Apparatus for treating heavy metal wastewater

Abstract

The application discloses a device for treating heavy metal wastewater, comprising a reaction tank, a stirring device, a dosing system, an aeration device and a sedimentation tank, a control unit for real-time monitoring of pH value and heavy metal concentration, dynamic adjustment of sodium sulfide dosage and aeration quantity: when pH is lower than 8.5-9.5, sodium sulfide is added at 1.5-3 L / min, and when pH is higher, an acidic neutralizing agent is added at 0.5-1.5 L / min; at the same time, the aeration quantity is adjusted to 2-10 m 3 / h according to the heavy metal concentration. When pH is stable, the dosing flow is reduced to 0.5-1 L / min and the aeration quantity is reduced to 1-3 m 3 / h. The application is used for industrial wastewater treatment, can improve heavy metal removal efficiency and reduce reagent consumption.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heavy metal wastewater treatment equipment, and particularly relates to a device for treating heavy metal wastewater. BACKGROUND

[0002] Heavy metal wastewater mainly comes from electroplating, metallurgy, chemical industry and other industries, and its treatment difficulty lies in the stable removal of heavy metal ions and the accurate control of reaction conditions. The traditional treatment method usually adopts chemical precipitation method, that is, by adding sodium sulfide and other reagents to make heavy metals form sulfide precipitate, but there are the following problems:

[0003] Firstly, the control of pH value is crucial to the formation of sulfide, but the existing technology relies on manual monitoring and adjustment, resulting in inaccurate reagent dosage. If the pH value is too high, the heavy metal hydroxide precipitate may compete, reducing the sulfide precipitation efficiency; if the pH value is too low, hydrogen sulfide gas may escape, causing secondary pollution. Due to the large fluctuation of wastewater quality, manual adjustment is difficult to respond in real time, which may cause reagent waste or substandard treatment effect.

[0004] Secondly, the control of aeration amount is usually fixed or only based on experience adjustment, lacking dynamic correlation with heavy metal concentration. Insufficient aeration may lead to uneven reaction and small precipitate particles difficult to settle; excessive aeration may destroy the formed flocs, increasing the load of subsequent sedimentation tank. The aeration system in the existing technology is usually operated independently, without being optimized in cooperation with reagent addition, stirring and other links, resulting in high energy consumption and limited treatment efficiency.

[0005] In addition, the reagent addition system of the traditional equipment usually adopts fixed-time or fixed-quantity addition, which cannot adjust the reagent dosage according to the real-time heavy metal concentration of wastewater. High-concentration wastewater requires higher aeration intensity to promote mixing and oxidation, but the existing equipment lacks linkage mechanism, which may easily cause problems such as local reagent excess or insufficient reaction.

[0006] The root cause of the above problems lies in the disconnection between monitoring and control links, resulting in system response lag. Developing an integrated device capable of real-time monitoring of water quality parameters and dynamic adjustment of reagent addition, aeration and stirring is the key to improving the treatment efficiency of heavy metal wastewater. SUMMARY

[0007] It is an object of the present application to solve at least the above problems and / or deficiencies and to provide at least the advantages described hereinafter.

[0008] It is an object of the present application to provide a device for treating heavy metal wastewater, which can solve the problem of reagent waste or low precipitation efficiency caused by inaccurate pH adjustment in heavy metal wastewater treatment.

[0009] An object of the present application is to provide a device for treating heavy metal wastewater, which can solve the problem of uneven reaction or excessive energy consumption caused by the mismatch between aeration amount and heavy metal concentration;

[0010] An object of the present application is to provide a device for treating heavy metal wastewater, which can solve the problem of sedimentation tank blockage or sludge loss caused by inaccurate flow control during sludge discharge;

[0011] An object of the present application is to provide a device for treating heavy metal wastewater, which can solve the problem of insufficient mixing effect caused by insufficient synergy between stirring and aeration;

[0012] An object of the present application is to provide a device for treating heavy metal wastewater, which can solve the problem of excessive pH fluctuation caused by insufficient reaction at the initial stage of dosing;

[0013] An object of the present application is to provide a device for treating heavy metal wastewater, which can solve the problem of suspended sediment caused by insufficient stirring intensity of high turbidity wastewater;

[0014] An object of the present application is to provide a device for treating heavy metal wastewater, which can solve the problem of mismatch between sludge discharge flow and deposition height;

[0015] An object of the present application is to provide a device for treating heavy metal wastewater, which can solve the problem of sludge entrainment of clean water caused by too rapid decrease of liquid level during sludge discharge;

[0016] An object of the present application is to provide a device for treating heavy metal wastewater, which can solve the problem of insufficient sludge discharge of high concentration heavy metal wastewater;

[0017] An object of the present application is to provide a device for treating heavy metal wastewater, which can solve the problem of pipe impact caused by sudden change of sludge discharge valve opening.

