Effect of calcium ions and anaerobic microbial activity on sedimentation of oil sands tailings

► Tailings ponds originate from bitumen production by surface mining. ► Densification is monitored as the movement of a boundary separating supernatant from the tailings. ► Ca(NO3)2 and lactate gave the most increased rate of tailings densification. ► Calcium ions and microbial activity are needed for optimal tailings densification.