Paper and pulp
Wastewater / effluent
Holmen Paper, Madrid produces newsprint from wastepaper. In 2001, the mill had to improve their wastewater treatment process before discharge to a municipal sewer.
Holmen chose SCBP treatment technology. The process consisted of two 1250m3 SCBP bioreactors in series, followed by a microflotation unit. Carrier filling degree inside the bioreactors was 40%. Treatment results were excellent and three weeks after the start-up, all guarantee values were achieved.
In 2006, Holmen started a new paper machine, almost tripling production capacity to 470,000t/a. This meant that the capacity of the wastewater treatment plant had to be increased. Two new 1500m3 SCBP bioreactors with 20% carrier filling degree and a new microflotation unit were built. The new process was operated in parallel lines with the older reactors.
Today, the average flow to the treatment plant is approximately 8500m3/d. The average inlet COD and BOD5 concentrations are 2590 and 1180mg/l, respectively. This means that the average volumetric loads over the whole process are 4.0kgCOD/m3/d and 1.8 kgBOD/m3/d. Daily maximum volumetric loads are 6.2kgCOD/m3/d and 2.8kgBOD/m3/d. Outlet average concentrations of COD, BOD5, and SS after the microflotation units are 400, 70 and 25ppm, respectively. Treated water is led to municipal sewer.