Ceyda Senem Uyguner-Demirel

Leaching potential of nano-scale titanium dioxide in fresh municipal solid waste.

With the rapid development in nanotechnology in recent years, the number of commercially available products containing engineered nanomaterials (ENMs) has increased significantly. It is expected that large fractions of these ENMs will end up in landfills for final disposal. Despite the wide use of ENMs, little data is available on their fate within landfills. This study examined the leaching behavior of nanoscale titanium dioxide (nano-TiO2), one of the mostly used ENMs, in fresh municipal solid wastes (MSWs). Batch reactors containing municipal waste samples were spiked with a range of nano-TiO2 concentrations at different pH and ionic strength conditions. The Ti concentrations in leachate decreased rapidly and reached steady state after about 12-24 h. Results suggest that, for the environmental conditions considered, approximately 3-19% of the added nano-TiO2 remained in leachate. Batch tests conducted with individual synthetically-prepared solid waste components also showed low leaching potential (5.2% for organic waste, 3.3% for glass, 1.7% for both textile and paper and 0.6% for metal), indicating that all components of MSW contributed to the retention of the nano-TiO2 mass within the solid matrix.

Enhanced ozonation of selected pharmaceutical compounds by sonolysis.

In search of new options to achieve removal of pharmaceuticals in the environment, combined ultrasound and ozonation has become a focus of intense investigation for wastewater treatment. In this study, three pharmaceuticals were selected as model compounds for degradation experiments: diclofenac (DCF), sulfamethoxazole (SMX) and carbamazepine (CBZ). Comparison of the degradation rates for both ozonation and combined ultrasound/ozonation treatments was performed on single synthetic solutions as well as on a mixture of the selected pharmaceuticals, under different experimental conditions. For single synthetic solutions, the efficiency removal for ozonation reached 73%, 51% and 59% after 40 min for DCF, SMX and CBZ, respectively. Comparable results were obtained for pharmaceuticals in mixture. However, the combined ultrasound/ozone treatment was found to increase degradation efficiencies for both DCF and SMX single solutions up to 94% and 61%, respectively, whereas lower removal yields, up to 56%, was noted for CBZ. Likewise, when the combined treatment was applied to the mixture, relatively low removal efficiencies was found for CBZ (44%) and 90% degradation yield was achieved for DCF.

An integrated chemical and ecotoxicological assessment for the photocatalytic degradation of vancomycin

The photocatalytic degradation of an antibiotic, vancomycin B hydrochloride (VAN-B), has been investigated in aqueous suspensions of titanium dioxide (TiO2) by monitoring the change in its concentration as well as the production of ammonia and chlorides as a function of irradiation time. The removal of 50 mg L−1 VAN-B solution yields maximum concentrations of 2.45 and 2.53 mg N-NH3 L−1 after 120 min of photocatalytic oxidation using 0.1 and 0.2 g TiO2 L−1, respectively. When 0.2 g TiO2 L−1 were applied up to 87% of the stoichiometric amount of chloride was reached within 120 min of irradiation, corresponding to 0.087 mmol L−1. A set of bioassays (Daphnia magna, Pseudokirchneriella subcapitata and Ceriodaphnia dubia) was performed to evaluate the potential detoxification of VAN-B and its by-products of oxidation under chronic and acute tests. The toxicity of the treated VAN-B samples varied during the oxidation, due to the formation of some intermediate products more toxic than VAN-B. Despite almost total removal of VAN-B that was achieved within 120 min of irradiation, a significant increase in toxicity was observed in chronic tests proving that the chronic assays are more appropriate than acute ones to detect the impact of by-products formed during the photocatalytic degradation of antibiotics.

Presence, Behavior and Fate of Engineered Nanomaterials in Municipal Solid Waste Landfills

As a result of extensive use of engineered nanomaterials (ENMs) in consumer products, significant amounts of ENMs are eventually released to the environment and find their way to wastewater treatment plants, incineration plants and landfills. Recent concerns about the potential impacts of these materials on the environment and human health, have diverted researchers’ interest to investigate the behaviour of inorganic, metallic/metal oxide ENMs in conventional activated sludge wastewater treatment and anaerobic sewage sludge digestion systems. However, related information about the presence and fate of such ENMs during waste stabilization in municipal solid waste (MSW) landfills which remains a widely used method of solid waste management, is scarce in literature. Therefore, in this paper, recent information about the detection methods and fate of the most commonly used metal oxide ENMs such as TiO2, ZnO, Ag and SiO2 in MSW landfills was revealed. The complexity of the factors influencing ENMs retention and transport mechanisms was discussed. Future research needs relating to the fate of ENMs in MSW were also identified.