A siphon valveless filter tank and backwashing method for water treatment

Abstract

The present application belongs to the technical field of water treatment, and specifically relates to a siphon valveless filter tank for water treatment and a backwashing method. The filter tank comprises a filter tank main body, a water inlet system, a filtering system, a backwashing system, a clean water collecting system and a control valve assembly. The inside of the filter tank is provided with, from top to bottom, a clean water area, an ultra-high space, a sand washing tank, a filter material layer, a supporting layer, an air-water distributor and a water distribution area, and a vertical shaft water distribution channel is arranged in parallel on the side. The water inlet system eliminates the air entrainment phenomenon through the vertical shaft water distribution channel. The backwashing of the filter tank comprises two modes of hydraulic automatic control and program control, and both modes integrate air-water combined backwashing operation. The present application combines the advantages of homogeneous filter material deep bed filtration and hydraulic automatic control, realizes air-water combined backwashing, and efficiently removes impurities in the filter layer. The filter tank has compact structure, is easy to operate and maintain, and can expand the treatment capacity of a single tank as needed, and is suitable for water treatment scenes such as water supply treatment, sewage treatment and water purification, and is especially suitable for new construction and old plant reconstruction of medium and small water plants.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a siphon valveless filter structure and backwashing method for water treatment (including water supply treatment, sewage treatment and water purification treatment). Background Technology

[0002] In water treatment filtration processes, flow control technology directly affects the stability of effluent quality and the balance of process operation. A lack of effective flow control can easily lead to imbalances between the process influent and the total water volume of the water plant, causing sudden changes in water volume and consequently, fluctuations in water quality. Currently, mainstream filters such as siphon filters and gravity valveless filters rely on hydraulic conditions to achieve gradual control of filtration flow. V-type filters, with their combined air-water backwashing, have become the mainstream choice for medium to large-scale drinking water treatment. However, all types of filters have inherent defects in structural design and operational performance. Based on existing research and engineering practices related to filter design, operation, and modification, all three types of filters struggle to simultaneously meet requirements for treatment efficiency, backwashing effect, cost, and compatibility with applicable scenarios. Specific technical pain points and industry status are as follows:

[0003] I. Gravity-type valveless filter

[0004] Gravity-type valveless filters are widely used in small and medium-sized water treatment scenarios due to their hydraulic automatic control characteristics. Their core advantages are reflected in four aspects: First, convenient hydraulic automatic control operation eliminates the need for large gate valves and complex opening and closing control equipment. They can automatically complete the entire filtration and backwashing process based on hydraulic conditions, requiring minimal manual intervention and resulting in low management costs, thus meeting the high-efficiency operation needs of small and medium-sized water plants. Second, low construction and operating costs and a simplified structure eliminate the need for additional auxiliary equipment such as flushing pumps and elevated water tanks, resulting in low initial investment. Furthermore, operation relies on gravity, leading to low energy consumption. Third, excellent filtration stability ensures that the effluent water level is always higher than the filter bed, maintaining a positive head filtration state and preventing negative head phenomena at the source, thus guaranteeing stable effluent quality. Fourth, strong scenario adaptability allows for a certain range of influent turbidity adaptation, and the simple structure makes it easy to maintain, suitable for scenarios with limited technical management capabilities, such as rural water supply and small-scale industrial wastewater treatment.

[0005] However, from the perspective of actual engineering operation and technical research, the limitations of gravity-type valveless filters are also quite significant, and common problems have emerged in the actual operation of multiple water plants: First, the filter media is difficult to maintain. The filter media is sealed inside the enclosed tank, making it impossible to visually observe its condition during operation. When the filter media becomes caked or heavily polluted, requiring cleaning or replacement, the loading and unloading operations are cumbersome, time-consuming, and labor-intensive. Furthermore, traditional filter media are prone to design and operational deviations such as a non-uniformity coefficient K80 ≥ 2.0 and a filter layer thickness of less than 700mm, directly reducing the interception capacity. Second, the backwashing system has prominent defects. Not only is insufficient backwashing prone to occur at the four corners of the filter, but there are also widespread problems with insufficient backwashing water volume and intensity, and large fluctuations in backwashing intensity. In some water plants, the backwashing intensity is even as low as 5.2~7.8 L / (s·m). 2 (), far below 15 L / (s·m) 2 The design reference values ​​are not met, and there are frequent malfunctions such as slow siphon formation and water leakage in the siphon auxiliary pipe. In addition, traditional equipment does not have a forced backwash function and cannot cope with sudden filter media blockage. Thirdly, the inlet pipe is prone to air trapping, which interferes with the operation of the backwash siphon system, making it difficult to carry out backwashing smoothly. Structural problems such as blockage of the flushing water tank connecting pipe will also affect the backwashing process.

[0006] Furthermore, gravity-type valveless filters, due to their closed and valveless structure, cannot directly adopt the air-water combined backwashing process of V-type filters, which becomes the core technical obstacle to solving the problem of incomplete backwashing.

