RU2849615C1 - Irrigation system for wastewater utilisation - Google Patents

Abstract

FIELD: agriculture.

SUBSTANCE: irrigation system includes a storage pond connected by a supply pipeline to a wastewater source, designed as an embanked section of the irrigated area, connected by an irrigation pipeline to the irrigation network. The embankment of the storage pond is formed from soil removed from the embanked area, with a pond basin 0.3-0.5 m deep, sloping from its centre to the earth embankment. The irrigation pipeline is equipped with a pressure regulator and connected to the irrigation network, consisting of a distribution pipeline with perforated irrigation pipes, the distance between which is no more than twice the capillary water transfer value of the soil of the irrigated area, laid at a depth of 0.3-0.5 m from the soil surface on screens made of membrane film 0.3-0.5 m wide. The irrigation pipeline is equipped with an electrically operated gate valve connected to a soil moisture sensor installed in the irrigated area. A wastewater level sensor is located in the storage pond and connected to the electric drive of the gate valve installed on the supply pipeline.

EFFECT: preservation of the natural fertility of the soil in the irrigated area.

1 cl, 2 dwg

Description

The proposed invention relates to the field of agriculture and will find application in areas of insufficient moisture in the absence of fresh irrigation water.

A well-known irrigation system for the disposal of domestic wastewater includes a source of domestic wastewater, a pipeline for its discharge into a storage pond, and a pumping station connected by a pipeline to an irrigation network consisting of underground perforated pipes. (Manual VNTP 01-98 "Irrigation Systems Using Wastewater and Livestock Effluents" Ministry of Agriculture of the Russian Federation, Moscow, 1998, pp. 104-105.)

The disadvantages of this irrigation system are the need to supply water from the storage pond to the irrigation network using a pumping station and the seasonal operation mode of the irrigation network.

A system for recycling wastewater for irrigation is known, which includes a storage pond and irrigation pipelines connected to an irrigation network in the form of checks. A distinctive feature of this system is the design of the storage pond as a section of the field surface surrounded by an embankment of soil removed from the adjacent irrigated area, forming checks with the bottom below the bottom of the storage pond. This design of the system allows for the gravity-fed delivery of wastewater to the irrigated area due to the pressure created by the water layer in the storage pond. (Wastewater recycling system, Russian Federation patent No. 2815821, A01G 25/00, published March 22, 2024, bulletin No. 9). This patent has been accepted as a prototype.

A disadvantage of this system is the use of soil removed from the surface of the irrigated area to form the reservoir embankments. This requires the application of large quantities of organic and mineral fertilizers when subsequently cultivating crops in the checks formed by the removed soil. Another drawback is the seasonal operation of the irrigation network, which necessitates the use of wastewater between irrigation seasons. Furthermore, irrigation by filling the checks with wastewater on highly permeable lands poses a risk of groundwater pollution due to deep filtration of runoff, and in the presence of saline groundwater, salinization of the irrigated area.

The said disadvantages can be eliminated by an irrigation system for wastewater disposal, which includes a storage pond connected by a supply pipeline to a wastewater source, made in the form of an embanked section of an irrigated area, connected by an irrigation pipeline to an irrigation network, in which, according to the proposed invention, the storage pond shaft is formed from soil removed from the embanked area with the pond bowl being made deepened by 0.3-0.5 m with a slope from its center to the earthen shaft, and the irrigation pipeline is equipped with a pressure regulator and is connected to an irrigation network consisting of a distribution pipeline with perforated irrigation pipes, the distance between which is no more than twice the value of capillary transfer of water by the soil of the irrigated area, laid at a depth of 0.3-0.5 m from the soil surface on screens made of membrane film 0.3-0.5 m wide, while the irrigation pipeline is equipped with a valve with an electric drive connected with a soil moisture sensor installed in the irrigated area, and a wastewater level sensor is placed in the storage pond, connected to an electric drive of the valve installed on the supply pipeline.

A new technical result of using the proposed irrigation system for wastewater disposal is the preservation of the natural fertility of the irrigated soil by creating a bank of soil removed from the bottom of the pond basin. The placement of perforated tubes on membrane film screens 0.3-0.5 m wide, at a depth of 0.3-0.5 m from the soil surface at a distance no greater than twice the capillary transfer of water by the soil, and the use of a pressure regulator allow for subirrigation without deep filtration of wastewater beyond the irrigated soil layer and for its disposal throughout the frost-free season. Furthermore, the installation of a soil moisture sensor in the irrigated area and a water level sensor in the storage pond ensure real-time regulation of the wastewater flow to the irrigated area.

The essence of the proposal is explained by the drawing, where Fig. 1 shows a diagram of an irrigation system for wastewater disposal, a plan view; Fig. 2 shows a vertical section of the irrigation system for wastewater disposal along the A - A axis.

