Purification of Waste Bleach Waters, Polymeric Lignins, Biological Methods, Physiological, Ultrafiltration, Biological Treatment

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	Purification of Waste Bleach Waters - (a) Biological methods. In paper industry, waste bleach waters are currently treated using aerated lagoons (having bacteria) and activated sludge plants. These methods, however, can not remove high molecular mass chlorinated materials. In view of this, the use of white rot fungi is recommended, since they can degrade polymeric lignins.
However, white rot fungi have not been used on a commercial scale, due to their complicated physiological demands (energy source), which are difficult to satisfy on a large scale. (b) Ultrafiltration combined with biological treatment. Ultrafiltration of the effluents of paper industry reduces TOCI from 50% to 35-45% (3 kg/tonne pulp), which can be further reduced to 2 kg/tonne pulp, by combining ultrafiltration with oxygen bleaching. The effluent, however, is still acutely toxic, so that further biological treatment is needed. Following biological methods are available: (i) use of aerated lagoons, which are expensive: (ii) fungal treatment, particularly filamentous fungi (e.g. white-rot fungus = Phanerochaete chrysosporum), which can be filtered off and recirculated to the process.