[0007] II. Siphon Filter

[0008] The siphon filter tank achieves automatic switching between filtration and backwashing based on the siphon principle. Its core consists of several filter cells, all sharing an inlet channel, an outlet channel, and a backwash tank, eliminating the need for complex power equipment. During the filtration stage, raw water enters each filter cell through the inlet channel. After impurities are trapped by the quartz sand and other filter layers, the water collects in the collection space below the filter plates and flows into the outlet channel through the outlet siphon pipe. During the backwashing stage, when the filter layer resistance of a certain filter cell rises to a set value and the water level reaches a threshold, a backwash siphon is formed through the siphon auxiliary pipe. The filtered water from other filter cells backwashes the filter layer of that cell. Impurities are discharged into the backwash tank through the drainage siphon pipe. When the water level in the filter cell falls below the siphon break point, air enters the pipe, breaking the siphon, and the filter cell automatically resumes filtration.

[0009] The advantages of siphon filters lie in their simplified equipment and economical operation: they do not require large valves, backwash pumps, or complex automatic control systems, relying on their own head and flow rate to complete backwashing. The pipe gallery area is small and the layout is concentrated, reducing the cost by 20%-30% compared to ordinary rapid filters of the same scale. Furthermore, the hydraulic automatic control can reduce the investment of management personnel. During operation, it can automatically and evenly adjust the filtration rate of each filter cell to adapt to water flow fluctuations, maintain positive head filtration, eliminate the risk of negative head, and the parallel operation of multiple filter cells ensures uniform effluent quality with minimal fluctuations. Moreover, there is no high-pressure equipment, resulting in high operational safety.

[0010] However, its shortcomings are also prominent and have become the core issues restricting the improvement of effluent water quality and operational stability. Existing patent research and engineering modification practices have clearly identified several technical pain points: First, the backwashing effect is unstable and the cleaning is incomplete. The backwashing intensity is greatly affected by the water output of other filter cells, and the flushing head is only 1.1~1.3 meters. Using only water for backwashing cannot remove deep stains and sticky dirt from the filter media layer. The crystals formed by calcium and magnesium ions are also difficult to be discharged. Long-term operation can easily lead to filter media caking. At the same time, there is no precise control unit for the backwashing intensity, which can easily cause filter layer bulging and local water leakage. Second, the siphon system has poor operational stability. The vacuum of the inlet siphon pipe is easily destroyed by the accumulation of air bubbles in the water, leading to water inlet interruption. It is difficult to form a vacuum for drainage siphon and failures occur frequently in low-temperature environments in winter. Long-term operation can also cause siphon problems. The problems include: 1) Siphon pressure head decay, making it difficult to establish a stable siphon; 2) Traditional siphon pipelines lack forced siphon and forced disruption functions, and backwash start / stop control is inflexible; 3) Limited single-pool area, with low-resistance water distribution systems limiting filter grid area to avoid reduced water distribution uniformity; 4) Poor environmental adaptability and maintenance convenience, as the siphon system is sensitive to water temperature changes, easily leading to siphon disruption and startup difficulties at low or fluctuating water levels; 5) Poor compatibility between filter media and water distribution system, as the original filter media is heterogeneous with low interception capacity; 6) Filter plates and filter heads do not consider air-water backwashing requirements, easily leading to uneven air distribution and dead water zones.

[0011] Meanwhile, because the bottom water distribution channel of the siphon filter is not sealed, it is difficult to directly achieve air-water combined backwashing, which makes it difficult to fundamentally solve the problem of sludge residue in the filtration zone, becoming the core technical difficulty in its upgrading and transformation.

[0012] III. V-shaped filter

[0013] V-type filters are widely used in medium and large-scale drinking water treatment scenarios due to their excellent effluent quality and efficient backwashing performance. Their core advantages include: First, high filtration efficiency and excellent effluent quality. They utilize homogeneous coarse-grained filter media with a thickness of 0.95-1.5 meters, ensuring uniform particle size distribution and avoiding stratification issues associated with graded filter media. This results in strong dirt-holding capacity, a filtration rate of 7-15 m / h, a long filtration cycle, and stable effluent turbidity control. Second, effective backwashing with low energy consumption. The combined air-water backwashing process, coupled with V / U-shaped tank surface cleaning, is performed in four stages: air flushing, air-water flushing, water flushing, and surface cleaning. The filter media only slightly expands, minimizing loss and significantly reducing water and electricity consumption. Third, high automation and stable operation. Backwashing is automatically triggered by water level or differential pressure signals. The standardized operation process and strong resistance to shock loads make them suitable for large and medium-sized water plants operating on a large scale. Fourth, high filter media utilization. The overall dirt-holding capacity of the filter layer is balanced, extending the filter media's service life.