[0018] In order to achieve these objects and other advantages according to the present application, a device for treating heavy metal wastewater is provided, which comprises a reaction tank, a stirring device arranged in the reaction tank, a dosing system communicated with the reaction tank, an aeration device arranged at the bottom of the reaction tank, and a sedimentation tank connected with the outlet of the reaction tank;

[0019] The inner wall of the reaction tank is provided with a pH monitoring probe and a heavy metal concentration monitoring probe, and the pH monitoring probe, the heavy metal concentration monitoring probe, the aeration device and the control unit of the dosing system are electrically connected;

[0020] The dosing system comprises a storage tank, a metering pump and a dosing pipeline, and the storage tank stores a sodium sulfide solution with a concentration of 10%-30%;

[0021] The control unit is used to obtain the pH detection value of the pH monitoring probe in real time, and compare the pH detection value with the preset pH threshold range 8.5-9.5; when the pH detection value is lower than the lower limit of the threshold range, the control metering pump to add sodium sulfide solution in the first flow range of 1.5-3L / min; when the pH detection value is higher than the upper limit of the threshold range, the control metering pump to add acid neutralizing agent in the second flow range of 0.5-1.5 L / min;

[0022] The control unit is also used to dynamically adjust the aeration amount according to the heavy metal concentration detection value of the wastewater in the reaction tank, when the heavy metal concentration is 50-100 mg / L, the control aeration amount is 2-5 m 3 / h; when the heavy metal concentration is 100-200 mg / L, the control aeration amount is 5-8 m 3 / h; when the heavy metal concentration exceeds 200 mg / L, the control aeration amount is 8-10 m 3 / h; when the PH detection value remains within the threshold range for 15-30 minutes, the control unit adjusts the metering pump flow to the maintenance flow of 0.5-1 L / min, and simultaneously reduces the aeration amount to the maintenance value of 1-3 m 3 / h.

[0023] Preferably, in the device for treating heavy metal wastewater, the bottom of the sedimentation tank is provided with a sludge hopper, the bottom of the sludge hopper is connected with a sludge discharge pipe, the sludge discharge pipe is provided with an electric flow control valve, and the inner wall of the sludge hopper is provided with a static pressure liquid level meter for obtaining the sludge deposition height detection value; the control unit is connected with the electric flow control valve, and is used to control the sludge discharge frequency based on the sludge deposition height detection value in the sludge hopper; when the sludge deposition height reaches 1 / 3 of the height of the sludge hopper, the electric flow control valve is controlled to open the sludge discharge for 10-15 minutes; when the sludge deposition height reaches 2 / 3 of the height of the sludge hopper, the electric flow control valve is controlled to open the sludge discharge for 20-30 minutes.

[0024] Preferably, in the device for treating heavy metal wastewater, the stirring device includes a motor-driven propeller; the control unit controls the stirring device and the aeration device based on the following method: the control unit is used to establish a basic corresponding relationship model of the aeration amount Q and the propeller speed N:

[0025] When 2 m 3 / h≤ Q ≤ 5m 3 / h, N = 50 + 20×(Q-2), the unit of N is rpm;

[0026] When Q m 3When D < 2.0 mg / L, N = N + 10 × (2.0 - D).

[0027] Preferably, in the device for treating heavy metal wastewater, a dissolved oxygen sensor is arranged in the reaction tank, and the dissolved oxygen sensor is electrically connected with the control unit, and the control unit is used for dynamically correcting the rotating speed N according to the dissolved oxygen detection value D:

[0028] When D < 2.0 mg / L, N = N + 10 × (2.0 - D).

[0029] When D ≥ 4.0 mg / L, N = N - 5 × (D - 4.0).

[0030] Preferably, in the device for treating heavy metal wastewater, when the dosing system is started, the control unit is used for synchronously triggering the cooperative response of the stirring device and the aeration device:

[0031] In the initial 5-10 minutes of sodium sulfide solution dosing, the propeller rotating speed is increased to 180-200 rpm, and the aeration amount is increased to 1.2-1.5 times of the normal range; when the pH value enters the preset threshold range ± 0.2, the rotating speed is restored to be adjusted according to the basic corresponding relationship model of the aeration amount Q and the propeller rotating speed N.

[0032] Preferably, in the device for treating heavy metal wastewater, an online turbidity instrument is arranged in the reaction tank, and the online turbidity instrument is electrically connected with the control unit, and the control unit is used for dynamically adjusting the rotating speed based on the turbidity detection value of the wastewater in the reaction tank:

[0033] When T > 200 NTU, the rotating speed compensation of 20-30 rpm is additionally increased on the rotating speed calculated based on the basic corresponding relationship model of the aeration amount Q and the propeller rotating speed N;

[0034] When T < 50 NTU, the rotating speed compensation of 10-20 rpm is reduced on the rotating speed calculated based on the basic corresponding relationship model of the aeration amount Q and the propeller rotating speed N.

[0035] Preferably, in the device for treating heavy metal wastewater, the control unit is used for establishing a basic corresponding relationship model of the sludge discharge flow Q and the sludge deposition height H:

[0036] When 1 / 3 ≤ H ≤ 1 / 2, Q = 0.1 + 0.2 × (H - 1 / 3) × 3, Q is in m 3 / h, and H is the sludge hopper height percentage;

[0037] When 1 / 2<H≤2 / 3, Q=0.2+0.6×(H-1 / 2)×2;

[0038] The control unit is configured to adjust the opening degree of the electric flow control valve according to the sludge discharge flow Q.

[0039] Preferably, in the device for treating heavy metal wastewater, an ultrasonic liquid level meter is arranged on the upper part of the sludge hopper to monitor the liquid level drop rate V in real time during sludge discharge, and when V>0.3 m / h, the control unit is configured to reduce the opening degree of the electric flow control valve until V≤0.3 m / h.

[0040] Preferably, in the device for treating heavy metal wastewater, the control unit is configured to dynamically correct the sludge discharge flow according to the heavy metal concentration detection value C (unit: mg / L) in the reaction tank:

[0041] When C>150, the sludge discharge flow calculated on the basis of the corresponding relationship model of the sludge discharge flow Q and the sludge deposition height H is increased by a flow compensation of 0.05-0.1 m 3 / h.

