CN115231667A

CN115231667A - Method for determining optimal system magnetic cement ratio and magnetic coagulation water treatment process

Info

Publication number: CN115231667A
Application number: CN202210830156.7A
Authority: CN
Inventors: 陈立; 吉青青; 唐珍建; 任成全
Original assignee: CSCEC Scimee Sci and Tech Co Ltd
Current assignee: CSCEC Scimee Sci and Tech Co Ltd
Priority date: 2022-07-15
Filing date: 2022-07-15
Publication date: 2022-10-25
Anticipated expiration: 2042-07-15
Also published as: CN115231667B

Abstract

The invention relates to a method for determining the optimal system magnetic-mud ratio and a magnetic coagulation water treatment process, wherein the method comprises the following steps of S2, respectively taking quantitative slurry out of a mixing and stirring tank to perform a sedimentation test under the conditions of solid content of the same system and different magnetic-mud ratios N, respectively calculating sedimentation speeds V corresponding to the different magnetic-mud ratios N, and obtaining a plurality of groups of measurement data by taking the magnetic-mud ratio N as a horizontal coordinate and taking the sedimentation speed V corresponding to the magnetic-mud ratio N as a vertical coordinate; s3, marking each group of measurement data in a plane rectangular coordinate system, and obtaining an N-V fitting curve through data fitting; s4, obtaining the optimal system magnetic mud ratio N according to the N-V fitting curve ₀ (ii) a The method can determine the magnetic coagulation water treatment systemThe optimal system magnetic-mud ratio ensures that the magnetic coagulation water treatment system has higher sedimentation efficiency and the best economical efficiency when running at the optimal system magnetic-mud ratio.

Description

Method for determining optimal system magnetic cement ratio and magnetic coagulation water treatment process

Technical Field

The invention relates to the technical field of magnetic coagulation water treatment, in particular to a method for determining an optimal system magnetic cement ratio and a magnetic coagulation water treatment process.

Background

As an advanced water purification technology, the magnetic coagulation water treatment technology has the characteristics of simple process, small occupied area of equipment, large treatment capacity, strong impact load resistance, low operation cost, long service life of the equipment, stable effluent of 1 grade A or higher standard and the like, is receiving wide attention in the industry day by day, and is increasingly applied to the fields of sewage treatment plant upgrading and reconstruction, advanced wastewater dephosphorization, heavy metal wastewater treatment, black foul river treatment and the like.

The existing magnetic coagulation water treatment process is usually implemented in a magnetic coagulation water treatment system, and the magnetic coagulation water treatment usually comprises three links of magnetic medium coagulation stirring, magnetic medium precipitation and magnetic medium recovery, wherein the magnetic medium coagulation stirring link refers to a process of adding a medicament and a magnetic medium (or called magnetic particles) to enable colloidal particles and micro suspended matters in sewage to be aggregated so as to form a floc (or called floc) with higher density and stronger strength for subsequent quick precipitation; it can be decomposed into two stages of coagulation and flocculation. The magnetic medium precipitation link is used for separating suspended matters such as floccules, sludge and the like in the sewage in a gravity precipitation mode, so that the solid-liquid rapid separation is realized, the sewage is purified, and the aim of purifying the sewage is fulfilled. And in the separated magnetic mud, a part of the magnetic mud can flow back to the magnetic medium coagulation stirring link to realize sludge backflow, and the rest of the sludge can enter the magnetic medium recovery link which is mainly used for recovering the magnetic medium in the magnetic mud and putting the recovered magnetic medium into the magnetic medium coagulation stirring link as required, so that the magnetic medium can be recycled, and the economic efficiency is improved.

The greatest difference between the magnetic coagulation water treatment process and the traditional coagulation precipitation process is as follows: the traditional coagulating sedimentation process does not need to add a magnetic medium into the sewage; the magnetic coagulation water treatment process is a magnetized precipitation water treatment process, and magnetic particles (namely magnetic media) are required to be continuously added into sewage in the operation process, and medicaments with different doses are required to be added into the sewage according to the adding amount of the magnetic media. The magnetic-sludge ratio refers to the ratio of a magnetic medium to sludge in a magnetic coagulation water treatment system, and in the process of a magnetic coagulation water treatment process, the magnetic-sludge ratio not only affects the sedimentation speed of the sludge in a magnetic medium sedimentation link and further affects the sewage treatment efficiency, but also relates to the dosage of a medicament, the dosage of the magnetic medium and the like, and is closely related to the operation cost of the system.

Disclosure of Invention

The invention provides a method for solving the technical problem, aiming at solving the problem of how to determine the optimal system magnetic cement ratio of a magnetic coagulation water treatment system, so that the magnetic coagulation water treatment system can stably operate with the highest efficiency and the most economic operation cost, and the main concept is as follows:

a method for determining an optimal system magnetic cement ratio is applied to a magnetic coagulation water treatment system, the magnetic coagulation water treatment system comprises a coagulation device for conditioning sewage and a precipitation device for separating magnetic cement, the coagulation device is constructed with a mixing and stirring tank, and a stirrer is arranged in the mixing and stirring tank; the mixing and stirring tank is communicated with the sedimentation device, and a sludge discharge port of the sedimentation device is communicated with the mixing and stirring tank and used for refluxing the magnetic sludge; the method comprises the following steps:

s2, respectively taking out quantitative slurry from the mixing and stirring tank to perform a settling test under the conditions of solid content and different magnetic mud ratios N of the same system, and respectively calculating settling velocities V corresponding to the different magnetic mud ratios N to obtain a plurality of groups of measurement data with the magnetic mud ratio N as an abscissa and the settling velocity V corresponding to the magnetic mud ratio N as an ordinate;

s3, marking each group of measured data in a plane rectangular coordinate system, and obtaining an N-V fitting curve through data fitting;

s4, obtaining the optimal system magnetic mud ratio N according to the N-V fitting curve ₀ . In the scheme, in the running process of the magnetic coagulation water treatment system, under the condition that the solid content of the system is kept to be constant, taking out quantitative slurry from a mixing and stirring tank to perform a sedimentation test, so as to obtain a plurality of groups of measurement data with a magnetic mud ratio N as a horizontal coordinate and a sedimentation speed V corresponding to the magnetic mud ratio N as a vertical coordinate; therefore, an N-V fitting curve can be obtained by using the measurement data, and finally, the optimal system magnetomud ratio N can be intuitively and conveniently obtained from the N-V fitting curve ₀ . So that the optimal system magnetic cement ratio N can be used before the magnetic coagulation water treatment system is operated ₀ Calculating the dosage of the magnetic medium, the dosage of the medicament and the like for reference; therefore, in the running process of the magnetic coagulation water treatment system, the magnetic medium can be added according to the calculated adding amount of the magnetic medium, the medicament can be calculated according to the calculated adding amount of the medicament, and the magnetic coagulation water treatment system can use the optimal system magnetic cement ratio N ₀ The stable operation can not only ensure that the system has higher or highest sedimentation efficiency, but also ensure that the system has better or best economy, thereby effectively solving the problems in the prior art.

To solve the problem of calculating the sedimentation velocity, preferably, the sedimentation test comprises the following steps: the slurry taken out of the mixing and stirring tank is placed in a container, then the sedimentation height of the material group in the container is observed, the sedimentation height of the material group at different sedimentation time points is recorded, and finally the sedimentation velocity V is calculated according to the recorded data.

Due to the optimal system magnetic-mud ratio N ₀ The method is related to system solid content parameters of the system, and further comprises a step S1 of calculating the optimal system solid content range of the magnetic coagulation water treatment system and ensuring that the system solid content of the magnetic coagulation water treatment system is in the optimal solid content range in order to solve the problem that the system can operate at the highest efficiency and the lowest cost under different water inlet quality conditions. In this step, by calculating the optimum system solid content range of the magnetic coagulation water treatment system, the operation state of the magnetic coagulation water treatment system can be controlled by taking the optimum system solid content range as a reference, so that the magnetic coagulation water treatment system can be operated under different influent water quality conditionsThe solid content of the system can be in the range of the optimal solid content of the system, so that the optimal magnetic-mud ratio N of the system is calculated based on the range of the optimal solid content of the system ₀ Basically keeps unchanged, thereby ensuring that the system has the optimal system magnetic mud ratio N under the conditions of different inlet water quality ₀ The purposes of efficient precipitation and low-cost operation can be achieved.

