Igal Gozlan

Removal of pharmaceuticals using combination of UV/H2O2/O3 advanced oxidation process

Water and wastewater effluents contain a vast range of pharmaceutical chemicals. The present study aims to determine the potential of the advanced oxidation technology UV/H(2)O(2)/O(3) and its sub-processes (i.e. UV, UV/H(2)O(2), UV/O(3), O(3) and H(2)O(2)/O(3)) for the degradation of the antibiotics ciprofloxacin (CIP) and trimethoprim (TMP), and the antineoplastic drug cyclophosphamide (CPD) from water. Creating AOP conditions improved in most cases the degradation rate of the target compounds (compared with O(3) and UV alone). H(2)O(2) concentration was found to be an important parameter in the UV/H(2)O(2) and H(2)O(2)/O(3) sub-processes, acting as (•)OH initiator as well as (•)OH scavenger. Out of the examined processes, O(3) had the highest degradation rate for TMP and H(2)O(2)/O(3) showed highest degradation rate for CIP and CPD. The electrical energy consumption for both CIP and CPD, as calculated using the E(EO) parameter, was in the following order: UV > UV/O(3) > UV/H(2)O(2)/O(3) > O(3) > H(2)O(2)/O(3). Whereas for TMP O(3) was shown to be the most electrical energy efficient. Twelve degradation byproducts were identified following direct UV photolysis of CIP.

Detection of amoxicillin-diketopiperazine-2', 5' in wastewater samples.

The short half-life of aminopenicillin antibiotics in the aquatic environment put to the challenge the detection of their degradation products among environmental hydro-chemists. In a quest to study the occurrence of a new emerging micro-pollutant in the aquatic environment we attempted this by analyzing samples from a wastewater treatment plant for a major degradation product of amoxicillin (i.e., amoxicillin-diketopiperazine-2′, 5′) using a high-performance liquid chromatography technique coupled with tandem mass spectrometry method. ADP was repeatedly detected in all wastewater and effluent samples (18) from which it was extracted. To the best of our knowledge, this is the first study that evidently proves the occurrence of the chemically stable form of AMX, its Diketopiperazine-2′, 5′, in wastewater and effluent samples. Furthermore, penicillins are known to cause most allergic drug reactions. There is a risk that residues of hypersensitivity-inducing drugs, such as penicillins and their degradation products, may elicit allergic reactions in human consumers of water and food of animal origin.

Investigation of an amoxicillin oxidative degradation product formed under controlled environmental conditions

Amoxicillin (AMX) is a widely used penicillin-type antibiotic, and its presence in the environment has been widely investigated. The formation and structure of an oxidised degradation product (DP) of AMX are described in the present work. The experiments were carried out in buffer solution (pH7.5) containing AMX at a concentration of 100mgmL � 1 , with and without acid and in field secondary effluent. The DP, AMX-S-oxide (sulfoxide), was consistently obtained only under sunlight irradiation and was significantly augmented by the addition of humic acid (5mgL � 1 ) and mainly in field secondary effluent, which acts as a natural photo-sensitiser. The structure of the AMX-S-oxide DP was determinedbyanLC-MStechniqueusingamobilephaseofdeuteratedandnon-deuteratedsolvents.A 1 HNMRspectrum was obtained for the pure compound isolated by preparative HPLC. Further confirmation of the AMX-S-oxide structure wasachievedbycomparisonofitsUVspectrumwiththoseofthetwooxidationproducts,AMX-S-oxideandhydroxylated AMX, obtained by the ozonolysis of AMX.

