THE INFLUENCE OF FILTRATION ON ULTRAVIOLET DISINFECTION OF SECONDARY EFFLUENT FOR MICROIRRIGATION

A microirrigation system with an ultraviolet (UV) disinfection unit was operated under field conditions using filtered secondary effluent. Over a nine-month period the study was conducted in three phases with the filtered effluent exposed to an average UV dose of 100 mW·s/cm 2 . The rate of filtration was reduced to improve disinfection in each subsequent phase. Three different emitter designs, automatic self flushing, continuous self flushing, and tortuous path turbulent flow (all 4 L/h (1 gal/h), were tested . Media filtration was observed to remove significant amounts of suspended solids, to alter the particle size distribution of the secondary effluent, and to improve disinfection efficiency of UV radiation. Adequate filtration to remove particles greater than 40 µm was deemed necessary for effective UV disinfection to prevent clogging of the emitter types tested.