In order to solve the problem that the magnetic coagulation water treatment system can be ensured to operate in the optimal state through control under different water inlet quality conditions, in a second aspect of the invention, the step S1 further comprises the following steps:

s1.2, calculating the optimal stirring intensity G of the mixing and stirring pool ₀ And calculating the optimal rotating speed of the stirrer according to the optimal stirring intensity;

s1.3 at optimum stirring intensity G ₀ In the case of (2) calculating the optimum solid content range [ a, b ] of the system]；

S1.4, controlling the stirrer to operate at the optimal rotating speed, and monitoring the solid content H of the system in the mixing and stirring tank; the system solid content in the mixing and stirring tank is adjusted by changing the reflux amount of the magnetic mud, so that the system solid content H is in the optimal solid content range. In the method, the stirring strength is used as a coagulation stirring control index instead of a coagulation effect control index, so that the limitation of adopting a G value and a GT value as coagulation effect control indexes in the design and operation of the existing mixing stirring tank is solved; in the operation process of the mixing and stirring tank, the higher the stirring strength is, the better the coagulation effect is, therefore, in step S1.2, based on the actual mixing and stirring tank, the optimal stirring strength of the mixing and stirring tank is calculated, and substantially, in order to find the optimal stirring strength corresponding to the optimal coagulation effect of the mixing and stirring tank, the optimal rotating speed of the stirrer can be calculated according to the optimal stirring strength, so that in the actual operation process, the optimal coagulation effect can be obtained in the mixing and stirring tank only by controlling the rotating speed of the stirrer to the optimal rotating speed. Due to different water quality conditionsThe treatment effect of the whole system can have larger fluctuation and difference, therefore, in the method, the solid content of the system is creatively used as the control index of the coagulation effect, and the optimal stirring intensity G is achieved ₀ In the case of (2) calculating the optimum solid content range [ a, b ] of the system]The system can effectively represent the coagulation effect of the whole system and is convenient to control the coagulation effect of the system by utilizing the optimal solid content range, so that the stirrer can run at the optimal rotating speed in the actual running process, and the system solid content H in the mixing and stirring tank can be synchronously monitored; when the solid content of the system exceeds the optimal solid content range [ a, b ]]During the process, the system solid content in the mixing and stirring tank can be adjusted by changing the magnetic mud reflux amount, so that the system solid content H is in the optimal solid content range, the precise control of the magnetic coagulation water treatment process is convenient to realize, the designed magnetic coagulation water treatment system can be ensured to operate in a mode most favorable for improving the sewage treatment effect under various water quality conditions, and the effluent quality can be obviously improved.

In order to solve the problems associated with the design and operation of the system, the method further comprises a step S1.1 of determining pool shape parameters of a mixing and stirring pool in the coagulation device, and determining size structural parameters of the stirrer according to the pool shape parameters and design specifications, wherein the size structural parameters at least comprise blade diameter, blade number and blade width. In this scheme, confirm earlier that mix the pond shape parameter in stirring the pond, confirm the size structure parameter of agitator through pond shape parameter, not only make the agitator more adapt mix the stirring pond, under the condition that pond shape parameter and size structure parameter all match best moreover, can also obtain best stirring intensity through the rotational speed that changes the agitator for the design of system is in the same place with the accurate relevance of operation effect.

In order to solve the problem of calculating the optimal stirring intensity of the mixing pool in the magnetic coagulation water treatment system in the third aspect of the present invention, further, in step S1.2, a G-df fitting curve is first calculated, and the optimal stirring intensity G is obtained through the G-df fitting curve ₀ And df represents a two-dimensional fractal dimension of a flocculating constituent in the sewage. The mixing intensity is used as the index of the coagulation mixing control and not as the mixingUnder the condition of the coagulation effect control index, the method further introduces the concept of 'fractal dimension' containing information such as the size, the density and the like of the flocculating constituent by analyzing the coagulation morphology theory as the coagulation effect control index, the change of the fractal dimension can more accurately reflect the forming process and the rule of the flocculating constituent under certain stirring conditions, and the optimal stirring strength of each mixing and stirring tank can be more accurately calculated; meanwhile, the method obtains the optimal stirring intensity by utilizing the G-df fitting curve, can avoid the interference of other factors, and is very convenient, accurate and efficient.

To solve the problem of facilitating obtaining the optimum stirring intensity, it is preferable that the optimum stirring intensity G is calculated in step S1.2 ₀ The method comprises the following steps:

s1.2.1, taking the rotating speed of a stirrer as a variable, inspecting the two-dimensional fractal dimension df of a flocculating constituent in sewage under different G values by changing the rotating speed of the stirrer, and obtaining at least three groups of measurement data with the G value as a horizontal coordinate and the df as a vertical coordinate;

s1.2.2, marking each group of measurement data in a plane rectangular coordinate system, and obtaining a G-df fitting curve through data fitting;

s1.2.3 and obtaining the optimal stirring intensity G according to the G-df fitting curve ₀ 。

In order to solve the problem of conveniently measuring the two-dimensional fractal dimension of the flocculating constituent in the sewage, further, the method for measuring the two-dimensional fractal dimension df of the flocculating constituent in the sewage comprises the following steps: firstly, a proper amount of coagulated suspension is placed on a glass slide from a mixing and stirring stage Chi Naqu;

measuring L and A of at least two flocculants under a microscope to obtain at least two groups of data points with lnL as a horizontal coordinate and lnA as a vertical coordinate, wherein A is a projection plane of the flocculants, and L is the maximum circumference of projection;

and finally, performing linear fitting on each group of data points, wherein the slope of the fitted linear is the two-dimensional fractal dimension df.

In a fourth aspect of the present invention, to solve the problem of calculating the optimal solid content range of the magnetic coagulation water treatment system, further, in step S1.3, an H-df fitting curve is first calculated, and the optimal solid content range [ a, b ] is obtained through the H-df fitting curve, where H represents the solid content of the system. In the method, the optimal solid content range [ a, b ] of the system is calculated by an H-df fitting curve, so that the solid content H of the system and the two-dimensional fractal dimension df can be associated together, the relationship between the solid content and the coagulation effect can be intuitively and accurately reflected by using the two-dimensional fractal dimension df, and the optimal solid content range can be obtained more conveniently. And the method can be matched with the optimal stirring intensity to obtain the optimal solid content range of the system under the optimal stirring intensity condition, so that the whole system can operate in a mode most beneficial to improving the sewage treatment effect under various water quality conditions, and the effluent quality can be obviously improved.

To solve the problem of easy calculation of the optimum solid content range, it is preferable that the method of calculating the optimum solid content range [ a, b ] in step S1.3 is:

s1.3.1 and keeping the stirring intensity of the mixing and stirring tank at G ₀ Taking the system solid content H in the mixing and stirring tank as a variable, and investigating the two-dimensional fractal dimension df of a flocculating constituent in sewage under the condition of the same stirring strength by changing the system solid content H in the mixing and stirring tank, and obtaining at least three groups of measurement data with H as a horizontal coordinate and df as a vertical coordinate;

s1.3.2 marking each group of measurement data in a plane rectangular coordinate system, and obtaining an H-df fitting curve through data fitting;

s1.3.3, and obtaining the optimal solid content range [ a, b ] of the system according to the H-df fitting curve.

Preferably, in the step S1.3.3, the method for calculating the optimal lower limit a of solid content is: setting a two-dimensional fractal dimension lower limit df0, and calculating the corresponding system solid content H by using a fitting formula corresponding to an H-df fitting curve or an H-df fitting curve ₀ And let a = H ₀ ；

And/or the method for calculating the upper limit b of the optimal solid content is as follows: setting two-dimensional fractal dimension upper limit df1, and calculating corresponding system solid content H by using a fitting formula corresponding to an H-df fitting curve or an H-df fitting curve ₁ And let b = H ₁ 。

Preferably, the lower fractal dimension limit df0=2; and/or, the upper fractal dimension limit df1=3.

