Journal of Scientific & Industrial Research Vol. 63, June 2004, pp 527-535 Characterization of chlorinated organic material in Eucalyptus pulp bleaching effluents M Roy*, S K Chakrabarti, N K Bharadwaj, Sandip Chandra, Sanjay Kumar, Sarabjeet Singh and P K Bajpai Thapar Centre for Industrial Research & Development, Bhadson Road, Patiala 147 004, Punjab and M B Jauhari T-57, Sector 12, Noida 201301, UP Received 22 October 2003; accepted 12 February 2004 Elemental chlorine and chlorine compounds are commonly used in the developing countries for bleaching of pulp. The study deals with the bleaching of eucalyptus pulp with chlorine, hypochlorite, and chlorine dioxide and identification of various organochlorine compounds generated in the bleach effluents at different stages. Molecular weight distribution of macromolecules present in bleach effluents at different stages have also been studied Keywords: Eucalyptus pulp, Bleaching, Organochlorine compounds, Toxic effluent IPC Code: Int.Cl 7 : C 01 B 21/00 Introduction The pulp produced by chemical pulping requires bleaching to produce bright pulps. Elemental chlorine and chlorine compounds are commonly used, particularly in the developing countries for bleaching of pulp. Various kinds of chlorinated phenols, phenolic carboxylic acids, dicarboxylic acids, resin acids and hydrocarbons origi- nating from lignin and/or extractions of wood are found to be present in the bleach effluent 1-12 . Studies 13-15 indi- cate that some of the chlorinated organic compounds present in the wastewater of bleached pulp mills are toxic, mutagenic, and resistant to biodegradation. Some of the compounds known to impart toxicity are; 2,4,5– trichlorophenol, tetra- and penta-chlorophenols, tetra-chlorocatechol, 3,4,5-trichloroguiacol tetra- chloroguaiacol, polychlorinated dibenzo-p-dioxins (PCDD), and furans (PCDF). The components of particular concern are tetra-chlorodioxin (TCDD) and tetra-chloro difuran (TCDF) 16,17 . The detection 1 of TCDDs and TCDFs in pulp and paper mill effluents prompted many researchers to study the release and control of toxic pol- lutants in the pulp bleaching process with chlorine or chlorine derivatives. Softwoods, which are used in large proportion by European and North American countries for pulping proc- esses, are reported to release high amount of chlorinated organics on chlorine bleaching. 13,18,19 . Not much infor- mation is available on the nature and quantities of various organochlorine compounds present in bleach plant effluents formed from Indian varieties of hard woods or agro-residues. In our earlier work 20 , we have studied the effect of different pulping and bleaching conditions on the generation of pollutants, e.g., colour, COD, AOX, EOX and POX, using Eucalyptus as raw material. In the present study, we report the results of the detection and quantitative determination of various pollutants formed during different bleaching (chlorine and chlorine com- pounds) sequences, using Eucalyptus (Eucalyptus teretecornis), which is one of the important pulping raw ma- terials in Indian subcontinent and several other countries, including Australia, Brazil and European community. All the organochlorine compounds may not be toxic. For example, many chlorophenols and chloroacetones, in addition to other chloroorganics, are toxic. It is therefore, necessary to identify these compounds at different stages of bleaching to assess the extent of toxicity in bleaching effluents. This study will help in deciding about the bleaching stages to be followed in the pulp & paper industry. Experimental Procedure