Water Treatment Processes

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Water Treatment Processes
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Why do we need to treat our drinking water?

• Industrial runoff
• Agricultural runoff
• Road runoff
• Residential runoff

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Industrial Runoff

• Some industrial facilities generate ordinary
  domestic sewage that can run off into sewage
  drains.
• Industries that generate wastewater with high
  concentrations of conventional pollutants (e.g.
  oil and grease), toxic pollutants (e.g. heavy
  metals, volatile organic compounds) or other
  nonconventional pollutants such as ammonia, need
  specialized treatment systems.

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Agricultural Runoff

• Nutrients (nitrogen and phosphorus) are
  typically applied to farmland as commercial
  fertilizer animal manure or spraying of
  municipal or industrial wastewater (effluent) or
  sludge.
• Nitrates and phosphates derived from these can
  pose health risks to humans if they end up in the
  drinking water.
• Sediment (loose soil) washed off fields is the
  largest source of agricultural pollution in the
  United States

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Road Runoff

• Sediments from construction sites and discharge
  of toxic chemicals such as motor fuels and
  concrete washout into the storm drains.

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Residential/urban runoff

• is surface runoff of rainwater created by
  urbanization. This runoff is a major source of
  urban flooding and water pollution in urban
  communities worldwide.

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Water Treatment Process
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Step 1 Raw Water Intake and Screens

• Intake structure - delivers water to the water
  treatment plant
• Lake or Reservoir
• Stream or River
• Groundwater
• Screens prevent trash, logs, or fish from
  entering the treatment plant

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Step 2 Coagulation and Flocculation

• In coagulation, coagulants like lime and alum are
  added to the water, which causes particulates to
  clump together.
• Next, the water is shaken into larger clumps,
  called flocs.

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Coagulation and Flocculation
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Step 3 Sedimentation

• The sedimentation process requires that the water
  stand for 24 hours, which allows the clumps to
  settle to the bottom.

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Settling Basin
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Step 4 Second Filtration

• The water is then filtered, 
• disinfected (usually with chlorine)
  and aerated.
• Aeration helps to remove certain contaminants
  like radon.

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Disinfection

• Disinfection process designed to kill or
  deactivate most microorganisms in water,
  including disease causing bacteria
• Types of disinfection
• Physical
• Ultraviolet (UV) rays
• Heat
• Chemical
• Chlorine
• Ozone

Fecal Coliforms
Giardia lamblia
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Storage and Distribution

• Storage keeping water for later use
• Elevated tanks
• Ground storage tanks
• Distribution system network of pipes and pump
  stations that transports finished water from the
  treatment plant to the user