4. General information on the contribution of some treatment processes

Even if it proves impossible to eliminate all micropollutants from water, some treatment processes are clearly more effective than others in reducing the concentration of a wide range of micropollutants. The Poseidon program (European project, 2005) confirmed that conventional activated sludge plants are generally unable to significantly treat a number of particularly polar or poorly biodegradable residues. However, for biodegradable compounds and/or compounds easily retained by the biomass, biological processes such as activated sludge or biofiltration have shown significant reductions in outgoing concentration [2][60] . Figure