Chlorine/Chloramines Treatment

 During the Main Process of Water Treatment Chlorine/Chloramines are used in the Disinfection Stage of the process. This stage comes before the finished water storage cycle and after the disinfectant floride.

The Disinfection Basin Cycle

Disinfection, sometimes referred to loosely as chlorination, is a necessary part of the water treatment process. It kills pathogens, and it produces chemical byproducts. Disinfection is typically done by adding small amounts of a chlorine-based disinfectant to water. It destroys water-borne microbes, bacteria, and viruses — organisms that can cause serious illnesses or death. Typhoid and cholera, which have killed hundreds of thousands of people in global epidemics, have been controlled in the United States through the addition of disinfectant to drinking water.

Key Pollutants That Are Removed During this Step

Disinfection is needed to inactivate (kill) bacteria and viruses that make it through the physical removal (filtration) steps. Viruses and Giardia are effectively killed by chlorine. Chlorine and Chloramines also kill pathogens that can be harmful to humans if consumed.



Major Advantages of Using Chlorine/Chloramines as a Disinfectant

The advantage of chlorination is that it continues to kill bacteria as water moves through pipes to the tap. Chlorine has the major advantage of ensuring clean water right up to the tap, whereas the action of other disinfectants - such as ozone, ultraviolet light and ultrafiltration - is only temporary. In addition to purifying water, chlorine helps remove tastes and odors, controls the growth of slime and algae in mains pipes and storage tanks, and helps to remove unwanted nitrogen compounds from water.

Major Disadvantages of Using Chlorine/Chloramines as a Disinfectant

The major disadvantage is the possibility of disinfection by-products. Excess chlorine in water can combine with organic material in the water to form substances such as Trihalomethanes, which can cause liver, kidney, or central nervous system problems, and are linked to an increased risk of cancer over a lifetime exposure. See Disinfection Byproducts sub page for more information.

Other disadvantages include Cryptosporidium which is resistant to chlorine. Cryptosporidium rose to public attention in 1993 when it sickened over 400,000 people, killing a hundred, in Milwaukee, Wisconsin. Largely because of this scare, new or amended U.S. drinking-water regulations developed early in the twenty-first century that expanded water treatment requirements specifically to address Cryptosporidium. Although chlorine is not effective against Cryptosporidium, alternative disinfectants such as ozone and ultraviolet light do appear to be effective at killing it. In Europe, both of these disinfectants are often used without chlorination to kill bacteria in the water supply.

The US EPA has set a maximum limit for the amount of chlorine in drinking water, it is 33% higher than chlorine used in pool water. On February 16th, 2011 the new maximum of 4.0 mg/l chlorine and chloramines in drinking water will be effective nationwide. Chronic exposure to concentrations of chlorine of around 5 mg/l caused respiratory complaints, corrosion of the teeth, inflammation of the mucous membranes of the nose and increased susceptibility to tuberculosis.

Other Forms of Disinfectant During the Water Treatment Process

Ultraviolet Light

Ultraviolet germicidal irradiation (UVGI) is a sterilization method that uses ultraviolet (UV) light at sufficiently short wavelength to break down microorganisms. Using a UVGI device in certain environments like circulating air or water systems creates a deadly effect on micro-organisms such as pathogens, viruses and molds that are in these environments. Coupled with a filtration system, UVGI can remove harmful micro-organisms from these environments. There are potential dangers that come with this disinfectant. At certain wavelengths (including UVC) UV is harmful to humans and other forms of life. In most UVGI systems the lamps are shielded or are in environments that limit exposure, such as a closed water tank or closed air circulation system, often with interlocks that automatically shut off the UV lamps if the system is opened for access by human beings. Limited exposure mitigates the risk of danger.

Subpages (1): Disinfection Byproducts
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