2. Introduction
• The manufacture of pulp and paper is a
resource-intensive industry that consumes
large amounts of energy, water, and trees.
• It is one of the oldest and one of the• It is one of the oldest and one of the
largest industry in our country.
• Waste water contains very high COD and
colour.
3. • Presence of lignin in the waste is very
high which is not easily biodegradable.
• Because of this COD/ BOD ratio is very
highhigh
• Pulp mill causes more pollution than
paper mills.
4. Manufacturing process
1. Pulp Making
• Chipped cellulose materials are digested
with different chemicals in one tank under
high temp and pressure.
• The process thus loosens the cellulose• The process thus loosens the cellulose
fibers and dissolves the lignin, resin in
the raw material.
• Chemicals used are- sodium sulphate,
sodium hydroxide and sodium sulphide
5. • Spent black liquor is produced from
digestion process.
• This black liquor is very rich in
chemicals therefore it is separated and
treated for recovery of chemicals.
• Cellulosic fibers are washed and
dewatered in ‘decker’ screen.
6. • Washed cellulosic fibers are sent for
bleaching in three stages where
chlorine, caustic and hypochlorite are
used in successive stages.used in successive stages.
• The bleached pulp is sent for paper
mill
7. 2. Paper mill
• In paper mill pulp is mixed with
Alum, talc and dyes in a tank known
as ‘beater’
• After beating pulp is refined in a• After beating pulp is refined in a
machine known as ‘jordan’.
• Refined paper is then diluted for
consistency and passed through
screen to remove lumps and knots
8. • The pulp is then passed through belt
of fine screens to a series of rolls,
where the product paper is produced.
• The drained water is called as white• The drained water is called as white
water
9.
10. Characteristics of combined effluent
Item Small mill Large mill
capacity 20 tonnes of
paper/day
2000 tonnes of
paper/day
Flow per day 330 m3/tonne 222 m3/tonne
Colour 7800 units
pH 8.2-8.5 8.5-9.5
TS mg/l --- 4410
SS mg/lit 900-2000 3300
