Intelligent dosing system and method for hardness and alkali removal wastewater

Abstract

The invention belongs to the technical field of wastewater treatment, and particularly relates to an intelligent dosing system and method for hardness and alkali removal wastewater. The monitoring unit is used for monitoring calcium hardness, magnesium hardness and alkalinity of inlet water and outlet water and monitoring the pH value in a reaction tank 1; the control system is in communication connection with the monitoring unit, receives the monitoring data, and is used for selecting a dosing mode according to the calcium hardness, magnesium hardness and alkalinity data of the inlet water, calculating the dosing amount and feeding back and adjusting the dosing and pH value according to the monitoring data of the outlet water; the chemical adding unit comprises a lime chemical adding device, a sodium hydroxide chemical adding device and a sodium carbonate chemical adding device which are respectively connected with the control system, and corresponding chemicals are added according to instructions of the control system; the treatment unit sequentially comprises a coagulation tank, a reaction tank 1, a reaction tank 2, a flocculation tank and a sedimentation tank. According to the invention, through automatic intelligent dosing, the purpose of removing alkalinity and hardness in water at the lowest cost is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wastewater treatment, and particularly relates to an intelligent dosing system and method for removing hardness and alkali from wastewater. BACKGROUND

[0002] In the field of drinking water and industrial water, hardness is a key water quality index. High hardness can cause many problems in the process of municipal water and industrial water, and even kidney disease in human body is also believed to be related to high hardness in water. Therefore, it is necessary to remove hardness from high-hardness water. Wastewater containing hardness is divided into negative hardness water and permanent hardness water, and hardness ions are divided into calcium hardness ions and magnesium hardness ions. Different types of wastewater require the addition of different hardness removal agents and the control of different reaction pH values.

[0003] At the same time, as an index for measuring the proton absorption capacity of water, high-alkalinity wastewater has significant hazards: on the one hand, strong corrosion can erode drainage pipelines and sewage treatment facilities, increasing equipment operation and maintenance costs; on the other hand, it can inhibit the activity of nitrifying bacteria and interfere with the nitrification in the biochemical treatment section, reducing the sewage treatment effect.

[0004] However, the existing hardness removal technology has limitations, such as poor adaptability to different types of wastewater, reliance on manual experience for reagent addition and pH value control, and difficulty in precise coordination, resulting in high treatment cost and unstable effect. Therefore, it is an urgent need to develop a technology that can intelligently adapt to various types of hardness wastewater, dynamically regulate and control automatic dosing and reaction conditions through water quality detection, and achieve efficient removal of alkalinity and hardness at the lowest cost, to solve the problem of high-hardness and high-alkalinity wastewater treatment.

[0005] In view of this, the present application is proposed. SUMMARY

[0006] The purpose of the present application is to provide an intelligent dosing system and method for removing hardness and alkali from wastewater. The intelligent dosing system detects the calcium hardness, magnesium hardness and alkalinity of the influent, selects the operating mode, detects the calcium hardness, magnesium hardness and alkalinity of the effluent, and adjusts the dosage based on feedback, to automatically and intelligently dose, achieving the purpose of removing alkalinity and hardness from water at the lowest cost.

[0007] To achieve the above purpose, the present application provides the following technical solutions:

[0008] An intelligent dosing system for removing hardness and alkali from wastewater, comprising:

[0009] A monitoring unit for monitoring the calcium hardness, magnesium hardness and alkalinity of the influent and effluent, and for monitoring the pH value in the reaction tank 1;

[0010] The control system is in communication connection with the monitoring unit, receives monitoring data, is used for selecting dosing mode according to the calcium hardness, magnesium hardness, alkalinity data of inlet water, calculating the dosing amount, and adjusting the dosing and pH value according to the outlet monitoring data feedback;

[0011] The dosing unit comprises a lime dosing device, a sodium hydroxide dosing device and a sodium carbonate dosing device, and is connected with the control system respectively, and the corresponding reagent is added according to the instruction of the control system.

[0012] The processing unit comprises a coagulation tank, a reaction tank 1, a reaction tank 2, a flocculation tank and a sedimentation tank in sequence; the reaction tank 1 is connected with the lime dosing device and the sodium hydroxide dosing device, and the reaction tank 2 is connected with the sodium carbonate dosing device.

