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Thesis for Master of Science
Isabel Cristina Serra Pedro "Degradation
of acid orange 7 in a vertical flow constructed wetland planted with Phragmites
sp." ABSTRACT This work concerns the treatment of effluents from the textile industry, attempting to evaluate the applicability of artificial wetlands to the treatment of effluents containing Azo dyes, and to determine some of the parameters necessary for the design of an industrial installation. A continuous subsurface vertical flow pilot reed bed planted with Phragmites sp. was used to carry out the treatment of an aqueous solution of acid orange 7, AO-7, selected as synthetic influent. The experimental work was performed within a pilot bed at IST in Lisbon, which is around 9 years old, withich has a surface area of 0.96 m2, a height of 0.87 m and a sandy-clay soil, planted with Phragmites sp., fed continuously and operated at a constant flooding rate of 21%. The influence of hydraulic loading, HL, in the AO-7 removal efficiency was studied for influent hydraulic loads of 28, 40, 53 and 108 Lm-2d-1 at a constant AO-7 concentration of 127 mg/L. The influence of the AO-7 mass loading was studied at a constants of 30 Lm-2d-1, for average inlet concentrations of AO-7 of 171, 262, 425, and 1003 mg/L.The experiments were performed during wintertime and system was daily monitored by quantification of colour, COD, TOC, pH, sulfates and nitrates and HPLC analysis of AO-7 and sulphanilic acid. In all the experiments, removal efficiencies of the different parameters achieved were higher than 95%. The detection and quantification of sulphanilic acid, nitrates and sulfate in the outlet led to the conclusion that an effective aerobic mineralisation of AO-7.From experimental results it is possible to degrade AO-7 in a vertical constructed wetland at a mass load of 30 gAO-7m-2d-1 and efficiencies higher than the effluent discharge EU directive, for varies atmospheric conditions with air temperatures from 4 to 24ºC. Keywords: Textiles effluents; Azo dye; Acid orange 7;Colour removal; Biodegradation of azo dyes; Constructed wetlands; Sub-surface vertical flow
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