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What is LS and how does it work?
Lime Softening
Removes hardness by precipitating it out of solution
Lime
Ca(OH)
2
Quicklime
CaO
Three reactions used in lime softening
1. Ca(HCO
3
)
2
+Ca(OH)
2
-->2CaCO
3(s)
+2H
2
O
2. Mg(HCO
3
)
2
+2Ca(OH)
2
-->2CaCO
3(s)
+Mg(OH)
2
(s)
2H
2
O
3. MgSO
4
+Ca(OH)
2
+Na
2
CO
3
-->Mg(OH)
2(s)
+CaCO
3(s)
+Na
2
SO
4
What process is used to remove permanent hardness?
Lime-Soda Softening
CLS
Cold Lime Softening
WLS
Warm Lime Softening
HLS
Hot Lime Softening
How do you remove silica from water?
MagOx process. Add MgO to LS unit, silica will become trapped in heavy sludge blanket
IX
Ion Exchange
How does IX work?
Water passes through a packed cartridge that replaces hard ions with soft ions
Types of ion exchange resins
-Anionic
-Cationic
-Neutral
Classes of ion exchange resins
-SAC (Strong acid cation)
-WAC (Weak acid cation)
-SBA (Strong base anion)
WBA (Weak base anion)
RO
Reverse osmosis
How does RO work?
Pressure is applied to the concentrated water, which is then forced through a membrane. Contaminents are left behind.
Permeate
Treated water
RO Parameters
Pore size - determines which TDS can be removed by RO
Flow rates - lower flow rates more efficient
Pressure - variable depending on application/membrane
Surface area - bigger SA is more efficient
NF
Nanofiltration
UF
Ultrafiltration
In what order are these units placed in a water treatment plant?
WLS-->IX-->NF/UF-->RO
Author
saitclt
ID
189028
Card Set
ENVS348 Review
Description
Unit Operations
Updated
2012-12-12T18:04:21Z
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