Total solids are determined measuring the dry content in water or solvent by evaporating all the water using a solids analyzer from the sample. Total suspended solids are measured by filtering the sample prior to the measurement and subsequently determining the amount of solids retained in the filter, the result is expressed in mg/l of solids. Total dissolved solids are accessible by evaporating all the water from the filtrate (liquid that passed through the filter). An example with detailed description can be found in our waste water application note:
Total Solids in Wastewater Treatment Process