Under the quiescent condition when flow velocity and

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Under the quiescent condition, when flow velocity and turbulence is minimal, particles that are denser than water will settle at the bottom of the tank (Nathanson & Schneider, 2015). This is what is known as sedimentation. The layer that accumulates at the bottom is called sludge. The tank itself is usually called a sedimentation tank but other names like settling tanks or clarifiers are also used. Other factors are part of the sedimentation process. Inside the sedimentation tank, the water does not stop flowing altogether. If flows slowly enough to allow particles to settle to the bottom. The time the water remains inside the tank is called detention time. Containers are also designed to prevent them from overflow and to prevent the water from flowing faster than what is calculated to complete the sedimentation process known as short-circuiting. Disinfection The last step of the water treatment process is disinfection. This process is designed to disable or kill hazardous pathogens that remain in the water (Nathanson & Schneider, 2015). Without disinfection, there is potential to spread waterborne illnesses such as adenovirus infection, amebiasis, cholera, hepatitis A and others. Under certain conditions, some of these diseases can be fatal if not treated in time.
UNIT VIII ESSAY5Chlorination.To disinfect the water, the chemical chlorine must be added. There are times when chlorine may react with organic compounds resulting from plant decay. This creates trihalomethanes (THM’s) compounds that may cause cancer in humans. The development of these compounds can be prevented by ensuring that chlorination is done after the removal of most organics have been eliminated by previous treatment methods. Even though chlorine is sufficient to kill most pathogens, additional disinfection methods have been developed to ensure the quality of the water is up to standards and safe to drink.Ozone.Ozone is another process of the disinfection process. It is a highly reactive gas at ordinarytemperature and pressure and acts as a potent disinfectant when added to water (Nathanson & Schneider, 2015). Unlike chlorine, it does not leave a taste or odor in the water. Because of its reactivity, it cannot be stored and must be created on-site. Another positive aspect of the Ozone gas is that it does not react with organics left in the water to develop THM’s. Even though it is more effective than chlorine, it is not used as often because it is an expensive method of disinfection. Ultraviolet Radiation. The use of ultraviolet (UV) light is a type of electromagnetic radiation also used to disinfect water. When used under high doses, it destroys bacteria and viruses (Nathanson & Schneider, 2015). This method does not involve chemicals, which makes it a more reliable and economical to use. The UV radiation is recommended to be used with other disinfection methodslike chlorine. When both ways are used together, it ensures that cryptosporidium can be
UNIT VIII ESSAY6

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