A system for cleaning biofilm from the walls of water pipelines using water hammer pressure

Abstract

The application discloses a system for cleaning biofilm on the wall of a water conveying pipeline by using water hammer pressure, which comprises an upstream water storage pool, a downstream water storage pool and a pressure main pipeline connecting the upstream water storage pool and the downstream water storage pool, and an electromagnetic flowmeter, a biofilm monitor and an electromagnetic flow regulating valve are arranged on the pressure main pipeline, wherein the electromagnetic flow regulating valve is located at the end of the pressure main pipeline and adjusts the working state according to the feedback signal of the biofilm monitor, including keeping the same valve opening degree to stably supply water from the upstream water storage pool to the downstream water storage pool, and cleaning and washing the biofilm on the inner wall of the pressure main pipeline according to the valve opening degree curve. The biofilm is flushed by the high-intensity shearing force caused by the fluctuating turbulent flow based on the water hammer effect, so that the biofilm on the wall is caused to fall off and is taken away with the water flow, the pipeline is effectively cleaned, the water quality is improved and the service life of the pipeline is prolonged.

Description

Technical Field

[0001] This invention relates to the field of biofilm treatment technology in water supply networks, and in particular to a system for cleaning biofilm from the walls of water supply pipelines using water hammer pressure. Background Technology

[0002] The water supply network and the drinking water it transports constitute a vast and complex "reactor." Standard-compliant treated water undergoes a series of physicochemical and biological reactions within this network, leading to residual chlorine decay, increased turbidity, bacterial growth, and deterioration of water quality. Common microorganisms in the water supply network include bacteria, protozoa, freshwater algae, and other microorganisms. These microorganisms attach to and grow on the water pipes, forming a biofilm. In the water supply network system, 95% of the microorganisms are concentrated in the pipe biofilm, while only 5% remain free-floating in the water.

[0003] Although water supply pipes are a nutrient-poor environment, microorganisms can still attach and grow on the pipe walls, forming biofilms. The proliferation of biofilms often leads to a series of problems such as pipe corrosion and water quality deterioration. Studies have shown that the formation of biofilms in water supply networks is a dynamic process, initially involving bacterial attachment, followed by the generation of extracellular polymeric substances (EPS). EPS It can alter the surface properties of bacteria in biofilms, providing them with physical stability against shear forces, thus promoting greater microbial adhesion and aggregation. Bacterial growth within the biofilm occurs in a layered aggregation, and the process of forming a mature biofilm can take anywhere from several months to several years. Once hydraulic conditions change and external forces exceed the biofilm's adhesive strength, the biofilm detaches from the pipe surface.

[0004] Because chemical reagents produce harmful byproducts, the current mainstream methods for cleaning biofilms attached to and growing in water supply networks are to use pipeline robots or ultraviolet disinfection. However, these methods require a lot of manpower and resources and are slow to clean. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a system that is simple in structure and has a good cleaning effect by using water hammer pressure to clean the biofilm on the wall of water supply pipelines. The system uses the high-intensity shear force generated by water hammer to physically destroy the surface of the biofilm and remove it.

[0006] Technical Solution: To achieve the above objectives, the present invention provides a system for cleaning biofilm from the walls of water supply pipelines using water hammer pressure. The system includes an upstream reservoir, a downstream reservoir, and a main pressure pipeline connecting the upstream and downstream reservoirs. An electromagnetic flow meter, a biofilm monitor, and an electromagnetic flow control valve are installed on the main pressure pipeline. The electromagnetic flow control valve is located at the end of the main pressure pipeline and adjusts its operating state based on feedback signals from the biofilm monitor. This includes maintaining the same valve opening to ensure a stable water supply from the upstream reservoir to the downstream reservoir and cleaning the biofilm from the inner wall of the main pressure pipeline according to the valve opening curve.

[0007] A pressure sensor is also installed upstream of the electromagnetic flow control valve.

[0008] The valve opening curve refers to a graph showing the change in the size of the valve opening as the valve moves from fully open to fully closed over a period of time. It is set according to the water hammer pressure required to clean the biofilm on the inner wall of the main pressure pipeline, so that the water hammer pressure generated in the main pressure pipeline is less than the maximum water pressure that the main pressure pipeline can withstand.

[0009] The control conditions for the electromagnetic flow regulating valve to operate according to the valve opening curve to clean the biofilm on the inner wall of the main pipeline are as follows:

[0010] ;

[0011] In the formula, k The flow resistance coefficient of the electromagnetic flow control valve; F(k) For the electromagnetic flow control valve opening curve; BES v The value of the biofilm electrical signal fed back by the biofilm monitor is in mV. BES max This is the maximum critical value of the electrical signal in the biomembrane.

