How can inorganic dissolved solids be effectively removed from waste streams?

Inorganic dissolved solids are typically ions and small molecules that cannot be removed through conventional methods like filtration or settling because they remain dissolved in solution. Ion exchange is a highly effective method for removing these substances from wastewater.

This process works by exchanging undesirable ions in the water with more benign ions on a resin. For example, if the water contains high concentrations of sodium ions, the ion exchange resin can replace these with calcium or magnesium ions, which are less problematic in many contexts. This method is particularly effective for softening water and removing specific contaminants, including heavy metals and other charged inorganic species.

In contrast, the other methods—filtration, settling tanks, and bacterial digestion—are not effective at removing dissolved solids. Filtration can only accomplish separation of larger particles and suspended solids, while settling tanks rely on gravity to separate heavier solids from liquids, which does not apply to dissolved substances. Bacterial digestion is used to treat organic matter and is ineffective against inorganic compounds. Therefore, ion exchange stands out as the appropriate choice for removing inorganic dissolved solids from waste streams.