Application of Ultrafiltration Membrane Technology in Pulp and Paper Mills in Indian Context: A Review

Abstract

In general, Indian pulp and paper mills generate 25–225 m $^3$ wastewater/tonne of paper. Pulp and paper mill effluent carries high pollution load in terms of COD, BOD, absorbable organic halides (AOX) and is dark brown in colour mainly due to the lignin and lignin derivatives. Stringent application of new environmental norms in the form of CREP (Corporate Responsibility for Environmental Protection) has forced many mills to close down their operation. Hence, large proportion of water now being discharged need to be recycled back into the system at the appropriate intake points with/without treatment. There are several conventional treatment processes employed in Indian paper industry which effectively remove BOD, TSS, and also COD but do not remove colour, AOX, heavy metal and process chemicals as per the desired level to recirculate the process water in good condition.

Membrane technology is being adopted increasingly in the paper mills for closing their mill production process. Application of membrane technology is one such option which can improve the recycled water quality by removal of heavy metal contaminates, COD, TSS, colour, AOX, and lignin. This shall reduce the load on conventional recovery evaporation system with no significant loss of inorganic compounds. Membranes also provide an effective method of closing the chelating stages and allow the filtrates to be used as bleach plant wash liquors. Membrane filtration also allows efficient recycling of white water. The present paper reviews current status of ultrafiltration in terms of R efforts and its application to the paper industry with due focus of system closure in Indian pulp and paper mills.