1. Introduction
Municipal wastewaters are typically treated through conventional activated sludge (CAS) processes which are generally energy intensive and focus on the removal of organics and nutrients. The specific energy consumption of CAS plants without sludge incineration is in the range of 0.3–0.6 kWh/m3[1]. About half of the energy is used for aeration, which is necessary for microbial degradation of organic C and nitrogen removal in wastewater. Thus, approximately 45% of the total biodegradable chemical oxygen demand (COD) in wastewater is lost through oxidation to carbon dioxide