DEPARTMENT OF CHEMISTRY
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
SUB:CHEMISTRY
B.Tech I year
COURSE CODE: CY0101
AUTHOR: Dr. P.KAMARAJ.
Course material – B.Tech
1.TECHNOLOGY OF WATER
INTRODUCTION
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Introduction…
• An adult needs to drink approximately 2 liters of water every day.
• Humans also use much larger amounts of freshwater (as opposed to the saltwater of oceans) for cooking, cleaning, industry, and agriculture. • Thus, the quality of the freshwater supply is important for virtually every aspect of our lives.
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
SOURCES OF WATER
• Surface water is water in a river, lake or fresh water wetland.
• Surface water is naturally replenished by precipitation and naturally lost through discharge to the oceans, evaporation, and sub‐surface seepage.
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Ground water
• Groundwater or Sub‐Surface water is fresh water located in the pore space of soil and rocks. • It is also water that is flowing within aquifers below the water table. Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
TYPES OF WATER BASED ON HARDNESS
• Hard Water
• Soft Water
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Hard water
• What is "Hard Water"?
Hard water is water that does not form lather readily with soap. It contains cations with a charge of +2, especially Ca2+ and Mg2+.
These ions do not pose any health threat, but they can engage in reactions that leave insoluble mineral deposits. Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Soft water
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What is soft water?
Soft water is water that forms lather readily with soap.
It is free from salts like CaSO4, MgSO4, Ca(HCO3)2, Mg(HCO3)2
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
TYPES OF HARDNESS
• Temporary hardness
• Permanent hardness
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Temporary hardness
• What is temporary hardness?
• The hardness of water which can be removed merely on boiling is called temporary hardness.
• This hardness is caused by carbonate salts like Ca(HCO3)2 and Mg(HCO3)2
• Water containing this hardness is called temporary hard water.
• It is also called carbonate hardness.
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Permanent hardness
• What is permanent hardness?
• The hardness of water which can not be removed by mere boiling is called permanent hardness.
• This type of hardness is caused by non‐carbonate salts like CaSO4, MgSO4, Ca(NO3)2, MgNO3 etc.
• The water containing this type of hardness is also called permanent hard water.
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Units of hardness
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How is hardness expressed?
Hardness is expressed in the following unit:
mg/L calcium carbonate equivalent parts per million
Clark degrees (°Clark) French degrees (°F) Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Calcium carbonate equivalent
• How is hardness expressed in calcium carbonate equivalent?
Wt. of hardness causing substance x Eq. wt. of CaCO3
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Hardness =
Equivalent wt of hardness causing substance Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Water quality parameters
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How do you measure water quality?
Water quality is measured using the following parameters:
Electrical conductivity Dissolved Oxygen pH Color of water Taste and odor (geosmin, 2‐methylisoborneol (MIB), etc) Turbidity Total suspended solids (TSS) Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Water quality parameters….
• Dissolved metals and salts (sodium, chloride, potassium, calcium, manganese, magnesium) • Chemical oxygen demand (COD) • Biochemical oxygen demand (BOD) Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Water quality parameters….
• Microorganisms such as fecal coliform bacteria (Escherichia coli), Cryptosporidium, and Giardia lamblia
• Nutrients, such as nitrogen and phosphorus • Dissolved metals and metalloids (lead, Mercury (element),arsenic, etc.) • Dissolved organics: Colored Dissolved Organic Matter (CDOM), Dissolved Organic Carbon (DOC) • Temperature • Pesticides • Heavy Metals • Pharmaceuticals Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Disadvantages of hardness
In domestic applications
• Washing
• Bathing
• Drinking
• Cleaning utensils
• Cooking
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Disadvantages of hard water • In Industrial applications
• Boiler feed water
• Water for sugar industries
• Water for paper industries
• Laundries
• Dyeing industries
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Determination of hardness
• Methods of determination of hardness
1. EDTA method
2. O’ Hehner’s method
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
EDTA METHOD
• Principle
• Ca2+ + EBT‐‐‐‐‐‐‐‐‐‐‐‐‐‐Æ[Ca2+ ‐ EBT]
• [Ca2+ _ EBT] + EDTA‐‐‐Æ [Ca2+ ‐ EDTA] + EBT
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
EDTA METHOD
• TITRATION 1
Standardisation of EDTA
• TITRATION 2
Determination of Total Hardness • TITRATION 3
Determination of Permanent Hardness
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Determination of Alkalinity in water
• 1.Phenolphthalein alkalinity
• 2.Methyl Orange alkalinity
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Scale • When the impurities in boiler are precipitated out of the water directly on heat transfer surfaces or when suspended matter in water settle out on the metal and become a hard and adherent deposit, it is called scale.
