Yen Xa wastewater plant sparks hope of reviving Hanoi’s rivers
Hannah Dang
August 21, 2025 | 09:30 AM GMT+7
The recently inaugurated Yen Xa wastewater treatment plant is seen as a game changer in Hanoi’s decades-long battle against water pollution.
For generations, rivers such as To Lich, Lu and Set once embodied the character of the capital. Today, however, they are more often remembered for foul odors, darkened waters, and the urban environmental crisis they symbolize.
Residents have grown accustomed to these rivers doubling as open sewers, while temporary measures like dredging, water pumping or deodorizing have done little more than treat symptoms.
On August 19, 2025, after five years of construction, the Yen Xa wastewater treatment plant was officially launched. With a daily capacity of 270,000 cubic meters, serving over one million residents across 20 inner-city wards, it is the largest wastewater treatment plant in northern Vietnam.
Its scale nearly matches the combined output of Hanoi’s existing seven treatment plants, positioning it as a pivotal lever in the city’s plan to collect and treat 50 to 55 per cent of urban wastewater under the Hanoi Party Committee’s 2021 - 2025 urban development program.
Inside the the control room of Yen Xa wastewater treatment plant.
What sets Yen Xa apart is not just its size but its integrated approach. For the first time, Hanoi has rolled out a combined system of intercepting sewers, collection pipelines, and a central treatment hub stretching over 40 kilometers, 24 of which were built using Japan’s trenchless pipe-jacking technology. The method ensures technical durability while minimizing disruption to daily urban life.
The facility employs AO (anoxic and oxic) activated sludge treatment, an advanced process capable of removing organic matter, nitrogen, and phosphorus, widely adopted in major global cities.
Yet experts emphasize that Hanoi’s rivers can only truly recover through a comprehensive framework: strict control of industrial discharges, consistent wastewater collection, behavioral change in households, and above all, urban planning that integrates water as a living part of the city’s landscape.
Viewed more broadly, Yen Xa represents a shift in Hanoi’s urban governance, from reactive, stopgap measures toward strategic and long-term investment.
It is also a case study in effective international cooperation with the project being funded by Japanese ODA through JICA, the project highlights the transformative impact of development loans when directed toward core infrastructure tied to community well-being.
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