Abstract
The concentration of calcium and magnesium ions is called water hardness. It is one of the parameters that describes the quality of water. The carbonate mineral deposits are responsiable for the most hardness in water. A study has been carried out on the determination of the hardness in water of different districts in Janzur-Libya. In this study the ASTM D-1126 was used as a Standard Test Method for Hardness in Water. The results showed that the level of the total hardness in water was from 420 mg/l to 1300 mg/l. The limit of the World Health Organisation is 500 mg/l which means the hardness in water of many districts in Janzur-Libya is over the limit and in general the water is very hard. The level of the calcium hardness in water was from 190 mg/l to 460 mg/l and of the magnesium hardness in water was from 230 mg/l to 840 mg/l.