pulp and paper industry water treatment
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Pulp and paper industry water treatment
This two kinds of industries are normally separated. The pulp (raw
material for paper industry) and the paper industry, produce different kindofwaste water. There is also a third related industry, the paper recycling
industry, which has a similar kind of waste water. In the following text the
three branches of industry are separated.
Production process, pulp industry
The composition of pollutants in waste water of paper industries, dependon the kind of raw material which is used. For paper production wood,
bagasse (outer stalk sugar cane), hemp, straw, etc. are used. Five basic
procedures are used to produce pulp in an industrial way. The conduction
of case can be with or without a bleaching process.
If a bleaching process is also step of production, the Lignin will be
destroyed. The effect is a whiter paper. The color depends also on the
different kinds of wood or other raw materials which are used for the
production. This step have the disadvantage to load the environment
more, because of the use of chemicals like chlorine or chlorine dioxide
(which are restricted, because of the process).
Chemical Processes
To produce pulp for fine and print paper, two chemical procedures are used.
The Kaft process is an alkaline process. The lignin is cracked by NaOH or N
woods specially the wood contains pollutions.
Disadvantage is the odour problem, based on thiols and sulfides. The pulp hsuphite process.
Process water of this kind of process contains SO2 and the pH is between 8
wood. Normally the BOD5 is between 1- 2 g/L, and the COD is 4- 7 g/L.
The sulphite process is a procedure based on acids. The effect is not the s
procedure is more sensitive, against pollution. Branches and bark disturb thwood. Also resin disturbs the process.
Advantages of the sulphite process are more process variations and produ
production.
Semichemical processes
The NSSC (Neutral Sulphite Semichemical) is most used. The yield of th
The TMP (Thermo-Mechanical Process) is generally used for newsprint p
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The new CTMP (Chemi-Thermo-Mechanical P rocess) is high efficient (a
high than in other described processes. But it needs more energy to produc
In modern pulp plants, this kind of waste water has to treated generally:
bleaching solutions
washing and emptying
evaporation condensates
The amount of water which has to be treated is very high
approx. 30m3/t pulp with mechanical processes and up to 150 m
3/t p
up to 10- 30% of fibres, fibrils and CaCO3
BOD5 and COD load vary between different kind of wood (BOD5- 100-
Waste water is treated by anaerobic waste water treatment vaporizing, incin
Paper waste water
Paper is produced from new or recycled pulp. Depending on the quality of
the process of paper producing, kaolin, CaCO3, talc and/or TiO2 are added to
Also chemicals like organic fillers (starch, latex), colors, aluminum sulfate, e
making the process simpler.
Paper can be decolored, which can be done with two different processes. Wa
washing with a low amount of water plus additions like sodium silicates, sodi
Paper recycling
Pulp can be also made of recycled paper. But because of the color on
written, old papers the pulp has to be bleached. The following procedures
can be used.
Depending of the agents to bleach the pulp, waste water has to be
treated. Bleaching with peroxides, oxygen and ozone is not as efficient as
using chlorine or chlorine dioxide, but the water has generally a very low
or no amount of to treatment chemicals. By using chloride or chloride
dioxide, the water contains these agents which increase the AOX. On the
other hand, chloride bleaching is the most efficient.
The waste water of paper recycling contains also particles which have tobe filtrated. Rests of plastics, metal parts (paper clips, etc.) other waste
have to be removed.
Find information about Water recycling i
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