Total Dissolved Solids. The weight per unit volume of water of suspended solids in a filter media after filtration or evaporation.It can be reduced using reverse osmosis systems or using seawater reverse osmosis. Total dissolved solids meters gauge all existing anions and cations within the water, which include sodium, nitrate, phosphate, calcium, and magnesium. TDS in elevated levels do not describe the health safety of water, but it does outline problems regarding inconveniences and artistic taste, including taste, blemishing, or precipitation.