The pH was measuredwith a pH meter (Model
290A, Thermo Fisher Scientific Inc., Beverly, USA) and the
MLSS was measured following the standard method. The DO
concentration was measured using a bench-top pH/DO meter
(Orion 4 STAR, Thermo Fisher Scientific Inc., Beverly, USA)
equipped with a DO probe (Orion 081010MD, Thermo Fisher
Scientific Inc., Beverly, USA)