Photodegradation of sulphadimethoxine in water by medium pressure uv lamp

The photodegradation rate of sulphadimethoxine (SMT) in water was studied under polychromatic UV light, in a bench scale apparatus. SMT photolysis was carried out at pH levels of 2.5, 6.5 and 10 to study the impact of acid base properties on the degradation of SMT. The highest SMT photolysis fluence based rate was found at pH=2.5 (k=7.22x10(-4) cm2/mJ) and the lowest rate at pH=10 (k=4.72x10(-4) cm2/mJ), thus the reaction rate decreases with an increase in pH between pH values of 2.5-10. Results indicated that direct photolysis is not satisfactory for degradation of SMT by polychromatic UV lamp as a fluence of approximately 7,000 mJ/cm2 is needed to break down 99% of SMT at pH 6.5. The photodegradation products of SMT were studied at various pH values. Photodegradation of SMT results in dissimilar relative amounts of intermediates formed at different pH values which may exert a photon demand and impact on SMT photodegradation rate.

Identification, Mechanisms and Kinetics of Macrolide DegradationProduct Formation under Controlled Environmental Conditions

Erythromycin, azithromycin, clarithromycin and roxithromycin are antibiotics belonging to the widely used macrolide group. Their presence in the environment has been much investigated, despite the rapid degradation of Erythromycin to its spiroketal degradation product. In this study, the formation of macrolide degradation products was investigated in various aqueous solutions, each containing 100 μg/mL of the respective macrolide, under controlled artificial conditions: three phosphate buffer solutions (pH 5, pH 7 and pH 8.5), and a buffer solution at pH 7 with the addition of humic acids. Two solutions from natural sources were also examined: secondary effluent and tap water. The obtained degradation products were identified by their HRMS and NMR spectra (for Erythromycin-spiroketal, obtained from pure compounds isolated by preparative HPLC) as: N-oxide, N-desmethyl and N-didesmethyl forms of all examined macrolides. These degradation products were obtained only under irradiation by sunlight, while the Erythromycin-H2O degradation products were also obtained in the shade. The secondary effluent was the most significant medium for achieving macrolide degradation products. According the degradation product’s t1/2 values obtained in the secondary effluent, the azithromycin was most rapidly degraded (23 hours). Furthermore, results suggested that the degradation process was activated by sunlight irradiation energy, and that the degradation mechanism started with the transfer of an electron from the amine group to O2 to produce the radical ions RMe2N·+ and O2 ·- as intermediates and production of the N-oxide and N-desmethyl macrolide degradation products. The kinetics of macrolide degradation was calculated as a first-order reaction.

Formation and degradation of N-oxide venlafaxine during ozonation and biological post-treatment

While ozonation is considered an efficient treatment to eliminate trace organic compounds (TrOCs) from secondary wastewater effluents, the presence and persistence of transformation products (TPs) resulting from ozonation of TrOCs is a major concern that should be assessed prior to effluent discharge to the environment. Venlafaxine (VLX), an environmentally relevant tertiary amine-containing TrOC, was chosen as the model for this study. TP analysis confirmed that the lone electron pair of the non-protonated amine are the predominant site of oxidant attack, and therefore strongly affected by pH value and VLX speciation. N-oxide VLX (NOV), the primary ozone-induced TP, was formed and degraded simultaneously during ozonation of VLX-containing secondary effluent and reached a maximum yield of 0.44 to 0.85 (NOV-to-VLX0 ratio), depending on pH and hydroxyl (OH) radical presence. Rate constants for the reaction of NOV with ozone (3.1×102M-1s-1) and OH radicals (5.3×109M-1s-1) were determined. A simple kinetic model was developed to fit the kinetics of formation and degradation of NOV during ozonation in secondary effluents, based on a known ozone-reaction kinetic equation. The biodegradability of NOV (degradation rate of 39%) was significantly lower than that of the parent compound (VLX, 92%) after 71days, as evaluated by modified Zahn-Wellens tests, suggesting that N-oxide products are not better removed than the parent compound in a simulated biological post-treatment, which may even result in partial reformation of the parent compound. Lessons learned from this study were supported by a pilot-scale demonstration at the Shafdan wastewater-treatment plant, confirming the presence of NOV after ozonation and its persistence in biological post-treatment. Removal of such persistent TP will require higher dosages or promotion of OH-radicals during ozonation. Nevertheless, further assessment of the toxicity of persistent TPs relative to the parent compound is needed for complete evaluation of concerned TPs.