Quantification of Microthrix parvicella in activated sludge bacterial communities by real-time PCR

Aims: This study was to develop a simple and reliable method for quantifying Microthrix parvicella 16S rRNA gene copies and its application to activated sludge samples collected from wastewater treatment plants (WWTP) with and without foaming problems. Methodds and Results: The relative frequency of M. parvicella was determined by combining real-time PCR assays for quantification of total bacterial 16S rRNA gene copies and M. parvicella 16S rRNA gene copies. The developed method was applied to analyse 32 activated sludge samples obtained from German WWTP. The level of M. parvicella 16S rRNA gene copies in the 18 nonfoaming samples was below 3% of the total number of 16S rRNA gene copies and in the range of 0-18% for the 14 foaming samples. Conclusions: The described method allows reliable monitoring of the amount of M. parvicella in activated sludge samples. Significance and Impact of the Study: The described method may become an important component of a warning system for forthcoming bulking and foaming episodes.