Biofiltration optimization: Phosphorus supplementation effects on disinfection byproduct formation potential

Abstract

This study investigates the effects of phosphorous supplementation on the formation potential of total trihalomethanes (TTHM fp ) and five species of haloacetic acids (HAA5 fp ) during exposure to clearwell disinfection contact times. In addition, the study investigates the effects of phosphorous supplementation on the dissolved oxygen, organic carbon and nitrogen removal along with biofilm coverage of the filter media and biomass viability of the attached biofilm. The uptake of total phosphorus in the P enhanced filter did not correspond to the consumption of readily assimilated nitrogen or the consumption of soluble carbon. As such, the dissolved organic carbon reduction in the biologically active filters was shown to not be phosphorous nutrient limited. The clearwell TTHM fp was shown to be reduced in all filters across all measured biological filtration times in the control and P enhanced filters. The HAA5 fp increased with phosphorus-supplemented operation at specific filtration cycle times as compared to non-phosphorus-supplemented operation, indicating the potential for production of HAA5 with phosphorous supplementation. Enhanced biofilm coverage of the anthracite and sand media was observed during phosphorous supplementation. In addition, increased viability of the cells embedded in the biofilm was observed in the sand media at depth during phosphorus-supplemented operation.