The industrial WWTP of Komotini is processing wastewater from local industries (dairy, brewery, paper industries etc.). Due to the unstable influent characteristics and the low dissolved oxygen levels in the aeration tanks, bio-augmentation was a key solution for the stable plant operation. After the implementation, effluent COD dropped under 50 mg/L and TSS under 10 mg/L in the effluent. Also, SVI has reduced far below the typical values for activated sludge systems (≈150 mL/g) reaching 95 mL/g, in average. Moreover, dewatered sludge production reduced up to 70% compared to previous conventional operational conditions. The total operational cost has been significantly reduced, due to major cuts in sludge disposal, less usage of thickening polyelectrolytes and less electricity consumption for blowers and decanter operation.