[0013] Further, the control system is built-in with a dosing mode judgment logic; according to the inlet water alkalinity m(alkalinity) and calcium hardness m(calcium hardness), the following three modes are judged:

[0014] When 2 x m(alkalinity) > m(calcium hardness), the lime + sodium hydroxide adding mode is selected;

[0015] When 2 x m(alkalinity) ≈ m(calcium hardness), the sodium hydroxide adding mode is selected;

[0016] When 2 x m(alkalinity) < m(calcium hardness), the sodium hydroxide + sodium carbonate adding mode is selected.

[0017] Further, the control system is built-in with a dosing amount calculation model:

[0018] In the lime + sodium hydroxide adding mode, the lime adding amount m(lime) = [2 x m(alkalinity) - m(calcium hardness)] x 0.74;

[0019] In the sodium hydroxide + sodium carbonate adding mode, the sodium carbonate adding amount m(sodium carbonate) = [m(calcium hardness) - 2 x m(alkalinity)] x 1.06.

[0020] In addition, the application also provides an intelligent dosing method for hard and alkali removal wastewater by using the above-mentioned intelligent dosing system, comprising the following steps:

[0021] S1, a monitoring step: the calcium hardness, magnesium hardness and alkalinity of inlet water and outlet water, and the pH value of the reaction tank 1 are monitored in real time through the monitoring unit, and the data are transmitted to the control system;

[0022] S2, mode selection and calculation step: the control system calculates the theoretical adding amount of the corresponding reagent by using the dosing amount calculation model through the built-in dosing mode judgment logic;

[0023] S3, dosing reaction step: the dosing unit adds lime and / or sodium hydroxide to the reaction tank 1 and sodium carbonate to the reaction tank 2 according to the control system instruction, and the wastewater completes the hardness removal and alkali removal reaction in turn through the coagulation tank, the reaction tank 1, the reaction tank 2, the flocculation tank and the sedimentation tank;

[0024] S4, feedback adjustment step: the control system adjusts the dosing and pH value according to the effluent monitoring data, so that the effluent meets the requirements of calcium hardness < 70 mg / L, magnesium hardness < 70 mg / L and alkalinity < 100 mg / L.

[0025] Further, the residence time of the wastewater in the reaction tank 1 is 6-8 min, and the residence time of the wastewater in the reaction tank 2 is 10-12 min.

[0026] Further, in the lime + sodium hydroxide dosing mode, the influent alkalinity and calcium hardness are detected, the theoretical lime dosing amount is calculated, and sodium hydroxide is added to adjust the pH value in the reaction tank 1 to 10.3-10.5; the magnesium hardness of the effluent and the alkalinity of the effluent are fed back and adjusted; if the magnesium hardness of the effluent exceeds the standard, the sodium hydroxide dosing amount is increased; if the alkalinity of the effluent exceeds the standard, the lime dosing amount is increased.

[0027] Further, in the sodium hydroxide dosing mode, sodium hydroxide is added to adjust the pH value in the reaction tank 1 to 10.3-10.5; the magnesium hardness of the effluent, the alkalinity of the effluent and the calcium hardness are fed back and adjusted; if the magnesium hardness of the effluent exceeds the standard, the sodium hydroxide dosing amount is increased; if the alkalinity of the effluent and the calcium hardness exceed the standard, the sodium hydroxide dosing amount is increased.

[0028] Further, in the sodium hydroxide + sodium carbonate dosing mode, the influent alkalinity and calcium hardness are detected, the theoretical sodium carbonate dosing amount is calculated, and sodium hydroxide is added to adjust the pH value in the reaction tank 1 to 10.3-10.5; the magnesium hardness of the effluent and the calcium hardness of the effluent are fed back and adjusted; if the magnesium hardness of the effluent exceeds the standard, the sodium hydroxide dosing amount is increased; if the calcium hardness of the effluent exceeds the standard, the sodium carbonate dosing amount is increased.

[0029] Further, in the lime + sodium hydroxide dosing mode and the sodium hydroxide + sodium carbonate dosing mode, the control system preferentially meets the treatment requirement of the magnesium hardness of the effluent; in the sodium hydroxide dosing mode, the control system preferentially meets the treatment requirement of the alkalinity and calcium hardness of the effluent.

