The Best Carbon for the Job: Using the 2010 WERF Protocol to Choose an External Carbon Alternative for Enhanced Nitrate Removal

The City of Boulder, Colorado is among many facilities across the United States that is faced with the challenge of improving denitrification performance to meet future discharge permit limits when its current process is carbon limited. The city successfully implemented the Water Environment Research Foundation’s “Protocol to Evaluate Alternative External Carbon Sources for Denitrification at Full-Scale Wastewater Treatment Plants ” (Protocol), surveying a host of locally available waste products and commercially available external carbon supplements. Top alternatives included tofu whey, brewery weak wort, MicroC2000, methanol, and acetic acid. Through a phased evaluation detailed in the Protocol, the city was able to identify a combination of two carbon sources (acetic acid and brewery weak wort) that will give the reliability and immediate effectiveness required to meet daily maximum nitrate limits while leaving the opportunity for mutually beneficial local public-private partnerships that have the potential to reduce O&M costs and greenhouse gas emissions.