The industrial WWTP of Patras, which is receiving wastewater from local industries has an average influent flowrate of 3,500 – 4,000 m3/d. The plant was producing excess sludge that was ranging from 135 to 266 tons per month which needed to be reduced due to the high expenses for decanter operation and sludge handling. With the aid of bioaugmentation, the produced sludge was reduced by 80%. Further electric power and financial savings arose from the minimized dewatering presses running time, less aeration, less polyelectrolytes and chemicals usage, while also from the reduced cleaning that was necessary in the pumping station due to fats elimination. Interesting fact is that the WWTP’s microbial community was strengthened and was able to overcome situations where toxic oil-based wastewater entered the plant.