Light scattering by small particles

Abstract

On‐line turbidimeters are currently used for monitoring particle concentration in water and gas treatment processes. For small particle concentration, the intensity of scattered light is a linear function of the particle concentration, as long as a number of other parameters are kept constant: the refractive indexes of the particles and the surrounding medium, size, measuring angle and wavelength of the light. An international standard has been created in order to define the characteristics of the turbidimeters and the calibration suspension. The effects of the parameters are described and quantified. The special aspects of the measurement of very low turbidity values in water are treated: the zero value of water and the definition of the calibration conditions. A measuring method is presented which grants long‐term stability without recalibration. The first industrial application for on‐line turbidimeters was the monitoring of beer filtration in breweries, which started about 50 years ago. In the meantime, turbidimeters have been used in very diversified fields such as dust measurements in stacks, visibility in road tunnels and filtration control in the chemical industry. However, their main application today is the monitoring of drinking water treatment plants: control of the flocculation process by measuring the variations in the raw water (rivers, lakes, ground‐water, sources) and the resulting properties, sand filtration survey and final quality control.

Turbidity and RI Dependency of a Polymer Optical Fiber-Based Chromatic Sensor

“…For increased turbidity, corn starch was added to all the solutions to promote scattering centers. The size of these particles is on average 20 μm [17] where forward scattering is dominant [18]. Both chemical species were homogenous distributed in the solution.…”

Effects of particles and bioflocculation on ultraviolet disinfection

“…Research by Huber and Frost (1998) pointed out that in a medium with obstacles light will be deflected from its original path. This deflection is referred to as scattering and the degree of it depends on the nature of the particles.…”

“…The refractive index of a particle depends on its composition and as a natural consequence the difference between the indices of water and a particle is less when the particles are watery materials (such as biological cells), and more for inorganic particles (such as metal oxides). The larger this difference is the more scattering occurs (Huber and Frost, 1998).…”

“…When UV light is scattered by particles, although its energy is reduced, it is still capable of inactivating microbes. UV light that is absorbed by particles on the other hand, is no longer available for inactivation (Huber and Frost, 1998;Mamane and Linden, 2006b). However, the effect of absorbance can be properly factored into the delivered UV dose calculations such that no significant reduction in disinfection efficiency takes place for a specific UV dose (Christensen and Linden, 2003).…”

“…The reasons for this choice are the widespread use of turbidity in regulations as a water quality parameter and because turbidity is a simple way of measuring particles content of a sample by detecting the intensity of light scattered (AWWA, 1999). However, although turbidity measurements are usually directly proportional to mass concentration of particles, they are poor indicators of number concentration [i.e., equal numbers of different sized particles do not result in equal turbidities as light scattering depends on the particle size (Huber and Frost, 1998)]. Passantino et al (2004) investigated the effects of turbidity and algae on UV inactivation of MS2 bacteriophage with medium-pressure UV lamps.…”