Waste water treated by strong light 

A pilot project in Copenhagen is to cleanse waste water by passing it through a fine mesh net and exposing it to strong light to kill off micro-organisms.
A pilot project in Svanemøllebugten, Copenhagen, will for the first time cleanse a mixture of waste water and rainwater from urban areas by exposing it to strong light.

The aim is to find out how waste water in Denmark and elsewhere can be treated in a cost-effective manner at times of heavy rain. Heavy rainfall causes urban combined sewer systems to overflow, resulting in untreated waste water being discharged into the surrounding surface waters. This causes pollution in the watercourses and coastal areas.

Eliminating everything

The first step in the treatment process is to apply a grit, eliminating everything from footballs to supermarket trolleys. Secondly, impurities are then removed by passing the waste water through a fine mesh filter, so that no visible pollutants remain.

Finally the waste water has been subject to strong UV-light from fluorescent pipes to kill off infectious bacteria. The last step is crutial when ensuring that the effluent water quality complies with the requirements for bathing waters.

Destroys cell membranes

Explains COWI project manager Karsten Arnbjerg: "By passing the waste water under UV lamps - a special type of fluorescent pipe – the cell membranes of harmful micro-organisms are effectively destroyed. If the treatment plant functions as planned, it will have a positive impact on both the environment and human health due to an improved water quality."

Large quantities of waste water discharged
At present, waste water from north Copenhagen and parts of the suburbs of Gladsaxe and Gentofte ends up in a central location in the Copenhagen suburb of Hellerup, from where it is pumped to the municipal sewage treatment plant.

But when it rains, large quantities of untreated combined sewage are discharged into the sea – and finding storage for this excess water is both costly and difficult. But the new method is able to cleanse 500 litres of water per second - more than the average family uses in a day.

COWI is participating in a project group together with the water companies and water boards of Århus, Odense and Copenhagen. The project group will discuss the results of the pilot project in Copenhagen and the results from two other pilot plants situated in Odense and Århus, respectively. The three pilot plants combined cover three typical overflow discharge situations common in the EU.


Published: 16.01.2004


Facts  
The pilot projects are initiated following the adoption of the EU’s Water Framework Directive, which requires all counties to adopt an integrated plan of action for groundwater and inland and coastal waters. The pilot projects helps to establish cost-effective solutions to the requirements of the Water Framework Directive.

Copenhagen Energy, Odense Water Company and Århus City Council, together with the Environmental Protection Agency of Copenhagen and the counties of Funen and Århus, have been awarded with a grant from the EU-programme LIFE-environment totalling €1.8 million from the LIFE support programme. The Danish Environmental Protection Agency is also providing funding for the project. The entire project budget including ancillary works exceeds € 6.5 million. The results will be published on the Internet at www.cowiprojects.dk/lotwater.

In Copenhagen the project forms part of a bigger plan to improve the quality of coastal water in and around Svanemøllebugten, Copenhagen. In Odense the project aims to improve the environmental state of the River Odense, one of the biggest waterways in Denmark, while in Århus the aim is to improve the water quality in Århus Bay and also in Silistria Brook, Højbjerg. The project is scheduled for completion in 2006.