Re-use our sewer trash – closed



Waternet’s goal is to be climate-neutral by 2020. The re-use of residual streams that are released from the production of drinking water or the cleaning of waste water is one of the main targets.

Currently, calcite used for softening drinking water is treated in such a way that it can be used again for the same purpose – but it can also be used as a material for the production of glass, paper, plastic, carpets or cosmetics.

In Amsterdam, struvite is extracted from wastewater, which is then used as raw material in the fertiliser industry. Screened material (cellulose) is recovered from the influent and used as paving fibres (afdruipremmer) in asphalt.

Annually, about 2.500 tons of coarse waste from the bar screens are taken out of the influent of the two waste water treatment plants in Amsterdam. Coarse waste are objects that people flush through the sewer or that otherwise end up there and that accumulate behind the grates on wastewater treatment plants. Think of leaves, twigs, bags, sanitary towels, condoms, telephones, toys etc. Currently, this coarse waste is incinerated in accordance with laws and regulations.

In addition, about 1.000 tons of a mixture of fat, grease and fibres are annually taken out of the primary settling tanks of the two waste water treatment plants in Amsterdam.

Currently, coarse waste from the bar screens is incinerated. We want better use of this waste than incineration with energy recovery. Prevention is not achievable but re-use is our goal!

The fat/grease/fibre mixture is currently composted. What else can we do with this?


The Challenge:

Find an innovative solution to re-use coarse waste and fat/grease/fibre from residual streams



  • Your solution should consider hygiene and legal implications.


Issued by: Waternet

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