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
• Humic Acid
• Humates
If iron is also present  Ferric humates
• 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)
Types of Color
• Apparent Color: Color caused by
suspended matter
• True color: Color due to vegetable or
organic extracts that are colloidal.
• Color intensity ↗ with pH ↗
It is important to record pH and report the color
value with the pH.
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.
Sources of Color
• Natural coloring material
Generally not harmful and toxic
Yellowish brown color
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
Color Standard in Drinking
Water
• Primary ? Secondary?
Aesthetic reasons
USEPA drinking water std. Color < 15 units
recommended
Secondary Maximum Contaminant Level
SMCL
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
Standard Color Solutions
• Potassium chloro platinate K2PtCl6 tinted with
cobalt chloride
Yellow – brownish color
1 mg/L platinum K2PtCl6  Standard unit of
color
Color Measurement
• Color comparison tubes (Nessler tubes)
0 – 70 color units
If color > 70  Dilution is necessary
• Colored glass disks
• Spectrophotometric determination
• Color data  Determination of chemicals to
be used in treatment
Dose optimization
• Color parameter is used as a THM precursor