Chlorination

1
Chlorination

• References
• 1. Treatment Systems for Water Supplies AE-1046,
  June 1992
• Fred Bergsrud, Water Quality Coordinator,
  Minnesota Extension Service
• Bruce Seelig, Water Quality Specialist, North
  Dakota Extension Service
• Russell Derickson, Extension Associate in Water
  and Natural Resources, South Dakota Extension
  Service
• 2. Water Treatment Notes Chlorination of
  Drinking Water
• Cornell Cooperative Extension - Linda Wagenet and
  Ann Lemley
• September 1988

2
What impurities will chlorination remove?

• Chlorination is a water treatment that destroys
  disease-causing bacteria, nuisance bacteria,
  parasites and other organisms.
• Chlorination also removes soluble iron, manganese
  and hydrogen sulfide from water.

3

• Disease-causing bacteria can infect humans in
  several ways. Disease-causing organisms are
  transmitted from host to host in many ways
  including through a contaminated water supply.
• If a water supply becomes contaminated,
  elimination of the source is the most permanent
  solution. Chlorination is used to kill
  disease-causing bacteria in a water supply.

4
Advantages of chlorination

• 1. Controls Disease-Causing Bacteria
• 2. Controls Nuisance Organisms Chlorine
  treatment will control nuisance organisms such as
  iron, slime and sulfate-reducing bacteria.
• 3. Mineral Removal Clorination removes large
  amounts of iron, manganese and hydrogen sulfide
  from water by oxidizing them into filterable
  insoluble forms.

5
Disadvantages of chlorination

• 1. No Nitrate Removal Chlorine will not remove
  nitrates from water.
• 2. Causes Smell and Bad Taste Chlorine in water
  is not poisonous to humans or animals. However,
  if the concentration is great enough the water
  will taste bad so consumption may be reduced.
  Some people object to the smell and/or taste of
  very small amounts of chlorine.

6
The chlorination process

• 1. Chlorine demand is the amount of chlorine
  required to kill bacteria, oxidize iron or other
  elements in the water.
• 2. Free available chlorine residual is the amount
  of chlorine remaining in the water after the
  chlorine demand has been met.
• 3. Contact time is the amount of time that the
  chlorine is present in the water. The combination
  of chlorine residual and contact time determines
  the effectiveness of the chlorination treatment.

7
Chlorine treatment

• Chlorine readily combines with chemicals
  dissolved in water, microorganisms, small
  animals, plant material, tastes, odors, and
  colors. These components "use up" chlorine and
  comprise the chlorine demand of the treatment
  system. It is important to add sufficient
  chlorine to the water to meet the chlorine demand
  and provide residual disinfection.

8
Trade-offs

• Amounts of Chlorine used must be enough to kill
  and remove all undesired organisms and minerals
  while being small enough so it does not adversely
  affect the taste or smell of the water.
• These amounts are tested by experimentation and
  controlled by local government agencies.