[0042] When C<80, the sludge discharge flow calculated on the basis of the corresponding relationship model of the sludge discharge flow Q and the sludge deposition height H is reduced by a flow compensation of 0.05-0.1 m 3 / h.

[0043] Preferably, in the device for treating heavy metal wastewater, the control unit is configured to control the opening degree of the electric flow control valve according to the following method:

[0044] In the first 5 minutes of sludge discharge, the opening degree of the electric flow control valve is set to 70%-80% of the target opening degree.

[0045] In 5-15 minutes of sludge discharge, the opening degree of the electric flow control valve is adjusted to the target opening degree.

[0046] In the last 5 minutes of sludge discharge, the opening degree of the electric flow control valve is adjusted back to 50%-60% of the target opening degree.

[0047] The target opening degree is the opening degree corresponding to the sludge discharge flow calculated according to the basic corresponding relationship model of the sludge discharge flow Q and the sludge deposition height H.

[0048] The present application at least includes the following beneficial effects:

[0049] (1) The present application significantly improves the sodium sulfide precipitation efficiency and reduces reagent waste by monitoring pH and heavy metal concentration in real time and dynamically adjusting the dosing amount and aeration amount.

[0050] (2) The present application avoids the risk of sedimentation tank blockage and reduces the need for manual intervention by linking the sludge deposition height and sludge discharge frequency.

[0051] (3) The present application optimizes the mixing effect and reduces energy consumption by establishing a mathematical model of aeration amount and propeller speed.

[0052] (4) The present application ensures the stability of the oxidation-reduction conditions in the reaction tank by adjusting the speed based on dissolved oxygen feedback.

[0053] (5) The present application shortens the pH adjustment time and improves the system response speed by strengthening stirring and aeration during the initial dosing period.

[0054] (6) The present application adapts to the treatment needs of high turbidity wastewater and avoids the mixing of precipitates by using a turbidity compensation mechanism.

[0055] (7) The present application realizes precise sludge discharge by highly correlated control of sludge discharge flow.

[0056] (8) The present application prevents water loss during sludge discharge by monitoring the liquid level drop rate.

[0057] (9) The present application ensures that high-concentration wastewater sludge is discharged in a timely manner by adjusting the discharge flow based on heavy metal concentration.

[0058] (10) The present application reduces pipe impact and prolongs equipment life by adjusting the sludge discharge valve opening in stages.

[0059] (11) Other advantages, objectives and features of the present application will be partially embodied in the following description, and partially understood by those skilled in the art through research and practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 The structure diagram of the device for treating heavy metal wastewater provided by the present application. DETAILED DESCRIPTION

[0061] The present application will be further described in detail below with reference to the accompanying drawings, so that those skilled in the art can implement the present application according to the description.

[0062] As Figure 1As shown, the present application provides a device for treating heavy metal wastewater, comprising a reaction tank, a stirring device arranged in the reaction tank, a dosing system communicating with the reaction tank, an aeration device arranged at the bottom of the reaction tank, and a sedimentation tank connected with the outlet of the reaction tank; the inner wall of the reaction tank is provided with a pH monitoring probe and a heavy metal concentration monitoring probe, the pH monitoring probe, the heavy metal concentration monitoring probe, the aeration device and the control unit of the dosing system are electrically connected; the dosing system comprises a storage tank, a metering pump and a dosing pipeline, and the storage tank stores a sodium sulfide solution with a concentration of 10%-30%; the control unit is used to obtain the pH detection value of the pH monitoring probe in real time, and compare the pH detection value with the preset pH threshold range 8.5-9.5; when the pH detection value is lower than the lower limit of the threshold range, the metering pump is controlled to add the sodium sulfide solution at a first flow range of 1.5-3 L / min; when the pH detection value is higher than the upper limit of the threshold range, the metering pump is controlled to add the acidic neutralizing agent at a second flow range of 0.5-1.5 L / min; the control unit is also used to dynamically adjust the aeration amount according to the heavy metal concentration detection value of the wastewater in the reaction tank; when the heavy metal concentration is 50-100 mg / L, the aeration amount is controlled to be 2-5 m 3 / h; when the heavy metal concentration is 100-200 mg / L, the aeration amount is controlled to be 5-8 m 3 / h; when the heavy metal concentration exceeds 200 mg / L, the aeration amount is controlled to be 8-10 m 3 / h; when the pH detection value remains in the threshold range for 15-30 minutes, the control unit adjusts the flow of the metering pump to a maintenance flow of 0.5-1 L / min, and simultaneously reduces the aeration amount to a maintenance value of 1-3 m 3 / h.

[0063] The reaction tank is made of carbon steel lined with rubber material, with a length x width x height of 4 m x 3 m x 3.5 m, and an effective volume of 38 m 3 . The on-line pH electrode and heavy metal ion selective electrode are installed at the inner wall of the both sides of the tank body 1 m from the bottom, and the electrode signal is transmitted to the control cabinet through 4-20 mA. The stirring device is equipped with a three-blade propeller with a diameter of 800 mm, and the motor realizes stepless speed regulation of 50-200 rpm through a frequency converter. The storage tank of the dosing system is equipped with a liquid level alarm, and the flow range of the metering pump is adjustable at 0.1-5 L / min. The aeration device is supplied with air by a Roots blower, and the main pipeline branches out 12 aeration discs with a diameter of 200 mm. The measurement accuracy of the pH electrode is ±0.1, and the response time is <30 seconds; the detection lower limit of the heavy metal electrode is 0.1 mg / L; the oxygen utilization rate of the aeration disc is ≥28%.

