We use the term ‘Chloride’ in the water industry to refer to either a Chloride ion, a negatively charged Chlorine atom, or non-charged chlorine atom that shares a single bond with the rest of the molecule it is attached to.
Chloride is a naturally occurring element that is vital for life. It can generally be found in most environmental waters, usually with other minerals such as calcium or potassium, or as part of salt like sodium chloride. Chloride is a substantial component of dissolved solids.
Drinking water
Chloride is an essential element for human life and larger quantities in drinking water are unlikely to cause any serious issues beyond a foul taste and potential odour. However, in terms of the distribution system, elevated levels of Chlorine can cause corrosion for pipes, plumbing and pump equipment which will have both financial and operational repercussions.
Environmental waters
From an environmental freshwater perspective, whilst a relatively low level of Chloride ions is expected, is has become far more of a concern in recent decades. Since the introduction of using salt as a road de-icer, chloride concentration in freshwaters such as lakes, streams and rivers has increased. Whilst a competent de-icer, salt is then easily washed into water sources where it dissolves into chloride and sodium ions.
In freshwater, it is normal to see Chloride concentration 1-100 ppm, where chlorides have come from the dissolving of rocks containing salt in underground aquifers or similar. Chlorides are monitored as an indicator of water quality as, even slightly elevated amounts, they can be toxic to aquatic life. Humans can have a significant impact on the chloride levels, with the use of salts for road de-icing a common cause of an increase in Chlorides as they are washed off into water courses. They can also be found in human waste and as a by-product of some water treatment processes such as industrial water softening.
Chloride in streams cause the restructuring of community biotic structure as well as the potential to kill both flora and fauna inhabiting the environment. When subject to increasing chloride levels, both diversity of aquatic life and its productivity can be affected across all trophic levels. Particular concern is given when freshwaters are in a low flow phase as this can increase the impact of Chloride ions as they become more concentrated.
The Proteus Chloride ISE is a solid-state ISE has a sensor surface which is specific to chloride ions. At the surface, contact with chloride ions will produce different voltage potentials which the sensor detects and compares with the reading from the separate reference electrode to produce a concentration of chloride ions.