[0030] Further, the actual lime dosing amount is 1-1.3 times the theoretical lime dosing amount; the actual sodium carbonate dosing amount is 1-1.3 times the theoretical sodium carbonate dosing amount.

[0031] Compared with the closest prior art, the technical scheme provided by the present application has the following excellent effects:

[0032] ① The intelligent dosing system of this invention selects the operating mode by detecting the calcium hardness, magnesium hardness, and alkalinity of the influent, and adjusts the dosing amount based on the detection of the calcium hardness, magnesium hardness, and alkalinity of the effluent. This automated and intelligent dosing achieves the goal of removing alkalinity and hardness from water at the lowest cost. It realizes a technological breakthrough of "more precise water quality compliance, more controllable reagent costs, and more stable system operation", providing an efficient, economical, and highly adaptable solution for the treatment of high hardness and high alkalinity wastewater, with both environmental and economic benefits.

[0033] ② The process synergy of the intelligent dosing method of the present invention is a multi-dimensional coupling of "chemical principle + equipment control + data feedback": through the synergy of chemical metering of reagent addition, the synergy of reaction environment of pH value control, the synergy of staged treatment of reaction tanks 1 and 2, and the synergy of dynamic control of detection feedback, a self-optimizing intelligent dosing process is constructed; this synergistic mechanism breaks the limitation of "single reagent + fixed parameters" in traditional processes and achieves the technical goal of efficient hardening and alkali removal and low-cost operation.

[0034] ③ The intelligent dosing method of this invention can freely switch between three modes to treat various types of hardness removal wastewater, achieving multiple uses for a single tank. It also has strong resistance to shocks and can cope with wastewater with large changes in water quality. With the minimum dosage, the calcium hardness of the effluent is treated to <70mg / L, the magnesium hardness to <70mg / L, and the alkalinity to <100mg / L. Attached Figure Description

[0035] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein:

[0036] Figure 1 This is a schematic diagram of the intelligent dosing system for removing hardness and alkali from wastewater according to the present invention. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0038] In the description of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. The terms "connected" and "linked" used in this invention should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; they can refer to a direct connection or an indirect connection through intermediate components. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0039] According to a first aspect of the present invention, an intelligent dosing system for hardening and alkali removal wastewater is provided, such as... Figure 1 As shown, it includes:

[0040] Monitoring unit: includes units for monitoring calcium hardness, magnesium hardness, and alkalinity of influent and effluent, and units for monitoring pH value in reaction tank 1;

[0041] Control system: It is connected to the monitoring unit to receive monitoring data, and is used to select the dosing mode and calculate the dosing amount based on the calcium hardness, magnesium hardness and alkalinity data of the influent, and adjust the dosing and pH value based on the feedback of the effluent monitoring data.

[0042] The dosing unit includes a lime dosing device, a sodium hydroxide dosing device, and a sodium carbonate dosing device, which are respectively connected to the control system and dosing the corresponding reagents according to the instructions of the control system.

[0043] The treatment unit includes, in sequence, a coagulation tank, a reaction tank 1, a reaction tank 2, a flocculation tank, and a sedimentation tank; the reaction tank 1 is connected to a lime dosing device and a sodium hydroxide dosing device, and the reaction tank 2 is connected to a sodium carbonate dosing device.

[0044] The intelligent dosing system constructed in this invention acquires key water quality data through a monitoring unit, and the control system selects the appropriate mode and calculates the dosage based on chemical principles and algorithms. The dosing unit precisely administers the chemicals, and the treatment unit completes the reaction and separation. All parts work synergistically and closely together to achieve intelligent, efficient, and precise treatment of hardening and alkali-removing wastewater. Specifically, the coagulation tank adds coagulants to disrupt the colloidal stability of the wastewater, creating conditions for subsequent sedimentation; reaction tank 1, as the main reaction site, completes the Ca... 2+ With CO3 2- Precipitation reaction of Mg 2+ The hydroxide precipitation reaction is carried out simultaneously, and the pH value is adjusted; the reagent is further added to reaction tank 2 to remove residual Ca. 2Alternatively, it can be used to regulate water quality; the flocculation tank promotes the aggregation of small particles into larger flocs, increasing the particle size; the sedimentation tank achieves solid-liquid separation, separating the generated CaCO3 and Mg(OH)2 precipitates from the treated water, thus achieving the purpose of removing hardness and alkali.

