Removal of Pollutants from an AMD from a Coal Mine by Neutralization/Precipitation Followed by “In Vivo” Biosorption Step with the Microalgae Scenedesmus sp.

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.

Cultivation of Microalgae (Scenedesmus sp.) Using Coal Mining Wastewater and Separation via Coagulation/Flocculation and Dissolved Air Flotation (DAF)

“…However, the high ash content is notable, which is at the maximum threshold of that found in algae [39]. This is possibly due to the assimilation of inorganic components from the mine water [12,40]. If the values are normalized to only organic components, as demonstrated in many studies, the composition becomes 15.1% total lipids, 34% proteins, and 50.9% carbohydrates.…”

“…The treated water is clear and some ionic species are suitable as a source of essential nutrients for algae growth, such as Ca 2+ , Zn 2+ , Mn 2+ , and SO 4 −2 [7,10], although the addition of other nutrients may be necessary. In a previous study [12], the algae Scenedesmus sp. was grown in treated acid mine drainage from coal mining.…”

“…A noteworthy initiative involves the use of pre-treated mining water for promoting microalgae growth. This innovative approach offers benefits, including the potential production of materials for biofuel generation and the removal of residual pollutants that may persist after conventional acid mine drainage treatment processes [6][7][8][9][10][11][12][13]. In particular, Chlorella and Scenedesmus are microalgae of choice for metal removal, but it is necessary to develop strategic multidisciplinary approaches to develop commercially viable technologies [14].…”

Biotechnology of Microorganisms from Coal Environments: From Environmental Remediation to Energy Production

“…Over the last few decades, algae-based systems have shown promising prospects for removing various heavy metals from AMD. Algae function as “hyper-accumulators” (when an active mechanism is involved) and “hyper-adsorbents” (through passive mechanisms), with a pronounced selectivity for different elements [ 211 , 212 ]. Microalgal species such as Spirulina sp., Chlorella , Chlamydomonas , Scenedesmus , Cladophora , and Oscillatoria are widely employed for heavy metal removal [ 212 , 213 , 214 , 215 ].…”

Editorial for Special Issue “Pollutants in Acid Mine Drainage”

“…The papers by Zawierucha et al [30], Kato et al [31], Ryskie et al [32], and Santos et al [33] were related to diverse processes and tools for the treatment of AMD. Zawierucha et al [30] showed a novel approach based on the selectivity of elements of environmental concern, especially arsenic.…”