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New Report: Urban Recycled Water Use in California by Sharona Sokolow

By sharona Sokolow. California is currently in the middle of its most severe drought of the past fifty years. With the onset on climate change, the state can expect a future of more serious and prolonged droughts into the future. A method to combat the effects of climate change and increase the sustainability of water supplies is through use and expansion of recycled water. Despite successes both inside and outside the United States, recycled water is not as prevalent in California as it could be. Today, in response to California’s severe drought, legislation is promoting and incentivizing expansion of recycled water. With this inevitable expansion, it is important to understand how recycled water can affect human health.

Historically, one reason for the limited scope of recycled water within California is the lack of public support. Although treatment technologies produce water that meets or exceeds drinking water standards, the public has not embraced the use of recycled water, citing concerns that the water is unsafe or tainted. While concerns over water quality are very real, it is important to understand how implementing changes to California’s recycled water system can affect health on a broader scale. To address this issue, I recently wrote a report entitled “Urban Recycled Water Use in California: A Briefing Paper on Status, Opportunities for Expansion and the Environmental Health Benefits.”

Recycled water, an umbrella term for the product of highly treated wastewater, can be categorized by two types of use: potable reuse (water treated for human contact and drinking purposes) and non-potable reuse (water treated for uses without human contact). There are two types of potable reuse: indirect and direct. Indirect potable reuse (IPR) treats wastewater, and then injects the treated water into an environmental buffer, such as a lake, river, or groundwater, before it is reintroduced into the potable water supply. Alternatively, direct potable reuse (DPR) introduces treated wastewater directly into the potable supply with the support of an engineered buffer system.

Integrating potable reuse into the water supply is a feasible method for counteracting consequences of climate change, drought and population rise. Using wastewater as the source for recycled water allows source water to be in constant supply and thus impervious to the effects of climate change. Wastewater is a local water source thus lessening the need for costly, energy intensive imported water. In addition to lower cost, potable reuse limits potential system interruptions, such as those from deteriorating conveyance infrastructure within California’s primary imported water source, the State Water Project. These two factors render recycled water a feasible, cost effective solution for supporting California’s projected population rise from its current 37 million to 60 million people by 2050.

Potable reuse (direct much more so than indirect) is less energy intensive than current imported water sources, and much less energy intensive than implementing desalination, the conversion of seawater to potable water (See Figure 1). The lower energy intensity of potable reuse will correspond to a decrease in greenhouse gas emissions and thus help protect and improve air quality.

Further, as water and energy sources become scarcer, future water and energy costs will rise. These higher utility costs will disproportionately affect lower income communities where financial security is a precursor to health outcomes such as increased stress and exacerbation of existing health conditions, such as heart disease. Potable reuse will be a cheaper water source than other options, especially when compared to potential alternative water sources such as desalination, which has much higher operation costs.

Among the most prominent non-potable uses, large-scale landscape irrigation has the potential for the most significant impact on water use and holds the most benefit for human health. With water use regulations and mandatory irrigation cutbacks becoming more prevalent in response to drought, implementation of recycled water will also help irrigate and maintain green spaces. Green space is beneficial for preventing urban hot spots and urban heat island effect, which is especially significant given predictions for warmer temperatures and extreme heat events in the future; prevention of urban hot spots and urban heat islands also have a positive impact on air quality and respiratory disease. Availability of green space also has positive impacts on promoting physical activity and related health outcomes such as obesity, heart disease, elderly health, and mental health.

It is my hope that with greater understanding recycled water’s benefits, the public will become more accepting of its use, and California can work to maximize its water supply for the future.

The full report goes into greater detail, but recommendations for local water districts and public health agencies are as follows:

  • Explore incentives for building up infrastructure to support recycled water systems to widen their geographic reach within communities.
  • Encourage local water suppliers to apply for funding within California Proposition 1 to expand their recycled water portfolio to include potable reuse projects.
  • Foster collaboration between local water suppliers and public health departments to improve public perception of recycled water implementation and expansion.
  • Develop outreach programs and materials to inform public about recycled water programs.
  • Develop uniform terminology when discussing recycled water programs to avoid confusion, which may help gain public acceptance.
  • Incentivize and promote rebates for water reuse in landscape irrigation, both in public and residential spaces.
  • Promote expansion of recycled water systems for irrigation, thus maintaining green space for physical activity, and reducing potential for urban heat island effect.
  • Encourage water districts to collaborate with neighboring districts to expand reach of recycled water when connections are nearby service area borders.

The full report can be downloaded here: Link.