“…Several models have focused on the degradation of organic compounds by a single heterotrophic population (Casey et al ., 1999a(Casey et al ., , 2000Debus and Wanner, 1992 ;Essila et al ., 2000 ;Motlagh et al ., 2006 ;Semmens and Essila, 2001 ;Syron and Casey, 2008b ;Wanner et al ., 1994 ). A few studies have developed multipopulation models to investigate simultaneous removal of organics and nitrogen (Matsumoto et al ., 2007 ;Shanahan and Semmens, 2004 ;Terada et al ., 2007 ).…”