Appropriate control of activated sludge process is crucial for achieving desired effluent quality in the treatment of municipal and industrial wastewater. This paper deals with the development of a feedforward open loop optimal control strategy for a small size single tank ASP system used for the treatment of small volumes of industrial wastewater. The work presented in this paper is a deviation from the usual alternating mode of operation reported in the literature for single tank ASP systems, in which the oxygen supply to the aeration tank is switched on and off in a cyclic manner. The present work has highlighted that regulating the oxygen supply rate alone is ineffective for achieving the desired quality of treated effluent. Further, the need for adding soluble carbon from an external source in addition to regulating the oxygen supply rate is emphasized in this work for effective control of COD and TKN in the treated effluent stream. The proposed control scheme is tested on a single tank ASP model reported in the literature and is found to perform well for various load conditions. Appropriate tuning of controller parameters ensures that the COD and TKN levels do not exceed the limiting values and at the same time the desired effluent quality is achieved at a reduced cost associated with oxygen supply and external carbon addition.