Use of Cellulosic Substrates for the Microbial Treatment of Acid Mine Drainage

Abstract

A mixed aerobic‐anaerobic microbial treatment process was developed previously for acid mine drainage (AMD) using straw as a substrate. The process was effective only if AMD was supplemented with sucrose. The present study was conducted to determine which, if any, of three cellulosic materials could sustain the microbial treatment of AMD without the addition of a sucrose amendment and to determine the effect of the retention time on the performance of the reactors. The performance of small reactors that treated simulated AMD in the continuous mode was evaluated using alfalfa (Medicago sativa L.) hay, timothy (Phleum pratense L.) hay, and straw with a 5‐d retention time. Parameters measured were pH, Fe, Al, sulfate, and ammonium. Timothy hay and straw sustained AMD mitigation for 3 wk, and thereafter all activity ceased. After the reactors ceased treating AMD, the mitigative activities were reinitiated by the addition of sucrose, but not by urea. Alfalfa sustained AMD mitigation for a longer time period than either straw or timothy. The effect of three retention times, 3.5, 7, and 35 d, was then investigated for reactors containing fresh alfalfa. Increasing the retention time resulted in better metal removal and a greater pH increase. With a 7‐d retention time, 75 L of simulated AMD were neutralized from a pH of 3.5 to a pH value greater than 6.5. Reactors operating with a 3.5‐d retention time treated only 58.3 L of simulated AMD before failing. Ammonium was detected in effluents of active reactors. The results of this study indicate that a low maintenance microbial treatment system can be developed with alfalfa as a substrate without the addition of a sucrose amendment.

Biotreatment of acidic zinc- and copper-containing wastewater using ethanol-fed sulfidogenic anaerobic baffled reactor

“…Ethanol (1,340 or 2,010 mg COD/L) was used as a carbon and electron source stoichiometrically to reduce sulfate to hydrogen sulfide and oxidize ethanol completely to CO 2 and H 2 O. Hence, COD/SO 4 2-ratio was kept constant at 0.67 on mass ratio throughout the study (Eqs. 1, 2).…”

“…The formation of acidic wastewaters can continue even tens or hundreds of years after mine closure if the conditions remain favorable [4,5].…”

Sulfidogenic fluidized‐bed treatment of metal‐containing wastewater at low and high temperatures

“…Metal-containing wastewater is created by the interaction of air and water with sulfides, mainly pyrite (FeS 2 ), found in overburden piles consisting of sub-commercial grade mining material leftover from the mining process and also in mine shafts. The formation of acidic wastewaters can continue even 10s and 100 years after mine closure, if the conditions remain favorable (Bechard et al, 1994;Szczepanska and Twardowska, 1999).…”

The potential utilisation of indigenous South African grasses for acid mine drainage remediation

“…Previous studies have included experiments on treating AMD with organic substrates such as straw and hay (Béchard et al, 1994) and rice husk (Chockalingam and Subramanian, 2006). The organic substrates serve as the electron donor for SRB, and carboxyl and phenolic acid groups in the organic substrates attach to a larger organic molecule which binds metal ions (Chockalingam and Subramanian, 2006).…”