SAR's biological water treatment plant at Mongstad is the largest treatment plant for polluted water in Norway, with a permit for annual treatment capacity and discharges in accordance with strict requirements of 240,000 mᶟ.
The unique thing about the plant is that it is robust, and has the ability to treat a wide range and complex compositions of contaminated water.
The water is mostly produced from offshore industries and includes, among other things, oil-contaminated water, ballast water, washing water, engine room slop and water contaminated with heavy metals.
Best Available Technology (BAT) is implemented to ensure optimal conditions for the process, as well as environmental protection.
Pretreatment of contaminated wastewater is done by chemical processing in a DAF plant ("Disolved Air Flotation"). Heavy metals, solids and hydrocarbons are removed in this process.
Sludge phase from DAF treatment is further treated in decanters to reduce the water content, where the water returns to the biological treatment.
Biological treatment in an activated sludge system ("Active Sludge" Bioreactor), removes dissolved organic compounds, nitrogen and phosphorus from the pretreated water from DAF.
Electric blowers supply air to "diffusers" into the bioreactor (Oxygen to the bacterial culture), sludge settles in a clarification tank, and is recycled back to the active sludge system.
Excess sludge is removed from the biologically active sludge and handled in a dewatering process.
Treated water from the biological treatment is then filtered in a Dynasand filter, which removes excess particles, before the water is finally controlled for discharge to sea.