DUAL ROLE OF ACTIVATED CARBON PROCESS FOR WATER REUSE

Four granular activated carbon (GAC) filters went into service in 1977 at the County Sanitation Districts of Los Angeles County's Pomona Wat er Reclamation Plant to treat 0.44 m(3)/s (10 mgd) of wastewater for r euse. This article provides long-term operational information for simi lar water reuse applications. The GAC filters successfully served dual roles as tertiary filters and adsorbers of organics. After 10 regener ations with an average 10% makeup of virgin carbon per regeneration, t he iodine number dropped from 1 000 mg/g to a leveled-off value of 600 mg/g; the molasses number increased from 170 to 250; apparent density decreased slightly; and mean particle diameter decreased from 1.65 mm to 1.2 mm. The ash content increased steadily from the initial 6.5% t o more than 15% after 15 regenerations. After 20 regenerations, the GA C filters still exerted a total organic carbon removal from more than 80% initially to a level of 20%. The removal of true color by the rege nerated carbon decreased from 90% initially to 30%. With the provision s of an afterburner and a wet Venturi scrubber, the air emissions from the carbon regeneration facility were effectively controlled. The ene rgy and labor costs become the dominant operation and maintenance cost s as the regeneration frequency increases.