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.
Keywords: Ultrafiltration membrane, pulp and paper mill, system closure, paper mill effluent
