Full Scale Evaluation of an Alternate Carbon Source and Methanol for Low Level Denitrification at a Long Island Sound Water Pollution Control Facility

The Fairfield WPCF is a 9 million gallon per day (mgd) average annual daily flow treatment facility that is located in southwestern Connecticut and discharges directly into Long Island Sound (LIS). The treatment facility was upgraded in 2002 to include low level nitrogen removal as part of the Total Maximum Daily Load (TMDL) for Long Island Sound. The biological nitrogen removal treatment consists of three trains of a four stage suspended growth activated sludge process that include primary anoxic zones followed by aeration with internal nitrate recycle, second anoxic zones with external carbon addition, and reaeration zones.From 2003 until November 2007, Fairfield utilized methanol as the external carbon source for denitrification in the second anoxic zone. The plant operations staff chose to change from methanol to MicroC™, a proprietary non-flammable, non-hazardous alternate external carbon due to the safety concerns of utilizing a hazardous and flammable liquid onsite and the highly fluctuating cost of methanol.Both Methanol and MicroC™ were shown to improve denitrification when added to the post anoxic zone at Fairfield. MicroC™ can be utilized interchangeably with methanol with no appreciable acclimation period needed or modification to the existing chemical storage and pumping facilities.