This article presents an approach to designing a large-scale water system, which integrates water-using operations and wastewater treatment units in different production sections within the same network. This approach uses a mixed-integer nonlinear programming (MINLP) model for water reuse and regeneration reuse in batch and semicontinuous processes. The application of this mathematical formulation to large-scale industrial problems with changing daily production schedule leads to huge and complex mathematical models. Two alternative multilevel strategies are proposed to solve such problems by means of temporal decomposition. The approach is illustrated with a brewery case study that integrates water consumers in two production sections. The results obtained show that, despite the high piping cost, integration of both sections yields better result than the separate water network design in each section. (c) 2011 American Institute of Chemical Engineers AIChE J, 2012