Reliability of Morphological Approach for Bulking Filamentous Bacteria Identification in Activated Sludge Plants

Activated sludge process is the most commonly applied technology for the biological treatment of wastewater. However, operational failures and deterioration of treatment efficiency due to extensive and uncontrolled growth of filamentous bacteria have been reported worldwide as common problems of this method. Over the years, various methods have been developed and applied for the identification of these bacteria in an attempt to find a solution to the bulking problem. In this study, morphological techniques were used to identify dominant filamentous bacteria in activated sludge plants in Ghana. Fluorescence in situ hybridization was subsequently applied to assess the reliability of the morphological results. The findings indicate that the usefulness of morphological approach for routine identification of filamentous bacteria for the purpose of bulking control should not be underestimated since the results of this approach agreed largely with the probe-defined results. Reliability of morphological results, however, can be improved when plant operators would have previously applied molecular techniques to identify these filaments. Where molecular techniques are available, morphological identification can also serve as a preceding rapid screening tool for subsequent probe selection.