DAT-IAT工艺处理城市污水的生态风险评估

采用常规水质指标检测和种子发芽及根伸长抑制的陆生生态毒理方法，评价了DAT-IAT工艺处理过程中各工艺阶段污水的生态风险.常规水质指标检测结果显示，COD和SS可以达标排放，而氮的形态由进水时的NH⁺₄-N转变为DAT、出水中的NO^-₃-N，只是形态发生了变化，并没有从污水中去除，虽然达到了设计的NH⁺₄-N去除要求，可以达标排放，但是并未降低受纳水体发生富营养化的生态风险.生态毒理指标检测结果显示，进水、DAT、出水各阶段污水中COD对小麦种子发芽的半数抑制浓度逐渐降低，分别为249.3、 165.3和161.2 mg·L^-1；对小麦根伸长的半数抑制浓度也逐渐降低，分别为257.6、 154.0和142.1 mg·L^-1，表明DAT-IAT工艺处理过程中污水的生态毒性变化趋势为逐渐增大，处理后的出水存在一定的生态风险，有进一步进行生态风险调控的必要性.在相同水质条件下，小麦根伸长抑制率比小麦种子发芽抑制率更显著，可以把小麦根伸长作为评价污水处理生态风险的敏感指标之一.

Ecological Risk Assessment of the DAT-IAT Process for Municipal Wastewater Treatment

By using the regular water-quality indices and the terrestrial ecotoxicological methods of inhibiting seed germination and root elongation, the ecological risk of the DAT-IAT process for municipal wastewater treatment was assessed. The results of regular water-quality indices determination showed that COD and SS in treated wastewater by the DAT-IAT process could attain the National Integrated Wastewater Discharge Standard. Although NH⁺₄-N could also meet the standard, most of nitrogen could not be removed out of the wastewater because of the N-form changing from NH⁺₄-N to NO^-₃-N. Thus, the ecological risk of eutrophication could not successfully be reduced. The results based on the determination of ecotoxicological indices showed that IC50 of COD in wastewater from inflow water, DAT and effluent toxic to the germination of wheat seeds decreased gradually. The IC50 of the inhibitory rate of seed germination was 249.3 mg·L^-1, 165.3 mg·L^-1 and 161.2 mg·L^-1, respectively, and the IC50 of the inhibitory rate of root elongation was 257.6 mg·L^-1, 154.0 mg·L^-1 and 142.1 mg·L^-1, respectively. It thus revealed that the ecotoxicity of wastewater increased after treatment by the DAT-IAT process, which demanded more studies to address the regulation of the ecological risk. In particular, the inhibition of wheat root elongation was far more sensitive than the germination of wheat seeds under the same water-quality conditions. Thus, the root elongation could be recommended as a sensitive method to assess ecological risk of wastewater treatment effluents.