What commonly increases chloride concentration in wastewater?

Chloride concentration in wastewater is often influenced by various anthropogenic sources, with dietary intake and the use of water softeners being the most significant contributors.

When chloride is consumed through the human diet—primarily from salt (sodium chloride)—a portion of it is excreted through urine, leading to increased chloride levels in wastewater. Additionally, water softeners, which are commonly used to treat hard water, exchange sodium ions for calcium and magnesium ions, resulting in a discharge that is rich in chloride. The discharge from these water softeners can significantly boost the chloride concentration in the wastewater stream.

While other factors like heavy rainfall and industrial discharges may also influence chloride levels, they do not have as direct and consistent an impact as the dietary intake and water softeners do. Natural mineral dissolution typically increases chloride concentration in natural water bodies rather than wastewater specifically.