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Surname 1
Students Name
Professors Name
Course
Date
Portable Water Treatment Operations
a) Addition of lime results into the following reaction equations:
CO2 + Ca(OH)2 CaCO3 + H2O
Ca(HCO3)2 + Ca(OH)2 2CaCO3 + 2H2O
Mg(HCO3)2 + Ca(OH)2 CaCO3 + MgCO3 + 2H2O
MgCO3 + Ca(OH)2 CaCO3 + Mg(OH)2
Na(HCO3) + Ca(OH)2 CaCO3 + NaOH + H2O
The above equations show that 1 kmol of CO2 needs 1 kmol of Ca(OH)2; 1 kmol of
Ca(HCO3)2 needs 1 kmol of Ca(OH)2; 1 kmol of Mg(HCO3)2 needs 2 kmol of Ca(OH)2; 1 kmol
of Na(HCO3) needs 1 kmol of Ca(OH)2.
Mg2+ has a concentration of 120 m/L
Molecular weight of Mg2+ = 24.3g/mole 24.3mg/mole
Valance (n) = 2 eq/mole Valance (n) = 2 meq/mole
Equivalent weight (EW) = MW Valance EW = 24.3 mg/mmole [1/2 meq/mole]
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Surname 2
EW = 12.15 mg/meq
Equivalent weight for CaCO3 found as below:
MW = 100 g/mole MW = 100 mg/mmole
Electrical charge (n) = 2eq/mole Electrical charge = 2 meq/mmole
EW = MW Electrical Charge EW = 100 mg/mmole (1/ meq/mmole)
Concentration of Mg2+ as CaCO3 is as shown below:
mg/L as CaCO3 = (mg/L as species) EW of CaCO3 EW of species
= (10 mg/Las Mg2+) 50mg/meq 12.15 mg/meq
= 41.15 mg/L as CaCO3
Quantity of CaO = 82.30 28 = 2.9 mg/L
Quantity of Na2CO3 = 82.30 106 = 0.776 gm/L
Component Mg/L EW mEW/L EW as CaCO3/EW ion
(mg/l)
Mg/L as CaCO3-
Ca2+ 120 20 6 2.5 299.67
Mg2+ 30 12.2 2.47 4.12 123.52
Na1+ 10 23.0 0.43 2.18 21.8
Cl1- 58 35.5 1.64 1.41 81.78
SO42- 10 48.0 0.20 1.04 10.42
HCO31- 428 61 7.03 0.8 342.4
Bar chart of raw water in mg/L as CaCO3
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Surname 3
0
Ca2+ Mg2+ Na1+
HCO31- Cl1- SO4
2-
0
To soften to the practical solubility limits, lime and soda must be added asshown below.Additionequal to:
Lime,mg/L as
CaCO3
Lime,mEW/L
Soda,mg/L as CaCO3
Soda,mEW/L
HCO3 -
Ca2+minus HCO3
Mg2+
Total
342.4
43.5
385.9
7.03
2.47
9.5
0
43.5
43.5
0.80
2.47
3.27
The difference between Mg2+ -0 = 43.5
The total lime addition is 385.9 + 43.5 + 35 = 464.4 mg/L as CaCO 3The soda addition is 43.5 mg/L as CaCO 3
b) Bar chart after reaction with HCO3 _(in mg/L as CaCO3 ).
Ca2+ Mg2+ Na1+
CO2-
HCO31-
Cl1-
SO42-
300
Bar chart after reaction of calcium with soda (in mg/L as CaCO 3 ).
300
342.4
423.6 445.4
424.18 434.58
0300
42 300
124.18 300
134.58 300
123.6 145.4
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Surname 4
c) The ionic balance
Sum of cations = sum of anions
175.6 = 175.6 mg/L as CaCO3
3.51 = 3.23 meq/L
All the above sums are ok as +- 10% range is allowed
Total Hardness = (Ca2+) + (Mg2+) = 99.8 + 41.2
= 141 mg/L as CaCO3
Alkalinity = (HCO3-) + (CO3
2-) + (OH-) (H+)
Since the pH = 10.8
H+ = 10-pH = 10-10.8 mole/L
H+ = 10-10.8 eq/L
OH- = 10-6.8 mole/L
From the table, HCO3- = 7.03 mEW/L
g/L of HCO3- = EW eq/L = (61 q/eq) 1.80 10-3g/L = 109.8 10-3 g/L
Quantity of CO2 = 1.33 10-6 mole/L = 79.8 10-6 g/L
d) Hypothetical bar graph for finished water
CH NCH
Ca(HCO3)2 CaSO4 MgSO4 Na2SO4 NaCl KCl
e) 30 minutes, the residence depth at 80% (best efficiency other than 100%) represents 1
meter.
CaCO3 in relation to the 1 meter depth will be 1.801 10-3 1000 50 = 90.1 mg/L
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