Water scarcity, population growth, and climate change are increasing the world’s focus on water reuse projects. The WateReuse Research Foundation recently released a report on the cost of overtreating reclaimed water.

By: Larry Schimmoller, CH2M HILL Global Technology Leader and Mary Jo Kealy, CH2M HILL Senior Principal Technologist

Mr. Schimmoller and Ms. Kealy participated in an October 2013 webcast for the WateReuse Association where they presented findings from the 10-01 study on the cost of overtreating reclaimed water.

As populations around the world continue to grow and communities appreciate the difficulty of securing new water supplies, water reuse is expected to expand in the coming years. Droughts and mounting community and regulatory pressures have also increased the application of water reuse.

Throughout the world, the level of treatment provided in water reuse projects varies significantly depending on a variety of factors including regulations, water quality, end uses of the treated water, and public influence. Selecting the appropriate treatment technology and level of treatment can be a complex decision and one which is often based on the perception that more advanced treatment is better. Recent experiences within the water reuse industry have demonstrated that governmental and nongovernmental organizations and advocacy groups can influence selection of a higher or more costly level of treatment than is fit for the water purpose. This is partially because of a failure to consider the full financial, environmental, and social elements of the triple bottom line (TBL). The reality is, however, treatment trains that are perceived as “more advanced” or “higher tech” do not always provide the optimal solution and can result in such high TBL costs that water reuse may be prohibitively expensive.

In a study for the WateReuse Research Foundation (10-01: Fit for Purpose Water: The Cost of Overtreating Reclaimed Water), the benefits and costs of applying different levels of treatment for potable reuse applications were examined. The study aimed to pair levels of treatment to the intended use, without expending unnecessary funds or energy or emitting excess greenhouse gas and other air emissions, while also minimizing other environmental and social costs.

As part of the project, CH2M HILL developed and applied a TBL framework to guide sound selection of which treatment process to utilize. Comparing two common potable reuse scenarios, the study considered microfiltration—reverse osmosis—ultraviolet advanced oxidation method (widely considered the “gold standard” for potable reuse), as well as an ozone-biologically active carbon—granular activated carbon—ultraviolet disinfection treatment (activated carbon based treatment is more prevalent in the eastern and central U.S.).

Evaluating three different plant capacities (5 mgd, 20 mgd, and 70 mgd) to determine the TBL costs for varying treatment plant capacities, the study provides a baseline for utilities to consider when thinking about implementing a water reuse project.

An economic cost-benefit analysis approach was used to identify and quantify the most significant TBL factors in dollars to inform reuse water treatment selections and avoid costly overtreatment. Treatment technologies were selected with the aim of providing comparable water quality to ensure the comparison was fair. The most influential TBL factors for potable reuse projects included:

  • Direct financial costs: construction, engineering, and annual operating costs
  • Upstream environmental and social factors: greenhouse gas emissions and other air emissions resulting from the plant’s electricity use and the production and transportation of chemicals required for water treatment
  • Downstream environmental and social factors: greenhouse and other air emissions and land requirements for transporting and disposing of salt and chemical solids at treatment plant site

Download the full report to see how TBL costs were developed for each scenario and how they impact which treatment option provides the best solution fit for the water’s purpose. Read the recent article by Bloomberg News to learn more about how water scarcity is causing U.S. communities to consider water reuse and recycling.

Larry Schimmoller, PE, is CH2M HILL’s Global Technology Leader for Water Reuse. He has extensive experience in planning, piloting, process selection, design, and construction of water treatment and water reuse projects. He is located in the firm’s Denver, Colorado office.

Mary Jo Kealy, PhD, is a Senior Principal Technologist at CH2M HILL, with more than 30 years of experience as a natural resource economist with specialized expertise in natural resource and environmental economics, benefit-cost analysis, and public economics. Mary Jo is located in the firm’s Philadelphia, Pennsylvania office.