Target life stage: Veligers.
Recommended uses: Raw water systems, power-generating plants
Control objective: 100-percent veliger mortality.
Chemical type: Nonoxidizing.
Chemical form: Aluminum sulfate.
Recommended concentration: > 130 mg/l for veliger mortality.
Application Process:
Inject a concentration of aluminum sulfate (a coagulant) into the raw water supply at a point midway between two sidestream monitors. Laboratory tests (Mackie and Kilgour 1993) indicate that aluminum sulfate concentrations must be above 130 mg/l to cause 50-percent veliger mortality within 24 hr. The physical presence of aluminum sulfate has been shown to remove living veligers at concentrations above 100 mg/l (Mackie and Kilgour 1993). The pH drop caused by the chemical reactivity of the aluminum sulfate with the water may cause an instantaneous kill of veligers, especially in the mixing zone (Claudi and Mackie 1994).
Program efficiency: Determined by examining the data collected by the sidestream monitors before, during, and after application.
Additional considerations: Prechlorination greatly improves aluminum sulfate's efficiency. It is thought that the chlorination will cause the veligers to close their shells and increase their settling rate (Claudi and Mackie 1994).
Management and Control Contents