Abstract. In the project “Labest Papier – Langzeitbeständigkeit von Papier” (Labest Paper – Long-term durability of paper), the suitability of paper to serve as a permanently undamaged information carrier for at least 500 years is to be assessed by the Department of Paper Manufacturing and Mechanical Process Engineering (PMV) for the Federal Office for the Safety of Nuclear Waste Disposal (BASE). The ageing mechanisms of paper are known, as are countermeasures. This leads to standards and recommendations for the use of paper for documents. DIN EN ISO 9706 (2010) is the main proponent of the direction that longevity can be ensured solely via the composition of the paper and the initial situation at the beginning of ageing. DIN 6738 (2007), on the other hand, takes as its basis the approach of assessing the physical ageing of the paper based on artificial ageing and the strength losses observed in the process. Other standards vary the approaches somewhat or mix them in part, for which the lecture presents a comparison table. The usability of a document depends on two essential factors. Firstly, the residual strength after an ageing process must be high enough for the document to be usable. Secondly, the information written on it must still be legible or at least recognisable. The limits of the possibilities for dealing with damage that has already occurred are almost only set by complete destruction. Otherwise, forensic means can restore the information in a document, at least in part, with the appropriate investment of time and money. The lecture provides examples, such as the reprocessing of shredded Stasi files. Even the loss of knowledge of writing and language need not be a final obstacle, as the decipherment of hieroglyphics proves. The costs of measures to deal with damage depend individually on the condition of the documents and on the objectives in dealing with the damage. Prevention is an effective means of avoiding damage and costs in the first place. Paper is an information carrier well known for over 2000 years and has already proven its suitability for storing long-term information. Despite the fact that an intactness in the sense of being completely untouched is never given, paper has the advantage of a long migration time and that no reading or decoding device is necessary compared to modern information storage media, such as digital media or microfilm. Which grade of paper will ultimately meet the demands, however, depends on the overall consideration of the availability of the grade, the expected damage and the possibilities and costs of handling it. There is still a need for research, especially with respect to the assessment of the effect of printing inks and auxiliaries used in paper production on the longevity as well as the classification of recycled paper. An extensive measurement program is investigating this during the current project. After the project is accomplished, BASE will be able to decide in which way the already existing types of papers including marking can be preserved for as long as necessary and how the state-of-the-art optimised system “paper ink” must be prepared to ensure long-term durability. The paper is based on two working stage reports, AP1 (Schaffrath, 2020) and AP2 (Schaffrath, 2021).
Modelling approach to an ultrafiltration process for the removal of dissolved and colloidal substances from treated wastewater for reuse in recycled paper manufacturing