In order to solve the problem of convenience in measuring multiple sets of measurement data, further, in step S1.3.1, the system solid content H in the mixing and stirring tank is changed by changing the reflux amount of the magnetic mud. The solid content H of the system in the mixing and stirring tank is changed in such a way, so that the operation is simple and convenient, and a group of measurement data can be measured under the working condition of each solid content H of the system, so that a plurality of groups of measurement data can be conveniently obtained, and an H-df fitting curve can be conveniently calculated.

In a fifth aspect of the present invention, a problem of accurately controlling the flux of return sludge on-line during the operation of the magnetic coagulation water treatment system is solved, and further, the magnetic coagulation water treatment system is further provided with a controller, a sensor and a flow control device, wherein the controller is electrically connected with the sensor, the stirrer and the flow control device respectively, and the flow control device is arranged on a communication path between the sludge discharge port and the coagulation device;

in the step S1.4, the controller is utilized to control the stirrer to run at the optimal rotating speed, and the sensor is utilized to monitor the solid content H of the system in the mixing and stirring tank; when the solid content H of the system is larger than the upper limit b of the optimal solid content, the controller reduces the reflux amount of the magnetic mud by controlling the flow control device, so that the solid content of the system in the mixing and stirring tank is reduced, and the solid content H of the system is in the optimal solid content range; when the solid content H of the system is smaller than the lower limit a of the optimal solid content, the controller controls the flow control device to improve the reflux amount of the magnetic mud, so that the solid content of the system in the mixing and stirring pool is increased, and the solid content H of the system is in the optimal solid content range. The scheme detects and controls the solid content of the system, so that the system can operate in the optimal solid content range under any water quality condition, and the effluent quality can be ensured to reach the standard.

Preferably, the flow control device adopts a control valve. The controller valve comprises a two-way control valve, a three-way control valve and the like.

Preferably, the controller is a PC, a singlechip or a PLC.

Preferably, the sensor is an online suspended matter monitor.

The sixth aspect of the invention provides a magnetic coagulation water treatment process, which comprises the step of calculating the optimal solid content range [ a, b ] of a magnetic coagulation water treatment system according to the method]Optimum system magnetic mud ratio N ₀ And the optimum rotational speed of the agitator;

controlling the stirrer to operate at the optimal rotating speed in the operation process of the magnetic coagulation water treatment system; and the system solid content in the mixing and stirring tank is adjusted by controlling and changing the reflux quantity of the magnetic mud, so that the system solid content H is always in the optimal solid content range [ a, b ]]Internal; and the actual magnetic mud ratio of the system is equal to the optimal system magnetic mud ratio N ₀ Or at the optimum system magnetic mud ratio N ₀ In the presence of a surfactant.

Compared with the prior art, the method for determining the optimal system magnetic cement ratio and the magnetic coagulation water treatment process provided by the invention can determine the optimal system magnetic cement ratio of the magnetic coagulation water treatment system, so that when the magnetic coagulation water treatment system runs at the optimal system magnetic cement ratio, the system can be ensured to have higher precipitation efficiency, and the system can be ensured to have better economy, thereby effectively solving the problems in the prior art.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

Fig. 1 is a block diagram of a method for determining an optimal system magnetic-mud ratio according to an embodiment of the present invention.

Fig. 2 is a schematic structural diagram of a first magnetic coagulation water treatment system provided in an embodiment of the present invention.

Fig. 3 is a schematic structural diagram of a second magnetic coagulation water treatment system provided in an embodiment of the present invention.

Fig. 4 is a schematic structural diagram of a third magnetic coagulation water treatment system provided in the embodiment of the present invention.

FIG. 5 is a graph of a G-df fit obtained using the method provided by the present invention.

FIG. 6 is another graph of a G-df fit obtained using the method provided by the present invention.

FIG. 7 is a graph of an H-df fit obtained using the method provided by the present invention.

FIG. 8 is a graph of an N-V fit obtained using the method of the present invention.

Description of the drawings

PAC production apparatus 101, PAC metering pump 102, PAM production apparatus 103, and PAM metering pump 104

The coagulation device 200, a first mixing and stirring tank 201, a second mixing and stirring tank 202, a third mixing and stirring tank 203, a sensor 204, a stirrer 205, a baffle plate 206 and a guide cylinder 207

The sedimentation device 300, the sedimentation cavity 301, the inclined pipe 302, the reflux pump 303, the flow control device 304, the magnetic sludge pump 305, the excess sludge pump 306, the pipeline 307 and the stirring mechanism 308

The magnetic recovery device 400.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

The embodiment provides a method for determining the optimal system magnetic cement ratio in a magnetic coagulation water treatment system, which is mainly applied to the magnetic coagulation water treatment system, wherein,

as shown in fig. 2, the magnetic coagulation water treatment system includes a PAC production apparatus 101, a PAM production apparatus 103, a coagulation apparatus 200 for conditioning sewage, a precipitation apparatus 300 for separating magnetic sludge, a magnetic recovery apparatus 400, and a controller, wherein,

as shown in fig. 2, the coagulation apparatus 200 is constructed with a mixing and stirring tank to provide a space for the coagulation process and the flocculation process of the sewage, and a stirrer 205 is provided in the mixing and stirring tank to enhance the stirring strength. In practice, the number of mixing tanks constructed in the coagulation device 200 may be determined according to actual requirements, and preferably, at least two mixing tanks communicating with each other may be constructed in the coagulation device 200. For example, as shown in fig. 2, three mixing and stirring tanks are constructed in the coagulation apparatus 200, and the coagulation apparatus 200 is provided with a water inlet and a water outlet, which are respectively communicated with the mixing and stirring tanks located at the ends. For convenience of description, the three mixing and stirring tanks are respectively a first mixing and stirring tank 201, a second mixing and stirring tank 202 and a third mixing and stirring tank 203, the first mixing and stirring tank 201, the second mixing and stirring tank 202 and the third mixing and stirring tank 203 are sequentially communicated with each other, as shown in fig. 2, a water inlet is communicated with the first mixing and stirring tank 201, a water outlet is communicated with the third mixing and stirring tank 203, a stirrer 205 may be disposed in the first mixing and stirring tank 201, and the stirrer 205 is mainly used for enhancing the stirring intensity in the first mixing and stirring tank 201, as shown in fig. 4; several static baffles 206 may also be provided, as shown in fig. 2 or fig. 3, the static baffles 206 are mainly used to make the flow path of the sewage more tortuous, so that the coagulant and the sewage can be sufficiently mixed in the first mixing stirring tank 201. An agitator 205 is arranged in the second mixing and stirring tank 202, and the added magnetic medium and the refluxed magnetic mud are generally added into the second mixing and stirring tank 202, as shown in fig. 2-4. A stirrer 205 is arranged in the third mixing and stirring tank 203, so that the sewage can be fully mixed with the added coagulant aid and can react.

In the present embodiment, the PAC preparation apparatus 101 is in communication with the water inlet, and as shown in fig. 2, the PAC preparation apparatus 101 is mainly used for preparing a medicament, such as a coagulant. In practice, PAC preparation apparatus 101 is further provided with a PAC metering pump 102 in communication with the water inlet, so that output of the medicament can be precisely controlled by PAC metering pump 102. As shown in fig. 2, the PAM preparation apparatus 103 may be in communication with the third mixing and stirring tank 203 through a pipe 307, so as to add the prepared coagulant aid into the third mixing and stirring tank 203, and similarly, in implementation, a PAM metering pump 104 is further disposed on a communication path between the PAM preparation apparatus 103 and the third mixing and stirring tank 203, so as to precisely control the output of the medicine by using the PAM metering pump 104.

