Safe Drinking Water

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Safe Drinking Water
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• The majority of people in the US get their water
  from public water systems that have to meet state
  or federal requirements for safety
• Almost 20 of the worlds population does not
  have regular access to clean drinking water

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Common water-borne diseases

• Cholera
• Transmitted by Vibrio cholera and causes
  gastrointestinal issues
• Giardiasis
• Transmitted by Giardia lamblia parasite and
  causes GI issues
• Legionellosis
• Caused by Legionella pneumophila bacteria and
  leads to flu like symptoms

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Cholera
Giardia lamblia
Legionellosis
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Organisms in the Water

• Maximum Contaminant Level Goals (MCLG) are in
  place to prevent water borne illnesses
• Zero tolerance for Giardia, Legionella and
  viruses
• Indicator organisms like fecal coliform bacteria
  are used for water quality testing

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Making Water Safe

• If surface water or well water is contaminated
  there are a few methods that can clean it
• Chlorination- chlorine can disinfect (kill) most
  microbes
• UV Light- kills bacteria more expensive than
  chlorination
• Heat- water heated to a rolling boil for at least
  one minute can kill bacteria and protozoan cysts
• Filtration- activated carbon filters remove
  organic chemicals from water

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The Treatment Process
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Waste Water Treatment

• Most of the wastewater from residential areas is
  biodegradable
• Industrial water and storm runoffs contain toxic
  chemicals that can interfere with treatments

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Treatment Process

• 1. Screening
• Wastewater entering the treatment plant includes
  items like wood, rocks, trash and even dead
  animals.
• The water is run through a screen to catch these
  solids
• Most of these materials are sent to a landfill.

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• 2. Pumping
• The wastewater system relies on the force of
  gravity to move sewage from your home to the
  treatment plant. (So wastewater-treatment plants
  are located on low ground, often near a river
  into which treated water can be released).
• If the plant is built above the ground level, the
  wastewater has to be pumped up to the aeration
  tanks

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• 3. Aerating
• The wastewater is sent to a tank where it is
  exposed to oxygen to allow decomposition to begin

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• 4. Removing sludge
• Wastewater then enters the sedimentation tanks
• Large particles (AKA the sludge) settles out of
  the wastewater and is pumped out of the tanks
• Some of the water is removed in a step called
  thickening and then the sludge is processed in
  large tanks called digesters.

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• 5. Removing scum
• Lighter materials float to the surface
• This 'scum' includes grease, oils, plastics, and
  soap.
• Slow-moving rakes skim the scum off the surface
  of the wastewater. Scum is thickened and pumped
  to the digesters along with the sludge.

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• 6. Killing bacteria
• Wastewater flows into a 'chlorine contact' tank,
  where the chemical chlorine is added to kill
  bacteria,
• The chlorine is mostly eliminated as the bacteria
  are destroyed, but sometimes it must be
  neutralized by adding other chemicals
• The treated water (called effluent) is then
  discharged to a local river, wetland or the ocean

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The Sludge

• Another part of treating wastewater is dealing
  with the solid-waste material
• These solids are kept for 20 to 30 days in large,
  heated and enclosed tanks called 'digesters.'
• Here, bacteria break down (digest) the material,
  reducing its volume, odors, and getting rid of
  organisms that can cause disease
• The finished product is mainly sent to landfills,
  but sometimes can be used as fertilizer.

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Wastewater Treatment Video
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Summarizing Questions10 points

1. Why is chlorine added to water during the
   treatment process?
2. Expand Why is there more chlorination and
   filtration of water during summer months?