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 kind of waste 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, depend on 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 Na2S, which is very effective at different kind of woods specially the wood contains pollutions.
  • Disadvantage is the odour problem, based on thiols and sulfides. The pulp has also to be bleached more, compared to the suphite process.
  • Process water of this kind of process contains SO2 and the pH is between 8 and 9. BOD and COD are depending on the kind of 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 same compared to the alkaline process. The procedure is more sensitive, against pollution. Branches and bark disturb the chemical process and will not solute as well as the wood. Also resin disturbs the process.
  • Advantages of the “sulphite process” are more process variations and producing conditions without unwanted thiol and sulfide production.

 

 

 

The production of demineralised water for bleaching pulp and supplying boilers and cooling circuits:

  • By coupling ultrafiltration with reverse osmosis
  • By counter-current regeneration (UFD process), for good quality, softened water
  • By ozone to bleach paper pulp and to ensure the absence of any remaining chlorinated compounds (AOX)

The treatment of waste water and sludge:

  • By a physical/chemical finishing process, for the reduction of suspended matter and phosphorus
  • By biological pre-treatment to eliminate carbonaceous pollution
  • By biological process for diluted effluent and high water flow
  • By a methanisation process, for granular sludge and to make use of the energy contained in the sludge
  • By MBR, combining aerobic digestion with separation by ultrafiltration membranes

Furthermore, we offer a full range of services that cover complete operation of your water treatment installations, maintenance, technical assistance and leasing of mobile water treatment units to meet any temporary requirements (emergencies, maintenance, etc.).

  • Guaranteed supply of process water, both in terms of quantity and quality
  • Water savings
  • Production of boiler supply water
  • Ozone treatment to bleach paper pulp
  • The treatment of waste water, effluent and sludge
  • Cost reduction

We have a complete range of water treatment solutions for the production of demineralised water and the treatment of effluent from the paper industry.