Turbidty and Color in Water Treatment

TURBIDITYEnvironmental Wastewater Management

Ilyana A. Causing ENFT-4A

TurbidityTotal

Suspended Solids

Turbidity

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Turbidity

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Turbidity

oTURBIDITY can also include:• CDOM (colored dissolved organic matter) – humic stain Tea color produced from decaying plants and leaves – release of tannins Cause water to appear RED or BROWN• FDOM (fluorescent dissolved organic matter)

Water Clarity

oThis is a physical characteristic by how clear or transparent water isoCLARITY – depth that sunlight penetrates in wateroThe further the sunlight can reach the higher the water clarityoDepth of sunlight reached – photic zone

Salinity

oSalt ions can cause suspended particle to aggregate and settle at the bottomoSalinity affects water clarityoSalt affects aggregation and settling velocity of suspended solids

Turbidity Meters and Measurements

oNote:Turbidimeter's Optical Design will affect turbidity readingsReadings can vary based on wavelengths emitted, light source instability, high particle

density or presence of dissolved or colored materials

Typical levels

Clear Cloudy Opaque

Turbidity 5 NTU 55 NTU 515 NTU

Total Suspended Solids 20 mg/L >40 mg/L

How to measure TURBIDITY

Turbidity is measure in NTU (Nephelometric Turbidity Units) Instrument: Nephelometer or TurbidimeterThe unit used in the ancient times was JTU (Jackson Turbidity Units)Instrument: Jackson candle turbidimeter

How to measure TURBIDITY

Turbidity is measure in NTU (Nephelometric Turbidity Units) Instrument: Nephelometer or TurbidimeterThe unit used in the ancient times was JTU (Jackson Turbidity Units)Instrument: Jackson candle turbidimeter

COLOREnvironmental Wastewater Management

Ilyana A. Causing ENFT-4A

What Causes Color in Water?

• Color in water is the result of dissolved extracts from metals in rocks and soil, from organic matter in soil and plants

• When color is caused by metals, it is usually due to iron, copper, or manganese ions

There is a distinction between true color and apparent color

TRUE COLORSAPPARENT

COLORS

Color

• True color is the result of dissolved organics, minerals, or chemicals in water• However, suspended materials in the water (turbidity) can change the apparent color of the

water As a result, the first step of measuring true color is to remove the water's turbidity by

filtration or centrifugation• You should also be aware that changes in pH can change the true color of waterAs a result, pH is always measured along with color during color testing

Measuring Color

Two types of procedures can be used to measure the color in water

visual method

instrumental method

Measuring Color

• The visual method is the simplest since it consists of a water sample being compared to a series of colored slides or tubes

• This method can be used in most cases, but it is not appropriate for use on water which has been contaminated by industrial wastes

• When using the visual method, color is usually measured in color units

• Water with color as high as 20 units will not ordinarily be noticed by the consumer, but the water plant should be operated so that the color will be less than 20 units.

• The EPA Drinking Water Standards limit for color is 15 units

Removing Color

• Color in water is nearly always harmless

• However, for aesthetic reasons, color in water should be maintained at an unnoticeable level

• A plant will have little difficulty in producing an effluent with color of 10 units or less since

coagulation followed by chlorination or ozonation tends to remove the majority of the color

from water