In contrast to water consumption, water pollution has gained less attention in water footprinting so far. Unlike water scarcity impact assessment, on which a consensus has recently been achieved, there is no agreement on how to address water quality deterioration in water footprinting. This paper provides an overview of existing water footprint methods to calculate impacts associated with water pollution and discusses their strengths and limitations using an illustrative example. The methods are described and applied to a case study for the wastewater generated in textile processing. The results for two scenarios with different water quality parameters are evaluated against each other and the water scarcity footprint (WSF). Finally, methodological aspects, strengths and limitations of each method are analysed and discussed and recommendations for the methods application are provided. Two general impact assessment approaches exist to address water quality in water footprinting: the Water Degradation Footprint (WDF) calculates the impacts associated with the propagation of released pollutants in the environment and their uptake by the population and ecosystem, while the Water Availability Footprint (WAF) quantifies the impacts related to the water deprivation, when polluted water cannot be used. Overall, seven methods to consider water quality in water footprinting were identified, which rely upon one or a combination of WDF, WAF and WSF. Methodological scopes significantly vary regarding the inventory requirements and provided results (a single-score or several impact categories). The case study demonstrated that the methods provide conflicting results concerning which scenario is less harmful with regard to the water pollution. This paper provides a review of the water pollution assessment methods in water footprinting and analyses their modelling choices and resulting effects on the WF. With regard to the identified inconsistencies, we reveal the urgent need for a guidance for the methods application to provide robust results and allow a consistent evaluation of the water quality in water footprinting.

中文翻译：

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解决水足迹中的水质问题：现状、方法和局限性

与耗水量相比，迄今为止，水污染在水足迹方面的关注较少。与最近已达成共识的缺水影响评估不同，在如何解决水足迹中的水质恶化问题上尚未达成一致。本文概述了用于计算与水污染相关的影响的现有水足迹方法，并使用说明性示例讨论了它们的优势和局限性。这些方法被描述并应用于纺织加工中产生的废水的案例研究。对具有不同水质参数的两种情景的结果进行相互评估和水资源短缺足迹 (WSF)。最后，方法论方面，分析和讨论了每种方法的优点和局限性，并提供了对方法应用的建议。存在两种一般影响评估方法来解决水足迹中的水质问题：水降解足迹 (WDF) 计算与释放的污染物在环境中的传播及其被人口和生态系统吸收相关的影响，而水资源可用性足迹 (WAF) ) 当不能使用受污染的水时，量化与缺水相关的影响。总的来说，确定了七种在水足迹中考虑水质的方法，它们依赖于 WDF、WAF 和 WSF 中的一种或组合。方法范围在清单要求和提供的结果（单分或多个影响类别）方面存在显着差异。案例研究表明，对于哪种情景对水污染的危害较小，这些方法提供了相互矛盾的结果。本文回顾了水足迹中的水污染评估方法，并分析了它们的建模选择和对 WF 的影响。对于已识别的不一致之处，我们揭示了迫切需要为方法应用提供指导以提供可靠的结果并允许对水足迹中的水质进行一致评估。