Study of Low Dosage Pre-Ozonation on Sand Filtration Efficiency

The most traditional method for water filtration is the sand filter. Sand filters consist of sand, some type of activated carbon, and a more coarse aggregate such as gravel. Particles too large are then filtered out. Suspended particles too small for sand to catch are thus the problem, therefore different techniques are used to increase the efficiency of sand filters, these techniques are called pre-filtration. The goal of pre treatment is to coagulate, or clump together; the small suspended solids so that they may be caught in the filter. Current water treatment plants use many different types of pre-filtration: ferric, aluminum salts, or cationic polymers. One form of pre-treatment is ozonation. By electrically charging oxygen and allowing a third molecule to join, ozone, (O3), is created. Ozonation is the process of applying ozone to cause the small suspended particles in a given sample to coagulate. It has been studied and experimented for many years, proving a significant increase in coagulation and thus allowing the sand filtration to be more effective. As longer treatments of ozone are applied, the taste and odor may also be neutralized. In addition to the benefits previously stated, ozone may also be used as a disinfectant. In fact ozone oxidizes thousands times faster than that of chlorine. However, the production of ozone is somewhat energy intensive, and therefore an option that is sometimes over looked.