FILAMENTOUS GROWTH IN ACTIVATED-SLUDGE

Bulking and foaming in activated sludge have been associated with fila mentous overgrowth. Filamentous Nocardia amarae and nonfilamentous Pse udomonas auruginosa were cultured using fatty acids (C2-C24) as the so le carbon. N. amarae could utilize all acids tested for growth, wherea s P. auruginosa hardly grew on acids with 12 or more carbons. Maximum specific growth rate and saturation constant of N. amarae on C24, at 0 .048 h(-1) and 1.520 g COD/L, respectively,were much lower than that o f P. auruginosa, showing that N. amarae had a relatively stronger affi nity for long-chain fatty acids. N. amarae was competitive in activate d sludge processes that receive sewage containing a high proportion of long-chain fatty acids, oils, and fats.