WP1 Restoration of Contaminated Sites
Ballroom E, Level 4
2:10 PM - 5:30 AM, Wednesday, 12 November 2003
Chair: Barnthouse, Larry ,
(414) Advances in Biotreatment of Acid Mine Drainage and Biorecovery of Metals: 2. Membrane.
Tabak, H1, Govind, R2, 1 USEPA, NRMRL, Cincinnati, OH, USA2 Univeristy of Cincinnati, Cincinnati, OH, USA
ABSTRACT- Several biotreatment techniques for sulfate reduction utilizing sulfate reducing bacteria (SRB) have been proposed in the past, however few of them have been practically applied to treat sulfate containing acid mine drainage (AMD).This paper deals with development of an innovative polypropylene hollow fiber membrane bioreactor system for the treatment of acid mine water from the Berkeley Pit, Butte, Montana, using hydrogen consuming SRB biofilms. The advantages of using the membrane bioreactor over the conventional tall liquid phase sparged gas bioreactor systems are: large microporous membrane surface to the liquid phase resulting in high mass fluxes; formation of hydrogen sulfide outside the membrane. preventing the mixing with the pressurized hydrogen gas inside the membrane; there is no gas recycle and thus no requirement of gas recycle compressor; membrane surface is suitable for immobilization of active SRB, resulting in the formation of biofilms. thus preventing washout problems associated with suspended culture reactors and resulting in higher sulfate bioconversion; and lower operating costs in membrane bioreactors, eliminating gas recompression and gas recycle costs. Information is provided on sulfate reduction rate studies and on biokinetic tests with suspended SRB in the anaerobic digester sludge and sediment SRB source master culture reactors and with SRB biofilms in the bench-scale membrane bioreactors. Biokinetic parameters were determined using biokinetic models for the master culture and membrane bioreactor systems. Data are presented on the effect of acid mine water sulfate loading at 25. 50, 75 and 100 ml/min in scale-up SRB membrane units, under varied temperatures (25C, 35C and 40C) to determine an optimum sulfate conversion rate for an effective AMD biotreatment. Pilot-scale studies have provided data on the effect of flow rates of acid mine water (MGD) and varied inlet sulfate concentrations in the influents on the resultant outlet sulfate concentration in the effluents and on the number of SRB membrane modules needed for the desired sulfate conversion for those systems. The pilot-scale data indicate that the SRB membrane bioreactor systems can be applied toward field-scale biotreatment of AMD and for recovery of high purity metals and an agriculturally usable water.
Key words: microbial sulfate reduction, acid mine drainage biotreatment