Biological mechanisms in slow sand filters

Bench‐scale investigations of particle removal mechanisms in slow sand filters identify bacterivory as the only significant biologically mediated particle removal mechanism. Particle and E. coli removal mechanisms in slow sand filters were investigated at bench scale. Sodium azide (an inhibitor of oxidative phosphorylation) caused appreciable reduction in particle and E. coli removal; this indicated biological removal mechanisms were significant. Bacterivory was identified as the biological mechanism principally responsible for bacteria removal. There was no evidence of significant particle removal by attachment to biofilms.