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生物处理法由于其成本低、效率高等优势被广泛应用于生活污水处理[1],污水中的有机物与各种营养物质(氮、磷等)通过微生物代谢被利用。其中,温度和碳源是影响该过程的重要因素[2]。低温会使微生物活性和底物利用率下降,导致污水处理性能下降[3];另一方面,低温也会导致活性污泥的沉降性能变差,出现污泥膨胀[4]。有机碳源是微生物反硝化过程的电子供体和能源,碳源缺乏会对脱氮造成不利影响[5]。
A2/O工艺具有工艺流程简单、运行灵活、水力停留时间短、活性污泥不易膨胀、基建和运行费用低等优点[6],因而在国内外应用广泛。但A2/O工艺本身就存在反硝化菌与聚磷菌的碳源竞争等矛盾,在低碳氮比的进水条件下,这一矛盾愈发突出。低温条件下,A2/O工艺的启动受到显著负面影响,生物处理系统的效率明显下降[7]。
在我国大部分地区的城市生活污水,尤其是南方地区的城市生活污水,均具有C/N偏低的特点,COD一般约为200 mg·L−1[8],COD/TN为3.3~8.5[9],而满足或完成反硝化的COD/TN为4~15[8]。在温度方面,由于地理区域的差异以及季节变化,水温可能降低至8~15 ℃,甚至低于5 ℃[3]。因此,低温低C/N的进水条件对污水生物处理系统的稳定运行和生物脱氮的效率提出了挑战。
基于上述研究,本研究利用中试规模的A2/O装置,研究了低温低C/N进水条件下装置的脱氮规律,并结合反应动力学,评估了该条件对脱氮效果的影响,以期为优化低温低C/N进水条件下A2/O工艺的运营调控提供数据支持。
A2/O工艺处理低温低碳氮比生活污水的脱氮效率及反应动力学
Nitrogen removal efficiency and kinetics of A2/O process treating low temperature and low C/N ratio municipal wastewater
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摘要: 低温低碳氮比(C/N)生活污水对生物脱氮不利。利用A2/O中试装置探究了低温低碳氮比进水条件对生物脱氮效率的影响,并结合反应动力学进行了评价。结果表明,低温低碳氮比的进水条件对COD、
$ {{\rm{NH}}_4^ +} $ -N的去除影响较小,出水均能达到一级A排放标准;对TN的去除影响较大,平均去除率仅为56.5%,其原因在于反硝化过程受到限制。沿程实验结果表明,较高的溶解氧(DO)和碳源的缺乏是导致反硝化效果差的主要原因。反应动力学拟合的结果表明,温低碳氮比的进水,其比硝化速率、比反硝化速率明显低于常规状态下进水的值,且比反硝化速率对${{\rm{NO}}_3^ - } $ -N浓度的变化敏感。Abstract: It is difficult to denitrify low temperature and low C/N municipal wastewater. A pilot-scale A2/O plant was used to explore the influence of low-temperature and low-C/N ratio of influent on nitrogen removal, and bioreaction kinetics was combined to conduct the evaluation. The results show that the low temperature and low C/N ratio of influent had slight effect on the removal of COD and$ {\rm{NH}}_4^ + $ -N, the effluent could meet the discharge standard of first class A (GB 18918-2002). These influent conditions had a large impact on the removal of TN, and an average TN removal rate was only 56.5%, which was attributed to the inhibition of the denitrification process. The experiment results along the process show that high DO and the lack of carbon source were the main reasons for the poor denitrification effect. The results of kinetics fitting show that for the influent of low-temperature and low-C/N ratio, the specific nitrification rate and specific denitrification rate were significantly lower than the values under normal conditions, and the specific denitrification rate was sensitive to the change of${\rm{NO}}_3^ - $ -N concentration.-
Key words:
- A2/O process /
- low temperature /
- low C/N ratio /
- nitrogen removal /
- reaction kinetics
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表 1 实验用水水质
Table 1. Characteristics of influent wastewater
数值类型 COD/
(mg·L−1)TN/
(mg·L−1)${\rm{NH}}_4^{+} $ -N/
(mg·L−1)COD/TN 范围 148.90~250.60 34.98~55.87 23.09~39.43 2.89~6.08 平均值 198.95 45.19 30.78 4.43 表 2 沿程实验水质测试结果
Table 2. Water quality test results along the process
取样位置 COD/(mg·L−1) $ {\rm{NH}}_4^ + $ -N/(mg·L−1)${\rm{NO}}_3^ - $ -N/(mg·L−1)${\rm{NO}}_2^ - $ -N/(mg·L−1)DO/(mg·L−1) ORP/mV 进水 204.80 24.90 0.47 0.048 — — 厌氧池出口 62.67 13.32 0.84 0.078 0 −225 缺氧池出口 28.59 6.14 9.18 0.199 0.68 93 好氧池出口 25.58 2.08 13.54 0.003 4.33 157 二沉池出水 23.10 1.02 14.49 0.033 — — -
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