Project Spotlight: Mexico's Atotonilco wastewater treatment plant

Friday, February 2, 2018

The project to build what would become the largest wastewater treatment plant in Mexico and Latin America, a facility located in Atotonilco de Tula, in the central state of Hidalgo, was conceived during the former federal administration.

The plant was seen as a potential solution to existing low wastewater treatment rates in the agriculture-rich Mexico valley basin, where Atotonilco is located.

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A tender was launched in May 2019 and awarded in December of that year to consortium Aguas Tratadas del Valle de México, comprised of Promotora del Desarrollo de América Latina (Ideal), Acciona Agua, Controladora de Operaciones de Infraestructura (Conoisa), Atlatec, Desarrollo y Construcciones Urbanas (Dycusa), and Green Gas Pioneer Crossing Energy. 

The idea was that the plant would treat 60% of wastewater produced in Mexico City, so that it could later be used for the irrigation of 80,000ha of agricultural lands and also for industrial purposes. The goal of the plant is to benefit 700,000 people living in Hidalgo's Mezquital valley, 300,000 of which live in irrigation zones.

PICTURED: Map showing the plant's location. CREDIT: Conagua.

A road full of obstacles

Although originally expected to be completed by 2012, a number of different reasons, such as the complicated topography of the project's site, pushed back the start of the works to 2011. The completion date was postponed a number of times allegedly due to some amendments made to the contract, and also to disagreements with the municipal authorities. 

The initiative finally entered a construction ramp-up phase in December 2016, with capacity tests beginning by mid-2017. 

Originally budgeted at 8bn pesos (US$453mn), the price-tag had already increased to 9.2bn pesos by the time the project was tendered, due to inflation. Based on information from national water authority Conagua from January 2018, the required investment for the plant ended up being 12.46bn pesos.

The facility was built under a DBOT (design, build, operate, and transfer) model, with the contract awarded as a 25-year concession.

While 51% of the total investment was provided and/or secured by the building consortium, the remaining funds came from national infrastructure fund Fonadin.

What is the plant's current status?

Final tests on the plant had already been conducted and successfully concluded in 2017, Aurelio Ignacio López Mier, business development director for the Americas at ​Acciona Agua, told BNamericas late last month.

"Although we are still working on some issues, the plant has been treating water since 2016. We could say that it is already fully operating," López said.

According to the Acciona Agua representative, there are still some legal issues being worked out with Conagua due to some disagreements between the authority and the builders.

PICTURED: A view of the facility. CREDIT: Conagua.

Plant details

The plant has the capacity to treat 23m3/s of wastewater. The water will be supplied through the existing Emisor Central and Emisor Oriente drainage tunnels, the latter which is still under construction.

The facility will also serve to recharge a local aquifer with high quality water. It is also able to generate 32-33 MW of power, which will be used for self-consumption. 

Some 380,000m3 of concrete, 44,000t of reinforced steel, 1Mm2 of geomembrane, 72km of pipes and 2Mt of wire were used during the plant's construction.

The facility will have a useful life of 25 years.