File Name: Turbidity.pptFeb 2001

Turbidity & Suspended Solids

Overview

File Name: Turbidity.pptFeb 2001

Turbidity

Definition Turbidity in liquid is caused by the

presence of suspended solids.

Measurement A Nephelometric process is used which

measures the quantity of light scattered by the particles at right angles

File Name: Turbidity.pptFeb 2001

Units of Measurement

FTU = Formazine Turbidity Units NTU = Nephelometric Turbidity Units TUF - Turbidity Units Formazine

1 FTU = 1 NTU = 1 TUF = 2.5 ppm SiO2 / liter

File Name: Turbidity.pptFeb 2001

Light Scatter

Small particles which are smaller than the light wavelength (approx.. 1/10) scatter light in all directions

Particles which are the same size as the light wavelength scatter light with a distinct distribution in the forward direction

Large particles (approx.. 5 x larger than the wavelength used) scatter light with a more distinct distribution in a forward direction

File Name: Turbidity.pptFeb 2001

Turbidity Sensor

ISO Standard 7027 Measurement wavelength of

up to 860 nm (+/- 30 nm) Measurement angle of 90o

between the light source and receiver

File Name: Turbidity.pptFeb 2001

Comparison of Standards for Potable Water

ASTM D1889 & EPA 180.1 Defines visible light source

• Tungsten lamp operated at color temperature between 2200 and 3000oK

Pro• Current Standard

Con• Expected lamp life 1 year• Affected by stray light• Affected by Color• Affected by air bubbles

International Standard, ISO 7027 Defines wavelength

• The wavelength of the incident radiation shall be 860 nm

Pro• Method accepted on initial

review by ASTM• LED life 10 years• Not affected by stray light• Not affected by color• Only two sensors to measure

from Drinking Water to Sludge Con

• Affected by air bubbles in low Turbidity range

File Name: Turbidity.pptFeb 2001

Installation Options

File Name: Turbidity.pptFeb 2001

De-bubble Flow Chamber

File Name: Turbidity.pptFeb 2001

Typical Wastewater Treatment Plant