The company, which operates four plants in the UK and Ireland, appeared at Aberdeen sheriff court on 26 June to admit to breaching discharge limits, contrary to section 24 of the Sewerage (Scotland) Act 1968.
The court heard UFI had a history of breaching its effluent agreement with high-strength discharges from its works at East Tullos industrial estate in Aberdeen.
UFI admitted to discharging effluent to the sewer with a biochemical oxygen demand (BOD) up to 19 times greater than allowed by its consent in August 2006.
Scottish Water said the company’s agreement stipulated a maximum of 95 kilograms of BOD could be released to the sewer per day but on one occasion the company had discharged 1,772kg - almost 1.8 tonnes.
The recurring failures to meet effluent limits led the water company to report the breach to the Procurator Fiscal’s office, which brings public prosecutions in Scotland.
Scottish Water’s trade effluent quality manager George Ellen said: "This is the biggest fine that has been handed out in Scotland for such an offence… We hope this case serves as a warning to others to be vigilant about how and what they discharge into their drains because illegal discharges have a harmful effect on sewage infrastructure and the environment."