Degradation and decoloursation studies of paper mill effluents by TiO2 photocatalysis

Abstract

The paper industry has historically been one of the world’s largest consumers of freshwater resources and producers of wastewater discharges. The effluent contains a number of toxic organic compounds that may cause devastating environmental impacts to receiving waters when discharged directly. The scope of this project is to see photocatalysis as a viable treatment option in degrading and mineralizing the recalcitrant organic compounds as well as the possibility of utilizing the solar light spectrum. The experiments and analysis work is done on actual industrial wastewater. The process optimization like pH, catalyst concentration, oxidant dose, light intensity is carried out to obtain the best result for complete transformation of the toxic organic compounds to benign chemicals. The COD reduction of bleaching effluent observed was 86% and 91% under UV and solar light, respectively (with optimized conditions i.e. 7.5 pH, catalyst concentration of 0.5 gL-1 and oxidant dose (H2O2) of 2 ml L-1) after 3 hrs of treatment. The biodegradability (BOD5/COD) of the effluents is improved proposing AOP efficiency as pre-treatment option before biological treatment. Efforts have also been done on the application of AOP for the pre/post-treatment of RO reject water to make it fit for reuse/dilutions in industries. The present study also investigates the efficiency of AOP on color remediation of final ETP effluent. The results of photocatalytic degradation showed that it could be used as pre or post treatment technique for the complete degradation of recalcitrant organic pollutants present in paper mill effluent.