Treating Water and Wastewater with Lime

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Treating Water and Wastewaterwith Lime

• Kentucky Water and Waste Water Operators Show

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Waste Water TreatmentsIndustrial Waters

• 1. pH adjustment
• See alkali neutralization graph?

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Waste Water TreatmentsIndustrial Water

• 2. Coagulation/flocculation
• coagulation neutralization of the generally
  negatively charged particles
• flocculation formation of flocs
• In conjunction with Al or Fe salts, lime is
  used for coagulating suspended solids by
  maintaining the proper pH for most satisfactory
  coagulation conditions
• 3. Removal of phosphates, sulfates fluorides
• Precipitation of insoluble calcium salts
  that are readily recoverable
• ex 3 Ca(OH)2 2 H3PO4 ? Ca3(PO4)2 6 H2O

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Waste Water TreatmentsIndustrial water

• 4. Precipitation of metals
• Adjusting pH level of waste water to form
  insoluble metallic hydroxides Me(OH)x

Metal Aluminum Cadmium Chromium Cobalt Copper Iron
Lead Manganese Mercury Nickel Silver Zinc
Optimal pH zones for the precipitation of
different metals
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Waste Water TreatmentsMunicipal water

• Low lime treatment before biological treatment
  
• - removal of phosphates
• Odor control
• Most of the lime used in sludge treatment

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Drinking Water Treatment

• Drinking water strictly regulated
• One important parameter of the quality of water
  is its hardness or its lime / carbon dioxide
  equilibrium
• Ca(HCO3)2 ? CaCO3 H20 CO2
• Too soft water ? cardiovascular diseases
• Too hard water ? scaling problems, increased use
  of soap...

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Drinking Water Treatments1. Softening

• Purpose remove the carbonate hardness from the
  water
• 1. Prevent scaling in the pipes installations
• 2. Improve our living less scaling in the
  bathroom, less use of soap detergents
• Reaction
• Ca(HCO3)2 Ca(OH)2 ? CaCO3 precipitated H20
• Example Pellet reactor

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Drinking Water Treatments2. Remineralization3.
pH adjustment / coagulation

• Purpose increase the hardness of a too soft
  (corrosive) water
• - Protective coating on the inside of water mains
• Reaction
• H20 Ca(OH)2 2 CO2 ? H20 Ca(HCO3)2
• Purposes
• - Adjust pH to prepare for further treatment
• - Coagulation of suspended solids with alum (Al)
  or iron (Fe) salts
• - Facilitating sludge thickening

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Sludge Treatments

• Lime treatment
• Converts sludge in a usable product
• Really cost-effective option when the treated
  sludge is used on the lands

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Sludge Treatments

• BEFORE MECHANICAL Dewatering use of lime
• - Facilitates the dehydration process
• - Destroys pathogens (pH gt 12)
• - Destroys and prevents formation of odors
• - Precipitation of most metals reduction of
• their solubility and mobility
• AFTER MECHANICAL Dewatering use of quicklime
  CaO
• - Exothermic reaction pasteurization of the
  sludge
• - Higher solid content of waste easier handling
  and storage
• - Destruction of pathogens and limitation of the
  odors
• - Non negligible calcium supply