[0014] The main drawbacks of V-type filters are: First, high initial investment and operating costs, requiring specialized equipment such as blowers, long-handled filter heads, and large-diameter solenoid valves, and strict construction precision requirements; second, stringent operation and management requirements, with multiple backwashing processes and high parameter control precision, necessitating professional technicians for operation and maintenance, otherwise filter media caking and fluctuations in effluent water quality may occur; third, large footprint and complex tank structure, making them unsuitable for the renovation of old water plants with limited space, and the civil engineering costs of new construction projects are relatively high; fourth, narrow application scenarios, with high costs and high operation and maintenance requirements creating significant barriers to application for small and medium-sized water plants in towns or water plants with limited renovation budgets.

[0015] IV. Overall Pain Points of Existing Technologies and Industry Needs

[0016] A comprehensive analysis of the above three types of filters and existing technological research and engineering practices reveals that the core advantages of gravity-type valveless filters and siphon filters are automatic hydraulic control, simple operation and maintenance, low cost, and the ability to maintain positive head filtration, preventing water quality deterioration. They are suitable for small and medium-sized water plants and rural water supply systems with limited technical management capabilities. However, both suffer from the common problem of limited backwashing effectiveness—the backwashing time is determined by the water volume in the tank, making it impossible to flexibly adjust the backwashing time. This results in incomplete cleaning of deep impurities in the filter layer, and long-term operation can easily lead to filter media caking. Furthermore, due to their structural limitations, neither can directly implement the air-water combined backwashing process of V-type filters, making it difficult to solve the problem of sludge residue in the filtration zone. At the same time, both have many technical defects in terms of siphon system stability, filter media management, and operational flexibility. In actual water plant operation, common problems such as insufficient backwashing intensity, siphon failure, and fluctuations in effluent water quality have already occurred. Existing renovation solutions either have high renovation costs, are limited by site and tank structure, or cannot fundamentally solve the core pain points.

[0017] Although V-type filters can achieve efficient backwashing through air-water combined backwashing to ensure effluent quality and have become an important reference direction for the upgrading and renovation of filters, their complex control system, high infrastructure and operating costs, and strict requirements for operation and maintenance technology have significantly limited their application in small and medium-sized water plants, rural water supply scenarios, and the renovation of old water plants, making it impossible to balance cost and scenario adaptability.

[0018] While existing technologies have proposed low-cost upgrades to V-type filters for siphon filters and have developed technologies such as siphon system optimization and water distribution system upgrades for gravity valveless filters, a filter device and corresponding backwashing method that combines the advantages of hydraulic automatic control of gravity valveless filters and siphon filters with the high efficiency of air-water combined backwashing of V-type filters, while also being reasonably priced, easy to operate and maintain, and adaptable to different scale water treatment scenarios (including small and medium-sized water plants, rural water supply, and renovation of old water plants) has not yet been developed.

[0019] Based on this, the development of a siphon valveless filter process device and its backwashing method that integrates the advantages of various filter beds, overcomes existing defects, and organically combines hydraulic automatic control with air-water combined backwashing is urgently needed in the water treatment field. This also aligns with the current industry development trend of upgrading water plants, energy conservation and consumption reduction, and integrated urban and rural water supply. Summary of the Invention

[0020] The purpose of this invention is to provide a siphon valveless filter structure and backwashing method that integrates the core characteristics of V-type filter, gravity valveless filter and siphon filter. It has the advantages of hydraulic automatic control, the high efficiency of air-water combined backwashing, moderate cost, and simple operation and maintenance. It can be adapted to water treatment scenarios of different scales (including water supply treatment, sewage treatment and water purification treatment).

[0021] The siphon valveless filter proposed in this invention has the following structure: Figure 1 and Figure 2 As shown, the specific structure includes the filter body, inlet system, filtration system, backwashing system, clean water collection system, and control valve assembly, wherein:

[0022] The filter body is a rectangular or circular pool, and inside it is arranged from top to bottom as follows: clear water zone (12), installation high space (5), sand washing tank (6), filter media layer (7), support layer (8), air-water distributor (9), and water distribution zone (10); a vertical well water distribution channel (3) is arranged parallel to one side of the filter body; the clear water zone (12) and the water distribution zone (10) of the filter body are interconnected by a connecting pipe (11).

[0023] The water inlet system consists of an inlet (1) and an inlet siphon (2). Raw water enters the filter tank through the inlet (1) and flows into the vertical shaft distribution channel (3) through the inlet siphon (2). The diameter of the inlet siphon (2) is determined according to the design flow rate. Generally, the flow velocity in the pipe is controlled at 0.6-1.0 m / s. The vertical shaft distribution channel (3) is a rectangular cross-section channel used to eliminate the air entrainment phenomenon in the water inlet. The channel height is not lower than the siphon outlet of the inlet siphon (2). Several drainage and venting ports (16) are provided on the lower part of its side wall. The drainage and venting ports (16) are evenly distributed and connect the vertical shaft distribution channel (3) with the installation high space (5) of the filter tank body. A valve F1 is installed on the inlet siphon (2) to control the start and stop of the inlet siphon.

