Long-term competition between sulfate reducing and methanogenic bacteria in UASB reactors treating volatile fatty...

Area of Science:

• * Environmental microbiology
• * Anaerobic digestion
• * Microbial ecology

Background:

• * Competition between methane-producing bacteria (MB) and sulfate-reducing bacteria (SRB) is crucial in anaerobic digestion.
• * Acetate is a key substrate utilized by both MB and SRB.
• * Understanding this competition impacts wastewater treatment and biogas production.

Purpose of the Study:

• * To investigate the competition for acetate between MB and SRB in upflow anaerobic sludge bed (UASB) reactors.
• * To determine the influence of COD:sulfate ratio on microbial dominance.
• * To model the long-term dynamics of this microbial competition.

Main Methods:

• * Operation of mesophilic UASB reactors treating volatile fatty acids (VFA) or acetate with varying COD:sulfate ratios.
• * Evaluation of acetate utilization partitioning based on conversion rates and microbial activities.
• * Dynamic simulations using a mathematical model with Monod kinetics.

Main Results:

• * A COD:sulfate ratio below 0.67 favored SRB dominance over MB.
• * Prolonged operation (250-400 days) was required for SRB to utilize 90% of acetate.
• * Mathematical modeling confirmed the long-term nature of acetate competition.

Conclusions:

• * High sulfate conditions shift acetate utilization towards SRB.
• * Reactor operational parameters (pH, solid retention time) and inoculum composition influence competition dynamics.
• * Optimizing conditions can accelerate SRB outcompetition of MB for acetate.