• Evaporation in a boiler causes impurities to concentrate. This interferes with heat transfers and may cause hot spots leading to local overheating. Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Causes of Scale
• What causes scale?
• Scaling is mainly due to the presence of calcium and magnesium salts (carbonates or sulphates), which are less soluble in hot conditions than in cold conditions
• It is also due to the presence of too high concentration of silica in relation to the alkalinity of the water in the boiler.
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Disadvantages of scale
• If the scales are not prevented or removed regularly they will cause localised overheating.
• This can lead to • tube failure (explosion risk) and/or a reduction in the heat transfer properties of the transfer surfaces. • reduced efficiency and increased energy costs. Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Removal of scale
• Hardness causing salts can either be removed before they enter the boiler system, using a water softener, reverse osmosis plant or de‐
alkalisation unit, or they can be treated inside the boiler itself.
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Sludge
• If the dissolved salts in the boiler water form a precipitate of loose and slimy nature and is suspended in the boiler water, the precipitate is called Sludge.
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Disadvantages of sludge
• Choking of pipes
• Waste of fuel
• Formation of scales
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Prevention of sludge formation
• Blow down operation
• Using softened water
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Other boiler troubles
• Priming and foaming
Priming is the carryover of varying amounts of droplets of water in the steam (foam and mist), which lowers the energy efficiency of the steam and leads to the deposit of salt crystals on the super heaters and in the turbines. caused by improper construction of boiler, excessive ratings, or sudden fluctuations in steam demand. Priming is sometimes aggravated by impurities in the boiler‐water. •
Foaming is the small persistent bubbles formed at the surface of the boiler water. The use of anti‐foaming and anti‐priming agents, mixtures of surface‐
active agents modify the surface tension of a liquid, remove foam and prevent the carry‐over of fine water particles in the steam.
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Other boiler troubles ……..
• Boiler corrosion
• Caustic embrittlement
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Methods of preventing boiler troubles
•Internal conditioning
•External treatment Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Internal conditioning
• Internal treatment
• Internal treatment is a treatment carried out when boilers operate at low or moderate pressure, when large amounts of condensed steam are used for feed water, or when good quality raw water is available. Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
The purpose of an internal treatment
• 1) To react with any feed‐water hardness and prevent it from precipitating on the boiler metal as scale
• 2) To condition any suspended matter such as hardness sludge or iron oxide in the boiler and make it non‐adherent to the boiler metal
• 3) To provide anti‐foam protection to allow a reasonable concentration of dissolved and suspended solids in the boiler water without foam carry‐over.
• 4) To eliminate oxygen from the water and provide enough alkalinity to prevent boiler corrosion. Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Internal conditioning methods
• Phosphate conditioning:
Phosphates or polyphosphates react with the alkaline boiler water and neutralize the hardness of water by forming tricalcium phosphate an insoluble compound that can be disposed on blow down operation on a continuous basis or periodically through the bottom of the boiler. • Anti‐foaming or anti‐priming agents:
mixture of surface‐active agents that modify the surface tension of a liquid, remove foam and prevent the carry over of fine water particles in the steam Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Internal conditioning methods…..
• Calgon conditioning
• Carbonate conditioning
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
External Treatment Methods
• Zeolite Process
• Ion‐exchange Process
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Zeolite Process
• What are zeolites?
• Zeolites are a group of hydrated crystalline aluminosilicates found in certain volcanic rocks. The tetrahedrally coordinated aluminum and silicon atoms form AlO4 and SiO4 tetrahedral groups. Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Zeolite Process
• What is zeolite process?
• It is a water softening process in which Ca2+ and Mg2+ ions present in water are exchanged with Na+ ions present in sodium zeolites. The water coming out of this process will be free from Calcium and Magnesium ions.
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Zeolite process
• To prepare a zeolite for water treatment, they are soaked in concentrated NaCl solution. • The cavities trap as many sodium ions as they can accommodate. • After the treatment, the zeolite is designated as Na‐zeolite. Then the salt solution is drained, and the zeolite is washed with water to eliminate the extra salt. When hard water flows through them, calcium and magnesium ions will be trapped by the Na‐zeolite. • For every Ca2+ or Mg2+ trapped, two Na+ ions are released. The treated water contains a rather high concentration of Na+
ions, but low concentrations of Mg2+ and Ca2+. Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Zeolite Process
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Ion‐Exchange Process
• What is ion exchange process?
