2PROPERTIES OF WATER We live on a planet that is dominated by water. Water has a very simple atomic structure.The atomic structure of a water molecule consists of two hydrogen (H) atoms joined to one oxygen (O) atom.The unique way in which the hydrogen atoms are attached to the oxygen atom causes one side of the molecule to have a negative charge and the area in the opposite direction to have a positive charge.The resulting polarity of charge causes molecules of water to be attracted to each other forming strong molecular bonds.
3Solid StateWhen water is frozen its molecules arrange themselves in a particular highly organized rigid geometric pattern that causes the mass of water to expand and to decrease in density.
4LIQUID STATEIn the liquid phase, water molecules arrange themselves into small groups of joined particles.The fact that these arrangements are small allows liquid water to move and flow
5GASEOUS STATEWater in the form of a gas is highly charged with energy. This high energy state causes the molecules to be always moving reducing the likelihood of bonds between individual molecules from forming.
7Physical Properties Molar Mass 18.015 Molar Volume 55.5 moles/liter Boiling Point100°C at 1 atmFreezing point0°C at 1 atmTriple pointK at 4.6 torrSurface Tension73 dynes/cm at 20°CVapor pressureatm at 20°CHeat of vaporization40.63 kJ/mol
8Physical Properties Heat of Fusion 6.013 kJ/mol Heat Capacity (cp) 4.22 kJ/kg.KDielectric Constant78.54 at 25°CViscosity1.002 centipoises at 20°CDensity1 g/ccDensity maxima4°CSpecific heat4180 J kg-1 K-1 ( T=293…373 K)Heat conductivity0.60 W m-1 K-1 (T=293 K)
9Physical Properties Melting heat 3.34 x 105 J/kg Evaporation heat Critical Temperature647 KCritical pressure22.1 x 106 PaSpeed of sound1480 m/s (T=293 K)
10POLARITY OF THE WATERBecause electrons are more attracted to the positively charged oxygen atom, the two hydrogen become slightly positively charged (they give away their negative charge) and the oxygen atom becomes negatively charged.
12WATER CHEMISTRY WHAT IS pH? pH represents the acidity or alkalinity of a solution, such as your lemon juice or soapy water.Neutral solution has a pH of 7. Any solution with a pH below 7 is acidic, and if the pH is above 7, then it's alkaline.
15THE STORY OF MICROBESMicrobes are the oldest form of life on Earth. Some types have existed for billions of years. These are single-cell organisms and invisible to the eye, but they can be seen with microscopes.Microbes live in the water you drink, the food you eat, and the air you breathe. Most microbes are helpful and some even essential.Billions more live naturally in our skin, mouth, nose, teeth, throat, and urethra. In fact, 95% of microbes are not harmful.The World of Microbes There are five types of microbes: bacteria, viruses, protozoans.
16BACTERIAThe most abundant organisms on Earth, bacteria live almost everywhere: in the soil and water, in plants and animals.They take the form of spheres, rods or spirals, bacteria consist of a single cell.Disease results, however, when bacteria multiply rapidly (each cell simply divides into two identical cells) and damage or kill human tissue, as in pneumonia and tuberculosis.Diseases can also produce toxins that damage or kill human tissue, as in food poisoning or cholera.Bacteria pictured clockwise from top: E. coli (causes food poisoning), Strepococcus pyrogenes (causes strep throat), Mycobacterium tuberculosis (causes tuberculosis)
17BACTERIA Bacteria are everywhere. These are the simplest of creatures that are considered to be alive.They are in the bread you eat, the soil that plants, even inside of you.Bacteria are small single cells sized about 0.5 – 2 micron (I micron = 1mm/1000)They reproduce by binary fission.
18Types of Microbes causing waterborne illness Bacteria: Diseases caused by water-borne bacteria include cholera and typhoid.
21What are viruses ?Viruses are very small particles which infect humans, animals, plantsand even bacteria.Virus particles (or virions) are unable to make copies of themselvesand they must infect a living host cell in order to make more copies ofthemselves.Viruses cause serious diseases in animals such as rabies and foot-andmouth disease.Viruses cause many serious human diseases such as hepatitis, polio,influenza and AIDS.Virus comes from the Latin word for poison.They can infect animals, plants, and even other microorganisms.Viruses that infect only bacteria are called bacteriophages.
