Xylem has been awarded a contract to provide advanced treatment technology to the Werdhölzli wastewater treatment plant in Zurich. The upgrade will make the plant the largest ozone plant for the removal of micropollutants in the world.

The Werdhölzli wastewater treatment plant is already the largest wastewater treatment facility in Switzerland, serving 434,000 people. Xylem’s ozone technology will enable the plant to meet new Swiss regulations on the removal of micropollutants.

Xylem will supply eight Wedeco SMOevo ozone systems to the plant as part of a $51.17 million upgrade project. Once operational, the plant will be able to produce 153 kilograms of ozone per hour to treat a flow of 6,500 liters per second, making it the largest ozone plant for the removal of micropollutants in the world.

The challenge of removing micropollutants

Growing concern about micropollutants is leading many countries to consider more rigorous treatment solutions. Micropollutants are contaminants that are released from everyday products such as industrial chemicals, pharmaceuticals, personal care products, pesticides and hormones. They cannot be removed with conventional wastewater treatment technologies.

“The elimination of micropollutants from wastewater is a challenge that more and more facilities must address,” said Florian Milz, Key Account Manager with Xylem. “While conventional treatment processes do not remove them completely, oxidation with ozone is proving to be one of the most efficient methods for reducing these contaminants. Pollutants, colored substances, odors and microorganisms are directly destroyed by oxidation, without creating harmful chlorinated by-products or significant residues.”

Stricter legislation on removing micropollutants

The European Union has published a list of prioritized substances that pose a threat to ground and surface water sources. To adhere to the environmental standards set by the EU, the member countries have to regularly monitor the occurrence of the listed substances*.

In Switzerland, a 20-year process to upgrade major wastewater treatment plants is underway to tackle such pollutants, which currently remain in treated wastewater and are released into surrounding lakes and rivers. As part of this agenda, new legislation came into effect on January 1, 2016, requiring wastewater treatment plants to implement an additional treatment process, specifically for the removal of micropollutants.

A reliable, cost-effective solution

Peter Wiederkehr, Chief Operating Officer (COO) at Entsorgung + Recycling Zürich explained, “Wastewater treatment plants serving a population of 5,000 or more must now be equipped with a new treatment stage which ensures that up to 80 percent of pre-selected micro pollutants are removed. Extensive research has confirmed ozone as a preferred technology for this stage**. Xylem’s Wedeco SMOevo ozone systems will enable us to meet the new treatment regulations with a reliable, environmentally-friendly and cost-effective solution.”

Xylem will also be responsible for installing the system on-site and training the operators during the commissioning of the upgraded plant. Construction on the Werdhölzli wastewater treatment plant upgrade began in 2016, and the plant is expected to be operational by 2018.

“We are pleased to support this ambitious project in partnership with Carl Heusser AG, Xylem’s official distributor in Switzerland,” said Xylem’s Florian Milz. “Our systems combine maximum flexibility and reliability.”

*Directive 2000/60/EC, Water Framework Directive, and Directive 2013/39/EU