Co-digestion of onion juice and wastewater sludge using an anaerobic mixed biofilm reactor

• Published in: Bioresource technology 2008-02, Vol.99 (3), p.631-637
• Main Authors: Romano, Rowena T., Zhang, Ruihong
• Format: Article
• Language: English
• Subjects: Aerobiosis; Alkalinity; Allium cepa; Anaerobic digestion; Anaerobiosis; Applied sciences; Bacteria, Anaerobic - physiology; Biodegradation, Environmental; Biofilms; Biological and medical sciences; Biological treatment of sewage sludges and wastes; Bioreactors; Biotechnology; Carbon to nitrogen ratio; Co-digestion; Environment and pollution; Exact sciences and technology; Extracted onion juice; Food; Food industries; Fruit and vegetable waste; Fundamental and applied biological sciences. Psychology; Industrial applications and implications. Economical aspects; Methane; Onions; Onions - metabolism; Pollution; Use and upgrading of agricultural and food by-products. Biotechnology; Waste Disposal, Fluid; Wastes
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2006.12.043

The co-digestion of onion juice and aerobic wastewater sludge produced from an onion processor using an anaerobic mixed biofilm reactor (AMBR) was investigated for biogas energy production potential and waste treatment. Two experiments were conducted to study the performance of an AMBR at different organic loading rates (OLRs) using different mixtures of onion juice and aerobic sludge. In the first experiment, the OLR was increased from 1.24 to 4.37 gVS/L/d by increasing the amount of onion juice in the feed mixture while maintaining a constant amount of aerobic sludge. When the OLR reached 4.37 gVS/L/d, the AMBR failed as indicated by decreased biogas production and pH. Increase of carbon to nitrogen ratio (C/N) from 13.7 to 20.3 and lack of proper alkalinity were suspected to be the causes for the failure. In the second experiment, the C/N of the feed mixture was maintained at about 15 while the OLR was increased from 1.40 to 3.60 gVS/L/d. The digester showed stable performance. The average biogas and methane yields of the two experiments were 0.62 ± 0.05 L/gVS and 0.37 ± 0.08 L/gVS, respectively. It was concluded that the C/N of about 15 was recommended for treating the mixture of onion juice and aerobic sludge.