Why Circular Water Systems Are Key to Sustainable Urban Growth

As urban populations continue to grow, pressure on water resources intensifies, leading to widespread water scarcity. To address this challenge, cities must look to alternative sources of water.

One promising solution is decentralised, or onsite, water reuse technologies. These systems capture and treat water generated within or around a building—such as wastewater, greywater, stormwater, or rainwater from roofs—and reuse it locally.

This reduces demand on centralised supplies, eases the strain on ageing infrastructure, and promotes efficient, sustainable water management.

Moving Beyond the Linear Water Model

In a recent article, Robert Brears highlights how onsite water reuse systems can improve climate resilience, enhance urban sustainability, and help cities better withstand the impacts of drought and extreme weather. He argues that the traditional linear approach to water—extract, use, dispose—is no longer sustainable in an age of rapid urbanisation, climate change, and resource constraints.

Instead, Brears advocates for a circular water economy, a closed-loop model that maximises water recovery and reduces waste. This approach not only benefits the environment but also strengthens urban resilience.

New York City as a Model for Incentives

Brear highlights New York City’s onsite water reuse grant pilot programme, which provides incentives to commercial, mixed-use, and multi-family residential property owners to install water reuse systems.

New York City’s Department of Environmental Protection provide grants for commercial, industrial, and multi-family residential property owners with incentives to install fixture retrofits and other water efficiency technologies, such as onsite water reuse systems, totalling $50,000 or more on a single private property, and up to $250,000 for building-scale and $500,000 for district-scale projects.

The programme aims to encourage the installation of water reuse systems in commercial, mixed-use, and residential properties, setting a benchmark for urban water security and sustainability.

Click the link to know more about NYC Environmental Protection water conservation and re-use grants.

Ensuring Safety Through Research

To promote the safe use of decentralised, recycled, or reused water for non-drinking purposes, the US Environmental Protection Agency (EPA) has developed risk-based models. These models assess the health risks associated with using locally collected water sources, such as wastewater, greywater, stormwater, and rainwater, around buildings. They also help determine the necessary treatment to ensure this water is safe for reuse in non-potable applications.

The EPA published several studies on:

• Identifying and measuring these microorganisms in locally collected wastewaters and ensuring they are removed similarly to pathogens during treatment
• Monitoring the treatment processes in onsite non-potable water reuse systems (ONWS) to ensure that recycled water is treated effectively, reducing pathogens and ensuring its safe application. The research involves describing and quantifying the microorganisms, both bacterial and viral, found in these locally collected wastewaters, and
• The life cycle assessment of these systems, which includes the costs of installing and operating ONWS at different scales and types, is compared against the benefits, such as savings from reduced drinking water costs.

Click the EPA page to view the Onsite Non-Potable Water Reuse Research.

According to Brears, “Scaling up onsite water reuse and adopting the circular water economy are essential for creating resilient and sustainable cities. By investing in advanced technologies, offering targeted incentives, and fostering collaboration across sectors, urban areas can ensure reliable water supplies, reduce waste, and enhance their ability to adapt and thrive in the face of future challenges” (Brears, 2025).

Water scarcity cannot be solved by relying on outdated, linear models of extraction and disposal. Cities must embrace innovation, collaboration, and bold policy shifts that prioritise decentralised water reuse and the circular water economy. By learning from initiatives like New York City’s incentive programme and applying cutting-edge research from the EPA, urban centres can unlock a future where water is not wasted but continually renewed.

This is more than just a technical fix—it is a blueprint for resilience, sustainability, and survival in an age of climate uncertainty. Every litre saved and reused strengthens the foundations of thriving cities and secures water for generations to come. The challenge is urgent, but the solutions are within reach. What remains is the will to act.