Sustainable Solutions for the 21st Century – Integration of Water Treatment Systems with Energy Derived from Municipal Waste

Hillsborough County is a Florida municipality that has seen rapid growth and utility demands over the past 50 years. In response, it has implemented an innovative project to reduce the cost of wastewater and water treatment processes by using renewable electrical energy produced from municipal solid waste.The county developed a modern energy-from-waste (EfW) facility 27 years ago, recognizing that solid waste was capable of producing significant amounts of renewable energy in the form of electricity, and to limit landfill disposal. The electricity was sold to a local utility to help offset the costs of solid waste disposal to local rate payers. The EfW facility was also located adjacent to one of the county's advanced wastewater treatment plants (AWTP), allowing the county to take advantage of reclaimed water at the EfW facility for cooling, irrigation, and other process uses.Six years ago, faced with continuing growth, the county expanded their EfW facility by approximately 50 percent capacity. At this time, they also decided to disconnect the adjacent AWTP from the local electric grid and use renewable electricity supplied from their adjacent EfW facility to reduce the cost of wastewater treatment at the AWTP. This synergistic arrangement resulted in savings to both the Solid Waste and Water Resources Departments. Following the success of this initial project, the county expanded their internal use of their electrical power by adding a new electrical power feeder circuit to a nearby potable water booster station for additional shared savings.The Hillsborough County Florida success may serve as the catalyst for other municipal entities to develop integrated utility projects. The opportunities will vary greatly from one municipal utility to another based on local variables and markets. Ideally, all of the energy demand for a municipal utility's water and wastewater treatment processes would be met by electrical output from the EfW facility. The percent of internal use should be maximized in order to optimize the shared benefits.To evaluate whether this ideal synergistic arrangement could be feasible, an analysis was performed for three communities with population sizes ranging from small (176,000), medium (700,000) to large (2 million). The potential to match the electrical output from the EfW facility to the energy requirements of the water and wastewater processes was examined.