Degradation of drugs in water with advanced oxidation processes and ozone.

The aim of this paper is to assess the degradation of a mixture of ibuprofen and clofibric acid and to study the mineralization and toxicity following ozone treatment. To this end, a comparison is presented of the experimental results obtained from ozone treatment using atmospheric air as the feed gas (Experiment I, [O3] = 15 gN/m(3)), with and without addition of H2O2, and those obtained under the same conditions but using concentrated oxygen as the feed gas, obtained by pressure swing adsorption technology (Experiment II, [O3] = 200 gN/m(3)). All tests were conducted using a pilot scale reactor. Under (Experiment II) conditions, degradation exceeded 99% and up to 60% mineralization was achieved for initial compound concentrations, and hydraulic retention time was reduced by 75% compared to (Experiment I). The results of toxicity tests show through increasing the production of ozone gas in (Experiment II), toxicity was eliminated at initial study concentrations of ≤1 mg/l for all treatment times studied.

Molecular structure and biodegradation kinetics of linear alkylbenzene sulphonates in sea water.

The present paper describes the results of the application of the biodegradation test proposed by the United States Environmental Protection Agency (USEPA) "Biodegradability in sea water" Office of Prevention, Pesticides, and Toxic Substances (OPPTS) 835.3160, to Linear Alkylbenzene Sulphonate (LAS), the synthetic surfactant with the highest consumption volume on a world-wide basis. High performance liquid chromatography (HPLC) has been employed for the separation and quantification of the different homologues and isomers of the surfactant. Water from the Bay of Cádiz (South-West of the Iberian peninsula) has been used as test medium. The results indicate how both lag and t (50) time shows a significant linear relationship with the length of the alkyl chain of the homologue; the effect of this is that the homologues of longer chain length not only begin to degrade first but also degrade at a faster rate. Regarding the isomeric composition, it is observed that as the percentage of biodegradation increases, there is an increase in the proportion of internal isomers, in comparison with the isomeric relationships of the original test substance.

Biodegradation kinetics of linear alkylbenzene sulphonates in sea water.

This article reports the primary biodegradation kinetics of linear alkylbenzene sulphonates (LAS) in sea water from the Bay of Cadiz (South West of the Iberian Peninsula). The authors used the biodegradation test guideline proposed by the Office of Prevention, Pesticides, and Toxic Substances of the United States Environmental Protection Agency; 835.3160 "Biodegradability in sea water" in its shake flask variant. High performance liquid chromatography (HPLC) has been employed for the analysis of the surfactant material. The surfactant shows a primary biodegradation kinetic in accordance with a logistic model, the kinetic parameters t (50) and lag time were calculated by means of a easy quantitative procedure introduced. Mean values of 6.15 +/- 0.45 and 6.67 +/- 0.6 days were obtained for t (50) and lag time, respectively. These results indicate that although LAS has a high primary biodegradation rate in sea water, it biodegrades slower than in similar tests conducted in river water.

Enhancement of aerobic microbial degradation of polychlorinated biphenyl in soil microcosms.

This article reports the results of various biodegradation experiments on polychlorinated biphenyl (PCB)-contaminated sandy soil employing a mixed culture of acclimatized bacteria. Following the optimization of different variables without chemical pretreatment, the elimination rate achieved of Aroclor 1242 in slurry-phase reactors was 61% after four months of treatment, with the presence of biphenyl as cosubstrate being the most important factor affecting PCB biodegradation. The biodegradation occurred as a first-order process, and it proved most effective in respect to dichlorinated biphenyls (100% removal), followed by trichlorinated (92%) and tetrachlorinated biphenyls (24%). The results also showed that the degradability of PCBs in soil may be enhanced by an advanced oxidation pretreatment (Fenton reaction), producing almost 100% elimination of PCBs at the end of the integrated chemical-biological process and 72% mineralization of the intermediates generated during the chemical pretreatment.