Why Test for Total Solids?
Total solids (somtimes called total residue) is related to turbidity, except that it includes not just suspended solids, but also dissolved solids such as the mineral ions calcium, phosphorus, iron, sulfur and bicarnonate. A certain level of these ions is essential for life. Cells also depend on the density of total solids to determine the amount of water that flows in and out of the cell.
However, too much dissolved solids in water can affect humans by inducing a laxative effect and giving the water a mineral taste. Increased total solids has a similar effect to turbidity in that water clarity is reduced, water temperature can rise, oxygen levels can fall as a result of less photosynthesis, and solids can bind to toixc compounds and heavy metals.
In summary, testing for dissolved solids involves weighing a clean 300ml beaker to the nearest mg. Fill the beaker with test water and evaporate off the water. Weigh the beaker again with the resulting residue. Then subtract the two results to determine the amount of milligrams of residue per liter of water.
Refer to the Field Manual for Water Quality Monitoring for details on performing this test.
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