WATER TREATMENT TECHNOLOGY (TAS 3010) LECTURE NOTES 8 - Measurement Unit

8/9/2019 WATER TREATMENT TECHNOLOGY (TAS 3010) LECTURE NOTES 8 - Measurement Unit

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Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT

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1) Introduction

2) mg/L Unit

3) meq/L unit

4) Hardness & Alkalin

ity

Measurement Unit


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Introduction

- Water management begins with knowing the quantity of wateravailable

- Basic information on water measurement units and convenient

conversion factors.

- Conversion factors simplify changing from one unit of measurement toanother.

- There are two conditions under which water is measuredwater at

rest and water in motion. Water at rest is measured in units of volume.

Water in motion is measured in units of flow unit of volume for aconvenient time unit. It is important that the difference between a unit of

volume and a unit of flow be kept in mind.


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olume Units v/s Flow Units

Flow Units

Water in motion; i.e., flowing in streams,

canals, pipelines, and ditches, ismeasured in units of volume per unit of

timegallons per minute (gpm), cubic

meter per seconds(cms-cumec) cubic feet

per second (cfs-cusec), acre-inches per

hour and acre feet per day.

Volume Units

Water at rest; i.e., ponds, lakes,reservoirs, and in the soil, ismeasured in units of volume gallon, liter, cubic meter, cubicfoot, ha-m, square km-m, acre-inch, and acre-foot.


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mg/L = ppm (parts per million)

ppm = 1 part = 1 mg substance

106 part 106 mg water

Water density, p

p = 1000 kg = 103 g = 106mg = 1 lb water

m3 L L 10lb water

106mg of water = 1 L of water

1 ppm = 1 mg substance

1 L water

mg/L unit


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meq/L unit

- Measurement that involved in combination of several differentelement

- Equivalent mass = atomic or molecular mass (g) / valence

- Example :

- Atomic mass for Ca2+ = 40 g

- Valence = 2+

[valence] = 2

Equivalent mass for Ca2+ = Atomic mass/Valence

= 40/2

= 20

Meq/L = concentration ion mg/L x 1 / equivalent mass


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ardness & Alkalinity

- Mg/L as CaCO3 = meq/L x Equivalent mass for CaCO3

- Equivalent mass for CaCO3 :

Solution:

Equivalent mass of Ca2+ = 40/2 = 20

Equivalent mass of CO32- = 60/2 = 30

Equivalent mass for CaCO32- = 20 + 30 = 50

Equivalent mass of Ca2+ + Equivalent mass of CO32-


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Water Hardness

Water hardness is commonly defined as the sum of the

polyvalent cations dissolved in the water. The most common such cations are calcium and

magnesium, although iron, strontium, and manganese

may contribute . Therefore, Water hardness is an

expression for the sum of the calcium and magnesium

cation concentration in a water sample.

Hardness is usually reported as an equivalent quantity of

calcium carbonate (CaCO3).

Total hardness = Total meq/L Ca2+ and Mg2+ x Equivalent mass for CaCO3

Hardness (in mg/L) as CaCO3 = M2+ (mg/L) x (100 g/mol CaCO3/ atomic weight of M

2+ )


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Water Hardness - Category

Level of hardness Total hardness as mg/l CaCO3

soft 0-60 mg/l

moderately hard 61-120 mg/l

hard 121-180 mg/l

very hard >180 mg/l


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Solution

A sample of water was analyzed for common ions with the

result shown below:

HCO3

- = 300 mg/L

Na+ = 115 mg/L

SO4

2- = 240 mg/L

Mg2+ = 36.6 mg/L

Cl- = 71.0 mg/L

Ca2+ = 100 mg/L

1) Convert these concentration

from mg/L to meq/L

2) Construct a bar diagram inmiliequivalent per liter for this

water

3) Calculate the water hardness

in term of mg/L CaCO3

4) Categorized the strength of thewater hardness


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Solution

A sample of water was analyzed for common ions with the

result shown below:

HCO3

- = 300 mg/L

Na+ = 115 mg/L

SO4

2- = 240 mg/L

Mg2+ = 36.6 mg/L

Cl- = 109 mg/L

Ca2+ = 100 mg/L

1) Separate cation and anion

2) Tabulate the component,

equivalent mass and meq/L

3) Draw the bar diagram


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WATER TREATMENT TECHNOLOGY (TAS 3010) LECTURE NOTES 8 - Measurement Unit