The combination of green electricity and biologically treated wastewater for hydrogen production represents an innovative approach to integrating wastewater treatment and renewable energy. Through additional treatment steps, biologically treated wastewater can be further processed into ultra-pure water (UPW) for use in electrolyzers. The oxygen generated during electrolysis also opens up perspectives for its application in aerobic treatment processes. The specific boundary conditions and the required investment for direct injection into the activated sludge tank are currently still under further investigation.