Upgrading Effluent Treatment Plant Performance in Small Non-Wood Based Pulp Mills Through Lignin Removal Process- A Pilot Scale Experience, 2001 Pulping Conference Proceedings

R. K. Jain, A. Gupta, R. M. Mathur, A. G. Kulkarni--In absence of a viable chemical recovery system, handling of black liquor rich effluents is of major concern for survival of small agro based pulp and paper mills. Presence of lignin in the black liquor limits the treatment efficiency of biological treatment systems to around 50% of COD. It becomes difficult for these mills to achieve standard discharge norms in terms of COD and color.

The present paper discusses the Lignin Removal Process (LRP) developed at CPPRI for selective separation of only high molar mass fraction of lignin, which accounts for nearly 70% of the total lignin present in the black liquor. The liquor after removal of lignin becomes more amenable to biological treatment. The process has been up scaled to pilot scale to process 15-20 M 3 of black liquor, which has been in continuous operation in an agro-based mill. The performance of the pilot plant has been highly satisfactory, wherein overall COD reduction of 80-85% is achieved against 50% in conventional treatment systems, thus making it possible to reach closer to the desired standard norms. Utilization of precipitated lignin as saleable phenolic derivative will make the process more attractive for commercialization in small agro based pulp and paper mills in India and abroad.