In addition to fibres, other major components of paper are calcium (approx. 20%) and starch (3%). Under the influence of bacteria that feed on the starch, in paper mills where production is based on recycled paper, a great deal of dissolved calcium is produced. Installations that are designed to purify the water from paper mills therefore have to deal with large volumes of dissolved calcium. Following the biological purification process, the purified waste water is practically a saturated solution of calcium carbonate. This water cannot be reused in paper production because the pipelines and sprayers would quickly become clogged with the calcium deposits.
There are a number of methods for removing calcium through the addition of chemicals. However, IWE has developed a method based on disrupting the balances in the water so that no chemicals are required. The result is a water quality that is sufficient to avoid calcium deposits. Using filter systems and a small amount of disinfectant, the water can be made crystal clear and safe for reuse. This process is currently subject to a patent application. For anyone interested in this technology, IWE will be happy to broker the system.