Effluent quality at kraft/soda agro-based paper mills and its treatment using a heterogeneous photocatalytic system

The present study deals with the characterization and treatment of bleach plant effluents generated from Indian varieties of wheat straw or bagasse or hardwood/non wood materials. Spent bleach liquor (SBL) was generated by the chlorination and extraction of unbleached pulp under controlled conditions at laboratory scale. SBL as well as effluents collected from different pulp and paper mills were examined for various characteristics such as total solids (TS), total suspended solids (TSS), total dissolved solids (TDS), pH, chemical oxygen demand (COD), biological oxygen demand (BOD) and chloride ion concentration and their degradation was studied by heterogeneous photocatalytic systems using titanium dioxide (TiO2) and zinc oxide (ZnO) under UV/solar irradiation. The degradation of the organic matter present in the effluent was evaluated as COD removal and reduction in BOD. For the applicability of cost effective heterogeneous photocatalytic process at industrial scale, solar photocatalytic water detoxification was explored and satisfactory results were obtained.