We all know the change that the introduction of localized irrigation has brought about. The advantages for horticultural and fruit crops above all, suppose an efficiency and water saving without equal. It also has its drawbacks as we saw in the entry of drip irrigation problems . One of them is clogging and to avoid it, filters are the solution. Today we cover in a general way some filtering systems.

EVERYTHING DEPENDS ON THE EXPLOITATION

When we talk about filters, we are talking about irrigation networks for farms with clearly business objectives, not domestic ones. A domestic drip irrigation network for an orchard or garden usually does not exceed 200 meters of hose with a few dozen drippers and the irrigation frequencies are somewhat lower assuming a lower probability of blockages. On the other hand is profitability. When 1, 10 or 20 drippers are clogged in a garden, orchard or private estate, they are seen, cleaned and in the worst case, we puncture new drippers. If, in addition to this, we take into account that for the garden or balcony, we sometimes use the mains water, then the filters no longer make any sense as you can imagine. Filters are expensive systems to maintain depending on the type of filter and the frequency of its maintenance.

On the other hand we have large farms where we have hundreds of kilometers of pipes, thousands of drippers and water from ponds or wells that, without any doubt, will have significant amounts of suspended particles and other elements that prevent uniform irrigation and the clogging of hundreds or even thousands of droppers. In these cases, the profitability of a good filtering system is more than proven and there is not one, but several filters necessary to avoid clogging situations every two by three. One of the factors that most affect irrigation uniformity is precisely the efficiency of the filtering equipment. Let’s see some important filters for irrigation networks.

SIMPLE PHYSICAL BARRIERS

GRIDS

It is the simplest system that is usually located in ditches or open conduits, for example to retain large elements such as branches, leaves, stones …

DECANTERS

When water is channeled either by pipe, ditch or similar, it carries a speed. The speed implies dragging of particles of different sizes and that must be avoided as far as possible. For them, the decanters fulfill this function. They are successive deposits where the water loses speed and the sands (mainly) end up settling at the bottom.

PRE-FILTERING

The pumps are what drive the water through the irrigation networks. The internal turbine that moves the water ends up suffering wear, and the more particles that enter, the shorter its useful life. Therefore, any precaution is little. Leaves, branches and small particles can also enter the suction zone of the pump, even if there are decanters and grates. Therefore, a small mesh in the form of a basket in the suction zone will prevent the entry of a large number of elements that can considerably shorten the useful life of the pumps.

SOMEWHAT MORE COMPLEX FILTERS

HYDROCYCLONES

Its very name indicates what it is going to do. Cause a rotational movement inside the tank. To achieve this rotational movement, the entry of water is made tangentially generating a centrifugal force that displaces the solid particles towards the wall of the hydrocyclone. The particles will fall into a sediment accumulator at the bottom while the water will come out clean from the top of it thanks to this centrifugal force. This type of filtering is widely used in well water extractions . It does not suppose a great loss of load in the network and the efficiency is very remarkable . On average, almost 98% of particles smaller than 100 microns are separated.

SAND FILTERS

There are more or less complex ones, with their own designs for each company that makes them more or less effective, but the base and the foundation of operation of all is the same. A bed or bed of filtering sand (usually silica among other components) that allow the water to go through the bed slowly, leaving behind a multitude of particles, mainly organic. For this reason they are very useful and necessary when the content of organic matter in irrigation water is high or a really fine filtration is wanted.. The advantage is that the contact surface with the filtration bed particles is very high, achieving a very effective filtration. The pressure drops are obviously higher (up to 3 m pressure drop) and can be doubled if the filter bed is not clean and in optimal condition. They are expensive and require maintenance (cleaning the bed). The way to know when to do this is by installing pressure gauges before and after the filter unit. The pressure differences will give us the moment of cleaning.

MESH FILTERS

This is it. In tights. They are usually cartridges or housings that have metal or plastic meshes with different light diameters inside .

RING FILTERS

You hear a lot about ring filters. That’s because the filtering effectiveness is acceptably good compared to the price. Sand filters are often expensive and not profitable if the farm is not large enough and the flow rates are not too high. The amortization and maintenance of sand filters is more expensive. Ring filters are often a substitute for sand filters in smaller installations. They are also installed as secondary filter elements.It consists of a cartridge with rings or discs grooved on both sides. When they overlap with each other, they form the conduits through which the water passes. They retain a large amount of sediment. Like all filters, they must be washed when they become clogged. It is done manually or by backwashing, although there are also automatic ones, being much more comfortable and efficient when washing at the optimal time.

These filtering systems are the most used. Here we leave you a general classification of filters based on the particles present in the water. It must be taken into account that when designing an irrigation installation, one must delve more into the type of installation, size of the network, characteristics of the water, size of the farm, flow rates, pressure drops, maintenance, cleaning and many more variables to correctly choose the filter system (s).