[0045] Setting up two reaction tanks (Reaction Tank 1 and Reaction Tank 2) allows for step-by-step reactions, improving treatment efficiency. For example, after the main sedimentation and pH adjustment are completed in Reaction Tank 1, Reaction Tank 2 can perform fine-tuning. Furthermore, it facilitates flexible control of reagent dosing location and reaction time based on different dosing patterns and water quality conditions. For instance, adding sodium carbonate in Reaction Tank 2 allows for more precise reaction with residual calcium. 2+ This reaction reduces drug waste.

[0046] Among them, calcium hardness reflects the calcium content in the water. 2+ The content of CO3 directly relates to the amount of CO3 required for the CaCO3 precipitation reaction. 2- Dosage; magnesium hardness determines Mg removal 2+ The required pH level; alkalinity is expressed as calcium carbonate, characterizing the HCO3- content in the water. - Content, used to determine HCO3 - Converted to CO3 2- Can Ca be satisfied afterward? 2+ Precipitation is required; pH monitoring is used to control the reaction process.

[0047] Influent monitoring data provides a basis for the control system to select the dosing mode and calculate the initial dosage. For example, the relationship between "2×m (alkalinity)" and "m (calcium hardness)" determines whether to add lime, sodium hydroxide, or sodium carbonate. Effluent monitoring data is used for feedback and adjustment. If the calcium hardness, magnesium hardness, or alkalinity of the effluent does not meet the standards, the control system can adjust the dosage and pH value accordingly to achieve closed-loop control and ensure the treatment effect.

[0048] The control system selects the dosing mode based on the comparison between "2×m (alkalinity)" and "m (calcium hardness)" according to the influent calcium hardness, magnesium hardness, and alkalinity data. When 2×m (alkalinity) > m (calcium hardness), it indicates that HCO3... - If there is an excess, choose the lime + sodium hydroxide addition mode to replenish the calcium using lime. 2+ Consuming excessive HCO3 - Sodium hydroxide adjusts the pH; when 2×m (alkalinity) ≈ m (calcium hardness) (here, approximately equal to means the difference between the two is less than 30 mg / L), HCO3 - With Ca 2+ Theoretically, only sodium hydroxide is needed to adjust the pH; when 2×m (alkalinity) < m (calcium hardness), HCO3... - If insufficient, choose the sodium hydroxide + sodium carbonate addition mode, with sodium carbonate supplementing CO3. 2- Remove excess Ca2+ .

[0049] Based on effluent monitoring data, the control system adjusts the dosing and pH value in real time. If the magnesium hardness of the effluent exceeds the standard, the dosage of sodium hydroxide is increased to raise the pH value and promote the precipitation of Mg(OH)2; if the calcium hardness of the effluent exceeds the standard, the dosage of lime or sodium carbonate is increased accordingly under different modes to ensure that the calcium hardness, magnesium hardness and alkalinity of the effluent meet the index requirements of "calcium hardness <70mg / L, magnesium hardness <70mg / L, alkalinity <100mg / L".

[0050] According to a second aspect of the present invention, an intelligent dosing method for treating hardening and alkali removal wastewater using the above-described intelligent dosing system includes the following steps:

[0051] S1. Monitoring steps: The calcium hardness, magnesium hardness, and alkalinity of the influent and effluent, as well as the pH value of reaction tank 1, are monitored in real time through the monitoring unit, and the data is transmitted to the control system.

[0052] S2. Mode Selection and Calculation Steps: The control system uses the built-in dosing mode judgment logic and the dosing amount calculation model to calculate the theoretical dosage of the corresponding agent.

[0053] S3. Chemical dosing reaction steps: The dosing unit adds lime and / or sodium hydroxide to reaction tank 1 and sodium carbonate to reaction tank 2 according to the control system instructions. The wastewater passes through the coagulation tank, reaction tank 1, reaction tank 2, flocculation tank and sedimentation tank in sequence to complete the hardening and alkali removal reaction.

[0054] S4. Feedback and Adjustment Steps: The control system adjusts the dosing and pH value based on the effluent monitoring data to ensure that the effluent meets the following requirements: calcium hardness <70mg / L, magnesium hardness <70mg / L, and alkalinity <100mg / L.

