1. Total hardness category

① temporary hardness. The part that can precipitate when water is boiled is mainly calcium and magnesium bicarbonate.

② permanent hardness. Parts that cannot be precipitated after boiling, such as calcium, magnesium chloride, sulfate and nitrate, etc.

③ negative hardness. When the total alkalinity exceeds the total hardness, the part that exceeds the hardness, such as sodium carbonate and potassium carbonate.

two。 Relationship

① when total hardness > total alkalinity:

Permanent hardness = total hardness-total alkalinity temporary hardness = total alkalinity

SO42- +Cl- +NO3- > K+ +Na+

② when total hardness = total alkalinity:

At this point, there is only temporary hardness.

Temporary hardness = total hardness = total alkalinity

SO42- +Cl- +NO3- = K+ +Na+

③ total hardness

Temporary hardness = total hardness negative hardness = total alkalinity-total hardness

SO42- + Cl- + NO3- < K+ + Na+

In daily groundwater monitoring, the rationality of the data can be tested by referring to the above formula according to the determination results of anion and cation. However, for seriously polluted water bodies, due to the complex composition, the ion concentration relationship listed in the above formula may not be established.

(source: new Horizon of Water treatment)