Chitosan in the treatment of mine spoil rainwater - An approach to protect the aquatic biota

Abstract

The mining industry suppresses vegetation, exposing large soil areas in its ordinary operation. Water pollution and turbidity are caused by the carrying of solids, mainly colloidal particles, to the watercourses due to the effect of rainfall events. Therefore, the discharge of those effluents will lead to failure with watercourse quality parameters. Thus, there is a need to treat drainages (rainwaters) from the mining industry. However, using common coagulants and flocculants can result in acute or chronic ecotoxicity for aquatic biota. In this scenario, this research aimed to evaluate using a natural coagulant, the biopolymer Chitosan, to remove turbidity from mining industry spoiled water through bio-coagulation. The ecotoxicity of the natural coagulant was compared to the commonly used coagulants. For this purpose, we used synthetic rainwater (SRW) from the dispersion of fine (colloidal) particles in natural waters. Materials (water and soil) were collected in the mining area's sumps (sedimentation basins). The turbidity of the produced SRW ranged from between 500 and 4000 NTU. Jar Tests using Chitosan (CTS), polyaluminum chloride (PAC®12), and Superfloc®N100 variable doses were carried out to compare the effects of the coagulating/flocculating agents on the SRW turbidity reduction. The obtained results demonstrated the efficiency of CHS on turbidity reduction. The results were encouraging for low turbidity samples (<1000 NTU), making it possible to meet the limit parameters recommended by the Brazilian legislation. In addition, it was possible to conclude both CHS and the effluents treated with this coagulant have lower toxicity to aquatic biota than the combination of PAC®12 and Superfloc®N100.