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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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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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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