Environmental Engineering Lecture 3

1. Environmental Engineering Lecture 3

2. Review • Questions 2-1, 2-8, 2-9

3. Alkalinity • Alkalinity of a water is a measure of its capacity to neutralize acids – to absorb H ions • Alkalinity is measured by titrating with a strong acid (H2SO4) • Acidity is measured by titrating with a strong basic solution (NaOH)

4. Pure Water Titration

5. Carbonate Water Titration Phenolphthalein indicator Pink to colorless Methyl Orange indicator Orange to Pink

6. Alkalinity Measurements • Alkalinity is measured by titrating a given sample with 0.02 N sulfuric acid • Normality = equivalent of solute/1 L of solution • 0.02 N H2SO4 contains 0.98 g of pure sulfuric acid

7. Alkalinity Measurements Alkalinity expressed in terms of mg of CaCO3 per liter If the water sample is 100 ml and normality of acid is 0.02 N, 1 ml of titrant gives: 10 mg/l Alkalinity

8. If P the amount of titrant to reach Phenolphthalein end point

9. Example 100 ml water sample is titrated for alkalinity by using 0.02 N sulfuric acid. To reach pH 8.3 requires 3 ml. and an additional 12 ml is added to reach 4.5 pH Calculate the phenolphthalein and total alkalinities?

10. Hardness Hardness is caused by multivalent metallic cations, those most abundant in natural waters are Calcium and Magnesium

11. Hardness EDTA = ethylene-diamine-tetra-acetate

12. Hardness • Hardness in mg/L as CaCO3: = Ca+2 [mg/l] x 50 / eq wt of Ca+2 = Mg+2 [mg/l] x 50 / eq wt of Mg+2 = HCO3- [mg/l] x 50 / eq wt of HCO3- • Total Hardness = Ca+2 +Mg+2 • Determine the various hardnesses of the following sample: • Ca+2 = 60 mg/l • Mg+2 = 29.3 mg/l • HCO3- = 366 mg/l • Questions 2-4 and 2-5

13. Color • Pure water is colorless, but water in nature is often colored by foreign substances • Natural minerals (iron, manganese) • Vegetables origins • Colored industrial waste • 1 standard color unit =1mg/l platinum + ½ mg/l metallic cobalt

14. Turbidity Insoluble particles of soil, organics, microorganisms, and other materials impede the passage of light through water by scattering and absorbing the rays. This interference of light passage through water is referred to as turbidity. Measurement of turbidity in treated drinking water, commonly less than one unit, is measured using (nephelometer). Units of turbidity using a nephelometer are expressed as Nephelometric Turbidity Units (NTU).40 NTU up to 10,000 NTU

15. Colloid & Coagulation • A large variety of turbidity-producing substances found in polluted waters do not settle out of solution, • for example, color compounds, clay particles, microscopic organisms, and organic matter from decaying vegetation or municipal wastes. These particles, referred to as colloids, • range in size from 1 to 500 millimeters and are not visible when using an ordinary microscope.

16. Coagulation • The purpose of chemical coagulation in water treatment is todestabilizesuspended contaminants such that the particles contracts and agglomerate forming flocs • Colloids • Hydrophobic (clay, inorganic matters…) • Hydrophilic (soap, blood, detergents…) • Destabilization of hydrophobic colloids is accomplished by addition of chemical coagulants, such as salts of aluminum and iron. They reduce the repulsive forces between colloids

18. Organic Chemistry Of the organic matter in wastewater 60 - 80% is readily available for biodegradation

19. Organic Chemistry • Biodegradable Organic Matter: • Carbohydrates (Sugar + Carbon + Hydrogen+ Oxygen) • Protein (Amino acids + Carbon + Hydrogen+ Oxygen) • Fat(Glycerol Units)

20. Groups of Organic Compounds

21. Nitrogen • Common Forms • Organic matters (nutrients) • Ammonia (toxic for fishes) • Nitrite • Nitrate • Gas Nitrogen