Water Technology Lecture 2 PDF

AIAS Lecture 2 MODULE -1: Water Technology Introduction, Specifications and Hardness of water Dept. of Chemistry, AIAS, Amity University, Noida...

AIAS Lecture 2 MODULE -1: Water Technology Introduction, Specifications and Hardness of water Dept. of Chemistry, AIAS, Amity University, Noida 1  AIAS Contents: Introduction and specifications of Hardness and its determination Alkalinity water, (EDTA method only), Boiler feed water boiler problems – Scale, Sludge, Priming & Foaming Causes & Prevention, Water softening processes : Lime Caustic Embrittlement & – soda process, Zeolite, Ion Water for domestic use. Corrosion : Causes & Prevention, exchange method, Carbonate & Phosphate conditioning, Colloidal Conditioning & Calgon Treatment, 2  AIAS As a valuable natural resource, water is found in different forms in the environment. Through the water cycle, the movement of water in the environment and its management can be understood. To get fresh water is a major problem and it is not easy to get because fresh water is limited and vulnerable. Introduction Due to an increasing population, economic growth and climate change, water shortages are becoming a global issue,. A lack of clean, fresh water can hinder the efforts to reduce poverty and progress national development, resulting in poor health, low productivity, food insecurity and restricted economic development. 3  AIAS Water Cycle/Hydrological Cycle https://shodhganga.inflibnet.ac.in 4  AIAS Water Distribution on Earth https://shodhganga.inflibnet.ac.in 5  AIAS Table 1: Permissible limits of different Parameters: WHO (World Health Organization) BIS (Bureau of Indian Standards) https://shodhganga.inflibnet.ac.in 6  AIAS Surface water , groundwater and collected rainwater are our main sources of water for drinking, washing, agriculture and industry, all of which are dependent on rain and snow falling on the Earth’s surface. Sources Surface water It is located on top of the Earth's surface such as rivers, creeks, and of Water wetlands. This may also be referred to as blue water. The vast majority is produced by precipitation and water runoff from nearby areas. Rivers, streams, lakes, and ponds are widely used as water sources, especially in rural areas. The amount of available surface water depends largely on rainfall. When rainfall is limited, the supply of surface water will vary considerably between wet and dry seasons and also between years. 7  AIAS Sources Stream River Lake Pond of Water Domestic applications Industrial applications Reservoir Sea water Rain Ground Water 8  AIAS The water, which does not form lather with soap easily is called as hard water. Hardness of water is a measure of its capacity to precipitate soap. Hardness is caused mainly by the presence of calcium (Ca2+) and magnesium (Mg2+). Other multivalent cations also cause water hardness such as Fe3+, Sr2+, Zn2+, Hardness Mn2+. If Water is hard , Then calcium and magnesium salts react with soluble sodium of water soap to form insoluble salts of calcium and magnesium. 