Bavo De Witte

Ozonation and advanced oxidation by the peroxone process of ciprofloxacin in water

A bubble reactor was used for ozonation of the antibiotic ciprofloxacin. Effects of process parameters ozone inlet concentration, ciprofloxacin concentration, temperature, pH and H(2)O(2) concentration were tested. Desethylene ciprofloxacin was identified, based on HPLC-MS analysis, as one of the degradation products. Formation of desethylene ciprofloxacin was highly dependent on pH, with the highest concentration measured at pH 10. Radical scavengers t-butanol and parachlorobenzoic acid were added in order to gain mechanistic understanding. Radical species other than hydroxyl radicals were suggested to occur at acidic pH which can explain fast ciprofloxacin ozonation at pH 3.

Influence of pH on the sonolysis of ciprofloxacin: biodegradability, ecotoxicity and antibiotic activity of its degradation products.

The presence of antibiotics in the aquatic environment has raised concerns due to the potential risk for the emergence or persistence of antibiotic resistance. Antibiotics are often poorly degraded in conventional wastewater treatment plants. In this study, sonolysis at 520 kHz and 92 W L(-1) was used for the degradation of the fluoroquinolone antibiotic ciprofloxacin. In a first experiment at pH 7, 57% of the ciprofloxacin (15 mg L(-1)) was degraded after 120 min of ultrasonic irradiation at 25 degrees C. pH proved to be an important parameter determining the degradation rate, since the pseudo first order degradation constant increased almost fourfold when comparing treatment at pH 7 (0.0058 min(-1)) and pH 10 (0.0069 min(-1)) with that at pH 3 (0.021 min(-1)). This effect can be attributed to the degree of protonation of the ciprofloxacin molecule. The BOD/COD ratio of the solutions, which is a measure for their biodegradability, increased from 0.06 to 0.60, 0.17, and 0.18 after 120 min of irradiation depending on the pH (3, 7, and 10, respectively). The solution treated at pH 3 can even be considered readily biodegradable (BOD/COD>0.4). The antibiotic activity against Escherichia coli (G-) and Bacillus coagulans (G+) of the treated solutions also reduced after sonolysis. The highest decrease was again found when irradiated at pH 3. In contrast, ecotoxicity of the solutions to the alga Pseudokirchneriella subcapitata increased 3- to 10-fold after 20 min of treatment, suggesting the formation of toxic degradation products. The toxicity slowly diminished during further treatment.

Ciprofloxacin ozonation in hospital wastewater treatment plant effluent: Effect of pH and H2O2

The ozonation of ciprofloxacin was studied in hospital wastewater treatment plant effluent with focus on parent compound degradation, degradation product identification and residual antibacterial activity. Before ozonation, ciprofloxacin sorption on suspended solids was tested as a function of temperature (10.0-27.5 degrees C) and pH (3, 7 and 10). Temperature did not significantly affect ciprofloxacin sorption while sorption was highest at pH 7 (logK(d)=4.7) compared to pH 3 (logK(d)=4.3) and 10 (logK(d)=3.9) (n=3). Ozonation was slowest at pH 7 with ciprofloxacin half life times of 29 min, compared to 19 and 27 min at pH 10 and 3, respectively. Addition of 10-1000 microM H(2)O(2) increased ciprofloxacin half life times up to 38 min, probably influenced by competition with H(2)O(2) for ozone as well as radical species. Ciprofloxacin ozonation products were identical as previously detected during ciprofloxacin ozonation in deionized water and revealed strong pH dependence. Residual antibacterial activity was measured by agar diffusion tests. For Pseudomonas fluorescens and Escherichia coli, reduction of antibacterial activity was related to the parent compound degradation, while degradation products indicated to be the main compounds with respect to the antibacterial activity against Bacillus coagulans.

