RESUMO
In this paper, the treatment of real groundwater samples contaminated with gasoline components, such as benzene, toluene, ethylbenzene, and xylene (BTEX), methyl tert-butyl ether (MTBE), tert-butyl alcohol (TBA), and other gasoline constituents in terms of total petroleum hydrocarbons as gasoline (TPHg) by an ozone/UV process was investigated. The treatment was conducted in a semi-batch reactor under different experimental conditions by varying ozone gas dosage and incident UV light intensity. The groundwater samples contained BTEX compounds, MTBE, TBA, and TPHg in the ranges of 5-10000, 3000-5500, 80-1400, and 2400-20000 microgl(-1), respectively. The ozone/UV process was very effective compared to ozonation in the removal of the gasoline components from the groundwater samples. For the various gasoline constituents, more than 99% removal efficiency was achieved for the ozone/UV process and the removal efficiency for ozonation was as low as 27%. The net ozone consumed per mol of organic carbon (from BTEX, MTBE, and TBA) oxidized varied in the range of 5-60 for different types of groundwater samples treated by the ozone/UV process. In ozonation experiments, it was observed that the presence of sufficient amount of iron in groundwater samples improved the removal of BTEX, MTBE, TBA, and TPHg.
Assuntos
Carcinógenos Ambientais/isolamento & purificação , Gasolina , Ozônio/química , Raios Ultravioleta , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Benzeno/química , Benzeno/isolamento & purificação , Derivados de Benzeno/química , Derivados de Benzeno/isolamento & purificação , Carcinógenos Ambientais/química , Éteres Metílicos/química , Éteres Metílicos/isolamento & purificação , Tolueno/química , Tolueno/isolamento & purificação , Poluentes Químicos da Água/química , Xilenos/química , Xilenos/isolamento & purificação , terc-Butil Álcool/química , terc-Butil Álcool/isolamento & purificaçãoRESUMO
A kinetic model that describes the removal of organic pollutants by an ozone/UV process is described. Oxalic acid, which reacts with a very low rate constant with ozone and relatively high rate constant with hydroxyl radical (OH*), was used as the probe chemical to model the process. The model was verified by experimental data on concentrations of oxalic acid and hydrogen peroxide (H202) under various experimental conditions, i.e., ozone gas dosage, UV light intensity, and varying oxalic acid concentrations.
Assuntos
Modelos Químicos , Ácido Oxálico/química , Ozônio/química , Raios Ultravioleta , Poluentes Químicos da Água/análise , Poluição da Água/prevenção & controle , Peróxido de Hidrogênio/análise , Cinética , Ácido Oxálico/análiseRESUMO
The objective of this study is to assess the enhancement in biodegradation of dichlorodiethyl ether (DCDE) by ozonation and Fenton treatment. Acclimated and non-acclimated sludge cultures were used to test the biodegradability of the preoxidized DCDE solutions by three different tests: Short-term and long-term respirometry through continuous monitoring of oxygen consumption, and the mid-term test in which the amount of remaining organic matter was measured by TOC and COD tests. These tests were applied to solutions of DCDE preoxidized at the levels of 25%, 50%, 75%, and 100%. The results indicated that the biodegradability of oxidized DCDE solutions improved substantially compared to non-oxidized solutions. Fenton-treated DCDE exhibited toxicity to microorganisms under long-term exposure. Higher levels of preoxidation of DCDE led to mineralization of larger amounts of organic matter during subsequent biodegradation. There was no significant difference in the rate of biodegradation of oxidized products by either acclimated or non-acclimated bacteria.