[0012] The flow resistance coefficient of the electromagnetic flow control valve is calculated as follows:

[0013] ;

[0014] In the formula, Q The flow rate value fed back by the electromagnetic flowmeter, in meters (m³). 3 / s; g The acceleration due to gravity is m / s². 2 ; A G The cross-sectional area of ​​the electromagnetic flow control valve is expressed in meters (m²). 2 .

[0015] Among them, when BES vWhen the signal value is between 700mV and 900mV, the electromagnetic flow control valve operates according to the valve opening curve.

[0016] The method for calculating water hammer pressure is as follows:

[0017] ;

[0018] In the formula: ∇p is the water hammer pressure, in meters; K is the biofilm permeability, in meters. 2 φ is the porosity of the biofilm; u is the local velocity vector; μ is the water viscosity, in Pa·s.

[0019] The biofilm permeability K and biofilm porosity φ are obtained in real time from the biofilm monitoring instrument.

[0020] Beneficial effects: 1. This invention uses the high-intensity shear force caused by the turbulent flow formed by the water hammer effect to flush the biofilm, causing the biofilm on the pipe wall to fall off and be carried away by the water flow, effectively cleaning the pipe, improving water quality and extending the service life of the pipe.

[0021] 2. This invention can simultaneously remove other sediments and attachments in the pipeline, with high treatment efficiency, strong adaptability, and no secondary pollution, reducing the possibility of pollutants entering the water body.

[0022] 3. This invention does not require modification of existing pipelines, is simple to operate, can adapt to pipelines of different diameters, has high flexibility and mobility, and has a wide range of applications.

[0023] 4. This invention enables remote online operation to monitor and control various devices in the system. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the system structure described in this invention;

[0025] Figure 2 This is a schematic diagram of pressure oscillation within a pipeline.

[0026] Figure 3 A schematic diagram of the system structure is provided for implementation.

[0027] Figure 4 A schematic diagram of the valve opening curve of the flow control valve under different closing schemes;

[0028] Figure 5 A schematic diagram illustrating pressure oscillation within a pipeline under different shut-off schemes;

[0029] Figure 6 To implement different closure schemes, the biofilm inside the pipeline BES Schematic diagram of signal changes; Detailed Implementation

[0030] The technical solution of the present invention will be described in detail below with reference to the embodiments and accompanying drawings.

[0031] like Figure 1 As shown, the system of the present invention includes an upstream reservoir 1, a downstream reservoir 7, and a pressure main pipeline 2 connecting the upstream reservoir 1 and the downstream reservoir 7. An electromagnetic flowmeter 3, a biofilm monitor 4, a pressure sensor 5, and an electromagnetic flow regulating valve 6 are sequentially installed on the pressure main pipeline 2 from the upstream reservoir 1 to the downstream reservoir 7.

[0032] The electromagnetic flow control valve 6 is located at the end of the main pressure pipeline 2 and opens and closes according to the valve opening curve. The valve opening curve refers to the curve of valve opening and corresponding flow resistance coefficient. When the valve opening changes, the fluid flow rate changes accordingly to generate water hammer pressure of different magnitudes. During the process of water hammer generation and gradual decay, the pressure and flow rate in the main pressure pipeline 2 will undergo continuous oscillating changes. Under the influence of the friction of the main pressure pipeline 2, the water hammer wave will gradually decay until the pressure and flow rate stabilize back to a constant value. At this time, the entire system returns to a new equilibrium state.

[0033] Water hammer is a pressure wave that occurs during transient flow in pipelines. It is caused by a change in flow velocity at a certain cross-section of the pipe, resulting in a sudden increase or decrease in pressure at that point. The pressure rise caused by water hammer can sometimes be very large, potentially leading to pipe rupture; the pressure drop caused by water hammer creates a vacuum inside the pipe, which may cause the pipe to collapse and be damaged. The propagation speed of water hammer waves in typical pipelines is approximately 1000 m / s. If the liquid flow velocity inside the pipe is 1.0-1.5 m / s, the water hammer pressure caused by a sudden valve closure is approximately 1-1.5 MPa. The economical flow velocity in typical water supply networks is around 1.0 m / s, and the maximum water hammer pressure is around 0.2 MPa. During the entire transient process of water hammer, the pressure changes in all directions within the pipeline can significantly impact biofilm growth. EPS Sufficient impact force is generated. A flow velocity change of only 0.2 m / s is required to produce a water hammer pressure of 0.2 MPa, resulting in a pressure head of only 20 m. The pressure rating of the water supply pipeline should be no less than 0.6 MPa, therefore this pressure head will not damage the pipeline. Thus, during biofilm removal, the water hammer effect can be fully utilized to alter the hydraulic conditions of the water flow in the pipeline. External force can disrupt the surface structure of the biofilm, while the drastic change in water velocity can further promote the shedding of the biofilm, achieving a good cleaning effect.

