Identification and quantification of the main sources of dissolved and colloidal materials in recovered papers

The use of recovered fibres as raw materials in the paper industry presents many environmental and economical advantages. However it has also serious drawbacks due to the high amount and the high number of contaminants introduced in the system.These problems are worsened as a consequence of the closing-up of the process water systems; the immediate consequence, that limits the closure degree, is the build-up of dissolved and colloidal material (DCM) in the system. In this paper, the main sources of dissolved and colloidal materials are reviewed : The main sources at the origin of DCM are investigated (papermaking, converting additives, fibres themselves...). The contribution of each source to induce DCM in waters is assessed and then, for various types of recovered paper taking into account the level of occurrence of the sources, the potential of DCM formation in reslushing waters is estimated. This estimation which simulates the contribution of each source is rather close to the reality : estimations and measurements performed on the same raw materials give roughly the same level of DCM in the case of the brown sorts of raw materials used for the production of packaging papers.