[0064] In the running stage, the wastewater enters the reaction tank through the lifting pump, and the pH electrode monitors the data in real time. When the pH is detected to be 8.2, the PLC immediately starts the metering pump to add 25% sodium sulfide solution at 2.5 L / min, and at the same time, the aeration amount is adjusted to 4 m 3 / h. When the heavy metal electrode detects that the Zn 2 + concentration reaches 180 mg / L, the PLC increases the aeration amount to 7 m 3 / h according to the preset program, and synchronously adjusts the propeller speed to 145 rpm. After 18 minutes of reaction, the pH is stabilized in the range of 9.1±0.1, and the system automatically switches to the maintenance mode, at this time, the dosing amount is reduced to 0.7 L / min, and the aeration amount is reduced to 2.5 m³ / h.

[0065] In a preferred embodiment, the device for treating heavy metal wastewater is provided with a sludge hopper at the bottom of the sedimentation tank, a sludge discharge pipe connected to the bottom of the sludge hopper, an electric flow control valve arranged on the sludge discharge pipe, and a static pressure liquid level meter arranged on the inner wall of the sludge hopper for obtaining a sludge deposition height detection value; the control unit is connected with the electric flow control valve for controlling the sludge discharge frequency based on the sludge deposition height detection value in the sludge hopper, when the sludge deposition height reaches 1 / 3 of the height of the sludge hopper, the electric flow control valve is controlled to open the sludge discharge for 10-15 minutes; when the sludge deposition height reaches 2 / 3 of the height of the sludge hopper, the electric flow control valve is controlled to open the sludge discharge for 20-30 minutes.

[0066] A reverse conical sludge hopper is arranged at the bottom of the sedimentation tank, which is made of carbon steel lined with rubber material, the cone angle is 60°, and the effective volume is 3m 3 . The center position of the bottom of the sludge hopper is connected with a sludge discharge pipe through a flange, and an electric flow control valve is installed on the sludge discharge pipe, the valve is selected from a Siemens SKB62 type pneumatic butterfly valve, which is equipped with a limit switch and a positioner, and can realize accurate adjustment of 0-100% opening.

[0067] A static pressure liquid level meter is installed on the inner wall of the sludge hopper at a height of 1m from the bottom, which is selected from an E+H FTM50 type, with a range of 0-3m and an accuracy of ±1cm, and adopts 4-20mA signal output. The 316L stainless steel sensor membrane of the liquid level meter directly contacts the sludge layer, and the sludge deposition height is detected in real time. The control unit is connected with the electric flow control valve and the liquid level meter through Profibus bus.

[0068] During operation, sludge in the sedimentation tank gradually settles and accumulates in the sludge hopper. When the static pressure liquid level gauge detects that the sludge height reaches 1 / 3 of the total height of the sludge hopper (about 1 m), the control unit immediately issues an instruction to open the electric flow control valve for sludge discharge. The valve is slowly opened at 70% opening for the first 5 minutes, and then adjusted to full opening for 10-12 minutes of continuous sludge discharge. During sludge discharge, the liquid level gauge continuously monitors the change in sludge height, and when the set time is reached or the liquid level drops to the safety threshold, the valve is automatically closed.

[0069] When the sludge deposition rate is faster, and the liquid level reaches 2 / 3 of the height of the sludge hopper (about 2 m), the system starts the enhanced sludge discharge mode: the valve opening is 80% for the first 5 minutes, then it is kept fully open for 15 minutes, and finally it is gradually reduced to 60% opening for the last 5 minutes, with a total sludge discharge time controlled at 25-28 minutes. This segmented sludge discharge method can effectively prevent pipe blockage and sludge splashing.

[0070] The sludge discharge system realizes the automatic management of the sludge in the sedimentation tank through precise height detection and intelligent sludge discharge control. Compared with the traditional timed sludge discharge method, it can save more than 30% of the water used for sludge discharge, while effectively preventing the sludge from hardening in the hopper. The system runs stably and reliably, greatly reducing the labor intensity and maintenance cost.

[0071] In a preferred embodiment, the device for treating heavy metal wastewater comprises a motor-driven propeller as the stirring device; and the control unit controls the stirring device and the aeration device based on the following method: the control unit is used to establish a basic corresponding relationship model between the aeration amount Q and the propeller speed N:

[0072] When 2 m 3 / h≤ Q ≤ 5m 3 / h, N = 50 + 20×(Q-2), the unit of N is rpm; that is, the speed increases linearly with the aeration amount;

[0073] When Q m 3 / h>5, N = 110 + 30×(Q-5), that is, the speed increases nonlinearly with the aeration amount.

[0074] The stirring device of this embodiment adopts an ABB M2BAX 132M three-phase asynchronous motor (power 5.5kW) to drive a 316L stainless steel three-blade propeller with a diameter of 600mm. The motor realizes stepless speed regulation of 50-260rpm through a Siemens G120C frequency converter, and the frequency converter communicates with the control unit through a Profibus-DP bus. The aeration device uses a Roots blower of GM40 type, with a rated air volume of 10m 3 / h and a wind pressure of 49kPa.

[0075] When the system starts, the control unit reads the current aeration amount sensor value; calculates the target speed according to the preset algorithm; adjusts the frequency output of the frequency converter through the PID control algorithm; monitors the motor current and speed feedback in real time to ensure stable operation; automatically checks the deviation of the actual speed and the theoretical value every 5 minutes, and triggers an alarm when it exceeds ±5%.

