01-27 - 02-03 - CEE 351 - ENVIRONMENTAL QUALITY ENGINEERING...

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Every field has its jargon and acronyms; Environmental Engineering is no exception. CEE 351 - ENVIRONMENTAL QUALITY ENGINEERING Water Quality Parameters I. Categories of Water Quality Parameters A . Physical B . Chemical C . Biological II. Units of Expression A. Mass relationships 1. mass/volume: mg/L (milligram/liter) 1 mg/L = 8.34 lbs/10 6 gallon 2. mass/mass = parts per million (ppm) and parts per billion (ppb) [ppm mg/L, for dilute solution] [See note section on General Chemistry ] Volume = volume of solution ; i.e., water with dissolved substances in it. mass material/mass water; Ex. 1 mg/1000 g = 10 - 3 g/10 3 g = ppm
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II. Units of Expression (cont.) B. Chemical expressions 1. Molecular weights, atomic weights, valence, chemical symbols 2. Law of mass action and combining weights 3. Equivalent weights - expression of materials as chemically equivalent quantity of a second chemical substance Ex., for precipitation of minerals: Eq. wt. = molecular weight valence Proportions in reactions are moles , not mass. 1 HCl 1 H + + 1 Cl - 36.5 g 1 g 35.5g For Acid-Base reactions : Eq. Wt. = mol. Wt. / (number of H + or OH - available for reaction) For Oxidation-Reduction reactions: Eq. Wt. = mol. Wt. / (number of electrons lost or gained in a reaction) Example. Fe +3 can form Fe(OH) 3 (s) +3 mol wt. Eq wt. Fe = 3
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Physical Parameters of Water Quality I. Temperature - measured in-situ A. Important in use of water for cooling purposes (thermal pollution) B . Alters solubility of dissolved oxygen and other gases and accelerates biological action hence is important in biological aspects of natural waters. C . Changes chemical equilibrium and kinetics . II. Turbidity - measurement of interference to passage of light through a liquid caused by the suspended material present in that liquid. A. Concern with: 1. Aesthetics 2. Clogging filters 3. Interference with disinfection As a “rule of thumb”, an increase in temperature of 10 o C will double the rate of a reaction. 4. Harmful particles? - pathogenic microorganisms - asbestos particles contaminants adsorbed on particle surfaces
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Physical Parameters of Water Quality II. Turbidity (continued) B . Measured against arbitrary scale of turbidity units arrived at by measuring interference to light passage by solutions containing known amounts of formazin polymer suspension [one turbidity unit corresponds to approximately 1 mg/L SiO 2 (of a specified particle size)]. III. Color A. Caused by dissolved material or colloidal organic matter B . Measured by comparison with arbitrary scale developed from set of solutions containing different amounts of potassium chloroplatinate. [One color unit = 1 mg/L Pt in the form PtCl 6 -2 ]. or colloidal minerals
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Measurement of c o l o r According to Standard Methods for the Analysis of Water and Wastewater: “The visual comparison method is applicable to nearly all samples of potable water.” In the visual method tubes are used containing 50 mL volumes of solutions of a solution containing PtCl 6 -2 . 50 color units = 50 mg Pt/L.
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01-27 - 02-03 - CEE 351 - ENVIRONMENTAL QUALITY ENGINEERING...

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