[0024] The filtration system includes a filter media layer (7), a support layer (8), an air-water distributor (9), and a water distribution zone (10). The filter media layer (7) uses deep-bed homogeneous filter media. Generally, the filter media particle size is 0.8-1.3 mm, the filter layer thickness H is 900-1100 mm (preferably 1000 mm), the non-uniformity coefficient K80=1.2-1.4, and the water quality parameter L / d≥1100 (including the water distribution layer). Compared with the traditional gravity valveless filter, it has a stronger dirt-holding capacity and can avoid surface interception. The support layer (8) is located below the filter media layer (7) and uses graded pebbles to support the filter media layer and prevent filter media loss. Generally, there are three layers of pebbles. The particle size of the pebbles in the three layers is 2-4 mm, 4-8 mm, and 8-16 mm from top to bottom, and the thickness of each layer is 90-110 mm. (Preferred size 100mm); The air-water distributor (9) is laid horizontally below the support layer (8) and consists of several perforated branch pipes evenly arranged to ensure that air and backwash water are evenly distributed to the filter media layer (7); Generally, the diameter of the branch pipe is 3-8mm and the spacing between adjacent branch pipes is 150-300mm; The water distribution area (10) is the water collection space at the bottom of the filter body, used to collect the filtered water and guide it to the connecting pipe (11).

[0025] The backwashing system includes a backwashing siphon pipe (4), a backwashing air pump (15), an outlet pipe (17), a siphon breaking pipe (18), and valves F2, F4, and F5 connected to the backwashing siphon pipe (4). One end of the backwashing siphon pipe (4) is connected to the bottom of the vertical shaft water distribution channel (3), and the other end overflows and is connected to the outlet pipe (17). The bottom elevation of the U-shaped siphon pipe is lower than the bottom elevation of the U-shaped inlet siphon pipe (2) (generally 0.3-0.5m lower) to ensure that an effective siphon head is formed during backwashing. Valves F2, F4, and F5 are installed on the backwashing siphon pipe (4) in sequence. Valve F2 is used to break the backwashing siphon, valve F4 is connected to the air extraction system and is used to forcibly trigger the backwashing siphon, and valve F5 mainly controls the opening and closing of the backwash breaking pipe (18). The backwash air pump (15) is a Roots blower or a centrifugal blower. Its outlet is connected to the main pipe of the air-water distributor (9) through a pipeline. The air volume of the blower is determined according to the backwash intensity and is used to introduce air into the filter layer (7) for air washing. The diameter of the water outlet pipe (17) is matched with the flow rate of the backwash siphon pipe (4) and the end is connected to the drainage system or sludge treatment system.

[0026] The clear water collection system consists of a clear water zone (12), an outlet siphon (13), and an outlet channel (14). The clear water zone (12) is an independent water storage space, the volume of which is determined according to the backwash water consumption of a single filter cell, and its top is open to the atmosphere. One end of the outlet siphon (13) is connected to the bottom of the clear water zone (12), and the other end is connected to the outlet channel (14). Generally, the flow velocity in the siphon (13) is controlled at 0.8-1.2 m / s. A valve F3 is installed on the outlet siphon (13) to adjust the outlet flow rate and the amount of backwash water replenishment. The outlet channel (14) is an open channel used to collect the water from each filter cell and transport it to the subsequent clear water reservoir. At the same time, it forms a water replenishment loop with the clear water zone (12) through pipelines to ensure sufficient backwash water volume.

[0027] The control valve group includes valves F1, F2, F3, F4 and F5, all of which are electric or pneumatic valves and can achieve automatic control. Among them, valve F1 controls the start and stop of the inlet siphon, valve F2 controls the start and stop of the backwash siphon, valve F3 adjusts the outlet flow rate and the backwash replenishment water volume, valve F4 cooperates with the air extraction system to achieve forced backwash triggering, and valve F5 mainly controls the opening and closing of the backwash damage pipe (18).

[0028] Based on the above-mentioned siphon valveless filter structure, the present invention also provides a corresponding backwashing method, including two control modes: hydraulic automatic control and program control. Both modes include a combined air-water backwashing step, as detailed below:

[0029] (a) Hydraulic self-control method, the specific steps are as follows:

[0030] 1. Filtration stage: Raw water enters the inlet siphon pipe (2) through the inlet (1), and the inlet flow rate is controlled at 0.6-1.0 m / s. Under the action of siphon, the water flows into the vertical well distribution channel (3). After eliminating the air, it flows smoothly into the installation high space (5) of the filter body through the drainage and exhaust port (16). From top to bottom, it passes through the sand washing tank (6), the filter media layer (7), and the support layer (8). Impurities in the water are intercepted by the filter media layer (7). The purified water is collected in the distribution area (10) through the air-water distributor (9), and then enters the clear water area (12) through the connecting pipe (11). Finally, it flows into the outlet channel (14) through the outlet siphon pipe (13), and the flow rate in the outlet siphon pipe (13) is controlled at 0.8-1.2 m / s. Finally, it is transported to the subsequent treatment unit or the clear water reservoir.

