Actualizing the sustainable & economic benefits of onsite non-potable water systems
Extreme drought and water shortages in major cities such as Cape Town, South Africa; São Paulo, Brazil; Los Angeles, and Beijing, China, have brought international attention to the fact that the world’s water resources are finite. Changing climates, prolonged drought and population growth are putting increased pressures on urban water supplies. Many cities interested in becoming more water efficient are turning to water recycling and reuse to maximize valuable potable supplies and meet demand challenges.
Water recycling and reuse projects vary in purpose and scale, ranging from municipal-scale recycled water projects, to the use of recycled water to recharge aquifers, and even water capture and reuse for household laundry-to-landscape systems. Onsite non-potable water reuse is an emerging strategy for conservation and efficiency in commercial and mixed-use buildings. These systems rose in popularity as an approach to building drought resilience in Australia, and have since been explored in cities including New York, San Francisco, Seattle and Tokyo.
Onsite non-potable water systems collect wastewater, storm water, rainwater and more, and treat it so that it can be reused in a building or across multiple buildings, for non-potable purposes such as cooling, irrigation, and flushing toilets and urinals. These systems shift the way we think about water use in urban communities and allow buildings to customize approaches to water conservation by offsetting valuable potable water supplies.
While interest in onsite non-potable water systems grows, implementation has been stymied due to a lack of standards or guidance to govern the development and operation of these systems. Currently, national water standards or guidelines for onsite non-potable water systems in the U.S. do not exist. Some states have varying degrees of standards in place, but the standards are limited and water quality criteria varies. At the same time, recycled water policies do not provide the appropriate level of guidance for water quality treatment standards, reporting or monitoring requirements for these systems.
To address these barriers and accelerate the adoption of onsite non-potable water systems, 35 leaders from municipalities, water utilities, and public health agencies from 11 states and Washington, D.C., have come together to form the National Blue Ribbon Commission for Onsite Non-potable Water Systems. The commission is convened by the U.S. Water Alliance and the Water Research Foundation, and is chaired by the San Francisco Public Utilities Commission. The commitment from national partners and local leaders across the country demonstrates the willingness of the industry to move toward a new paradigm of sustainable water management in buildings.
“Guidebook for Developing and Implementing Regulations for Onsite Non-potable Water Systems” builds upon research guided by an independent advisory panel of public health and water quality experts, and was published by the Water Reuse & Environment Foundation in “Risk-Based Framework for the Development of Public Health Guidance for Decentralized Non-Potable Water Systems.” Both publications represent progress in establishing industry-backed standards for regulating and managing onsite non-potable water systems. The research presented in the risk-based framework and the guidance and model policies outlined in the guidebook establish water quality standards and criteria for these systems.
Paving the Way
Many of the parties represented on the National Blue Ribbon Commission have been working together since 2014 to advance best management practices that support the use of onsite non-potable water systems in commercial and mixed-use buildings. Together they published “Blueprint for Onsite Water Systems: A Step-by-Step Guide for Developing a Local Program to Manage Onsite Water Systems” to serve as a how-to guide for communities interested in creating a program for governing onsite water treatment.
From these works, some key best practices have emerged for those interested in deploying onsite non-potable water systems—either through a municipal program or as an individual building owner. One is to take a risk-based approach to water treatment to protect public health. Onsite non-potable water systems are reimaging how various water supplies can serve several end uses, but protecting public health is paramount.
As outlined in the guidebook, the water quality standards should be defined based on the alternate water source, such as roof runoff, storm water, blackwater, and greywater, and the non-potable end use, including toilet and urinal flushing, clothes washing, ornamental plant irrigation, and dust suppression. Regulations should apply the quantitative microbial risk assessment to evaluate the potential exposure and associated human health risks to govern systems. Considering source water quality and potential human exposure in the treatment design ensures these systems protect public health and meet future regulations.
Another key best practice is to take a proactive policy approach. Since national or state standards for onsite non-potable water systems do not currently exist, municipal agencies can take a proactive policy approach to pass local standards that establish regulatory frameworks for managing these systems and provide clear direction for project developers. The National Blue Ribbon Commission’s “Guidebook for Developing and Implementing Regulations for Onsite Non-potable Water Systems” discusses three policy vehicles for supporting the development and implementation of onsite non-potable water systems across state and local authorities. The report presents different management and oversight structures, as well as a model state regulation and a model local ordinance, which can be tailored and adopted by jurisdictions.
Consider partnering to establish a local program for ongoing oversight. The success of onsite non-potable water systems depends on strong collaboration across various stakeholder groups. In this case, coordination between water and wastewater utilities and public health agencies ensures projects protect public health and meet water quality standards. “Blueprint for Onsite Water Systems: A Step-by-Step Guide for Developing a Local Program to Manage Onsite Water Systems” captures best practices from leading public health agencies and water utilities to guide municipal agencies through the process of identifying alternate water sources and end uses, setting water quality standards, and establishing monitoring, reporting, and permitting processes.
Try approaching onsite non-potable water systems with a conservation philosophy to address revenue and system impacts. As municipalities consider how an uptick in onsite non-potable water systems may impact their system flows or decrease revenue, utilities should approach such considerations with a similar philosophy as other conservation programs. Onsite non-potable water systems provide another conservation measure that has the potential to yield demand reduction and cost savings, and there are proven strategies for addressing considerations related to wastewater flows, solid recovery, and revenue streams while promoting onsite systems.
Finally, consider promoting onsite non-potable water systems with developers as a green building strategy. The next generation of efficient buildings will need to incorporate water conservation and onsite non-potable water reuse is one way to meet this demand. Market trends call on utilities and local governments to create enabling policies and permitting processes to allow for these innovative systems to be deployed. This also is an opportunity for utilities to explore public-private partnerships with developers to shift costs, share risks and reach mutually beneficial goals.