A comparative pilot scale study analyzing the performance of biological versus conventional drinking water filtration with the application of various backwash strategies for headloss and ripening control

A pilot scale comparison study between conventional and biological dual media anthracite/sand filters was conducted to assess their performance and address industry concerns with biofiltration. The filters were subjected to various backwash and temperature conditions, including the addition of air scour and extended terminal subfluidization wash (ETSW) at 15-25°C and 0-5°C. The biofilters had significantly lower DBP formations (p<0.05) than the conventional filters under all conditions, by 33-46%. The biofilters exhibited greater headloss development than the conventional filters with a water only backwash, but it was found to be minimized by up to 19% when applying air scour and ETSW under warm water conditions. The conventional filters proved to be more vulnerable in terms of particle release during ripening, regardless of backwash strategy. A double stage ETSW step was also explored and found to improve ripening particle counts and turbidity in both filter types, even further than a single stage ETSW, while simultaneously providing headloss control.