The agricultural industry uses copious amounts of water on a daily basis. From watering crops to feeding animals to operating machinery, the need for viable and fresh water is large. But in these difficult times of drought and scarcity it can be difficult to obtain viable water for agricultural purposes.
One such way of creating fresh, usable and potable water is via desalination plants, which have proven to be effective in providing relief during times of drought and water shortage.
Desalination refers to the removal of salt and minerals from a target substance, such as soil or salt water. This water can then be used for other applications, such as irrigation.
A desalination plant is a plant which performs this process by pumping seawater into a pump station and then into a holding tank via drum screens. These screens screen water to 0,5mm to remove kelp, sea shells and other impurities.
This water is then passed through six screens or filters before undergoing reverse osmosis for purification. Treated water is fed from the plant to split tanks, where it is chemically treated to remove bacteria and restore the pH balance. It is then able to be used for potable water sources, or for irrigation and other agricultural purposes.
The answer is yes, desalination plants provide water that can be used for agricultural purposes. It is a viable resource during this intense time of drought in our country and can relieve stress in many industries which use water for daily processes.
Desalinated water is replacing the high salinity and brackish water that is found in boreholes across the Western Cape and other provinces. This high salinity makes the water unsuitable for use in irrigation and for feeding and watering livestock.
Desalination plants are able to purify this water, making it suitable for use. Without this innovation, farmers would still be struggling with highly saline water, which is dangerous for crops and for human and animal consumption.
Installing a desalination plant for agricultural purposes incurs many costs, some of which are higher than others. The costs involved include the feed water source, product water specification and operating related costs such as power, membrane element replacement, chemical usage, cartridge pre-filters and maintenance.
Another cost which is not common to every desalination plant is the installation of solar panels. Solar energy may increase the initial capital costs, but will decrease operating costs after time. This option is more popular in remote areas with little access to power lines and in those areas that have an abundance of sun.
The costs can seem high at the outset, but desalinated water is vital for the smooth functioning of any farm or agricultural business. This need for clean potable water outweighs the hesitance towards the cost.
While many crops are highly salt resistant, there are some which are not that sensitive to salt, which means that farmers are able to mix the desalinated water with regular water in order to reduce costs. This gives the water an acceptable level of salinity as not all crops need completely desalinated water.
By mixing the two types of water, farmers do not have to produce as high a volume of desalinated water. A farmer who uses completely desalinated water will run operating costs which reach up to R200 000, whereas a farmer who blends waters will only incur costs of up to R136 000. Because electricity costs are the main contributor to overall costs, blending the water means less electricity usage, decreasing the electricity costs by almost 80%.
Desalination is beneficial, especially to the agricultural industry, as it provides viable fresh water where there may otherwise be no water source. It is a water saving alternative to using brackish water for irrigation. And, because it has a lower salt content, it is not as damaging to the crops or soil. Salts in water can also stunt plant growth, which is something farmers strive to avoid.
Desalination plants provide water which will not increase the salinity of the soil and will, in turn, decrease the adverse effect on crop growth and yield via its negative effects on soil properties.
By utilising desalination plants, farmers and agricultural businesses can introduce a viable supply of water to their land, decreasing the need for using borehole water which may have a high saline content or using water which is needed for drinking rather than irrigation.
The world is in crisis mode and the agricultural industry is the perfect application for alternative water management systems.
