1.4 M

Equivalent Inhabitants

Treatment of wastewaters

The design is for a primary Wastewater Treatment Plant (WWTP) with complete sludge treatment, with an average flow of 2.81 m3 and a maximum flow of 3.45 m3 (phase I), to serve more than one million people, representing 65% of the estimated population of the metropolitan area of the capital city, San José.

The Los Tajos WWTP is the cornerstone of Phase I of the San José Environmental Improvement Project, a program aimed at the upgrading and expansion of the more than 360-kilometre network primary and secondary sewer networks. This will mean a reduction of untreated sewage in the country from 20% to 0.1% of the total.


In Phase II, the Improvement Plan will clean up the River Tárcoles basin, reducing public health risks and pollution of the aquifers in the area, as well as preparing the city for the growth forecast for the next few years.

General Information

  • Location: San José, Costa Rica
  • Capacity: 242,784 m3/d
  • Contract type: D&C commissioning, technology transfer and assistance in O&M
  • Equivalent population: 1.4 million people

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