Substrate Pre-loading Influences Initial Colonization of GAC Biofilter Biofilms

Area of Science:

• Environmental Microbiology
• Water Treatment Technologies
• Biotechnology

Background:

• Microbial communities on biological/granular activated carbon (BAC/GAC) are crucial for pollutant removal efficiency.
• Biofilm development and stability on GAC influence the performance of water treatment systems.

Purpose of the Study:

• To investigate if pre-loading GAC with organic carbon substrates (sucrose, lactose, LB medium) promotes stable, high-coverage biofilms.
• To assess the impact of substrate pre-loading on the temporal dynamics of biofilm biomass and microbial community composition on GAC.

Main Methods:

• Substrate pre-loading of new GAC with sucrose, lactose, or LB medium.
• Monitoring of biofilm biomass using flow cytometry (FCM).
• Analysis of microbial community composition via sequencing.
• Experiments conducted in both batch and continuous-flow setups over prolonged operational periods.

Main Results:

• Substrate-loaded GAC showed significantly higher initial biofilm biomass (3-114 times) compared to non-loaded controls.
• Initial microbial richness was lower on loaded GAC (13-28% of control), with distinct compositions between batch and continuous-flow experiments.
• In continuous-flow systems, biofilm biomass and community composition converged with controls after 64 days, indicating instability.

Conclusions:

• Substrate pre-loading effectively enhances initial GAC colonization, influencing biomass and microbial community structure.
• The enhanced biofilm structure is not stable long-term due to continuous dispersal and competition from influent bacteria.
• Findings highlight the dynamic nature of GAC biofilms and the challenges in maintaining stability for consistent pollutant removal.