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当前我国农村生活污水因其废水C/N比偏低,致使反硝化所需碳源不足,无法提供充足电子,抑制了生物脱氮过程[1]。近年来,研究者探索采用微气泡曝气生物膜反应器[2],AOA-SBR[3]、CW-BER[4]、微生物燃料电池[5-6]和超滤膜与硝化/反硝化[7]等方法,以改善低C/N比污水脱氮效率低的现状;尤其在利用废弃生物质作为固体缓释碳源方面做了大量的研究[8-11],在一定程度上达到了强化脱氮的目的;但该方法存在因释放不稳定导致出水有机物过高的问题。因此,探寻节能高效、简单易行的脱氮新技术具有十分重要的意义。
人工快渗(constructed rapid infiltration,CRI)滤料渗透性能良好、干湿交替运行、兼具过滤和生物降解的双重功能,因而具有基建投资少、工艺简单、管理方便和能耗低等优点,在处理农村生活污水和受污染地表水方面备受关注[12-15]。近年来,陈佼等[16]运用亚硝化-厌氧氨氧化工艺,为解决CRI系统TN去除率低的问题提供了新方法;SU等[17]设计了以砾石、沙子、焦炭和沸石为混合填料的新型CRI,实现了90%的TP的去除率,其在改变CRI运行方式、补充有机碳源和多技术耦合等研究方面亦取得了一定的进展。
铁型反硝化技术是以零价铁(ZVI)或Fe2+替代有机物作为反硝化电子供体的新型脱氮技术,是处理低C/N比污水有效途径之一[18]。纳米零价铁(nZVI)因其粒径小、比表面积大和反应活性高等优点在强化微生物脱氮方面得到了较好的应用[19-22],但其在实际应用存在抗氧化性弱、易团聚和易堵塞系统等缺点[23]。ZHAO等[20-21]以SA/Mt-nZVI作为额外的电子供体处理污水时,发现增加了10%~20%的TN去除率;将花生壳固体碳源与nZVI联用使用显著改善了自养和异养反硝化作用,从而强化生物脱氮效率。
基于CRI的优势和nZVI处理低C/N比污水的不足,本研究向CRI系统填料中混入微米粒径的零价铁粉(记作ZVIP),构建了ZVIP-CRI协同体系。在改善CRI渗透性能的同时,通过营造干湿交替(好氧/缺氧)的运行环境,强化ZVIP缓慢氧化腐蚀释放电子,探索ZVIP强化CRI处理低C/N比污水脱氮的可行性。考察了铁砂体积比(VFe/S)、湿干时间比(TW/D)和碳氮比(C/N)对ZVIP-CRI协同体系INT-ETS和TN去除率的影响,并通过高通量测序分析了填料脱氮功能菌群变化,探索了可能的脱氮机制,以期为ZVIP强化CRI反硝化脱氮性能研究提供参考。
ZVIP-CRI协同体系强化低C/N比污水的脱氮机理及性能
Research of mechanism and performance of nitrogen removal enhancement for Low C/N ratio polluted water by ZVIP-CRI synergistic system
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摘要: 针对当前低C/N比污水脱氮效率低的问题,探索了微米零价铁粉(ZVIP)强化人工快渗(CRI)脱氮的可行性。考察了铁砂体积比(VFe/S)、湿干时间比(TW/D)和进水C/N比(C/N)对ZVIP-CRI协同体系总氮(TN)去除率、电子传递活性(INT-ETS)和填料功能菌群的影响。结果表明:当TN平均进水质量浓度为50.07 mg·L−1、水力负荷周期为12 h时,在VFe/S为10%、TW/D为1/3和C/N为4的优化条件下运行30 d后,该协同体系TN平均出水质量浓度为25.82 mg·L−1,与传统CRI相比,TN去除率提高了17.80%;填料平均INT-ETS值为109.04 mg·(g·h)−1,是传统CRI的5.14倍,证实了ZVIP不仅可作为有效的电子供体稳定能强化CRI脱氮,而且在交替好氧(落干)和缺氧(淹没)运行环境下显著增加了电子传递活性,强化了CRI的长效脱氮性能。利用高通量测序对填料菌群组成进行了对比研究,发现Thiobacillus 反硝化菌属在协同体系中占绝对优势,相对丰度均高于40%,Aquimonas, Brevundimonas, Hydrogenophaga等厌氧氨氧化功能菌属丰度均有增加,据此推测,该协同体系可能存在多种生物脱氮途径。Abstract: Aiming at the problems of low denitrification efficiency in the treatment of micro-polluted water with low C/N ratio, the feasibility of zero valent iron power (ZVIP) with micrometers scale strengthening artificial rapid infiltration (CRI) for the synergistic and advanced denitrification was conducted. The effects of the iron sand volume ratio (VFe/S), Wet-to-dry time ratio (TW/D) and C/N ratio (C/N) of influent on TN removal performance, the change of Electron Transport System (ETS) of the synergistic system and functional microbial population in filler were investigated. The results showed that the ZVIP-CRI cooperative system run for 30 days under the optimal conditions of a hydraulic load cycle of 12 h, VFe/S=10%, TW/D=1/3and C/N=4, the average TN in effluent of the system was 25.82 mg·L−1, and the corresponding TN removal rate increased by 17.80% compared with traditional CRI; the average INT-ETS of filler was 109.04 mg·(g·h)−1 and 5.14 times of traditional CRI system. It was demonstrated that ZVIP can be devoted as an effective electron donor to enhance denitrification in CRI system, and increased electron transfer activity and long-term denitrification performance in alternating aerobic (dry) and anoxic (submerged) environment of CRI. High-throughput sequencing was used to compare the bacterial community structure of synergistic system, it was found that Thiobacillus of denitrifying bacteria dominated in the reactor, and their relative abundances were higher than 40%. The abundance of Aquimonas, Brevundimonas, hydrogenophaga and other anoxic ammonia oxidizing bacteria increased, which suggested that there might be a variety of biological denitrification pathways.
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Key words:
- zero valent iron power /
- CRI /
- Low C/N ratio /
- electron transfer activity /
- denitrification
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表 1 脱氮可行性实验方案
Table 1. Plan of feasibility experiment of nitrogen removal
实验
柱号铁砂
体积比进水水质 运行条件 C/N COD
/(mg·L−1) -N$ {\rm{NO}}_3^{-} $
(mg·L−1)R1 0 4 200 50 水力负荷周期为12 h、TW/D为1:2条件下运行15 d R2 5% 0 0 50 R3 5% 4 200 50 表 2 影响因素实验方案
Table 2. Plan of influencing factor experiment
影响因素 因素水平 运行条件 水力负荷周期/h 进水C/N TW/D TW/D 1∶2、1∶3和1∶4 12 4 — C/N比 2、3和4 12 — 1∶3 铁砂体积比 0%、5%、10%和20% 12 4 1∶3 -
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