Maximizing Benefits from Renewable Energy at Blue Plains AWWTP
Abstract:The District of Columbia Water and Sewer Authority (DC WASA) operates the Blue Plains Advanced Wastewater Treatment Plant (AWWTP) and can treat up to 370 mgd of wastewater as an average from the metropolitan Washington, DC area. It is the largest advanced wastewater treatment plant in the world. This project will maximize the use of renewable energy to produce power and steam at the Blue Plains AWWTP.
At the Blue Plains AWWTP wastewater is converted into stabilized biosolids, a renewable resource used as a soil amendment. Lime is used to produce these stabilized biosolids. However, a new project is being developed for the Blue Plains AWTP to utilize thermal hydrolysis and mesophilic anaerobic digestion (TH+MAD) to replace lime stabilization. Once implemented, this new process would provide the following advantages:
Digester gas (140 mm BTU/day) would produce heat & power simultaneously
Heat and power from digester gas would reduce existing air emissions onsite and from commercial power sources
Electrical power from digester gas (13 MW, year 2014) closely matches critical process requirements for the AWWTP, providing a reliable standby source of power when needed
Thermal Hydrolysis with Anaerobic Digestion reduces final biosolids by nearly 50%, dramatically reducing diesel fuel for hauling. (1,275 gal/day saved)
Lime stabilization is reduced to relatively infrequent peak conditions, reducing the use of lime which requires high energy to produce. (40 tons/day of lime saved)
Thermal Hydrolysis with Anaerobic Digestion produces a Class A product, expanding beneficial uses and reducing hauling.
WASA's Renewable Energy and Emissions Reduction Facility (REERF) is a combined heat and power (CHP) system using digester gas burned in gas turbines (GTs) followed by heat recovery steam generators (HRSGs) followed by steam turbines (STs). A steam boiler will also be utilized to ensure adequate steam production. Steam will heat the Thermal Hydrolysis/Anaerobic Digestion process scheduled for mid-2014 completion and replace some existing natural gas heaters currently used at the AWWTP.
Detailed cost evaluations were done to establish the most effective choices considering annual costs and capital costs. This led to creative funding options such as deferred bond payments after the facilities are built and operating to capitalize on the major annual operating cost savings.
This paper will describe the key features being planned for the Blue Plains AWWTP and how the production of electricity and steam will be maximized.
Document Type: Research Article
Publication date: January 1, 2010
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