The industrial WWTP of Komotini is processing wastewater from local industries (dairy, brewery, paper industries etc.) with an average influent of 2000-2500 m3/d and a fluctuating COD from 1600 to 3600 mg/L. The TSS in the influent can also be high, reaching up to 2500 mg/L. Due to the unstable parameters and the low dissolved oxygen levels in the aeration tanks, bio-augmentation was a key solution for the proper function of the plant. After the implementation, effluent COD dropped under 50 mg/L and TSS under 10 mg/L. Also, SVI has reduced way below the common values for activated sludge systems (≈150 mL/g) reaching 95 mL/g. Thus, the plant showed stability in fluctuating flowrates and organic loads. Moreover, dewatered sludge production reduced up to 70% of the initial sludge production prior the bio-augmentation. The total operational cost has dropped significantly due to major cuts in sludge disposal, less usage of thickening polyelectrolytes, less electricity consumption from blowers and decanter.