Evaluation of greenhouse gas emissions from aerobic and anaerobic wastewater treatment plants in Southeast of Italy

Abstract

An evaluation of the operative functioning data of 183 Wastewater Treatment Plants (WWTPs) in Apulia (Southeast of Italy) has been carried out aimed to assess their Green House Gases (GHGs) emissions and the level for which the use of anaerobic sludge treatment should be more convenient in terms of electricity consumption and of GHGs emissions. Out of the 183 studies WWTPs, 140 are practicing aerobic digestion of sludge, while the remaining 43 are practicing anaerobic digestion of sludge. WWTPs in Apulia are serving about 4,81 million PE (Population Equivalent), yielding approximately 600,000-ton equivalent CO2 per annum. The production of GHGs emissions has been estimated by evaluating the contribution of CO2 deriving from: a) electric energy consumption (fossil CO2), b) biogenic CO2, c) N2O and d) CH4 emissions. The present study investigates a number of technical measures for upgrading the existing WWTPs, so to reduce GHGs emissions through the amelioration of CH4 production and capture in the anaerobic step, and through reducing the production of biogenic N2O and CO2 emissions in the aerated basin. The methodology employees artificial intelligence-based control for upgrading the aerobic oxidation of the organic carbon and the nitrification-denitrification steps. As a result, GHGs emissions are expected to be reduced by approximately: 71% for CH4, 57% for N2O, 20% for biogenic CO2 and 15% for fossil derived CO2.