Assessment of ultraviolet light disinfection efficiency of advanced wastewater treatment plant effluent
Pilot-scale operation of a 3-bank UV disinfection system for filter effluent from the Clark County Advanced Wastewater Treatment Plant has shown {dollar}>{dollar}4-log removal of seeded MS-2 coliphage at UV dosages of 80-100 milliwatt-seconds per square centimeter (mW-s/cm{dollar}\sp2{dollar}), and consistent removal of fecal and total coliforms to less than 2.2 MPN/100 mL at dosages in the vicinity of 50-80 mW-s/cm{dollar}\sp2{dollar} UV transmittance varied from 40% to 70% over the monitoring period and was strongly correlated with turbidity. No diurnal variations in effluent quality were detected during intensive sampling. Effluent quality was most strongly affected by storm events that change filter operation conditions. Rapid biological fouling occurred on the off-line banks. Inorganic fouling of on-line banks was minimal. Assuming a worst case UV transmittance (%) and required treatment dosage (mW-s/cm{dollar}\sp2),{dollar} treatment capacity of this 30-foot long, 6-lamp system was 0.10 million gallons per day.
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