[0055] In the above technical solution, as a preferred embodiment, the residence time of wastewater in reaction tank 1 is 6-8 minutes; the residence time of wastewater in reaction tank 2 is 10-12 minutes. The reagent is added to the middle of the reaction tank wall. Because the reaction tank has a stirrer, it is necessary to avoid the stirrer, and considering the need for uniform mixing, the reagent is added to the middle of the reaction tank wall.

[0056] Typically, except for hard wastewater with a pH of 6-8, the alkalinity in the water exists in the form of bicarbonate ions. Alkalinity is usually measured in terms of calcium carbonate, i.e.:

[0057] c(H + ) = 2 × m (alkalinity) / 100;

[0058] c(HCO3 - )=c(H + ) = 2 × m (alkalinity) / 100;

[0059] The types of alkaline substances in water are complex (such as HCO3). - CO3 2- OH - Directly comparing the concentrations of various alkaline substances (such as calcium carbonate and H2O) makes it difficult to accurately reflect their overall neutralizing capacity. Using calcium carbonate (CaCO3) as a conversion benchmark standardizes the total effect of all alkaline substances into a single numerical value, facilitating cross-sectional comparisons and calculations. The molar mass of calcium carbonate (100.09 g / mol) and its equivalence with hydrogen ions (1 mol CaCO3 corresponds to 2 mol H2O) are discussed. + This simplifies the calculation formulas in titration analysis. For example, the coefficient 50.04 used in the total alkalinity formula is the value of the molar mass of CaCO3 divided by 2.

[0060] Calcium hardness is usually measured in terms of calcium carbonate, i.e.:

[0061] c(Ca 2+ ) = m(calcium hardness) / 100;

[0062] Normally, except for hard reactions where the pH value is >10, all bicarbonate ions in the water are converted to carbonate ions. The carbonate ions then react with calcium ions in the water in a 1:1 ratio, i.e.:

[0063] c(CO3 2- )=c(HCO3 - After the pH is increased;

[0064] Ca 2+ +CO3 2- =CaCO3↓, the two react in a 1:1 molar ratio to form calcium carbonate precipitate;

[0065] When bicarbonate ions are insufficient to remove calcium hardness from water, sodium carbonate needs to be added to remove excess calcium ions; when bicarbonate ions are excessive and sufficient to remove calcium hardness from water, calcium ions (lime) need to be added to remove excess alkalinity.

[0066] c(CO3 2- )=c(HCO3 - )<c(Ca 2+ Sodium carbonate needs to be added;

[0067] After conversion, the result is 2×m (alkalinity) < m (calcium hardness), so sodium carbonate needs to be added.

[0068] Conversely, if 2×m (alkalinity) > m (calcium hardness), calcium ions (lime) need to be added;

[0069] Therefore, by detecting the alkalinity and calcium hardness in the water, the dosing operation mode can be selected: ① When 2×m (alkalinity) > m (calcium hardness), select the lime + sodium hydroxide dosing mode. Lime replenishes calcium ions to remove excess alkalinity, and sodium hydroxide replenishes hydroxide ions to adjust the reaction pH; ② When 2×m (alkalinity) ≈ m (calcium hardness), select the sodium hydroxide dosing mode. The bicarbonate content in the water is just enough to remove calcium ions, so only the reaction pH needs to be adjusted; ③ When 2×m (alkalinity) < m (calcium hardness), select the sodium hydroxide + sodium carbonate dosing mode. Sodium hydroxide replenishes hydroxide ions to adjust the reaction pH, and sodium carbonate replenishes carbonate ions to remove excess calcium ions.

[0070] (1) When 2×m (alkalinity) > m (calcium hardness), choose the lime + sodium hydroxide addition mode.

