Triple Bottom Line Comparison of Potable Reuse and Other Water Supply Options

Authors:

  • Ben Stanford, Alan Karnovitz, Grace Johns, Michalis Hadjikakou, Stuart Khan, Hazel Rowley, Tommy Wiedmann, Stephanie Ishii

An online survey was disseminated through the WRRF to assist in developing the TBL tool and methodology.

Direct and Indirect Potable Reuse (DPR and IPR, respectively) are increasingly being considered as two of many possible water supply options for water utilities in various locations throughout the US. However, as with any new water supply, potable reuse needs to be considered vis-à-vis other technologies or solutions, including a ‘no action’ scenario to determine the true value and economic impact of that supply option. To improve public acceptance and stakeholder support, it is critical that such comparisons be completed in a transparent, publicly accessible manner to facilitate management-level decision making, as well as public engagement and education about the water supply options. This calls for a comprehensive and objective evaluation methodology for comparing alternative water supply options, which lends itself to a triple bottom line (TBL) framework.

The TBL framework provides an established accounting approach for concurrently quantifying economic, environmental, and social implications for any business decision or project. At a time when companies and other organizations are expected to operate on the basis that long-term profitability should go hand-in-hand with social justice and environmental protection, TBL offers the ideal framework to ensure sustainable decisions. For water and wastewater utilities and other water-related authorities, TBL represents a widely accepted, transparent, and defensible means to compare the total (economic, environmental and social) benefits and costs of any investment vis-à-vis other alternatives, including the option of taking no action.

Through a WateReuse Research Foundation funded study, we are developing a specialized TBL tool and associated methodology that goes beyond conventional practices to evaluate water supply options. This work uses a hybrid life cycle assessment (LCA) method that includes three core components: 1) process LCA, 2) economic input-output modeling with environmental extensions, and 3) Social Impact Assessment. The hybrid LCA approach uses process LCA to estimate cots itemized by inputs, thus enabling the identification of all system flows, e.g., chemicals, equipment, labor. The hybrid LCA approach also benefits from input-output lifecycle assessment to quantify environmental impacts and draws upon the social sciences to provide quantitative measures of social indicators, such as resilience to drought, ratepayer acceptance, and project risk factors. The framework engages stakeholders throughout the process and ensures standards of accountability to minimize “gaming of the system” in which decision making criteria are weighted in such a way to achieve a desired outcome. Working within an established TBL framework, we are using hands-on participatory workshops and utility case studies to define, test, and validate a methodology for comprehensive evaluation of the various supply options that incorporates stakeholder perceptions and value systems.

In this presentation, we will discuss the developed framework including the social, environmental, and economic indicators and our methodology for integrating a multi-criteria decision analysis component into the decision tool. We will demonstrate how this tool has been applied to at least one utility case study and discuss how findings from this study can be used to support water supply evaluations.

For more information, please contact the author at bstanford@hazenandsawyer.com.

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Horizons Fall 2017 (pdf)

Horizons showcases significant water, wastewater, reuse, and stormwater projects and innovations that help our clients to achieve their goals, and can help you achieve yours. Articles are written by top engineers and process group leaders, demonstrating and explaining the beneficial application of a variety of technologies and tools.

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