How to clean water

There are 3 different categories of ways of cleaning water: 1) Filtering, 2) Changing the properties and 3) distillation (evaporation/condensation).

1) Filtration

Regardless of type, shape and size – filters do the same thing: Holding things back on one side of a membrane and letting smaller things pass through the given pore size. That means that all filters have a certain lifespan before clogging – and then they need cleaning/exchanging.

Particle filters

These filters come in many different types, ranging from your coffee filter, to sandfilters, to various membranes. 

Carbon Filters

Activated carbon is particularly good at adsorbing organic compounds. Some carbon filters even work as a particle filter.

The ability to hold back dissolved contaminants is called adsorption. The efficiency of the carbon filter depends on particle and pore size, surface area, surface chemistry, density and hardness. Quality manufacturers have different qualities and even dedicated filters for certain usages.

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Reverse Osmosis (RO) – household/sub counter

Reverse Osmosis is a filter technology with tiny pores in a membrane. To get water molecules to pass, high pressure is needed – from a few bars in a sub counter filter to several hundreds of bars in industrial applications. Ro is today the preferred desalination technology on an industrial scale.

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Aquaporin filtration

This is a relatively new technology with promising aspects.  Aquaporins, also called water channels, are integral membrane proteins from a larger family of major intrinsic proteins that form pores in the membrane of biological cells, mainly facilitating transportation of water between cells. The cell membranes of a variety of different bacteria, fungi, animal and plant cells contain aquaporins through which water can flow more rapidly into and out of the cell than by diffusing through the phospholipid bilayer.

The technology is quite new (2003) and first filters are now on the market (2018).

2) Changing water properties

Unlike filtration, these methods change the contents in water – but do not remove them. 

Ultra Violet “filtration”

UV light effectively destroys bacteria and viruses. So, leading contaminated water through a certain energy level of UV light, will kill and/or disrupt the organism’s genetic material.

It makes sense to use this simple technology in the final stage of a water cleaning system, just to make sure that if any living matter should grow inside the system/piping/dispensers/bottles etc – then an UV-light is a good extra security.

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Ozonation

Ozone is a naturally occurring component of fresh air. It can be produced by the ultraviolet rays of the sun reacting with the Earth’s upper atmosphere (which creates a protective ozone layer), by lightning or it can be created artificially with an ozone generator.

The ozone molecule (O3) contains three oxygen atoms whereas the normal oxygen molecule contains only two. Ozone is a very reactive and unstable gas before it reverts back to oxygen. Ozone is the most powerful and rapid acting oxidizer man can produce and will oxidize all bacteria, mould and yeast spores, organic material and viruses given sufficient exposure.

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Boiled water

In an emergency, boiling is the best way to kill parasites, vira or bacteria.

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Chlorination

Water chlorination is the process of adding chlorine (Cl2) or hypochlorite to water. This method is used to kill certain bacteria and other microbes in tap water as chlorine is highly toxic. In particular, chlorination is used to prevent the spread of waterborne diseases such as cholera, dysentery, and typhoid.

Chlorine in water is over three times more effective as a disinfectant against Escherichia coli than an equivalent concentration of bromine, and over six times more effective than an equivalent concentration of iodine.

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3) Nature’s way: Distillation

Nature has provided water cleaning since…ever. The water cycle is what is keeping us alive and what makes all life possible. Collecting water vapor is what it is all about. Rain. Same-same. 

Distillation

Distillation is the core technology of any WaterStillar system:

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Dehumidifiers

Generally, dehumidifier water (including AC’s) is considered a rather clean kind of greywater: not suitable for drinking, but acceptable for watering plants. The water may contain trace metals from solder and other metallic parts. The trace metals may pose a danger if used on edible plants, as they can bioaccumulate. However, the water is usable for irrigation of non-edible plants.

Various pathogens, including fungal spores, may (or will) accumulate in the water, particularly due to its stagnancy. Unlike in distilled water production, the water is not boiled, which would kill pathogens (including bacteria). 

Food-grade dehumidifiers, also called atmospheric water generators, are designed to avoid toxic metal contamination and to keep all water contact surfaces clean. The devices are primarily intended to produce pure water, and the dehumidifying effect is viewed as secondary to their operation. Still, the working principles lead to water, that needs careful post-treatment to be used for drinking (carbon, UV, ozone etc). 

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