Oily waste: challenges, issues and remedies

In Riviera’s webinar, Oily waste: challenges, issues and remedies held on 29 October 2025, H2O LLC technical specialist Matthew Adams and Marinfloc sales and production manager Fredrik Andersson warned that outdated rules, weak enforcement and poor training continued to undermine oily water separator (OWS) performance.

Mr Adams framed the issue in terms of seamanship and regulation and reminded delegates that nearly all modern OWS units were built to IMO MEPC 107(49), designed to deliver effluent at or below 15 ppm oil content.

“The OWS or the oily water separator serves as the first line of defence in preventing accidental oil discharges into the sea,” he said, but added this depended on crews understanding discharge limits, special areas and oil record book requirements, and on vessels keeping oil content monitors (OCMs) correctly calibrated.

He identified three recurring causes of accidental discharge: weak understanding of IMO discharge rules; inadequate maintenance and training; and neglected OCM calibration.

Mr Adams stressed that inspectors increasingly expected crews to demonstrate competence of the equipment itself.

Regular operation, basic housekeeping and scheduled maintenance, supported by genuine calibration certificates from authorised dealers were presented as minimum expectations rather than best practice.

Mr Andersson focused on enforcement gaps and fuel changes and noted that satellite monitoring had detected tens of thousands of oil slicks over the past quarter century, yet only a tiny fraction had been investigated.

“When no one checks, compliance becomes optional,” he said, warning this encouraged the continued use of bypasses and outdated systems.

At the same time, he noted, bilge water composition had been transformed by low-sulphur fuels, methanol, LNG, biodiesel, modern detergents and advanced lubricants, while type-approval tests still relied on 1990s fuel samples.

According to Mr Andersson, static separator designs certified under MEPC 107(49) struggled with this dynamic bilge water, and the absence of updated test protocols removed incentives to develop and certify improved designs.

He argued that flocculation offered a practical retrofit and newbuild option, allowing treatment systems to be tuned to changing bilge chemistry. “The solutions for pollution exist,” he said. “There are no excuses.”