This book is focused on proposing a methodology to estimate the reuse potential of treated water in a region. For this, as a starting point, it was considered necessary to describe the techniques, conditions and factors that must be taken into account to evaluate the operational status of the wastewater treatment plants belonging to the region selected for the study. The methodological proposal estimates the demand for treated water in agriculture, irrigation of green areas, in industry, in car washing and in schools, among other economic activities, supported by publicly accessible information, which greatly facilitates obtaining information. A valuable aspect of the proposed methodology is that it dispenses with the need to collect information in the field regarding water consumption in industries; information that very often companies are not willing to provide. In chapters 1 and 2 there is a description of the general situation that prevails in Mexico regarding the reuse of treated water, as well as the general conditions to take into account to promote the use of treated water. In chapters 3 and 4 detail the proposed procedure to estimate the reuse potential of treated water in a region around wastewater treatment plants. In these chapters reference is made to the annexes of the document where you can find the formats, tables and procedures explained to carry out the detailed technical survey of the wastewater treatment plants, their evaluation and estimation of environmental and social impacts through weighted factors technique evaluation, among other things. Finally, already in the final chapters, an example of application of the proposed methodology that covers the Metropolitan Area of Monterrey, Nuevo León, Mexico is developed, where 11 plants were selected for evaluation based on available public information.