Shenandoah – Wastewater Treatment Plant Evaluation
Benesch evaluated the existing 2.0 million gallons per day wastewater treatment plant, built in 1975, which utilizes the conventional activated sludge process as secondary treatment and consists of influent headworks, primary clarification, aeration, final clarification and chlorine disinfection.
Benesch identified and evaluated options to upgrade the existing facility or construct a new facility. Special consideration was given to new nitrogen and phosphorus removal requirements under the Chesapeake Bay Strategy. Upgrade alternatives included providing a parallel treatment train to the existing facility, replacing anaerobic digesters with aerobic digesters, installing an automatically-cleaned influent bar screen and converting the chlorination system to UV disinfection.
New facility options identified a sequencing batch reactor (SBR) as the most feasible and economical option. Life-cycle costs (20-year design life) determined similar costs for upgrading the existing facility or constructing a new facility at $24M each. The chosen design facilitated the continued operation of the plant during construction. In order to move the project forward, Benesch negotiated a Consent Order & Agreement with the Environmental Protection Agency.
