Introduction What is the goal of Water Treatment Technologies? To remove 1) Turbidity 2) Chemicals 3) Pathogenic Contaminants from water sources in the most affordable and expedient manner possible.

Impurities in Water 1) Dissolved Impurities :- carbonates and bicarbonates, chlorides, magnesium, iron, dissolved gases 2) Suspended Impurities :- Organic :- oil globules, vegetable and animal matter Inorganic :- clay and sand 3) Colloidal Impurities :- finely divided silica and clay, organic waste products, amino acids 4) Micro organisms :- fungi and bacteria

Methods for removal of impurities Screening Sedimentation Coagulation Filtration Sterilization :- 1) by Chlorine or Bleaching Powder 2) by UV Radiation 3) by Ozone

Boiler Feed Water One of the chief use of water is generation of steam by boilers. Essential requirements of Boiler Feed Water :- It should be free from - Turbidity, oil, dissolved salts - Hardness & scale forming constituents - Dissolved O2 & CO2 - Caustic alkali

If hard Water is directly fed into boiler there arise many problems such as - Priming - Foaming - Sludge & Scale Formation - Caustic Embrittlement

Priming : The process of formation of Wet Steam is called Priming. Because of priming efficiency and life of machine parts decrease. It is caused by - Very high water level - Presence of foam on the surface - High steam velocity

Foaming : Formation of stable bubbles above the surface of water is called foaming. These bubbles are carried over by steam leading to excessive priming. It is caused by presence of soluble impurities like alkali metal salts and oil. Foaming can be controlled by action of anti foaming agents like synthetic polyamides

Sludge and Scale formation :

Sludge Scale Sludges are soft and non- adherent deposits. Scales are hard deposits which stick very firmly to the inner surface of boiler. 2. Sludges can be removed easily. 2. Scales are very difficult to remove. 3. Sludges can transfer heat to some extent and is less dangerous. 3. Scales are bad conductors of heat and are more dangerous. 4. Sludges are formed by substances like MgCl2 and CaCl2. 4. Scales are formed by substances like CaSO4 and Mg(OH)2.

Caustic Embrittlement : It is the phenomenon during which the boiler material becomes brittle. Na2CO3 present in water breaks up and give NaOH and water become alkaline. This alkali boiler water flows into cracks by capillary action. There the water evaporates and concentration of caustic soda increases. This leads to failure of boiler. It can be avoided by using sodium phosphate as a softening reagent instead of Na2CO3 and adding tannin or lignin to boiler water which blocks the cracks.