Influência da concentração e da granulometria de sedimentos na medida da turbidez com uso de sensor óptico

Abstract

The transport of suspended sediment in water bodies is responsible for the reduction of water quality, the transport of pollutants, the silting of reservoirs, among other problems. That is why it is important to monitor the management of water resources. The turbidity sensor has been used as an indirect measure for the monitoring of suspended sediment concentration (SSC). However for the proper calibration of the turbidity sensor, the factors that influence its measurement must be considered. Among these factors are the sediment, equipment and flow characteristics. The characteristics of the sediment of greatest influence on the measurement of the sensor are the concentration and the size of the sediment. In this way, we aim to verify the influence of the sediment concentration and grain size on the CSS estimation with the use of the turbidity sensor. For this, three experiments were carried out to evaluate the turbidity measurement in different concentrations and granulometry using an artificial channel fed by water and sediment. In the first experiment, the concentration and turbidity were measured in 60 experimental points with different CSS. In the second, these same parameters were measured in 12 experimental points, but with sediment in 4 different granulometries. In the third experiment besides the granulometry variation, the solid discharge of sediment in suspension was also varied with the control of the inflow of sediment. A linear relationship between the turbidity and CSS results was established for all experiments, which provided the line equation and the R². In experiment 3 the relationship between turbidity and CSS was established for each experimental point. With the results obtained, it was concluded that the relationship between turbidity and SSC is influenced by concentration and grain size, and with increasing concentration there is a decrease in the effect of particle size on turbidity sensor sensitivity. Finally, it is concluded that in low solid discharge condition, the turbidity measurement decreases with increasing particle size.