Characterisation of a Leucothrix-type bacterium causing sludge bulking during petrochemical waste-water treatment

Summary From a petro chemical waste-water treatment plant showing sludge bulking, two filamentous microorganisms of the Leucothrix type were isolated. Morphological and some physiological characteristics of the isolates L1 and L2 were compared with the characteristics of two cool water strains of Leucothrix mucor. The main divergences of the isolates were the requirement for biotin and thiamine (L1) or for biotin alone (L2) and the non marine character, since they can grow at a salinity of 5 ppt, without NaCl. It is suggested that the isolates may be new species of the genus Leucothrix, that can cause sludge bulking.