Turbidity measurements and modified imhoff cone method for estimation of suspended sediment concentration

Abstract

The requirement for monitoring of suspended sediment concentrations (SSCs) with good temporal and spatial resolution has led to the development of methods for sediment measurements. In this study, two practical and relatively cheap alternative methods (namely turbidity sensor and Imhoff cone method) were used to estimate SSC. Imhoff cone is a practical and indirect free settleable solid analysis method. Although this method is easy to use and cheap, moving the water samples to the laboratory and allowing them to settle can be time consuming. Therefore Polyacrylamide (PAM), which is a soil conditioner and a flocculant, was tested as an accelerant of sediment settling in Imhoff cone method. PAM concentrations of 0.05 and 0.1 ppm were used in water samples. The results showed that it causes turbidity sensor measurement method had high reliability and advantage including continuous monitoring and ability to read and store more data at high expected sediment concentrations (<10.0 g/L). Finalizing the flocculation and settling material stabilization processes in a short time, like 10 min, increased the use of Imhoff cone method in the field conditions without having to move samples to the laboratory. However, this method had disadvantages of causing errors at low sediment concentrations and requiring sensitive measurements due to the graduation of the cone. These problems can be solved by using better graduated cones or digital sensors in the cones. Finally, this study showed that these methods have potential with high reliability and are good alternatives for practical and economical sediment measurements. © by PSP.