Turbidity Measurement in water treatment

A general definition of Turbidity is the decrease in the transparency of a liquid caused by the presence of un-dissolved substances (ISO/EN7027). The definition of Turbidity Measurement can explained as where Solids are so finely dispersed in the liquid that they do not significantly settle even when allowed to stand for a long period of time.


In Suspended Solids Measurement it is where solids are sufficiently large that they will either drop to the bottom or rise to the top of a sample given sufficient opportunity. There is no defined point where turbidity stops and suspended solids start but for practical purposes we use 1000 NTU/FTU as a crossover point.

The following products listed below can help with Turbidity Measurement in water treatment.

The LTH instrumentation and Quadbeam sensors will treat both types of solids as a disruption of the light signal and infer the appropriate solids content in FTU, g/l , mg/l, NTU, percent, etc. The units of measurement are:

NTU: An instrument that measures turbidity by the 90˚ light scattering method is called a nephelometer. The measuring units are Nephelometric Turbidity Unit or NTU.

FTU: Formazin is the only reliable standard with which we have to measure turbidity and suspended solids. Calibrations made with Formazin are called Formazin Turbidity Units or FTU.

The unique high quality T30 turbidity sensor uses a combination of four beam ratio-metric measurement with both attenuated and 90° scattered Near Infra-Red light and provides a reliable, repeatable and accurate measurement of turbidity. The T30 turbidity sensor has been designed to meet the international standards for turbidity measurement. (ISO/EN 7027)

Applications for Turbidity measurement include:
Monitoring of clarifier overflow weirs
Final outlet of effluent from DAF plants
Raw water inlet measurements in water treatment plants
Surface water monitoring
Solids loading in rivers and streams
Product breakthrough on plate heat exchangers
Percentage solids in fruit and vegetables juices

The key features of the LTH Electronics instrumentation and Quadbeam T30 Turbidity measurement system are:

Ratiometric signal processing compensates for changes in the optical properties of the emitters and detectors due to ageing and surface coating.

Effects of colour, temperature and changes in background ambient light are virtually eliminated.

Call us on +44 (0)1582 593693 or email sales@lth.co.uk to find out how we can help you.