H. Chua et al., Novel feast-fast technique for filamentous foam control in the activated sludge process - introducing a new foam-measurement method, WATER SCI T, 42(3-4), 2000, pp. 95-102
Overgrowth of filamentous Nocardia spp. in the activated sludge microbial e
cosystem was previously identified as the cause of foaming problems in Hong
Kong. in this work, the specific growth rate of N. amarae was found to be
significantly higher than that of non-filamentous bacteria under food-to-mi
croorganism (FIM) ratios lower than 0.5 mgBOD/mgMLSS-day, and was used as t
he basis for the development of a novel Feast-Fast Operation (FFO) for the
prevention and control of foaming problems. The F/M ratio in the "feasting"
aeration unit was 0.8 mgBOD/mgMLSS-day while that in the "fasting" aeratio
n unit was 0.2 mgBOD/mgMLSS-day, resulting in an overall process F/M ratio
that remained within the normal range, while avoided prolonged exposure of
the sludge ecosystem to an F/M ratio below 0.5 mgBOD/mgMLSS-day. The FFO su
ppressed filamentous overgrowth and foaming without adversely affecting the
organic treatment efficiency of the modified process. A new and convenient
measurement method was developed for quantifying the degree of foaming and
foam stability in activated sludge.