污水再生利用是解决水资源短缺和水环境污染问题的重要途径，保障水质安全是污水再生利用的关键问题。再生水水源污水厂二级出水中污染物成分复杂，可能含有多种病原微生物和化学污染物，经深度处理后仍存在水质安全风险。再生水厂自身操作运行条件的波动性也是出水水质风险的来源之一。此外，再生水水质标准的日益严格对保障再生水水质达标提出了挑战。因此，如何在科学系统地评价再生水厂水质风险基础上制定实用有效的风险管理策略，已经成为保障我国再生水安全迫切需要解决的问题。 本研究针对我国再生水安全管理面临的上述问题，以再生水厂水质模型为核心工具，构建了再生水厂水质风险评价与管理的方法学。该方法学能够模拟和评价再生水厂进水水质和工艺运行参数等对出水水质风险的影响，从进水到各工艺单元的全过程识别水质风险关键控制指标，从而为制定实用有效的再生水厂水质风险管理策略提供支持。 本研究开发了机理性再生水厂水质模型，该模型能够模拟COD、NH3-N、粪大肠菌群、余氯、遗传毒性和雌激素效应沿超滤、臭氧和氯消毒工艺单元的变化。基于现场数据进行参数识别和模型验证。结果表明，模型具有较好的模拟效果和高比例的灵敏参数，且参数数值与文献值基本吻合，因此，模型具有较高的可靠性。 本研究应用模型对清河再生水厂开展水质风险评价与管理案例研究。根据相关再生水水质标准确定常规指标水质风险评价标准，根据毒性效应当量物质预测无效应浓度推算出再生水厂出水毒性效应限值，作为毒性效应水质风险评价标准。应用再生水厂水质模型模拟出水水质的概率分布，并结合水质风险评价标准，评价再生水厂出水水质风险。结果表明，清河再生水厂出厂水存在一定水质风险，且NH3-N、遗传毒性和雌激素效应的风险较高。依据区域灵敏度分析的方法，识别水质风险的关键控制指标，进而从设定污水厂二级出水的污染物控制目标、优化再生水厂工艺运行参数等方面制定水质风险管理策略。
Wastewater reclaimation and reuse is an important method to solve the problem of water shortage and water pollution. Guarantee of reclaimed water safety is a key issue of wastewater reclaimation. Many types of chemical pollutants and pathogens exist in secondary effluent of wastewater treatment plants and reclaimed water, which may cause water quality risk. The variation of operating conditions of wastewater reclaimation plants is also a source of effluent water quality risk. Moreover, increasingly stringent reclaimed water standards also challenge reclaimed water quality. Therefore, an urgent problem is put forward, i.e. how to establish effective strategies of risk management based on scientificly evaluating water quality risk of wastewater reclaimation plants. Aiming at solving this problem, a methodology was developed for assessing and managing water quality risk in a wastewater reclaimation plant based on a wastewater reclaimation plant model. With this methodology, the influence of influent water quality and operating conditions on water quality risk in a wastewater reclaimation plant could be simulated and evaluated, the critical control indexes of water quality risk in the wastewater reclaimation plant could be identified, and effective management strategies for reclaimed water safety could be formulated. The conceptual wastewater reclaimation plant model was developed. The model could simulate the variations of chemical oxygen demand, ammonia-nitrogen, fecal coliform, residual chlorine, genotoxicity and endocrine disrupting effect through ultrafiltration, ozonation and chlorination. The model was calibrated and validated against field monitoring data. Results indicated that the model had good simulation performance and a high proportion of sensitive parameters, and the values of model parameters coincided well with the literature values. Therefore, the model exhibited high reliability. The wastewater reclaimation plant model was applied for assessing and managing water quality risk in Qinghe wastewater reclaimation plant. The water quality risk assessment standards for conventional water quality indexes were determined according to related water quality standards for reclaimed water. The limiting values of effluent toxicity of the wastewater reclaimation plant, namely the water quality risk assessment standards for toxicity, were determined according to predicted no-effect concentrations of toxic equivalent concentrations. The probability distributions of effluent quality were simulated by applying the wastewater reclaimation plant model. Combing the simulation results with the water quality risk assessment standards, the effluent quality risk of Qinghe wastewater reclaimation plant was evaluated. Results indicated that water quality risk might be high in terms of ammonia-nitrogen, genotoxicity and endocrine disrupting effect. The critical control indexes that determine water quality risk were identified through regional sensitivity analysis. On this basis, effective management strategies such as setting water quality goals for secondary effluent and optimization of wastewater reclaimation plant with respect to operation were proposed.
