After Over a Decade of Foaming, the Development of a Statistical Model Combined with Traditional Microscopy Provides Operating Guidelines

The goal of this study was to use traditional microscopy in conjunction with statistical analysis of Manhattan WWTP data to discern what operational factors have the most significant impact on the presence or absence of filament-induced foaming, and to develop a probability model that allows operators to predict the probability of foaming given operating parameters. Current microscopy suggests the observed filaments (primarily Nocardioforms, Nostocoida limicola II, and Type 1851) are caused by a combination of oil and grease, volatile fatty acids, low F/M ratios, and high SRT conditions. Two probability models were developed, and both showed that Temperature, SRT, F/M ratio, mixed liquor TSS, and mixed liquor VSS are all statistically significant predictors of foaming. Additionally, individual predictor logistic curves were prepared to help the plant staff determine operating regimes that allow them to keep the WWTP operating under a desired probability of foaming.