The sixties: sand filters made of metal parts reigned supreme
During this period, the number of products on offer was very limited. They evolved almost exclusively around sand filtration methods, or even screen filters, with metal (often galvanized) parts. The filters were nearly always cleaned manually, i.e. dismantling the product and cleaning the filter components by hand (screen filters) or reversing the direction of flow as in the case of sand filters in order to remove elements trapped during the filtration process. The way of determining when the manual cleaning process had to be carried out was very haphazard: ideally conducted via a regular and careful observation of the difference in pressure existing upstream and downstream of the filter. Unfortunately, it as often initiated when the pressure downstream had dropped to a point where there was a risk of irrigation being stopped… often when the critical threshold had already been reached, so therefore it was too late.
Furthermore, for the sake of convenience and pragmatism, the trend was to have one single large filter tank… it was not uncommon to see sand tanks with a diameter of 60’’ (1.5m) or more. These systems required a lot of hydraulic energy to backwash effectively.
The eighties: screen filters complement the existing offer
Weary of the constraints imposed by this star product, the sand filtration system, the users began complementing or even replacing their sand filter systems with screen filters. The housing was at that time made of powder-coated steel for large dimensions (above 3″) whereas plastic (acetal or polypropylene) was being offered for smaller sizes. We also saw the appearance and popularisation of small-sized screen filters for agriculture and parks and gardens.
The nineties: the arrival of the disC technology combined these two concepts
An Israeli company began offering a product that combined the benefits of sand filtration (good efficiency when filtering particles of biological origin) while offering a facility for cleaning the filtering elements used in the screen filter range of products. The material in question was a technical polymer of the type used with certain screen filters. The plastic processing management technique was, therefore, a great asset for the manufacturers of light-weight filter elements in large volumes, allowing clear economies of scale to be achieved.
This was also a period when the systems were being sold increasingly in battery form, i.e. a number of small capacity filter elements positioned in parallel rather than having one single large capacity filter. This allowed for the sequential backwashing of each filter element, one after the other, which improves the efficiency of the backwashing, even under restrictive conditions, in terms of pressure and flow-rate and it also makes the system more compact and thus easier to transport.
The two thousands: the fully automatic option
The controllers have also made great progress, having now become a part of a large number of stations which, as a result, have become automatic! A pressure differential sensor then permanently measures the difference in pressure upstream and downstream, and starts at the right time a sequential backwash of the parts that make up the filtration station. This makes life a lot easier for the users and ensures that the system runs smoothly.
This revolution thus provided a boost to concepts that already existed:
• the sand filtration station is simplified: the large tank of 60” or more is replaced by 4 smaller tanks (e.g. 4 x 24” tanks) and positioned in parallel because the controller can manage the complex task of organising the sequential backwashing (one tank after the other).
• the development of automatic screen filters: these have greatly benefitted from this automation because, at the right moment, they begin the backwashing process which prevents the avalanche effect that is so characteristic of this kind of ‘surface’ filtration (when the screen progressively becomes clogged by the particles, the water can no longer pass through the unclogged orifices and the whole unit becomes blocked very quickly with the risk of the mesh becoming twisted or even the screen breaking up).
• disc filters are more popular: they have become ultra-compact and easy to use by being light and simple (all parts are now made of plastic, even the backwash valves or manifolds) and more efficient (several elements in parallel) while automation allows them to be controlled perfectly.
Post-two thousand: a period when plastics have challenged the use of steel
The market has become more mature. We can now find all sorts of materials used in the filter components: powder-covered steel for corrosion resistance (because it allows for greater flexibility when manufacturing a specific or customised filter), or even technical plastic components for their light weight and also the reduced cost achieved by large-scale production. Of course, the plastic products are made with moulds, which involves a higher initial investment from the manufacturers. However, the global irrigation market is expanding and these large volumes of products produced will easily be absorbed into the market. There is fierce price competition between the traditional manufacturers and a number of outsiders have also entered this tough market (often copying the products of the leaders).
