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近年来,集中收集-卫生填埋已成为我国城市生活垃圾的主要处理处置方式[1]。然而,垃圾填埋会产生大量高氨氮、低C/N的垃圾渗滤液,由于其高浓度的氨氮和复杂的有机物组成将对水体环境和人体健康带来严重影响和危害,因此,对于这类废水的处理已成为研究焦点和难点[2]。
目前,短程硝化反硝化耦合厌氧氨氧化(anaerobic ammonia oxidation, ANAMMOX)工艺已成功应用于多种低碳氮比(C/N)的高氨氮废水处理,如垃圾渗滤液、养殖废水及味精加工废水脱氮[3-6]。与常规硝化-反硝化工艺相比,短程硝化反硝化-ANAMMOX工艺可节省60%的需氧量,且ANAMMOX工艺无须外加碳源,是一种高效低耗、运行成本低廉的废水生物脱氮技术[7-8]。但是,理论上,ANAMMOX细菌将1 mol
${\rm{NH}}_4^{+} $ -N和1.32 mol${\rm{NO}}_2^{-} $ -N转化为N2的同时,会生成0.26 mol硝态氮,约占反应总氮的10%(如式(1)所示),造成出水中硝态氮浓度较高,总氮超标[9]。因此,使用短程硝化反硝化-ANAMMOX工艺处理垃圾渗滤液,无法达到我国2008年新修订并实施的《生活垃圾填埋场污染控制标准》[10]中规定的垃圾渗滤液处理厂出水排放标准(NH4+-N≤25 mg·L−1、TN≤40 mg·L−1)。垃圾填埋场填埋气中含有大量硫化氢气体,垃圾渗滤液中硫化物含量也会随着垃圾填埋时间的增加而增加[11]。以深圳某垃圾填埋场为例,填埋场产气量为35 000 m3·h−1,其中,硫化氢气体浓度为150~300 mg·L−1。近年来,以硫化物(H2S/HS−/S2−)作为电子供体的硫自养反硝化(sulfur-driven autotrophic denitrification, SAD)脱氮技术受到广泛关注,SAD生物脱氮过程无需外加碳源,可以有效去除水中
${\rm{NO}}_x^{-} $ -N污染物,同时硫化物被转化为氧化态硫酸盐,且对下游水厂或水环境不会造成不良影响[12-13]。SAD技术已逐步开始应用于低负荷的水体环境修复[14]、生活污水深度处理[15]、水产养殖废水处理[16]和海水冲厕水处理[17]等。目前,对硫自养反硝化的研究比较深入,已具备一定的理论基础[18-20]。因此,利用SAD技术应用于垃圾渗滤液处理,既能解决异养反硝化脱氮中有机碳源(电子供体)不足的问题,又能实现对垃圾填埋气中硫化氢气体无害化处理并回收电子,避免空气污染的同时又节省了填埋气脱硫成本。本研究在实现短程硝化反硝化-ANAMMOX工艺处理垃圾渗滤液稳定运行的基础上,进一步耦合SAD反应器,构建了两级自养脱氮深度处理工艺,并探究了其工艺效能。
两级自养反硝化实现垃圾渗滤液的深度脱氮
Deep denitrification of landfill leachate by two-stage autotrophic denitrification process
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摘要: 针对目前生物工艺难以解决垃圾渗滤液深度脱氮的问题,探究了短程硝化反硝化-厌氧氨氧化-硫自养反硝化(两级自养)工艺处理高氨氮、低C/N比垃圾渗滤液的脱氮效果。结果表明, 当进水垃圾渗滤液中氨氮平均浓度为2 560 mg·L−1,COD值为4 000~5 000 mg·L−1时,经过短程硝化反硝化-厌氧氨氧化处理后,总氮去除负荷可达1.19 kg·(m3·d)−1、总氮去除率可达93.1%(出水TN=176.3 mg·L−1)、COD去除率可达52.2%。但是,厌氧氨氧化反应器出水中
${\rm{NO}}_x^{-} $ -N浓度为154.5 mg·L−1,仍未达到我国生活垃圾填埋场垃圾渗滤液处理排放标准(TN≤40 mg·L−1)。在厌氧氨氧化反应器之后串联硫自养反硝化,整体工艺最终出水${\rm{NH}}_4^{+} $ -N、${\rm{NO}}_2^{-} $ -N、${\rm{NO}}_3^{-} $ -N平均浓度分别为1.9、0.6、9.7 mg·L−1,TN≤15 mg·L−1,进水总氮去除率为99.5%。在短程硝化反硝化-厌氧氨氧化-硫自养反硝化两级自养深度脱氮反应系统中实现了垃圾渗滤液深度脱氮。Abstract: In view of the difficulty of deep denitrification in the treatment of landfill leachate by biological process at present, a new process coupling partial nitrification-denitrification-anaerobic ammonia oxidation (ANAMMOX) and sulfur-driven autotrophic denitrification (SAD) was applied to treat the landfill leachate with high ammonia nitrogen and low C/N ratio. The results showed that at the ammonia concentrations of 2 560 mg·L−1 and COD of 4 000~5 000 mg·L−1 in the influent landfill leachate, the total nitrogen removal load, nitrogen removal efficiency and COD removal efficiency were 1.19 kg·(m3·d)−1, 93.1% (the total nitrogen concentration in effluent was 176.3 mg·L−1), and 52.2% after partial nitrification-denitrification-ANAMMOX treatment, respectively. However,${\rm{NO}}_x^{-} $ -N concentration in the effluent of the ANAMMOX reactor was 154.5 mg·L−1, which could not meet the effluent quality standard of TN≤40 mg·L−1 in domestic solid waste landfill. When the SAD was coupled with partial nitrification-denitrification-ANAMMOX process in a series connection mode, the average concentrations of${\rm{NH}}_4^{+} $ -N,${\rm{NO}}_2^{-} $ -N,${\rm{NO}}_3^{-} $ -N in the effluent of the whole process were 1.9, 0.6 and 9.7 mg·L−1, respectively, the total nitrogen concentration was below 15 mg·L−1, the nitrogen removal efficiency reached 99.5%. Deep denitrification of landfill leachate was achieved by two-stage autotrophic deep denitrification process of partial nitrification-denitrification-ANAMMOX-SAD. -
表 1 垃圾渗滤液水质
Table 1. Characteristic of landfill leachate
pH COD/(mg·L−1) ${\rm{NH}}_4^{+} $ -N/(mg·L−1)${\rm{NO}}_2^{-} $ -N/(mg·L−1)${\rm{NO}}_3^{-} $ -N/(mg·L−1)碱度/(mg·L−1) 8.3~8.8 4 000~5 000 2 300~2 700 <5 <50 10 000~13 000 表 2 SAD反应器启动过程中运行条件
Table 2. Operation conditions during start-up of SAD reactor
阶段 运行时间/d HRT/h 进水流量/(L·d−1) 氮负荷/(kg·(m3·d)−1) 硫负荷/(kg·(m3·d)−1) I 0~30 24 2 0.07 0.14 II 31~70 12 4 0.14~0.18 0.28~0.36 III 71~115 5 9.6 0.43~0.56 0.86~1.12 -
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