Biological filtration of treated waste water by Daphnia: an alternative for technical filtration, or an addition?

Several years of research on the island of Texel proofed that Daphnia magna are very well capable to remove faecal coli bacteria effectively from treated wastewater by biological filtration. The Daphnia population, mainly Daphnia magna, is maintained by activated sludge particles and loose bacteria from the treated waste water. Because of the filtration by Daphnia the ponds fed with treated waste water do no turn green by algae, as expected. A combined research project on mesocosm scale (m 3 -scale) has been started on three sites (STP Horstermeer and STP Grou in the Netherlands, plus STP Empuriabrava in Spain) to study this phenomena. In Horstermeer the research aims mainly on comparing the biological filtration by Daphnia with technical filtration like sand filtration and membrane filtration. The experiments in Grou and Empuriabrava run parallel to full-scale Daphnia ponds. Keywords algae, biological filtration, constructed wetland, Daphnia, disinfection, food chains, ponds, suspended solids, treated waste wastewater