The Kloten Opfikon WWTP treats wastewater from households, businesses and industry in Kloten and Opfikon, as well as from Zurich Airport. Population growth and new statutory water protection requirements meant that the plant had to be substantially expanded, upgraded and refurbished. Planning began more than ten years ago, and TBF supported the major project through every phase, from planning and construction through to commissioning.

The site is hemmed in on every side by the airport, roads, a river, tram tracks and a railway tunnel. The plant also had to be converted while it remained in operation, and without breaching water protection requirements. On top of this came a factor no planning could have foreseen: a global pandemic. Despite everything, the works were successfully completed after eight years of construction.

We were given the opportunity to visit the newly expanded plant. Our two TBF colleagues, Bernhard Buchli (overall project management) and Silke Bauer (senior site supervision), took us on a journey through ten fascinating years of planning and construction. Michael Kasper (AKO management) told us how communication succeeded between all parties involved, and Tino Furrer (biological treatment operations) explained the Nereda® process to us.

The project involved, among other things, a new mechanical pre-treatment stage, the conversion of the biological treatment stage to the innovative Nereda® process, the construction of a new ozonation plant to eliminate micropollutants, and the modernisation of sludge treatment including the construction of two new digester towers. A new staff and operations building was also built for the WWTP.

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