Mystic Takes (a) Charge: Startup of the BioMag Process

The Mystic Water Pollution Control Facility (WPCF) in Stonington, Connecticut was faced with the need to upgrade its wastewater treatment process to achieve nitrogen removal to meet the General Permit for Nitrogen Discharges, without constructing any new tankage. An emerging technology, the BioMag system marketed by Evoqua Water Technologies, was implemented to meet this challenge. The BioMag process utilizes a magnetite-ballasted mixed liquor process to operate at a mixed liquor suspended solids (MLSS) concentration much higher than conventional activated sludge systems. After the completion of a successful full-scale demonstration at the Mystic WPCF in 2010, a permanent system was constructed in 2014 as part of an overall plant upgrade. Since startup the facility has achieved a total nitrogen (TN) effluent concentration of less than 5 milligrams per liter (mg/L) on a consistent basis. Lessons learned at startup and during operation include foam control considerations, biological solids capture efficiency, the influence of polymer and potential impacts on the performance of downstream ultraviolet (UV) disinfection.