Anaerobic/aerobic (AnA) and completely aerobic (CA) laboratory-scale sequencing batch reactors operating on an acetate- and casamino acids-based synthetic wastewater were used to investigate the suitability of the AnA process for treating nutrient?deficient wastewaters in plants that have stringent effluent nutrient requirements. Of particular interest is the case where phosphorus (P)-deficient wastewaters with highly variable influent COD loading are being treated to meet both effluent TSS and P limits. At a 4 d mean cell residence time, AnA activated sludge had an approx. 20% lower P...