The system consists of a storage pond 2 located next to the irrigated area 1, consisting of an earthen embankment 3 and a pond bowl 4. The storage pond 2 is connected to the source of wastewater by a supply pipeline 5, on which a valve with an electric drive 7 is installed in a well 6. An irrigation pipeline 8 is used to supply water from the storage pond 2 to the area 1, on which a valve with an electric drive 10 is installed in a well 9. The pipeline 8 is led into a well 11, where a pressure regulator 12 is located. Well 11 is connected to a distribution pipeline 13, to which perforated irrigation pipes 14 are connected, laid at a depth of 0.3-0.5 m from the soil surface on screens 15 made of membrane film 0.3-0.5 m wide. The distance between the perforated pipes should not exceed twice the value Capillary transport of water by the soil. A topsoil moisture sensor 16 is installed in irrigated area 1, connected via a wireless transmitter to the electric drive of valve 10. A water level sensor 17 is installed in storage pond 2, connected via wires to the electric drive of valve 7.

We will examine the construction and subsequent operation of an irrigation system for wastewater disposal using the example of the Republic of Crimea, where the steppe region outside the irrigation zone of the North Crimean Canal faces a shortage of fresh irrigation water and the problem of wastewater disposal from populated areas. The challenge of using domestic wastewater for irrigation is the limited duration of the irrigation season, which, depending on the crop, ranges from four to six months. Wastewater is generated throughout the year. This necessitates the construction of large-capacity storage ponds to accumulate wastewater for subsequent use during the irrigation season. The construction of such storage ponds in the flat steppe terrain requires extensive excavation work and the use of a pumping station to pump wastewater from the buried storage pond into the irrigation system.

The proposed irrigation system for wastewater disposal addresses these issues. The system is being constructed at a regulated distance from a populated area with a centralized wastewater disposal and treatment system. Area 1, where the irrigation system is being constructed, is intended for growing continuous-seeded grain crops (spring wheat) and sown grasses for the production of grass meal, as part of a grain-grass crop rotation. The soil in Area 1 is medium loam. This soil is characterized by capillary water transfer of up to 1.6 meters. Snow cover in the steppe region of the republic is unstable, lasting up to 20 days with a soil freezing depth of up to 20 cm.

According to the proposal, storage pond 2 is constructed by filling an earthen embankment 3 2.5 m high with soil removed from the pond bowl 4 (excavation), with the formation of its bottom with a slope from the center to the embankment 3. Forming the bottom of the bowl with a depth of 0.3-0.5 m and a slope from the center of the bowl to the embankment ensures the release of wastewater from the pond before its periodic cleaning, carried out once every few years. An underground supply pipeline 5 is laid from the city treatment plant to storage pond 2, on which a well 6 is constructed and a valve with an electric drive 7 is installed in it. Irrigation pipeline 8 is laid from the pond bowl 4 to irrigated area 1. At the outlet of pipeline 8 from under earthen embankment 3, a well 9 is made, in which a valve 10 equipped with an electric drive is installed. At the end of pipeline 8, a well 11 is installed, in which a pressure regulator 12 is placed. On both sides of the well 11, trenches 0.4 m deep are dug, into which a distribution pipeline 13 is laid. On territory 1, perpendicular to pipeline 13, at a distance of 2.0 m, trenches 0.4 m deep and 0.3 m wide are dug. The bottom of the trenches is lined with a screen 15 made of membrane film 0.3 m wide, on which perforated irrigation pipes 14 are laid and connected to the distribution pipeline 13. The laying depth of 0.4 m exceeds the depth of soil freezing, which prevents freezing of wastewater in the pipes in winter. At the same time, the laying depth is less than the value of capillary water transfer by the soil, which ensures capillary supply of water to the surface in the root zone of the soil. A screen width of 0.3 m on medium loams prevents deep water runoff and ensures its capillary transport away from perforated tubes 14. Screen 15, constructed of membrane film, ensures, while preventing deep water runoff, gas exchange between the soil layers located below and above this screen, thus preventing gleyzation of the root zone soil. The distance between perforated tubes is 2 m, which is less than twice the capillary moisture transfer value of the soil in the area (3.2 m) and sufficient for the closure of the moistening contours of adjacent perforated tubes 14, ensuring continuous moistening of irrigated area 1. After connecting perforated tubes 14 to pipeline 13, the trenches are backfilled. On site 1, a sensor 16 for the moisture content of the upper soil layer is installed, equipped with a wireless communication device with the electric drive of the valve 10. In the storage pond 2, a sensor 17 for the level of wastewater is mounted, which is connected to the electric drive of the valve 7.

