CAUSES OF, AND CONTROL STRATEGIES FOR, MICROTHRIX-PARVICELLA BULKING AND FOAMING IN NUTRIENT REMOVAL ACTIVATED-SLUDGE SYSTEMS

Bench and pilot scale nutrient removal activated sludge units were use d to examine the effect of factors such as temperature, substrate type (easily biodegradable in the form of acetate and slowly biodegradable in the form of oleic acid) on Microthrix parvicella growth. The confi gurations examined include complete mix with and without selectors (an oxic and anaerobic) and plug flow reactors. The results indicate that low temperatures and substrates in the form of long chain fatty acids favour the growth of M. parvicella. With respect to reactor configurat ion, a plug flow configuration was shown to be quite effective in cont rolling the growth of M. parvicella and producing a sludge with good s ettling characteristics, while the presence of a selector, either anox ic or anaerobic, had no significant effect on the growth of M. parvice lla. (C) 1998 IAWQ. Published by Elsevier Science Ltd.