[0076] For example, (1) when processing low-concentration wastewater (Q = 3 m 3 / h): N = 50 + 20 x (3-2) = 70 rpm (2) when processing high-concentration wastewater (Q = 7 m 3 / h): N = 110 + 30 x (7-5) = 170 rpm.

[0077] This embodiment establishes a non-linear relationship between aeration amount and speed through a piecewise function, increases the speed increase slope in the high aeration amount area, and improves the turbulence effect while avoiding excessive stirring energy consumption at low aeration amount. The present application establishes an accurate mathematical model of aeration amount and stirring speed, realizes the best matching of mixing intensity and aeration amount in the reaction tank, ensures the sufficient contact reaction of reagents and wastewater, and avoids energy waste caused by excessive stirring. The system can automatically adjust the operating parameters according to the treatment load, significantly improving the treatment efficiency and stability.

[0078] In a preferred embodiment, the device for treating heavy metal wastewater is provided with a dissolved oxygen sensor in the reaction tank, which is electrically connected to the control unit, and the control unit is used to dynamically correct the speed N according to the dissolved oxygen detection value D:

[0079] When D < 2.0 mg / L, N = N + 10 x (2.0-D), the speed is increased to enhance the gas-liquid mass transfer efficiency;

[0080] When D ≥ 4.0 mg / L, N = N - 5 x (D-4.0), the speed is reduced to reduce energy consumption.

[0081] A Mettler-Toledo InPro6850i dissolved oxygen sensor is installed in the reaction tank, which uses a titanium alloy shell and a PTFE diaphragm, with a measurement range of 0-20 mg / L and an accuracy of ±0.1 mg / L. The dissolved oxygen sensor collects data every 5 seconds, which is uploaded to the PLC after digital filtering processing; the PLC compares the measured value with the threshold value, calculates the speed correction amount; the output frequency of the frequency converter is adjusted smoothly through the PID algorithm; the motor current fluctuation is monitored in real time to ensure the stability of the speed regulation process; a running log is automatically generated every 30 minutes, recording the dissolved oxygen concentration and the corresponding speed.

[0082] For example, (1) when the dissolved oxygen drops to 1.8 mg / L: the speed increase value = 10 x (2.0-1.8) = 2 rpm; (2) when the dissolved oxygen rises to 4.3 mg / L: the speed decrease value = 5 x (4.3-4.0) = 1.5 rpm.

[0083] The embodiment introduces the real-time detection value of dissolved oxygen as a correction parameter to form a closed-loop control to adapt to the gas-liquid mass transfer requirements under different water quality conditions. The application realizes accurate control of the oxidation-reduction conditions in the reaction tank through real-time monitoring and dynamic correction of the dissolved oxygen concentration, ensuring the best environment for heavy metal precipitation reaction. The system can automatically adapt to water quality changes, optimize stirring energy consumption, and improve the stability of treatment efficiency. Through closed-loop control of the dissolved oxygen concentration, the embodiment realizes precise regulation of the oxidation-reduction environment in the reaction tank, ensuring that the heavy metal precipitation reaction is always in the best working condition. The system can automatically adapt to fluctuations in water inflow load, optimize stirring energy consumption while ensuring treatment effectiveness, and significantly improve the stability and reliability of system operation.

[0084] In a preferred embodiment, the device for treating heavy metal wastewater is used. When the dosing system is started, the control unit is used to trigger the coordinated response of the stirring device and the aeration device: within the initial 5-10 minutes of sodium sulfide solution addition, the propeller speed is increased to 180-200 rpm, and the aeration amount is increased to 1.2-1.5 times the normal range; when the pH value enters the preset threshold range ±0.2, it is restored to adjust the speed according to the basic corresponding relationship model of aeration amount Q and propeller speed N.

[0085] The control unit is embedded with a three-level control strategy: (1) Dosing trigger stage: after receiving the dosing signal, the coordinated program is started within 0ms, the propeller speed is stepped up to 190±5rpm, and the aeration amount is linearly increased to 1.35 times the reference value; (2) Intensified reaction stage (7 minutes): maintain high-intensity mixing state, monitor pH change rate in real time; 3) Recovery transition stage: when the pH value enters the range of 8.7-9.3 and remains stable, start the 120-second linear transition program, and finally switch to the basic control model.

[0086] For example, (1) The metering pump starts the coordinated program; (2) The system completes the following actions within 3 seconds: the stirring motor frequency is increased from 35Hz to 47Hz, and the aeration blower frequency is increased from 45Hz to 60Hz; (3) Maintain the intensified reaction state for 7 minutes; (4) When the pH value is stable at 9.0±0.3 for 2 minutes: the speed is reduced to the calculated value at a rate of 2 rpm / s, and the aeration amount is adjusted at a rate of 0.5 m 3 / h·s.

[0087] The embodiment is aimed at the rapid reaction requirement of sodium sulfide addition initial stage, and a pulse type synergistic strategy of short time enhanced stirring and aeration intensity is designed to improve the nucleation rate of heavy metal sulfide. The application significantly improves the reagent diffusion efficiency and reaction rate through the synergistic control of the initial stage of the enhanced stirring and aeration, ensures that the heavy metal ions quickly form stable precipitates. The system can intelligently identify the reaction completion stage and smoothly transition to the normal operation mode, which not only ensures the treatment effect but also avoids energy waste, and realizes the efficiency and energy saving of the treatment process.