• It is a water softening method in which anions (like Cl‐, SO42‐,HCO3‐ etc.) in water are exchanged with anions (OH‐) present in the anion exchange columm and cations (like Ca2+, Mg2+) in water are exchanged with cations (H+) present in the cation exchange column. Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Ion Exchange Process…
• What are ion exchange resins? • An ion exchange resin is an insoluble matrix normally in the form of small (1‐2 mm diameter) beads fabricated from an organic polymer substrate. • The material has highly developed structure of pores on the surface of which are sites with easily trapped and released ions. • The trapping of ions takes place only with simultaneous releasing of other ions. Hence, the process is called ion exchange process. Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Ion Exchange resins…
• Resins
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Ion exchange types
The most common synthetic structures are:
• Cross‐linked polystyrene • Cross‐linked polymethacrylate
• Phenol‐formaldehyde Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
The Ion‐Exchange Process
Cation Exchange Column
• Scheme
Anion Exchange Column
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Desalination
• Desalination refers to processes that remove excess salt and other minerals from water in order to obtain fresh water suitable for animal consumption or irrigation, or, if almost all of the salt is removed, for human consumption. Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Desalination Methods
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1.Electrodialysis
2.Reverse Osmosis
3.Distillation
4.Freezing
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Electrodialysis
• Electrodialysis is an electrically driven membrane separation process that is capable of separating, concentrating, and purifying selected ions from aqueous solutions (as well as some organic solvents). • The process is based on the property of ion exchange membranes to selectively reject anions or cations. • Electrodialysis can remove salts from food, dairy, and other products, waste streams and other solutions, as well as concentrate salts, acids or bases. The system is a useful tool to remove unwanted total dissolved solids that can build up in product streams.
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Electrodialysis
Electrodialysis cell
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Electrodialysis ‐
Advantages
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Electrodialysis has the following characteristics that lead it to various applications: Capability for high recovery (more product and less brine) Energy usage that is proportional to the salts removed Ability to treat water with a higher level of suspended solids than RO Lack of effect by non‐ionic substances such as silica Low chemical usage for pretreatment Electrodialysis units are normally used to desalinate brackish water
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Reverse Osmosis
• What is Osmosis?
• Osmosis may be described as the physical movement of a solvent through a semi‐
permeable membrane based on a difference in chemical potential between two solutions separated by that semi‐permeable membrane. Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Reverse Osmosis….
• What is reverse Osmosis?
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When two solutions of different concentrations are separated by a semi permeable membrane, and a pressure higher than that of osmotic pressure is applied on concentrated side, solvent molecules move from concentrated side to dilute side through the membrane. This phenomenon is called reverse osmosis.
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Advantages of reverse osmosis
• This method removes ionic, non‐ionic and colloidal impurities.
• Membrane replacement is easy.
Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Domestic Water Treatment
• Water purification is the process of removing contaminants from a raw water source . Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Steps involved in water purification
Part 1 Removal of suspended impurities
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1.Screening : The first step in purifying surface water is to remove large debris such as sticks, leaves, trash and other large particles which may interfere with subsequent purification steps. Most deep Groundwater do not need screening before other purification steps.
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2.Flocculation is a process in which we first clarify the water. Clarifying means removing any turbidity or colour so that the water is sparklingly clear and colourless.
Clarification is done by causing a precipitate to form in the water. Initially the precipitate forms as very small particles but as the water is gently stirred, these particles stick together to form bigger particles. We can say that the small particles coagulate. This process is sometimes called flocculation. Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Steps involved in water purification….
• 3.Sedimentation Water exiting the flocculation basin may enter the sedimentation basin, also called a clarifier or settling basin. It is a large tank with slow flow, allowing floc to settle to the bottom.
• 4. Filtration
• After separating most floc, the water is filtered as the final step to remove remaining suspended particles and unsettled floc. The most common type of filter is a rapid sand filter. Water moves vertically through sand which often has a layer of activated carbon above the sand. Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Steps involved in water purification…..
• Part 2 Disinfection
• Disinfection is normally the last step in purifying drinking water. Water is disinfected to kill any pathogens which pass through the filters. Possible pathogens include viruses, bacteria, including Escherichia coli, Campylobacter and Shigella, and protozoans, including G. lamblia and other Cryptosporidia. Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Steps involved in water purification…..
Methods of disinfection:
Boiling: Water is heated hot enough and long enough to inactivate or kill micro‐organisms that normally live in water at room temperature. • Chlorination is the process of adding the element chlorine to water as a method of water purification to make it fit for human consumption as drinking water.
Addition of bleaching powder
Chloramines are another chlorine‐based disinfectant.
• Ozonisation: Ozone (O3) is a relatively unstable molecule "free radical" of oxygen which readily gives up one atom of oxygen providing a powerful oxidising agent which is toxic to most water borne organisms. •
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Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University
Drinking water
• What would be the quality of water treated for drinking purpose?
• should be safe to use and aesthetically pleasing. • be clear and colourless, with no unpalatable taste or odour. • should contain no suspended matter, harmful chemical substances or pathogenic micro‐organisms. Prepared by DR.P.KAMARAJ, DR.M.ARTHANAREESWARI and MRS.S.DEVIKALA, Dept. of Chemistry,SRM University