2C17H35COONa + CaSO4 −→ (C17H35COO)2Ca ↓ + Na2SO4 (sodium stearate) (insoluble salt) 2C17H35COONa + MgCl2 −→ (C17H35COO)2Mg ↓ + 2NaCl (sodium stearate) (insoluble salt) 9  AIAS Groundwater reaches the surface naturally through springs or artificially through wells. Springs typically rise up where the water table meets the land surface. Springs are important sources of water to feed streams and are attractive cultural and landscape Ground features in themselves. Wells and boreholes are dug by hand or drilled by machine. These have to be deep enough to extend below water and the water table so that water can be drawn up by bucket or by pumping. Rainwater Rainwater Rainwater is also an important source of water, although on a relatively small scale. Collecting rain from roofs or other hard- surfaced areas and storing it until it is needed can provide a valuable source of water for many purposes. 10  Hardness of Water AIAS Hardness – Concentration of multivalent cations like Ca and Mg. This includes Ca, Mg, Fe and other heavy metals Characteristics of hard water Hardness prevents the lathering of soap CaCl2 + 2Na-St → Ca-St ↓ + 2NaCl MgSO4 + 2Na-St → Mg-St ↓ + Na2SO4  Types of Hardness AIAS i. Temporary (carbonate) hardness ii. Permanent (non-carbonate) hardness. Temporary (Carbonate) Hardness Due to dissolved bicarbonates, carbonates and hydroxides of Ca, Mg, Fe and other heavy metals. (Alkaline Hardness). It can be easily removed by boiling the water heat Ca(HCO3)2 CaCO3↓ + H2O + CO2 heat Mg(HCO3)2 Mg(OH)2↓ + H2O + CO2  AIAS The reason for choosing CaCO3 as a standard for calculating hardness of water is due to: Hardness in Molecular weight of CaCO3 is 100 so calculation is easy. Moreover, it is insoluble in terms of water so it can be easily precipitated in water Calcium treatment process. Carbonate Equivalent of CaCO3 = Mass of the substance * Equivalents Equivalent wt. of CaCO3 /Equivalent wt. of the substance 13  AIAS 1) Parts /Million(ppm) : It is Parts of CaCO3 equivalent hardness per 106 parts of water. 2) Mg/Ltr: It is number of mgs of CaCO3 equivalent hardness present per litre of water. 1mg/L= 1mg of CaCO3 equivalent hardness /Ltr of water. Units of 1Ltr of water = 1000 gms. = 1000*1000 mgs 1mg/L = 1mg/ 106 mg = 1ppm. Hardness 3) Degree Clarke (0Cl) : It is parts of CaCO3 equivalent hardness per 70,000 parts of water. 4) Degree French (0Fr) : It is parts of CaCO3 equivalent hardness per 105 parts of water. 