The European pulp and paper industry
is committed to maximising the environmental friendliness of its production
practices, as reflected in efforts made at the paper mill of Oudegem Papier
in Belgium. A notable feature of the facility is its sophisticated water
treatment system, which draws on innovative research carried out in the
European Commission funded PAPER
Oudegem Papier is part of the VPK
Packaging Group , one of the leading western European suppliers of
paper-based packaging materials. The paper mill in Dendermonde specialises
in production of cardboard, test liner and fluting based on recycled fibre.
Locally collected recovered paper is processed at the mill to produce
papers for corrugated board, solid board, tubes and cores. The facility
is centrally located in a densely populated area of Flanders, northern
Belgium, which generates an inexhaustible supply of raw material. In 2000,
its three specialised paper machines produced a total output of 320,000
tonnes, consuming more than half of all the recycled paper collected in
the Flanders region.
Water is a key resource
in paper manufacture. To achieve its current production, Oudegem
Papier pumps 1,000,000 m³/year of water from the River Dender.
Although a large volume, this level of consumption is among the
lowest in Europe for such processes. Every effort is made to reuse
as much water as possible, and to keep effluent discharges to a
minimum. To this end, Oudegem Papier has an ultra-modern water purification
installation that is constantly being optimised and refined.
The site was equipped with a modern anaerobic and aerobic effluent
treatment system in 1994, capable of handling up to 150 m³/h
of effluent. However, this had developed problems with calcium carbonate
(CaCO3) precipitation in the water treatment plant, due to a gradual
increase of calcium levels by the restricted effluent volume allowed.
The anaerobic sludge lost activity due to the participation of CaCO3
on the pallets, and the aerobic sludge was tending to accumulate
so much CaCO3 that it settled to form a thick layer of sediment
on the bottom of the aeration tanks.
In addition, VPK planned to increase production to over 450,000
tonnes/year. It therefore decided to invest an additional €
4 million in an extended system for the mill, which would improve
the internal water quality by reducing the COD (chemical oxygen
demand - a measure of pollution) in the circuit from above 10,000
to below 5,000 mg/l in order to avoid calcium precipitation. The
ultimate objective is to reach a quasi-complete closure of the water
cycles, so that no more water needs to be discharged into the river.
The new equipment
employs innovative purification processes developed under the European
Commission FP5 Growth project PAPER KIDNEY (advanced water treatment
technologies for kidney operating of zero effluent water systems
for paper and board production), of which VPK was a consortium member.
The major breakthrough for PAPER KIDNEY was the idea of cleaning
up the internal water loops by an anaerobic thermophilic internal
circulation reactor (ICR) instead of investing in an extension of
the existing water treatment plant.
An initial advantage of this technology is the cultivation of thermo-tolerant
bacteria, which could digest the pollutants under anaerobic conditions
at around 55ºC: the actual temperature of the process water.
Previously, it had been necessary to cool the water before treatment,
resulting in a considerable waste of energy. Another benefit is
the ability to use a vertical design for the reactor tanks, with
a smaller footprint that reduces the risk of calcium precipitation.
And, by cleaning up the internal water system, biogas is produced
that is reused as a reliable and renewable fuel supply with high
energy efficiency for the steam production.
Commissioned in 1999, the system takes 385 m³/h of non-cooled
clarified water and returns it to the mill circuit after purification.
With this improved internal water quality, the previously existing
treatment plant can function well within its capabilities.
Under the Innovative
products, processes and organisation key action, PAPER KIDNEY
is determining the feasibility of minimising paper mills' water
consumption without compromising product quality.
KIDNEY Advanced water treatment technologies for kidney operating
of zero effluent water systems for paper and board production