Dissolved Oxygen

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Dissolved Oxygen

• WQT 134
• Environmental Chemistry II
• Dissolved Oxygen

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Key Words

• Dissolved Oxygen- The amount of oxygen in a
  sample. Impacted by flow rate, photosynthesis,
  aerobic respiration, elevation, clarity,
  temperature, sludge deposits, and water depth

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Dissolved Oxygen

• Temp Colder the water the more DO it can hold.
  As temp goes down DO goes up.

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Dissolved Oxygen

• Temp Warm turbid water will have low DO values.
  Wetlands

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Dissolved Oxygen

• Elevation At higher elevations, less oxygen can
  be dissolved in water. 

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Dissolved Oxygen

• Photosynthesis dissolved oxygen concentrations
  may be very low in the morning, and very high in
  the afternoon

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Dissolved Oxygen

• Flow rate Increased flow rate increased mixing
  of DO into the water.

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Dissolved Oxygen

• Sewage Increased sewage can lower DO in the
  water.

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Dissolved Oxygen

• Aquatic Health
• lt 5 mg/L DO poor for aquatic fish
• 10 mg/L ideal DO concentrations

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Langelier Saturation Index (LSI)

• Factoids
• Aggressive (corrosive) or scaling condition of
  water
• Online calculator
• Precipitate or Dissolve CaCO3
• Difference between pH of water and pH of CaCO3
• LSI pH (actual) pH (s)
• pH (actual) measured pH of water
• pH (s) theoretical pH at which the water will be
  saturated with calcium carbonate. Takes into
  account Ca ion , alkalinity, pH, Temp, and TDS
• LSI0 water is stable (rare)
• LSI CaCO3 will precipitate (scaling)
• 1 mild scale, 4 severe scale
• LSI - CaCO3 will dissolve (corrosion)
• -1 mild, -5 severe

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Langelier Saturation Index (LSI)
Saturation Index Description General Recommendation
- 5 Severe Corrosion Treatment Recommended
- 4 Severe Corrosion Treatment Recommended
- 3 ModerateCorrosion Treatment Recommended
- 2 Moderate Corrosion Treatment May Be Needed
-1 Mild Corrosion Treatment May Be Needed
-0.5 None- Mild Corrosion Probably No Treatment
0 Near Balanced No Treatment
0.5 Some Faint Coating Probably No Treatment
1 Mild Scale Coating Treatment May Be Needed
2 Mild to Moderate Coatings Treatment May Be Needed
3 Moderate Scale Forming Treatment Advisable
4 Severe Scale Forming Treatment Advisable
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Langelier Saturation Index (LSI)
Exercise Determine the Langelier index for a
water sample with the following characteristics,
using the Powell, Bacon and Lill diagram
Temperature 120oF, M-Alk 100 mg/L,
Ca-hardness 120 mg/L, pH 8, total dissolved
solids 210 mg/L.
LSI pH (actual) pH (s)
pH actual 8.0 7.32 .68 pH (s) pCa
2.92 pAlk2.7 C at 120o
1.7 pH(s) Sum 7.32
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Langelier Saturation Index (LSI)
1.7 C at 120o
2.92 PCa
2.70 P(Alk)
Hardness120 mg/L
P Alk100 mg/L
TDS210 mg/L