Heterotrophic bacteria isolated from a chloraminated system accelerate chloramine decay

Area of Science:

• Environmental microbiology
• Water treatment chemistry

Background:

• Chloramine is a common disinfectant in water distribution systems.
• The stability of chloramine is influenced by microbial activity.
• Heterotrophic bacteria are ubiquitous in aquatic environments.

Purpose of the Study:

• To investigate the capability of heterotrophic bacteria from a chloraminated system to degrade chloramine.
• To identify bacterial species involved in chloramine decay.
• To elucidate the mechanism of chloramine decomposition by bacteria.

Main Methods:

• Isolation of heterotrophic bacteria from a laboratory-scale chloraminated reactor.
• Culturing of bacterial isolates with varying acetate concentrations and chloramine.
• Monitoring of chloramine, acetate, and ammonium concentrations during bacterial growth.
• Detailed mechanistic studies using a Mycobacterium sp. isolate.

Main Results:

• Sixty-two heterotrophic bacterial cultures were isolated, with 93.3% identified as Mycobacterium sp.
• Bacterial growth was correlated with the decrease in chloramine, acetate, and ammonium levels.
• Chloramine auto-decomposition, likely enzyme-mediated, was identified as the primary decay mechanism.

Conclusions:

• Heterotrophic bacteria play a significant role in chloramine stability within water distribution systems.
• Current strategies for water disinfection should consider the impact of heterotrophic bacteria.
• Minimizing heterotrophic bacterial populations may be necessary to enhance chloramine efficacy.