Ultraviolet and ultrasound disinfection of a recycle irrigation water

Abstract

Disinfection of an irrigation recycle water is evaluated by an investigation divided into three phases. Phase I experiments investigates disinfection by ultraviolet light alone; Phase II examines ultrasound disinfection; and Phase III investigates combined effects of ultrasound and ultraviolet light. Phase III also evaluates unit process sequencing in order to optimize disinfection performance. Ultraviolet light produced an average microorganism inactivation of 85.4% following one minute of UV irradiation. The response became asymptotic at this point. Cell viability, measured by ATP concentration, was not reduced below 10% until 15 minutes of UV treatment. Ultrasonic treatment resulted in microorganism survivals ranging fram 66.4% (60 W/1 and 30 minutes of treatment) to 25.1% (350 W/1 and 30 minutes of treatment). Combined treatment processes produced comparable results to UV only disinfection schemes. Overall, a satisfactory level of disinfection was not attained using UV light or ultrasound. The lack of disinfection response was attributable to the presence of interfering water constituents.