The concept of decentralization is far from novel. For quite some time now, the power grid system has been actively exploring decentralized or distributed energy grids to enhance energy reliability and security, particularly in the face of natural disasters and malicious attacks. This paradigm shift towards decentralization isn't confined to the energy sector; it is also gaining significant momentum within the water sector. This momentum is driven by the pressing need to enhance water supply in regions grappling with water scarcity, ensure compliance with environmental regulations, and align with the principles advocated by the OneWater approach.
Decentralized water systems are designed to collect, treat, and reuse water in close proximity to the source and point of use. The source water for these systems can encompass household and industrial wastewater, stormwater, rainwater, or even agricultural runoff. The modular treatment can be tailored to a wide range of scales, spanning from individual homes, clusters of homes, subdivisions, and commercial, industrial, and agricultural facilities. The treated water finds a diverse range of applications, from non-potable uses like toilet flushing to indirect potable use s such as groundwater replenishment, and even direct potable uses, including drinking water.
In my previous publication on Nature Sustainability, I demonstrated the benefits of a hypothetical hybrid water supply system in Houston, TX (see figure below). This hybrid system integrates centralized sources with distributed supplies of reclaimed wastewater treating to drinking water standards from nine wastewater treatment plants (e.g., direct potable reuse). Compared to a centralized system, the hybrid system has shown the potential to decrease dependence on surface and groundwater, reduce energy consumption for water transmission, and mitigate the risk of water quality deterioration during transport.
In my recent publication on Nature Water, I continued the same hybrid configuration and examined how resilience such system is to different types of disruptions, including pump power outage, pipe leakage, and source water contamination.
Overall, we found that a hybrid system did a better job supplying safe water and avoiding low flows across the city than the centralized system, particularly in areas where low water pressure is common. The negative impact caused by disruptions display lower severity, impact range, and downtime for the hybrid system. The configuration is important. For example, a pump outage at Houston’s Northeast Water Purification Plant caused the greatest drop in system-wide water flow among the city’s three water treatment plants in our simulation. But if the system was supplemented with a modular reclaimed water treatment facility near that plant, we found that that the additional water supply would significantly reduce the extent of the disruption.
While water reuse currently constitutes less than 1% of the total water usage in the U.S., there is a growing momentum across various scales, from small to large, to embrace and implement water reuse practices. With climate change fueling extreme storms and making water supplies less reliable in many areas, centralized systems paired with distributed water reuse could provide water security and increase urban water resiliency. As federal funds pour in to revitalize America’s water infrastructure, U.S. cities have a golden opportunity to bolster their large water systems with a decentralized approach.
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