water

Water : Water By V.S.Saravanamani Asst.Prof/Chemistry Annapoorana Engg.College

UNIT I WATER TECHNOLOGY : UNIT I WATER TECHNOLOGY Characteristics – alkalinity – types of alkalinity and determination – hardness –types and estimation by EDTA method (problems); Domestic water treatment –disinfection methods (Chlorination, ozonation. UV treatment) – Boiler feed water– requirements – disadvantages of using hard water in boilers – internal conditioning (phosphate, calgon and carbonate conditioning methods) – external conditioning – demineralization process – desalination and reverse osmosis.

INTRODUCTION : INTRODUCTION H2O Natural Solvent Basic necessity of human’s life No life can exist without water Human body constitute two-third of water It also absolute essential for all other living things

SOURCES : SOURCES Rain water River water Ground water Sea water

Characteristics of water : Characteristics of water clear, colourless and odourless. cool and pleasant to taste. free from harmful bacteria and suspended impurities. free from dissolved gases like CO2, H2S, NH3, etc., and poisonous minerals like Pb, Sb, Mn, etc., cont..,

Slide 6 : Hardness should be less than 500 ppm. Cl content should be less than 250 ppm. Fl content should be less than 1.5 ppm. TDS should be less than 500 ppm. pH of the potable water should be 6.5 – 8.5.

Water quality parameters : Water quality parameters Physical parameters Chemical parameters Biological parameters

Physical Parameters : Physical Parameters Colour Odour Taste Turbidity

Chemical parameters : Chemical parameters Acidity Alkalinity Hardness Corrosiveness

Biological parameters : Biological parameters Bacteria Virus Fungi

Alkalinity : Alkalinity Alkalinity is caused by the presence of hydroxide, carbonate and bicarbonate Alkalinity or AT is a measure of the ability of a solution to neutralize acids to the equivalence point of carbonate or bicarbonate

Determination of Alkalinity : Determination of Alkalinity The alkalinity producing ions can be determined by titrimetry using standard acid and phenolphthalein and methyl orange as indicators. The determination is based on the following reactions. [OH-] + [H+]  H2O [CO32-] + [H+] ( HCO3- ) [HCO3-] + [H+]  H2O+CO2

Types of alkalinity : Types of alkalinity Hydroxide alkalinity ----- due to [OH-] alone Carbonate alkalinity ------due to [CO32-] alone Bicarbonate alkalinity --- due to [CO32-] alone Hydroxide & Carbonate --- [OH-] & [CO32-] Carbonate & Bicarbonate -- [CO32-] & [CO32-] No chance for all alkalinities

Slide 14 : Aim To estimate the type and amount of alkalinity present in the given water sample Principle Phenolphthalein end point OH¯ + H+ H2O CO32¯ + H+ HCO3¯ Methyl Orange end point HCO3¯ + H+ CO2 + H2O

Titre values and different alkalinities : Titre values and different alkalinities

Titration-IEstimation of Alkalinities : Titration-IEstimation of Alkalinities Burette Solution - HCl Pipette Solution - Alkaline water sample Indicator s - Phenolphthlein - Methyl orange Endpoints [P] - pink colour disappeared [M] - Appearance of pink colour

Hardness : Hardness “It is the chemical property of water which prevents lathering of soap solution” Which gives lather means “soft water” Which doesn’t lather means “hard water”

Types of hardness : Types of hardness Temporary hardness Permanent hardness

Temporary hardness : Temporary hardness “It is in the presence of bicarbonate of Ca and Mg ions in the water” Ex: Mg(HCO3)2 & Ca(HCO3)2 It can be removed by boiling water Ca (HCO3)2  CaCO3 ↓+ H2O + CO2 Mg (HCO3)2  Mg (OH)2↓+ H2O + CO2 by the addition of lime Ca(OH)2

Permanent hardness : Permanent hardness “It is in the presence of chlorides and sulphates of Ca and Mg ions in the water” Ex:CaSO4 , MgSO4,CaCl2,MgCl2 It can not be removed by simply boiling can be removed by Lime – Soda process Zeolite process

Slide 21 : Total Hardness The sum of temporary hardness and permanent hardness

Expression of Hardness : Expression of Hardness The concentration of hardness producing salts are usually expressed in terms of an equivalent amount of CaCO3. CaCO3 is chosen as a standard because Its molecular weight (100) and equivalent weight (50) is a whole number, so the calculations in water analysis can be simplified. It is the most insoluble salt, that can be precipitated in water treatment.

Units of Harndess : Units of Harndess Parts per million (ppm) Usually defined as one milligram of CaCO3 per litre of water or the no. of parts of CaCO3 equivalent hardness per 106 parts of water 1ppm = 1mg / lit

Estimation of hardness by EDTA method : Estimation of hardness by EDTA method EDTA Ethylene Diamine Tetra Acetic Acid.

Aim : Aim To estimate the amount of Total hardness, Permanent hardness and Temporary hardness present in the given water sample

Principle : Principle The amount of hardness causing ions. (Ca2 + and Mg2+) can be estimated by titrating the water sample against EDTA using Eriochrome Black- T (EBT) at a pH of 8 – 10. In order to maintain the pH, buffer solution (NH4Cl – NH4OH mixture) is added. Only at this pH such a complexation is possible. When the EBT indicator is added to the water sample, it forms wine red coloured weak complex, with Ca2+ and Mg2+ ions.

