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Physical Methods
Published in Jerome Greyson, Carbon, Nitrogen, and Sulfur Pollutants and Their Determination in Air and Water, 2020
Turbidimetry and nephelometry are analytical techniques that are based on the light scattering properties of suspended solids. The two techniques differ only in the manner in which the scattered light is observed. In turbidimetry, measurement is made of light that is scattered in a forward direction by the suspended matter. In nephelometry, light that is scattered at a 90° angle from the direction of the source radiation is measured. In both cases, the intensity of the signal reaching the detector may be related to the concentration of the suspension.
Biodesulfurization of high sulfur coal from Shanxi: Optimization of the desulfurization parameters of three kinds of bacteria
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Jie Xu, Xiangrong Liu, Changlei Song, Zhipeng Du, Fangxin Wang, Jingwen Luo, Xinjuan Chen, Anning Zhou
Colorimetry (turbidimetry) is a rapid method for determining the number of cells in a suspension. The growth curves of three bacteria were determined by measuring the optical density at 600 nm (OD 600 nm). The effects of four surfactants (concentration of 0.1%) on the growth curves of three microorganisms in culture were shown in Figures 4a–6a. It was found that the bacterial lag phase would be prolonged if surfactant was directly mixed with culture medium before inoculation. Compared with the biomass of different microorganisms without surfactants, the decrease in biomass of bacteria with surfactants is almost 17% at the stationary phase. The results indicated that surfactants could inhibit bacterial growth up to some extent.
Functionality of turbidity measurement under changing water quality and environmental conditions
Published in Environmental Technology, 2022
Jani Tomperi, Ari Isokangas, Tero Tuuttila, Marko Paavola
Turbidity is, however, a difficult parameter to measure absolutely because many factors affect the turbidity reading. The most common method for measuring turbidity nowadays is an optical sensor. Optical sensor works by emitting a beam of light and detecting the amount of light that reaches the detector. The more particles present in the liquid, the more the light will be scattered, absorbed and diminished. Scattered light can be measured by nephelometry or turbidimetry methods. The angle between light source and detector is 90° for nephelometry or 180° for turbidimetry, i.e. in turbidimetry the intensity of light transmitted through the medium is measured and in nephelometry the light scattered 90° is measured. However, the optical design (the placement and design of the detector) of the turbidimeter will affect the turbidity reading. Turbidity instruments of different design commonly do not yield identical or equivalent results and therefore turbidity values measured with different turbidity meters, for example based on nephelometry or turbidimetry, are not directly comparable. In addition, bubbles, gases, sensor fouling such as biological growth, or scratches on the optical surface of the instrument produce a bias when light beams are blocked. The degree of scattered light is dependent on the amount and the properties of (i.e. size, shape, density and colour) the suspended particles (e.g. algae, clay or sand). When there are wide variations in the composition of particle properties, precise turbidity measurements are likely impossible. Organic material has different optical properties compared with inorganic material and therefore optical measures as turbidity scatter light differently for organic particles which cause substantial uncertainties. Waters are coloured mostly due to the suspended particles or dissolved compounds, for example, the decomposition of organics, metallic salts or coloured clays. Water colour value is found to be pH dependent and can affect a turbidity measurement. Also, measuring turbidity under static (sampling and laboratory measurement) or dynamic (in situ continuous measuring) conditions will affect the turbidity readings. Dynamic measurement techniques more accurately reflect the dynamic nature of the particle movement within the water body, but static measurements do not account for particle settling. Measuring turbidity directly within the water source is preferable because of problems with representative sampling, the settling of solids, temperature and pH changes, and interferences such as condensation or scratches on sample cuvettes. The temperature of the sample changes during the transport to a laboratory and causes differences between the laboratory and in situ measurements. [1,10–12]