Solid particles in water, such as sand, silt, clay or detritus may clog drip irrigation systems. For this reason, filters that remove all these particles from the water and then input only clean water in the irrigation system are absolutely necessary and essential.
Why is it important to use filtered water?
One of the characteristics of drip tapes is their reduced size, indeed, they can emit water quantity of 0.6 – 1.0 – 1.5 – 2.0 liters / hour per drop point. Consequently, drip tapes can be easily clogged if inorganic solid particles such as sand, silt and clay are present in the system.
Those who use surface water such as, for example, consortium water, river and lake water, face also the problem of organic substances such as algae, mucilage, clayish substances of minimum diameter, that have an even a more obstructive effect than solid particles.
Various types of filters
Different types of filters have been designed to satisfy all needs, basing on the extent of the cultivated land, on how the system has been designed in relation to water availability and, therefore, the overall water quantity used, as well as on water quality:
- Net filters
- Disc filters
- Sand filters
- Hydrocyclone filters
The filtration process of these filters is inspired by the natural flow of water that passes through the soil layers before reaching the underground aquifer.
Water is introduced into the filter, which consists of a generally metallic container with a layer of filtering mass inside, made up of “sand” – preferably a siliceous type– of various sizes, commonly, between 0.3 and 1.5mm, so that the passage holes between them result to be <100 microns. Suspended particles present in the water, both organic and inorganic, are blocked passing through this layer. As the liquid gradually flows down, it becomes cleaner.
The grit can be composed of: sand, gravel or other selected granular materials. The degree of filtration depends on the actual size of the compound and the speed of the water passing through the filter. Eventually the water is drained by further draining elements to come out clean.
Silica sand filter
A particular type of gravel filter is the one that uses silica sand of size 0.3-1.2 mm as a filtering element.
The silica sand layer, which is positioned horizontally, blocks solid particles from the water.
The filtering layer – the main part of the filter – is placed horizontally, occupying a larger filtering surface, so it is certainly a more powerful type of filter than many others.
If the irrigation system is equipped with a fertigation system, it is a good rule to ensure that the fertilizer is injected downstream of the sand filter, and upstream of the safety filter with net and / or discs.
Being a static precipitation filtration system, it is suitable pretty much for any type of filtration of the water coming from:
- Natural layers
Degree of filtration
It is equivalent to a filtration from 40 to 80 microns: however, the parameter of the low speed of water passage through the filtering mass is essential to be respected. The speed should never exceed 0.5 meters/second, to avoid the dragging effect of the particles that, in addition to the physical effect, are stopped by weak electrostatic charges inside the filtering mass.