Minimizing greenhouse gases emissions and energy consumption from wastewater treatment plants via rational design and engineering strategies: A case study in Mashhad, Iran

Abstract

Wastewater treatment plants (WWTPs) play direct and indirect roles in the emission of greenhouse gases (GHG) produced by biological processes and energy consumption, respectively. Nowadays, reducing GHG emission and the energy consumption of WWTPs are of interest. In this study, at first, the GHG emissions and energy consumption of the Mashhad WWTP (MLE and aerobic digestion process) were compared with energy self-sufficient WWTPs. In the next stage, four scenarios were developed to reduce GHG emissions and energy consumption. According to the results, energy consumption and GHG emissions in this WWTP is outside of the acceptable value. By changing aerobic digestion to anaerobic digestion, the energy consumption will decreases from 1 kWh/m3 to 0.58 kWh/m3, and the total amount of CO2 equivalent (CO2e-T) increases from 0.64 kg CO2e/m3 to 1.65 kg CO2e/m3. In order to reduce energy consumption and GHG emissions, anaerobic digester and CHP must be used together. This process leads to reduced energy consumption and GHG emissions by about 70% and 53% , respectively. The lowest (highest) GHG emissions will occur in MLE with anaerobic digester and CHP (without CHP). Based on this study, GHG emissions and energy consumption can be controlled by selecting a correct process for WWTPs.