Understanding Desalination: How to remove salt from bore water

Water security is a massive priority for us, particular in dry seasons. We have a few bores on our property, and at times we find that the water is too salty to use on the vegetable garden, for the chickens or even for cattle water. I have been wondering for a while if there is a cost-effective option to remove the salt, so I was happy to be approached by SWS Pacific with the offer of an article on this subject.  

The desalination units are still relatively expensive at around $6000, however, sometimes water security is worth the investment depending on your other water sources and you overall plan for producing food from your property. I hope you find this article interesting.

If you want to know more about our solar bore pump, I have an eBook here and more information at the end of the article.

The importance of water

Every rural Australian understands the vital importance of water. Without it, we have nothing: no showers, no animals, no vegetables, no life on the land. In much of rural Australia, water is scarce at the best of times and effectively non-existent when the rain doesn't fall for long periods of time. Learning to make do with what you have is just a reality of life on the land, and it is especially true when it comes to water usage.

But sometimes what you have just doesn’t work, no matter how much you want it to. Many rural Australians supplement their needs with bore water – but there are times when the water we get from it is too salty to use for either our cattle, chickens or the vegetable garden.

What is desalination?

Desalination sounds complex but in practice, it is simply the process of removing salt from a water source such as the sea (or a brackish bore) to make it drinkable. There are several different methods that are used to desalinate water, ranging from simple evaporation and condensation (distillation) through to electrodialysis and even microbial desalination.

By far the most widespread and cost-effective method though is reverse osmosis (RO). So, how does it work?

How does desalination work?

All of Australia’s major industrial desalination plants use reverse osmosis to make drinking water and the best way of understanding how it works – without diving back into high school physics –  is by thinking of these plants as giant filters.

These plants take salt water and force it through a semi-permeable membrane (filter) at high pressure. The ‘semi-permeable’ part means that water molecules can pass through to the other side of the membrane but any salt, minerals or other impurities cannot. What you are left with is fresh, clean, life-giving water out one side and salty brine out the other, which can be either stored or disposed of.

Like anything, this process requires energy. At the giant, industrial desalination plants that dot the Australian coastline, that energy comes from the electricity grid, but any source will do. Pleasure cruisers living on their yachts will often power their small-scale desalinators off their onboard batteries, or even with a small diesel generator. 

What does desalination require?

As you’re probably realising, desalination is in fact a fairly simple process, and that holds true in terms of the unit itself – the only thing that changes is the size of the parts involved. Industrial desalination plants produce hundreds of billions of litres of water each year, and accordingly need super-sized components. However most commercial or consumer-grade units actually need very little space, and are more or less the same across the board, no matter what size you’re using.

Water is drawn into the unit through an intake that is fed from your water source – whether that is the sea or a bore – before passing through an initial sediment filter that removes any debris or large particles. This is followed by a fine filter to remove smaller particles and protect the semi-permeable membrane. 

From there, the water is pressurised and forced through the semi-permeable membrane, which filters out the dissolved solids such as salt, along with any remaining chemicals or organic compounds. Some desalinators will have another filter after this to ‘polish’ the water before it passes to a storage tank, ready for the humans, chickens or garden beds that need it.

Where can I find a small-scale desalination system?

Due to their wide range of uses and growing demand worldwide, desalination systems are no longer a hard-to-find specialist product. The model you choose will ultimately depend on your local climate and specific needs so you will want to talk to an Australian supplier like SWS Pacific for help to decide on the ideal system for your situation.

SWS Pacific are water treatment specialists and their range covers every possible use case, from compact marine desalinators for small yachts to large, container-sized systems that are used to create clean water all over the world, from Namibia to Norway.

Their Solar Water Solutions Systems are probably the most remarkable, as they derive all of their energy from solar panels, even on cloudy days, and with no need for expensive battery storage. They can be combined with other power sources to reduce their dependence on solar, but in a country where the sun pretty much always shines, I find it incredibly satisfying that they can run totally independently.

Best of all, their brackish water units have an 85% recovery rate, so you don’t have to worry that you’re losing the majority of your precious water down the drain. In a nation where water stands to become even more scarce and precious than it already is, I really can’t overstate how incredible these systems are, even if you don’t live near the ocean.

To find out more, head to https://www.swspac.com/solar-water-solutions and take a look at the videos and information they have available.