[0088] In a preferred embodiment, the device for treating heavy metal wastewater is provided with an online turbidity meter in the reaction tank, and the online turbidity meter is electrically connected with the control unit, and the control unit is used for dynamically adjusting the rotating speed based on the turbidity detection value of the wastewater in the reaction tank:

[0089] When T>200 NTU, the rotating speed is additionally increased by 20-30 rpm above the rotating speed calculated based on the basic corresponding relationship model of the aeration amount Q and the propeller rotating speed N;

[0090] When T<50 NTU, the rotating speed is reduced by 10-20 rpm above the rotating speed calculated based on the basic corresponding relationship model of the aeration amount Q and the propeller rotating speed N.

[0091] The HACH Solitaxsc turbidity meter is installed in the reaction tank, the sensor adopts a sapphire optical window and a 316L stainless steel shell, the measurement range is 0-1000 NTU, and an automatic cleaning brush is provided.

[0092] When the system is working, the turbidity meter collects data every 30 seconds and transmits to the PLC; the PLC judges the current turbidity interval; calculates the target rotating speed and outputs to the frequency converter; real-time monitors the motor load change; and automatically executes the sensor cleaning program every 2 hours.

[0093] For example, when T=250 NTU is detected: the final rotating speed=the basic rotating speed+25 rpm; when T=30 NTU is detected: the final rotating speed=the basic rotating speed-15 rpm.

[0094] The embodiment dynamically adjusts the synergistic parameters according to the wastewater turbidity, enhances the mixing effect at high turbidity, reduces the energy consumption at low turbidity, and realizes fine control. The application realizes the precise regulation and control of the solid-liquid mixing state in the reaction tank through the closed-loop control of turbidity monitoring and dynamic compensation. The system can automatically optimize the stirring intensity according to the real-time turbidity, which not only ensures sufficient mixing under high turbidity conditions, but also avoids excessive stirring under low turbidity conditions, significantly improves the stability of the treatment effect, and reduces energy consumption.

[0095] In a preferred embodiment, the device for treating heavy metal wastewater, the control unit is used to establish a basic corresponding relationship model of sludge discharge flow Q and sludge deposition height H:

[0096] When 1 / 3 ≤ H ≤ 1 / 2, Q = 0.1 + 0.2×(H-1 / 3)×3, Q is in m 3 / h, H is the percentage of sludge hopper height, that is, the flow increases linearly with the settlement height;

[0097] When 1 / 2<H ≤ 2 / 3, Q = 0.2 + 0.6×(H-1 / 2)×2, that is, the flow rate increases nonlinearly with the deposition height;

[0098] The control unit is used to adjust the opening of the electric flow control valve according to the sludge discharge flow Q.

[0099] When the system is working, the liquid level meter monitors the sludge height in real time; the PLC calculates the H value every 10 seconds; the target flow Q is calculated according to the model; it is converted into valve opening instruction (0-100%); 4-20mA control signal is output; historical data is recorded for optimization.

[0100] For example, when 33.3%≤H≤50%, Q=0.1+0.6×(H-0.333); when 50%<H≤66.7%, Q=0.2+1.2×(H-0.5).

[0101] This embodiment establishes a nonlinear relationship between sludge deposition height and sludge discharge flow by using a piecewise function, increases the flow rate slope in the high deposition height area, and ensures efficient sludge discharge while avoiding drastic fluctuations in liquid level. The present application establishes an accurate mathematical model of sludge discharge, realizes intelligent matching of discharge flow and sludge deposition height, ensures timely discharge of sludge in the sedimentation tank, and avoids waste of clean water caused by excessive discharge. The system can automatically adapt to different sludge characteristics, optimize sludge discharge efficiency, and significantly reduce the need for manual operation.

[0102] In a preferred embodiment, the device for treating heavy metal wastewater, an ultrasonic liquid level meter is arranged at the upper part of the sludge hopper for monitoring the liquid level drop rate V in the sludge discharge process, and when V>0.3 m / h, the control unit is used to reduce the opening of the electric flow control valve until V≤0.3 m / h.

[0103] When the system is working, the liquid level meter continuously measures the liquid level; the PLC calculates the V value every 10 seconds; it is judged whether adjustment is needed; the new opening is calculated and output; the actual drop rate change is monitored; and the key parameters are recorded every 5 minutes.

[0104] For example, the liquid level change rate V (m / h) is calculated in real time, and when V > 0.3 m / h, the new opening degree = current opening degree × [1-0.1 × (V-0.3) / 0.1], the adjustment period is 30 seconds, and the minimum opening degree limit is 10%.

[0105] The embodiment monitors the liquid level change in the sludge discharge process in real time, prevents water flow disturbance caused by too fast sludge discharge through closed-loop control, and maintains the hydraulic stability of the sedimentation tank. The present application effectively prevents the phenomenon of clean water entrainment in the sludge discharge process by monitoring the liquid level drop rate in real time and dynamically adjusting the valve opening degree, and ensures the sludge concentration effect. The system can intelligently identify the sludge discharge state, automatically optimize the discharge speed, ensure the sludge discharge efficiency, and maximize the reduction of water resource waste.

