Anaerobic digestion of catering wastes: effect of micronutrients and retention time

• Published in: Water science and technology 2008-01, Vol.57 (5), p.687-692
• Main Authors: Climenhaga, M.A, Banks, C.J
• Format: Article
• Language: English
• Subjects: Ammonia; Ammonia - metabolism; anaerobic digesters; Anaerobic digestion; Anaerobic processes; Anaerobic treatment; Anaerobiosis; biodegradability; Bioreactors; cafeterias; catering; Digestion; duration; equipment performance; Fatty acids; Fatty Acids - chemistry; Fatty Acids - metabolism; Fatty Acids, Volatile - metabolism; Food; Food sources; food wastes; fried foods; fruits (food); Humans; lipids; Load distribution; Loading rate; meat; Methane - metabolism; methanogens; Micronutrients; Micronutrients - metabolism; nutrients; Organic loading; Reactors; Refuse Disposal - methods; Retention; Retention time; starch; sugars; Time Factors; Trace elements; Vegetables; volatile fatty acids
• ISSN: 0273-1223; 1996-9732
• DOI: 10.2166/wst.2008.092

Source-separated foodwastes collected from a campus catering facility were processed in bench-scale single-stage anaerobic digesters. The feedstock contained a varied mix of fruits, vegetables, meats and fried foods. A constant organic loading rate (OLR) was maintained with differing hydraulic retention times (HRT). Regular addition of trace elements or prolonged retention time allowed stable digestion at high total volatile fatty acid (TVFA) levels. Reactors on HRT of 25, 50, and 100 days with no micronutrient supplementation exhibited methanogenic failure after approximately 40, 100 and 90 days respectively, while duplicate reactors with micronutrient supplementation maintained stable digestion. An extended HRT of 180 days has so far allowed continued digestion (for reactors with and without micronutrient supplementation) at levels of ammonia nitrogen exceeding 5.7 g l(-1) and volatile fatty acid levels exceeding 15 g l(-1), usually considered inhibitory or toxic.