Greenhouse gas production: A comparison between aerobic and anaerobic wastewater treatment technology

Anaerobic wastewater treatment offers improved energy conservation with potential reduction in greenhouse gas emissions. Pitfalls exist in that the methane produced in anaerobic treatment can offset any reductions in carbon dioxide emissions, if it is released to the environment. This paper analyzes greenhouse gas emissions from both aerobic and anaerobic treatment systems, including sludge digestion and the losses of dissolved methane in digested biosolids and process effluents. There exists cross over points, ranging from 300 to 700 mg/L influent wastewater BOD _u, which are functions of the efficiency of the aerobic treatment system. Anaerobic treatment becomes favorable when treating influents higher in concentrations than the cross over values. A technology to recover dissolved methane would make anaerobic treatment favorable at nearly all influent strengths.