English

Abstract

The importance of sulfate-reducing bacteria for metal precipitation in anaerobic passive treatment systems for remediation of acid mine drainage has been established. Conditions leading to decline of sulfate-reducing activity and failure of passive treatment systems are not well understood; however, this study hypothesizes that decline in performance is related to decline in substrate availability for sulfate-reducing bacteria. Other microbial functions break down complex organic material to provide the simple organic compounds required by sulfate reducers, and are essential for sustainability of passive mine drainage treatment systems. An understanding of relationships between microbial activities and system performance is thus essential to the design of anaerobic passive treatment systems for long-term performance. The objective of this research is to develop a method to: (1) assess the activities of important microbial functions that influence sulfate reduction in an anaerobic passive treatment system, and (2) apply the method to an anaerobic column system treating synthetic mine drainage to detect differences in activities as the system ages, for the purpose of determining the rate-limiting step(s) in the degradation of organic material as they relate to sulfate reduction. The approach involves the use of a long-term column study in conjunction with short-term batch studies, which add substrate supplements to the organic material from sacrificed columns in order to probe the activities of important microbial functions. The substrate supplements each target a distinct microbial function at a specific step in the anaerobic degradation of complex organic compounds. Activities measured in batch studies correlate to overall column performance in terms of sulfate-reducing activity. Results of gas analyses from the batch studies illustrate the usefulness of this approach in quantifying important microbial functions, as well as identifying the rate-limiting step(s) in the degradation of organic material as the system ages. Data suggest an overall stimulation of metabolic activities by cellobiose and glucose, and indicate the rate-limiting step(s) lie between cellulose and cellobiose.