GENERATE YOUR OWN WATER

From the air or from your borehole, here’s how to get self-sufficient

Get your water analysed

A detailed water analysis will be required to assess the current water source. This will ensure that you have adequate pre-treatment and also assist in choosing the correct process for the intended use of the water. Our research put sample testing into two categories. If you just want to pipe borehole water for ablution and washing clothes, you’re looking at spending around R3 000 at your local water testing facility like Aquatico in Gauteng or through the city council in Cape Town. This kind of testing also has a seven working day turnaround.

To test water for the intention of consumption you need to get what is known as a ‘full SANS’ done. This will cost you around R10 000 and there’s a 15 working day processing time. Through this analysis you’ll get the full profile of your water to see how you need to treat it.

Decide what you will be using it for

If you are just using the water for general household irrigation, desalination is normally not required. An inexpensive fine filter will be sufficient to prevent nozzles from blocking.

For household tasks like washing and ablution, desalination is not normally required. The focus here is to remove heavy metals and hardness that could damage plumbing and sanitaryware. This can easily be removed by oxidation (adding chlorine) and media filtration (sand filter).

For drinking water, it advisable that desalination is used; not just for removing salt, but also as an additional barrier against pathogens and other types of pollutants.

Know your energy costs

The higher the salt content, the higher the pressure required to produce potable water. Essentially more energy is required to produce higher pressure and thus energy cost will be higher.

At higher salinities, membrane fouling and scaling also becomes an issue that needs to be considered. Additional chemicals and dosing equipment would be required to reach the desired mineral concentrations.

Corrosion is a factor at higher salinities. This influences the material selection of the piping and equipment and ultimately the start-up cost.

Try harvesting water from air

The Incas built their settlements high above the clouds and harvested dew to serve their water needs. While effective, these passive methods of water collection have low yields compared to powered solutions. On the powered side, though, the story is a bit more grim. Dehumidifiers use a cooling coil to cause condensation, so the process hinges on the coldness of the cooling coil and is actually more energy hungry than proportionate desalination.

By far the most popular solution currently is the wet desiccation method which uses a brine solution to effectively pull moisture out of the surrounding air. Again, the brine must be processed – usually heated to boiling point – and water harvested from that process.

You could also try collecting the waste water from air-conditioners. Harvested water from this process still needs to be purified but at least the production method is a by-product of a different process.

Renewable energy has improved the energy cost of these alternative water-harvesting methods but it’s still relatively more expensive than collecting and reticulating rain, or pumping from a borehole. Unless you live in constant freshwater fog, you should catch and treat as much as you can. PM

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