Civil4136: Environmental Engineering I Lecture Notes PDF

CIVIL4136: Environmental Engineering I Lecture 3a: Water Quality- Physical Quality Dr. Md. Abdullah-Al-Mamun Dept of Civil and Architectural Engineering Sultan Qaboos University Muscat, Oman  Lecture outlines - Global water distribu...

CIVIL4136: Environmental Engineering I Lecture 3a: Water Quality- Physical Quality Dr. Md. Abdullah-Al-Mamun Dept of Civil and Architectural Engineering Sultan Qaboos University Muscat, Oman  Lecture outlines - Global water distributions - Water is a strange molecule - Water quality issues - Impurities in environmental media - Water quality parameters - Details of Physical Quality  Water cycle Ice and snow melting Huge pumping for irrigation Saline water intrusion to ground water Distribution of Earth’s water [0.03% on global water] Water (H2O) is a strange molecule Water is a polar molecule  Water (H2O) is a strange molecule Why does water bend at its surface? Think about, How an water insect walks on the water surface. It doesn’t sink because of the water’s surface tension. Surface tension was developed due to ability of water molecules to stick to each other. Hydrogen atoms of one water molecule are attracted to oxygen atom of another molecule. Each water molecule Hydrogen can form up to four hydrogen bonds and, bonds in liquid water collectively, they give water a cohesiveness. Water (H2O) is a strange molecule 8.33% Why does ice float? In liquid water, the irregular positions of hydrogen bonding creates denser packing, but in ice, the hydrogen bonds are in regular position 91.67% forming hexagons, which achieves lighter packing. Photograph: Ralph A Clevenger/CORBIS  Water (H2O) is a strange molecule Different snow crystal formation Water Quality Issues  Water Quality Issues (global) Global water quality problems: According to UN (United Nations) Eutrophication: A result of high-nutrient load (mainly P, N), impairs beneficial uses of water. Major nutrient sources include agricultural runoff, domestic sewage (also creates microbial pollution), industrial effluents and atmospheric inputs from fossil fuel burning and bush fires. An emerging water quality concern is the discharge of personal care products and pharmaceuticals, such as birth control pills, painkillers and antibiotics, on aquatic ecosystems. Climate change cause some major alterations to the hydrological cycle (Tsunami, flood, droughts, ….).  Water Quality Issues (Local) Example of Water quality issues in Delhi, India Groundwater is contaminant by chemical pollutants such as fluorides, nitrates and iron due to leachates from industrial effluents, waste dumps and fertilizers. − Fluoride content of Rithala village was recorded as high as 6.4 mg/L, Hanuman mandir as 3.2 mg/L. − Municipal water is often getting F- and NO3- by adding groundwater with it. − Supply water at Asia House, Gandi Marge and Moti Bagh have shown nitrate content above 100 mg/L. − Almost 90% groundwater supply showed bacterial content in central Delhi. High Arsenic content of 50-3200 µg/L found in groundwater (West Bengle, India and Bangladesh) Almost all the smaller rivers in Indian have turned into toxic streams. The effects on rivers form population growth, agriculture modernization, urbanization and industrialization – is enormous and growing day by day….Most Indian cities get a large portion of drinking water from rivers. This entire life stands threatened (Source: Centre for science and environment, 1999, p. 58) Water Quality Issues (Local) Groundwater salinity problem in Oman due to seawater (Cl-, F-) intrusion.  