H H.Ahmadian B - Department of Chemical and Petroleum Engineering, Sharif University of Tecnhonology,Tehran,Iran
R . B Boozarjomehry - Department of Chemical and Petroleum Engineering, Sharif University of Tecnhonology,Tehran,Iran
D Rashtchian - Department of Chemical and Petroleum Engineering, Sharif University of Tecnhonology,Tehran,Iran

A new methodology for targeting minimum effluent treatment flow rate satisfying minimum freshwater requirement is proposed in this paper where it can be applied to fixed-flowrate as well as fixed-contaminant-load problems having a single or multiple contaminants. Asuperstructure is developed for the synthesis of distributed wastewater treatment networks with stream recycles and then an ant colony algorithm is used in this study to solve the WUTN optimization problem. To apply ACO, the problem must be represented by an appropriate graph along which the ant moves to construct candidate solutions. For single contaminant water-using systems, ACO and other algorithms as well as Lingo can nd the same minimum freshwater consumption. For multiple contaminants systems, it can nd the same or better results in case studies. Moreover, ACO can yield many water-using networks consuming the same minimum freshwater but with different congurations, whereas Lingo yields only one network.

Ant colony; Wastewater minimization; Water network