A comparative approach to the application of a physico-chemical and advanced oxidation combined system to natural water samples

Natural organic matter removal (NOM) efficiencies of samples from three major drinking water sources (Elmali, Omerli, and Buyukcekmece) of Istanbul were compared using different treatment systems. Enhanced coagulation as a physico-chemical method was applied using ferric chloride and aluminum sulphate as the coagulating agents. Moreover, the application of enhanced coagulation in combination with photocatalytic oxidation using TiO2 was investigated. The efficiency of NOM removal relevant to each treatment step was assessed through DOC removal, UV254 removal, and fluorescence measurements. Irrespective of the treatment applied as enhanced coagulation, photocatalytic oxidation or their combinations, the highest removal efficiency was determined for Elmali followed by Omerli and Buyukcekmece samples both in terms of DOC and UV254. Enhanced alum coagulation leads to significant variation in DOC removals as 44%, 28% and 26% for Elmali, Omerli, and Buyukcekmece water samples, respectively. Upon application of ferric chloride as the coagulant, the DOC removals achieved were found to be slightly higher as compared to alum. Moreover, the combined treatment incorporating photocatalytic oxidation subsequent to alum coagulation leads to 36%, 37%, and 50% of DOC removal for Omerli, Buyukcekmece, and Elmali respectively. The improvement of removal efficiencies in combined treatment systems were scrutinized with an emphasis on induced water properties as supported by the specific fluorescence intensities of the samples

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 o