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Many water and wastewater treatment plants (WWTPs) are fitted with a UV system that provides post treatment disinfection before the water is released to receiving water. This paper presents a study on expected removal for the pharmaceutical venlafaxine (VEN) in a typical UV unit at a municipal WWTP with analysis of removal rates of an advanced oxidation process using UV irradiation with injection of H2O2. The study is supported by bench scale degradation experiments on VEN. Results demonstrated that UV can completely degrade VEN, but the addition of H2O2 increased pseudo first order rate constant by up to 2.5 times. Extrapolations of the lab data indicated that removal rates of VEN at the UV disinfection unit of a typical municipal WWTP are approximately 0.4% at standard operating conditions. With the addition of 10 mg/L of H2O2, degradation of VEN can be increased by ten times over existing UV treatment. By studying the impact of adjusting parameters such as UV intensity, UV dosage, and H2O2 dosage, a framework is set to allow researchers and engineers to move forward with developing UV/H2O2 systems that meet their future design needs for pharmaceutical removal. [ABSTRACT FROM AUTHOR]

This study evaluates the influence of UV dose on degradation of carbamazepine (CBZ) in wastewater under UV-C (λ = 254 nm) photolysis with and without H2O2. The rate of degradation of CBZ exhibited a direct dependence on the intensity of incident UV irradiation as the rate of degradation was observed to increase linearly (R2 = 0.98) with UV intensity between 1.67 and 8.95 × 1017 photons/s. More than 95% of the CBZ that spiked in wastewater rapidly degraded within 4 min with a first-order rate constant of 1.2 min−1 for an optimum H2O2 dose of 100 mg/L. Bench-scale continuous flow reactor experiments also showed that CBZ degraded with first-order kinetics at a rate constant of 1.02 min−1. The kinetic parameters obtained for a continuous bench-scale reactor were in good agreement with the relationships developed through batch experiments with only a marginal deviation of ± 6.5%. The relationship between UV intensity and CBZ degradation rate obtained in this study was extrapolated to the UV disinfection unit of a wastewater treatment plant to predict possible degradation of CBZ during UV disinfection. The addition of 100 mg/L of H2O2 to the secondary-treated effluent entering the UV disinfection unit is predicted to achieve over 60% degradation of CBZ. Abbreviations: CBZ carbamazepine; AOPs advanced oxidation processes; UV ultraviolet radiation; UV-C ultraviolet C (λ = 254 nm) radiation; NZVI non-zerovalent iron; WWTP wastewater treatment plant; HPLC high-performance liquid chromatography [ABSTRACT FROM AUTHOR]

This article presents the results of an investigation into the function of UV in a photo-assisted ozonation process for treatment of carbamazepine (CBZ) in treated domestic wastewaters. Experiments were conducted on synthetic spiked water and secondary treated municipal wastewater. Degradation of CBZ was studied for various combination of O3 dosage ranging from 4.8 to 14.4 mg/h and UV intensities with varying intensity and wavelength (UVC: λ = 254 nm and UVA: 352 nm). In synthetic spiked water, CBZ was degraded to below detectable limits within 0.5 min for ozone dose of 14.4 mg/h. The rate of degradation of CBZ increased exponentially with increase in ozone dose following a zero-order rate at each dose level. The degradation rate of CBZ in wastewater was slower compared to deionized water (DI) water by 40-75% for various doses of ozone, presumably due to the presence of organic matter remaining in treated wastewater. Optimal UV intensities for UVA and UVC were obtained as 0.62 and 0.82 mW/cm2 for all doses of ozone in synthetic spiked water samples and UV intensities beyond this resulted in lower rates of degradation of CBZ. For photo-assisted ozonation with ozone doses of 9.6 and 14.4 mg/L, rate constants were two times higher for UVA irradiations as compared to UVC irradiation. Contrary to observations in DI water, experiments in wastewater showed increase in rate of degradation with higher UV intensities. Overall, photo-assisted ozonation was found to be appropriate for both water and wastewater treatment by exploiting the benefit of direct attack of ozone and of produced .OH radicals to yield a greater extent of mineralization of CBZ. [ABSTRACT FROM AUTHOR]

A study on dechlorination of PCB138 in transformer oil (TO) and 2-propanol (IPA) using 254 nm ultraviolet (UV) light as well as dye sensitized visible light has been conducted. Studies on dechlorination of polychlorinated biphenyls (PCBs) in TO using visible light in the presence of methylene blue (MB) and triethylamine (TEA) (providing a ‘photocatalytic’ cycle) in both deaerated and aerated conditions have been conducted to determine effects of TO, MB and TEA on reaction rates. The results show that photolytic methods are effective in treating PCBs in TO, and that the oil plays a limited adverse role. Under UV irradiation, PCB 138 can be >99% dechlorinated in the presence 0.06% (w/w) TO in IPA within 1 h with a rate constant of 0.0853 min−1, while 47% of PCB138 can be dechlorinated in 92.1% (w/w) TO in IPA within 2 h with a rate constant of 0.0051 min−1. In the ‘photocatalytic’ system, 94% reduction of PCB 138 was achieved within 30 min with a rate constant of 0.0968 min−1 when the solvent was 60.70% (w/w) TO in IPA, while 71% dechlorination of PCB138 was achieved within 30 min with a rate constant of 0.0382 min−1 when 81.62% (w/w) TO was present. In treatment of 30–73 ppm PCBs in TO, the optimal concentration of MB and TEA were found to be 0.5 g/L and 58.08 g/L respectively. Because of quenching by oxygen, deaeration of the solution is necessary for an efficient reaction. The photocatalytic system is especially adapted for treating lower concentration of PCBs in TO. [ABSTRACT FROM AUTHOR]

Laurentide humic acid has been titrated with paraquat and with selected divalent metal ions. In some cases, the humic acid was spiked with one cation before titration with another one. Several equivalence points were determined for the binding of the divalent cations, including paraquat. Three equivalence points agreed well with values predicted from the acidic properties of the humic acid. Eight independent experiments gave nine replicate values for an equivalence point that corresponds to 79.2 mole % of the total pairs of carboxyl groups. It is postulated that this represents a large molecular weight or structural fraction of the humic acid. The remaining 20.8 mole % can either bind one divalent cation to two carboxylate anions or bind one divalent cation to one carboxylate anion, with another anion providing for charge balance. Aggregation ‐ disaggregation and dissolution ‐precipitation phenomena may determine which case prevails, and they in turn are sensitive to the chemical compositions of samples. It should be possible to develop analytical chemical methods for characterizing the stoichiometric properties of humic acid samples. [ABSTRACT FROM PUBLISHER]

The solution phase complexing equilibria of atrazine by fulvic acid at 25°C±1.° have been investigated over the pH range of 1.3 to 6.0. Experiments with 0.1MKC1 and chelated Cu(II) are compared with those without metal ions. The use of a fulvic acid having calibrated acidic and Cu(II) chelation properties has made it possible to obtain stoicheometricly “exact”; chemical information. This is correlated with previous hydrolysis kinetics work. It is concluded that atrazine is hydrogen bonded in a labile equilibrium, to an identifiable set of protonated carboxyl groups, which act as Brönsted acid catalysts for hydrolysis. 0.1M KC1 changes (1‐αA), the degree of protonation of the carboxyl groups, without otherwise affecting the atrazine complexing. Cu(II) chelation both reduces and weakens the complexing through a combination of carboxyl group blocking, and fulvic acid aggregation. Simple equations are presented for predictive calculations. [ABSTRACT FROM PUBLISHER]