This month we’ve been focusing on this critical water quality parameter - why and how it’s used as a measure of quality, and the practical options available for monitoring it in a variety of applications.

Turbidity is one of the most common measurements used in qualitative assessment of water suitability. Turbidity data is useful in drinking water treatment and production, wastewater and environmental monitoring, various process applications (e.g. aquaculture) and some pool markets.

“the optical property that causes light to be scattered and absorbed rather than transmitted in straight lines through the sample”

“Standard Methods for Examination of Water and Wastewater"

The concept of turbidity is the ‘cloudiness’ of water due to light being scattered by small particles suspended within the sample. The particles that create turbidity can be suspended inorganic material (silt, sand), organic material and micro-organisms (phytoplankton, cryptosporidium)

caption: Factors affecting the turbidity of water

The development of turbidity as a qualitative measure has been promoted both by developments in instrumentation and the production of reference materials that can be used for comparison and calibration.

The speed of turbidity measurement makes it an excellent tool for general water quality monitoring, requiring no reagents and capable of being determined visually. The human eye is an excellent turbidity meter, capable of determining to approximately 4 NTU.

Turbidity is measured in a number of applications:

  • Drinking water - The development of turbidity as a qualitative measure has been promoted both by developments in instrumentation and the production of reference materials that can be used for comparison and calibration. The speed of turbidity measurement makes it an excellent tool for general water quality monitoring, requiring no reagents and capable of being determined visually. The human eye is an excellent turbidity meter, capable of determining to approximately 4 NTU.
  • Wastewater - Measurement at all stages of treatment processes but the use of Total Suspended Solids is of more importance here. Surface water monitoring (streams, rivers, lakes, oceans) is also of importance due to the effects of turbidity on aquatic ecosystems. Levels of turbidity are very difficult to quantify due to the extremely variable nature of samples and processes e.g. the Blue Nile annually varies from several thousand NTU down to 6 NTU.
  • Process Industries - Filtration equipment monitoring, sedimentation studies and aquaculture environment control utilize turbidity measurement for process control.

We've put several articles together this month, taking a look at turbidity in two very different applications:

  • Network Turbidity Testing - a case study looking at how important turbidity is for a drinking water supplier in maintaining the quality of their networks. Read the full article online here.
  • Measuring Turbidity in Swimming Pools - a techincal article looking at why turbidity is important for pool water quality, and what options exist for regular and accurate monitoring. Read the article online here.

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