Usually, the micro-irrigation system is the first hub consisting of water pump, instrument, control valve and filter, and the pipe network composed of the main pipes, branch pipes and capillary pipes for the task of water distribution and distribution, and various forms of water supply directly to the root of the crop. The emitter is composed of three parts. Among them, the emitter is the key equipment in the final stage of the irrigation task, which is called the heart in the micro-irrigation system. In order to make the emitter work normally, the selection and working performance of the filtration equipment is crucial. If the selection of the filtering equipment is wrong, the irrigator will be blocked, which will cause uneven water distribution and system performance degradation, and even cause the entire micro-irrigation system to collapse, which will require a lot of manpower and financial resources to eliminate the blockage or rebuild the system.
There are several types of filtering devices:
(1) The trash rack (screen) is mainly used in irrigation water sources such as rivers, reservoirs and other large-sized debris, intercepting dead branches, weeds and other large floating objects to prevent debris from entering. In a sedimentation tank or reservoir. The trash rack is simple in structure and can be designed and manufactured according to the actual situation of the water source. The primary sewage screen (net) is a mesh type trash rack installed at the inlet of the water source in the water source, that is, the primary purification treatment facility, which is mainly used for sludge containing water sources such as water plants, sundries and algae.
(2) Sedimentation tank Sedimentation tank is one of the primary treatment facilities for water purification of irrigation water. Although it is a simple and ancient water treatment method, it is an effective and economical treatment to solve the water purification problems of various water sources. In this way, the role of the sedimentation tank is manifested in two aspects; 1 removal of solid matter present in the water. When there is too much sediment in the water, the screen filter and media filter used will be ineffective due to frequent flushing, in which case the sedimentation tank can act as a primary filter. 2 Remove iron material. The carbon dioxide dissolved in the groundwater is reduced in pressure in the sedimentation tank, the water temperature rises and escapes, and the pH of the water increases, causing oxidation and precipitation of the iron species.
(3) Centrifugal filter (also known as sand separator) is mainly used to remove well cement sand. The working principle of the centrifugal filter is the centrifugal force generated by the high-speed rotating water flow, which separates the sand particles and other heavier impurities from the water body. There is no filter screen inside, no detachable parts, and the maintenance is very convenient. The sand trap at the bottom of the centrifugal filter must be flushed frequently to prevent deposited sediment from being brought into the system again. For organic matter or impurities with a specific gravity lower than water, the separation effect of the centrifugal filter is very poor. Only in a certain flow range, the centrifugal filter can exert the effect of purifying the water.
(4) Sand filter is mainly used for pre-stage filtration of organic matter in reservoirs, ponds, dams, channels, rivers and other open water sources. It uses sand as a filter medium, and the sewage enters the canister through the water inlet, and then passes through the pore interception and capture between the sand and stone to achieve the filtering purpose. The sand filter is reliable in filtration and high in cleanliness. It is most effective in treating all organic and inorganic impurities in water with sand filter in all filters, and it can provide uninterrupted water supply. As long as the organic content in the water exceeds 10 mg/L, the sand filter should be used regardless of the inorganic content.
(5) Net filter (also known as mesh filter) This is a simple and effective filtering device, which is also cheaper and is most widely used in irrigation systems at home and abroad. Its filter media is a nylon mesh or a stainless steel mesh. It is mainly used to filter dirt such as powder, sand and scale in irrigation water. It can also be used to filter irrigation water containing a small amount of organic pollutants. However, when the organic content is slightly higher, the filtration effect is very poor, especially when the pressure is high. A large amount of organic dirt can pass through the screen and enter the pipeline, causing blockage of the system and the emitter. There are many types of mesh filters. According to the installation method, it can be divided into vertical and horizontal; according to the manufacturing materials, it can be divided into plastic and metal; according to the cleaning method, it can be divided into manual cleaning and automatic cleaning; it can be divided into closed and open according to whether it is closed or not. The mesh filter consists of a main part such as a screen, a casing, and a top cover. Each part of the filter is made of pressure-resistant metal or plastic. The screen of the main filter of the system is generally made of stainless steel wire for the filter on the branch pipe and the capillary tube, and the screen mesh can also be made of nylon or copper wire.
(6) Laminated filter The filter is overlapped by a large number of very thin circular laminations and locked to form a cylindrical filter element. Each circular lamination has two faces, and a plurality of S are distributed on one side. The filter tank has a large number of concentric annular filter grooves on the other side. If the filter capacity of the laminated filter is different, the size of the S-shaped and annular filter grooves on the laminate is also different. Like the mesh filter, the filtration capacity of the laminated filter is also expressed in mesh. The filtration capacity of the filter is between 40 and 400 mesh.
Before choosing a filter device, you should first determine the following factors:
1 Find out what impurities are contained in the irrigation water.
2 Determine the flow path diameter of the selected emitter, which will be used to select the filter capacity of the filter.
3 Determine the peak flow of the irrigation system and use this flow to select the filter capacity of the filter.
The mesh size of the selected filter, ie the filter capacity of the filter, depends on the flow path diameter of the emitter. For the filter of the micro-spray system, it is necessary to filter all the impurities larger than 1/7 of the nozzle diameter; In the drip irrigation system of the dripper, the filter capacity of the filter must be such that all of the impurities larger than 1/10 of the diameter of the drip can be filtered out.