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ABSTRACT:
Acid Orange 24 (AO24) dye was degraded in a trickling biofilter packed with peat and wood chips and inoculated with biomass from a petrochemical industry wastewater system. Different operating strategies were tested; in the first stage, two biofilters were operated independently-one non-aerated biofilter (passive) and the other with aeration-subsequently, the systems were operated serially, and effluent from the non-aerated biofilter was fed to the biofilter with aeration. This treatment train was used to test three different filtration velocities-0.141, 0.282, and 0.423 m/d. The results show that, when operating the systems with a dye charge of 0.035 kg AO24 m^sup 2^/d and treating the effluent in a single step, good removal efficiencies of AO24 (95 and 89%), COD (63 and 53%), and acute toxicity (63 and 78%) were obtained in both biofilters (with and without air), although mutagenic and potentially carcinogenic intermediary compounds were not removed, because genotoxicity exhibits values higher than 2.0 units for the mutation rate. When using the non-aerated biofilter/aerated biofilter treatment train, it is possible to treat a dye charge 3 times greater (0.106 kg AO24 m^sup 2^/d) and efficiently remove 98% AO24, 76% COD, 100% acute toxicity, and 100% genotoxicity, which indicates that, with this biological system, an advanced degree of biotransformation and mineralization of the azo dye AO24 is achieved. Water Environ. Res., 83, 107 (2011).
KEYWORDS: azo dye removal, AO24 toxicity and genotoxicity, aerated/non-aerated trickling biofilters, byproducts degradation.
doi:10.2175/106143010X12780288627977
Introduction
Dyes are substances that absorb light at a certain wavelength within the region of the visible spectra (between 4000 and 8000 Å), which gives them a certain color. The structural unit that gives color to a dye molecule is the chromophore. In the case of azotype dyes, which represent 70% of the dyes currently used in the world, their chromophore is a molecule: N=N; that is, a double linkage between nitrogenous radicals of aromatic amines (ary lamines), some of which have been reported as being carcinogenic for man (Kadlubar et al., 1992; Tavan et al.,2002). When the double bond of the azo dyes breaks, arylamines are released, and toxicity increases (Shaul et al., 1991). This is why it is important to degrade these intermediary products also.
The AO24 is used widely to color synthetic fibers (nylon), wool,...