Design-Build Team Members
Johnston Construction Company led the design-build team providing engineering, construction, and commissioning services for the $472,000 public bid fixed price contract for the anaerobic digester mixing system.
The project involved modifications to the existing 65 foot diameter primary anaerobic digester at the Frederick Wastewater Treatment Plant located in Frederick, MD. The digester mixing system was added to improve digestion of secondary sludge prior to dewatering and disposal. Performance requirements included a minimum sludge volume turnover of seven times per day and no more than a one degree-F variation in sludge temperature as measured in the four quadrants of the digester.
Modifications included the design and installation of digester sludge suction and discharge piping inside the existing digester. A masonry building was constructed onto the side of the anaerobic digester to house the digester sludge mixing equipment consisting of one Hayward Gordon 60 HP chopper pump, seal water system, controls, and associated piping. The scope of work also included the installation of telecommunication, HVAC, and electrical systems.
The project was started in January 2006. Final design, construction, and performance testing was completed in September 2006.