Wastewater treatment process impact on energy savings and greenhouse gas emissions

Abstract

The objective of this research was to assess the energy consumption of wastewater treatment plants (WWTPs), to apply a mathematical model to evaluate their carbon footprint, and to propose energy saving strategies that can be implemented to reduce both energy consumption and greenhouse gas (GHG) emissions in Greece. The survey was focused on 10 WWTPs in Greece with a treatment capacity ranging from 10,000 to 4,000,000 population equivalents (PE). Based on the results, annual specific energy consumption ranged from 15 to 86 kWh/PE. The highest energy consumer in all the WWTPs was aeration, accounting for 40-75% of total energy requirements. The annual GHG emissions varied significantly according to the treatment schemes employed and ranged between 61 and 161 kgCO₂e/PE. The highest values of CO₂emissions were obtained in extended aeration systems and the lowest in conventional activated sludge systems. Key strategies that the wastewater industry could adopt to mitigate GHG emissions are identified and discussed. A case study is presented to demonstrate potential strategies for energy savings and GHG emission reduction. Given the results, it is postulated that the reduction of dissolved oxygen (DO) set points and sludge retention time can provide significant energy savings and decrease GHG emissions.

Aeration Process in Bioreactors as the Main Energy Consumer in a Wastewater Treatment Plant. Review of Solutions and Methods of Process Optimization

“…It focuses on decreasing the operating costs using advanced systems of control, and improving the energy recovery, thus increasing the economic benefit [80][81][82]; • Carbon footprint analysis (CFA)-CFA is employed for measuring the total amount of greenhouse gases produced during the operation of wastewater treatment plant. The carbon footprint in WWTPs can be mitigated by decreasing the energy consumption through on-site energy recovery and improving the efficiency of aeration [83][84][85][86][87][88]; • Life cycle assessment (LCA)-LCA constitutes a standardized procedure which is employed for examining the environmental aspects characterizing wastewater treatment plants. This approach was adopted in a few studies in order to investigate the energy-related issues, including the production of biogas as well as AD [89][90][91]; • Data envelopment analysis (DEA)-DEA is commonly used to evaluate the eco-efficiency, frequently when the available data is limited.…”

Considerations for reducing food system energy demand while scaling up urban agriculture

“…It has been estimated that approximately 2% of the total US electricity use is for municipal wastewater treatment (Electric Power Research Institute 2002). The aeration step of treatment, which promotes biodegradation of pollutants, accounts for approximately 50% of this energy use (Curtis 2010, Mamais et al 2015. This approach also results in the release of GHG emissions to the atmosphere; in 2000, US wastewater treatment resulted in ∼33.3 Mt CO 2 e from energy use and sludge degradation (Center for Sustainable Systems 2014).…”

Operational Improvement of Main Pumps for Energy-Saving in Wastewater Treatment Plants

“…Regarding operational improvements, many researchers have studied the optimization of air flow rate to reactors [9][10][11][12]. On average, in Japan, 14% of the energy in WWTPs was consumed by main pumps, while 49% and 28% was consumed for the wastewater treatment process and the sludge treatment process, respectively (formulated from Sewerage Works Statistics in Japan, 2012).…”