Filamentous bacteria have been known to be the major cause of activated sludge bulking and foaming. Attempts to overcome bulking and foaming have been implemented but have thus far not proven effective as long term remedial procedures as they fail to take account of the physiology and biochemistry of the causative filamentous bacteria. Published data on the biochemistry and physiology of filamentous bacteria is still very scarce due to the difficulties in obtaining pure cultures. Pure culture studies however, still remain a technology that has shown promise as an essential tool in studying filamentous bacteria on the basis of morphology, nutritional requirements and physiology. The aim of this research was therefore to study isolates of Haliscomenobacter hydrossis (HHY1 and HHY2) on the basis of their biochemistry and physiology. The results obtained demonstrated HHY1 and HHY2 were considerably biochemically diverse. They utilize an array of different substrates for growth, including slowly biodegradable polymers (dextrin, starch, edible oils and casein) and, they also grow optimally at wide ranges of temperature and pH. It was also revealed that they possess denitrifying capabilities and belong to the functional group of sequential denitrifiers. This equips them with a survival and growth advantage in a complex growth environment as that of the activated sludge process. These findings may lead to a better understanding of the biochemical and physiological conditions that may incite bulking and/or foaming and a better understanding of Biological Nutrient Removal systems, areas that are still in need of much attention.

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