PULP & PAPER INDUSTRY
WASTE GENERATION POINTS
CHARACTERISTICS OF W/W
CHARACTERISTICS OF TREATED W/W
Reff :- S. C. Bhatia
• Raw Materials-Conventional raw material
are rice and wheat, straw, bagasse, jute,
cotton rags, grasses, gunny, hessian, etc.
• Chemical Requirements- About 5-12% of
NaOH is required per tonne of raw material.
Lime is used as supplement to NaOH.
Chlorine and calcium hypochlorite are
bleaching chemicals. Sizing chemicals and dyes
are also used.
Raw materials used in paper industry.
• Water Requirements- P and P industry’s
existence lies on water supply. Constant
water supply is required in all processes.
Agricultural residue based industries require
200-350 cubic meter per tonne of paper
made, however units using waste paper
require 100-150 cubic meter per tonne of
The bark is removed from in-coming logs, and these
are then chipped. Sometimes, the wood arrives at the
plant already chipped, meaning that this step is
The wood chips are heated in a solution of NaOH and
Na2S in a pressure cooker, during which time a lot of
the lignin is removed from the wood. The pressure is
then released suddenly, causing the chips to fly apart
The pulp is washed with water to wash out the
cooking chemicals and lignin from the fiber so that
they will not interfere with later process steps. A good
removal of chemicals
is necessary for several reasons:* The dissolved chemicals interfere with the
downstream processing of the pulp.
* The chemicals are expensive to replace.
Apart from fibres, the cooked pulp also contains partially
uncooked fibre bundles and knots. Modern cooking processes
have good control over the delignification and produce less
"rejects". Knots and shives are removed by passing the pulp
over pulp screens equipped with fine holes or slots.
This is done in two stages. Firstly the pulp is treated with
NaOH in the presence of O2. The NaOH removes hydrogen
ions from the lignin and then the O2 breaks down the polymer.
Then, the pulp is treated with ClO2 then a mixture of
NaOH, O2 and peroxide and finally with ClO2 again to remove
19/03/2012 remaining lignin.
The fibers are mechanically treated to make them bond
better to each other, chemicals added to provide special
properties such as color or water resistance, and then the
water is squeezed out and the pulp is rolled smooth and
Various ancillary processes result in the recovery of
CaO, NaOH and Na2S, the major chemicals used in the
process. Various utilities ensure that such conditions as
sufficient reaction times and adequate mixing are met.
• Sources of waste wateri) Black liquor* from cooking section.
ii) Pulp wash water from pouchers.
iii) Bleaching section.
iv) Paper machine.
* Black liquor is the spent cooking liquor from the kraft
process when digesting pulpwood into paper
pulp removing lignin, hemicelluloses and other
extractives from the wood to free the cellulose fibers.
• Treatment of Pulp and Paper Mill Wastewater by
Polyacrylamide (PAM) in Polymer Induced
• Cationic polyacrlyamide Organopol 5415 with very
high molecular weight and low charge density is
found to give the highest flocculation efficiency in
the treatment of the paper mill wastewater.
• It can achieve 95% of turbidity reduction, 98% of
TSS removal, 93% of COD reduction and sludge
volume index (SVI) of 14 ml g−1 at the optimum
dosage of 5 mg l−1.
• Based on the cost evaluation, the use of the
polyacrylamides is economically feasible to treat
the pulp and paper mill wastewaters.
• Result suggests that single-polymer system can
be used alone in the coagulation–flocculation
process due to the efficiency of the
• Sedimentation of the sludge by gravity
thickening with settling time of 30 min is
possible based on the settling characteristics of
the sludge produced by Organopol 5415 that
can achieve 91% water recovery and 99% TSS
removal after 30 min settling.
• Enzymes offer a simple solution for addressing lignin
in effluent. Enzymes oxidize lignin and phenolic
compounds to enable and promote separation from
effluents and increase capacity.
• Moreover, enzymes can modify the residual lignin in
unbleached pulp to improve the physical and
mechanical properties of paper and board and the
runability of the paper machine.
• Enzymes are a biodegradable alternative to
petroleum-based and/or expensive strengthening
agents and effluent management additives.
• The application of enzymes directly leads to better
paper quality: While the brightness level goes up, the
residual dirt level goes down. Saving on bleaching
chemicals also means milder process conditions and
an accentuated sustainable profile.(deinking)
• The enzymatic treatment can reduce the kappa
number and increase pulp brightness when the same
bleaching chemical charges are applied. It also allows
savings in bleaching chemicals, while the final
brightness of the paper is increased.(bleaching)