La Atarjea potable water treatment plant, Water treatment plant in El Agustino, Peru

La Atarjea is a water treatment plant in El Agustino that processes water from the Rimac River through several purification stages. The facility uses settling tanks, sand filters, and other filtration methods to produce water safe for drinking.

The plant opened in 1956 and was the world's largest water treatment facility at that time. Its operation marked a turning point in Lima's water supply, as it replaced the practice of using river water directly for the city's needs.

The name Atarjea comes from an old colonial-era water deposit behind the Presbítero Maestro cemetery, which supplied Lima before the plant existed. The plant was designed by the French firm Degremont and inaugurated on 28 July 1956. Its intake channels capture Rímac River water after a descent of about 5,000 metres through narrow and rocky ravines.

The plant sits in El Agustino, east of central Lima, and is an operating industrial site, not a visitor attraction. There is no public tour circuit; access to the grounds requires authorization from the operator, Sedapal. Views of the intake and treatment structures are limited from outside the perimeter.

The plant's name comes from an older reservoir called Atarjea, built in the viceregal era behind the Presbítero Maestro cemetery. The modern plant was designed by the French firm Degremont and inaugurated on 23 July 1956, entering service on 28 July.