The conceptual design of industrial wastewater treatment flowsheets implies the selection and sequencing of technologies in order to obtain a set of feasible treatment options, each achieving the proposed treatment goals. A design methodology was developed to support engineers in the conceptual design of wastewater treatment facilities and help them to improve creativeness and effectiveness. This hierarchical process design package can be described as an expert system coupled to a relational database and external programs integrated as a knowledge-based management system. This study describes the proposed hierarchical procedure and the primary treatment selection prototype.