In this embodiment, the sedimentation device 300 may be an existing sedimentation tank, and the sedimentation device 300 may implement separation of magnetic sludge from the water body in the sewage by using a sedimentation method. For example, as shown in fig. 2, the sedimentation device 300 is configured with a sedimentation chamber 301, a sludge discharge port and a water outlet, wherein the sludge discharge port and the water outlet are respectively communicated with the sedimentation chamber 301, the water discharge port of the coagulation device 200 is communicated with the sedimentation chamber 301 of the sedimentation device 300, and an inclined pipe 302 (or an inclined plate) for enhancing sedimentation, a stirring mechanism 308 (including a motor, a transmission shaft for driving and connecting the motor, a hanger mounted on the transmission shaft, etc.) and the like are generally arranged in the sedimentation chamber 301, as shown in fig. 2, and will not be described herein again. In the actual operation process, sewage is precipitated in the precipitation cavity 301 of the precipitation device 300, the precipitated magnetic mud is discharged out of the precipitation device 300 through the mud discharge port, and clear water after the magnetic mud is separated is discharged out through the water outlet.

In this embodiment, the magnetic recycling device 400 is mainly used for recycling the magnetic medium in the magnetic mud, and an existing magnetic disc type magnetic separator or a drum type magnetic separator or the like may be used to separate the magnetic medium from the mud in the magnetic mud by using the principle of magnetic adsorption. When assembled, the magnetic recovery device 400 is communicated with the sludge discharge port of the settling device 300 so as to receive and separate magnetic media in the magnetic sludge; the magnetic recycling device 400 is further communicated with the coagulation device 200, for example, as shown in fig. 2, the magnetic recycling device 400 is communicated with the second mixing and stirring tank 202 of the coagulation device 200, so that at least part of the recycled magnetic medium is thrown into the second mixing and stirring tank 202 to realize recycling of the magnetic medium.

In this embodiment, the coagulation device 200 is also communicated with the sludge discharge port of the sedimentation device 300 to return the magnetic sludge, as shown in fig. 2. Since the magnetic recovery device 400 and the coagulation device 200 are respectively communicated with the sludge discharge port of the sedimentation device 300, during the operation process, the requirement of magnetic sludge backflow is firstly met, and the residual sludge (called residual sludge for short) enters the magnetic recovery device 400. In order to split the magnetic sludge, there are various embodiments, and in this embodiment, for example, a reflux pump 303 and a flow rate control device 304 for controlling the reflux amount are disposed in a communication path between the sludge discharge port of the settling device 300 and the coagulation device 200. In practice, the flow control device 304 may be a control valve, which may be a two-way control valve, a three-way control valve, etc. commonly used in the art, and in this embodiment, the flow control device 304 is a solenoid valve, for example. Of course, in a more sophisticated scheme, in order to monitor the backflow amount of the magnetic mud, a flow meter can be further disposed on the communication path between the mud discharge port of the sedimentation device 300 and the coagulation device 200. Meanwhile, a surplus sludge pump 306 is disposed on a communication path between the magnetic recovery apparatus 400 and the sedimentation apparatus 300 so that surplus magnetic sludge is input into the magnetic recovery apparatus 400 by the surplus sludge pump 306, as shown in fig. 2. In practice, the sludge discharge port and the coagulation device 200 may be communicated through a pipe 307 or a channel, and similarly, the sludge discharge port and the magnetic recovery device 400 may also be communicated through a pipe 307 or a channel.

In the actual operation process, the sewage enters the first mixing and stirring tank 201 of the coagulation device 200 through the water inlet, and is fully mixed with the coagulant in the first mixing and stirring tank 201; then the sewage enters a second mixing and stirring tank 202, and under the action of a stirrer 205, the magnetic medium, the backflow magnetic sludge and the sewage are fully mixed in the second mixing and stirring tank 202; then the sewage enters a third mixing and stirring tank 203, and is fully mixed with a coagulant in the third mixing and stirring tank 203, then enters the sedimentation device 300 through a water outlet, and is precipitated in the sedimentation device 300, the separated clear water is discharged through a water outlet of the sedimentation device 300, the precipitated magnetic mud is conveyed backwards through a mud outlet of the sedimentation device 300, and can flow part of the magnetic mud back to the coagulation device 200 according to the requirement, the residual mud is input into a magnetic recovery device 400 for recovering the magnetic medium, and the recovered magnetic medium can be conveyed into the coagulation device 200, so as to realize the recycling of the magnetic medium.

Based on the magnetic coagulation water treatment system with the structure, in order to determine the optimal system magnetic cement ratio of the magnetic coagulation water treatment system, as shown in fig. 1, in order to closely correlate the design of the magnetic coagulation water treatment system with the control in the actual operation process, the method provided by the embodiment comprises the following steps:

step S1, calculating the optimal system solid content range of the magnetic coagulation water treatment system, and ensuring that the system solid content is in the optimal solid content range in the operation process of the magnetic coagulation water treatment system. Due to the optimal system magnetic mud ratio N ₀ In the step, the operation state of the magnetic coagulation water treatment system can be controlled by taking the optimal system solid content range as reference through calculating the optimal system solid content range of the magnetic coagulation water treatment system, so that the system solid content of the magnetic coagulation water treatment system can be in the optimal system solid content range under different water inlet quality conditions, and the optimal system magnetic cement ratio N calculated based on the optimal system solid content range is ensured to be N ₀ Basically keeps unchanged, thereby ensuring that the system has the optimal system magnetic mud ratio N under the conditions of different inlet water quality ₀ The purposes of efficient precipitation and low-cost operation can be achieved.

And S2, respectively taking out quantitative slurry from the mixing and stirring tank to perform a sedimentation test under the conditions of the solid content of the same system (namely, the actual solid content of the system in the actual operation process of the system, wherein the solid content of the system of the magnetic coagulation water treatment system is in the optimum system solid content range according to the step S1, so that the solid content of the system belongs to the optimum system solid content), and different magnetic mud ratios N, and respectively calculating sedimentation speeds V corresponding to the different magnetic mud ratios N to obtain a plurality of groups of measurement data with the magnetic mud ratio N as an abscissa and the sedimentation speed V corresponding to the magnetic mud ratio N as an ordinate.

To facilitate the calculation of the sedimentation velocity, in a further embodiment, the sedimentation test in step S2 comprises the steps of: firstly, placing slurry (namely a mixture consisting of water, magnetic medium, sludge, medicament and the like) taken out from a mixing and stirring tank into a container; the amount taken can be determined according to actual requirements, for example, 1L, 1.5L, 2L and the like can be taken each time, and the container can adopt an existing measuring cylinder or measuring cup and the like. And then observing the sedimentation height of the material group in the container, recording the sedimentation heights of the material group at different sedimentation time points, and finally respectively calculating the corresponding sedimentation velocity V according to the recorded data.

And S3, marking each group of measurement data in a plane rectangular coordinate system, and obtaining an N-V fitting curve through data fitting, as shown in FIG. 8.

S4, obtaining the optimal system magnetic mud ratio N according to the N-V fitting curve ₀ . Specifically, in the running process of the magnetic coagulation water treatment system, under the condition that the solid content of the system is kept to be constant, taking out quantitative slurry from the mixing and stirring tank for a sedimentation test to obtain a plurality of groups of measurement data with a magnetic mud ratio N as an abscissa and a sedimentation velocity V corresponding to the magnetic mud ratio N as an ordinate; therefore, an N-V fitting curve can be obtained by using the measurement data, and finally, the optimal system magnetomud ratio N can be intuitively and conveniently obtained from the N-V fitting curve ₀ . So that the optimal system magnetic cement ratio N can be used before the magnetic coagulation water treatment system is operated ₀ Calculating the dosage of the magnetic medium, the dosage of the medicament and the like for reference; therefore, in the running process of the magnetic coagulation water treatment system, the magnetic medium can be added according to the calculated adding amount of the magnetic medium, the medicament can be calculated according to the calculated adding amount of the medicament, and the magnetic coagulation water treatment system can use the optimal system magnetic cement ratio N ₀ Stable operation ensures not only the highest sedimentation efficiency of the system, but also the best economy of the system.

