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ENVE 201 Environmental Engineering Chemistry 1

ENVE 201 Environmental Engineering Chemistry 1. COLOR (Chapter 13) Dr. Aslıhan Kerç. Color. Most of the surface water are colored, especially in swampy areas. Coloring material  due to contact of water with organic debris (decomposition of leaves, woods). Principal Color Bodies. Tannins

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ENVE 201 Environmental Engineering Chemistry 1

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  1. ENVE 201EnvironmentalEngineeringChemistry 1 COLOR (Chapter 13) Dr. Aslıhan Kerç

  2. Color • Most of the surface water are colored, especially in swampy areas. Coloring material  due to contact of water with organic debris (decomposition of leaves, woods)

  3. Principal Color Bodies • Tannins • Humic Acid • Humates If iron is also present  Ferric humates

  4. Natural color  Negatively charged colloidal particles. can be removed by coagulation Surface waters may appear highly colored due to colored suspended matter (red clay soil)

  5. Types of Color • Apparent Color: Color caused by suspended matter • True color: Color due to vegetable or organic extracts that are colloidal.

  6. Color intensity ↗ with pH ↗ It is important to record pH and report the color value with the pH.

  7. Sources of Color • Discharge of highly colored wastewater into water sources. Examples ? Dyeing operation in textile industry. Pulping operation in paper industry  lignin. Lignin is highly colored and resistant to biological degredation.

  8. Sources of Color • Natural coloring material Generally not harmful and toxic Yellowish brown color

  9. Formation of Tri Halo Methanes (THMs) Chlorination of waters containing NOM (Natural Organic Matter)  Formation of THMs NOM + Cl2  THM THMs  - Chloroform - 1,2 dichlorobromomethane - 1,2 dibromochloromethane - Bromoform

  10. Color Standard in Drinking Water • Primary ? Secondary? Aesthetic reasons USEPA drinking water std. Color < 15 units recommended Secondary Maximum Contaminant Level SMCL

  11. Methods of Determination • To measure true color  Pretreatment to remove suspended matter  Centrifuging Filtration ? not recommended due to adsorption of color onto the filter Apparent color  Measured as is

  12. Standard Color Solutions • Potassium chloro platinate K2PtCl6 tinted with cobalt chloride Yellow – brownish color 1 mg/L platinum K2PtCl6  Standard unit of color

  13. Color Measurement • Color comparison tubes (Nessler tubes) 0 – 70 color units If color > 70  Dilution is necessary • Colored glass disks • Spectrophotometric determination

  14. Color data  Determination of chemicals to be used in treatment Dose optimization • Color parameter is used as a THM precursor

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