[0031] 2. Backwash triggering: As the filtration process continues, the impurities trapped by the filter media layer (7) gradually increase, and the filtration resistance continues to increase, causing the water level in the vertical well water distribution channel (3) to rise continuously. When the water level rises to the throat position of the backwash siphon pipe (4), a siphon effect is formed in the backwash siphon pipe (4) under the action of the siphon auxiliary pipe system. At this time, the control system automatically opens valve F1 to introduce air into the inlet siphon pipe (2), destroying the inlet siphon. The inlet siphon pipe (2) stops water intake, avoiding water waste during the backwash process.

[0032] 3. Water backwashing: After the backwashing siphon (4) forms a siphon, it begins to pump water from the vertical shaft distribution channel (3), causing the water level in the channel to drop rapidly to below the bottom of the clear water zone (12). At this time, the purified water in the clear water zone (12) flows back into the distribution zone (10) through the connecting pipe (11) under the action of the water level difference. It then evenly washes the filter media layer (7) upward through the air-water distributor (9). The filter media particles are suspended under the action of the water flow, and they collide and scrub each other, washing away the impurities attached to the surface of the filter media. The backwashing wastewater carries impurities upward and flows into the vertical shaft distribution channel (3) after being collected by the sand washing tank (6). It is then discharged from the pool body through the backwashing siphon (4) and the outlet pipe (17). If the backwashing water volume of a single filter cell is insufficient, the water supply circuit of the outlet siphon (13) can be opened by adjusting valve F3 to supplement the clear water zone (12) with part of the outlet water in the outlet channel (14), ensuring that the backwashing water volume meets the requirements. The backwashing intensity is controlled at 5-15 L / m²·s, and the backwashing time is generally designed to be 4-6 min (e.g., 5 min). This parameter can ensure that sludge is washed away while retaining the filter membrane on the sand surface.

[0033] 4. Combined air-water backwashing: When the filter is in the backwashing cycle, the backwashing air pump (15) is automatically started 1 minute after the water backwashing starts. Air is evenly introduced into the filter media layer (7) through the branch pipe holes of the air-water distributor (9) for air backwashing; the air backwashing intensity is controlled at 5-15 L / m. 2•s, the air washing time is 1-5min, which can be flexibly adjusted according to the cleanliness of the filter material; air forms tiny bubbles in the filter material layer (7), and generates a stirring effect during the rising process, further enhancing the scrubbing effect between filter material particles and improving the impurity removal rate; air gathers in the installation high space (5) of the filter pool, and is discharged from the pool body through the vertical well water distribution channel (3) via the drainage and exhaust port (16), and the backwash wastewater is still discharged according to the above water backwash path.

[0034] 5. Backwash termination: When the backwash water level in the clear water zone (12) drops to the level of the siphon destruction pipe (18), air enters the backwash siphon pipe (4) and destroys the siphon effect, the backwash terminates, and the filter resumes the filtration stage.

[0035] (ii) Program control method, the specific steps are as follows:

[0036] 1. Filtration stage: The filtration stage is exactly the same as that of the hydraulic automatic control system.

[0037] 2. Backwash trigger: The turbidity of the filter effluent is monitored in real time by an online turbidity monitor. When the effluent turbidity rises to the set value (0.5-0.8 NTU, for example 0.8 NTU), the control system issues a command to open valve F1 to introduce air, so that the inlet siphon pipe (2) stops siphoning water in; at the same time, valve F4 is opened to start the air extraction system to extract the air in the backwash siphon pipe (4) and quickly form a siphon effect.

[0038] 3. Water backwashing: The water backwashing procedure is the same as that of the hydraulic automatic control method, and the backwashing intensity and initial duration are executed according to the preset parameters.

[0039] 4. Combined air-water backwashing: The steps are the same as those of the hydraulically controlled combined air-water backwashing, but the air washing intensity and time are automatically adjusted according to the fouling of the filter media.

[0040] 5. Backwash termination: Valve F2 can be triggered to open by time control (e.g., after 5 minutes of backwashing) or turbidity control (when the turbidity of the backwash effluent is lower than a certain set value of 3.0-8.0 NTU), thereby disrupting the siphon effect of the backwash siphon pipe (4), and then the relevant valves and backwash air pump (15) are closed, and the filter resumes filtration.

