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《城镇污水处理厂污染物排放标准》(GB18918-2002)规定了TN的一级A排放标准限值为15 mg·L−1 ,
${\rm{NH}}_4^ +$ -N的一级A排放标准限值为5 mg·L−1 [1]。2016年以来,各地相继发布了城镇污水处理厂的污染物地方排放标准,其中的出水氮指标愈加严格[2]。例如,北京市的《城镇污水处理厂水污染物排放标准》(DB11/890-2012)中TN和${\rm{NH}}_4^ +$ -N的一级A标准限值分别调至10 mg·L−1 和1.0 (1.5) mg·L−1 [3] 。更严格的排放标准也给污水处理厂的生物脱氮工艺提出了更高要求。以前置缺氧反硝化(缺氧-好氧,anoxic-oxic,AO)为代表的生物脱氮工艺是主流的生活污水脱氮技术[4-6]。在相关的工程应用中,一般采取增大内回流比的方式来提高工艺的脱氮效率。然而,内回流液来自于曝气区,其溶解氧含量较高,导致缺氧区不能保持理想的缺氧状态,从而限制了脱氮效率的提升,且很难实现深度脱氮。若在好氧段的后端增加缺氧段形成后置缺氧段,即构成了缺氧-好氧-缺氧(anoxic-oxic-anoxic,AOA)工艺,便可充分利用微生物胞内糖原或聚羟基脂肪酸酯驱动反硝化来进行脱氮[7-8]。该工艺不仅脱氮效果好,还可利用内碳源以节省费用,并在一定程度上减少剩余污泥的产量、降低污泥处置费用,是一种有发展潜力的技术[4]。然而,由于微生物自身存储碳源不足,在长时间的好氧反应后,细胞内的碳源大多已被氧化,此时细胞处于饥饿状态,导致后置缺氧区的内源反硝化效率较低,故仍需采用提高污泥浓度、促进短程硝化反硝化等措施以提高后置缺氧区的反硝化效率[9-13]。
本研究在中试规模装置的后置缺氧区添加生物填料,以提高系统内污泥浓度,并通过添加羟胺调控不同硝化细菌以实现短程硝化反硝化,再优化外回流比以提升整体脱氮,以期为污水深度脱氮工艺的进一步工程化应用提供参考。
基于生物膜耦合AOA的城镇生活污水深度脱氮工艺中试研究
A pilot-scale study of hybrid system of biofilm and anoxic-oxic-anoxic process for enhanced nitrogen removal of municipal wastewater
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摘要: 针对缺氧-好氧-缺氧(AOA)工艺中后置缺氧区效率偏低的问题,通过耦合生物膜、投加羟胺及优化外回流比等方式,在不外加碳源的条件下开展了中试规模的低C/N污水深度脱氮实验,考察了后置缺氧区对强化脱氮的贡献,并分析了系统强化脱氮的实现途径。结果表明:在投加的羟胺质量浓度为5 mg·L−1、外回流比为140%的条件下,系统脱氮效率可提升40%;其中,后置缺氧区提升22%,后期出水TN稳定低于10.0 mg·L−1;脱氮途径由全程硝化反硝化转变为短程硝化反硝化,稳定期系统亚硝酸盐氮积累率达90%以上。微生物群落结构分析结果表明,Acinetobacter为优势菌属参与了系统硝化反硝化,优势菌属Caldilinea 和Dok59及明显富集菌属Candidatus Brocadia、Bacillus和Thermomonas均对脱氮有促进作用。以上结果可为该工艺的进一步工程应用提供参考。Abstract: In view of the low efficiency of post-anoxic zone in the process of anoxic-oxic-anoxic (AOA), a pilot-scale experiment of deep nitrogen removal from low C/N wastewater was carried out without adding carbon sources, by coupling biofilms, adding hydroxylamine and optimizing external reflux ratio. The contribution of post-anoxic zone to enhanced nitrogen removal was explored and ways for enhanced nitrogen removal were analyzed. The results showed that the nitrogen removal efficiency increased by 40% under the conditions of 5 mg·L-1 hydroxylamine and a reflux ratio at 140%. The efficiency of the post-anoxic zone increased by 22%, and the total nitrogen (TN) in the effluent was lower than 10 mg·L-1. The denitrification pathway changed to partial nitrification and denitrification from complete nitrification and denitrification. The nitrite accumulation rate reached more than 90% during the stable operation. The analysis of microbial community structure showed that Acinetobacter was the dominant bacterium involved in systematic nitrification and denitrification. The dominant bacteria Caldilinea and Dok59 promoted the nitrogen removal, as well as the obvious enrichment bacteria Candidatus Brocadia、 Bacillus and Thermomonas. These results can provide reference for further engineering application of the process.
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Key words:
- biofilm /
- hydroxylamine /
- partial nitrification /
- endogenous denitrification /
- pilot study
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表 1 AOA系统的运行工况
Table 1. Operating conditions of AOA system
运行阶段 运行时长
/d羟胺质量浓度
/ (mg·L−1)外回流比
/%温度
/℃阶段1 0~37 0 100 18~20 阶段2 38~51 5 100 18~20 阶段3 52~145 5 140 18~25 表 2 投加羟胺与其他常用碳源的经济性对比分析
Table 2. Comparative analysis of economy for hydroxylamine and other common carbon sources dose
碳源
种类投加位置 投加的质量浓度
/(mg·L−1)试剂单价
/(元·kg−1)单位水量增加成本
/(元 ·104 m−3)羟胺 好氧池 5 30 1 086 乙酸钠 厌氧/缺氧池 36 (按C/N为4) 5 1 800 葡萄糖 厌氧/缺氧池 45 (按C/N为5) 3 1 350 注:假设处理水量为1.0 × 104 m3·d−1,出水平均TN由19 mg·L−1
降至10 mg·L−1。 -
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