Some 30 000 tonnes (about 22 % dry matter) of sludge containing valuable nutrients and organic matter is generated during the treatment of waste water in the Oulu region. The sludge that results from waste water treatment is industrially processed on the site of the treatment plant. The final result of the treatment is a soil enrichment material that can be used as fertiliser or further processed into a soil product, for example. In addition, energy can be recovered from sludge in the form of biogas.
The reduction in phosphorus reserves that can be recovered easily and cost-effectively has raised concerns internationally about there being sufficient availability of phosphorus. When soil enrichment material and soils derived from treatment plants are used, nutrients are returned to the soil and the natural resource of phosphorous, which is in decline, enters into an efficient cycle.
In the Oulu region, a determined effort has been made to exploit sewage sludge and promote it in cooperation between the municipality and local businesses, with a view to bringing about new applications and a processing chain that meets today's stricter requirements.
