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Mechanical pulping

The type of virgin pulp most often used in the production of newsprint and high- circulation magazine papers is obtained by mechanically separating the fibers in wood.Though this is another mainly mechanical process, the amount of energy expended per unit mass of generated pulp is high, and that may explain why there is significant release of soluble and particulate materials into the water phase (Stephenson and Duff 1996).The heating is probably responsible for increased release of material into the water phase though the literature search did not reveal data to support such an expectation.

Mechanical pulping

The type of virgin pulp most often used in the production of newsprint and high- circulation magazine papers is obtained by mechanically separating the fibers in wood. Though this is another mainly mechanical process, the amount of energy expended per unit mass of generated pulp is high, and that may explain why there is significant release of soluble and particulate materials into the water phase (Stephenson and Duff 1996). Mechanical pulping is often carried out at elevated temperatures, i.e. thermomechanical pulping (TMP), which enables softening of the lignin between the fibers, making it possible to preserve a much greater proportion of full-length fibers during the separation process. The heating is probably responsible for increased release of material into the water phase
though the literature search did not reveal data to support such an expectation. The peroxide-bleaching of thermomechanical pulp (BCTMP) is known to convert hemicellulose components of TMP into negatively charged carboxylate species, which readily enter into solution and can contribute to the pollutant load In general, however, high-yield pulps contribute relatively low levels of COD to the effluent.