AWWA MTC50235

The ultraviolet disinfectability of membrane treated wastewater was investigated using a laboratory collimated beam apparatus. Secondary clarified effluent, chlorinated to reduce membrane fouling, or unchlorinated, is treated by microfiltration (MF) followed by reverse osmosis (RO) at Orange County Water District's Water Factory 21 facility. Membrane treated wastewater has low bacterial density, suspended solids and turbidity and high UV transmittance. These properties allow a lower UV dose to achieve the same inactivation response when compared to conventionally treated wastewater. Coliphage MS2-seeded MF filtrate and RO permeate blended in ratios of 100:0, 60:40, 20:80 and 0:100, unchloirinated and chlorinated were investigated using UV doses ranging from 0 to 150 mWs/cm2. MS2 coliphage was seeded to a target of 5x10[6] pfu/mL and enumerated using a top overlay agar method of bacteriophage bioassay. The collimated beam unit (PCI-WEDECO) employed low-pressure mercury vapor lamps as the UV light source with a radiometer for direct measurement of UV intensity at 254 nm. Includes 4 references.