Is hydraulic retention time an essential parameter for MBR performance?

The effect of hydraulic retention time (HRT) on membrane bioreactors (MBR) operation is discussed. A brief literature review on this topic indicates that biased conclusions can be drawn if data is obtained under non steady-state conditions. Another relevant aspect regarding steady-state operation includes activated sludge adaptation to bioreactor running conditions. In addition, wastewater components also have influence on steady-state achievement and MBR performance. (c) 2007 Elsevier B.V All rights reserved.