Small particles in distribution systems: effect of improving treatment

Abstract

Particles originating in water following treatment can create operational and water quality issues in distribution systems. The effect of treated water particle concentration on distribution water quality was assessed by monitoring particles at the beginning and end of four pilot distribution systems (PDSs). Flow conditions in this study produced a 75-h retention time that included three 8-h overnight stagnation periods. Generally, higher levels of treatment produced water of lower particle concentration, which resulted in lower particle concentrations and particle volume concentrations in the PDSs. Particles entering the PDS were almost all in the 0.5- to 2-µm size fractions. Deposition and resuspension were found to be the primary mechanisms influencing particle behavior in these systems, with particles lost in systems through deposition and resuspension during flow disturbances. Study results suggest that particle monitoring should be more widely adopted as a management tool and that instruments capable of detecting smaller size fractions should be used.