Using granular media amendments to enhance NOM removal

Abstract

Granular media amendments to slow sand filtration show promise in improving organic precursor removal.Filters amended with anionic resin and granular activated carbon (GAC) achieved significantly higher (>75 percent) removals of organic carbon and trihalomethane formation potential during an 89‐day filter run than any other filter media combination studied. There was no significant difference in removal rate with GAC used as a surface or sublayer amendment. Treatment efficiencies of the aluminum oxide–, anthracite‐, and clinoptilolite‐amended slow rate filters could not be clearly distinguished from conventional slow sand filters with precursor removals <25 percent. Organic precursor removal by slow rate filters was considered a function of both the microbiological maturity and adsorptive capacity of the schmutzdecke and filter bed. Maintenance of elevated removals by resin‐ or GAC‐amended slow sand filters will eventually require the use of deeper amendment layers or frequent replacement or