EVALUATION OF GROWTH CHARACTERISTICS OF FILAMENTOUS BACTERIA USING OPTIMISED ISOLATION TECHNIQUES

Filamentous bacteria have been known for decades now, to be the main cause of activated sludge bulking in wastewater treatment worldwide. Attempts to control bulking have thus far failed owing to the fact that current applications are not long-term solutions and if applied wrongly may in fact, inhibit all processes. Also, pure culture studies on filamentous bacteria are still very limited due to difficulty in isolation. It is believe therefore that, isolating filamentous bacteria and studying them in pure culture still remains a necessary step towards uncovering new and long-term solutions to curing filamentous bulking. Previous research focused on optimising conditions for the successful isolation of filamentous bacteria. It was the aim of this study therefore, to characterize on the basis of their cellular and colonial morphology, filamentous bacteria isolated from various activated sludge processes grown on various media. Mixed liquor samples from six wastewater treatment plants located within the Durban Metropolitan area were used for this study. Previously optimised pre-treatment techniques that facilitate easier isolation of filamentous bacteria were applied so as to reduce surface tension between floc-formers and filaments thereby allowing easier separation thereof. With the application of the spread plate technique, serial dilutions of 10-1 to 10-5 of the pre-treated samples were spread onto each of the following media; CGYA, TGYA, SCY and R2A and incubated for at least one to four weeks at 20-25oC. CGYA was a more growth supportive medium for isolates. Seventy isolates were obtained and characterized according to their colonial and cellular morphologies. Since it is not possible to present all the findings in this manuscript, the results for only 14 filamentous types that were presumptively identified according to conventional identification methods are presented herein. Cellular characterization wa