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

The integration of a photobioreactor for wastewater treatment by microalgae is proposed as a future alternative for cost-efficient and environmentally friendly nitrogen and phosphorous removal in municipal WWTPs. The high growth rates and higher biogas yields (compared to conventional sewage sludge) of algal biomass can significantly improve the energy balance of a WWTP. This is currently being considered especially for countries in subtropical climate zones like Spain or Israel. As this study focuses on temperate climate zones with changing seasons, lower temperature and less sunlight, the energy potential of an implemented wastewater treatment by microalgae is discussed for an existing WWTP (32,000 population equivalents) in Central Germany. For the dimensioning of the plant and the determination of the energy-rich biomasses, the observed influent loads of the plant were used and the calculation was carried out according to valid regulations. The observation of algae growth figures is based on pilot-scale test series from Germany and thus corresponds to the selected climatic conditions. Initial results show a shift in the energy balance from a current energy demand of 662,173 kWh a-1 to energy production of approx. 1.9 MWhel. a-1.