From Grease Trap Waste to FAME: Analyzing Long Chain Fatty Acids in Grease Trap Waste via Derivatization to Their Fatty Acid Methyl Esters

The Nansemond Wastewater Treatment Plant, located in Suffolk, Virginia is operated by Hampton Roads Sanitation District (HRSD), which treats and discharges approximately 30 million gallons per day into the James River, a major tributary to the Chesapeake Bay. Recent upgrades at the Nansemond Treatment Plant were completed to substantially reduce total nitrogen discharges to receiving waters. However, this new treatment necessitates the addition of large quantities of external carbon for effective denitrification, raising the operating costs by approximately $700,000 per year. HRSD is investigating the fermentation of long chain fatty acids (LCFAs) in grease trap waste (GTW) as a carbon source. To support this effort, HRSD’s Central Environmental Laboratory (CEL) developed a cost effective method for analyzing LCFAs with existing equipment and supplies. This method involves derivitization of LCFAs to fatty acid methyl esters (FAMEs) and subsequent analysis by gas chromatography and flame ionization detection (GC/FID). The FAME method has a linear working range from 10 to 1000 mg/L, detection limit of 0.39 to 2.53 mg/L depending on the specific LCFA compound, with a recovery of 75-154% in laboratory control standards (compound specific), and takes approximately fifty minutes for GC analysis of 19 LCFAs in a GTW sample.