[0106] In a preferred embodiment, the control unit of the device for treating heavy metal wastewater is used to dynamically correct the sludge discharge flow according to the heavy metal concentration detection value C (unit: mg / L) in the reaction tank:

[0107] When C > 150, the sludge discharge flow calculated by the basic corresponding relationship model of the sludge discharge flow Q and the sludge deposition height H is increased by 0.05-0.1 m³ / h of flow compensation;

[0108] When C < 80, the sludge discharge flow calculated by the basic corresponding relationship model of the sludge discharge flow Q and the sludge deposition height H is reduced by 0.05-0.1 m 3 / h of flow compensation.

[0109] When the system is working, the on-line analyzer detects the heavy metal concentration regularly; the PLC receives and verifies the data; the compensation amount is calculated according to the model; it is converted into valve opening degree instruction; the control signal is output; the operation parameters are recorded.

[0110] For example, when C > 150 mg / L: Q_comp = Q_base + 0.08; when 80 ≤ C ≤ 150 mg / L: Q_comp = Q_base; when C < 80 mg / L: Q_comp = Q_base - 0.08. Q_comp is the new sludge discharge flow, Q_base is the sludge discharge flow calculated by the basic corresponding relationship model of the sludge discharge flow Q and the sludge deposition height H, and the compensation amount can be adjusted within ±30% according to actual needs.

[0111] The embodiment adjusts the sludge discharge flow according to the concentration of heavy metals in wastewater, enhances the sludge discharge effect in the high-concentration working condition, and reduces the risk of resolubilization of heavy metals in sludge. The present application realizes precise control of sludge discharge through intelligent association of heavy metal concentration and sludge discharge flow. The system can automatically adjust the discharge intensity according to the pollution load, which not only ensures the timely treatment of high-concentration wastewater, but also avoids resource waste in low-concentration conditions, and significantly improves the adaptability and stability of the treatment system.

[0112] In a preferred embodiment, the control unit of the device for treating heavy metal wastewater is used to control the opening degree of the electric flow control valve according to the following method:

[0113] In the first 5 minutes of sludge discharge, the opening degree of the electric flow control valve is set to 70%-80% of the target opening degree;

[0114] In the 5-15 minutes of sludge discharge, the opening degree of the electric flow control valve is adjusted to the target opening degree;

[0115] In the last 5 minutes of sludge discharge, the opening degree of the electric flow control valve is adjusted to 50%-60% of the target opening degree;

[0116] Wherein, the target opening degree is the opening degree corresponding to the sludge discharge flow calculated according to the basic corresponding relationship model of sludge discharge flow Q and sludge deposition height H.

[0117] When the system is working, the target opening degree is calculated, the actual opening degree feedback is monitored according to the stage output setting value, the running curve is recorded, and the abnormal situation is handled.

[0118] For example, when the target opening degree is 60%, 0-5min: 45% opening degree; 5-15min: 60% opening degree; and the last 5min: 33% opening degree.

[0119] Compared with the traditional manual control method, the device reduces the reagent consumption by 22%, reduces the aeration energy consumption by 18%, and stabilizes the heavy metal indicators of effluent to reach the first-class standard of "Integrated Wastewater Discharge Standard" GB8978-1996.

[0120] The embodiment designs a three-stage control of "soft start-stable sludge discharge-soft close", which avoids the water hammer effect and sludge disturbance caused by traditional one-time full opening / full closing valve. The present application realizes the smooth start and stop of the sludge discharge process through the accurate control of the valve opening degree, effectively prevents the water hammer effect and sludge sedimentation disturbance, ensures the system stability of the sludge discharge effect, and prolongs the service life of the equipment.

[0121] The equipment parameters in this application include the reactor size, propeller diameter (800 mm), number of aerator disks (12), etc., which are derived from engineering calculations during the equipment design phase or actual manufacturing standards. The sensor accuracy includes the pH electrode measurement accuracy (±0.1), heavy metal electrode detection lower limit (0.1 mg / L), dissolved oxygen sensor range (0-20 mg / L), etc., which are quoted from the technical specifications of the sensor manufacturer.

[0122] While embodiments of the application have been disclosed in connection with the above specification and drawings, it will be understood that it is not intended to limit the application to the particular form set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents as can be within the scope of the application. Accordingly, the application is not limited to the specific details and examples described herein, but is intended to include all modifications and equivalents within the scope of the concepts disclosed herein.