[0034] The biofilm monitor 4 measures the natural electrochemical activity of the bacterial biofilm within the main pressure pipe 2, enabling early detection of biofilm growth and indicating the actual presence and extent of bacteria over a specific period. Its feedback... BES When the signal change is less than 500mV, it indicates that the pipeline is in good condition, the biofilm is growing slowly and on a small scale, and will not affect the water quality; when BES When the signal is between 500mV and 700mV, it indicates that a biofilm is growing inside the pipeline, requiring close monitoring and a decision on whether to take cleaning measures; when BES When the signal is between 700mV and 900mV, it indicates that a large amount of biofilm has appeared in the pipeline and reached a certain scale, which has begun to pollute the water quality and have a certain corrosive effect on the pipeline. The pipeline urgently needs to be cleaned.

[0035] The closing pattern of the electromagnetic flow control valve 6 is closely related to the maximum pressure during water hammer impact on the pipeline. Generally, the faster the electromagnetic flow control valve 6 closes, the greater the extreme water hammer pressure. The specific maximum water hammer pressure required in the main pressure pipeline 2 should be related to the real-time biofilm permeability fed back by the biofilm monitor 4. K and biofilm porosity φ Relatedly, when the water hammer pressure reaches 20m water head, it can achieve the effect of quickly and effectively cleaning up biofilm.

[0036] The method of this invention for calculating the water hammer pressure required to clean the biofilm on the inner wall of the main pressure pipeline 2 is based on the feedback values ​​of the electromagnetic flowmeter 3, the biofilm monitor 4, and the pressure sensor 5. The specific required water hammer pressure is calculated, and the opening of the electromagnetic flow control valve 6 is then controlled to generate the corresponding water hammer pressure. The specific control conditions are as follows:

[0037]

[0038] in:

[0039]

[0040] In the formula, k The flow resistance coefficient of electromagnetic flow control valve 6; F(k) The curve showing the relationship between the flow resistance coefficient and the opening degree of the electromagnetic flow control valve 6; BES v This is the biofilm electrical signal monitoring value fed back by biofilm monitor 4, in mV; BES max This represents the maximum critical value of the electrical signal in the biomembrane. Q The flow rate value fed back by electromagnetic flowmeter 3, in meters. 3 / s; g The acceleration due to gravity is m / s². 2 ; A GThe cross-sectional area of ​​electromagnetic flow control valve 6 is given in meters. 2 .

[0041] The biofilm is assumed to be a porous medium, and the real-time biofilm permeability is based on feedback from the biofilm monitor 4. K and biofilm porosity φ The water hammer pressure for cleaning the biofilm on the pipe wall can be calculated using the following equation:

[0042]

[0043] In the formula: ∇ p Water hammer pressure, in meters (m). K Biomembrane permeability, in meters (m). 2 ; φ The porosity of the biofilm; u This is a local velocity vector; μ The viscosity of water is expressed in Pa·s.

[0044] Among them, the water hammer pressure generated by the opening and closing of the electromagnetic flow regulating valve 6 is less than the maximum internal water pressure that the pressure main pipeline 2 can withstand; the maximum pressure generated inside the pressure main pipeline 2 H The opening and closing mechanism of the electromagnetic flow control valve 6 in the pipeline and the pressure bearing standard of the pipeline are determined.

[0045] The process for cleaning the biofilm growing on the inner wall of the main pressure pipeline 2 is as follows:

[0046] 1. Based on the feedback from biofilm monitor 4 BES The signal determines the maximum water hammer pressure required to clean the pipeline;

[0047] 2. Based on the maximum water hammer pressure, formulate a scheme for the opening and closing of the electromagnetic flow regulating valve, clarify the valve opening degree and opening and closing information, and input the information into the controller of the electromagnetic flow regulating valve 6 to control the electromagnetic flow regulating valve 6 to open and close according to the input information;

[0048] 3. Once the pressure value monitored by pressure sensor 5 returns to equilibrium, it indicates that the water hammer process has basically ended. Figure 2 As shown;

[0049] 4. Observe the feedback from the biofilm monitor. BES signal when BES If the signal value falls back to the acceptable range, it indicates that the biofilm cleaning of the inner wall of the main pressure pipeline 2 is complete.

[0050] 5. Control the electromagnetic flow regulating valve 6 to the normal water supply opening degree according to the planned valve opening pattern. After stabilization, the normal water supply state of the pipeline can be restored. Example

[0051] Pipeline layout diagram as follows Figure 3As shown, the water transmission pressure pipeline is approximately 3.2 km long, with a diameter of DN1200, and the total designed flow rate of the water transmission system is 1.2 m³ / s. 3 / s, the upstream reservoir is 6.0m high, and the downstream reservoir is 3.6m high. Negative pressure is not allowed in the pipeline during the transition process, and the maximum pressure must not exceed 0.6MPa. The calculated initial water hammer pressure for cleaning the biofilm on the pipe wall is 20.4m. The valve opening curve of the flow regulating valve used in this example is as follows: Figure 4 As shown in Table 1, the extreme values ​​of water hammer pressure are highly correlated with the valve closing strategy. The valve patterns and extreme pressure values ​​in the pipeline used in this study are illustrated in Table 1. The opening and closing pattern, such as 30s, refers to the total time taken for the valve to go from fully open to fully closed, which is 30 seconds.

