水平潜流人工湿地对畜禽养殖废水中特征污染物的去除

为了探究水平潜流人工湿地去除畜禽养殖废水污染物的性能,选择养殖废水中常见的特征污染物抗生素——四环素(tetracycline,TC)和重金属Cu2+,构建模拟水平潜流人工湿地,设置空白处理(CK)、进水中外加1 mg·L-1四环素(TC)、进水中外加5 mg·L-1 Cu2+(Cu)、进水中外加1 mg·L-1四环素和5 mg·L-1 Cu2+(TC+Cu)这4组潜流人工湿地,考察人工湿地对畜禽养殖废水中污染物的去除效果.结果表明,CK组湿地对养殖废水中总有机碳(total organic carbon,TOC)、总氮(total nitrogen,TN)、NH:-N和 PO43-P 的去除率分别为(84.3±7.2)％、(78.6±7.0)％、(82.1±4.4)％和(88.0±6.0)％,与 CK 组相比,TC、Cu和TC+Cu组湿地对TN的去除率分别下降了 0.4％～21.7％、2.8％～25.5％和4.3％～27.0％,对NH4+-N的去除率分别下降了 1.6％～15.7％、2.5％～17.8％和8.4％～23.0％,进水中添加TC或Cu2+对湿地TN和NH4+-N的去除有明显抑制作用.TOC、TN、NH4+-N和P043--P等污染物的去除主要发生在湿地前端.TC、Cu和TC+Cu组人工湿地对TC和Cu2+的去除率均分别在99.9％和91.4％以上.4组湿地出水中11种四环素抗性基因(tetracycline resistance genes,TRGs)绝对丰度均显著低于进水(低约2～3个数量级).CK组湿地出水tetA、tetC、tetE、tetO、tetQ、tetT和tetBp基因相对丰度均显著低于进水,这7种TRGs的去除率为43.3％(tetC)～96.3％(tetA).与CK组相比,进水中添加TC或Cu2+使湿地出水中TRGs相对丰度有所升高,TC、Cu和TC+Cu组湿地出水中TRGs相对丰度分别比CK组高12％～52％、6.7％～51％和24％～82％.人工湿地对抗生素、重金属和抗生素抗性基因有好的去除率,是一种适宜净化畜禽养殖废水的深度处理技术.

Removal of Characteristic Pollutants in Livestock Wastewater by Horizontal Subsurface Flow Constructed Wetlands

To explore the removal efficiency of characteristic pollutants in livestock wastewater by horizontal subsurface flow constructed wetlands (CWs), this study selected tetracycline (TC) and Cu²⁺, a familiar antibiotic and a typical heavy metal in livestock wastewater, respectively, to build the following four groups of CWs:control (CK group), 1 mg·L^-1 TC in influent (TC group), 5 mg·L^-1 Cu²⁺ in influent (Cu group), and both 1 mg·L^-1 TC and 5 mg·L^-1 Cu²⁺ in influent ("TC+Cu" group). The average removal rates for control CWs were (84.3±7.2)% for total organic carbon (TOC), (78.6±7.0)% for total nitrogen (TN), (82.1±4.4)% for ammonia nitrogen (NH₄⁺-N), and (88.0±6.0)% for PO₄^3--P in a long-term operation. Compared with that in the CK group, the removal rate of TN in the TC group, Cu group, and "TC+Cu" group decreased by 0.4%-21.7%, 2.8%-25.5%, and 4.3%-27.0%, respectively, and the removal rate of NH₄⁺-N decreased by 1.6%-15.7%, 2.5%-17.8%, and 8.4%-23.0%, respectively. TC or Cu²⁺ in the influent significantly inhibited the removal of TN and NH₄⁺-N in livestock wastewater by CWs. The removal of TOC, TN, NH₄⁺-N, and PO₄^3--P by the CWs mainly occurred in the front section of the CWs. The removal rates for TC and Cu²⁺ were above 99.9% and 91.4% in the effluent of both CWs treated with TC, Cu²⁺ respectively and CWs treated with TC and Cu²⁺. The results showed that influent had a higher abundance of 11 tet genes than effluent by approximately two to three orders of magnitude through all CWs, suggesting that the CWs may play a dominant role in antibiotic resistance genes (ARGs) and the bacteria removal process. The relative abundances of seven tet genes (tetA, tetC, tetE, tetO, tetQ, tetT, and tetBp) in effluent were lower than those in influent, and seven tet genes were reduced by 43.3% (tetC)-96.3% (tetA) in the CK. Compared to that in the CK, the addition of TC or Cu²⁺to the influent increased the relative abundance of TRGs in the effluent of CWs. The relative abundances of TRGs in the effluent of the TC group, Cu group, and "TC+Cu" group were 12%-52%, 6.7%-51%, and 24%-82% higher, respectively, than that in the CK. These results suggest that CW is suited for livestock wastewater advanced treatment, as it provides great application prospects in the removal of antibiotics and heavy metals and the alleviation of the future risk of antibiotic resistance genes.