BIOFILTRATION PERFORMANCE .2. EFFECT OF BACKWASHING

In a biological dual-media (anthracite-sand) filter, backwashing with nonchlorinated water did not affect the biomass attached to the media at the top of the filter or the control of total organic DBPs. Backwas hing a similar concentrations of biomass attached to the media at the top of the filter and lower steady-state removal of the same parameter s. A loss of some of the attached biomass at the top of the filter occ urred immediately after backwashing with chlorinated, water, but later in the filter cycle the biomass recovered to its prebackwashing conce ntration. Concurrent with the loss of biomass was an increase in the c oncentrations of ozone DBPs in the filter effluent: these also recover ed to prebackwashing concentrations later in the filter cycle.