Fueling Biogas Production at the Nansemond Treatment Plant With Fat Oil and Grease Through Advanced Anaerobic Digestion

The Hampton Roads Sanitation District (HRSD) currently manages all the solids produced from nine major wastewater treatment plants by a combination of incineration, land application, and composting. A recent district-wide solids management study undertaken by HRSD recommends a number of improvements at the Nansemond treatment plant. These improvements include:Additional anaerobic digesters to digest primary and waste solids.New thermal drying facility for digested solids.Improvements to existing dewatering facility to integrate with thermal drying facility.The recommended improvements represent a switch in the biosolids management strategy from primarily incinerating dewatered solids from the Nansemond plant at the Boat Harbor treatment plant to producing thermally-dried granules which are marketable as a Class A biosolids product. Through an RFP process, HRSD elected to implement composting as a turnkey project instead of thermal drying. In another study, the need to dispose of fat oil and grease from the treatment plants was established. This paper describes the improvements undertaken at the Nansemond treatment plant to address these changes.