This project originated with a Task Force of the Water Environment Federation's (WEF's) Spanish- and Portuguese-Speaking Advisory Group, to develop the Wastewater Engineering Glossary. The primary source of wastewater engineering terms is the glossary in Operation of Municipal Wastewater Treatment Plants (MOP 11 - 4th Edition). The glossary was developed as a reference tool for engineering professionals in Spanish-speaking countries working with technical materials written in English. Conversely, the glossary is of value to the same spectrum of engineering professionals in English-speaking countries working with technical materials written in Spanish.