Behavior of nanoscale titanium dioxide in laboratory wastewater treatment plants according to OECD 303 A

•Fate and effect assessment of P25 TiO2 nanoparticles in laboratory sewage treatment plants.•Biodegradation and nitrification was not affected by TiO2.•Only 3–4% of the added TiO2 was found in the effluent.•OECD 303 A guideline applicable for nanoparticles. The fate assessment of nanomaterials in municipal sewage treatment plants (STP) is a crucial step for their environmental risk assessment and may be assessed by monitoring full scale STP, dosage to medium scale pilot STP or by laboratory testing. For regulatory purposes preferably standardised test protocols such as the OECD guidelines for testing of chemicals should be used. However, these test protocols have not yet been specifically designed for nanoparticles. Therefore, the fate and behavior of a TiO2 nanomaterial (P25, average hydrodynamic diameter 95%) was retained in the sewage sludge and only 3–4% was found in the effluent. No effect of the TiO2 nanomaterials on the biodegradation or nitrification was observed.