Decentralized Systems

When Distributed Systems Make Sense

Until recently, planners considered decentralized wastewater management an option only for rural and less densely populated suburban areas where publicly owned and operated sewer service was not available. Recent experience and research, however, has shown that a variety of decentralized approaches are efficient and effective when used in tandem with centralized management, often referred to as a distributed system. In fact, cluster systems and other distributed approaches can meet the needs of a community cost effectively and with improved performance and environmental sustainability, particularly when there are constraints on a centralized approach.

A recently completed WERF research project, When to Consider Distributed Systems in an Urban and Suburban Context (DEC3R06), resulted in several products to help determine whether a decentralized approach makes sense for a given community.

Differing Needs to Distributed Systems

The project team, led by Victor D’Amato, PE, of Tetra Tech Inc., analyzed 20 case studies where distributed approaches are being used to provide integrated water (wastewater, stormwater, reclaimed water) services across a range of community-specific situations and management frameworks. An analysis of these case studies showed how green developers, independent communities, and municipal utilities are responding to the unique drivers behind the implementation of distributed systems.

For green buildings and sustainable sites, distributed systems are being integrated into buildings and landscapes used to help conserve, recover, and reuse water, nutrients, and energy within facilities. These systems also provide good opportunities to support education and recreation.

Independent communities are using distributed systems to both maintain fiscal control and preserve their community character by preventing the uncontrolled development that can come with sewer availability if proper zoning restrictions are not in place. And traditional municipal utilities are incorporating distributed infrastructure into their asset portfolios by managing cluster and other decentralized systems, and using satellite systems and sewer mining to enhance opportunities for reuse and build synergies through physical interconnection with existing collection and treatment systems.

The Right Tools for the Right Decision

This project resulted in several products that can help planners, utility managers, engineers, developers, regulators, and other decision makers determine whether they should consider using a decentralized approach in their communities. These products include a tool that allows users to rank their communities’ objectives and priorities and determine whether a distributed approach makes sense in their community. Also developed through the project are a research digest that summarizes the findings of this research, three summary documents that provide in-depth analysis of the drivers behind the decision to select a distributed approach, and summaries of each of the 20 case studies.

All of these items, including the original database used to capture the details of this research, will be available in May 2010 on both the WERF and National Decentralized Water Resources Capacity Development Project (NDWRCDP) websites ( and

WERF thanks Elizabeth Striano of A Green Footprint, LLC for contributing this article.