Abstract
This work evaluates the benefits of a complementary treatment step of acid mine drainage (AMD) using the algae Scenedesmus sp. in terms of algae biomass production, residual metal removal, and the toxicity of the discharged water. Conventional treatment by neutralization/precipitation of an AMD from a coal mine in Brazil was conducted with Ca(OH)2 at pH 8.7. Algal growth studies were performed in the treated AMD, with and without a nutrient supply. The raw effluent and treatments were compared in terms of residual concentration of metals and sulfate, conductivity, and toxicity with the Allium cepa and Daphnia magna test organisms. The results show that the conventional treatment allowed a major metal removal, reduction in the conductivity, and good indices in the toxicological parameters evaluated. The biosorption with in vivo microalgae improved the quality of the effluent for residual metals. No significant toxicity was observed to Allium cepa in all treatments performed, while the Daphnia magna test indicated a reduction in toxicity after the biosorption step. It was concluded that algae growth can be carried out in treated mine waters, providing algae biomass and helping to achieve the standards for water discharge.
Highlights
Active chemical treatment by neutralization has been widely applied by the coal mining industry to prevent the damages caused by acid mine drainage
The sample of acid mine drainage (AMD) used in this work was provided by a coal mining company located in the municipality of Figueira, northeast of the State of Paraná, Brazil (23◦ 490 15” S; 50◦ 250 50” W)
The results show that microalgae may be suitable candidates for simultaneous remediation and sustainable biomass production in aqueous environments fed by treated acid mine drainage—at least from those of the coal mining industry
Summary
Active chemical treatment by neutralization has been widely applied by the coal mining industry to prevent the damages caused by acid mine drainage. Considering the acidic mine water treatment plants in Brazil, the most commonly used neutralizing reagent is hydrated lime, raising the pH to 8.7. Calcium chemicals are preferred since they are cheaper and allow the partial removal of the amount of sulfate ions present in the wastewater [5]. This practice was validated by recent studies applying the reagents Ca(OH) and NaOH at pH 7.0 and 8.7 to treat acid mine drainage from a coal mine [6,7]. Additional treatment steps can be applied for AMD control when
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