An important feature of industrial water and wastewater systems is that the concentrations are subject to fluctuations with time. The most common way to overcome the effects of such fluctuations is to install buffering capacity at strategic locations within the network. This paper presents a systematic strategy for the design and placement of buffering capacity to mitigate concentration changes. The strategy is capable of determining cost-effective designs for application in existing and new networks. The methodology is based on the concept of a steady state flow of water entering and leaving a tank, as in a continuous stirred tank reactor design. The approach is able to deal with any length (time period) and number (frequency of occurrence) of concentration changes. The proposed strategy has been extended to develop an automated methodology based on combined superstructure optimization, which simultaneously identifies optimal designs of networks with effluent treatment and buffering capacity systems. The approaches should be viewed as a tool for screening alternatives, which can then be evaluated in greater detail.