Wastewater management is essential in the daily life of human beings since it allows its future reuse and, therefore, this resource is not lost with the course of time. Moreover, in the history of humanity, no large city or civilization has been able to grow without treating its sewage, due to the large number of diseases prevented by this process. The purposes of this work are several, but the main one is to conduct a comprehensive study on the reuse of wastewater in the city of Chicago with the aim of being aware of all the details that it has, covering all the points included in it and focusing on those that are most important in the process. Trying to optimize this process and making readers aware of the enormous scope and the tremendous importance of this procedure are the other two major objectives of this project. The Chicago River is the only river in the world in which its course has been artificially reversed in order to improve water treatment management, not by flowing towards the Lake Michigan, but by moving away from it. On the other hand, the City of Chicago has two of the most important civil engineering superstructures built in recent years, the Stickney sewage treatment plant and the Tunnel and Reservoir Plan (TARP). Trying to understand these three concepts is fundamental to understand water reuse in a metropolitan area that reaches 9.5 million people. The concise presentation of the entire wastewater management process in the city of Chicago, the subsequent report on possible improvements for optimal water reuse, and the comparison of Chicago's wastewater management with that of Barcelona, one of the most elite cities in terms of wastewater management, will be the main results or findings of the project. The results obtained will lead the author to make a precise and concrete conclusion about an issue which is possibly the most important subject that human beings have faced in their existence, but which does not attract the media focus and, consequently, most of the society does not give it its due importance.