Effect of Temperature on Biofilm Growth Dynamics and Nitrification Kinetics in a Full-Scale MBBR System

The Moorhead, Minnesota Wastewater Treatment Facility (WWTF) operates a moving bed biofilm reactor (MBBR) to comply with seasonal ammonia discharge limitations. Since becoming operational in 2003 it has shown the ability to reach high ammonia removal efficiency year round even though it is subject to the extreme temperature variations found in the upper Midwest. Monitoring data for attached biomass revealed dramatic changes from winter to summer months with large quantities of attached biomass in the colder months and significantly less in the warmer months. Monitoring results indicated that attached biomass, biofilm thickness, and biofilm morphology change significantly from warm to cold weather months. Attached biomass quantities were found to vary upwards of four and half times while biofilm thickness changed up to three times between the warm and cold weather months.