Alice L. Petre

Occurrence of emerging pollutants in urban wastewater and their removal through biological treatment followed by ozonation

This work reports a systematic survey of over seventy individual pollutants in a Sewage Treatment Plant (STP) receiving urban wastewater. The compounds include mainly pharmaceuticals and personal care products, as well as some metabolites. The quantification in the ng/L range was performed by Liquid Chromatography-QTRAP-Mass Spectrometry and Gas Chromatography coupled to Mass Spectrometry. The results showed that paraxanthine, caffeine and acetaminophen were the main individual pollutants usually found in concentrations over 20 ppb. N-formyl-4-amino-antipiryne and galaxolide were also detected in the ppb level. A group of compounds including the beta-blockers atenolol, metoprolol and propanolol; the lipid regulators bezafibrate and fenofibric acid; the antibiotics erythromycin, sulfamethoxazole and trimethoprim, the antiinflammatories diclofenac, indomethacin, ketoprofen and mefenamic acid, the antiepileptic carbamazepine and the antiacid omeprazole exhibited removal efficiencies below 20% in the STP treatment. Ozonation with doses lower than 90 microM allowed the removal of many individual pollutants including some of those more refractory to biological treatment. A kinetic model allowed the determination of second order kinetic constants for the ozonation of bezafibrate, cotinine, diuron and metronidazole. The results show that the hydroxyl radical reaction was the major pathway for the oxidative transformation of these compounds.

Application of the combination index (CI)-isobologram equation to study the toxicological interactions of lipid regulators in two aquatic bioluminescent organisms.

Pharmaceuticals in the aquatic environment do not appear singly and usually occur as complex mixtures, whose combined effect may exhibit toxicity to the aquatic biota. We report an environmental application of the combination index (CI)-isobologram equation, a method widely used in pharmacology to study drug interactions, to determine the nature of toxicological interactions of three fibrates toward two aquatic bioluminescent organisms, Vibrio fischeri and the self-luminescent cyanobacterial recombinant strain Anabaena CPB4337. The combination index-isobologram equation method allows computerized quantitation of synergism, additive effect and antagonism. In the Vibrio test, the fibrate combinations showed antagonism at low effect levels that turned into an additive effect or synergism at higher effect levels; by contrast, in the Anabaena test, the fibrate combinations showed a strong synergism at the lowest effect levels and a very strong antagonism at high effect levels. We also evaluated the nature of the interactions of the three fibrates with a real wastewater sample in the cyanobacterial test. We propose that the combination index-isobologram equation method can serve as a useful tool in ecotoxicological assessment.

Ecotoxicological assessment of surfactants in the aquatic environment: combined toxicity of docusate sodium with chlorinated pollutants.

The toxicity of perfluorinated surfactants perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorobutane sulfonate (PFBS) and PF-656 as well as the sulfosuccinate surfactant docusate sodium has been examined using two bioluminescence inhibition assays based on the marine bacterium Vibrio fischeri and the self-luminescent cyanobacterial recombinant strain Anabaena CPB4337. We also determined multigenerational toxicity towards the growth of the algae Pseudokirchneriella subcapitata. With EC(50) values in the 43-75 mg/L range, docusate sodium exhibited a higher toxicity towards the three organisms than PFOS, PFOA, PF-656 and PFBS. We investigated the toxicological interactions of the most toxic surfactant, docusate sodium, with two chlorinated compounds, triclosan and 2,4,6-trichlorophenol (TCP), in their binary and ternary mixtures using the method of the combination index based on the median-effect equation. In general, the binary mixture of the chlorinated compounds triclosan and TCP exhibited antagonism, which was stronger for the growth test using P. subcapitata. Except for the green alga, the binary mixtures of docusate sodium with TCP or triclosan showed synergism at medium to high effect levels; the synergistic behaviour predominating in the ternary mixture and in the three tested species. This result highlights the potential toxicological risk associated with the co-occurrence of this surfactant with other pollutants.

