Økologisk byfornyelse og spildevandsrensning, 59 – Demonstrationsprojekt i fuldskala for rensning af gråt spildevand

Demonstrationsprojekt i fuldskala for rensning af gråt spildevand

Summary and conclusions

This report presents the evaluation of the project “Demonstration plant for treatment of grey wastewater” financed by the Danish Environmental Protection Agency within the framework of “Action plan for handling rainwater and grey wastewater”.

A full-scale plant for treatment of grey wastewater, collected from bathrooms was tested. The aim was to reuse the treated water for flushing toilets when the quality of the water was acceptable. The treatment plant consisted of two sand filters with aeration of filters and treated water.

Analysis of the treated water concluded: The treated grey water from the plant could not be used for domestic use. This is the conclusion from the report published by the Danish Environmental Protection Agency: “Developing a method for characterisation of grey wastewater” made by Environment & Resources DTU, Technical University of Denmark.

There is no economic benefit with the current water prices and sewage fees. The yearly expenses incl. depreciation of plant costs is 22.000 DKK for 17 households. That is 1.300 DKK per household. The yearly benefit of recycled water is estimated to 13.000 DKK, that is 765 DKK per household.

It could be considered to calculate sustainability and use of resources in a longer perspective.

The testing of the plant shows that it demands engagement from the households if these are to maintain and supervise the plant. Due to hygienic and aesthetic reasons not all will accept handling sewage and sludge.

10 student projects at Environment & Resources DTU, Technical University of Denmark have been completed in the test period.

Suggestions for additional experiments:

Optimising the plant by changing flow, time, aeration etc.

If the optimising of the plant does not reduce the number of microorganisms in the treated water it should be considered to use disinfections to the water by a recognized method.

Also the problem with aeration should be solved, that is a suitable compressor must be found.