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When water reuse projects are studied, cost-benefit analyses often only consider internal benefits, and not external ones, like the tourist value of beaches when sewage pollution stops.

Traditional economic feasibility studies tend to focus exclusively on internal costs, missing out on much of the value that water reuse brings to the table

Economic feasibility studies often decide the fate of water reuse projects, but the assessment methods generally weigh internal costs such as distribution and treatment requirements much more heavily than external benefits like environmental impact and increased tourism. As a result, many proposed water reuse projects are inaccurately given negative, marginal, or lukewarm assessments when they clearly would create economic benefit far outweighing the investment.

A recent study by researchers from the University of Valencia and Pontifica Universidad Católica de Chile established a theoretical methodology, which included both internal and external economic impacts, and applied it to 13 wastewater reuse projects in Valencia, Spain.

The research team found that when only internal benefits were considered in these cost-benefit analyses, only a portion of the projects were found to be economically viable. However, when external benefits were included, all 13 were deemed to be economically viable. The team concluded that economic feasibility assessments for water reuse projects should consider environmental benefit and resource availability, as well as economic benefits.

Positive Environmental Benefits of Water Reuse

Another recent study out of Palermo, Italy, examined cost-benefit analysis methodology for water reuse projects. The research team identified a number of wastewater reuse benefits:

Besides benefits associated to increased water availability for irrigation, reuse projects of urban water can also provide positive environmental impacts, as they contribute to improve water quality of the receiving bodies by diverting wastewater from their outlet. This represents a typical win-win situation where significant synergies can be achieved between urban and agricultural sector, and the environment.

The research team focused on a wastewater reuse project in Puglia, in the south of Italy. The coastal area has been seeing an uptick in recreational activity centered on a strip of beach. A nearby wastewater treatment plant reclaims wastewater for irrigation rather than discharging into the ocean, where pollution could limit beach activity.

In this scenario, the team found that a cost-benefit analysis that ignores non-use benefits –such as aesthetic enjoyment of cleaner water in the reclaimed stretch of beach — will inaccurately find the project unsustainable. Incorporating the benefits of the reclaimed beach into the cost-benefit analysis decisively tipped the scales in favor of the project.

Case-by-Case Basis

The study acknowledges that most benefits of reuse are both site- and context-specific. Local regulatory frameworks, water costs, and water availability are generally considered when deciding the feasibility of a water reuse project, but environmental benefits are rarely quantified.

Another study out of Ardhi University and The Nelson Mandela African Institute of Science and Technology in Tanzania found:

[T]here is no universal way that can fit all cases due to difference in local circumstances. The main challenge is on […] comprehensive evaluation and valuing of the environmental benefits.

The researchers identified wastewater reuse benefits as mainly related to recovered natural resources, improved production in agriculture, and the environment.

When Is Water Reuse Feasible?

Water reuse is clearly worthwhile in a growing number of scenarios. For instance, in small island developing states (SIDS) in the Caribbean, pristine beaches bring in tourist dollars. Irrigation water often is scarce and 85% of wastewater is discharged into the Caribbean untreated. In such cases, it’s clear that reuse is likely to be economically sustainable. And now, with smaller decentralized wastewater treatment plants like Fluence’s Aspiral™, local reuse is much more affordable than ever.

It’s time to widen cost-benefit analyses to consider the true scope of water reuse’s benefits. Researchers have reinforced the idea that it no longer makes sense to discharge water after the first use. Contact Fluence to learn more about making every drop of water count — more than once.

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