Abstract
(English)
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PHOTOCATALYTIC DEGRADATION OF WATER ORGANIC POLLUTANTS
Biological wastewater treatment is often the most economical process when compared with other treatment options. Nevertheless, industrial effluents are known to contain toxic and/or non-biodegradable organic substances and biological process are not efficient in these cases. Photocacatalytic oxidation processes have been proposed as an attractive alternative for the pretreatment of this kind of wastewater, which can reduce their toxicity, improve their biodegradability and prepare the pretreated wastewater to a biological, low cost, treatment.
This study was conducted to investigate the mineralization of 5-amino-6-methyl-2-benzimidazolone (AMBI), an important biorecalcitrant intermediate in the industrial production of dyes, via a coupled photochemical-biological system.
Photocatalytic (Solar) experiments were carried out at the Plataforma Solar de Almeria (PSA), southern Spain, an ideal place for installing solar plants, as more than 300 days per year can be expected to be sunny, with an average of 3000 sunny hours per year.
Different Photocacatalytic oxidation processes, i.e. the systems light/TiO2/O2 light/TiO2/H2O2, light/Fe3+/H2O2, and light/Fe3+/O2 have been studied and their performances for the Disolved Organic Carbon (DOC) mineralization of the AMBI solution were compared. Between the different evaluated systems by direct sunlight at the PSA, we decide to go further into the study of the iron photo-assisted processes. Although these systems show a slow decay of DOC after a first efficient, but short, period of mineralization, its homogenous character provides, with reasonable limitations, good engineering conditions for coupling theses systems with a complementary biological treatment. The toxicity and biodegradability analyses of the phototreated solutions show that the solution resulting from the photodegradation of AMBI is biologically compatible and its complete mineralization can be performed by biological means.
The field experiments under direct sunlight at PSA clearly show that the solar photocatalytic treatment is a promising technology for the pre-treatment of wastewater containing AMBI. The integration of solar and biological processes at pilot scale appears to be advantageous for achieve the complete mineralization of biorecalcitrant water organic pollutants.
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