不同深度复合垂直流人工湿地脱氮性能比较

NITROGEN REMOVAL PERFORMANCE OF COMPOSITE VERTICAL FLOW CONSTRUCTED WETLAND AT DIFFERENT DEPTHS

设计构建了4套分段式复合垂直流人工湿地(IVCW)柱状模拟系统(总程分别为145,185 cm),针对低C/N型人工污水,研究基质层高、添加活性生物质及进水中氮素组成对该系统脱氮效果的影响。结果表明:当水力停留时间为1 d时,4套系统对总氮(TN)去除率均在30%以上,半程基质层设置为95 cm,不添加活性生物质的HI组对TN去除率最高,达到42%;对NH_(3)-N、NO^(-)_(3)-N的平均去除率分别为20%~48%、21%~66%,而NO^(-)_(2)-N在各系统中均发生了不同程度的积累。随着进水中NO^(-)_(3)-N占比负荷的增加(从1/7到6/7),其NO^(-)_(3)-N去除率整体呈下降趋势,仅HI组去除率变化较其他组更稳定。但IVCW系统加深后,添加活性生物质反而会降低其TN去除效果。IVCW系统第1段,即下行流上层单元对脱氮贡献最大,高达80%以上;不同处理间强化脱氮效果差异虽不显著,但系统后段其脱氮途径间存在一定差异。相应地,微生物脂肪酸的丰度和种类在第1段最高,其脂肪酸组成与其他段差异最明显;以cy19:0为标志的厌氧细菌在上行流第3~4段逐渐占据优势,且加深组均高于其对照组;单不饱和脂肪酸(MUFA)表征的好氧细菌对IVCW系统脱氮效率贡献更大。

In this project,four sectional IVCW column pilot systems with the column depth of 145 cm and 185cm were built for wastewater with a low C/N ratio,to examine the effects of substrate height,the addition of active biomass and nitrogen composition in influent on nitrogen removal efficiency of the system.Results showed when the hydraulic retention time was 1 d,the total nitrogen(TN)removal rate of the four systems was all above 30%,and when the half-way substrate layer was set at 95 cm,the HI group without active biomass added had the highest TN removal rate of 42%;the average removal rates of NH3-N and NO3-N ranged from 20%to 48%and 21%to 66%respectively,while NO2-N was found accumulated in different degrees in each system.With the increase of the proportion of NO3-N in the influent(from 1/7 to 6/7),the removal rate of NO3-N in the influent decreased as a whole,and the removal rate of HI group was more stable than that of the other groups.However,after the depth of the IVCW system was increased,adding active biomass will reduce its TN removal effect.The first stage of the IVCW system,i.e.the upper downflow unit,contributed the most to nitrogen removal,up to 80%;although the effect of enhanced nitrogen removal was not significant among different treatments,there were certain differences in the nitrogen removal pathway in the later stages of the system.Accordingly,the abundance and type of microbial fatty acids were the highest in the first segment,and their fatty acid composition was the most obvious difference from other segments;the anaerobic bacteria marked by cy19:0 gradually occupied the dominant position in the 3 to 4 segments of the upstream flow,and the deepened group was higher than the control;the aerobic bacteria characterized by monounsaturated fatty acids(MUFA)contributed more to the nitrogen removal efficiency of the IVCW system.