1ppm= 1mg/L= 0.1 0Fr = 0.07 0Cl 14  AIAS Calculate temporary and permanent hardness of water in 0Fr and 0Cl from the following water sample: Mg(HCO ) = 10.2 mg/L, 3 2 Mg(NO3)2= 20.8mg/L, MgSO4= 20 mg/L, CaCO3= 23 mg/L, KCl= 67 mg/L Solution: CaCO3 Equivalents of 1) Mg(HCO3)2= 10.2*50/73 =6.99mg/L, 2) Mg(NO3)2 =20.8 * 50/74 = 14.05mg/L, 3) MgSO4 = Numerical 20*50/60 = 16.67mg/L, 4) CaCO3= 23*50/50=23mg/L Total Hardness= 60.71 mg/L = 60.71*0.10Fr =6.0710Fr, 60.71 * 0.070Cl= 4.24970Cl Temporary Hardness = 6.99 + 23= 29.99mg/L= 2.999 0Fr, 0.20993 0Cl Permanent Hardness=Total hardness –Temporary hardness= 30.72 mg/L, 3.072 0Fr, 2.1504 0Cl 15  AIAS Hardness of water Concentration of multivalent cations like Ca, Mg Includes Fe, Zn and other heavy metal ions – Ca and Mg are the most common ions leathers with soap Doesn’t leather with soap  AIAS Types of Hardness Hardness Temporary Permanent Hardness Hardness (or) (or) Non- Carbonate Carbonate Hardness Hardness Difference between Temporary and AIAS Permanent hardness  AIAS Calculation Hardness Concentration of multivalent cations Calculated in CaCO3 equivalents 𝐻𝑎𝑟𝑑𝑛𝑒𝑠𝑠 = 𝑀𝑜𝑙. 𝑤𝑡. 𝑜𝑓 𝐶𝑎𝐶𝑂3 × 𝑀𝑎𝑠𝑠 𝑜𝑓 ℎ𝑎𝑟𝑑𝑛𝑒𝑠𝑠 𝑐𝑎𝑢𝑠𝑖𝑛𝑔 𝑠𝑢𝑏𝑠𝑡𝑎𝑛𝑐𝑒 𝑀𝑜𝑙. 𝑤𝑡. 𝑜𝑓 ℎ𝑎𝑟𝑑𝑛𝑒𝑠𝑠 𝑐𝑎𝑢𝑠𝑖𝑛𝑔 𝑠𝑢𝑏𝑠𝑡𝑎𝑛𝑐𝑒 in ppm CaCO3 Reasons for expressing hardness in CaCO3 equivalents, – It is the most common insoluble impurity in water. – Its molecular weight is 100.  AIAS Units of Hardness Hardness = [Ca2+] + [Mg2+] in CaCO3 equivalents Parts per million of hardness causing impurities in CaCO3 equivalents  Conversion of hardness causing AIAS impurities in to CaCO3 eq. 𝐻𝑎𝑟𝑑𝑛𝑒𝑠𝑠 = 𝑀𝑜𝑙. 𝑤𝑡. 𝑜𝑓 𝐶𝑎𝐶𝑂3 × 𝑀𝑎𝑠𝑠 𝑜𝑓 ℎ𝑎𝑟𝑑𝑛𝑒𝑠𝑠 𝑐𝑎𝑢𝑠𝑖𝑛𝑔 𝑠𝑢𝑏𝑠𝑡𝑎𝑛𝑐𝑒 𝑀𝑜𝑙. 𝑤𝑡. 𝑜𝑓 ℎ𝑎𝑟𝑑𝑛𝑒𝑠𝑠 𝑐𝑎𝑢𝑠𝑖𝑛𝑔 𝑠𝑢𝑏𝑠𝑡𝑎𝑛𝑐𝑒 A sample hard water contains, 9.1 mg/L Ca(HCO3)2 ; 8.5 mg/L Mg(HCO3)2; 14.6 mg/L CaSO4; 14.0 mg/L MgSO4 and 5.0 mg/L MgCl2. Calculate the temporary, permanent and total hardness.  AIAS Compound Mass Hardness MW Calculation C factor Conversion Hardness in ppm of (mg/L) (g) CaCO3 eq Ca(HCO3)2 9.1 162 100/162 (100/162) x 9.1 5.62 TH Mg(HCO3)2 8.5 146 100/146 (100/146) x 8.5 5.82 TH Temporary Hardness 11.44 CaSO4 14.6 136 100/136 (100/136) x 14.6 10.74 PH MgSO4 14 120 100/120 (100/120) x 14 11.67 PH MgCl2 5 95 100/95 (100/95) x 5 5.26 PH Permanent Hardness 27.67 Total hardness = Temporary Hardness + Permanent Hardness 11.44 + 27.67 = 39.11 mg/L (or) ppm CaCO3 eq.  AIAS Hardness Calculation 2) One litre of sample hard water contains, 27.3 mg Ca(HCO3)2 ; 5.9 mg CaSO4; 17.1 mg Mg(HCO3)2; 12.6 mg MgSO4 Total hardness = Temporary Hardness + Permanent Hardness 30 mg MgCl2. (20.89)28.56 +(93.06) 46.41 = (113.95)74.97 mg/L (or) ppm CaCO3 eq. 29 mg KCl Calculate the temporary, permanent and total hardness.  AIAS Hardness calculation 3) A sample hard water contains, 20.1 mg/L Ca(HCO3)2 ; 15.6 mg/L CaSO4; Total hardness = Temporary Hardness + Permanent 8.1 mg/L Mg(HCO3)2; Hardness 17.96 + 127.93 = 145.89 mg/L 100.6 g/mL MgSO4 (or) ppm CaCO3 eq. 0.031 g/L MgCl2. Calculate the temporary, permanent and total hardness.  AIAS 1. How can we make 1 litre of water with 700 ppm of CaCO3 equivalent hardness? 25  AIAS Eq wt of Mg(HCO3)2= 24+(1+12+48)*2=146/2=73 Eq wt of MgSO4= 24+32+64=120/2=60 Eq wt of Mg(NO3)2= 24+(14+48)*2= 148/2=74 Eq wt of CaCO3= 40+12+48=100/2=50 CaCO3 eq hardness of Mg(HCO3)2=10.2*50/73= CaCO3 eq hardness of Mg(NO3)2= 20.8* 50/74= CaCO3 eq hardness of CaCO3= 23*50/50= 23 CaCO3 eq hardness of MgSO4= 20*50/60= 26