In situ enzyme activities of filamentous scum bacteria in municipal activated sludge wastewater treatment plants

In situ phosphatase, esterase, lipase, and β-glucuronidase activities were investigated in filamentous scum bacteria by ELF (enzyme labeled fluorescence)-technology. Microthrix parvicella exhibited significant activities for all four enzymes with lipase activity being the highest. In situ activities were considerably higher in activated sludge as compared to scum indicating M. parvicella growth to occur mainly in the sludge fraction. "Nocardioform actinomycetes" showed significant activities for phosphatase, esterase, and β-glucuronidase, lipase activity was only moderate. Activities revealed to be similar for activated sludge and scum. As population densities of enzyme-active actinomycetes were noticeably higher in scum they presumably find good growth conditions in the scum layer. Enzyme activities in Nostocoida limicola morphotypes were only low with no lipase activity being detected. Due to their phylogenetic diversity activity assignment should be combined with fluorescence in situ hybridization (FISH). Numerous type 0041/0675 and type 1851 filaments showed all but lipase activity. However, some of their attached bacteria revealed to be lipase-active. Only a few morphotype 0092 filaments revealed phosphatase, esterase, and β-glucuronidase activity. ELF investigations proved suitable for monitoring in situ filamentous activity. Present imponderabilities of Eikelboom morphotype phylogenetic affiliation are discussed.