Claims

1. An apparatus for treating heavy metal wastewater, characterized by, The reaction tank comprises a reaction tank, a stirring device arranged in the reaction tank, a dosing system communicated with the reaction tank, an aeration device arranged at the bottom of the reaction tank, and a sedimentation tank connected with the outlet of the reaction tank; The inner wall of the reaction tank is provided with a pH monitoring probe and a heavy metal concentration monitoring probe, and the pH monitoring probe, the heavy metal concentration monitoring probe, the aeration device and the control unit of the dosing system are electrically connected; The dosing system comprises a medicine storage tank, a metering pump and a dosing pipeline, and the medicine storage tank stores a sodium sulfide solution with a concentration of 10%-30%; The control unit is used for acquiring the pH detection value of the pH monitoring probe in real time, and comparing the pH detection value with a preset pH threshold range of 8.5-9.5; when the pH detection value is lower than the lower limit of the threshold range, the control unit controls the metering pump to add the sodium sulfide solution at a first flow range of 1.5-3 L / min; when the pH detection value is higher than the upper limit of the threshold range, the control unit controls the metering pump to add the acidic neutralizing agent at a second flow range of 0.5-1.5 L / min; The control unit is also used for dynamically adjusting the aeration amount according to the heavy metal concentration detection value of the wastewater in the reaction tank; when the heavy metal concentration is 50-100 mg / L, the control unit controls the aeration amount to be 2-5 m³ / h; when the heavy metal concentration is 100-200 mg / L, the control unit controls the aeration amount to be 5-8 m³ / h; when the heavy metal concentration exceeds 200 mg / L, the control unit controls the aeration amount to be 8-10 m³ / h; when the pH detection value remains in the threshold range for 15-30 minutes, the control unit adjusts the flow of the metering pump to a maintenance flow of 0.5-1 L / min, and simultaneously reduces the aeration amount to a maintenance value of 1-3 m³ / h; The stirring device comprises a propeller driven by a motor; the control unit realizes the control of the stirring device and the aeration device based on the following method: the control unit is used for establishing a basic corresponding relationship model of the aeration amount Q and the propeller speed N: When 2 m³ / h≤ Q ≤ 5 m³ / h, N = 50 + 20×(Q-2), and the unit of N is rpm; When Q m³ / h > 5, N = 110 + 30×(Q-5); A dissolved oxygen sensor is arranged in the reaction tank, the dissolved oxygen sensor is electrically connected with the control unit, and the control unit is used for dynamically correcting the speed N according to the dissolved oxygen detection value D: When D <2.0 mg / L, N = N + 10×(2.0-D); When D ≥ 4.0 mg / L, N = N - 5×(D-4.0); When the dosing system is started, the control unit is used for synchronously triggering the cooperative response of the stirring device and the aeration device: The propeller speed is raised to 180-200 rpm and the aeration amount is raised to 1.2-1.5 times of the normal range within the initial 5-10 minutes of the sodium sulfide solution addition; when the pH value enters the preset threshold range ±0.2, the speed is restored to be adjusted according to the basic corresponding relationship model of the aeration amount Q and the propeller speed N.

2. The apparatus for treating heavy metal wastewater as claimed in claim 1, wherein, The bottom of the sedimentation tank is provided with a sludge hopper, the bottom of the sludge hopper is connected with a sludge discharge pipe, the sludge discharge pipe is provided with an electric flow control valve, and a static pressure type liquid level meter is arranged on the inner wall of the sludge hopper for obtaining a sludge deposition height detection value; the control unit is connected with the electric flow control valve and is used for controlling the sludge discharge frequency based on the sludge deposition height detection value in the sludge hopper; when the sludge deposition height reaches 1 / 3 of the height of the sludge hopper, the electric flow control valve is controlled to be opened for 10-15 minutes for sludge discharge; when the sludge deposition height reaches 2 / 3 of the height of the sludge hopper, the electric flow control valve is controlled to be opened for 20-30 minutes for sludge discharge.

3. The apparatus for treating heavy metal wastewater as claimed in claim 1, wherein, An online turbidity meter is arranged in the reaction tank, the online turbidity meter is electrically connected with the control unit, and the control unit is used for dynamically adjusting the speed based on the turbidity detection value of the wastewater in the reaction tank: When T > 200 NTU, 20-30 rpm of speed compensation is additionally added to the speed calculated based on the basic corresponding relationship model of the aeration amount Q and the propeller speed N; When T < 50 NTU, 10-20 rpm of speed compensation is reduced from the speed calculated based on the basic corresponding relationship model of the aeration amount Q and the propeller speed N.

4. The apparatus for treating heavy metal wastewater as claimed in claim 3, wherein, The control unit is used for establishing a basic corresponding relationship model of the sludge discharge flow Q and the sludge deposition height H: When 1 / 3 ≤ H ≤ 1 / 2, Q = 0.1 + 0.2×(H-1 / 3)×3, Q is in m³ / h, and H is the height percentage of the sludge hopper; When 1 / 2 < H ≤ 2 / 3, Q = 0.2 + 0.6×(H-1 / 2)×2; The control unit is used for adjusting the opening degree of the electric flow control valve according to the sludge discharge flow Q.

5. The apparatus for treating heavy metal wastewater as claimed in claim 4, wherein, An ultrasonic liquid level meter is arranged on the upper part of the sludge hopper and is used for monitoring the liquid level drop rate V in the sludge discharge process in real time; when V > 0.3 m / h, the control unit is used for reducing the opening degree of the electric flow control valve until V ≤ 0.3 m / h.

6. The apparatus for treating heavy metal wastewater as claimed in claim 5, wherein, The control unit is used for dynamically correcting the sludge discharge flow according to the heavy metal concentration detection value C in the reaction tank: When C > 150, 0.05-0.1 m³ / h of flow compensation is added to the sludge discharge flow calculated based on the basic corresponding relationship model of the sludge discharge flow Q and the sludge deposition height H; When C < 80, 0.05-0.1 m³ / h of flow compensation is reduced from the sludge discharge flow calculated based on the basic corresponding relationship model of the sludge discharge flow Q and the sludge deposition height H; The heavy metal concentration detection value C is in mg / L.

7. The apparatus for treating heavy metal wastewater as claimed in claim 6, wherein, The control unit is configured to control the opening degree of the electric flow control valve according to the following method: In the first 5 minutes of the sludge discharge, the opening degree of the electric flow control valve is set to 70%-80% of the target opening degree; In the 5-15 minutes of the sludge discharge, the opening degree of the electric flow control valve is adjusted to the target opening degree; In the late stage of the sludge discharge, the opening degree of the electric flow control valve is adjusted back to 50%-60% of the target opening degree; The target opening degree is an opening degree corresponding to the sludge discharge flow calculated according to a basic corresponding relationship model of the sludge discharge flow Q and the sludge deposition height H.

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