Coagulation and Flocculation
These are the initial procedures during treatment of water. Chemical substances possessing a positive charge are added to water in this compartment. The positive charge neutralizes the negative charge from dirt leading to the formation of huge fragments known as floc.
Floc is heavier than other particles present in water. Therefore, this process allows floc to remain at the base of the tank.
After the sedimentation process, the transparent water at the top of the tank moves across filters consisting of assorted components such as sand, charcoal or gravel. These components have different pore sizes that facilitate the removal of dissolved particles such as dust, microorganisms, and chemicals.
Disinfectants such as chlorine are then added to the filtered water in the disinfection compartment to eliminate any remaining contaminant. The chemicals also safeguard the water from germs during storage and transportation to homes.
Clean water is then stored in reservoir tanks from where it is piped to consumers.
In the U.S.A., chlorine is generally preferred as a disinfectant over ozone because it has a residual. The presence of a residual is important because it shows that water contains an adequate quantity of chlorine to kill all microorganisms. It also provides defense against recontamination in the course of storage.
The existence of free residual in treated water is associated with the absence of harmful microorganisms. Consequently, it is an important factor that gauges the potability of water.
In recent years, ozone has been replacing chlorine as the primary disinfectant in the U.S.A. One key advantage of using ozone to treat water is that there are few byproducts released into the water from the process. The release of many byproducts into treated water usually puts such water at risk. During chlorination of water, additional steps are usually required to get rid of these byproducts.
However, ozone treatment of water evades these additional procedures. One other benefit of ozone water purification is that there are no added chemicals that interfere with the natural taste of water. Therefore, the resultant water does not have the characteristic taste of chlorine.
However, ozone treatment of water also has disadvantages. It is thought that this procedure releases little quantities of bromate, which is thought to be a carcinogen. In addition, ozone treatment does not offer any residual effect. Therefore, any harmful organism that endures the oxidation procedure evades the entire treatment process.