Chemistry of Water PDF

CHEMISTRY OF THE WATER WHAT IS WATER? ✓ A clear, colorless, odorless, and tasteless liquid essential for most plant and animal life. ✓ Under nomenclature used to name chemical compounds, H2O scientific name is pronounced as dihydrogen monoxide, though it is not almost never used. ✓ W...

CHEMISTRY OF THE WATER WHAT IS WATER? ✓ A clear, colorless, odorless, and tasteless liquid essential for most plant and animal life. ✓ Under nomenclature used to name chemical compounds, H2O scientific name is pronounced as dihydrogen monoxide, though it is not almost never used. ✓ Water is LIQUID at standard temperature and pressure. The intrinsic color of water and ice is a very slight blue hue, although appear colorless in small quantities. Water is essentially invisible as a GAS. ✓ Water is a good solvent and is often referred to as the universal solvent. ✓ Substances that dissolve in water, e.g. salts, sugars, acids, alkalis, and some gases – especially oxygen, carbon dioxide (carbonation) are known as hydrophilic (water-loving) substances, while those that do not mix well with water, (e.g. fats and oils) are known as hydrophobic (water-fearing) substances. ✓ The boiling point of water (and all other liquids) is dependent on the barometric pressure. ✓ (On the top of Mt. Everest water boils at 68 °C, compared to 100 °C at sea level) ✓ Conversely, water deep in the ocean near geothermal vents can reach temperatures of hundreds of degrees and remain liquid. ✓ The maximum density of water occurs at 3.98 °C. ✓ It has the anomalous property of becoming less dense, not more, when it is cooled down to its solid form, ice. ✓ It expands to occupy 9% greater volume in this solid state, which accounts for the fact of ice floating on liquid water, as in icebergs. WATER TRIVIA AND FACTS ENGR. JONAYKA T. AZARIAS Page 1  CHEMISTRY OF THE WATER ✓ Only 3% of Earth’s water is fresh water, 97% is salt water. ✓ Over 90% of the world's supply of fresh water is located in Antarctica. ✓ The total amount of water in the body of an average adult is 37 liters. ✓ Human brains are 75% water. ✓ A person can live about a month without food, but only about a week without water. If a human does not absorb enough water dehydration is the result. ✓ Hot water weighs more than cold water. ✓ Frogs do not need to drink water as they absorb the water through their skin. ✓ Although Mount Everest, at 29,028 feet, is often called the tallest mountain on Earth, Mauna Kea, an inactive volcano on the island of Hawaii, is actually taller. Only 13,796 feet of Mauna Kea stands above sea level, yet it is 33,465 feet tall if measured from the ocean floor to its summit. ✓ Water is the only substance that is found naturally on earth in three forms: liquid, gas, solid. ✓ In a 100-year period, a water molecule spends 98 years in the ocean, 20 months as ice, about 2 weeks in lakes and rivers, and less than a week in the atmosphere. HYDROLOGY AND HYDROLOGICAL CYCLE HYDROLOGY ✓ The study of water and its movement along its various pathways within the hydrological cycle. ✓ It is applied by engineers who use hydrological principles to compute river flows from rainfall, water movement in soils from knowledge of soil characteristics, evaporation rates from water balance or energy balance techniques. HYDROLOGICAL CYLCE ✓ The hydrological cycle is central to hydrology. ✓ As shown, water evaporates from the earth’s oceans and water bodies and from land surfaces. (About seven times more evaporation occurs from oceans than from the earth’s land surfaces). ✓ The evaporated water rises into the atmosphere until the lower temperatures aloft cause it to condense and then precipitate in the form most globally as rain but sometimes as snow. ENGR. JONAYKA T. AZARIAS Page 2  CHEMISTRY OF THE WATER ✓ Once on the earth’s surface, water flows into streams, lakes, and eventually discharge into surface waters. ✓ Through evaporation from surface waters or transpiration from plants, water molecules return to the atmosphere to repeat the cycle. The term evapotranspiration is used referring to combined evaporation and transpiration. ✓ Transpiration - the process where water contained in liquid form in plants is converted to vapor and released to the atmosphere. Much of the water taken up by plants is released through transpiration. ✓ In general, of 100 units of rain that falls on grassland in temperate zones, 10 to 20 units will go to groundwater, 20 to 40 units will transpire and 40 to 70 units will become stream runoff. WATER QUALITY AND ITS PARAMETERS ✓ Water in nature is most nearly pure in its evaporation state, however, it acquires impurities once condensed and additional impurities are added as the liquid water travels through the remainder of the hydrologic cycle and comes into contact with materials in the air and on or beneath the earth’s surface. ✓ In addition, human activities contribute further impurities in the form of industrial and domestic wastes, agricultural chemicals, and other less obvious contaminants. These impure water returns to the atmosphere as relatively pure molecules through evaporation. ✓ The impurities accumulated by water