Titanium dioxide (TiO2), whose particle size is less than 100 nm, is one of the most widely used nanomaterials. A previous study reported that exposure of TiO2 nanoparticles (nano-TiO2) inhibited the growth of algae, therefore, the adverse effects on aquatic biota are of great concern. Wastewater treatment plants are suspected as significant sources of TiO2 into public water body as it is contained in various consumer products such as cosmetics and pigments. In this study, a wastewater treatment plant in Japan was surveyed to understand the occurrence and behavior of nano-TiO2 during wastewater treatment processes. The survey was conducted on June 14 and 15, 2018. Influent, effluent and five samples from treatment processes were collected every 2 h over a period of 24 h and were composited respectively. An aliquot of each sample was fractionated into nano-phase by a 100 nm PVDF membrane. Ti and five other metals were analyzed by ICP-OES. As a result, total Ti concentration in effluent was 3.14 ?g-Ti/L and overall removal rate was 91.3%. In contrast, nano-TiO2 concentration in effluent was 1.77 ?g-Ti/L and the removal rate was 57.2%. Thus, the study indicates that the removal efficiency of TiO2 may depend on the particle size. |