Identification and advanced oxidation of chloro-organics from bleaching wastewater of pulp and paper mill

Abstract

This study evaluates the effectiveness of ozonation process for the treatment of pulp and paper mill wastewater from bleaching section. The wastewater was characterized for different chloro-organic compounds i.e. adsorbable organic halides (AOX), chlorophenolics, and chloro resin & fatty acids (cRFA). Six categories of chlorophenolics (chlorophenols (CP), chlorocatechols (CC), chloroguaiacols (CG), chlorosyringol (CS), chlorosyringaldehyde (CSA), and chlorovanilline (CV)) and four cRFA were detected in the bleaching wastewater. For ozonation studies, optimization of process variables including initial pH of wastewater and ozone dosage was done in terms of chemical oxygen demand (COD) and color removal efficiency. Under optimized conditions of pH (9.0) and dosage of ozone (1.3 mg O3/mg COD), the removal efficiency for AOX, chlorophenolics, and cRFA was 73, 89, and 92%, respectively. After ozonation, the biodegradability of wastewater was increased about two times. This process proved to be more effective for the removal of cRFA and highly chlorinated chlorophenolics.