Performance of wastewater treatment plants in emission of greenhouse gases

The present work has estimated greenhouse gas emissions in aerobic and anaerobic Wastewater Treatment Plants in Southern Italy. Greenhouse gases emissions from each treatment unit were calculated based on emission factors related to Chemical Oxygen Demand removal for biogenic CO₂ and CH₄ assessment and on Nitrogen removal for N₂O. N₂O, biogenic CO_2, and CH₄ emissions vary for aerobic and anaerobic-based WWTPs respectively from 73 kgCO_2eq/PE*y for anaerobic plants to 91 kgCO_2eq/PE*y for aerobic plants. In aerobic and anaerobic digestion systems WWTPs the contributions to CO_2eq total emissions from N₂O, CH₄, biogenic CO₂, and fossil CO₂ are 30 %-33 %, 20 %-29 %, 22 %-25 %, and 26 %-16 %, respectively. N₂O emissions from biological processes were found the most contributing sources of greenhouse gases while in the physical processes higher contribution is indirect carbon dioxide related to energy consumption. Compensatory measures are reported to reduce greenhouse gases emissions.