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This paper comprises several assays aiming to identify the basis for the bioremediation of mine-impacted water (MIW). To do so, the conditions for build anoxic microcosms for treating this effluent were varied, containing MIW, and a source of chitin, to biostimulate sulfate-reducing bacteria (SRB). The chitin sources were: commercial chitin (CHIT) and shrimp shell (SS), which in addition to chitin, contains CaCO3, and proteins in its composition. The CHIT assays were not successful in sulfate-reduction, even when the pH was increased with CaCO3. However, in all SS assays the SRB development was successful (85% sulfate removal for assay 3), including the metal-free (MF-SS) assay (75% for assay 5). High-throughput sequencing analysis revealed the structure of bacterial community in the SS assay: the most abundant genera were Clostridium and Klebsiella, both fermentative and chitinase producers; a few SRB from the genera Desulfovibrio and Desulfosporosinus were also detected. In the MF-SS assay, Desulfovibrio genuswas detected but Comamonas was dominant. It could be deduced that SS is a suitable substrate for SRB development, but CHIT is not. The sulfate-reduction process was provided by the cooperation between fermentative/chitinase-producer bacteria together with SRB, which leads to efficient MIW treatment, removing sulfate and metallic ions.

Among the Advanced Oxidative Processes (AOPs) applied in the degradation of toxic and resistant organic compounds such as dyes, the heterogeneous photo-Fenton process stands out, once it has high discoloration efficiency and operational simplicity. Given that, this study evaluated the efficiency of the heterogeneous photo-Fenton process in real textile wastewater treatment using chitosan beads as a solid catalyst. Laboratory-scale beads production and tests were carried out to monitor a photochemical reactor equipped with a mercury bulb of 125 W. Samples were collected at different reaction times, equal to 15, 30, 45, 60, 75, 90, and 105 min. The H2O2 concentration applied was 400 mg L−1. The chitosan beads weighed 2 g and were coated with iron, presenting an average diameter of approximately 4 mm. The results presented 91.92 % of effluent discoloration. It was possible to verify the process efficiency without iron precipitation when working with pH values above 6. Furthermore, the determination of other parameters behaviors, such as color, aromatic compounds, dissolved and total solids, as well as toxicity, was accomplished.