22Sizes and Shapes of Viruses HELICAL VIRUS:A virus consisting of nucleic acid surrounded by a hollow protein cylinder or capsid and possessing a helical structure.POLYHEDRAL VIRUS:A virus consisting of nucleic acid surrounded by a hollow protein, multi-sided capsid. The most common polyhedral form is the icosahedron, a geometric form having 20 triangular faces, 30 edges, and 12 vertices.ENVELOPED VIRUS:A virus consisting of nucleic acid within either a helical or polyhedral core and surrounded by an envelope. The envelope is usually derived from a host cell membrane by budding.BINAL VIRUS:A virus that has neither helical nor polyhedral forms or has combinations of these forms. Formerly called complex.
23How big are viruses ?Viruses are very small. The virus which causes polio is 20 nanometers in diameter - that means that polioviruses laid out side by side would stretch for a mere one millimeter- about the width of a pinhead !!!The cells in your body which the poliovirus infects are 10 to 20 micrometers in diameter, one thousand times larger than the polio virus.Even though all viruses are far too small to be seen with the naked eye or even a modern light microscope scientists have been able to study viruses using powerful electron microscopes.1 metre = 1000 millimeters 1 millimetre = 1000 micrometers 1 micrometre = 1000 nanometers So 1 nanometre is 1/ th of a metre !!!
24Bacteriophages Bacteriophages are viruses that infect bacteria. Bacteriophage first discovered around 1915, have played a unique role in viral biology.Bacteriophages can have a protein "tail" attached to the capsid (protein coat that envelopes the genetic material), which is used to infect the host bacteria.When these viruses reproduce, they break open, or lyse, their host cells, resulting in the destruction of the host.The whole cycle can be complete in minutes depending on a variety of factors such as temperature.
25VIRUS MULTIPLICATIONViruses are intracellular obligate parasites which means that they cannot reproduce or express their genes without the help of a living cell.The multiplication process involves 4 stages, viz.Adsorption of a Bacteriophage to the Cell Wall of the BacteriumPenetration of the Viral Genome into the Cytoplasm of the BacteriumViral Replication and MaturationRelease of the Bacteriophages by Lysis of the Bacterium
26Adsorption of a Bacteriophage to the Cell Wall of the Bacterium Bacteriophage binding to the cell wall of a bacterium
27Penetration of the Viral Genome into the Cytoplasm of the Bacterium The bacteriophage injects its genome into the bacterium's cytoplasm
28Viral Replication and Maturation The viral genome directs the host cell's metabolic machinery (ribosomes, tRNA, nutrients, energy, enzymes, etc.) to synthesize viral enzymes and viral parts.The capsids assemble around the viral genomes as the viral tails assemble.
29Release of the Bacteriophages by Lysis of the Bacterium A bacteriophage-coded enzyme breaks down the peptidoglycan in the bacterial cell wall causing osmotic lysis
31Hepatitis A virusHepatitis A virus (HAV), is a small,unenveloped RNA virus.This virus transmitted by fecal-oral route by ingestion and intestinal infection.The virus then spreads by the bloodstream, to the liver, a target organ.Hepatitis A has an incubation period of about four weeks. The virus replicates in the liver. Relatively large quantities of virus are shed in the fecesIt causes mild illnesses in children to the full range of symptoms with jaundice in adults.The incubation period of hepatitis A is 3-5 weeks, with a mean of 28 days.Inactivated hepatitis A vaccines have been developed over the past decade and are now licensed in many countries.
32RotavirusesRotaviruses cause enteric disease with symptoms characterized by diarrhea, vomiting, abdominal discomfort, and fever, or any combination.The virus affects mainly infants and young children.Diarrhea ranges from mild to severe and can cause fatal dehydration.The 70-nm-diameter wheel-shaped particles.Transmission is by the fecal-oral route and damage the small intestine.
33POLIO VIRUS'Pico (Greek very small ) RNA Viruses with a simple spherical struture shown here in a 3D reconstruction based on electron microscope pictures and X-ray crystallography data.Viral poliomyelitis is now very rare in developed countries due to vaccination.Poliomyelitis as a viral disease was first recognised by Landsteiner and Popper, 1909.Polio enters its host via the oral route through contaminated water, food or saliva and replicates itself in the small intestine.In the absence of a strong immune response, the virus enters the blood stream and in about 1% of those infected the polio virus attacks the motor neurones and the central nervous system causing lifelong paralysis or death.Infectious polio virus is excreted in the faeces where it can spread to the sewage and water supplies.The Salk vaccine in contrast uses a preparation of killed polio virus which can not replicate in the host but is able to give rise to an immune response which will protect the host against a later polio virus infection.
