Role of DOM’s Metal-Binding Capacity during AMD Treatment in Passive Bioreactors

摘要

Passive bioreactors have proved effective for acid mine drainage (AMD) treatment. They rely on sulphate-reducing bacteria, which require available organic carbon. Additionally, dissolved organic matter (DOM) has a strong capacity to bind and co-transport metals. Process efficiency is, therefore, related to selection of suitable substrates. DOM reactivity and DOM-metal complexes releasing from potential substrates were evaluated toward four generic metals in AMD (Cd~(2+), Ni~(2+), Fe~(2+), and Cu~(2+)), based on fluorescence quenching. DOM showed the highest reactivity toward Fe but a limited number of sorption sites, whereas DOM-Cd~(2+) complexes exhibited very low fluorescence quenching. The mixture of substrates respected the scale of reported stability of metal organic matter interactions (Cu~(2+) > Ni~(2+) > Fe~(2+)). Overall, after reaching steady-state, limited concentration of DOM-metal complexes was released into the treated water during bioreactors operation, in agreement with theoretical predictions based on geochemical modeling. The fluorescence quenching technique is, therefore, recommended for substrate selection.