Fate of engineered Nanoparticles in Municipal Wastewater Treatment PLants
Norbert Kreuzinger norbkreu(at)iwag.tuwien.ac.at
Nanomaterials are used in large amounts in cosmetics, textiles, varnishes, and polishing agents and are emitted from households via wastewater discharges. Due to their specific properties nanomaterials may influence biotransformation processes in wastewater treatment plants and may enter the environment via treated wastewater in the case they are not retained. The study investigated the effect of the nanoforms of silver (Ag), ceriumdioxide (CeO2), titaniumdioxide (TiO2), and fullerenes on the biological processes in wastewater treatment, their preferential partitioning behaviour into liquid or solid phase as well as the removal potential of municipal wastewater treatment plants. The short and long term effects of nanoparticles on the performance of biological processes were monitored in laboratory-scale wastewater treatment reactors. The experiments were run with and without the addition of well-defined, synthetic nanoparticles. For the acute inhibition tests comparatively high concentrations of nano Ag, nano CeO2, nano TiO2 and C60-fullerenes were added, whereas for the chronic inhibition tests the concentrations were lowered to a more realistic level. In summary, the nanoparticles did not show any effect on the biological processes in the lab-scale sewage treatment, neither on carbon respiration nor on nitrification. The continuous tests also proved that the synthetic nanoparticles adsorb on the activated sludge rather than stay dispersed in the liquid phase. The adsorption behaviour of the sludge was confirmed in batch tests with synthetic nanoparticles. Overall, more than 90 % of the nanoparticles were retained in the sludge. For an insight into the exposure of municipal wastewater treatment plants to C60- and C70-fullerenes, silver, cerium and titanium, five different plants were sampled. The samples comprised the influent to the wastewater treatment plant, treated effluent, and activated sludge. In none of the samples fullerenes were detected, probably due to yet only minor use of fullerenes in consumer products. The mass balances of total Ag, Ce, and Ti substantiate that these elements are present in wastewater and are successfully removed by adsorption on the sludge. Work sponsored by the national research program NANO Environment, Health and Safety programme, project “NanoDESTINARA”.