Total suspended solids measures the actual mass of particles held in the water column — silt, clay, organic debris, and algae. The sample is filtered, the filter is dried, and the residue is weighed. It is a direct, quantitative answer to the question of how much material is in your water, and it is the standard measurement for sediment and erosion problems. Method SM 2540 D; MDL 0.2 ppm, RL 0.2 ppm.