Mission
To comply with environmental standards at all times, at
competitive costs.
Description
The effluent treatment facilities at Papier Masson Ltée
were put into operation in June 1995. They are used to
sanitize:
- the water discharged from the pulping and papermaking
processes
- the leadrate from the mill’s landfill
site
PRIMARY TREATMENT
The primary treatment of wastewater has three steps:
- A mechanical Bar Screen removes any debris that could
block or damage the piping.
- A primary clarifier purifies
the wastewater of solid materials that form sediment
(suspended solids or SS), such as wood
pulp, sand and bits of wood. These solids are salvaged
as sludge and are referred to as primary sludge.
- In summer,
a cooling tower lowers the temperature of the water to
between 30°C and 37°C so it can
be treated further.
SECONDARY TREATMENT
- The wastewater (effluent) then goes into two aeration
basins, the centrepiece of the activated-sludge secondary
treatment. These basins make it possible to remove 98%
of the organic wood material and all toxicity from the
wastewater.
These basins are equipped with an aeration system that
supplies the oxygen needed for the biological breakdown
of dissolved organic matter and for maintaining optimal
mixing conditions in the aeration basins.
In these basins, micro-organisms feed on the dissolved
organic matter and reproduce under optimal conditions.
These micro-organisms naturally exist in water and it
is their activity that cleanses the wastewater.
- From
the aeration basins, the effluent flows into two secondary
clarifiers whose purpose is to capture and retain the
micro-organisms
in the effluent. The sludge salvaged at this point
is called biological sludge.
These micro-organisms form a sediment at the bottom
of the secondary clarifiersand are returned to the
aeration
basins so as to maintain a sufficient level of micro-organisms
for the water treatment.
Excess biological sludge is taken and mixed with the
primary sludge. This mix, called biosolids, is dehydrated
using
a belt press. Once dried, the biosolids are converted
into compost or distributed to farmers for use as organic
fertilizer.
After going through the secondary treatment, the cleaned
water is returned into the Lièvre River, in compliance
with the standards prescribed by the federal and provincial
regulations governing pulp and paper mills.
Diagram
- Waste Water treatment
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