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Download Fundamental properties of water and Methods of Purification
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Fundamental properties of water and Methods of Purification Presented by: Becky Lacey Water purification specialist Content History of Water Where it comes from Impurities Variations around the country Methods of water purification Summary Useful terminology History of Water • The Indus Civilisation, which produced the first cities around 2500BC, also built the first sewers. They even had man hole covers so they could be cleaned and unblocked • Jerusalem in the 7th Century BC was supplied by a man-made underground water tunnel which led from a protected spring outside the walls History of Water • The Roman Empire was famous for building aqueducts to bring water to its cities. Everyday the people of Rome used more than 1000 million litres of water for all uses including fountains and baths. Few homes had piped water though. People carried their waste to sewage disposal points, which led to the Greater sewer or Cloaca Maxima History of Water • The Inca Empire provided homes for about 12 million people. To keep people healthy a stone channel ran down each street in the main city carrying fresh water from the mountains, ready to flush away sewage • The Ashanti Kingdom in 18th century West Africa was very clean. Buildings in the capital had sewage pipes cleaned on a daily basis with boiling water and remote villages had public toilets History of Water In the UK • • • 1300 – 1600 – Lead pipes were laid, various methods employed to transport water to cities and towns around the country. By the end of the 1500’s filtration water started to take place. 1600 – 1800 – The first flushing toilets were designed and introduced. 1800 – 1900 – Mechanical and sand filtration were perfected. 1847 it was a criminal offence to pollute drinking water. 1852 The General Board of Health recommended new sewers in every town. Between 1832 – 1847 there were Cholera Epidemics which lead to 1858 – The year of the “Great Stink” seeing the recommendation of 1852 carried out. 1885 water was checked fro bacteria for the first time. Reservoirs were built around the country. History of Water In the UK • 1900 – present day The routine way to treat water was to: Screen to catch branches, solids and dead animals, treat it with aluminium sulphate to remove solids and chlorinate against bacteria. 1945 the Water Act reorganised the water industry. 1973 the water bill for England and Wales created 10 Regional Water Authorities. 1989 The Water Act allowed local authorities to sell off the water companies Water Companies • • • • • • • • Anglian Water Bournemouth and West Hampshire Water Hampshire Water Bristol Water Cambridge Water Cholderton and District Water Dee Valley Water Dwr Cymru (Welsh Water) • • • • • • • • Essex and Suffolk Water Folkstone and Dover Water Mid Kent Water Northumbrian Water Portsmouth Water Scottish Water Severn Trent Water South Staffordshire Water South East Water Definition of water The chemical symbol for water is H2O Definition of water The chemical symbol for water is H2O As a chemical it is defined as Dihydrogen Oxide and therefore it is a binary compound that occurs at room temperature as a clear, colourless, odourless liquid. Dihydrogen Oxide freezes at 0°C and boils at 100 °C At atmospheric temperatures and pressures it can exist in all three of it’s phases: Solid (Ice) Liquid (Water) Gaseous (Water vapour / steam) The Water Cycle 1 = Precipitation 2 = Condensation 3 = Transpiration 4 = Evaporation 5 = Surface run off Impurities of Water • In solution • In suspension • Gases Impurities in Solution An Inorganic compound is any substance in which two or more chemical elements other than carbon are combined. Picture = Calcium carbonate crystals Organic compound are substances whose molecules contain one or more (often many more) carbon atoms Impurities in Suspension Colloids are substances inorganic or organic which are finely dispersed throughout the liquid medium of water. Particle size is usually between 1100nm. Living matter which will include any plant, animal or bacteria Gases Carbon Dioxide - CO2 Oxygen - O2 Sulphur Dioxide – SO2 Chlorine – Cl2 Water Sources for England and Wales Prescribed Concentration or Value (PCV) Substance Standard Microbiological parameters Amount Allowed Faecal coliforms, faecal streptococci, Clostridium perfringens 0 per 100 ml Substance Standard Amount Allowed Chloride 400 mg/l Chlorine No standard Chromium 50 µg/l Colour 20 mg/lPt/Co scale Total coliforms 0 per 100 ml Chemical parameters Amount Allowed Alkalinity No standard Conductivity 1500 µS/cm Aluminium 200 µg/l Copper 3000 µg/l Ammonium 0.5 mg/l Cyanide 50 µg/l Antimony 10 µg/l Fluoride 1500 µg/l Arsenic 50 µg/l Iron 200 µg/l Barium 1000 µg/l Lead 50 µg/l Boron 2000 µg/l Magnesium 50 mg/l Cadmium 5 µg/l Manganese 50 µg/l Mercury 1 µg/l Nickel 50 µg/l Calcium 250 mg/l Prescribed Concentration or Value (PCV) Substance Standard Substance Amount Allowed Nitrate 50 mg/l