Buenos Aires: South America’s Largest Wastewater Treatment Plant Kicks Off

The Riachuelo, a major river that borders Buenos Aires and flows into the Río de la Plata, is breathing again. In early June, a new wastewater treatment plant was brought into service, part of what is called the “Riachuelo System”—the largest environmental remediation project ever undertaken in Argentina, centered on treating the river’s waters.

The project, which involves 14 municipalities and affects over 4.3 million residents, represents a turning point in the fight against water pollution in the Río de la Plata basin. After decades of contamination caused by illegal discharges and sewage, the project marks the beginning of a new environmental era.

The Riachuelo, also known as the Matanza River, was for over 150 years one of the most polluted rivers in Latin America. Its waters were subjected to the irregular dumping of industrial waste and sewage, as well as flooding that affected densely populated neighborhoods of Buenos Aires such as La Boca and Barracas.

In 2006, a class action lawsuit by residents of the basin led the Argentine Supreme Court to order the government to clean up the river. From that ruling was born the “Riachuelo System,” a colossal sustainable infrastructure project also supported by the World Bank.

The Riachuelo System is divided into three major infrastructure sections. The first included the construction of main collectors and all the necessary works to intercept wastewater and rainwater and channel it deep underground.

But the beating heart of the system is Section 2, entrusted to Fisia Italimpianti—a leading water sector company controlled by the Webuild Group—which involved the construction of a state-of-the-art pretreatment plant.

Section 3, built by the Webuild Group, consists of a hydraulic tunnel dug 40 meters deep beneath the bed of the Río de la Plata. It spans 12 kilometers in length and is equipped with 34 vertical diffusers (“risers”) that allow for the controlled release of treated water further out in the river.

Section 2 is located in the port area of Avellaneda, south of Buenos Aires. It is here that the wastewater, channeled 40 meters underground, is lifted by a pumping station with a capacity of 36 m³/sec and sent for pretreatment.

The process is divided into two phases:

1. In the first, solid debris is removed.
2. In the second, sand, oils, and fats are separated from the water using micro air bubbles in 32 aerated channels.

Once treated, the water is transferred to the intake chamber and injected into the tunnel to be carried to the Río de la Plata. Overall, the system can treat 2.3 million cubic meters of polluted water per day, with an average flow rate of 27 m³ per second.

The environmental, economic, and social benefits resulting from the Riachuelo System are vast.

In addition to directly treating the river, for the first time in 70 years the project has also expanded the sewage treatment network of the Buenos Aires metropolitan area, allowing 1.5 million new users to access the system, drastically reducing health risks linked to water pollution and improving services in 14 municipalities across the city.

Overall, the Riachuelo System aligns with the UN’s Sustainable Development Goals by promoting the protection of aquatic and terrestrial ecosystems, enhancing urban quality of life, and contributing to the fight against sewage pollution.

The entire project has been recognized as a concrete example of resilient and sustainable infrastructure development, replicable in other highly urbanized and environmentally stressed areas.