34What can we do to limit the spread of viral diseases ? Improved standards of sanitation and the supply of clean drinking water can reduce the spread of viruses such as the polio virus which is shed from the body in faeces.Other viruses such as the influenza virus and rhinoviruses are spread by sneezing, such viral infections are much more likely to spread in overcrowded conditions.In animals and humans virus infected cells release proteins called interferons which make the cells around them more resistant to attack by viruses.When a cell is infected by a virus it displays virus proteins to cells of the immune system. The immune system is a collection of cells which work together to protect the body from harmful bacteria and viruses.Antibodies recognize specific viruses and prevent them attaching to cells.Vaccination aims to induce a strong T-cell (white blood cells) and B-cell (antibodies) response against viruses by using killed or attenuated (weakened) virus particles.
35What are viruses ?Viruses are very small particles which infect humans, animals, plantsand even bacteria.Virus particles (or virions) are unable to make copies of themselvesand they must infect a living host cell in order to make more copies ofthemselves.Viruses cause serious diseases in animals such as rabies and foot-andmouth disease.Viruses cause many serious human diseases such as hepatitis, polio,influenza and AIDS.Virus comes from the Latin word for poison.They can infect animals, plants, and even other microorganisms.Viruses that infect only bacteria are called bacteriophages.
36Sizes and Shapes of Viruses HELICAL VIRUS:A virus consisting of nucleic acid surrounded by a hollow protein cylinder or capsid and possessing a helical structure.POLYHEDRAL VIRUS:A virus consisting of nucleic acid surrounded by a hollow protein, multi-sided capsid. The most common polyhedral form is the icosahedron, a geometric form having 20 triangular faces, 30 edges, and 12 vertices.ENVELOPED VIRUS:A virus consisting of nucleic acid within either a helical or polyhedral core and surrounded by an envelope. The envelope is usually derived from a host cell membrane by budding.BINAL VIRUS:A virus that has neither helical nor polyhedral forms or has combinations of these forms. Formerly called complex.
37PROTOZOAProtozoa consist of a single cell that includes a nucleus. The cell also contains structures that carry out specific processes needed for life functions. A diverse and complex group, protozoa range through many shapes and sizes.They can be parasitic, needing to live within another organism, or free-living in moist habitats.The similarity of inner structures of protozoan and human cells makes it difficult to treat infections caused by protozoa. Drugs that may destroy the protozoan may also destroy human cells.Protozoan infections include amebic dysentery, malaria, and African sleeping sickness.Protozoa pictured clockwise from top: Giardia intestinalis (causes diarrhea), Trypanosoma brucei (causes sleeping sickness),Plasmodium gametocyte (causes malaria)
38Protozoa: Water-borne protozoa that cause disease include Amoeba, Giardia and Cryptosporidium. Its size ranges from 5 – 12 micron.
42How the disease Spreads? A person may be infected by drinking contaminated water, or by direct or hand-to-mouth transfer of the bacteria from feces or contaminated surfaces.
43What are the Symptoms?Human symptoms for water-borne illnesses range from fever and malaise to the better known gastro intestinal symptoms such as diarrhea and stomach aches.Most water-borne illnesses cause:Abdominal discomfortFeverVomitingDiarrheaSymptoms are more severe for people with weakened immune systems and can lead to death.
44What is the treatment?For most gastroenteritis is a self-limited disease of few days duration.The main risks are of dehydration and electrolyte imbalance.Maintaining a good hydration is the most important thing in gastroenteritis.There is generally treatment available for bacterial and protozoal infections but for viral its more symptomatic relief.For bacterial infection anti bacterial drugs can be given and for protozoal infections anti-protozoal drugs can be given.
45How to Prevent?Always wash your hands before handling food especially after using the toilet or handling pets or soil.Wash fruits and vegetables with clean water, especially if you plan to eat them raw.Avoid unpastuerized milk and dairy products.Cooking kills germs.Don’t drink water from lakes, rivers or pools.Water swallowed while swimming may contain harmful bacteria.Clean surfaces where diapers are changed after every use.More precautions are needed traveling to developing countries.Food and drinks, in particular raw fruits and vegetables maybe contaminated if not washed properly with pure water.
46Tests for Microbial quality of Drinking water? Coliform Test: It is more reliable for bacteria. Turbidity Test: It is more reliable for protozoa.