The aim of the this study was to investigate the ozone dosage required to remove active pharmaceutical ingredients (APIs) from biologically treated wastewater of varying quality, originated from different raw wastewater and wastewater treatment processes. Secondary effluents from six Swedish wastewater treatment plants (WWTP) were spiked with 42 APIs (nominal concentration μg/L) and treated with different O₃ doses (0.5-12.0 mg/L ozone) in bench-scale experiments. In order to compare the sensitivity of APIs in each matrix, the specific dose of ozone required to achieve reduction by one decade of each investigated API (DDO₃) was determined for each effluent by fitting a first order equation to the remaining concentration of API at each applied ozone dose. Ozone dose requirements were found to vary significantly between effluents depending on their matrix characteristics. The specific ozone dose was then normalized to the dissolved organic carbon (DOC) of each effluent. The DDO₃/DOC ratios were comparable for each API between the effluents. 15 of the 42 investigated APIs could be classified as easily degradable (DDO₃/DOC ≤ 0.7), while 19 were moderately degradable (0.7 < DDO₃/DOC ≤ 1.4), and 8 were recalcitrant towards O₃-treatment (DDO₃/DOC >1.4). Furthermore, we predict that a reasonable estimate of the ozone dose required to remove any of the investigated APIs may be attained by multiplying the experimental average DDO₃/DOC obtained with the actual DOC of any effluent.
The catalytic etherification of glycerol with tert-butyl alcohol over a strong acid ion-exchange commercial resin (Amberlyst 15) has been studied. The etherification reactions were carried out in a glass laboratory autoclave reactor with magnetic stirring without solvent at autogenous pressure. Experimental results were obtained at different temperatures (50−80 °C) and using an 8.5 wt % catalyst loading referred to the starting amount of glycerol. Four ethers (two monoethers and two diethers) and isobutylene were identified as the main products of glycerol etherification and tert-butyl alcohol dehydration (secondary reaction), respectively. Two simplified heterogeneus kinetic models are proposed to describe the process performance. The first model lumps the monoethers and diethers into the species M and D, respectively, and includes three reactions and the corresponding kinetic equations. The second model includes all of the species detected and six stoichiometric equations. Kinetic parameters for each kinetic model were estimated by data fitting. Irreversible dehydration of tert-butyl alcohol can be assumed at the operating conditions employed in the present study. Both kinetic models proposed describe the evolution of the system properly, in terms of both the reactant and product distributions with reaction time in the temperature range studied.
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