Microbial Degradation of Lignin for Decolourisation of Bleach Plant Effluents

Abstract

Pulp and paper industry generates large volumes of highly heterogeneous waste streams containing compounds from wood or other raw materials, process chemicals and compounds formed during processing. For each ton of pulp manufactured, the wastewater discharge ranges from 30-180 m3, while 20-70 m3 newlineis discharged for each ton of paper and paper board manufactured. Quantities and characteristics of the wastewaters generated are highly dependent on the raw materials, and processes used and on the process conditions. Pulping and bleaching processes are the two major sources of wastewater in comparison to paper machines which contribute little. newlineThe effluents from conventional bleaching processes are of growing environmental concern because of their dark brown colour and presence of toxic chlorinated lignin degradation products, including Chlorophenols, chloroguiacols, and chloroaliphatics. Bleach effluents may cause problems like oxygen deficiency, acute or chronic toxicity, mutagenicity, etc., in the receiving water bodies. Most of the pollution load, of the bleach effluents, is contributed newlineby the first extraction stage of the bleaching process. About 75% of the dissolved organic material, and 60% of the organically bound chlorine, of the bleach plant effluents, are reportedly contributed by the first extraction stage effluents. Hence, it is believed that environmentally safe handling and disposal of first extraction stage effluents can almost lead to tackling of the environmental pollution problems associated with bleach effluents. newlineIncreasing environmental awareness coupled with stringent environmental legislation and regulations are forcing the pulp and paper industry to adopt a multiplicity of strategies for tackling the pollution problems associated with bleach effluents. These strategies include: newline1. Modifications of the manufacturing processes for minimisation of wastes at newlinesource.