One of the main problems connected with the drip irrigation technique is represented by the possible occlusion of the dispensing devices caused by material carried in suspension by the water current.
It is therefore necessary to make a careful analysis of the water supply source used, in order to know the values of pH, calcium, magnesium, total salinity, sodium, potassium, iron, manganese, boron, bicarbonate, carbonate, chloride, sulphate, sulphide , quantity and size of suspended solids. In particular, the suspended solids in the water network include particles of variable size, such as sand grains or clay particles, living organisms including bacteria and algae, and a wide variety of other substances transported in suspension.
Qualitatively it is possible to describe the causes and distinguish the types of clogging into:
Physical clogging
This type of clogging is due to inorganic suspended solids (silt, sand and clay) and organic suspended solids (algae, remains of aquatic plants and animals, etc.), which can accumulate and block the regulator.
Chemical type clogging
This type of clogging is caused by the precipitation of calcium and magnesium carbonates and iron and manganese oxides. Precipitation can be favored by the increase in pH and temperature or by the presence in solution of other ions, such as those brought by fertilizers.
Biological clogging
This type of clogging results from microbial activity which can produce organic sludge, filaments and deposits.
Classification of emitters
In relation to the sensitivity to obstruction phenomena, it was proposed by Karmeli and Keller[1974] the following classification:
- “very sensitive” emitters those with passage sections with a diameter of less than 0.7 mm
- “sensitive” emitters those with a diameter between 0.7 and 1.5 mm
- “insensitive” emitters those with a diameter greater than 1.5 mm
Treatments
Since the occurrence of clogging phenomena in micro-irrigation systems is particularly fearful, as even a minimum percentage of clogged drippers can significantly reduce the uniformity of delivery, it is necessary to proceed through an appropriate water treatment (chemical or physical; the treatment chemical can be performed alone, or sometimes, together with the physical one) which, by improving its qualitative characteristics, reduces the risk of occlusion. That is, they can be mitigated with the use of dispensers that are not very susceptible to clogging by using dispensers with large passage openings.
Chemical treatment
Chemical treatment consists of adding one or more chemicals in order to control the development of organisms and chemical reactions. Chemical treatments commonly used in drip irrigation systems include the addition of chlorine and / or acid.
Physical treatment
The physical treatments commonly adopted for the removal of organic solids, filamentary materials and algae that may be present in surface waters, involve filtration processes using devices equipped with filter elements (mesh filters) or equipped with elements consisting of overlapping discs ( disc filters), or even through granular filtration (sand filters). Suspended solids that may be present in deep (well) water can be removed by centrifugal separators, sedimentation tanks, or some combination of the above systems.
