复合人工湿地处理低浓度畜禽养殖废水的净化效果

Purification performance of combined constructed wetlands on livestock wastewater with low concentration of pollutants

为了解人工湿地对低浓度畜禽养殖废水的去除速度与净化效果,采用4级复合人工湿地以间歇进水的方式处理低浓度猪场废水,监测不同时期各级湿地进出水中TN、TP、NH_4^+-N、COD_(Cr)等污染物指标浓度的变化。结果表明,复合人工湿地进水中TN、TP、NH_4^+-N、CODCr年平均初始浓度分别为41.6、8.4、21.4、253.9 mg·L^(-1),去除率分别为94.66%、79.36%、91.04%、32.32%。其中1级湿地(芦苇-砾石垂直渗透流)对TN、TP和CODCr去除速度较快,分别为2.9、0.6、7.5 g·m^(-2)·d^(-1);2级湿地(芦苇-沸石垂直渗透流)对NH_4^+-N去除速度较快,为1.8 g·m^(-2)·d^(-1);3级湿地(芦苇-砾石水平潜流)和4级湿地(稻田水平表面流)对污染物的去除速度较低,对TN、TP、NH_4^+-N的去除速度均小于0.4 g·m^(-2)·d^(-1),对COD_(Cr)的去除速度小于2.3 g·m^(-2)·d^(-1)。污染物去除率受季节温度变化的影响较小。

In order to evaluate the removal rate and efficiency of livestock wastewater with low concentration of pollutants in constructed wetlands, four-stage combined constructed wetlands were used to purify piggery wastewater with low concentration of pollutants under intermittent influent. The variations of TN, TP, NH4＋-N, and CODCrin different stages of the wetlands were monitored during spring, summer, autumn,and winter. The annual average concentrations of TN, TP, NH4＋-N, and CODCrin the influent were 41.6, 8.4, 21.4, and 253.9 mg·L-1, respectively, and the removal efficiencies of these pollutants were 94.66%, 79.36%, 91.04%, and 32.32%, respectively. In addition, the first stage of the wetlands（reed-gravel vertical seepage flow）had higher rates for removing TN, TP, and CODCr, which were 2.9, 0.6, and 7.5 g·m-2·d-1,respectively. The second stage of the wetlands（reed-zeolite vertical seepage flow）showed a high removal rate for NH4＋-N, which was 1.8 g·m-2·d-1. However, the removal rates of pollutants in the third stage（reed-gravel horizontal undercurrent）and the fourth stage（rice-soil surface flow）of the wetlands were lower. The removal rates of TN,TP, and NH4＋-N were all less than 0.4g·m-2·d-1, whereas that of CODCrwas less than 2.3 g·m-2·d-1. Season and temperature had little influence on the removal rates of most of the studied pollutants.