ENUMERATING AND DISINFECTING BACTERIA ASSOCIATED WITH PARTICLES RELEASED FROM GAC FILTER-ADSORBERS

Granular activated carbon (GAC) in filter-adsorbers provides an excell ent support surface for the proliferation of microorganisms. Therefore , GAC beds may release particles of carbon with attached bacteria that are protected from disinfection. In this pilot-plant study, particles were collected from the product waters of GAC filter-adsorbers, exami ned for bacterial colonization, and characterized by energy-dispersive X-ray analysis. Results showed that bacteria attached to GAC particle s could be disinfected with chlorine if particle concentrations were i n the range found in the product waters, i.e., <20 mu g/L. Increasing particle concentration tenfold interfered with disinfection efficiency . Powdered activated carbon used in pretreatment contributed to the pa rticles found in product water.