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. 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 sugarcane), hemp, straw, etc. are used. Five basic procedures are used to produce pulp in an industrial way. The color depends also on the different kinds of wood or other raw materials which are used for the production.
Paper is produced from “new” or recycled pulp. Depending on the quality of pulp, it’s used for different sorts of paper. During the process of paper producing, kaolin, CaCO3, talc and/or TiO2 are added to the pulp, to give the paper whiter color.
Also chemicals like organic fillers (starch, latex), colors, aluminum sulfate, etc. are used to make paper of different properties or making the process simpler.
Paper can be decolored, which can be done with two different processes:
- Washing the pulp with a high amount of water, or
- Washing with a low amount of water plus additions like sodium silicates, sodium carbonate, fatty acids or non ion detergents.
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 for white water recycling: 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 to be filtrated. Rests of plastics, metal parts (paper clips, etc.) other waste have to be removed.