Synthesis of distributed waste treatment systems has been extensively researched on in the past decades. Although the use of centralised treatment systems is widespread in the process industries, distributed treatment systems are proven to be superior to the former, particularly in terms of cost effectiveness. In this work, a recent-developed graphical targeting technique is extended to determine the minimum treatment flowrate for a single-contaminant system with multiple distributed effluent treatment units. Treatment units of fixed outlet concentration and removal ratio types are considered. Apart from locating the minimum treatment flowrate, additional constraints on maximum inlet concentration and specified regulatory limit are also considered in this work. In addition, the targeting technique is extended for cases with multiple treatment units and two-contaminant system. Case studies were solved to illustrate the proposed approach. (C) 2012 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.