[0041] In addition, the present invention can control the amount of water replenished by the effluent siphon pipe (13) by adjusting valve F3 and control the backwashing time by adjusting valve F2, so as to achieve precise control of backwashing intensity and duration, thereby automatically selecting the backwashing method (water backwashing or air-water combined backwashing) according to the effluent water quality and filter media cleanliness of the filter bed, and achieving the optimal filter bed operation efficiency.

[0042] The main technical features and performance advantages of this invention are as follows:

[0043] 1. Integrating the core advantages of gravity valveless filters, siphon filters, and V-type filters, the effluent water quality is stable: It adopts the homogeneous filter media deep bed filtration technology of V-type filters, with a filter media layer thickness of up to 1000mm, strong dirt holding capacity, avoids surface interception filtration, and the effluent turbidity can be stably controlled below 0.5NTU; at the same time, it retains the hydraulic automatic control characteristics of gravity valveless filters and siphon filters, without the need for complex power equipment, and is easy to operate and maintain, overcoming the defects of high cost and complex management of V-type filters.

[0044] 2. Optimized water inlet structure and improved operational stability: The water inlet method adopts a vertical shaft distribution channel, eliminating the umbrella-shaped hood structure of traditional gravity-type valveless filters. The presence of vents eliminates air trapping during inlet operation, ensuring uniform water intake. During air-water backwashing, gas accumulates in the extra-high space of the filter installation and is discharged through the vertical shaft distribution channel via the drainage and vents, achieving air backwashing of the filter. Backwash water enters the vertical shaft distribution channel through the sand washing tank and drainage and vents, and is discharged from the filter via the backwash siphon pipe. This air-water backwashing effectively removes deep impurities from the filter layer, prevents filter media caking, and extends the filter media's service life.

[0045] 3. The backwashing time can be flexibly adjusted. If the backwashing water volume of a single filter cell is insufficient, the water supply circuit of the outlet siphon pipe (13) can be opened by adjusting valve F3, and part of the outlet water in the outlet channel (14) can be siphoned to the clear water area (12) to ensure that the backwashing water volume meets the requirements. This is beneficial for the water plant to adjust the backwashing time cycle and backwashing time according to the filtration conditions of the filter cell.

[0046] 4. This type of filter has a wide range of applications and is economical in cost: The device has a compact structure, does not require backwash water pumps or large valves for control, and can operate automatically using its own hydraulic conditions. It is easy to control and maintain, and is suitable for various scenarios such as the construction of small and medium-sized water plants and the renovation of old water plants. Compared with V-type filters, it reduces the initial investment by more than 20% because it does not use large valves and complex PLC control. The operation and control are simple, and the single-pool treatment capacity can be expanded according to demand, breaking through the problem of limited single-pool area of ​​traditional valveless filters. Attached Figure Description

[0047] Figure 1 This is a schematic cross-sectional view of the siphon valveless filter of the present invention.

[0048] Figure 2 This is a schematic cross-sectional view of a siphon valveless filter (AA).

[0049] Numbering in the diagram: 1-Inlet, 2-Inlet siphon pipe, 3-Vertical shaft water distribution channel, 4-Backwash siphon pipe, 5-Installation high space, 6-Sand washing tank, 7-Filter media layer, 8-Support layer, 9-Air-water distributor, 10-Water distribution area, 11-Connecting pipe, 12-Clear water area, 13-Outlet siphon pipe, 14-Outlet channel, 15-Backwash air pump, 16-Exhaust port (inlet hole), 17-Backwash outlet pipe, 18-Siphon breaking pipe, F1, F2, F3, F4, F5-Valve (where valve F4 is connected to the air extraction system). Detailed Implementation

[0050] Example 1: The siphon valveless filter of the present invention was used in the new expansion project of a slightly polluted water plant. The original process of the water plant was a 125-ton / hour hydraulic circulation clarifier connected in series with a gravity valveless filter. The influent turbidity was 10-50 NTU, and the effluent turbidity of the clarifier was 3-5 NTU. The original gravity valveless filter had a filtration rate of 7 m / h, a backwash time of 5 min, and an intensity of 15 L / m. 2 After six months of operation, the turbidity of the effluent exceeds 1.0 NTU. To maintain the effluent turbidity below 1.0 NTU, the treatment capacity needs to be reduced to 65-70 tons / hour.

[0051] The expansion project utilizes the siphon valveless filter of this invention, with a designed treatment capacity of 125 tons / hour, a filtration rate of 7 m / h, a backwash time of 5 min, and a combined air-water backwashing method. The water backwash intensity is 10 L / m²·s, and the air backwash intensity is 5 L / m²·s. 2 After 1.5 years of operation, the turbidity of the filter effluent remained stable below 0.5 NTU, the water treatment capacity remained at the design scale, the backwash water consumption was only 50% of the original process, and the filter media did not show any caking, thus extending the service life of the filter.

