This paper discusses the development of control algorithms for the urban wastewater system. This system is considered to comprise of sewer system, wastewater treatment plant and receiving watercourse. Since control actions are affecting the water quality in the river, river water quality based objectives, rather than conventional criteria such as overflow volumes or loads, are applied in this study when determining the optimum control algorithm. The aim of achieving optimum performance of the urban wastewater system with regard to oxygen and ammonium concentrations in the river defines an optimisation problem with multiple objectives, which is solved by application of an evolutionary algorithm and by calling the urban wastewater system simulator SYNOPSIS as a means to evaluate the objective function. Application to control of a semi-hypothetical case study demonstrates the benefits of this technique and encourages further studies in this unique application area.