This document is part of the IETC series of Introductory Guides for Decision-makers. These guides are intended to assist decision-makers at the local level in understanding the issues and making informed decisions for the benefit of all citizens and stakeholders. The scope of sewage management has evolved throughout history with changes in socioeconomic conditions, city structures, and the environment. Today, sewage infrastructure that is well planned and operated supports urban sanitation and related activities. Effective sewage management is essential for nutrient recycling and for maintaining ecosystem integrity.