A wastewater treatment plant at SCA’s Munksund paper mill in Sweden went online in June. The mill produces paper mass and kraftliner, a starting material for packaging. SCA says that the new treatment plant will reduce oxygen-consuming matter in wastewater by more than 70%.
Construction on the MultiBio-based plant began at the beginning of 2008 at a cost of $31 million. The new treatment plant consists of three basins – the old design consisted of only one sedimentation basin.
Up to 25,000 cubic meters of process water per day is pumped into the treatment plant. In a first sedimentation basin, which is 45 meters in diameter, fibres and bark sink to the bottom and are transported to dewatering and combustion.
After its cooled to approximately 37 degrees Celsius, the water is pumped to the bio-basin, which is 35 meters in diameter, where the biological treatment process takes place. To ensure that the microorganisms responsible for carrying out the treatment process are healthy and capable of doing their job, air, nitrogen and phosphorus are added to the basin.
In the post-sedimentation basin, the biosludge sinks to the bottom and is pumped out and dewatered. It totals about three to four tons per day, which is used to fuel the plant’s boiler. The water, cleaned of oxygen-consuming matter, is then released into the Yttre fjärden bay near the mill.
The company has set a goal to reduce the proportion of organic matter in wastewater by 30% and cut water use by 15%.
The company recently reported that its factory in Box Hill, Australia cut fresh water use 70% per tonne of paper over the last 10 years.