Nitrite 0.1 mg/l Oxidisability 5 mg/l PAH 0.2 µg/l Benzo3,4 pyrene (a PAH) 10 ng/l Pesticides Standard Amount Allowed Sulphate 250 mg/l Surfactants 200 µg/l Temperature 25 C Tetrachloroethene 10 µg/l 0.1 µg/l Tetrachloromethane 3 µg/l PH 5.5-9.5 Trichlorethene 30 µg/l Phosphorus 2200 µg/l Trihalomethanes (THMs) 100 µg/l Potassium 12 mg/l Turbidity 4 Formazin Turbidity Units Qualitative odour and taste No standard Total dried solids 1500 mg/l Quantitative odour and taste Dilution No of 3 at 25ºC Total hardness No standard Selenium 10 µg/l No significant increase Silver 10 µg/l Total organic carbon (TOC) Sodium 150 mg/l Zinc 5000 µg/l Definition of water Conductivity (μS/cm) Total Dissolved Solids (TDS) (ppm or mg/l) Resistivity (MΩ-cm) pH Hardness Fouling Index (silt density) Purification Technologies Distillation Heat water to boiling Condense water vapour Collect condensate(liquid) In separate container Purification Technologies Ion – Exchange (DeI) Chemical exchange process Works only with elements in a charged state Once exhausted can be regenerated Instantaneous demand Good food source for bacteria Purification Technologies Reverse Osmosis (RO) Sophisticated filtration Physical removal Requires pressure 93-98% removal of minerals 99% Bacteria Purification Technologies Filtration Physical removal based on particle size Removal of particles 0.2µm filter size removes bacteria (ultra – microfilters) 0.1 – 0.01µm filter size removes endotoxin (ultra-filtration) Purification Technologies Ultra violet irradiation (UV) Short wavelength energy Breaks C-C bonds 185nm - Small chain organic molecules 254nm - Bacteria Purification Technologies Organic Adsorbtion Concentration of organic molecules at the surface of usually activated carbon media sometimes man made resins Low molecular weight organics 185nm - Small chain organic molecules 254nm - Bacteria Technologies Distillation Resistivity Conductivity Hardness Heavy Metals Silica pH Total Organic Carbon Micro-organisms Endotoxins Particles / colloids Reverse Osmosis Deionisation Organic Adsorbtion Filtration Ultrafiltration UV Market sector Parameter Clean Steam Micro Electronics <35 _ _ 18.2 TDS (ppm) 30 _ Hardness (ppm) _ _ 0.1 0.05 _ 5 _ 0.05 - 1 Renal Conductivity (µS-cm) USP Pharma Laboratory Clinical <1.29 Resistivity (MW/cm) 1 to 10 Heavy Metals (ppm) 1 to 10 0.1 TOC (ppb) <500 <50 <50 Particles (µm) Chlorine/Chloramines (mg/l) <0.1 0.01 Calcium (mg/l) <2 0.005 Nitrate/nitrite (mg/l) <2 0.2 0.01 <0.01 0.01 0.005 Aluminium (mg/l) Silica (ppb) Bacteria (cfu/100ml) <100 <100/ml no P aeruginosa or E Coli Endotoxins (Eu/ml) <0.03 <0.25 <100 depends 50 10 3 <10/ml _ 1 0.25 0.03 Quotations for Water If there is magic on the planet, it is contained in the water. - Loren Eisley When the well is dry, we know the worth of water. - Benjamin Franklin Thank you for your attention Useful Terminology • Potable water – Water suitable for drinking • Hardness – The scale - forming and lathering inhibiting qualities which some water supplies possess caused by high concentrations of calcium and magnesium • Conductivity – The process of electrical transfer through water, measured in microsiemens/cm. • Resistivity – The reciprocal of conductivity. Resistivity is usually corrected to 25 degrees centigrade and expressed as megohm-cm. 1megohm-cm is equivalent to 1 microsiemen/cm Useful Terminology • pH – A measure of the acidity or alkalinity of a solution. pH1 is very acid pH7 is neutral and pH14 is very basic. pH is measured using a glass electrode. • OA – Oxygen Absorbed is a measure of organic content of water. The water is reacted with acidified potassium permanganate and the permanganate consumed is used to quantify the organics present with the result being expressed in ppm O2 • SDI – Silt Density Index, also called Fouling Index (FI), a test used to estimate the concentration of colloids in water; derived from the rate of blockage of a 0.45 micron filter Useful Terminology • Bacteria – Also known as Microorganisms are some of the simplest living cells known usually found as single cells living “alone” or in groups as chains or clumps of cells. Cell size varies from 0.5 10 micron. • Colloid – A stable dispersion of fine particles in water that have a typical size less than 0.1 micron. Colloids containing iron (Fe), aluminium (Al), silica (SiO2) and organics are commonly found in water. • Total Dissolved Solids – A measure of the total of organic and inorganic salts dissolved in water, obtained by drying residue at 180ºC. • PPM – parts per million is a unit equal to milligram per kilogram of water, ppm is equivalent to mg/l in dilute solutions. Useful Terminology • Ion – Any non aggregated particle of less than colloidal size possessing either a positive or a negative electric charge. Some organic molecules are so large that even as ions they are considered to be colloids. • Cation – A positively charged ion • Anion – A negatively charged ion • Molecule – The smallest particle of an element or compound that is capable of separate existence without losing the properties of the substance.
