USING GRANULAR MEDIA AMENDMENTS TO ENHANCE NOM REMOVAL

Filters amended with anionic resin and granular activated carbon (GAC) achieved significantly higher (>75 percent) removals of organic carbo n adn trihalomethane formation potential during an 89-day filter run t han any other filter media combination studied. There was no significa nt difference in removal rate with GAC used as a surface or sublayer a mendment. Treatment efficiencies of the aluminum oxide-, anthracite-, and clinoptilolite-amended slow rate filters could not be clearly dist inguished from conventional slow sand filters with precursor removals <25 percent. Organic precursor removal by slow rate filters was consid ered a function of both the microbiological maturity and adsorptive ca pacity of the schmutzdecke and filter bed. Maintenance of elevated rem ovals by resin- or GAC-amended slow sand filters will eventually requi re the use of deeper amendment layers or frequent replacement or regen eration of the exhausted amendment.