Sweden's Alfa Laval and Norway's OceanSaver confirmed they have both won type-approval from the US Coast Guard (USCG) for their ballast treatment system.
The approval comes after Norwegian peer Optimarin won the first type approval for a USCG-compliant ballast treatment system earlier this December.
Both companies submitted their application for type approval last September.
Alfa Laval's system uses an ultra-violet light and mechanical filtration, while OceanSaver's system uses electrochlorination and mechanical filtration.