Before irrigation begins, storage pond 2 is filled with wastewater supplied by pumps from the local treatment plant through supply pipeline 5 with valve 6 open. When storage pond 2 fills to the 2-meter mark, water level sensor 17 signals the electric actuator of valve 7 to close it. Maintaining the water level in storage pond 2 at the 2-meter mark prevents aquatic vegetation from overgrowing the pond. After sowing spring wheat and when the soil moisture level drops to 75% of the maximum permissible humidity, wastewater is supplied from the storage pond 2 to the irrigated area 1. For this purpose, the pressure regulator 12 in the well 11 is installed at a level of 0.1 m from the surface of the irrigation pipes 14 and the valve 10 in the well 9 is opened. In this case, water from the storage pond 2 enters through the irrigation pipeline 8 through the well 11 into the distribution pipeline 13, and from there into the perforated pipes 14. During the process of filling the network of pipes 14, the water level in the storage pond 2 decreases, and the water level sensor 17 in the pond sends a command to the electric drive of the valve 7 to open it. A two-meter-thick layer of water in storage pond 2 ensures gravity-fed water supply to well 11, while pressure regulator 12 maintains a stable pressure of 0.1 m in tubes 14. Screen 15 prevents water from seeping beyond the root zone and ensures its capillary moistening. As water is supplied to tubes 14, capillary movement occurs both toward the soil surface and away from tubes 14. The capillary water transport value for medium loam soils is 1.6 m. Double the transport value, respectively, is 3.2 m. Therefore, the capillary moistening contours of adjacent tubes 14, spaced 2 m apart, merge, and a continuous capillary moistening zone forms within a 0.3 m-thick soil layer in the irrigated area, with the moisture content corresponding to the soil's normal water content. Since water continuously evaporates from the field surface, it moves through capillary pores not only away from tubes 14 but also toward the surface. Membrane film of screen 15, while preventing deep water runoff, maintains air permeability, preventing gley formation in the soil layer around tubes 14. Water level sensor 17, combined with pressure regulator 12, maintains a favorable water-to-air ratio for plant roots in the 0.3-meter soil layer throughout the growing season. During prolonged rainfall or heavy downpours and in the absence of surface runoff, the top 5 cm of soil may become moistened to the full capacity, filling the non-capillary pores with water. In this case, moisture sensor 16 signals the electric actuator of valve 10 to close it. When this valve is closed, the flow of wastewater to irrigated area 1 ceases. Consequently, the water level in storage pond 2 will exceed the preset mark of two meters, and level sensor 17 will signal the closure of valve 7. After precipitation ceases and the topsoil dries to the minimum water level, a signal from soil moisture sensor 16 opens valve 10, and irrigation of area 1 resumes. When the water level in storage pond 2 drops below two meters, level sensor 17 signals the opening of valve 7, and the flow of wastewater to the storage pond resumes. Water supply to storage pond 2 is stopped one week before harvest. This reduces soil moisture and minimizes soil compaction during harvesting. After harvesting, water supply to irrigated area 1 is resumed. Since capillary pores remain in the soil after harvest, wastewater evaporation continues until the topsoil freezes in winter. In winter, when the topsoil freezes, the water in the capillaries freezes, and its movement toward the surface ceases. When capillary movement ceases, the wastewater level in storage pond 2 rises, and sensor 17 signals the closure of valve 7. Soil freezing in Crimea is typically short-lived, so with the onset of a thaw, the ice in the soil capillaries melts, and water movement toward the soil surface resumes. As water consumption for evaporation from the surface of area 1 resumes, its level in pond 2 decreases, and level sensor 17 signals the opening of valve 7 and the resumption of wastewater flow into storage pond 2. In the spring, before sowing in area 1, the water supply from pond 2 is stopped by closing valve 10, and plowing is performed with soil turnover, moving the topsoil with accumulated mobile salts to the plowing depth (20 cm). After plowing, a mixture of annual grasses is sown to produce grass meal. After sowing, when the soil moisture level drops to 70% of the reference water, wastewater is supplied in the manner described above, with breaks for grass harvesting. After the end of the growing season, water is continued to flow into the perforated tubes, and it flows through the soil capillaries to the surface, where it evaporates. In the spring after plowing, grain is sown and subsequently irrigated. Thus, wastewater disposal in area 1 is carried out with short breaks for sowing and harvesting throughout the frost-free season, which allows for a reduction in the volume of storage ponds.

The proposed irrigation system for wastewater disposal preserves the natural fertility of the irrigated area and ensures gravity-fed wastewater delivery to the irrigated area. The placement of perforated tubes at intervals no greater than twice the capillary transfer rate of soil moisture onto 0.3-0.5 m wide membrane screens at a depth less than the capillary transfer rate of soil water, as well as the presence of a pressure regulator in the perforated tubes, allows for moistening the root zone of the soil via subirrigation through capillary pores without wastewater filtration beyond the irrigated soil layer and for its disposal throughout the frost-free season.

Claims (1)

An irrigation system for wastewater disposal, including a storage pond connected by a supply pipeline to a source of wastewater, made in the form of an embanked section of an irrigated area, connected by an irrigation pipeline to an irrigation network, characterized in that the embankment of the storage pond is formed from soil removed from the embanked area, with the creation of a pond bowl, deepened by 0.3-0.5 m, with a slope from its center to the earthen embankment, and the irrigation pipeline is equipped with a pressure regulator and is connected to an irrigation network consisting of a distribution pipeline with perforated irrigation pipes, the distance between which is no more than twice the value of capillary transfer of water by the soil of the irrigated area, laid at a depth of 0.3-0.5 m from the soil surface on screens made of membrane film 0.3-0.5 m wide, wherein the irrigation pipeline is equipped with a valve with an electric drive connected to The irrigated area is monitored with a soil moisture sensor, and a wastewater level sensor is placed in the storage pond, connected to the electric drive of the valve installed on the supply pipeline.