Application of ozonation and biotreatment for forest industry wastewater

This research is focused on the integrated process for the treatment of bleached Kraft pulp mill effluents. Pre-ozonation of softwood and hardwood combined bleaching effluents at alkaline pH resulted in 50 and 44% COD abatement, respectively. Segregation of highly polluted streams of bleaching process can be recommended to reduce the cost of treatment since the COD removal yield of CEH effluents was higher than combined bleaching effluents. Moreover, biodegradability of CEH effluents in terms of BOD5/COD ratio was increased from 0.16 to 0.32. Noticeable color removal was achieved by pre-ozonation of the CEH stage and combined bleaching effluents. Pre-ozonation enhanced the performance of subsequent algal treatment in the sequential batch reactor (SBR) and activated sludge treatment. Algae have a higher ability to degrade AOX producing compounds together with a high COD removal rate. Although pre-ozonation increased the abatement rate of COD of SBR, the AOX removal rate remained constant as 87%.