The design and operation and maintenance of equipment (especially equipment in a magnetic medium coagulation stirring link) in the existing magnetic coagulation water treatment system still use the theoretical system of the traditional coagulation sedimentation, and neglects the key factor that the density of formed floccules is higher because a magnetic medium with large specific gravity is introduced in the process of treating the magnetized and precipitated water.On the other hand, in the magnetic coagulation water treatment system, the magnetic medium coagulation stirring link is the core of the whole system, and in order to control the sewage treatment effect, the prior art generally adopts a G value and a GT value as coagulation control indexes, wherein G represents the velocity gradient of the motion of two particles in two adjacent water layers, and means that the particle collision frequency is reflected due to the velocity difference (also called as the stirring strength) of stirring in the distance of vertical water flow; the GT value corresponds to the total number of particle collisions per unit volume of water. Because the G value is obtained when the water flow is in a laminar flow state, actually, in a flocculation stage, the water flow is not laminar flow but always in a turbulent flow state, and vortexes with different sizes exist in the fluid, and besides the advancing speed, longitudinal and transverse pulsating speeds also exist, namely the G value only can represent the space average dissipation rate of energy and cannot reflect the dissipation rate of each local energy; GT value is too large (10) ⁴ ～10 ⁵ ) Can always meet the requirements, and loses the practical control significance; and the G value and the GT value can only be measured in a laboratory generally and cannot be measured on line in the sewage treatment process, so that the actual operation process of the magnetic coagulation water treatment system is difficult to control through the G value and the GT value. Based on the two reasons, the existing magnetic coagulation water treatment system is disconnected from the control in the actual operation process, so that the designed magnetic coagulation water treatment system is difficult to operate in a mode most beneficial to improving the sewage treatment effect under various water quality conditions, and the problems that the accurate control is inconvenient and the stable high-quality water outlet effect cannot be maintained along with the fluctuation of water quality in the actual operation process due to the lack of a proper control index are caused. In order to solve the technical problem, in the method, the step S1 specifically includes the following steps:

step S1.1, in the stage of designing the coagulation device 200 in the magnetic coagulation water treatment system, it is necessary to determine the pool shape parameters of the mixing and stirring pool in the coagulation device 200, where the pool shape parameters include the shape, size, and the like of the mixing and stirring pool, and then the size and structure parameters of the stirrer 205 may be determined according to the pool shape parameters and related design specifications (such as national standards, industry standards, and the like), the purpose of setting the stirrer 205 is to increase the stirring strength, and the stirrer 205 may be an existing stirrer 205, for example, the stirrer 205 may include a motor, a transmission shaft in transmission connection with the motor, and a plurality of blades mounted on the transmission shaft. In implementation, the dimensional and structural parameters at least include the diameter of the blades, the number of the blades, and the width of the blades, and of course, the number of layers of the stirrer 205, the installation angle of the stirring blades, and the like may also be included. So as to find the most suitable stirrer 205 which is most beneficial to improve the stirring intensity according to the mixing stirring pool after the pool shape parameters are determined, and further realize better coagulation effect. In practice, for a coagulation apparatus 200 constructed with a plurality of mixing tanks, each of which may be designed in the manner described above, in order to obtain the best mixing effect at each mixing tank, as shown in fig. 2 to 4.

Step S1.2, calculating the optimal stirring intensity G of the mixing and stirring tank ₀ And calculates the optimal rotation speed of the agitator 205 according to the optimal stirring intensity, wherein the optimal rotation speed can be the angular speed of the agitator 205 or the linear speed of the agitator 205. After the mixing and stirring tank and the stirrer 205 are designed and manufactured, in the actual operation process, the larger the rotating speed of the stirrer 205 is, the larger the stirring strength G in the mixing and stirring tank is, but in the magnetic coagulation water treatment process, the process with the best coagulation effect can meet two basic requirements: firstly, tiny particles in water form flocs which are easy to remove in the settling cavity 301 in the mixing and stirring tank; on the other hand, the coagulation is completed with the minimum duration, coagulant dosage and energy dissipation, thereby obtaining the maximum economic benefit. It was thus found that: the higher the stirring strength G, the less the optimum coagulation effect can be achieved in the mixing tank. In view of this, in combination with the limitations of the prior art that the G value and the GT value are used as the control indexes of the coagulation effect (wherein, G represents the velocity gradient of the movement of two particles in two adjacent water layers, which means that the collision frequency of the particles is reflected due to the velocity difference of the stirring in the distance of the vertical water flow (also called as "stirring intensity"), and the GT value is equivalent to the total number of particle collisions in the unit volume of water), the method only uses the stirring intensity G as the control indexes of the coagulation stirring and not as the control indexes of the coagulation effect, so as to solve the problems of the prior artIn the design and operation of the mixing and stirring tank, the G value and the GT value are adopted as the control indexes of the coagulation effect. Meanwhile, in the method, by analyzing the coagulation morphology theory, the concept of 'fractal dimension' containing information such as the size, the density and the like of the flocculating constituent is introduced as a coagulation effect control index, and the change of the fractal dimension can more accurately reflect the forming process and the forming rule of the flocculating constituent under certain stirring conditions. In the method, the fractal dimension of the flocculating constituent is calculated according to the functional relation between the projected area and the maximum perimeter of the flocculating constituent, and the functional relation between the projected area and the maximum length of the flocculating constituent is as follows:

A＝αL ^df

in the formula: a-is a projection surface of the flocculating constituent;

l-is the maximum circumference of the projection;

alpha-is a proportionality constant;

df-is the two-dimensional fractal dimension of the floccule.

And solving the natural logarithm of the formula to obtain:

ln A＝lnα+df ln L

as can be seen from the above formula, lnL and lnA are in a linear relationship, therefore, in this embodiment, the method for measuring the two-dimensional fractal dimension of the flocs in the sewage is as follows: firstly, taking out a proper amount of turbid liquid coagulated in the mixing and stirring tank by using a tripe pipette, and placing the turbid liquid on a glass slide; observing under a microscope, performing image processing on an electronic computer connected with an electronic microscope camera lens and a video image capturer, measuring L and A of different flocculants (at least two), and respectively calculating lnL and lnA, thereby obtaining at least two groups of data points with lnL as a horizontal coordinate and lnA as a vertical coordinate; and finally, performing straight line fitting on each group of data points by using data processing software (such as Excel, SPSS, MATLAB and the like), wherein the slope of the fitted straight line is the two-dimensional fractal dimension df of the flocculent in the sewage. In actual operation, in order to improve accuracy, at least two times of measurement can be carried out so as to obtain at least two fractal dimensions, and finally, the average value of the two fractal dimensions is obtained to be used as the final two fractal dimension df, so that the precision can be obviously improved, and the error can be obviously reduced.

For calculating the optimal stirring intensity G of a mixing and stirring tank in the magnetic coagulation water treatment system ₀ In a preferred embodiment, in step S1.2, a G-df fit curve is first calculated, as shown in fig. 5 and 6, and then the optimal stirring intensity G can be calculated by the G-df fit curve ₀ Wherein df represents a two-dimensional fractal dimension of a flocculating constituent in the sewage. For example, the optimum stirring intensity G is calculated in step S1.2 ₀ The method of (3) may comprise:

and S1.2.1, taking the rotating speed of the stirrer 205 as a variable, observing the two-dimensional fractal dimension df of the floccules in the sewage under different G values by changing the rotating speed of the stirrer 205, and obtaining at least three groups of measurement data with the G value as an abscissa and the df as an ordinate. Specifically, when the magnetic coagulation water treatment system is in operation, different stirring strengths G can be obtained by changing the rotation speed of the stirrer 205, and after each stirring strength G is stabilized, the two-dimensional fractal dimension df corresponding to the stirring strength G can be measured by using the method for measuring the two-dimensional fractal dimension, so that a set of measurement data can be obtained, and the above process can be repeated for 5 to 8 times, so as to obtain 5 to 8 sets of measurement data, as shown in fig. 5 and 6.