Degradation of caffeine and identification of the transformation products generated by ozonation

The ozonation of caffeine in water was performed at different pH values, including acidic conditions. Kinetic experiments were conducted by adding pulses of a concentrated caffeine solution to ozone saturated water. The results showed a rapid decrease of ozone concentration during the first 15s after injection, followed by a gradual decline at a much slower rate. The data were fitted to a second order kinetic model with rate constants increasing from 0.25 to 1.05 M(-1)s(-1) for pH in the 3-10 range. The initial ozone consumption per mol of ozonated caffeine was greater at high pH values, reflecting a higher ozone decomposition rate. The decomposition of ozone was positively affected by the concentration of caffeine, an effect that could be attributed to the presence of a reaction intermediate from the ozonation of caffeine that behaved as a strong promoter of ozone decomposition. A study of the transformation products identified by liquid chromatography in combination with time-of-flight mass spectrometry was carried out, which permitted a tentative degradation pathway to be proposed and several persistent by-products to be identified at both pH 3 and 8. Most transformation products were the result of the opening of the imidazole ring after breaking caffeines N9C8 double bond.

Coagulation-fenton coupled treatment for ecotoxicity reduction in highly polluted industrial wastewater.

A coupled coagulation-Fenton process was applied for the treatment of cosmetic industry effluents. In a first step, FeSO(4) was used as coagulant and the non-precipitated Fe(2+) remaining in dissolution was used as catalyst in the further Fenton process. In the coagulation process a huge decrease in total organic carbon (TOC) was achieved, but the high concentration of phenol derivatives was not diminished. The decrease in TOC in the coagulation step significantly reduces the amount of H(2)O(2) required in the Fenton process for phenol depletion. The coupled process, using a H(2)O(2) dose of only 2 g l(-1), reduced TOC and total phenol to values lower than 40 and 0.10 mg l(-1), respectively. The short reaction period (less than 15 min) in TOC and phenol degradation bodes well for improving treatment in a continuous regime. The combination of both processes significantly reduced the ecotoxicity of raw effluent and markedly increased its biodegradability, thus allowing easier treatment by the conventional biological units in conventional sewage treatment plants (STPs).

Continuous ozonation treatment of ofloxacin: transformation products, water matrix effect and aquatic toxicity.

The continuous ozonation of the antibiotic ofloxacin (OFX) has been performed using a synthetic water matrix and in a sewage treatment plant (STP) effluent. The aim was to study the effect of the water matrix on the ozonation with particular emphasis on the aquatic toxicity of treated water. OFX was completely removed in both water matrices, although the amount of ozone consumed for its depletion was strongly matrix-dependent. The extent of mineralization was limited and a number of intermediate transformation products (TPs) appeared, twelve of which could be identified. OFX reaction pathway includes the degradation of piperazinyl and quinolone moieties. The further oxidation of TPs gave rise to the formation and accumulation of carboxylic acids, aldehydes, nitrogen-containing organic compounds and inorganic ions. Aquatic toxicity of treated mixtures was assessed using four standard species: the bacteria Vibrio fischeri and Pseudomonas putida as target organisms and the algae Pseudokirchneriella subcapitata and the protozoan Tetrahymena thermophila as non-target organisms. OFX was toxic for the bacteria and the microalgae at the spiked concentration in untreated water. However, the continuous ozonation at the upper operational limit removed its toxic effects. T. thermophila was not affected by OFX, but was sensitive to STP effluent.

A bacterium-based contact assay for evaluating the quality of solid samples – results from an international ring test

The contact assay measuring the inhibition of Arthrobacter globiformis dehydrogenase activity as an endpoint to evaluate the toxicity of solid samples was tested in an international ring-test to validate its performance for ISO standardization (ISO/CD 18187). This work reports the results of the ring-test involving 9 laboratories from six countries. At least 8 valid data sets were obtained for each sample and more than three quarters of the participants attained the validity criteria defined in the standard. The coefficient of variation within (CVr) and between (CVR) laboratories was generally on average <15% and <30% for negative and positive controls, respectively. Regarding solid samples, the laboratories provided a similar ranking of the samples based on their toxicity, despite some variation in the LOEC values. The logarithmic within-lab standard deviation <0.50 for soils and <0.25 for wastes evidenced a good repeatability. The between-lab variability assessed by a CVR <30%, minimum-maximum factor <4 and a reproducibility standard deviation (SDR) <0.13 for a great part of the solid samples, confirmed the test reproducibility. Overall, this assay proved to be robust, sensitive and feasible for routine use towards the quality assessment of soils and wastes.