Biomass Evolution in Full-Scale Anthracite-Sand Drinking Water Filters Following Conversion to Biofiltration

This study investigated biomass concentrations, as measured by adenosine triphosphate (ATP), in full-scale, anthracite-sand biofilters as they acclimated to conversion from direct filtration to biofiltration. Results showed that there were three scales of biofilter biomass accumulation: an accumulation period within each filter cycle, and an accumulation period associated with adapting to chlorine-free conditions for both biomass measured at the start and end of the filter cycle. Both start-and end-of-cycle biomass reached steady state after 220 days of operation. Start-of-filter-cycle biomass accumulated at a rate of 0.008/day and reached a steady-state concentration of 59 ng ATP/cm(3) media. End-of-filter-cycle biomass reached an apparent steady-state concentration of 267 ng ATP/cm(3) media. Biomass measured over a single filter cycle had an accumulation pattern similar to start-of-filter-cycle biomass but accumulated more rapidly (1.96-4.46/day).