Agronomic considerations to take into account woth the irrigation of eviction water

 

The search for the development of efficient techniques that reduce the obtaining of water has led to the production of fresh water from seawater, becoming an opportunity for agricultural production.

The main advantage of desalination is that it is an inexhaustible water resource and not subject to weather variations,

being ideal in terms of obtaining water especially in areas where it is a resource of scarcity as is the case of the Spanish Southeast, and in which its application in recent years is giving good results as a complement to other water resources to guarantee the future agricultural irrigation.

On the other hand, its main drawback is the cost, which makes it unfeasible for some crops, especially because of its high energy consumption that can lead to the emission of greenhouse gases.

Difference between desalination of seawater and brackish water

Desalination can be of two types, on the one hand by desalination plants, which obtain water suitable for human consumption through the treatment of seawater. And, on the other hand, by means of the desalobradoras plants, that are desalination of underground water or superficial brackish. What makes brackish water different from seawater is that it typically contains lower levels of chloride and sodium ions, but a higher concentration of other ions such as calcium, magnesium, sulfates and bicarbonates; its salinity being much lower than the marina. Brackish waters therefore have an intermediate salinity between fresh water and sea water.

 

Reverse osmosis has become the general reference technology for desalination due to its advantages over others

It presents reduced energy production and consumption costs compared to other techniques applicable on a large scale, becoming the most common water desalination technique in modern crops where science and technology is used for more efficient production. Reverse osmosis results in water of low mineralization and low calcium, mineral and sulfate intake, being not yet suitable for direct human consumption, so before pouring it into the supply to go through a second process becoming desalinated water.

The resulting water composition is not the same in all desalination plants and varies according to the water desalination technique used and the main use for which it was designed. The farmer must modify its composition by means of fertirrigation equipment or other products, producing suitable water to obtain a greater volume to irrigate.

Reverse osmosis consists in passing the salt water through a semipermeable membrane, which allows the passage of water molecules while rejecting dissolved ionic species. It removes nitrates from the water producing a practically salt-free current, which is called “permeate,” and a stream that contains a higher concentration of salts, “brine,” which has those salts that have been rejected by the reverse osmosis membrane. This process allows irrigation even for sensitive crops such as: lettuce, potato, apple, pepper, table grape…

 

The post-treatments that are currently applied have been designed with the objective of adapting the resulting characteristics (osmotized sea water) to the quality requirements suitable for the consumption of human beings. Collected in RD 140/2003.

These after-treatments should be able to guarantee the chemical balance in desalinated seawater. In case of not doing so its low mineralization, it can cause high acidity and strong corrosion, resulting in breaks or seals in the pipes, distribution systems and control and regulation elements.

 

Are you considering watering your crop using reverse omiosis or other methods?

 

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