1. Occurrence
Chloride, in the form of chloride (Cl−) ion, is one of the major inorganic anions in water and wastewater. The salty taste produced by chloride concentrations is variable and depends on the chemical composition of water. Some waters containing 250 mg/L Cl− may have a detectable salty taste if the cation is sodium. On the other hand, the typical salty taste may be absent in waters containing as much as 1000 mg/L when the predominant cations are calcium and magnesium.
The chloride concentration is higher in wastewater than in raw water because sodium chloride (NaCl) is a common dietary component and passes unchanged through the digestive system. Along the sea coast, chloride may be present in high concentrations because of leakage of salt water into the sewerage system. Chloride also may be increased by industrial processes.
A high chloride content may harm metallic pipes and structures, as well as growing plants.