2.2. Kinetic selection studies
The predominant filamentous microorganism (later identified as Nocardia amarae, ATCC 27810) and Pseduomonas aeruginosa (CRCC 10261) were used to represent the filamentous and non-filamentous floc-forming bacteria in activated sludge. The cultures were maintained on yeast-extract-glucose agar slants at 2–4 °C.