Using wastewater as a resource

Algenbuizen in de kas

Using wastewater as a resource

Not all wastewater is necessarily 'dirty'. Toilet water can even be used as a clean energy source!


There are many kinds of wastewater, from the water used to flush toilets to the water used in laboratories.  If we use our overloaded sewage system to dispose of all this water, purifying it will take a huge amount of energy. But not all wastewater needs to be purified, and toilet water can even be used as an energy source!


Feces are ‘collected’ in vacuum toilets, fermented and turned into biogas. The residual flow from this process is used as food for algae. Such algae could, for example, be used in agriculture as fertilizer, allowing us to eventually close the biological cycle. On the moment, the algae bioreactor is still in the research phase. Meanwhile, the residual water from the toilet cycle - which has been ‘pre-purified’ by the algae - and the other wastewater streams are separated and led into a helophyte filter. In a helophyte filter or constructed wetland, water plants and micro-organisms ‘eat’ the organic waste, and whatever remains is filtered one last time through various layers of soil. Following the system design, the treated water could rejoin the groundwater. This closes the water cycle, with no need for a sewer. What we would like to find out is if we can put algae ‘on the pill’. I.e. whether we can get them to remove not just nutrients from the water but also medicine residues, pathogens, contraceptives and contaminating metals. This is a worthy research question for NIOO, Wageningen UR and commercial companies.

Wastewater treatment in the NIOO-KNAW building (Dutch)