hardnesscausing

Hardnesscausing substances are dissolved minerals that raise the hardness of water by supplying multivalent cations, mainly calcium (Ca2+) and magnesium (Mg2+). In natural waters, hardness results from the weathering of rocks and minerals that liberate Ca2+ and Mg2+ ions; trace contributions may come from iron, manganese, strontium, and barium, as well as from salts of these metals such as sulfates and chlorides.

Hardness is often categorized as temporary (carbonate) hardness, due to Ca2+ and Mg2+ with bicarbonate; permanent (noncarbonate) hardness from sulfates and chlorides. Temporary hardness can be reduced by boiling, which converts bicarbonates to carbonates that precipitate as scale; permanent hardness requires chemical treatment to remove or convert sulfates and chlorides.

Measurement and values: hardness is commonly expressed as mg/L as CaCO3 or as degrees of hardness. Common thresholds are: soft (<60 mg/L as CaCO3), moderately hard (60–120 mg/L), hard (120–180 mg/L), very hard (>180 mg/L).

Implications: elevated hardness can lead to scale buildup in pipes, boilers, and appliances, and lowers soap's effectiveness. It can affect taste and wear but has little consistent health risk; calcium and magnesium contribute to dietary intake. Treatment options include ion exchange softening, lime-soda ash softening, reverse osmosis, or precipitation with lime and washing soda.

Hardness-causing in environmental and industrial contexts is often controlled to balance scale control, efficiency, and mineral nutrition.