Abstract

The outcome of Kyoto protocol and other National and International agreements influence the design and operation of wastewater treatment facilities by restricting their greenhouse gas (GHG) emissions. Wastewater treatment plants (WWTPs) are recognized as one of the larger minor sources of GHG emissions that produce CO 2 , CH 4 , and N 2 O during the treatment processes. The overall on-site and off-site greenhouse gas (GHG) emissions by WWTPs of food processing industry were estimated by using an elaborate mathematical model. Three different types of treatment systems were examined in this study which included aerobic, anaerobic, and hybrid anaerobic/aerobic processes. The overall on-site emissions were 1952, 1992, and 2435 kg CO 2 e/d while the off-site emissions were 1313, 4631, and 5205 kg CO 2 e/d for the aerobic, anaerobic and hybrid treatment systems respectively. The on-site biological processes made the highest contribution to GHG emissions in the aerobic treatment system while the highest emissions in anaerobic and hybrid treatment systems were obtained by off-site GHG emissions due to on-site material usage. Biogas recovery and reuse as fuel were shown to cover the total energy needs of the treatment plants for aeration, heating and electricity for all three types of operations, and considerably reduced GHG emissions by 512, 673, and 988 kg CO 2 e/d from a total of 3265, 6623, and 7640 kg CO 2 e/d for aerobic, anaerobic, and hybrid treatment systems, respectively. In the end, recommendations were given on feasible approaches to reduce GHG emissions from WWTPs.