HepG2细胞对垃圾渗滤液经SND/UF/RO处理前后的毒性评估

垃圾渗滤液含有高浓度难降解毒性污染物及致癌、致诱变和致畸物质，其较为成熟的处理工艺主要有硝化反硝化（SND）、超滤（UF）和反渗透（RO）等.目前，关于SND/UF/RO技术对渗滤液处理前后的毒性降低情况尤其与细胞凋亡相关的研究较缺乏，故本文选用HepG2细胞为评价对象，研究经SND/UF/RO处理前后垃圾渗滤液的细胞毒性、遗传毒性.细胞毒性结果表明，经SND/UF/RO处理后，暴露在浓度为30%渗滤液中HepG2细胞活力从38.3%上升至88.4%；同时，凋亡试验和细胞周期分析表明，经SND/UF/RO处理后的出水清液无法诱导细胞发生凋亡，但可将细胞阻滞在G2期诱导细胞内染色体畸变.这是由于出水清液对HepG2细胞有明显的氧化损伤，但渗滤液原液可诱导细胞凋亡且阻滞细胞停留在S期而影响其增殖.微核试验数据显示，出水清液的遗传毒性是阴性对照组的2倍，彗星实验佐证了出水清液对细胞内DNA有微弱损伤.实验表明，SND/UF/RO工艺可将垃圾渗滤液原液的毒性减少约95%，出水清液仍具有微弱的细胞毒性和遗传毒性.因此，需对经SND/UF/RO处理后的排放液毒性高度重视.

Toxicity evaluation of landfill leachate before and after SND/UF/RO treatment on HepG2 cells

Landfill leachate contains high concentrations of refractory toxic pollutants which are carcinogenic, mutagenic and teratogenic. Currently, mature treatment of landfill leachate mainly include simultaneous nitrification and denitrification (SND), ultrafiltration (UF) and reverse osmosis (RO) and so on. It is lacking for the toxicity reduce of landfill leachate before and after SND/UF/RO treatment, especially on cell apoptosis. Therefore, this paper selected HepG2 cells as evaluating subject to study the cytotoxicity and genotoxicity of landfill leachate before and after SND/UF/RO treatment. The results of cytotoxicity showed that the viability of HepG2 cells increased from 38.3% to 88.4% after SND/UF/RO treatment when cells exposed to 30% leachate. Meanwhile, apoptosis experiments and cell cycle assays showed that the effluent could not induce cell apoptosis, but block the cells in the G2 phase and induce intracellular chromosomal aberration because of the effluent has obvious oxidative damage to HepG2 cells, while untreated leachate could induce cells apoptosis and block cells in S phase and affect their proliferation. The data of micronucleus test showed that genotoxicity of the effluent was 2-fold compared to negative control, and comet assay confirmed that the effluent could damage the DNA weakly in cells. These experiments show that SND/UF/RO treatment can reduce the toxicity of landfill leachate by about 95%, but its effluent still has weak cytotoxicity and genotoxicity. So it is necessary to pay high attention to the toxicity of SND/UF/RO treated leachate, which is discharged directly into the environment.