[0052] Table 1 Valve Closing Patterns and Pressure Extremes

[0053] plan Opening and closing rules Initial opening Target opening Maximum pressure of pipeline minimum pressure of pipeline 1 30s 1 0 48.3 7.1 2 45s 1 0 37.9 13.8 3 60s 1 0 32.3 16.9 4 75s 1 0 29.0 16.9 5 90s 1 0 26.9 16.5

[0054] The faster the flow control valve closes, the greater the maximum pressure in the pipeline, but it remains within the pipeline's pressure-bearing standard. During the valve closing process, pressure fluctuations within the pipeline are as follows: Figure 5 As shown, when the valve is closed, pressure oscillations occur within the pipeline. The high-intensity shear force generated by these pressure fluctuations can damage the biofilm on the pipeline's inner wall. In Scheme 1, the maximum pressure is 48.3 m, the maximum oscillation amplitude is 41.1 m, and the periodic values ​​are around 20 m, which can significantly damage the biofilm on the inner wall. While other schemes have maximum pressures exceeding 20 m, the periodic oscillation values ​​are smaller, limiting their destructive effect on the biofilm. The biofilm levels monitored by the biofilm monitoring instrument under different valve closure strategies are also shown. BES Signal changes such as Figure 6 As shown. The inside of the pipe is visible. BES The signal gradually decreases as the valve closing speed increases. When a 30-second segmented closure is adopted, the signal in the pipeline... BES The signal has gradually decreased from an initial 756mV to below 500mV, indicating a significant effect in cleaning the biofilm on the inner wall of the pipe.

Claims

1. A system for cleaning biofilm from the walls of a water pipeline using water hammer pressure, comprising an upstream reservoir (1), a downstream reservoir (7), and a pressure main pipeline (2) connecting the upstream reservoir (1) and the downstream reservoir (7), characterized in that, An electromagnetic flow meter (3), a biofilm monitor (4), and an electromagnetic flow regulating valve (6) are installed on the main pressure pipeline (2). The electromagnetic flow regulating valve (6) is located at the end of the main pressure pipeline (2) and adjusts its working state according to the feedback signal from the biofilm monitor (4). This includes maintaining the same valve opening to ensure a stable water supply from the upstream reservoir (1) to the downstream reservoir (7) and cleaning the biofilm on the inner wall of the main pressure pipeline (2) according to the valve opening curve. The valve opening curve F(k) This refers to the change in the size of the valve opening during the process of the valve going from fully open to fully closed over a period of time. The setting is based on the water hammer pressure required to clean the biofilm on the inner wall of the main pressure pipeline (2), ensuring that the water hammer pressure generated in the main pressure pipeline (2) is less than the maximum water pressure that the main pressure pipeline (2) can withstand; the valve opening curve... F(k) Characterizes the valve opening degree and flow resistance coefficient k The relationship is non-linear and inversely proportional; as the valve opening increases, k The value decreases, and as the valve opening increases, k The rate of decrease in value gradually slows down; The control conditions for the electromagnetic flow regulating valve (6) to clean the biofilm on the inner wall of the main pipeline (2) according to the valve opening curve are as follows: ； In the formula, k The flow resistance coefficient of the electromagnetic flow control valve (6) is denoted as . F(k) For the electromagnetic flow control valve (6), the valve opening curve is shown. BES v The value of the biofilm electrical signal fed back by the biofilm monitor (4) is in mV; BES max This represents the maximum critical value of the electrical signal in the biomembrane. The flow resistance coefficient of the electromagnetic flow control valve (6) is calculated as follows: ； In the formula, Q The flow rate value fed back by the electromagnetic flowmeter (3), in meters. 3 / s; g The acceleration due to gravity is m / s². 2 ; A G The cross-sectional area of ​​the electromagnetic flow control valve (6) is expressed in m². 2 .

2. The system for cleaning biofilm from the walls of water pipelines using water hammer pressure according to claim 1, characterized in that, A pressure sensor (5) is also provided upstream of the electromagnetic flow control valve (6).

3. The system for cleaning biofilm from the walls of water pipelines using water hammer pressure according to claim 1, characterized in that, when BES v When the signal value is between 700mV and 900mV, the electromagnetic flow regulating valve (6) operates according to the valve opening curve.

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