Los Tajos WWTP, Costa Rica

The Los Tajos plant will serve 65% of the estimated population of the metropolitan area of San José, the capital of Costa Rica.

Portada Los Tajos

On September 10, Acciona Agua, together with the Costa Rican Institute of Aqueducts and Sewer Systems (AyA), inaugurated the Los Tajos wastewater treatment plant, which will alleviate the pollution load of the rivers María Aguilar, Tiribí and Torres. The facility will be the biggest in the country and is Acciona Agua’s first project in Costa Rica. The project, representing an investment of 45 million dollars (around 40 million euro), will provide service to over a million people, i.e. 65% of the estimated population of the metropolitan area of the country’s capital city, San José.

FCC Aqualia central, Inodoro

The plant is a primary (i.e. physical-chemical) Wastewater Treatment Plant that will fully treat sludge at an average daily flow rate of 2.81 m3/s and a daily maximum of 3.45 m3/s (Stage I). The Los Tajos WWTP is the core element in Phase I of the Environmental Improvement Project for San José, an action program that also covers the rehabilitation and extension of the sewerage network and secondary connections of over 360 kilometres. It will mean a reduction of untreated sanitary water in the country from 20% to 0.1%. In Phase II, the Improvement Plan will clean up the basin of the River Tárcoles, reducing risks to public health and pollution of the aquifers in the area as well as preparing the city for the level of growth forecast for the next few years.

Acciona’s bid was selected in an international tender process with stringent economic, technical and environmental requirements, particularly as the Environmental Improvement Project was supported by an international cooperation loan from the Japanese Bank for International Cooperation (JBIC).

Acciona Agua was represented at the inauguration ceremony by the company’s Director of Construction, Luis Miguel López-Mier, Business Development Director for America, Ignacio López-Mier, and Project Manager, José Mª Trápaga. Also present were the President of the Republic of Costa Rica, Luis Guillermo Solís Rivera; the Japanese Ambassador to Costa Rica, Mamoru Shinohar; CEO of the AyA, Yamileth Astorga; the Mayor of San José de Costa Rica, Sandra Garcia Perez, and the Spanish Ambassador to Costa Rica, Jesús María Rodríguez-Andía.

The main design objective in Acciona’s tender for the Los Tajos WWTP was compliance with effluent flow requirements, an average daily treatment capacity of 2.81 m3/s and the smallest possible footprint. The aim was to strike a balance between ease of construction of the different stages and optimal operating and maintenance conditions. The following is a summary of the treatment elements of which the plant is composed.

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