As proof of the maturity of the market, the traditional leaders are now being challenged and the technological gap is less, although it still exists. The experience gained in the promotion, installation, use and maintenance of the product now makes all the difference.
Globally, the three technologies are now accessible in the two materials but in certain cases the material used could increase the benefits while also at times creating certain limitations:
Ultimately, a certain consensus has emerged with regard to the experiences and practices observed:
• sand filters: becoming easier to implement (designed to use common elements of smaller dimensions), they are often constructed of metallic materials (but experiences from the swimming pool industry shows that plastic can be an alternative in the future) and they should always be accompanied with a device that automatically controls the backwashing in order to avoid the risks associated with a medium that could fall apart under the presence of high pressure differentials. They are less difficult to manage than in the past if the strict rules are adhered to and the automatic process is available.
• screen filters, requiring less pressure and flow for backwashing, are economic when made of a powder-covered steel material and one single filter element (mechanically they are far simpler and more reliable) and in certain cases they can be optimised via an effective automatic process which is easily configured. They are mainly reserved for use as the main filter for water with a low level of contamination or even ideally as secondary filters, as they are simple and economic and, in this case, they offer an alternative option.
• disc filters are effective when they are made entirely of plastic with the adaptability provided by a design based on several standard components placed in parallel and controlled by a common automatic process. Being multi-purpose, they can be used on almost all agricultural applications in France and worldwide.
These three technologies all hold an important place on the world market because using any one of them on its own is insufficient to meet all the expectations of the agricultural or parks and gardens market, in terms of the type of emitter used or even the competence of the installer or the end user.
The coming years: for each problem there is a particular solution
At NETAFIM, we are not focusing on any particular one of the three solutions nor any particular material, rather we select the advantages of one or the other (or even a combination of all three sometimes) in order to best respond to each specific requirement.
In some countries, such as the United States, irrigation water is pumped up from rivers that are subject to the vagaries of the climate. In this case, we often go for the advantages of the adaptable and evolutionary sand filtration system for the main filter (with the possibility of increasing the filtering capacity in the future according to the needs), and then we use disc filters for filtering the water in the field (automatic or manual filter stations).
In certain countries, such as Israel, where recycled wastewater is used, disc filters work wonders because they reduce the risk of biofilms or bacteria developing, which can at times be observed in sand filters (stagnation in the filtering medium).
On the other hand, in certain Latin American countries, when water is drawn from deep wells, automatic screen filters are widely used because they are economic and sufficiently efficient and very reliable for the limited local distribution network and type of end user.
Ultimately, it should be borne in mind that it is essential to take into consideration the distribution chain (the professionals responsible for selling the product in the field and also providing assistance on the day.
If the distribution network is developed and very professional, then technical solutions, such as automatic disc filtration, can easily be proposed as part of the offer. If there is not a robust distribution setup in place, then a more traditional solution may be preferred, such as a basic sand filter with a more easily repairable metal frame rather than one made of plastic.
In future years: smarter technology to provide optimum the management of filter devices
Finally, one last element has become crucial for producers worldwide: the perfect match for these products to protect the localised irrigation systems within the framework of the overall project, achieving a good interaction between all the components of this project, with remote management being possible in the long term for these installations and, in particular, the filtration part of the project. This interaction is now possible thanks to new centralised automated products, which, on the same technical platform, are now providing the possibility of managing the filtration process itself (in particular, the backwashing of each filter element) as well as the other aspects (irrigation scheduling, fertilisation process, crop monitoring…). They also allow the user to check that the filters are fully functional (SMS alerts can be set and sent), that the backwashing process is triggered at exactly the right moment without causing any unnecessary wastage of water and energy (the retrievable history of the filters can even be recorded) with the possibility of detecting breakdowns remotely (e.g. monitoring the pressure upstream and downstream of the filter) … It is, without doubt, in these areas that the potential for innovation is strongest, this intelligence being able to optimise the performance of the filters, their interaction with economic imperatives and, therefore, the protection brought to the irrigation system and consequently this benefits the crop being grown. The filters are, therefore, not only mere products but rather a real line of defence for the initial investment made by the end client.
Author : Netafim France