Optimizing Filter Operation in an Ozone-Biofiltration Plant to Reduce Selection for Opportunistic Pathogens in Drinking Water Production
Objective 1: To characterize full-scale filter microbial communities before and after reduced backwash frequency.
Objective 2: To start up pilot-scale filters and characterize performance and microbial community structure.
Objective 3: To evaluate the impact of dechlorinating backwash supply.
Objective 4: To develop filter backwashing recommendations to share with utilities
During the reporting period, several activities to achieve Objectives 1 and 2 have been carried out, including extensive sampling of full-scale biologically active carbon (BAC) filters under normal and experimental conditions, and rehabilitation of pilot-scale filters. Initial results show that pH and fluoride were similar in both influent and effluent samples (p>0.05), turbidity and dissolved oxygen were significantly higher in filter influent vs. effluent (p=1.4x10-14 and p=0.014, respectively), and HPCs (as colony forming units/ml) were significantly higher in filter effluent vs. influent (p=7.3x10-6), as expected. Moreover, the total chlorine concentration in the backwash waste increases as a function of backwash time, while the turbidity of the backwash waste decreases as a function of backwash time.
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