wastewater with low C/N ratios and microbial community structure analysis[J]. Desalination and Water Treatment, 2014, 57(4): 1890-1899. [19] ONG Y H, CHUA A S M, HUANG Y T, et al. The microbial community in a high-temperature enhanced biological phosphorus removal (EBPR) process[J]. Sustainable Environment Research, 2016, 26(1): 14-19. doi: 10.1016/j.serj.2016.04.001 [20] KIM M G, NAKHLA G. Comparative performance of A2/O and a novel membrane-bioreactor-based process for biological nitrogen and phosphorus removal[J]. Water Environment Research, 2010, 82(1): 69-76. doi: 10.2175/106143009X447966 [21] VANDEKERCKHOVE T G L, DE MULDER C, BOON N, et al. Temperature impact on sludge yield, settleability and kinetics of three heterotrophic conversions corroborates the prospect of thermophilic biological nitrogen removal[J]. Bioresource Technology, 2018, 269(1): 104-112. [22] 田文德. BBSNP工艺性能及反硝化聚磷菌除磷特性研究[D]. 哈尔滨: 哈尔滨工业大学, 2013. [23] WANG Y, PENG Y, STEPHENSON T. Effect of influent nutrient ratios and hydraulic retention time (HRT) on simultaneous phosphorus and nitrogen removal in a two-sludge sequencing batch reactor process[J]. Bioresource Technology, 2009, 99(14): 3506-3512. [24] KERRN J, JENS P, HENZE M. Biological phosphorus uptake under anoxic and aerobic conditions[J]. Water Research, 1993, 27(4): 617-624. doi: 10.1016/0043-1354(93)90171-D [25] 罗富金. 螺旋升流式反应器脱氮除磷效果及污泥特性的试验研究[D]. 重庆: 重庆大学, 2004. [26] 曾薇, 李博晓, 王向东, 等. MUCT短程硝化和反硝化除磷系统中Candidatus Accumulibacter的代谢活性和菌群结构[J]. 中国环境科学, 2013, 33(7): 1298-1308. [27] 戴娴, 王晓霞, 彭永臻, 等. 进水C/N对富集聚磷菌的SNDPR系统脱氮除磷的影响[J]. 中国环境科学, 2015, 35(9): 2636-2643. doi: 10.3969/j.issn.1000-6923.2015.09.011