Step S1.2.2, marking each group of measurement data in a plane rectangular coordinate system, and obtaining a G-df fitting curve through data fitting. In this step, the data fitting process may be calculated by using existing data processing software, or may be calculated manually by using an existing mathematical formula, which is not described herein again, for example, as shown in fig. 5, a G-df fitting curve is obtained under the condition that only the stirrer 205 is arranged in the first mixing and stirring tank 201, and the guide cylinder 207 is not arranged; as shown in fig. 6, the G-df fit curve is obtained in the case where the stirrer 205 is provided in the first mixing/stirring tank 201 and the guide cylinder 207 is provided.

Step S1.2.3 obtaining the optimal stirring intensity G according to the G-df fitting curve ₀ . In practice, a G-df fit curve can be plotted, as shown in FIG. 5 or FIG. 6, and the highest point is found on the graph, and the abscissa corresponding to the highest point is the optimal stirring intensity G ₀ Of course, the maximum value pair can also be directly calculated by using the formula of G-df fitting curveThe optimum stirring intensity G can be obtained by the corresponding abscissa ₀ . As shown in FIGS. 5 and 6, the optimum stirring intensity G of the magnetic coagulation water treatment system was obtained ₀ Is 270s ^-1 。

When the optimum stirring intensity G is reached ₀ Once determined, the optimum stirring intensity G can be used ₀ The optimum rotation speed of the stirrer 205 is calculated, specifically, based on the optimum stirring intensity G ₀ The formula for calculating the optimum rotational speed of the agitator 205 is:

in the formula: q _t Mixing pool flow (m) ³ /s)；

The viscosity (Pa · s) of μ -water may be set to μ =1.14 × 10 in practical use ^-3 Pa·s；

K _g The duty factor of the motor in the agitator 205, which may be 1.2 when running continuously for 24h a day;

eta-the total mechanical transmission efficiency can be 0.92 in practical application;

c-drag coefficient, C = 0.2-0.5, and in practical application, C =0.5 may be selected;

the density of the rho-mixed liquid can be 1150kg/m in practical application ³ ；

ω -stirrer 205 rotational speed, ω =2 × (π n/60), rad/s, n is stirrer rotational speed;

z-number of stirring blades;

e-the number of layers of the stirrer 205, C = H/D, C > 1.3, and when the stirrer is actually applied, e =2 can be adopted; c is less than or equal to 1.3, e =1,D is taken as the equivalent diameter of the cross section of the tank body, and H is the height of the tank;

b-width of stirring blade, b = (0.1-0.25) d (m), d is the diameter of stirrer 205;

r-stirring blade radius, R = (1/6-1/3) D (m);

the mounting angle of the stirring blade is theta, and the angle can be 45 degrees in practical application;

g-acceleration of gravity, typically 9.8m/s ² 。

It is understood that when the coagulation apparatus 200 includes a plurality of mixing tanks each provided with the stirrer 205, the optimum stirring intensity G of each mixing tank can be calculated in step S1.2 ₀ And an optimum rotational speed of each agitator 205, such that each agitator 205 operates at its respective optimum rotational speed during actual operation.

Step S1.3, at optimum stirring intensity G ₀ In the case of (2) calculating the optimum solid content range [ a, b ] of the system]So as to optimize the solid content range [ a, b ]]The actual solid content of the system is controlled for reference, thereby achieving the purpose of effectively controlling the whole process. To facilitate calculation of the optimal solids content range for a magnetic coagulation water treatment system, in a preferred embodiment, an H-df fit curve is calculated, as shown in FIG. 7, and then the optimal solids content range [ a, b ] is obtained by the H-df fit curve]Wherein H represents the system solids content (which may also be referred to as suspended matter concentration, which refers to the concentration of suspended matter in the water body, including suspended sludge, magnetic media, flocculants, and the like). Specifically, the optimum solid content range [ a, b ] is calculated in step S1.3]The method comprises the following steps:

step S1.3.1, the rotation speed of the stirrer 205 is controlled to maintain the stirring intensity of the mixing and stirring tank at G ₀ I.e. so that the mixing and stirring tank has a stirring intensity G which is always at its optimum ₀ Status. Meanwhile, the system solid content H in the mixing and stirring tank is used as a variable, the two-dimensional fractal dimension df of the flocculating constituent in the sewage under the condition of the same stirring strength is investigated by changing the system solid content H in the mixing and stirring tank, and at least three groups of measurement data with H as a horizontal coordinate and df as a vertical coordinate can be obtained. Specifically, the rotation speed of the stirrer 205 is first maintained so that the stirring intensity of the mixing and stirring tank is kept at G ₀ To obtain the best stirring effect. Then changing the system solid content H in the mixing and stirring tank, sampling from the second mixing and stirring tank 202 or the third mixing and stirring tank 203 after the system is stable, and measuring the two-dimensional fractal dimension df corresponding to the system solid content H by using the method for measuring the two-dimensional fractal dimension of the flocculating constituent in the sewage, thereby obtaining a group of numbersBy so cycling, multiple sets of measurement data can be obtained, as shown in FIG. 7, and in a preferred embodiment, 5-8 sets of measurement data can be obtained.

In the test process, in order to change the system solid content H in the mixing and stirring tank, various embodiments are provided, for example, sewage with different water qualities can be introduced into the system to achieve the purpose of changing the system solid content H in the mixing and stirring tank, but the problem of troublesome operation exists. In a preferred embodiment, the system solid content H in the mixing and stirring tank can be changed by changing the magnetic mud reflux amount under the condition that the quality of the sewage entering the system is not changed, for example, the system solid content H =2000mg/L in the current mixing and stirring tank, after the current two-dimensional fractal dimension df is measured, the magnetic mud reflux amount of the system can be increased, so that the system solid content H of the whole system can be increased to 3000mg/L and maintained at the position of 3000mg/L, so as to measure the two-dimensional fractal dimension df at the moment, and then the system solid content H of the whole system can be increased to 4000mg/L, 5000mg/L, 6000mg/L, 7000mg/L and the like by increasing the magnetic mud reflux amount, as shown in fig. 7, so that multiple sets of measurement data can be conveniently and efficiently obtained, and the H-df fitting curve can be more conveniently calculated.

And S1.3.2, marking each group of measurement data in a plane rectangular coordinate system, and obtaining an H-df fitting curve through data fitting, which is very convenient. Similarly, in this step, the data fitting process may be calculated by using existing data processing software, or may be calculated manually by using an existing mathematical formula, which is not described herein again, for example, as shown in fig. 7, the data fitting process is an H-df fitting curve obtained by using the water sample in the second mixing and stirring tank 202.

Step S1.3.3, obtaining the optimal solid content range [ a, b ] of the system according to the H-df fitting curve]. Specifically, in one embodiment, the method for calculating the optimal lower limit a of solid content is: setting a two-dimensional fractal dimension lower limit df0, and calculating the corresponding system solid content H by using a fitting formula corresponding to an H-df fitting curve or an H-df fitting curve ₀ And let a = H ₀ . Similarly, the method for calculating the optimal solid content upper limit b is as follows: setting up two-dimensional fractal dimensionLimiting df1, calculating the corresponding system solid content H by using the H-df fitting curve or the fitting formula corresponding to the H-df fitting curve ₁ And let b = H ₁ Thus, the method is very convenient. In implementation, a lower limit df0 of the two-dimensional fractal dimension and an upper limit df1 of the two-dimensional fractal dimension may be determined according to actual requirements, and preferably, the lower limit of the two-dimensional fractal dimension may be set to df0=2; and/or, the upper limit of the fractal dimension may be set to df1=3.

The solid content of the system is a crucial influence factor for the magnetic-based synergistic water treatment technology, and the optimal solid content range of any magnetic coagulation water treatment system can be effectively determined by adopting the method, for example, as shown in fig. 7, the optimal solid content range is an H-df fitted curve of the magnetic coagulation water treatment system, and as can be seen from fig. 7: the solid content of the system in the system is less than 3000mg/L, the df value is less than 2, the coagulation effect is poor, and most of the coagulation effect is fine floccules, the reason for the coagulation effect is that the particle collision probability is low in the coagulation process, which is not beneficial to the coagulation among particles and the growth of particles, and the fine floccules are easily carried out by the overflow effluent of the sedimentation cavity 301, so that the effluent quality is influenced. When the solid content of the system is higher than 6000mg/L, the coagulation effect also tends to be poor, the solid content of the sedimentation cavity 301 is higher, the outlet water of the sedimentation cavity 301 runs out of flocs, the quality of the outlet water is influenced, and the impact resistance of the system is reduced. The reason for this is probably that when the solid content of the system is too high, the formed flocs are too much, and then the hydraulic action is influenced, so that part of the flocs have a descending trend, and the flocs which have an ascending trend are collided and broken up in the process. In conclusion, in the embodiment, the system solid content in the magnetic coagulation water treatment system is preferably controlled to be 3000-6000 mg/L, and the best effect can be obtained.

