Enhancing Biofilm Recovery From Carbon Filters for Molecular Analysis and Flow Cytometry

Effective biofilm recovery is essential when characterizing microbial communities on granular filter media in water treatment applications. This study evaluated (1) DNA extraction kit modifications to maximize DNA recovery and (2) low frequency sonication (40 kHz) durations to maximize recovery of viable cells for flow cytometry (FCM) considering filter media type (anthracite and granular activated carbon [GAC]), media age, and filter runtime. Both DNA and intact cell concentrations were greater for new GAC (< 12 months of full‐scale operation) and anthracite compared to old GAC (> 20 years). Biomass yields for old GAC were improved by using a less aggressive bead‐beating protocol (for DNA) and reduced sonication duration (for intact cells). Finally, collecting media at the beginning of a filter run (i.e., post‐backwash) improved biomass recovery compared to sampling after long filter runtimes. Further study of carbon attrition during extraction is recommended.