ADSORBABLE ORGANIC HALIDE REMOVAL MECHANISMS IN A PULP AND PAPER-MILLAERATED LAGOON TREATMENT SYSTEM

The aerated lagoon treatment system of a New Zealand pulp and paper mi ll exhibited 65% removal of adsorbable organic halide (AOX). This valu e is high compared to published data and an assessment was made of pos sible mechanisms for the observed AOX removal. Much of this removal to ok place in a short section (3.3 hour residence time) of the system's main lagoon. The initial AOX decrease in the aqueous phase could be ac hieved in part by settling of AOX-containing suspended solids from the influent wastewaters and by alkaline dehalogenation. In addition, lim e and bacterial solids present in the treatment system were able to ad sorb AOX from the influent wastewaters. Only a small proportion of the organic chlorine removed was found in sludges. A mass balance of aque ous and solid phases indicated that over 99% of the removed AOX was mi neralised.