Step S1.4, controlling the agitator 205 to operate at the optimal rotation speed to obtain the optimal agitation effect, and simultaneously monitoring the system solid content H in the mixing and agitating tank, wherein the system solid content H in the second mixing and agitating tank 202 is generally equal to the system solid content H in the third mixing and agitating tank 203 because the materials in the second mixing and agitating tank 202 and the third mixing and agitating tank 203 are balanced, and in actual operation, monitoring the final mixing and agitating tank (in this embodiment, the final mixing and agitating tank 203 is monitored)) The solid content of the internal system is only H. In the operation process, when the system solid content H in the mixing and stirring tank fluctuates, the system solid content in the mixing and stirring tank can be adjusted by changing the reflux quantity of the magnetic mud, so that the system solid content H is in the optimal solid content range, and the whole system can operate in a state which is most favorable for improving the sewage treatment effect. Specifically, in the method, the stirring strength is used as a coagulation stirring control index instead of a coagulation effect control index, so that the limitation of adopting a G value and a GT value as coagulation effect control indexes in the design and operation of the existing mixing stirring tank is solved; in the operation process of the mixing and stirring tank, the higher the stirring strength is, the better the coagulation effect is, therefore, in step S1.2, based on the actual mixing and stirring tank, the optimal stirring strength of the mixing and stirring tank is calculated, and substantially, in order to find the optimal stirring strength corresponding to the optimal coagulation effect of the mixing and stirring tank, the optimal rotating speed of the stirrer can be calculated according to the optimal stirring strength, so that in the actual operation process, the optimal coagulation effect can be obtained in the mixing and stirring tank only by controlling the rotating speed of the stirrer to the optimal rotating speed. Because the treatment effect of the whole system can have larger fluctuation and difference under different water quality conditions, in the method, the solid content of the system is creatively used as the coagulation effect control index, and the optimal stirring strength G is ensured ₀ In the case of (2) calculating the optimum solid content range [ a, b ] of the system]The system can effectively represent the coagulation effect of the whole system and is convenient to control the coagulation effect of the system by utilizing the optimal solid content range, so that the stirrer can run at the optimal rotating speed in the actual running process, and the system solid content H in the mixing and stirring tank can be synchronously monitored; when the solid content of the system exceeds the optimal solid content range [ a, b ]]During the process, the system solid content in the mixing and stirring tank can be adjusted by changing the reflux quantity of the magnetic mud, so that the system solid content H is in the optimal solid content range, the precise control of the magnetic coagulation water treatment process is convenient to realize, andand the designed magnetic coagulation water treatment system can be ensured to operate in a mode most beneficial to improving the sewage treatment effect under various water quality conditions, and the quality of the discharged water can be obviously improved.

In an application scenario of the method, a worker may obtain the current system solid content H of the system by periodically and manually monitoring the system solid content H in the mixing and stirring tank, and may compare the current system solid content H of the system with the optimal solid content range of the system, and when the current system solid content H of the system is found to be greater than the optimal solid content upper limit b, the worker may manually adjust the flow control device 304 to reduce the backflow amount of the magnetic sludge, and at this time, the flow control device 304 may adopt a manual valve. Similarly, when the current system solid content H of the system is found to be less than the optimal solid content lower limit a, the worker can manually adjust the flow control device 304 to increase the reflux amount of the magnetic mud, so that the system can always keep continuous operation in a mode most beneficial to improving the sewage treatment effect, and the system is particularly suitable for occasions with small sewage quality fluctuation.

In another application scenario of the method, in order to accurately control the return flow of the magnetic cement during the operation of the magnetic coagulation water treatment system, further, the magnetic coagulation water treatment system is further provided with a controller and a sensor 204, the controller is electrically connected with the sensor 204, the stirrer 205 and the flow control device 304 respectively, and the sensor 204 is used for monitoring the system solid content H in the mixing and stirring tank and sending the system solid content H to the controller, as shown in fig. 2 to 4. The controller may control the amount of return of the magnetic slurry by controlling the flow control device 304, and in this case, the flow control device 304 may preferably employ an electric controller valve, a solenoid valve, a pneumatic valve, or the like. The controller can not only control the rotation speed of the stirrer 205, but also store the optimum solid content range [ a, b ] (can be stored in the controller, and can also be stored in a storage device connected with the controller) of the system in advance, so that the controller can be used for controlling the rotation speed of the stirrer 205 during the actual operation of the system, the stirrer 205 is ensured to operate at the optimum rotation speed, and the sensor 204 can be used for monitoring the system solid content H in the mixing and stirring pool so as to compare the optimum solid content range of the system; when the solid content H of the system is larger than the upper limit b of the optimal solid content, the controller can reduce the reflux amount of the magnetic mud through the flow control device 304, so that the solid content of the system in the mixing and stirring tank is reduced, and the solid content H of the system is in the optimal solid content range; when the solid content H of the system is smaller than the lower limit a of the optimal solid content, the controller can increase the reflux amount of the magnetic mud through the flow control device 304, so that the solid content of the system in the mixing and stirring tank is increased, and the solid content H of the system is in the optimal solid content range.

In implementation, the controller may preferably be a PC, a single chip, or a PLC, or the like, and of course, the controller may also be a DSP, an embedded chip, or the like. The sensor 204 may preferably be an online suspended matter monitor (or called online suspended matter monitor), and for example, an SIN-PSS100 suspended matter analyzer, a ZWYG-2088T online sludge concentration meter, a ZWYG-2087A suspended matter online analyzer, or the like may be used. Of course, a turbidity meter and the like can be adopted, and only the concentration of suspended matters in the sewage can be monitored.

For convenience of illustration, the present embodiment provides a method for determining the optimal magnetic-to-mud ratio of a system, for example, the optimal solid content range of the magnetic coagulation water treatment system is 3000-6000 mg/L. For example, during the operation of the magnetic coagulation water treatment system, the solid content of the system can be controlled in an optimal system solid content range; for example, the solid content of the system in the current magnetic coagulation water treatment system can be controlled to be about 4000mg/L, and under the condition of the coagulation mode, the magnetic mud ratio of the system can be set to be 0:1; 0.5; 1:1; 1.5; 2:1; 2.5; 3:1; 3.5; 4:1;4.5 (in the actual operation process, a sample can be taken out from the third mixing and stirring tank 203, and magnetic substance determination is performed, specifically, after the magnetic substance in the sample is purified, the magnetic substance is compared with the mass of the non-magnetic substance therein, that is, the magnetic sludge ratio can be achieved, and in addition, the purpose of adjusting the magnetic sludge ratio can be achieved by changing the amount of the residual sludge, which is not described herein again), so that a sedimentation experiment is performed, and thus a plurality of sedimentation rates can be obtained, so that a plurality of measurement data can be formed, so that an N-V fitting curve as shown in fig. 8 can be obtained.The test method can be as follows: the method comprises the steps of taking a transparent glass measuring cylinder with the capacity of 1L, cleaning and drying the transparent glass measuring cylinder, taking 1L of system slurry with different magnetic mud ratios, directly pouring the system slurry into the measuring cylinder, observing the sedimentation height of a material group in the measuring cylinder, and recording the sedimentation heights of the material group at different sedimentation time points (such as 5 minutes, 10 minutes and the like), so that the sedimentation speed can be calculated according to the sedimentation time points and the sedimentation heights of the material group. The N-V fit curve fitted from the experimental results is shown in fig. 8. As can be seen from fig. 8: along with the increase of the magnetic mud ratio, the sedimentation speed is increased, but when the sedimentation speed is higher than 2.0. As shown in FIG. 8, the magnetic cement ratio in the magnetic coagulation water treatment system can be controlled to be preferably 2.0 to 3.0. Namely, under the condition that the system solid content in the magnetic coagulation water treatment system can be controlled to be about 4000mg/L for operation, the optimal system magnetic cement ratio N ₀ The ratio of magnetic mud to N of the optimal system can be 2.0-3.0 ₀ Can be 2.5 ₀ The water outlet device operates under the dual conditions, so that the water outlet device is convenient to control and beneficial to improving the water outlet effect, and can stably operate with the highest efficiency and the most economic operation cost.

