Yeon Jung

Removal of amoxicillin by UV and UV/H2O2 processes

The degradation of the β-lactam antibiotic amoxicillin (AM) treated with direct UV-C and UV/H(2)O(2) photolytic processes was investigated in the present study. In addition, the antibacterial activity of the solution treated by UV/H(2)O(2) advanced oxidation was compared with AM solution treated with ozone. The degradation rate of amoxicillin in both processes fitted pseudo first-order kinetics, and the rates increased up to six fold with increasing H(2)O(2) addition at 10mM H(2)O(2) compared to direct photolysis. However, low mineralization was achieved in both processes, showing a maximum of 50% TOC removal with UV/H(2)O(2) after a reaction time of 80min (UV dose: 3.8×10(-3)EinsteinL(-1)) with the addition of 10mM H(2)O(2). The transformation products formed during the degradation of amoxicillin in the UV and UV/H(2)O(2) processes were identified by LC-IT-TOF analysis. In addition, microbial growth inhibition bioassays were performed to determine any residual antibacterial activity from potential photoproducts remaining in the treated solutions. An increase of the antibacterial activity in the UV/H(2)O(2) treated samples was observed compared to the untreated sample in a time-based comparison. However, the UV/H(2)O(2) process effectively eliminated any antibacterial activity from AM and its intermediate photoproducts at 20min of contact time with a 10mM H(2)O(2) dose after the complete elimination of AM, even though the UV/H(2)O(2) advanced oxidation process led to bioactive photoproducts.

An investigation of the formation of chlorate and perchlorate during electrolysis using Pt/Ti electrodes: the effects of pH and reactive oxygen species and the results of kinetic studies.

The characteristics of chlorate (ClO(3)(-)) and perchlorate (ClO(4)(-)) formation were studied during the electrolysis of water containing chloride ions (Cl(-)). The experiments were performed using an undivided Pt/Ti plate electrode under different pH conditions (pH 3.6, 5.5, 7.2, 8.0 and 9.0). ClO(3)(-) and ClO(4)(-) were formed during electrolysis in proportion to the Cl(-) concentration. The generation rates of ClO(3)(-) and ClO(4)(-) under acidic conditions (pH 3.6 and 5.5) were lower than in basic pH conditions (pH 7.2, 8.0 and 9.0). However, the pH of the solution did not influence the conversion of ClO(3)(-) to ClO(4)(-). The effects of intermediately formed oxidants on the production of ClO(3)(-) and ClO(4)(-) were observed using sodium thiosulfate (Na(2)S(2)O(3)) as the active chlorine scavenger and tertiary butyl alcohol (t-BuOH) as the hydroxyl radical (OH) scavenger. The results revealed that electrolysis reactions that involved active chlorine contributed dominantly to ClO(3)(-) production. The direct oxidation reaction rate of Cl(-) to ClO(3)(-) was 13%. The OH species that were intermediately formed during electrolysis were also found to significantly affect ClO(3)(-) and ClO(4)(-) production. The key formation pathways of ClO(3)(-) and ClO(4)(-) were studied using kinetic model development.

pH Effect on Ozonation of Ampicillin: Kinetic Study and Toxicity Assessment

Ampicillin (AP) is a penicillin-type antibiotic and one of the most widely used bacteriostatic antibiotics in human and veterinary medicine. A kinetic study was performed under different pH conditions (5, 7.2, and 9) to determine the degradation efficiency of AP by ozonation. The second-order rate constants for the direct reaction of AP with ozone were measured to be 2.2 ˜5.4×105 M−1s−1 under the pH conditions tested. The rate constants were greater at higher pH. The potential toxicity of the AP intermediates formed after ozonation under the various pH conditions were examined using a bioluminescence assay on Vibrio fischeri species. The biodegradability of the AP degraded products was also determined by measuring the BOD5/COD of the ozonated samples under the different pH conditions. A lower biodegradability and acute toxicity was observed at the lowest pH (pH 5). These results suggest that higher pH conditions are needed for the removal of AP by ozonation in order to mitigate the residual toxicity that can remain even after complete removal of the parent compound by ozonation.

Evaluation of disinfection efficacy and chemical formation using MPUV ballast water treatment system (GloEn-PatrolTM)

This study was undertaken to evaluate the efficacy of inactivation of several indigenous marine species and the formation of oxidants and other by-products using medium-pressure ultraviolet (MPUV) ballast water treatment. The ballast water treatment system (BWTS) used in this study was composed of filtration modules as a pretreatment process, followed by a UV irradiation process equipped with a polychromatic MPUV lamp. The experiments were performed on seawater (Busan,>32 PSU) and brackish water (Nakdong River, 20–22 PSU) with flow rates of 50 and 250 m3/h. The disinfection efficacy of the system was evaluated using indigenous species (>50 μ m and 10–50 μ m) and surrogate microorganisms (E. coli and Enterococci group). The test results successfully met the D-2 regulation of the IMO (International Marine Organization). In addition, oxidants, such as H2O2, total residual oxidants (TRO) and OH radicals, and potential halogenated by-products, such as haloacetic acids, trihalomethanes and total organic halides, that had potentially formed after MPUV treatment, were measured. In conclusion, the ballast water treatment system employing the MPUV physical process not only effectively eliminated indigenous species in ballast water but also generated no harmful by-products.

The degradation of diethyl phthalate (DEP) during ozonation: oxidation by-products study

The degradation of diethyl phthalate (DEP) in an aqueous solution during ozonation was investigated by identifying the oxidation intermediates using GC-MS. The experiments were carried out in semi-batch mode with a 1.5 mg l(-1)-min ozone dose. The proposed degradation pathways were divided into hydrolysis of the aliphatic chain (pathway (A)) and hydroxylation resulting from OH attack in the aromatic ring (pathway (B)). With increasing ozone dose, the aromatic ring of DEP was opened and acidic compounds, such as malonic acid, succinic acid and glutaric acid were formed. In addition, the ozonation of DEP for 18 min induced hydrogen peroxide (H(2)O(2)) generation at levels six times higher than pure water. Of the intermediates indentified, phthalic acid (PA) and phthalic anhydride (PAH) enhanced the degradation of DEP by promoting ozone decomposition.