The causes of variability in the membrane bioreactor treatment of pulp and paper wastewater

The Gippsland Water Factory treats pulping and bleaching wastewater from Australian Paper. This study of a full-scale treatment system investigated the causes of periods of reduced treatment efficiency in the membrane bioreactors. This cross disciplinary investigation combined aspects of engineering, process microbiology, process chemistry and statistics to gain a high-quality picture of the possible causes. Data indicated a relatively stable bacterial population which was not affected by the periods of low treatment efficiency. The ultimate cause was determined to be carbonaceous colloids from ‘Black Liquor’ which is resistant to treatment and accumulates in the mixed liquor supernatant.