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ABSTRACT: The Joint Water Pollution Control Plant (JWPCP) of the Sanitation Districts of Los Angeles County provides advanced primary and partial secondary treatment for 15.3 m3/s (350 MGD) of wastewater. A 7-mo pilot plant study evaluated several tertiary treatment alternatives for in-plant water reuse. The influent to the tertiary treatment system was the high-purity oxygen-activated sludge plant effluent. Three filtration systems were evaluated: a deep-bed anthracite filter, a shallowdepth pulsed-bed sand filter, and a continuous backwash deep-bed sand filter. Chlorination and ultraviolet (UV) disinfection were also compared. All three filters were capable of consistently meeting the State of California's effluent turbidity limit. The differences in turbidity removal efficiencies were insignificant. Changes in hydraulic loading rate, up to 0.2 m3/m2 min (5 gpm/ft2), had insignificant effects on the quality of all filter effluents when filtering normal secondary effluent. The effect of chemical filter-aids on turbidity removal depended strongly on the characteristics of the filter influent and the filter design configuration. Breakthrough of alum might occur with an excessive dosage of alum. The estimated costs for filtering the secondary effluent by the three filters were similar. A high-UV dose of 300 mW-s/cm2 would be required to reduce the total coliform concentrations -2.2 MPN/100 mL, mainly because of the low UV transmittance (40-63%). The 2.2 MPN/100 mL coliform standard could be met either by a chlorine residual of 5 mg/ L with a contact time of 120 min or 10 mg/L for 60 min. Water Environ. Res., 69, 34 (1997).
KEYWORDS: chlorine, disinfection, filtration, reuse, tertiary treatment, ultraviolet.
The Joint Water Pollution Control Plant (JWPCP) is operated by the Sanitation Districts of Los Angeles County (the Districts). It provides advanced primary and partial secondary treatment for 15.3 m3/s (350 MGD) of wastewater. A 7-mo pilot plant study was conducted recently, from August 1994 to February 1995, to evaluate several tertiary treatment alternatives for in-plant water reuse. The influent to the tertiary treatment system was the clarified effluent from the high-purity oxygenactivated sludge plant. The potential in-plant reuse applications include wash water for plant operations and truck cleaning and process water for cooling towers. The overall objective was to provide information for a conceptual design and a process cost estimate for the in-plant water reuse.
Three different filtration...