Aster Bio's Environmental Genomics (genetic testing of MLSS) has found multiple examples of "bulking" organism DNA being present when the system is not yet bulking. In these cases, the organisms are not yet at a bulking threshold or conditions such as sufficient D.O. keep the microbes in their non-filamentous form. An example of sufficient D.O. preventing filament growth happens with S. natans. While often a severe filament, S. natans also effectively removes organics from wastewater. When it grows under aerobic conditions with supporting microbes, S. natans works within the floc as single cells.
As for non-filamentous bulking, conditions that promote excessive EPS production include high soluble BOD (organic acids), low nutrients, and low F/M or food scarcity.
Unlike microscopic or settling tests, genetic testing monitors these organisms before they exhibit problem behaviors. This is due to genetic testing being for specific genotypes vs microscopic exam where we look for phenotypes (appearance or form).