Total Dissolved Solids. The total dissolved solids (TDS) are the solids in the filtrate from the
TSS test. The liquid which passes through the TSS filter is collected in a weighed dish and evaporated for an hour at 180°C ± 2°C. The dish is then re-weighed with the TDS equaling the difference between the dish weight before and after filling with filtrate and drying, in mg per liter of filtrate.Again, this inexpensive test can be run in less than two hours and will indicate the chemical or biological solids in a wastewater which cannot be removed through settling, floating or filtration.