MEVGAL S.A. is the largest dairy producer in Northern Greece to collect most of the fresh milk produced in the region and neighboring areas from nearly 1000 farms on a daily basis. A wide range of end products is produced: fresh pasteurised milk, high-pasteurised milk, yogurts, cheeses, desserts and rice puddings, jellies and creams and the products are delivered every day to some 26,000 sales points across Greece and to 36 different countries, as well. The plant disposes all the wastewater from the production activity to an on-site wastewater treatment plant with a capacity of 60.000 Population Equivalent. Main challenges to cope with, were the high cost of surplus sludge production and disposal, fat accumulation in different wastewater polishing stages and compromised plant performance. After applying bioaugmentation, surplus sludge production has been significantly decreased, fat accumulation phenomena have been mitigated and all effluent parameters constantly remain within legislative limits.