1. ENVE 201 Environmental Engineering Chemistry 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 + Cl 2  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 K 2 PtCl 6 tinted with cobalt chloride Yellow – brownish color 1 mg/L platinum K 2 PtCl 6  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

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