Tertiary treatment of Effluent

Iggesund Paperboard is a member of the Holmen Group and Europe´s leading manufacturer of high quality virgin fiber paperboard for use in the packaging and graphics sectors. The Iggesund mill in Sweden is one of the most advanced, fully integrated pulp and paperboard mills in the world. The product family is called Invercote and is used for the highest quality graphics products and packaging. Invercote is a multilayered Solid Bleached Board and is manufactured from fiber of known and traceable origin and produced at a site where pulp production is integrated with the paperboard mill. CD covers and exclusive packaging for perfumes, chocolate and cognac are examples of applications. Production capacity is 330,000 tons/year. Holmen is a Swedish forest industry group that manufactures printing paper, paperboard and sawn timber and runs forestry and energy production operations.

The Iggesund Mill received early 2008 more strict requirements on the effluent quality from the Swedish Environmental Protection agency when it comes to COD, Suspended Solids and Nitrogen. Purac was selected as the turn-key contractor for the investment, which was decided in June 2009. The plant was ready for start-up late summer 2009 and was taken over by Iggesund Paperboard beginning of 2010. Process design is based on Chemical treatment to reduce inert COD and Dissolved Air Flotation. Effluent water from primary and secondary treatment, comprising of sedimentation and biological treatment in aerated lagoons, flows via a surge tower to a by-pass tank. In the mixing tank the chemical coagulants are added, in order to maximize COD-reduction, to the water which is then led to a distribution tank. In the distribution tank the water is equally divided in two lines by weirs into respective line.

The chemical sludge is separated from the clean water by Dissolved Air Flotation, DAF. The sludge which has a TSS-content of app. 2 % is dewatered in two decanter centrifuges. TSS-content after the centrifuges is app. 20 %. After treatment in the two DAF-lines the water is collected in a common outlet surge tower before it flows to the recipient, i.e. Gulf of Bothnia.


Technical data

Treatment results
COD average: < 120 mg/l
COD guarantee: ≤ 120 mg/l
TSS average: < 15 mg/l
TSS guarantee: ≤ 25 mg/l
P-tot average: < 0.1 mg/l
P-tot guarantee: ≤ 0.25 mg/l
N-tot average: < 1.0 mg/l
N-tot guarantee: ≤ 2.0 mg/l