IN-SITU CHARACTERIZATION OF SUBSTRATE UPTAKE BY MICROTHRIX-PARVICELLAUSING MICROAUTORADIOGRAPHY

Microthrix parvicella is a filamentous microorganism responsible for b ulking and foaming problems in many activated sludge treatment plants. The problems have increased with the introduction of nutrient removal in many countries, and presently, there is no reliable control strate gy for M. parvicella. Little is known about the physiology of M. parvi cella and conflicting data exist about its preferred organic substrate s, and whether it is able to be physiologically active under anaerobic and anoxic conditions. In this study, the ability of M. parvicella to take up various radioactively labeled organic compounds was investiga ted in situ at three nutrient removal plants using a microautoradiogra phic technique. Of 12 compounds tested under aerobic conditions only t he long chain fatty acids (LCFA), oleic acid and palmitic acid, and to some extent a lipid, trioleic acid, were assimilated. None of the sim ple substrates such as acetate, propionate, butyrate, glucose, ethanol , glycine and leucine were taken up. Furthermore, the uptake of oleic acid was compared under anaerobic, anoxic and aerobic conditions, and it was demonstrated that in addition to aerobic conditions M. parvicel la was also able to take up oleic acid under anaerobic and anoxic cond itions. No difference in substrate uptake pattern for M. parvicella wa s found among the tested activated sludge plants. The results strongly indicate that a better control strategy against M. parvicella must re ly on a better understanding of presence and availability of triglycer ides and LCFA, and an improved knowledge of the physiology of M. parvi cella under anaerobic and anoxic conditions. (C) 1998 IAWQ. Published by Elsevier Science Ltd.