WATER HYGIENE & SAFETY
remove as many chemical ions as possible from the water before it feeds into the reverse osmosis unit. Pre-treatment – which is responsible for the removal of calcium ions, iron, manganese, silica, and carbon dioxide – addresses either the hospital’s ‘raw’ water supply, or partially treated water. Depending on the site’s location, the mains water could be classified as ‘hard’ water, simply signifying that the water supply contains an abundant amount of chlorine and magnesium ions, which, when allowed to build up, or when heated, can cause a build-up of limescale in pipework, resulting in damage to the system it is feeding. Hard water is very easily treated through pre-treatment and other water treatment technologies such as reverse osmosis. There are numerous types of pre-
treatments available, depending on the desired quality of water required for use. Each pre-treatment is responsible for removing different chemical ions from the water supply, which is why, more often than not, pre-treatment technologies are combined. The most common forms of pre-treatment used in healthcare are sand filtration, carbon filtration, ion exchange (softeners), and organic scavengers. Pre-treatment is not only used to treat the water, but also designed to protect the system, which in return results in an
increase in the longevity of the system and its components.
Carbon
Carbon is one of the most used pre- treatments, as it removes impurities in terms of both chemical and microbiological sediments. This process occurs through absorption, in which the contaminants are trapped inside a carbon particle that can be
described as being like a pore.11
While
different types of carbon can be used, granular activated carbon (GAC) is used most frequently, as it has a larger pore surface, and can thus absorb more compared with other types.11
Figure 4: The ion-exchange process.12
frequently used to remove organic ions from a water system.
The carbon
acts as a catalyst, as it is used to trap the water contaminants. However, it does not trap salts, other important minerals, and some microorganisms. Carbon is
Ion exchange Softener resin is used to break down the chlorine and magnesium ions that cause the raw water to be classified as ‘hard’ water. The resin in the softening vessel can
UNTREATED WATER
Magnesium Calcium
TREATED WATER
Resin Swap beads
Sodium ions
Magnesium
Calcium
October 2022 Health Estate Journal 121
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