What Role Can Decentralized Water Reuse Play in Tackling Water Scarcity?

By Christian Bonawandt

Onsite and localized reuse expand the practice overall, which will be essential for long-term security.

On June 1, the White House released two reports addressing water scarcity in the U.S. and abroad. The first of these, the Drought Resilience Interagency Working Group’s (IWG) Summary Report,¹ outlined a working plan and budget for various federal agencies to allocate resources to drought-stricken areas of the country and reduce both the health and economic impacts of water scarcity. The second, the White House Action Plan on Global Water Security,² takes a more high-level approach, identifying policy direction and methods that support the development of relevant government and nongovernmental organization (NGO) strategies.

Both reports mention water reuse and recycling as core tools for tackling scarcity. In support of the effort, the U.S. Department of the Interior, which is part of the IWG, has earmarked $1 billion in grants specifically for water reuse projects for Fiscal Year 2022.³

Some cities have already built reuse into their water infrastructure, with more slated to vastly expand reuse over the next decade. The City of San Diego, for example, recently broke ground on the $950-million East County Advanced Water Purification Program — just one of three planned reuse facilities⁴ to support local water security. However, such large-scale reuse projects, and the accompanying price tags, can be out of reach for many municipalities.

Given this, decentralized water reuse can play a key role in reducing communities’ dependence on source water. The value of decentralized wastewater treatment has been well established and includes:

• Lower upfront investment. As the site needs only to serve key parts of the community, not the full population, decentralized projects are smaller and more affordable to build than a full reuse facility.
• Reduced strain on older/existing infrastructure. Some decentralized facilities can redirect flows away from existing pipelines, particularly those that are older and more prone to fail under duress.
• Access to different technologies. Depending on the gallons per day (GPD), the site may be able to utilize technologies, such as reverse osmosis (RO), that are more effective at lower flow rates than those commonly experienced in larger facilities

Private Sector Inspiration

Several successful decentralized water reuse projects have been executed in the U.S. over the past few years. Many of these projects are ideal case studies in environmental leadership and innovation.

Salesforce Tower. Completed just last year, after numerous COVID-induced delays, Salesforce Tower is not only the tallest skyscraper in San Francisco, but it is also home to an ambitious private water reuse project. Salesforce Tower is a blackwater system, meaning it reuses all of the building’s wastewater, including from the toilets. The treatment process involves aerobic screening, biological treatment, UV and chlorine disinfection, and total dissolved solids (TDS) and nutrient removal. The recycled water is used throughout the building, including in toilets, sinks, and cooling towers. Only fresh potable water is pumped in. Overall, 75% of its total water is reused, saving 30,000 GPD, or 7.8 million gallons per year.

Salesforce Tower’s blackwater system is part of a nationwide recycling trend.

Emory University. Just outside Atlanta, Emory University has offset 40% of its water consumption (146 million gallons annually) with a reuse system it calls the WaterHub, which relies heavily on natural biological processes. Wastewater flows through a series of flora-based bioreactors. This artificial wetland allows specially selected plant life to consume and break down biological waste and other contaminants. Water is then pumped to small greenhouse-like housing units where it is treated with a combination of UV sterilization and chlorine disinfectant. The recycled water is used in steam and chiller plants, which heat and cool more than 70 buildings, as well as for flushing toilets in residence halls.

Smithsonian Environmental Research Center (SERC). Research facilities like SERC are large consumers of both energy and water. SERC reuses 20,000 GPD of graywater (wastewater sans toilet flushes), employing a sequencing batch reactor (SBR) and microfilter (MF) followed by UV and chlorine disinfection. Water that is used in laboratory experiments is further filtered through an RO system for ultrapure water. The rest is used for firefighting, toilet-flushing, and filling stormwater ponds.

The clear pattern is that many of the biggest innovations in water reuse are occurring in the private sector. Municipalities will need to tap into this trend by finding ways to mandate or encourage commercial industry and NGOs to invest in onsite, decentralized water reclamation.

Water treatment plants (WTPs) and wastewater treatment plants (WWTPs) can aid in this process by making their own expertise available whenever possible to help private entities learn more about the technologies and best practices in water treatment, as well as how best to construct facilities that reduce the strain on existing infrastructure. After all, we are all part of the same water cycle in one way or another, so it’s in everyone’s best interest to ensure that decentralized water reuse projects continue to expand and succeed.

References:

1. https://www.whitehouse.gov/wp-content/uploads/2022/05/DroughtIWGReport_Final_EmbargoedUntil-June-1-at-6AM-ET.pdf
2. https://reliefweb.int/report/world/white-house-action-plan-global-watersecurity
3. https://www.usbr.gov/bil/docs/spendplan-2022/Reclamation-BIL_Spend_ Plan_2022.pdf
4. https://timesofsandiego.com/life/2022/06/01/officials-break-ground-on-eastcounty-advanced-water-purification-project/

About The Author

Christian Bonawandt is an industrial content writer for Water Online. He has been writing about B2B technology and industrial processes for 22 years.