Removal of chloro-organics and color from pulp and paper mill wastewater by polyaluminium chloride as coagulant

Abstract

This study evaluates the effectiveness of polyaluminium chloride (PAC) as a coagulant for the treatment of pulp and paper mill wastewater. The wastewater was characterized for different chloro-organic compounds, i.e. adsorbable organic halides (AOX), chlorophenolics, and chlorinated resin and fatty acids (cRFA). Four categories of chlorophenolics (chlorophenols, chlorocatechols, chloroguaiacols, and chlorosyringaldehyde) and four cRFA were detected in the wastewater. For coagulation studies, optimization of the process variables including initial pH, coagulant dosage, time, and initial organic load was done in terms of chemical oxygen demand and color removal efficiency. Under optimized conditions (pH 8.0, PAC dose 1.5 g/L, time 90 min.), the removal efficiency for AOX, chlorophenolics, and cRFA was 66, 41, and 87%, respectively. The chlorophenolics, i.e. 2,6-dichlorophenol, 3,4-dichlorophenol, 3,4,6-trichloroguaiacol, tetrachloroguaiacol, and 2,6-dichlorosyringaldehyde were not detected after treatment studies. Among different parameters, highest removal of color was observed from wastewater by PAC.