Study of Pre-Ozonation on Sand Filter Efficiency

The objective of the experiment was to determine the effects of pre-ozonation on sand filtration efficiency and the reduction in turbidity. Although ozonation is primarily used for disinfection, it is stated in Libra's test that it also acts a powerful oxidizer and breaks down suspended solids. This will be analyzed based on the reduction in turbidity levels of the samples used. In this study three water samples were used; a simulated surface water sample, a stagnant lake water sample and a sample obtained from a pond with abundant wildlife. The traditional surface water treatment of settling followed by sand filtration reduced the turbidity by approximately 6% on average, however with pre-ozonation the reduction was increased to over 30%. The simulated surface water showed a maximum reduction in turbidity of 80% with 188 mg/L dose. The maximum reduction in turbidity for the pond and lake water samples was 50% and 70%, respectively. The baseline suspended solids removal data of settling and filtration without ozonation resulted in an average reduction of 11%, likewise the reduction levels were increased dramatically with ozonation. Of the three samples the lake water showed a maximum reduction of approximately 90% with applied ozone dose greater than 500 mg/L. The Pond water showed only 70%, while the tap water showed a maximum reduction of 91% at doses greater than 500 mg/L. Thus pre-ozonation may be an effective method to increase effectiveness is sand filtration systems.