The potential impact of an implementation of microalgae-based wastewater treatment on the energy balance of a municipal wastewater treatment plant in Central europe

•Calculation of algae-amendment of an existing WWTP.•Year-round calculation of process efficiency based on algae growth rates in Germany.•Differentiation of algae mediated wastewater treatment by season.•Separate consideration of thermal and electrical energy balance.•Microalgae addition has a large potential in terms of renewable energy. Integration of a photobioreactor for WWT by microalgae is calculated as a future alternative for cost-efficient and environmentally-friendly nutrient removal for municipal WWTPs. High growth rates and higher biogas yields (compared to conventional sewage sludge) of algal biomass can significantly improve WWTP energy balances. This study focuses on temperate climate zones with changing seasons and discusses energy potential of microalgae-enhanced wastewater treatment for an existing WWTP (32,000 PE) in Central Germany. For WWTP-dimensioning and determination of energy-rich biomasses for anaerobic digestion and CHP, actual influent load data was used and calculation was carried out according to valid regulations. Algae growth figures are based on pilot-scale test series from Germany and correspond to the relevant climatic and local process conditions. Computed results show a shift in the energy balance from a current energy demand of 662,173kWh a-1 to an energy production of approx. 1,9MWhel. a-1 and 1 MWhth. a-1.