Environmental Declaration 2011 - Sappi

thermally in the heating power plant. This
plant consists chiefly of a 1,300 m³ steel
tank. Via an inflow distribution system at the
bottom, the wastewater flows through the
tank, from bottom to top. The biogas, the
pellet sludge with the microorganisms and
water are separated from each other in the
top area of the tank. The biogas produced is
utilised thermally in the heating plant,
reducing the use of fossil fuels.
Multi-stage waste water
treatment
During the following treatment stages
(activated oxygen and secondary purification),
further contaminants are further
degraded and the biomass is retained in the
system.
Following a preliminary purification, wastewater
from paper manufacture is purified in
an aerobic biological fixed film filter. Waste
water from the coating machine containing
calcium carbonate is treated in an ultrafiltration
module integrated into the process.
This recovered carbonate is used again in
production. Wastewater from the power
plant area is purified in a chemical­physical
treatment plant.
14 Environmental Declaration 2011
100
75
50
25
0
All treated waste water is carefully monitored
with a sophisticated online measuring
system, additional laboratory tests and is
also subject to measurements taken by the
public authorities before being run back into
the Main.
Waste water purification levels 1976 – 2011 (%)
COD purification
BOD5 purification t/a