Overview
FrançaisABSTRACT
Turbidity is one of the main parameters allowing for the characterization of water quality at input and output after internal treatment in factories. For most consumers, the clarity and transparency of drinking water remain the proof that it is of high quality. The matters contained in water are either dissolved or under the shape of suspended particles; these particles are involved in the measurement of the turbidity of the water to be treated. After having introduced the theoretical notions of turbidity, this article goes on to present the measurement and calibration principles associated to this parameter. The various measurement techniques and their fields of application are then detailed.
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Read the articleAUTHOR
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Claude PELLETIER: Engineer from the École supérieure d'ingénieurs en génie électrique (ESIGELEC-Charliat) - Technical Director EXERA (Association des exploitants d'équipements de mesure, de régulation et d'automatismes)
INTRODUCTION
Turbidimetry is part of industrial photometry, and represents one of the main parameters for determining drinking water quality. Indeed, the clarity and transparency of water are the image of high water quality for most people.
Turbidimeters are used in a wide variety of applications, including :
Drinking water treatment to check that sedimentation, flocculation, decantation and filtration equipment is working properly;
wastewater treatment ;
microbiological research ;
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the food industry:
drinks, soups,
dairy,
cheese dairy, etc. ;
sulfate analysis ;
surface treatments ;
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thermal systems for water quality control:
control of colloidal silica for boiler and turbine protection,
iron particles entrained in steam production from geothermal sites;
the pulp and paper industry ;
the semiconductor industry;
textile industry;
the chemical and petrochemical industries ;
various other industries.
Fluid turbidity can be modified by changes in its physical, microbiological, chemical and radiological properties. These changes can have significant effects on the microbiological quality of drinking water, due to the presence of bacteria and viruses. Microbial growth in water is particularly marked on the surface of particles and within low-coherence flocs. There is a coincidence between the existence of pathogenic germs and suspended solids.
Excessive turbidity alters the appearance of treated water and can interfere with the disinfection process and the maintenance of a sufficient chlorine residual in the distribution network.
Turbidity measurement can be used as a substitute for other parameters, for example:
detection of bacteria and viruses;
arsenic in natural water, the turbidity of which gives an indication of its content;
surface treatment water, whose pH measurement (neutralization) is followed by turbidity measurement.
These analyzers are designed for installation at operating sites for continuous water monitoring:
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Turbidity measurement
Bibliography
References
Glossary
Turbidity: the reduction in transparency of a liquid due to the presence of undissolved matter (NF EN ISO 7027 standard).
The definitions below are taken from FD ISO GUIDE 30.
Reference material (RM): material or substance for which one or more property values are sufficiently homogeneous and well defined to enable it to...
Regulations
Ministerial Order of February 2, 1998, published in the Journal Officiel of March 3, 1998
* Section III – Surface water pollution
Article 31
For receiving waters to which the provisions of Decree no. 91-1283 of December 19, 1991 apply, the effects of discharge must comply with the following provisions: no increase of more than 30% in suspended solids.
...
Standardization
- Water quality – Turbidity determination. - NF EN ISO 7027 - (mars 2000)
- Qualité de l'eau. Échantillonnage. Partie 1 : lignes directrices pour la conception des programmes et des techniques d'échantillonnage. - NF EN ISO 5667-1 - 2007
- Qualité de l'eau. Échantillonnage. Partie 3 : lignes directrices pour la conservation et la manipulation des échantillons d'eau. - NF EN ISO 5667-3 - 2004
- Qualité de l'eau....
Manufacturers and distributors
Table 1 lists the main equipment manufacturers and their distributors.
Organizations
Association of Measurement, Control and Automation Equipment Operators (Exera) http://www.exera.com/
ISA Instrumentation, Systems and Automation Society http://www.isa.org
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