Sludge Dry Solids and Moisture Conversion

What does solids content mean?

Dry solids content is the dry residue mass divided by the total wet mass. A 100 g sample with 20 g of dry residue has 20 percent solids and 80 percent moisture on a wet basis. Enter masses after subtracting container tare. A representative sample is as important as the calculation.

Why moisture percentages differ

Wet basis moisture uses total mass as the denominator. Dry basis moisture uses only dry solids. In the same example, 80/20 = 4, so moisture on a dry basis is 400 percent. This is valid. Treating loss of other volatile material as water changes the physical meaning of the result.

Convert weighing results to a moisture basis

Suppose net wet sample mass is 80 g and the residue after drying is 20 g. Water mass is 80 − 20 = 60 g. Solids content is 20 / 80 = 0.25, or 25 percent. Wet basis moisture is 60 / 80 = 0.75, or 75 percent. Dry basis moisture is 60 / 20 = 3, or 300 percent. All three percentages refer to the same sample but use different definitions.

Solids percentage plus moisture on a wet basis must total 100 percent. Do not include moisture on a dry basis in that sum. When transferring a result to another drying or sludge calculation, check whether the requested input is solids or moisture. Entering 75 percent moisture as 75 percent solids reverses the mass balance.

If residue mass appears greater than wet mass, examine units, container tare and sample matching. Applying a sample result to a whole batch is meaningful only when the sample represents that batch. Do not combine wet and dry weighings from different days as if they were measurements of the same sample. This tool does not assess the suitability of the laboratory method.

Frequently asked questions

How do you calculate dry solids in sludge?

For example, dividing dry residue mass by wet sample mass gives 20 percent dry solids for 150 g of sludge leaving 30 g of residue. Both masses must exclude container tare, and any loss of other volatile substances during drying cannot be distinguished from water loss.

Calculate with these values