- Engineering nanoparticles (ENPs) are an integral part of consumer products. Released to atmosphere or disposed to sewage, the ENPs quickly penetrate to surface and ground water sources. An absence of a dedicated ENP-retaining water treatment strategy imposes a potential health threat on drinking water consumers. The threat is gearing up an upgrade of treatment systems towards membrane filtration that provides a better barrier to ENPs penetration at higher energy costs. The current study compares the energy demand of granular and membrane filtrations, with a retention efficiency of inorganic and organic ENPs. Dedicated experiments with gold and silver nanoparticles, dyed viruses, protein, polysaccharide, and plasmid DNA showed that the energy demand increases from slow to river bank to rapid sand filtration, and to membrane ultrafiltration (UF). The UF alone consumes in average two times more energy than the entire coagulation-flocculation-sedimentation-sand filtration tray. The differences in retention efficiency however are much less pronounced. The traditional retention tray requires 0.4–0.45 kWh per m3 of effluent (kWh/m3) to provide between 90 and 99% (1 and 2 logs) ENPs retention. One kWh/m3 in average is needed to secure the retention of 99.9% (3 log) ENPs by UF.