Treatment of acid mine drainage with anaerobic solid-substrate reactors

Anaerobic solid-substrate reactors were used in laboratory study of acid mine drainage treatment. Parallel systems were run continuously for 23 months, both containing a solid substrate of 2:1 (weight) cow manure and sawdust. One system had cheese whey added with the mine drainage to provide an additional electron donor source to stimulate sulfate-reducing bacteria activity. Effluent pH from the reactor with whey addition was relatively constant at 6.5. Effluent pH from the reactor without whey addition dropped over time from 6.7 to approximately 5.5. Whey addition increased effluent alkalinity [550 to 700 mg/L as calcium carbonate (CaCO3) versus 50 to 300 mg/L as CaCO3] and sulfate removal (98 to 80% versus 60 to 40%). Sulfate removal rate with whey addition decreased over time from 250 to 120 mmol/m(3).d, whereas it decreased from 250 to 40 mmol/m(3).d without whey addition. Whey addition increased removal of dissolved iron (84 versus <0%). dissolved manganese (40 versus 2%), and dissolved zinc (99.7 versus 96.0%) in the second part of the experiment. Copper and cadmium removals were greater than 99%, and arsenic removal was 84% without whey addition and 89% with whey addition. Effluent sulfide concentrations were approximately 1 order of magnitude greater with whey addition. A 63-day period of excessive loading permanently decreased treatment efficiency without whey addition.