The Marinhas WWTP, located in Esposende, has been in operation since June 2000. The aim of this project was the upgrading / extension of the WWTP. Taking into account the conditions of sewage flow for the reference year (2036), the upgrading and extension of the Marinhas WWTP was designed to respond to a population equivalent of 23,383 IE. during high season, and 13,406 IE. during low season. The population in the start-up year (2014) was only 13,930 IE. (60% of nominal capacity) and 8,433 IE. (36% of nominal capacity), respectively during high season and low season.