Challenges in Starting up and Operating Attached Growth Denitrifying Process

Attached growth systems have biomass attached to media and are retained as opposed to being in suspension and be recycled; MBBR and IFAS are two of the examples of attached growth systems. Moving Bed Biofilm Reactors (MBBR) are innovative technology but are relatively new for United States. These are currently being used at few wastewater treatment plants in the country. MBBR system was designed and installed at 67-mgd Noman M. Cole, Jr. Pollution Control Plant (NMCPCP) located in the Chesapeake bay watershed to achieve a total nitrogen (TN) effluent concentration of 3.0 mg/L. MBBR was selected for use at this plant as a final polishing step. The plant provides BNR (Biological Nutrient Removal) before the MBBR process. At this plant, MBBRs remove nitrate (NO3-N) in an anoxic environment using supplemental carbon (methanol or analternative). The technology was demonstrated and met the effluent requirement on a pilot-scale test carried out at this plant before it was selected as a viable alternative for ENR (Enhanced Nutrient Removal). The MBBR process has been operating successfully since summer 2013 and is achieving the TN effluent goal. As is common with new and innovative technologies, there were several issues and challenges that were overcome during the construction, equipment startup, biological startup and full-scale operation. The paper presents the process and performance testing, challenges and lessons learned during the startup, and approximately one year of operation of the MBBR.