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Introduction to Water Filtration (2019)

It is essential to take into consideration the type of water we consume and use as not all water is the same. As compounds dissolve at different stages of the water cycle, water itself is not entirely pure. In addition to this, chemicals that are added must also be taken into consideration, as there are multiple toxins in water, such as fluoride and chlorine, which have a variety of detrimental and toxic effects on the human body. For instance, fluoride contributes to the calcification of the pineal gland in the brain; there are also studies to suggest how excess fluoride intake can lead to neurological damage, dental fluorosis, thyroid problems and more. As chlorine is a disinfectant, used in cleaning products as well as swimming pools, the implications of what it does to the human body does not appear to be widely understood or acknowledged.


Another factor to take into account is increased industrialisation and inadequate waste disposal, where toxic ions such as arsenic and lead accumulate and dissolve in water. Tap water unfortunately suffers from insufficient regulation, especially when hormones for example are not included in UK water standards, yet waste water recycling is on the increase. 


How one decides how to treat their own water is represented on a simple pyramid model. As such, there are different levels of filtration, which can be seen in Figure 1. As you rise up the pyramid, the impurities are smaller on the Nm scale or become more complex to reduce. 


Figure 1 Water Filtration Pyramid Spectrum

The filtration listed in Figure 1 are physical methods, which employ a porous barrier through which water passes through, resulting in the separation of water and solids. The further up the pyramid, the pores of this medium become much smaller (see Figure 2); this shows that the smaller the pores, the lower the ionic and toxicity range.

Figure 2 Filtration Porous Barrier Comparison

Distillers and Reverse Osmosis (RO) are at the top of the pyramid and sit in the “pure water” category. Distillers boil the water and condense it and remove all dissolved solids and gases above the boiling point of water (100°C). Distillers fall short of being comprehensive for dissolved gases, as well as suffer from huge practicality issues, especially with energy efficiency. RO provides approximately 95% of what a distiller can in terms of dissolved solids, but as they use activated carbon and a nominal RO membrane (0.001-0.0001 microns) are more effective overall for dissolved gases, which represents a group of chemicals which make up the vast majority of the 20,000+ known impurities. 


This is why reverse osmosis (RO) is the finest of all purification and filtration methods, which forces contaminated water through a semipermeable membrane to remove impurities and dissolved ions, including lead and sulphate (See Figure 3), which other filtration systems do not; the process of Nanofiltration for instance, would be able to remove substances such as viruses and bacteria, but not ionic substances that RO is able to achieve. As such, it is the only system to remove all impurities, leaving behind pure water. RO therefore allows for high quality pure water that is safe to drink by reducing contaminants that can lead to health issues. RO removes dissolved compounds due to the external pressure exerted on the water through the membrane. 


Figure 3 Reverse Osmosis

There are also concerns regarding the lack of nutrients in reverse osmosis water, however such deficiencies are often compensated through diet. Tap water does not have much in terms of nutrients either, but an exceptionally high level of contaminants. Another concern is that the RO process may reduce the Ph level of the water to 5.5 making it more acidic, however stomach acid ranges between 1.5-3.5. This is to say that drinking RO water is safe as stomach acid is much more acidic.

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