30.07.2020

How to manage salinity in avocado orchards

CUSTOMER NEEDS AND PROBLEMS

A Chilean avocado producer needed to double their hectares of farmland and the only water available was taken out from a well. The field was in a remote area so any civil works construction would have been very expensive and time-consuming to implement. However, the objective was clear: Achieve maximum profits per hectare of avocado.

  • At AZUD, we know that one of the key factors to achieve optimal production performance is to have low conductivity water because of the low tolerance of the avocado crop.
  • We know that irrigation water with conductivity over 200 µS/cm and over 35 ppm of chlorides may create sodium chlorides or manganese chlorides, that can burn the avocado leaves causing defoliation, which can lead to lose 20% of production.

WATER TREATMENT SOLUTION

To solve both problems, AZUD proposed installing a containerized desalination plant, avoiding the need for any civil works, and capable of producing water with concentrations below 30 ppm. In this case, the water production flow rate was 100 m3/h (440 GPM) and the well water quality was very poor, as it had iron and manganese (2-3 ppm) and very high suspended solids, so a complete pretreatment was needed previous to the reverse osmosis membranes.

In this process, it was very important to eliminate iron and manganese because these elements in a concentration above 0.1 ppm can cause mechanical damage to the reverse osmosis membranes, which could increase the salts concentration at the permeated and not meet the water quality needs for optimal avocado crop production.

  • The first stage of the treatment line was to oxidize at the inlet tank to precipitate the dissolved iron from Fe2+ to Fe3+, this way it can be physically retained.
  • After the oxidation, water is divided into two containerized lines with the same pretreatment:
    • First, water goes through a self-cleaning disc filtration equipment, with air-assisted backwash to improve the cleaning performance, eliminating the precipitated iron and manganese, and other suspended solids present in the water.
    • After the disc filter, water goes through a multimedia filter of silex, anthracite and pyrolusite. The pyrolusite will oxidize the iron and manganese that has not previously precipitated and would be retained by the silex and anthracite media.
  • Finally, the pretreated water goes into a third container equipped with microfiltration cartridges and with high performance and low energy consumption reverse osmosis membranes, obtaining the perfect water quality to be mixed with the nutrients needed for the avocado crop.

The complete desalination plant was equipped with remote control access allowing to have 75% less maintenance visits, complete awareness from our engineering office, optimizing diagnosis time, and intelligent preventive and predictive maintenance.

At AZUD we are aware that high water quality is needed to obtain maximum performance of your crop, that is why our mission is to design and propose a cost-effective and optimized water treatment solution.

Have a look at this video for more information about the design of the water treatment plant:

https://youtu.be/-2v7xK-B3oU

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