The city of Zurich is a highly populated area in Switzerland with a substantial economic value creation. SMEs are an important part of this value creation and are financially affected by tightening legislation and water quality standards. Drinking water in the area is provided by springs (20%), groundwater (40%) and lakes (40%).

The general water status is satisfactory; however objectives of water laws and Directives are not fully achieved and new challenges require new technologies and instruments to be assessed and implemented. Regarding water quality the following issues are identified as most relevant: new micro-pollutants, nitrate pollution, low carrying capacity of receiving water bodies, renewal and extension of existing collection network and treatment plants. Regarding water quantity, important factors include: sprawling urbanization, canalization, increasing frequency of extreme flood events, vulnerable groundwater tables. Current strategies have proved unable to meet these challenges.

With regard to water quality parameters, defined objectives are met at about 65% of measurement spots. Of the amount of 222 million m³ of wastewater that was treated in 2005, 99% was treated mechanically, biologically and with removal of phosphates. Additional filtration (4th stage treatment) was applied to 72% of treated volumes. Less than 1% of the received wastewater was discharged with only a mechanical treatment. The above resulted  in 27,400 tons of sludge (dry substance) that cannot be directly used as fertilizer and is mainly incinerated or co-processed.

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