throughout the hydrologic cycle and as a result of human activities may be both suspended (larger particles) and in dissolved form (molecules, ions). ✓ Colloids are also very small particles that are suspended but often exhibit many characteristics of dissolved substances. WATER QUALITY PARAMETERS 1. PHYSICAL a. SUSPENDED SOLIDS – are the fine particles of sediment in the water. (e.g. soil, biological solids, decaying organic matter, and particles discharged in wastewater) b. TURBIDITY – A measure of the extent to which light is either absorbed or scattered by suspended material in water. c. COLOR – Pure water is colorless ( as perceived by the naked eye) but water in nature is often colored by foreign substances. Apparent Color – color partly due to suspended solids True Color – color contributed by dissolved solids that remain after the removal of suspended solids d. TASTE AND ODOR – Substances that produce an odor in water will almost invariably impart a taste as well however, there are many mineral substances that produce taste but no odor. e. TEMPERATURE – One of the most important parameter. Temperature of surface waters governs the biological species present and their rates of activity. Temperature has an effect on most chemical reactions that occur in natural water. Temperature has an effect on the solubility of gases in water. 2. CHEMICAL a. TOTAL DISSOLVED SOLIDS – The material remaining in the water after filtration. This material is left as a solid residue upon evaporation of the water and constitutes a part of total solids. Dissolved solids may be organic or inorganic. b. ALKALINITY – Quantity of ions in water that will react to neutralize hydrogen ions. It is a measure of the ability of water to neutralize acids. c. HARDNESS – Concentration of all multivalent cations in solution. Sum of calcium and magnesium ions. d. FLOURIDES – Seldom found in appreciable quantities in surface waters. Appear in ground water in a few geographical regions. Toxic to humans and animals in large quantities, small concentrations are beneficial. ENGR. JONAYKA T. AZARIAS Page 3  CHEMISTRY OF THE WATER e. METALS – Metals are opaque, lustrous elements that are good conductors of heat and electricity. Metals are usually malleable and shiny, that is they reflect most of incident light. Basically, all metals are soluble to some extent in water. Excessive amounts may present health hazards. Toxic Heavy Metals – those metals that are harmful in relatively small amounts. Kidney – complex filters whose primary purpose is to eliminate toxic substances. The kidneys contain millions of excretory units called nephrons. Nephrotoxins – chemicals that are toxic to the kidneys. Cd, Pb, and Hg are nephrotoxic metals. f. NUTRIENTS – Elements essential to the growth and reproduction of plants and animals and aquatic species depend on the surrounding water to provide the nutrients. Over – enrichment problems may also lead to Eutrophication (natural aging process in which the water is organically enriched leading to increasing aquatic weeds – algal bloom). g. ORGANICS Natural organics – decay products of organic solids. Synthetic organics – result of wastewater discharges or agricultural practices. 3. BIOLOGICAL Pathogens – biological organisms in water capable of infecting or of transmitting diseases to humans. They are not native to aquatic systems and usually require a HOST for growth and reproduction. Species of pathogens can survive in water and maintain infectious capabilities for significant periods of time. CLASSIFICATION OF PATHOGENS a. BACTERIA – Over – enrichment problems may also lead to Eutrophication (natural aging process in which the water is organically enriched, leading to increasing aquatic weeds – algal bloom) b. VIRUS – smallest biological structures which are known to contain all the genetic information necessary for their reproduction. They can't multiply on their own, so they have to invade a 'host' cell and take over its machinery to be able to make more virus particles. c. PROTOZOA – the lowest form of animal life, they are complete and self-contained organisms that can be free–living or parasitic, pathogenic or non – pathogenic. Most protozoa are microscopic in size and can only be seen under a microscope. However, they do breathe, move and reproduce like multicelled animals. d. HELMINTHS – parasitic worms. The life cycles of helminths often involve 2 or more animal hosts, one of which can be human and contamination may result from human or animal waste that contain helminths. Contaminations could also be via other species such as snails or insects. 4. RADIOLOGICAL ✓ Excessive exposure to radioactive materials is harmful. ✓ Unnecessary exposure should be avoided (including drinking water). ✓ Naturally occurring RA compounds include Radon & Radium 226 found in GW. ✓ Strontium – 90 and Tritium are also found in surface water resulting from atmospheric nuclear weapon testing fallout. ✓ The most significant radionuclides associated with drinking water is dissolved radon gas. ✓ Radon is colorless, odorless & tasteless gas occurring naturally in ground water. ENGR. JONAYKA T. AZARIAS Page 4