Tertiary treatment of pulp and paper mill wastewaters by ozonation and O₃/H₂O₂ techniques

The efficiency of ozonation and O₃/H₂O₂ techniques for biologically treated pulp and paper mill wastewaters were examined on a laboratory scale. Studied parameters were COD, BOD, TOC, colour, and AOX. It was found that both of the examined techniques removed colour and AOX efficiently with a reasonable operational cost, but that they removed COD and TOC only moderately. The addition of H₂O₂ improved the colour and AOX reductions but it did not improve the COD and TOC reductions to any significant extent. The biodegradability was increased by both of these techniques but greater biodegradability was achieved with ozonation. The process solution should be decided case specifically since the purification efficiency of ozonation and O₃/H₂O₂ depends largely on the water matrix.