[0052] Example 2: The siphon valveless filter of the present invention was used in a technical renovation project of a water plant. The original process of the water plant consisted of 500 tons / hour gravity valveless filters connected in series, with an influent turbidity of 5~30 NTU and an effluent turbidity of 3~5 NTU from the sedimentation tank. The original filter rate was 7 m / h, the backwash time was 5 min, and the intensity was 15 L / m. 2 After three years of operation, the turbidity of the effluent exceeded 1.0 NTU, the treatment capacity dropped to 80 tons / hour, and the filter media became severely clogged and needed to be replaced.

[0053] The siphon valveless filter of this invention was used for modification, with a designed treatment capacity of 500 tons / hour, a filtration rate of 7 m / h, a backwashing time of 5 min, and a combined air-water backwashing method with a water backwashing intensity of 10 L / m. 2 ·s, backwash intensity is 5L / m 2After five years of operation following the modification, the turbidity of the filter effluent has consistently remained below 0.5 NTU, the treated water volume has been stable and up to standard, the backwashing effect is excellent, the filter media remains in excellent condition and does not require replacement, significantly reducing operating and maintenance costs.

Claims

1. A siphon valveless filter for water treatment, characterized in that, The specific structure includes the filter body, inlet system, filtration system, backwashing system, clean water collection system, and control valve assembly, among which: The filter body is a rectangular or circular pool, and its interior is arranged from top to bottom as follows: clear water zone (12), installation high space (5), sand washing tank (6), filter media layer (7), support layer (8), air-water distributor (9), and water distribution zone (10); a vertical well water distribution channel (3) is arranged parallel to one side of the filter body; the clear water zone (12) and the water distribution zone (10) are interconnected by a connecting pipe (11); The water inlet system consists of an inlet (1) and an inlet siphon (2). Raw water enters the filter tank through the inlet (1) and flows into the vertical shaft distribution channel (3) through the inlet siphon (2). The diameter of the inlet siphon (2) is determined according to the design flow rate. The vertical shaft distribution channel (3) is a rectangular cross-section channel used to eliminate the air entrainment phenomenon in the water. Its height is not lower than the siphon outlet of the inlet siphon (2). Several drainage and venting ports (16) are provided on the lower part of its side wall. The drainage and venting ports (16) are evenly distributed and connect the vertical shaft distribution channel (3) with the installation high space (5) of the filter tank body. The filtration system includes a filter media layer (7), a support layer (8), an air-water distributor (9), and a water distribution zone (10). The filter media layer (7) uses deep-bed homogeneous filter media. The support layer (8) is located below the filter media layer (7) and uses graded pebbles to support the filter media layer (7) and prevent filter media loss. The air-water distributor (9) is laid horizontally below the support layer (8) and consists of several perforated branch pipes evenly arranged to ensure that air and backwash water are evenly distributed to the filter media layer (7). The water distribution zone (10) is the water collection space at the bottom of the filter body, used to collect the filtered water and guide it to the connecting pipe (11). The backwashing system includes a backwashing siphon (4), a backwashing air pump (15), an outlet pipe (17), and a siphon breaking pipe (18). One end of the backwashing siphon (4) is connected to the bottom of the vertical shaft water distribution channel (3), and the other end overflows and is connected to the outlet pipe (17). Its throat elevation is lower than that of the inlet siphon (2) to ensure that an effective siphon head is formed during backwashing. The backwashing air pump (15) is a Roots blower or a centrifugal blower. Its air outlet is connected to the main pipe of the air-water distributor (9) through a pipeline. The blower air volume is determined according to the backwashing intensity and is used to introduce air into the filter layer (7) for air washing. The diameter of the outlet pipe (17) is matched with the flow rate of the backwashing siphon (4), and the end is connected to the drainage system or sludge treatment system. The clear water collection system includes a clear water zone (12), an outlet siphon (13), and an outlet channel (14). The clear water zone (12) is an independent water storage space, the volume of which is determined according to the backwash water consumption of a single filter cell, and its top is open to the atmosphere. The outlet siphon (13) connects the clear water zone (12) and the outlet channel (14). The outlet channel (14) is an open channel used to collect the effluent from each filter cell and transport it to the subsequent clear water reservoir.

2. The siphon valveless filter according to claim 1, characterized in that, In the filtration system, the filter media layer (7) adopts deep bed homogeneous filter media; the filter media particle size is 0.8-1.3mm, the filter layer thickness H is 900-1100mm, the non-uniformity coefficient K80=1.2-1.4, and the water quality parameter L / d≥1100; the support layer (8) has three layers of pebbles, and the particle size of the pebbles in the three layers is 2-4mm, 4-8mm, and 8-16mm from top to bottom, and the thickness of each layer is 90-110mm; the branch pipe aperture is 3-8mm, and the spacing between adjacent branch pipes is 150-300mm.

