Microirrigation Systems for Vineyards
Filtration Systems
Filtration equipment ensures that organic and inorganic particles in the system are removed, protecting the irrigation system from clogging. If chemicals or acids must be added for water treatment, ensure that you determine whether the materials should be injected before or after any filtration equipment. Some chemicals will react with the materials used to manufacture the filters. Water-soluble fertilizers are typically injected after the filters and must be in solution. Chemicals must be tested before being injected into the irrigation system. Sometimes, a combination of more than one type of filter may be necessary. Two sets of filters are often recommended. The primary filter removes suspended material from the water. A smaller-capacity secondary filter, installed downstream from the primary filter, protects the irrigation system in the event of primary filter failure. The degree of filtration is typically specified in microns or mesh. Four primary methods are used to filter water for irrigation systems: centrifugal sand filters, sand media filters, screen filters, and disk filters.
Centrifugal Sand Separators
Centrifugal sand separators (Figure 14.5) are not actually filters but are used as pre-treatment devices for other types of filters. A centrifugal sand separator removes larger particles of sand, silt, or other abrasive grit particles that can lead to the premature degradation of irrigation system components. These contaminants can reduce the efficiency of the irrigation system equipment by plugging and clogging valves and emitters. A sand separator is effective in removing up to nearly 98 percent of particle sizes that are too large to fit through an equivalent 200-mesh (0.074 mm) filter. The device does not remove organic material.
Sand Media Filters
Sand media filters (Figure 14.6) have been widely used in microirrigation systems. They consist of fine gravel and sand of selected sizes placed in pressurized tanks that filter contaminants as the water flows through the filtering media. The main body of the tank contains sand, which is the active filtering ingredient. The sand is placed on top of a thin layer of gravel, which separates it from an outlet screen. Selecting the smallest medium possible for a given installation is a common practice; however, a larger medium may sometimes be desirable. The larger medium generally causes less pressure drop and has a slower buildup of particles.
Disc Filters
Disc filters (Figure 14.7) are relatively new devices that possess traits of both sand media and screen filters. Disc filters are better than screen filters for retaining algae. The screening element of a disc filter consists of stacks of thin, doughnut-shaped, grooved discs, forming a three-dimensional filter cartridge. The stack is enclosed in corrosion and pressure-resistant housing. Each disc contains grooves, molded into its surface. These molded grooves provide for the mesh (or micron) rating of the filter.
Screen Filters
Screen filters (Figure 14.8) are most frequently used for removing physical contaminants. They are efficient in removing very fine sand from irrigation water, but tend to clog rapidly with heavy loads of algae and other organic material, and are not as efficient as sand media filters. Screen filters are sometimes used as secondary filters, located downstream of sand media filters. The basic parts of a screen filter are the filter screen and basket.
Arrangement of Irrigation Filters
The correct order for placing irrigation filters is generally from coarsest to finest filtration (Table 14.2), with the goal of removing larger particles first to protect subsequent, finer filters from premature clogging or damage.
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