Health effects of fluoride in Oman: Tooth fluorosis will be Bone fracture or caused by F ˃ 2 mg/L bending of bones will be cause by F ˃ 4 mg/L. No F content in water will create cavities in tooth 14  Water Quality Issues Distribution of water on Earth is uneven, sometimes it is too much. Water Quality Issues Water Quality Issues Water Quality Issues Water Quality Issues Water Quality Issues Water Quality Issues Water Quality Issues Water Quality Issues Water Quality Issues Water Quality Issues  Water Quality Issues Oil spillage  Impurities in Environmental Media 1. Inorganic impurities 2. Organic impurities 3. Particulate matter 4. Radionuclides 5. Microorganisms  1. Inorganic Impurities Ions in Water Sodium (Na+), Potassium (K+), Magnesium (Mg2+), Calcium (Ca2+), Aluminum (AL3+), Chloride (Cl-), Fluoride (F-), Bicarbonate (HCO3-), Sulfate (SO42-), Nitrate (NO3-) Inorganic Gaseous Pollutants Carbon monoxide (CO), Nitrogen dioxide (NO2), Sulfur dioxide (SO2), Ozone (O3) Toxic Metals Arsenic (As), Barium (Ba), Cadmium (Cd), Chromium (Cr), Cobalt (Co), Copper (Cu), Lead (Pb), Mercury (Hg), Nickel (Ni), Selenium (Se)  2. Organic Impurities Organic chemicals are built on a structure of carbon, hydrogen, and oxygen as common constituents. Alkanes: In addition to containing only hydrogen and carbon atoms, alkanes (also known as paraffins), are characterized by having open chains of carbon atoms (either branched or straight) in which pairs of carbon atoms share only single bonds. Alkenes: Alkenes differ from alkanes in that at least one pair of carbon atoms shares a double bond.  2. Organic Impurities Aromatics: The primary building block of an aromatic compound is the benzene ring. Benzene consists of six carbon atoms in a stable ring configuration with alternating single and double bonds. Polycyclic Aromatic Hydrocarbons (PAH): When several of the benzene rings are joined together, polycyclic aromatic hydrocarbons (PAH), such as naphthalene (2 benzene rings), phenanthrene (3 benzene rings), and benzo-a-pyrene (5 benzene rings) are formed.  2. Organic Impurities Oxygenated Organic Compounds: Such class of organic compounds includes oxygen in its structure. Halogenated Organics or Chlorinated Solvents Halogenated hydrocarbons are one of the largest and most important groups of contaminants found in groundwater. This group consists of both aliphatic and aromatic sublasses and is charecterized by the presence of one or more halogen atoms (Cl, Br, F). Examples: methylene chloride, chloroform, tetrachloroethylene (PCE), trichloroethylene (TCE), 1,2 dichloroethylene (1,2 DCE), and vinyl chloride.  2. Organic Impurities Organic Compounds Containing Sulfur or Nitrogen: Organic compounds containing sulfur or nitrogen are often of interest because of their strong odors and environmental health hazards.  3. Particulate Matter Suspended particles are another broad and important class of environmental impurities. We refer to a suspension of particles in air as an aerosol. In water, the particles are typically solid, and their suspension in water is sometimes called a hydrosol.  4. Radionuclides Radionuclides are chemical elements with an unstable atomic nucleus. When Radionuclides undergo radioactive decay, energy is released that can damage exposed tissue. Isotope Half-life Dominant Sources Exposure Pathway Tritium (3H) 12.3 y Weapons testing, fule reprocessing Hydrologic cycle Carbon-14 (14C) 5730 y Natural production, weapons testing Various Potassium-40 (40K) 1.3x109 y Natural Food chain Krypton (85Kr) 10.7 y Nuclear power, fuel processing External gas exposure Strontium (90Sr) 28.8 y Weapons testing Food chain Iodine (131I) 8.04 y Weapons testing, reactor accidents Inhalation, food chain Cesium (137Cs) 30.2 y Weapons testing Food chain Radon (222Rn) 3.85 d Natural, earthen material inhalation Radium (266Ra) 1600 y Natural Water and food chain Uranium (235U) 7x108 y Natural, enriched for reactor and weapons Industrial and military activities Plutonium (239Pu) 24,100 y Weapons, fuels for reactors Industrial and military activities  5. Microorganisms Microorganisms are common impurities in both water and air and are of great interest in environmental engineering. Certain organisms, called pathogens, can cause diseases. Prokaryotic Eukaryotic Viruses Bacteria Archaebacteria Protozoa fungi Algae  Drinking Water Quality parameters Water quality characteristics – Physical: turbidity, color, taste and odor, solid content – Chemical: pH, alkalinity, acidity, hardness, COD – Biological: bacteria, protozoa, viruses, algae, BOD  Wastewater Quality parameters Wastewater quality characteristics − Physical: Turbidity, color, odor, total solids − Chemical:  COD, TOC, Nutrients (N, P)  Heavy metals, trace elements  Organic industrial wastewater (need neutralization) − Biological: BOD All contaminants in water and wastewater are three types: Dissolved i.e. gases (O2, N2, CO2, H2S) cations, anions, organic compounds 1 2 3 Suspended - settle rapidly ( > 10 micron) Sands, silts, clay Microorganisms (bacteria (4.5 μ), protozoa) Colloidal – do not settle rapidly (< 1 micron) Organic matter, example is milk powder Viruses  Water Quality- Physical Solids content Turbidity Colour Taste and odour Temperature  Solids Content Source of solid: – Erosive action of water flow over ground surfaces – Domestic and industrial wastewater mixing – Plant fibers & biological solids (algal cell,..) Na+ K+ Impacts of solid in water: Na+ Ca+2 – Provides adsorption sites (space) for biological & chemical Agents – Organic solids may be degraded biologically and exhaust the DO from water – Organic solids may include disease-causing organisms Measurement (mg/L or ppm): – Total solids (TS) – Total suspended solids (TSS) & dissolved solids (TDS) – Organic & inorganic sediment  Solid content measurement: Gravimetric analysis Organic water solid Water sample TS = 25 mg / 100 mL = 25x10 mg / 100x10 mL = 250 mg / L Suspended ME MF solid Watman filter paper made by air glass fiber. Dissolved solid MH  Solid content measurement: Gravimetric analysis Total Solid 400 gm 150 gm SS Separate them by DS = gm using filter FSS FDS VSS VDS (inorganic, (inorganic, (organic, evaporate (organic, evaporate evaporate above 550 evaporate above below 550 0C) below 550 0C) 0C) 550 0C) = gm 100 gm 120 gm = gm Separate them by Separate them by using heat using heat  Turbidity Measure of clarity of water Due to colloid materials, microorganisms, silt, clay, algae, organic debris Impact – Adsorption sites for chemicals (taste & odor) – Affects flora (plants) & fauna (animals) in water due to light penetration interfering  Turbidity Turbidity is due to suspended particles. Measured using a nephelometer – Scattering of light at 90º – Units are NTU (nephelometric turbidity units) or JCU (Jackson turbidity units) How it works: If the light strikes a colloid, the light is scattered, bouncing off and reflecting upward. If the light does not strike a colloid, it shines through the water sample. The meter measures how much light is reflected off colloids in the water. Clear water will reflect little light while turbid samples, like this one, will reflect large amounts of light.  Color Pure water is colorless – Apparent color due to Suspended solids – True color due to Dissolved solids Source – Leaves, weeds, wood & acid produce yellowish-brown – Manganese oxide produce brown or blackish water – Industrial water (textile, dyeing, pulp, paper, mining & slaughter house produce several colours Impact – Affects the marketability of water for both domestic & industrial use Measured as total color units (TCU): Measure relative color with a standard reference color solutions.  Taste and Odor is coming in - Surface Water  Due to organic compounds (humic acid) produced from algae or microbial growth Ground Water  Due to dissolved gases (H2S, NH3) Measured in threshold odour test Water diluted until odour not longer detected Threshold odour number: TON = diluted vol/sample vol Impact – Not acceptable Original diluted – Some organic substances may be carcinogenic (causing cancer)  Temperature It governs the presence, rates & activities of biological species in water. Also affects chemical reactions and solubility of gases in water. Source – Temperature of atmosphere (Shallow bodies) – Discharge of industrial heated water – Irrigation return flow Impact – Biological activities increase as temperature increases – Accelerates growth of algae (taste & odor) – Accelerates chemical reactions – Physical properties of water are affected