Advanced Oxidation of Pharmaceuticals: Chemical Analysis and Biological Assessment of Degradation Products

Pharmaceuticals are often hardly biodegradable and physicochemical technologies are required for their removal from water. Degradation by advanced oxidation processes is intensively studied in last years. However, analytical methodologies to detect AOP-induced pharmaceutical degradation products and to assess their biological effects have not been reviewed until now. The authors aim to fill up this literature gap. The main goal is to bring forward a critical overview of the state-of-the-art of analytical techniques and the information they provide to clearly distinct 5 identification levels that are applicable for micropollutant degradation products in general. Next, literature data dealing with the application of identification tools is systematically summarized. Literature sources were mainly published from 2005 to 2008.

A qualitative screening and quantitative measurement of organic contaminants on different types of marine plastic debris.

Chemical compounds present on plastic were characterised on different types of plastic litter and beached pellets, using a general GC-MS screening method. A variety of plastic related compounds, such as building blocks, antioxidants, additives and degradation products, were identified next to diverse environmental pollutants and biofilm compounds. A validated method for the analysis of PAHs and PCBs on beached pellets at the Belgian Coast, showed concentrations of ∑ 16 EPA-PAHs of 1076-3007 ng g(-1) plastic, while the concentrations of ∑ 7 OSPAR-PCBs ranged from 31 to 236 ng g(-1) plastic. The wide variety of plastic compounds retrieved in the general screening showed the importance of plastic as a potential source of contaminants and their degradation products.

Chemical analyses of dredged spoil disposal sites at the Belgian part of the North Sea.

The chemical status of five dredged spoil disposal sites in the Belgian Part of the North Sea is evaluated. A linear mixed-effect model was applied to PCB, PAH and heavy metal data from 2005 to 2014. No decrease in PCB concentrations was found, with even an increase at two disposal sites. Hg/AL ratios increased with 62% at one disposal site (BR&WS2) from 2005 to 2006 to 2013-2014. Cu and Zn concentrations increased at two disposal sites. Additional harbour sampling suggests that the latter is possibly linked to antifouling paints. Based on OSPAR environmental assessment criteria, the current chemical status of the sites suggests no chronic effect of dredged spoil disposal. However, increasing time trend data for PCB, Hg, Cu and Zn demonstrate the importance of monitoring to identify adverse trends.

The effect of crude protein reduction on performance and nitrogen metabolism in piglets (four to nine weeks of age) fed two dietary lysine levels1

Lowering the CP level in piglet diets reduces the risk of post-weaning diarrhea and N excretion to the environment. The question remains at what point CP becomes limiting. An experiment was designed with 2 standardized ileal digestible (SID) Lys levels (10 and 11 g) and 6 CP levels (140, 150, 160, 170, 180, 190 g/kg) in a 2 x 6 factorial design (with 6 pens of 6 animals each per treatment). Linear and quadratic (QP) mixed models of performance in function of CP were fitted to study the effect of Lys and CP and their interaction. To determine optima, QP models and broken line models with linear (BLL) or quadratic (BLQ) ascending portions were fitted through the data. It was hypothesized 1) that the response to a decreasing digestible CP level could be described with broken line models and 2) that the breakpoint of these models is dependent on the dietary SID Lys level. Decreasing the CP level decreased ADG (P < 0.001). For G:F, the effect of decreasing CP level depended on the SID Lys level (P of the interaction = 0.028 in the linear model and P = 0.002 in the QP model). According to the BLL model, with 11 g SID Lys in the diet, G:F started to decline with CP levels below 176 g CP (SID Lys:apparent total tract digestible (ATTD) CP = 0.077), and with 10 g SID Lys, CP levels below 165 g/kg (SID Lys:ATTD CP = 0.075) depressed performance. Serum creatinine levels showed a linear decrease with increasing Lys:CP levels (P < 0.001). Across both SID Lys levels, when fitting a BLL model, minimal serum urea levels were reached at a Lys:CP ratio of 0.064. This seems to be the point where CP and not Lys limits muscle deposition. The small difference in breakpoint between serum urea level and performance suggests that the composition of nonessential AA may be also at stake. The effect of decreasing CP level depends on SID Lys and using a maximal SID Lys:CP ratio may be useful for optimizing the AA profile of dietary CP. When the Lys:CP ratio exceeds 0.064 (SID Lys:ATTD CP above 0.079), protein and not individual AA limits growth in most piglets between 4 and 9 weeks of age.