Microscopic studies of activated sludges in biological waste water treatment plants of the paper industry

Paper mill effluents that have been subjected to aerobic biological treatment frequently tend to form activated sludge with a high share of filiform microorganisms and a high sludge volume index. However, changes occurring in the microbiota are identified inadequately or too late by the chemical analytics that are typically being applied to monitor waste water treatment plants today. Regular microscopy of the activated sludge by comparison allows timely detection of such changes so that appropriate countermeasures can be initiated. Microscopic studies and measurements of operating conditions which were conducted in 13 waste water treatment plants of the paper industry have successfully identified relevant microorganisms in aerobic-biological treatment plants, The investigations included variation in the microbiota depending on loads and process engineering techniques. 021N, beggiatoa and thiothrix (sulfur bacteria) as well as H. hydrossis and nosticoida limicola were identified to be the dominant filiform bacteria. A database-assisted assessment and information system has been developed to monitor aerobic-biological effluent treatment plants. The system evaluates and compares the results obtained from microscopy and analytics and proposes suitable remedial action in case of operating failures.