UNSW Water Research Centre, School of Civil & Environmental Engineering, The University of New South Wales, Sydney, New South Wales, Australia.
Integr Environ Assess Manag. 2014 Jan;10(1):87-94. doi: 10.1002/ieam.1479. Epub 2013 Dec 10.
Chemicals are an important component of advanced water treatment operations not only in terms of economics but also from an environmental standpoint. Tools such as life cycle assessment (LCA) are useful for estimating the environmental impacts of water treatment operations. At the same time, LCA analysts must manage several fundamental and as yet unresolved methodological challenges, one of which is the question of how best to "allocate" environmental burdens in multifunctional processes. Using water treatment chemicals as a case study example, this article aims to quantify the variability in greenhouse gas emissions estimates stemming from methodological choices made in respect of allocation during LCA. The chemicals investigated and reported here are those most important to coagulation and disinfection processes, and the outcomes are illustrated on the basis of treating 1000 ML of noncoagulated and nondisinfected water. Recent process and economic data for the production of these chemicals is used and methodological alternatives for solving the multifunctionality problem, including system expansion and mass, exergy, and economic allocation, are applied to data from chlor-alkali plants. In addition, Monte Carlo simulation is included to provide a comprehensive picture of the robustness of economic allocation results to changes in the market price of these industrial commodities. For disinfection, results demonstrate that chlorine gas has a lower global warming potential (GWP) than sodium hypochlorite regardless of the technique used to solve allocation issues. For coagulation, when mass or economic allocation is used to solve the multifunctionality problem in the chlor-alkali facility, ferric chloride was found to have a higher GWP than aluminum sulfate and a slightly lower burden where system expansion or exergy allocation are applied instead. Monte Carlo results demonstrate that when economic allocation is used, GWP results were relatively robust and resilient to the changes in commodity prices encountered during the study period, with standard deviations less than 6% for all chlor-alkali-produced chemicals reported here. Overall outcomes from the study demonstrate the potential variability in LCA results according to the allocation approach taken and emphasize the need for a consensus approach to water sector LCAs.
化学品不仅在经济方面，而且从环境角度来看，都是高级水处理操作的重要组成部分。生命周期评估（LCA）等工具可用于估算水处理操作的环境影响。与此同时，LCA 分析师必须应对几个基本且尚未解决的方法学挑战，其中之一是如何最好地“分配”多功能过程中的环境负担。本文以水处理化学品为例，旨在量化 LCA 中分配方法选择对温室气体排放估算的可变性。本文研究和报告的化学品是对混凝和消毒过程最重要的化学品，结果基于处理 1000 毫升未经混凝和消毒的水进行说明。最近的生产这些化学品的工艺和经济数据，以及解决多功能性问题的替代方法，包括系统扩展和质量、火用和经济分配，应用于氯碱厂的数据。此外，还包括蒙特卡罗模拟，以全面了解这些工业商品市场价格变化对经济分配结果的稳健性。对于消毒，结果表明，无论使用哪种技术来解决分配问题，氯气的全球变暖潜能（GWP）都低于次氯酸钠。对于混凝，当使用质量或经济分配来解决氯碱设施中的多功能性问题时，发现三氯化铁的 GWP 高于硫酸铝，而当应用系统扩展或火用分配时，其负担略低。蒙特卡罗结果表明，当使用经济分配时，GWP 结果相对稳健且对研究期间遇到的商品价格变化具有弹性，所有报告的氯碱生产化学品的标准偏差均小于 6%。总的来说，这项研究的结果表明了根据所采用的分配方法，LCA 结果的潜在可变性，并强调需要对水部门的 LCA 采用共识方法。
