Target life stages: Veligers and adults.
Recommended uses: Raw water systems, hydroelectric plants.
Control objectives: Variable depending upon concentration applied.
Chemical type: Oxidizing.
Chemical form: Ozone.
Recommended concentration: Variable depending upon the temperature and objective.
Application Process:
Chemicals are injected into the raw water system between two sidestream monitors at predetermined time intervals from multiple injection points. At comparable residual levels, ozone outperforms chlorine in terms of contact time (Lewis et al. 1993). Ozone dissipates rapidly in raw water, resulting in low pipe residuals and no downstream environmental impacts (Claudi and Mackie 1994). Currently widely used for bacterial and viral inactivation in the sewage and water treatment industries, ozonation equipment is expensive to purchase and maintain.
If the control objective was 100-percent mortality of established adult populations, it would be difficult to maintain sufficient ozone concentrations throughout the system. One hundred-percent mortality of veligers and postveligers is achieved with a minimum of 5 hr of contact time at 0.5 mg/l and 15-20 °C (Lewis et al. 1993), 100-percent adult mortality within 7-12 days at concentrations of 0.5 mg/l, 7-8 days at concentrations of 1.0 mg/l, and 5-6 days at concentrations of 2.0 mg/l, at 15-20 °C (Claudi and Mackie 1994).
Program efficiency: Determined by examining the data collected from the sidestream monitors before, during, and after application.
Additional considerations: Time to death for any life stage depends upon both ambient temperature and concentration.
Further information on the use of ozone as a control method is available in EPRI (1992) and Claudi and Mackie (1994).
Management and Control Contents