Suggested Response - Q5

**You are provided with two water reports. Source 1 and Source 2. The reports are as follows:

Compounds (mg/L)

Source 1

Source 2

Sodium

2

2

Magnesium

3

12

Calcium

7

3

Chloride

7

5

Sulphate

1

6

Bicarbonate

9

3

Nitrate

0

1

What is the hardness and residual alkalinity of each source?

Response:

The total hardness for Source 1 is:

Total Hardness as CaCO3 = (2.5 x Ca²+) + (4.12 x Mg²+)

Total Hardness as CaCO3 = (2.5 x 7) + (4.12 x 3) = 30 mg/L

The total hardness for Source 2 is:

Total Hardness as CaCO3 = (2.5 x Ca²+) + (4.12 x Mg²+)

Total Hardness as CaCO3 = (2.5 x 3) + (4.12 x 12) = 57 mg/L

The residual alkalinity for Source 1 is calculated as follows:

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RA = 7.47 – (5 + 1.76) = 0.71 mg/L.

Using the same method, source 2 has a residual alkalinity of -6.71 mg/L

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RA== 2.49 – (2.14 + 7.06) = -6.71 mg/L.

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