Factors Affecting Drinking Water Biofiltration

This research examined several important factors affecting the removal of biodegradable organic matter in drinking water biofilters. Laboratory‐scale biofilters were used and were fed a cocktail of easily biodegradable compounds. The factors investigated were chlorine or chloramine in the backwash water, air scour during backwashing, anthracite/sand versus granular activated carbon (GAC)/sand media, and low (5°C) versus high (20°C) temperature operation. Factorial design experiments showed that the three main factors (chlorine in the backwash water, temperature, and media type) and their interactions were significant in most cases. The temperature effect was more significant when chlorine was present. The GAC filters were much more resistant to chlorinated backwash water than were anthracite filters. Air‐scour effects were generally negligible except in some cases at low temperature with chloramine in the backwash water. Glyoxal removal was more sensitive to unfavorable biofiltration conditions than were removals of acetate, formate, and formaldehyde.