With their increasing use, nanoparticles will become concentrated in urban effluents in the future. Both adequate monitoring methods and water treatment technologies will be necessary to assess and avoid consumer exposure. This paper reports results in these two challenging areas for both organic and inorganic nanoparticles. Treatment experiments indicate that lamellar settling is better adapted than dissolved air flotation for SiO2 nanoparticles removal. The use of 120 mg/L of Aqualenc coagulant without flocculant addition allows 99% removal to be achieved for an initial concentration of 1 g/L. On the other hand, the dissolved air flotation process implemented under the usual industrial conditions does not permit removal of SiO2 nanoparticles. In this case SiO2 removal occurs only by settling in the flocculator tank. Application of a high resolution liquid chromatography/mass spectrometry (LC/MS) technique to a small selection of treated urban effluents indicates that C60 fullerenes are not yet widely distributed in effluents; however non-point sources cannot be entirely ruled out.