3. The water treatment method based on the siphon valveless filter according to claim 1, characterized in that, This includes water supply treatment, wastewater treatment, and water purification; specifically, it is divided into two modes: hydraulic automatic control and program control, both of which include air-water combined backwashing operation, as detailed below: (a) Hydraulic self-control method, the specific steps are as follows: (1) Filtration stage: Raw water enters the inlet siphon pipe (2) through the inlet (1) and the inlet flow rate is controlled to be 0.6-1.0m / s; under the action of siphon, the water flows into the vertical well distribution channel (3), and after eliminating the air, it flows smoothly into the installation high space (5) of the filter body through the drainage and exhaust port (16). From top to bottom, it passes through the sand washing tank (6), the filter media layer (7), and the support layer (8). Impurities in the water are intercepted by the filter media layer (7). The purified water is collected in the distribution area (10) through the air-water distributor (9), and then enters the clear water area (12) through the connecting pipe (11). Finally, it flows into the outlet channel (14) through the outlet siphon pipe (13) and the flow rate in the outlet siphon pipe (13) is controlled to be 0.8-1.2m / s. (2) Backwash triggering: As the filtration process continues, the impurities trapped by the filter media layer (7) gradually increase, and the filtration resistance continues to increase, causing the water level in the vertical well distribution channel (3) to rise continuously. When the water level rises to the throat position of the backwash siphon pipe (4), a siphon effect is formed in the backwash siphon pipe (4) under the action of the siphon auxiliary pipe system. At this time, the control system automatically opens valve F1 to introduce air into the inlet siphon pipe (2), destroying the inlet siphon. The inlet siphon pipe (2) stops water intake, avoiding water waste during the backwash process. (3) Water backwashing: After the backwashing siphon (4) forms a siphon, it begins to pump water from the vertical well distribution channel (3), causing the water level in the channel to drop rapidly to below the bottom of the clear water zone (12); at this time, the purified water in the clear water zone (12) flows back into the distribution zone (10) through the connecting pipe (11) under the action of the water level difference, and evenly washes the filter media layer (7) upward through the air-water distributor (9). The filter media particles are suspended under the action of water flow, and collide and scrub each other, and the impurities attached to the surface of the filter media are washed off; backwashing wastewater The impurities are carried upwards and collected in the sand washing tank (6). After being collected, they flow into the vertical shaft water distribution channel (3) through the drainage and exhaust port (16), and then are discharged from the tank body through the backwash siphon pipe (4) and the outlet pipe (17). If the backwash water volume of a single filter cell is insufficient, the outlet siphon pipe (13) is opened by adjusting valve F3 to replenish water and the clean water in the outlet channel (14) is siphoned to replenish the clean water area (12) to ensure that the backwash water volume meets the requirements. The backwash intensity and time are controlled to ensure that the sludge is washed away and the filter membrane on the sand surface is retained. (4) Air-water combined backwashing: When the filter is in the backwashing cycle, the backwashing air pump (15) is started 1 minute after the water backwashing starts. Air is evenly introduced into the filter media layer (7) through the branch pipe hole of the air-water distributor (9) for air backwashing. The air backwashing intensity and air washing time are controlled according to the cleanliness of the filter media. The air forms tiny bubbles in the filter media layer (7) and generates a stirring effect during the rising process, which further enhances the scrubbing effect between filter media particles and improves the impurity removal rate. The backwashing air is gathered in the installation high space (5) of the filter body and discharged from the pool body through the vertical shaft water distribution channel (3) through the drainage and exhaust port (16). The backwashing water is collected in the sand washing tank (6) and then flows into the vertical shaft water distribution channel (3) through the drainage and exhaust port (16), and then discharged from the pool body through the backwashing siphon (4) and the water outlet pipe (17). (5) Backwashing termination: After the filter is cleaned, open valve F2. Air enters the backwashing siphon pipe (4) to destroy the siphon effect, and the backwashing is terminated. The filter resumes the filtration stage. (ii) Program control method, the specific steps are as follows: (1) Filtration stage: Same as the filtration stage of the hydraulic automatic control method; (2) Backwash trigger: The turbidity of the filter water is monitored in real time by an online turbidity monitor. When the turbidity of the water rises to the set value, the control system issues a command to open valve F1 to introduce air, so that the inlet siphon pipe (2) stops siphoning water inlet; at the same time, valve F4 is opened to start the air extraction system to extract the air in the backwash siphon pipe (4) and quickly form a siphon effect. (3) Water backwashing: The water backwashing steps are the same as those of the hydraulic automatic control mode, and the backwashing intensity and initial duration are executed according to the preset parameters; (4) Combined air-water backwashing: The steps are the same as those of the combined air-water backwashing in the hydraulic automatic control mode, and the air washing intensity and time are automatically adjusted according to the filter media fouling. (5) Backwash termination: Valve F2 is triggered to open by time control or turbidity control, which disrupts the siphon effect of the backwash siphon pipe (4). Then, the relevant valves and backwash air pump (15) are closed, and the filter resumes filtration.

Images