FACTORS INFLUENCING THE TREATMENT OF AUSTRALIAN PULP-MILL EFFLUENT

The use of chlorine to bleach paper pulp results in the formation of organochlorines, which, if not degraded by effluent treatment have the potential to cause harmful environmental effects. This paper describes the results oi a study aimed at determining the factors important in the degradation of organochlorines, toxicity, colour and chemical oxygen demand (COD) in bleached kraft effluent. Factors investigated included the effects of pH, Eh and nutrient supplementation. Biological activity was found to be important in treating pulp mill effluent. About 10% of the organochlorines in the effluent were removed in sterile controls compared with 40 to 60% in the presence of aerobic and anaerobic microbial activity. BOD and COD reduction were favoured by aerobic conditions. Reduction of all properties tested was approximately the same, whether the effluent was amended with defined nutrients or not, however the addition of raw sewage to the effluent improved the removal of COD and AOX under aerobic conditions, but not under anaerobic conditions. Colour removal was poor in most experiments.