AWWA WQTC59006

The results obtained during this study reinforced the potential of ozonation/biofiltration to control organics, ozone byproducts (OBP) and chlorinated disinfection byproducts (DBP) formation precursors. A total of six halaoacetic acids (HAA6) and total trihalomethanes (TTHM) measured in the filters were in compliance with Stage 1 of the Disinfection Byproduct Rule. Most substrates were removed within 3 minutes of empty bed contact time (EBCT) and, in general, additional contact times contribute very little to enhance biofilter performance. Dissolved organic carbon (DOC) was removed up to 30% and high removal of ozone byproducts was obtained in all filters (i.e., 65 to 84%), regardless of temperature regime. Implementation of second-stage ozonation resulted in significant ozone savings while maintaining similar CT credit and biofilter performance than first-stage biofiltration. Optimization of ozone oxidation placement in the treatment train resulted in a reduction of 20% in applied ozone. Biomass and microbial activity measurements correlated well with filter performance. Filters operated at cold temperatures performed as well as the ambient filters, after proper acclimation. Includes 10 references, tables, figures.