Effect of Particle Size on Difference between TSS and SSC Measurements

Three different laboratory methods have been used to quantify the amount of solids contained in the storm water samples. The three methods differ in the sub-sample preparation. In this study, the water samples of nine different particle concentrations over a range from 0 to 1000 mg/L and of seven different particle size distributions over a range from 0 to 1000 microns were prepared and analyzed for the solids concentrations using the three different analytical methods. It was found that the total suspended solids (TSS) concentration measured using EPA Method’s sub-sample pouring procedure was well correlated with the suspended sediment concentration (SSC) measured using the ASTM Method’s whole sample procedure. It was also found that the difference between the measured SSC and the measured TSS-EPA was well correlated with the particle size. The difference was larger as the particle size increased. A regression relationship between the TSS-SSC difference and the particle size was established. This regression relationship could be used to predict TSS-EPA from the reliably measured SSC if the particle size (or the equivalent particle size) is known.