Titration-IStandardization of EDTA : Titration-IStandardization of EDTA Burette Solution - EDTA Pipette Solution - Std.Hard water Reagents Added - 5ml Ammonia Buffer Indicator - EBT Endpoint - wine red to steel blue

Titration-IIEstimation of Total hardness : Titration-IIEstimation of Total hardness Burette Solution - EDTA Pipette Solution - Sample Hard water Reagents Added - 5ml Ammonia Buffer Indicator - EBT Endpoint - wine red to steel blue

Titration-IIIEstimation of Permanent hardness : Titration-IIIEstimation of Permanent hardness Burette Solution - EDTA Pipette Solution - Boiled and filtered Sample Hard water Reagents Added - 5ml Ammonia Buffer Indicator - EBT Endpoint - wine red to steel blue

CalculationTITRATION-I Standardization of EDTA : CalculationTITRATION-I Standardization of EDTA 1 ml of standard hard water = 1 mg of CaCO3 eq Volume of std hard water = 50ml = 50 mg of CaCO3 eq Volume of EDTA = V1 ml V1 ml of EDTA = 50mg of CaCO3 eq 1 ml of EDTA = 50/V1 mg of CaCO3 eq

Titration-II Estimation of Total hardness : Titration-II Estimation of Total hardness 1 ml of EDTA = 50/V1 mg of CaCO3 eq Volume of sample hard water = 50 ml Volume of EDTA = V2 ml = V2 (50/V1) mg of CaCO3 eq 50 ml of sample hard water = V2 (50/V1) mg of CaCO3 eq 1000 ml of sample hard water = (V2/V1) X 1000 mg of CaCO3 eq Total hardness =(V2/V1) X 1000 mg of CaCO3 eq

Titration-II Estimation of Permanent hardness : Titration-II Estimation of Permanent hardness 1 ml of EDTA = 50/V1 mg of CaCO3 eq Volume of sample hard water (BF) = 50 ml Volume of EDTA = V3 ml = V3 (50/V1) mg of CaCO3 eq 50 ml of sample hard water (BF) = V3 (50/V1) mg of CaCO3 eq 1000 ml of sample hard water (BF) = (V3/V1) X 1000 mg of CaCO3 eq Total hardness =(V2/V1) X 1000 mg of CaCO3 eq

Estimation of Temporary hardness : Estimation of Temporary hardness TEMPORARY HARDNESS Temporary Hardness = Total hardness – Permanent hardness

Domestic Water Treatment : Domestic Water Treatment Requisites of drinking water The water should be clear, colourless and odourless The water should be free from dissolved gases such as CO2, H2S etc., The water should be free from pathogenic (disease – producing) micro-organisms. The water should not be excessively hard or soft. The recommended maximum concentration of hardness is 125 ppm.

Slide 35 : The pH of the drinking water must be 7.0 – 8.5. The turbidity in drinking water should not exceed 25 ppm. The recommended maximum concentration of total dissolved solid in drinking water should be 500 ppm

Purification or Treatment of water for Municipal supply : Purification or Treatment of water for Municipal supply Screening Aeration Sedimentation and Coagulation. Filtration Sterilization and Disinfection Storage and distribution

Slide 37 : Screening It is a process of removing the floating materials like, leaves, wood pieces etc., from water. The raw water is allowed to pass through a screen, having large number of holes which retains the floating materials and allows the water to pass.

Slide 38 : Aeration Aeration of water promotes taste and odour by exchange of gases between the water and atmosphere. The main purpose of aeration is To add or increase the content of oxygen in water. To remove CO2, H2S and other volatile substances causing bad taste and odour in water. To remove the impurities like Fe and Mn (which are precipitated as their respective Ferrric and Mangenic hydroxides or other salts.

Slide 39 : Sedimentation with Coagulation The suspended and colloidal impurities which can settle at the bottom are separated in a sedimentation tank by gravitation. The main principle of sedimentation is to allow water to rest or flow at a very slow velocity (for 2 to 6 hrs.) so that the heavier particles settle down due to gravity. Sedimentation removes only 75% of the suspended impurities

Slide 40 : Coagulation However fine particles like clay, silica, etc., take many hours or sometimes days to settle down. So certain chemicals are added to aid sedimentation. This process is called coagulation. The common coagulants (chemicals) used are generally salts of aluminium. (alum {K2SO4.Al2(SO4)3.24H2O} Sodium aluminate NaAlO2 and salts of iron (Ferrous sulphate, ferric sulphate, ferric chloride).

Slide 41 : Filtration It is the process of removing bacteria, colour, taste, odour and suspended particles, etc., by passing the water through filter beds containing free sand, coarse sand and gravel

Slide 42 : Sterilisation or Disinfection The process of destroying / killing the disease producing bacteria, micro- organisms, etc., from the water and making it safe for use, is called disinfection. The chemicals or substances, which are added to water for killing the bacteria, etc., are known as disinfectants.