+ 1.4 M

Population equivalent

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 clean up the River Tárcoles basin, reducing public health risks and pollution of the aquifers in the area.

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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