Date of Award:


Document Type:


Degree Name:

Master of Science (MS)


Civil and Environmental Engineering

Committee Chair(s)

David K. Stevens


Eva C. Nieminski


Joan E. McLean


In order to meet increasing water demands and more stringent regulations drinking water treatment plant managers must continually look to new treatment strategies and optimization techniques. One such strategy is to eliminate chlorine residual before filtration, allowing indigenous bacteria already present in the source water to grow on the filter media. These microorganisms help improve effluent water quality by increasing organic and inorganic contaminant removal. The process is known as biological filtration, or biofiltration. The implications of converting a conventional filtration plant (not specifically designed for biofiltration) to a biofiltration plant are still not well understood. Therefore, the purpose of this study was to evaluate water quality and operational trends of a side-by-side full-scale biofiltration conversion at the Quail Creek Water Treatment Plant (QCWTP), located in Hurricane, Utah, and to determine the impact of pre-chlorination elimination on filter performance.

Four of twelve filters at the QCWTP were used to test the plant’s ability to operate in biological mode. One acted as a control and ran similar to the other eight filters in the treatment plant. The other three were converted to biofilters by quenching the influent chlorine residual with thiosulfate. The experiment lasted one year, so filter performance could be evaluated in each season. The results from the study indicated that the influent water was low in organic carbon (i.e. food for microorganisms), which resulted in small differences in biological activity between filters. Disinfection by-products (DBPs) (i.e. cancer causing agents created from the combination of chlorine and organic matter) were lower in the biofilters relative to the control. Biological conversion resulted in slightly higher and more variable final effluent turbidity values (though still within EPA drinking water standards and operational goals) compared to the non-biological filters; however, filter run times were unaffected.