猪场粪污中典型重金属和抗生素的去除及农用风险评估

Agricultural risk assessment and removal of typical heavy metals and antibiotics from piggery wastes

为了解规模化猪场粪污中重金属和抗生素的残留水平,选取山东省某规模化养猪场,采集不同处理阶段废水(暂存池、初沉池、二沉池、终沉池和氧化塘)和好氧反应器进出料,采用原子吸收法/电感耦合等离子体质谱法(ICP-MS)及超高效液相色谱-串联质谱(UPLC-MS-MS)分别对6种主要重金属(Cu、Zn、As、Cd、Cr、Pb)和6种典型抗生素(土霉素、金霉素、强力霉素、磺胺嘧啶、磺胺二甲嘧啶、磺胺甲噁唑)进行测定,并采用内梅罗污染指数法和生态风险商值对氧化塘出水和堆肥产品中重金属或抗生素进行生态风险评估。结果表明:6种重金属和6种抗生素在废水和堆肥产品中均有检出,废水中重金属主要为Cu和Zn,最高浓度分别为15042.5μg·L^(-1)和20890.3μg·L^(-1);主要残留抗生素为土霉素、金霉素和强力霉素,其中土霉素最高浓度可达234.1μg·L^(-1)。猪场废水处理工艺中"固液分离+UASB+多级A/O+氧化塘"组合工段能有效去除重金属和抗生素,重金属的去除率为74.8%~99.7%(Pb除外),抗生素的去除率为39.4%~99.8%,其出水水质满足《农田灌溉水质标准》(GB 5084—2005)。猪粪中抗生素在好氧反应器堆肥过程中的降解率为49.8%~90.9%;好氧堆肥产品中Pb、Zn含量超过了我国《有机肥料》(NY 525—2012)或《农用污泥污染物控制标准》(GB 4284—2018)。研究表明,强力霉素和土霉素为氧化塘出水中主要的高风险污染物,排入环境会造成一定的生态风险,需要采取减量等消减措施;Pb、Zn是堆肥产品中主要的污染物,直接施用农田会带来潜在风险。

To quantitate residual levels of heavy metals and antibiotics in piggery wastes from a large-scale pig farm in Shandong Province,six heavy metals(Cu, Zn, As, Cd, Cr, and Pb) and six antibiotics(oxytetracycline, chlortetracycline, doxycycline, sulfadiazine,sulfamethazine, and sulfamethoxazole)from different treatment units(temporary storage tank, primary settling tank, secondary settling tank, final settling tank, and oxidation pond)and an aerobic composting reactor were detected using atomic absorption spectrometry/inductively coupled plasma mass spectrometry(ICP-MS) and ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS-MS), respectively. The ecological hazards of compost products and effluents from oxidation ponds were assessed using the Nemerow index method or risk quotient(RQ)method. All six heavy metals and all six antibiotics were detected in all wastewater and compost products. The main heavy metals in wastewater were Cu and Zn, with highest concentrations of 15 042.5 μg·L^(-1)and 20 890.3 μg·L^(-1), respectively. Oxytetracycline, chlortetracycline, and doxycycline were the main antibiotics in wastewater, with concentrations reaching234.1 μg·L^(-1). The treatment process "solid-liquid separation + UASB + multistage A/O + oxidation pond" effectively removed heavy metals and antibiotics, with removal rates of 74.8%~99.7%(except Pb) and 39.4%~99.8%, respectively. The effluent quality met Standards for Farmland Irrigation Water Quality(GB 5084—2005). The degradation rate of antibiotics in pig feces ranged from 49.8% to90.9% during the composting process in the aerobic reactor. Pb and Zn concentrations in aerobic composting products of pig feces exceeded the limits specified in the Organic Fertilizer(NY 525—2012), and the Control Standards of Pollutants in Sludge for Agricultural Use(GB 4284—2018). In conclusion, doxycycline and oxytetracycline are the main pollutants, associated with high risk in the discharge water of oxidation ponds, posing a level of ecological risk to the environment. Further reductions or other mitigation measures should be considered. Pb and Zn are the main pollutants in compost products, which could pose potential risks if applied directly to farmlands.