Example 2

The main difference between the present embodiment 2 and the above embodiment 1 is that in the magnetic coagulation water treatment system provided in the present embodiment, only one magnetic mud pump 305 may be disposed downstream of the mud discharge port of the settling device 300, specifically, as shown in fig. 3 or fig. 4, the mud discharge port of the settling device 300 is communicated with the magnetic mud pump 305, the magnetic mud pump 305 is communicated with the flow control device 304, the flow control device 304 is respectively communicated with the coagulation device 200 and the magnetic recovery device 400, and the controller is electrically connected with the flow control device 304 for distributing the backflow amount of the magnetic mud under the control of the controller. The purpose of accurately controlling the reflux quantity of the magnetic mud is achieved. Because the coagulation device 200 and the magnetic recovery device 400 are respectively communicated with the sludge discharge port of the sedimentation device 300 through the flow control device 304, the flow control device 304 is configured with an input end and two output ends, wherein the magnetic sludge pump 305 is communicated with the input end, and the two output ends are respectively communicated with the coagulation device 200 and the magnetic recovery device 400.

The control method based on the magnetic coagulation water treatment system is the same as that in the embodiment 1, and the description is omitted.

Example 3

The embodiment provides a magnetic coagulation water treatment process, which comprises the following steps: the optimum solids range [ a, b ] for the magnetic coagulation water treatment system was calculated according to the method described in example 1]Optimum system magnetic mud ratio N ₀ And the optimum rotational speed of the agitator;

controlling the stirrer to operate at the optimal rotating speed in the operation process of the magnetic coagulation water treatment system; and the system solid content in the mixing and stirring tank is adjusted by controlling and changing the reflux quantity of the magnetic mud, so that the system solid content H is always in the optimal solid content range [ a, b ]]Internal; and the actual magnetic mud ratio of the system is equal to the optimal system magnetic mud ratio N ₀ Or at the optimum system magnetic mud ratio N ₀ Within the range of (1). Is beneficial to obtaining the best water outlet effect with high efficiency and low cost.

In a preferred embodiment, the solid content H of the system in the magnetic coagulation water treatment system can be controlled within 3000-6000 mg/L, and the actual magnetic mud ratio of the system can be controlled within the range of 2.0-3.0, so that the best water outlet effect can be obtained more effectively and at low cost. .

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention.

Claims

1. A method for determining an optimal system magnetic cement ratio is applied to a magnetic coagulation water treatment system, the magnetic coagulation water treatment system comprises a coagulation device for conditioning sewage and a precipitation device for separating magnetic cement, the coagulation device is constructed with a mixing and stirring tank, and a stirrer is arranged in the mixing and stirring tank; the mixing and stirring tank is communicated with the sedimentation device, and a sludge discharge port of the sedimentation device is communicated with the mixing and stirring tank and used for refluxing the magnetic sludge; the method is characterized by comprising the following steps:

s3, marking each group of measurement data in a plane rectangular coordinate system, and obtaining an N-V fitting curve through data fitting;

s4, obtaining the optimal system magnetic mud ratio N according to the N-V fitting curve ₀ 。

2. The method for determining an optimal system flux-to-mud ratio of claim 1, wherein said settling test comprises the steps of:

firstly, placing the slurry taken out of the mixing and stirring tank into a container;

then observing the sedimentation height of the material group in the container, and recording the sedimentation heights of the material group at different sedimentation time points;

and finally, calculating the settling velocity V according to the recorded data.

3. The method for determining the optimal system magnetic cement ratio as claimed in claim 1, further comprising S1, calculating the optimal system solid content range of the magnetic coagulation water treatment system, and ensuring that the system solid content of the magnetic coagulation water treatment system is within the optimal solid content range [ a, b ].

4. The method for determining an optimal system flux-to-mud ratio as claimed in claim 3, wherein said S1 comprises the steps of:

s1.3, at optimum stirring intensity G ₀ In the case of calculating the optimum solid content range [ a, b ] of the system]；

S1.4, controlling the stirrer to operate at the optimal rotating speed, and monitoring the solid content H of the system in the mixing and stirring tank; the system solid content in the mixing and stirring tank is adjusted by changing the reflux amount of the magnetic mud, so that the system solid content H is in the optimal solid content range.

5. The method for determining the optimal system flux-mud ratio as claimed in claim 4, further comprising S1.1, determining pool shape parameters of a mixing and stirring pool in the coagulation device, and determining the size and structure parameters of the stirrer according to the pool shape parameters and design specifications, wherein the size and structure parameters at least comprise the diameter of the blades, the number of the blades and the width of the blades.

6. The method for determining the optimal system flux-to-mud ratio as claimed in claim 4, wherein in S1.2, a G-df fitting curve is calculated, and the optimal stirring intensity G is obtained by the G-df fitting curve ₀ Wherein df represents a two-dimensional fractal dimension of a flocculating constituent in the sewage;

and/or in S1.3, firstly calculating an H-df fitting curve, and obtaining an optimal solid content range [ a, b ] through the H-df fitting curve, wherein H represents the solid content of the system, and df represents the two-dimensional fractal dimension of the floccules in the sewage.

7. The method for determining the optimal system magnetic cement ratio according to any one of claims 4-6, wherein the magnetic coagulation water treatment system is further provided with a controller, a sensor and a flow control device, the controller is electrically connected with the sensor, the stirrer and the flow control device respectively, and the flow control device is arranged on a communication path of the sludge discharge port and the coagulation device;

in the S1.4, the stirrer is controlled to operate at the optimal rotating speed by using the controller, and the system solid content H in the mixing and stirring tank is monitored by using a sensor; when the solid content H of the system is larger than the upper limit b of the optimal solid content, the controller reduces the reflux amount of the magnetic mud by controlling the flow control device so as to reduce the solid content of the system in the mixing and stirring tank and ensure that the solid content H of the system is in the optimal solid content range; when the solid content H of the system is smaller than the lower limit a of the optimal solid content, the controller controls the flow control device to improve the reflux amount of the magnetic mud so as to increase the solid content of the system in the mixing and stirring pool and enable the solid content H of the system to be in the optimal solid content range.

8. The method for determining an optimal system flux-to-mud ratio of claim 7, wherein said flow control means employs a control valve;

and/or the controller is a PC, a singlechip or a PLC;

and/or the sensor adopts an online suspended matter monitor.

9. The method for determining the optimal system magnetic mud ratio as claimed in claim 6, wherein the method for measuring the two-dimensional fractal dimension df of the flocculent in the sewage is as follows: firstly, a proper amount of coagulated suspension is placed on a glass slide from a mixing and stirring stage Chi Naqu;

10. A magnetic coagulation water treatment process, characterized by comprising calculating the optimum solids content range [ a, b ] of a magnetic coagulation water treatment system according to the method of any one of claims 3 to 9]Optimum system magnetic mud ratio N ₀ And the optimum rotational speed of the agitator;

in the magnetControlling the stirrer to operate at the optimal rotating speed in the operation process of the coagulation water treatment system; and the system solid content in the mixing and stirring tank is adjusted by controlling and changing the reflux quantity of the magnetic mud, so that the system solid content H is always in the optimal solid content range [ a, b ]]Inner; and the actual magnetic mud ratio of the system is equal to the optimal system magnetic mud ratio N ₀ Or at the optimum system magnetic mud ratio N ₀ Within the range of (1).