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ENGINEERING CHEMISTRY�Unit-I �Water Treatment

By

Prof. Attar M. N.

M.Sc ; Ph.D(Pursuing)

Assistant Professor

Yashoda Technical Campus, Satara

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Understand & Explain the basic concepts of water treatment.

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���Content�

  • Introduction
  • Sources of Water
  • Impurities in Water
  • Hard and Soft Water
  • Hardness of Water
  • Softening of Water

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INTRODUCTION:

  • IMPORTANCE OF WATER

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  • Living things are indeed in need of water.

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  • It cleanses our body.

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  • It energizes us every day.

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  • It keeps our body temperature at the right level.

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  • It is one of the essential resources for our health

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Distribution of Earths Water�

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  • Water is essential for the existence of human beings, animals and plants.
  • Though 80% of the earth’s surface is occupied with water, less than 1% of water is available for ready use.

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Distribution of Earths Water�

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Water quality �

Surface and ground water are normally used for industrial and domestic purposes. Hence undesirable impurities should be removed from these water.

Water treatment / water technology:

  • The process of removing all types of impurities from water and make it suitable for industrial and domestic purposes.

Water Parameters:

  • Hardness, alkalinity, total dissolved solids (TDS), dissolved oxygen (DO), colour, iron, chloride and turbidity.
  • Fluoride, sulphate, nitrate, nitrite, biochemical oxygen demand (BOD), chemical oxygen demand (COD) , metal ions – Mn, Pb, As.

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Sources of Water�

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Impurities in Water�

  • Any soluble, insoluble, biological, organic and inorganic substance present in water is termed as impurity in water.

1. Suspended Impurities

2. Colloidal Impurities

3. Dissolved Impurities

4. Biological Impurities

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Hard and Soft Water�

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  • Hard water: does not produce lather with soap solution, but produces white precipitate.

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  • Soft water: produces lather readily with soap solution.

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Hard and Soft Water�

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Disadvantages of� hard water�

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Difference between hard and soft water

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Hardness of water�

  • Hardness – The property or characteristics of water, which does not produce lather with soap.

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  • Detection of hardness
  • Hard water does not produce lather with soap solution and produces white scum.
  • Hard water gives wine red colour with Eriochrome Black-T indicator at pH 9 – 10.

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Types of Hardness

1. Temporary hardness (or) Carbonate hardness:

- due to the presence of bicarbonates of Ca and Mg.

- removed by boiling the water; adding lime to the water.

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2. Permanent hardness (or) Non-carbonate hardness:

- due to the presence of chlorides and sulphates of Ca and Mg.

- removed by i) lime soda process and ii) zeolite process.

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3. Total hardness – the sum of temporary hardness and permanent hardness.

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Units of hardness�

ppm – the number of parts by weight of CaCO3 equivalent hardness per million (106) parts of water.

mg/l – the number of milligrams of CaCO3 equivalent hardness per litre of water.

Grains per imperial gallon (gpg) or Clarke's degree (OCl)

French Degree (OF)

Milliequivalent per liter (meq/l)

The concentration of hardness producing salts is calculated as

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Mass of hardness producing salt x 50

Amount of equivalent of CaCO3 = --------------------------------------------------

Chemical equivalent of the hardness

producing substance

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Determination of hardness by EDTA method

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Water Characteristics�

  • Purpose
  • Quality requirements
  • Drinking
  • Edible, clear and free from colour, odor, turbidity and pathogens.
  • Domestic washing
  • Soft water producing lather readily.
  • Textile dyeing
  • Free from colour, turbidity, organic matter, Fe and Mn.
  • Boiler feed water
  • Free from dissolved salts, suspended impurities, silica and dissolved gases.
  • Drugs and pharmaceuticals
  • Soft and clear. Free from pathogens, colour, odor and suspended impurities.
  • Construction
  • Not too hard, should contain less of chlorides.
  • Paper industry
  • Free from colour, turbidity, organic matter, Fe, Mn, silica and alkalinity

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Softening of Water�

  • Water softening, also known as water conditioning, is a process that removes excess minerals from water sources

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  • Water softening removes ions like calcium, magnesium, and sometimes iron from water. These ions make it hard for products with other positively charged ions to dissolve in water.

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  • Processes
  • Zeolite or Permutit process
  • Demineralisation or Ion exchange process
  • Lime-soda process

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