Biofiltration Optimization Strategies—Operational and Water Quality Adjustments

Biological filtration in drinking water treatment removes natural organic matter with the help of microorganisms through biodegradation. This research highlights findings that examined various backwash strategies and changes to water pH on biofilter performance. Research was conducted at two locations for two different studies—City of Ottawa, Britannia Water Treatment Pilot Plant and at the Carleton University Environmental Engineering Pilot Scale Lab. The Carleton biofilters were operated at pH values of 6.0, 7.5, 9.0 and 10.0 to assess for changes in organic carbon removal, ammonia removal, as well as headloss development. At pH levels of 6.0–7.5 similar DOC removal efficiencies were observed at ~65%, while raising pH decreased organic carbon removals to a low of 30%. Ammonia removal was also monitored and increased as pH increased, with removals as follows 12%, 50%, ~90%, ~90% at pH 6.0, 7.5, 9.0, 10, respectively. Headloss did not appear to be correlated to changes in pH. The following backwash strategies were evaluated in order to elucidate impacts on biofilter performance: a water only wash, a water wash plus air-scour, and the addition of an extended terminal subfluidization wash (ETSW). Overall, backwash strategies that included ETSW demonstrated promising results with regards to filter ripening, as expected, with no adverse impact on DOC removal. Of note, headloss development was decreased through changes to backwash strategy. Overall, this research demonstrated that small changes to biofilter operation are possible to improve biofilter performance.