CE 370

1
CE 370

• Taste and Odor Control

2
Objective

• One of the objectives of water treatment is to
  produce water that is free of taste, odor, and
  color.

3
Causes of Taste and Odor

• Taste and odor can be caused by
• inorganic salts
• metal ions
• natural organic compounds
• organic compounds resulting from industrial
  activities
• products of biological activities
• In surface waters, algae is frequently the main
  cause of taste and odor problems

4
Causes of Taste and Odor

• In water systems, taste and odor problems are
  unique in each system.
• in groundwater, odor is caused by dissolved
  gasses that can be stripped from water by
  aeration.
• in surface water, odor is caused by nonvolatile
  organic compounds which can not be removed by
  aeration.

5
Prevention

• Preventing taste and odor-producing substances
  from reaching surface water should be given
  priority.
• if the problem is caused by industrial waste
  discharge, the source may be removed.
• if algal growth is causing the problem, copper
  sulfate can be used to stop the growth of algae.

6
Treatment

• Activated Carbon
• Oxidation

7
Activated Carbon

• The use of activated carbon adsorption is
  considered an effective treatment for the removal
  of taste and odor from water.
• Activated carbon can be prepared by controlled
  combustion of
• hardwood charcoal
• nut sells
• other carbonaceous materials
• Activated carbon is commercially available in
  granular or powdered forms.
• Carbon adsorbs chlorine, so the two chemicals
  should not be applied at the same time or in
  sequence without proper time interval.

8
Oxidation

• Oxidation is also used to remove taste and odor
  from water.
• Oxidation can be done by the use of
• chlorine (formation of trihalomethanes must be
  considered)
• chlorine dioxide (has the same oxidative power as
  chlorine without forming THMs)
• potassium permanganate (strong oxidizing agent
  but forms MnO2, so filtration must be applied
  after treatment with KMNO4)
• ozone

9
Removal of Synthetic Organic Chemicals

• Synthetic organic compounds (SOCs) include a
  large number of chemicals used in industrial,
  agricultural, and household activities.
• Some of the SOCs are toxic substances and can
  cause cancer or damage to vital organs, others
  can impair the nervous system. The maximum
  allowable level of SOCs in water range from
  0.0002 to 0.1 mg/l.

10
Sources of SOCs

• Surface waters can be polluted by SOCs through
  runoff from
• agricultural lands
• discharge of industrial wastewater
• spillage of chemicals

11
Treatment

• Conventional water treatment (coagulation -
  sedimentation - filtration) is not effective in
  removing SOCs.
• Other alternatives that can improve the treatment
  include
• changing the coagulants
• changing the polymers
• adjustment of pH
• use of activated carbon adsorption
• use of filtration through a bed of granular
  activated carbon

12
Treatment

• Granular activated carbon (GAC) can be
  reactivated by heating in a furnace.
• Pilot plant studies need to be conducted in order
  to
• select the best carbon
• determine the contact time
• determine the effect of water quality variation
• determine the effectiveness of reactivation

13
Sources of SOCs

• Groundwaters can be polluted by
• leaching of agricultural pesticides
• seepage from improper disposal of industrial
  volatile organic chemicals (VOCs)

14
Treatment of VOCs

• Air stripping in countercurrent packed towers and
  GAC adsorption are used to remove VOCs from
  groundwater.
• Air stripping may not be able to reduce the VOCs
  concentration to drinking water standards.
  Moreover, aeration is not feasible in cold
  climates due to ice formation on the tower
  packing.