Traitement de polissage par marais épurateur du drainage minier acide

Affiche présentée dans le cadre du Colloque de l'ARC, «La culture de la recherche au collégial», dans le cadre du 82e Congrès de l'Acfas, Université Concordia, Montréal, le 14 mai 2014.Les résidus miniers représentent une source de danger potentiel pour l'environnement, en particulier lorsque ces déchets contiennent des minéraux sulfureux qui peuvent s'oxyder et générer du drainage minier acide (DMA). Ce dernier est caractérisé par un pH faible et des concentrations en sulfates et métaux dissous élevées. Les traitements biologiques constituent une solution moins coûteuse par rapport aux traitements chimiques, en plus de présenter plusieurs avantages dont des taux élevés d’enlèvement des métaux, une réduction du pH, de faibles coûts d’exploitation et une consommation minimale d’énergie. La capacité des marais filtrants à traiter un DMA chargé en fer à l’étape de polissage a été étudiée. Les systèmes consistaient en des marais artificiels à écoulement vertical et horizontal de 0,052 m3, remplis de deux différents substrats et plantés avec des quenouilles (Typha latifolia). Ils étaient alimentés pour traiter 1,5 mL/min d’un DMA ayant une concentration moyenne de 38,0 mg/L de fer, 2,6 mg/L de manganèse, 0,4 mg/L de nickel et 0,9 mg/L de zinc à un pH moyen de 4,2. Après traitement, le pH moyen à l’effluent était de 8,0 pour les marais verticaux et de 7,6 pour les horizontaux. Le taux d’enlèvement du fer et du zinc était respectivement de 95 et 96 % pour les marais à écoulement verticaux et de 87 et 94 % pour les horizontaux. Le traitement du nickel et du manganèse était négligeable

Clostridia Initiate Heavy Metal Bioremoval in Mixed Sulfidogenic Cultures

Sulfate reducing bacteria (SRB) are widely used for attenuating heavy metal pollution by means of sulfide generation. Due to their low metal tolerance, several SRB species depend on associated bacteria in mixed cultures to cope with metal-induced stress. Yet the identity of the SRB protecting bacteria is largely unknown. We aimed to identify these associated bacteria and their potential role in two highly metal-resistant mixed SRB cultures by comparing bacterial community composition and SRB activity between these cultures and two sensitive ones. The SRB composition in the resistant and sensitive consortia was similar. However, whereas the SRB in the sensitive cultures were strongly inhibited by a mixture of copper, zinc, and iron, no influence of these metals was detected on SRB growth and activity in the resistant cultures. In the latter, a Gram-positive population mostly assigned to Clostridium spp.initiated heavy metal bioremoval based on sulfide generation from components of the medium (mainly sulfite) but not from sulfate. After metal levels were lowered by the Clostridium spp. populations, SRB started sulfate reduction and raised the pH of the medium. The combination of sulfite reducing Clostridium spp. with SRB may improve green technologies for removal of heavy metals

Short-Term And Long-Term Bioreactors For Acid Mine Drainage Treatment

Passive biological treatment of acid mine drainage (AMD) relies on sulfate-reducing bacteria (SRB) supported by a biodegradable organic carbon source. However, long-term treatment performance can be limited by the degradation rates of organic carbon available to SRB, and by low metal stability in spent reactive mixtures. The first part of this study focused on characterization of six natural organic materials and their short-term effectiveness in sulfate-reduction and metal removal from synthetic AMD. In the second part, long-term performance and metal precipitates in the reactive mixtures were assessed. Maple wood chips, sphagnum peat moss, leaf compost, conifer compost, poultry manure and conifer sawdust were analyzed in terms of their carbon and nitrogen content, as well as their easily available substances content (EAS). Single substrates and substrate mixtures were tested in a 70-day batch experiment (2-L reactors) and in an extended batch study for up to 350 days. Geochemical modeling and scanning electron microscopy (SEM) was used to assess the minerals present in the solid phase. The highest EAS content and the lowest C/N ratio suggested poultry manure would be the best substrate. Nevertheless, the lowest efficiency was found in the poultry manure reactor, whereas the mixture of three organic materials was the most effective. After 350 days, the mixture of organic carbon sources was still efficient for AMD treatment. SEM analysis of the solid phase indicated the presence of iron sulfides. Substrate characterization provided insight on organic carbon availability but did not elucidate their ability to promote sulfate-reduction and metal removal. Further research is needed to accurately predict long-term carbon availability and to assess the metal precipitates in spent reactive mixtures