MTF-CWs工艺对剩余污泥厌氧消化液的强化脱氮效果

Performance of MTF-CWs process in enhanced nitrogen removal from excess sludge anaerobic digester liquids

采用多级潮汐流人工湿地(multi-stage tidalflow constructed wetlands,MTF-CWs)处理城市污水处理厂剩余污泥厌氧消化液(excess sludge anaerobic digester liquids,ES-ADL),以垂直潮汐流的运行方式强化硝化,并根据进水NH_4^+-N和TN浓度分为2种不同工况。实验结果表明:在进水COD、NH_4^+-N和TN浓度分别为(293.68±9.62)、(845.70±11.53)和(847.00±11.47)mg·^(L-1)的条件下(工况1),出水COD、NH_4^+-N和TN浓度分别为(84.47±8.10)、(8.81±1.74)和(351.50±7.78)mg·L^(-1),COD、NH_4^+-N和TN的平均去除率分别为72.45%、98.93%和56.48%;在进水COD、NH_4^+-N和TN浓度分别为(413.31±7.47)、(1 023.85±8.32)和(1 025.78±8.31)mg·L^(-1)的条件下(工况2),出水COD、NH_4^+-N和TN浓度分别为(51.60±6.05)、(9.58±3.13)和(359.92±7.68)mg·L^(-1),COD、NH_4^+-N和TN的平均去除率分别为87.34%、99.05%和64.68%。在上述2种工况条件下,可将城市污水处理厂ES-ADL回流引起的氮循环累积量分别降低58.50%和62.19%。溶解氧消耗计算结果表明:MTF-CWs并没有提供NH_4^+-N的氧化(全程硝化或短程硝化过程)所需要的溶解氧;氮平衡计算结果表明:2种工况条件下通过非传统硝化-反硝化途径(如厌氧氨氧化)去除的总氮负荷分别占据总氮去除负荷的86.30%和82.53%。采用Miseq高通量测序技术进行菌群分析,结果表明:在反硝化脱氮贡献最大的人工湿地单元存在大量的厌氧氨氧化细菌Candidatus Kuenenia,且其占比随着取样深度(0.05～0.20m)增加而增加(其丰度由5.08%增加到13.18%),表明MTF-CWs处理ES-ADL时存在厌氧氨氧化途径。

Multi-stage tidal flow constructed wetlands（MTF-CWs） was employed to treat the excess sludge anaerobic digesting liquids（ES-ADL） in a wastewater treatment plant, which was conducted under vertical tidal-flow mode to enhance nitrification, and two operating cases were set by the influent concentration of NH4~＋-N and TN. In operation case 1, when the influent concentration of COD, NH4~＋-N and TN was（293.68 ± 9.62）,（845.70 ± 11.53）and（847.00±11.47） mg·L^（-1）,the effluent concentration of COD, NH4~＋-N and TN was（84.47 ± 8.10）,（8.81 ± 1.74）and（351.50 ± 7.78） mg·L^（-1）,and the corresponding average removal efficiency of COD, NH4~＋-N and TN reached72.45%, 98.93% and 56.48%, respectively. In operational case 2, when the influent concentration of COD, NH4~＋-N and TN was（413.31 ± 7.47）,（1 023.85 ± 8.32） and（1 025.78 ± 8.31） mg·L^（-1）, the effluent concentration of COD,NH4~＋-N and TN was（51.60 ±6.05）,（9.58±3.13） and（359.92 ±7.68）mg·L^（-1）, and the corresponding average removal efficiency of COD, NH4~＋-N and TN reached 87.34%, 99.50% and 64.68%. Under these two cases, MTF-CWs decreased 58.50% and 62.19% nitrogen accumulation caused by ES-ADL recycling, respectively. The calculation results of consumption of oxygen indicated that the removal of NH4~＋-N did not use up the demand dissolved oxygen of whole nitrification or shortcut nitrification. The calculation results of carbon balance indicated that 86.30% and 82.53%nitrogen loads, respectively, were removed by other nitrification-denitrification pathways under two operating cases.Miseq high-throughput sequencing was employed to analyze the microbial communities, large quantities of anaerobic ammonium oxidation bacteria Candidatus Kuenenia were found in the wetland unit which contributed most in denitrification, the ratio of Candidatus Kuenenia increased as the depth of sampling increased（5.08% to 13.18%）,which substantiated the existence of anaerobic ammonium oxidation pathways during treating excess sludge digester liquids with application of MTF-CWs.