The activated sludge process (ASP) has high operational costs due to the need for aeration at dissolved O-2 (DO) levels of a parts per thousand yen2 mg l(-1) and high capital costs to construct large reactors due to a low organic loading [typically 1 kg chemical oxygen demand (COD) m(-3) day(-1)]. A novel method for improving the energy use and treatment efficiency of the ASP via limited oxygenation (0.4 mg DO l(-1)) and high organic loading (6.2 kg COD m(-3) day(-1)) is proposed based on a laboratory-scale ASP for ammonia-rich industrial wastewaters. The sludge blanket phenomenon and granulation occurred simultaneously in the upflow microaerobic reactor.