Assessing the effects of metal mining effluents on freshwater ecosystems using biofilm as an ecological indicator: Comparison between nanofiltration and nanofiltration with electrocoagulation treatment technologies

Abstract

Abandoned mines cause serious environmental damage to their surroundings with considerable impacts on freshwater ecosystems. These impacts occur mainly due to the uncontrolled discharge of polluted effluents, which may contain high concentrations of heavy metals. Currently, no real solution exists for this important environmental problem, leaving a legacy of global pollution. This study aimed to assess the impact of a metal mining effluent from an abandoned mine on freshwater ecosystems, using aquatic biofilms as an ecological indicator. At the same time, the efficiency of different innovative treatment technologies in reducing the ecological impacts caused by mining effluents was evaluated, consisting of nanofiltration and nanofiltration combined with electrocoagulation. To do that, aquatic biofilms obtained from a pristine stream, were exposed, under microcosms conditions, to a metal mining effluent, untreated or treated by the innovative treatment technologies and responses were compared with unexposed biofilm which served as control. The structural and functional responses of the biofilm were measured with throughout time. Biofilms that were exposed to the untreated mining effluent showed significant differences respect to the rest of treatments and the control, particularly exhibiting inhibitory effects on photosynthetic efficiency just after 24 hours of exposure and a progressive shift of the photosynthetic community composition throughout the exposure period. The treatment technologies significantly reduced the ecological impact caused by the metal mining effluent. However, metal bioaccumulation in biofilm revealed a potential long-term impact. These observations evidenced the biofilm as a useful ecological indicator to assess the ecological impact caused by metal mining effluents on freshwaters and the efficiency of different treatment technologies to reduce it.

Effects of an hypersaline effluent from an abandoned potash mine on freshwater biofilm and diatom communities

“…Each microcosm contained 15 stream cobbles (previously scraped and autoclaved) used as substrates for natural biofilm colonization. The microcosms were filled with 3 L of artificial water, which was prepared to mimic a pristine stream as described in Ylla et al (2009) by dissolving pure salts in distilled water, and creating the same chemical composition described in Vendrell-Puigmitja et al (2020). A submersible pump (EDEN 105, Eden Water Paradise, Italy) was installed in each microcosm to ensure the recirculation of water.…”

“…BenthoTorch portable fluorimeter probe (bbe Moldaenke, Schwentinenta, DK) as defined in Vendrell-Puigmitja et al (2020). Biofilms of the corresponding microcosm were then scraped using a toothbrush and suspended in water from the corresponding microcosm.…”

Effects of the interaction between nutrient concentration and DIN:SRP ratio on geosmin production by freshwater biofilms

“…From this river, a natural biofilm suspension was obtained by scrapping several cobbles randomly selected along a 50m river stretch located at the water collection point of the water drinking company Aigües de Vic (X440478; Y4648779 UTM31N), and 15 mL of this suspension was inoculated in each microcosm to promote biofilm colonization. During the colonization period (three weeks), a new inoculum was added after each water renewal to favor biofilm settlement in the microcosms (Vendrell-Puigmitja et al, 2020).…”

Instream barriers contribute to population isolation of a small‐bodied, benthic, headwater‐specialist fish (Percidae)

“…The coal mines located in the headwaters of Red Bird River contribute to the high conductivity observed throughout the river's mainstem (U.S. EPA, 2011b), and our results indicate high conductivity is the leading cause of genetic isolation among proximate tributary populations in this system (Figure 1a). Newer reclamation practices that involve nanofiltration of mining effluent reduce conductivity levels (Kemak et al., 2018; Vendrell‐Puigmitja et al., 2020). Conducting such reclamation efforts at these mined sites could help reduce the conductivity in the mainstem, potentially leading to an increase in population connectivity.…”