Investigating the Nexus of Energy and Carbon Footprint in a Municipal Wastewater Treatment Plant with Activated Sludge Process (Conventional)

Abstract

In Iran, little attention has been paied to the nexus of energy and carbon footprint in wastewater treatment plants. The main goal of the current research is to investigate this issue in a municipal wastewater treatment plant with a conventional activated sludge (conventional). While studying the quantity and quality of wastewater, direct and indirect emissions were calculated based on the operation of the treatment plant and the amount of electricity consumption using emission coefficients. An average of 6,192,000 m3 of wastewater is treated annually in this treatment plant. The average BOD5 and COD removed are 274.6 and 467.9 mg/L, respectively. On average, 0.3623 ± 0.081 kWh/m3 of energy is consumed for treated wastewater, which is equivalent to 2241.5 MWh per year. As much as 94.6% of energy is consumed by pumps and surface aerators. Considering BOD removed, the direct greenhouse gas emissions are on average 2338.2 tCO2e/year and the indirect emissions due to electricity consumption are 2603 to 4665 tCO2e/year. Old design and lack of up-to-date equipment are factors that increase energy consumption and carbon footprint emission. The low tariff of electricity in the wastewater treatment plant (agricultural tariff) has made the issue of saving energy consumption less of a priority. It is necessary to pay attention to the reduction of electricity consumption, especially in the reactive mode, with the necessary modifications. It seems essential to conduct an energy audit in the existing treatment plants and pay attention to the nexus between energy and carbon footprint.

Keywords

• energy footprint
• greenhouse gases
• wastewater
• global warming