[0071] c(excess bicarbonate) = c(bicarbonate) - c(Ca) 2+ ) = [2 × m (alkalinity) - m (calcium hardness)] / 100;

[0072] Carbonate ions react with calcium ions in water in a 1:1 ratio. The molar mass of Ca(OH)₂ is 74 g / mol. Therefore:

[0073] c(calcium ion supplementation) = c(excess bicarbonate) = [2 × m(alkalinity) - m(calcium hardness)] / 100;

[0074] m(lime) = c(calcium ion supplement) × 74 = [2 × m(alkalinity) - m(calcium hardness)] × 0.74, which is the theoretical amount of lime to add;

[0075] Typically, the pH for calcium hardness removal is controlled between 10.3 and 10.5, while magnesium hardness removal requires a higher pH to form magnesium hydroxide precipitate. Therefore, during operation, the initial operating condition is a pH of 10.3-10.5, and the reaction pH is adjusted according to the magnesium hardness of the effluent. Specifically, the alkalinity and calcium hardness of the incoming water are first tested to calculate the theoretical amount of lime to be added, and an appropriate amount of sodium hydroxide is added to adjust the reaction pH to 10.3-10.5. The alkalinity, calcium hardness, and magnesium hardness of the effluent are then tested. (Water quality conditions can be considered; if the water quality is relatively stable, a longer testing interval can be used, such as testing every 4 hours or 8 hours; if the water quality fluctuates significantly, testing should be done every 2 hours or 1 hour).

[0076] If the magnesium hardness of the effluent exceeds the standard, the system will be fed back to increase the amount of sodium hydroxide added to raise the reaction pH. As the reaction pH increases, the magnesium hardness of the effluent will gradually decrease. When the magnesium hardness meets the standard, the reaction pH will remain stable.

[0077] If the alkalinity of the effluent exceeds the standard, the system will be fed back to increase the amount of lime added. During the reaction, some calcium hydroxide may not dissolve and may be directly captured and precipitated. Therefore, the actual amount of lime added is usually slightly greater than the theoretical amount (usually 1 to 1.3 times the theoretical amount).

[0078] The control system prioritizes magnesium hardness treatment because increasing the reaction pH also facilitates the reaction between calcium ions and carbonate ions. Therefore, adjusting the amount of lime added at the optimal reaction pH is the most effective way to save on reagents.

[0079] (2) When 2×m (alkalinity) ≈ m (calcium hardness) (the difference between the two is less than 30mg / L), the sodium hydroxide dosing mode is selected; the bicarbonate content in the water is just enough to remove calcium ions from the water, so there is no need to supplement calcium ions and carbonate ions.

[0080] During operation, the initial operating conditions are set at pH 10.3-10.5, and the reaction pH is adjusted according to the magnesium hardness of the effluent.

[0081] If the magnesium hardness of the effluent exceeds the standard, the system will be fed back to increase the amount of sodium hydroxide added to raise the reaction pH. As the reaction pH increases, the magnesium hardness of the effluent will gradually decrease. When the magnesium hardness meets the standard, the reaction pH will remain stable.

[0082] If the alkalinity and calcium hardness of the effluent exceed the standard, the control system will be fed back to increase the amount of sodium hydroxide added. During the reaction, due to incomplete reaction, some calcium ions and carbonate ions may not combine and precipitate. Therefore, it is necessary to increase the reaction pH and accelerate the reaction rate.

[0083] The control system first addresses the alkalinity and calcium hardness requirements, both of which are controlled by pH. Magnesium hardness removal typically has higher pH requirements. Therefore, the system prioritizes meeting the lower pH requirements for calcium hardness removal before addressing the higher pH requirements for magnesium hardness removal, which is beneficial for system stability.

[0084] (3) When 2×m (alkalinity) < m (calcium hardness), select the sodium hydroxide + sodium carbonate addition mode; sodium hydroxide replenishes hydroxide ions to adjust the reaction pH, and sodium carbonate replenishes carbonate ions to remove excess calcium ions;

[0085] c(excess calcium ions) = c(Ca) 2+ c(bicarbonate) = [m(calcium hardness) - 2 × m(alkalinity)] / 100;

[0086] Carbonate ions react with calcium ions in water in a 1:1 ratio. The molar mass of sodium carbonate is 10⁶ g / mol. Therefore:

[0087] c(replenished carbonate ions) = c(excess calcium ions) = [m(calcium hardness) - 2 × m(alkalinity)] / 100;

[0088] m(sodium carbonate) = c(supplemented carbonate ions) × 106 = [m(calcium hardness) - 2 × m(alkalinity)] × 1.06, which is the theoretical dosage of sodium carbonate;

[0089] During operation, the initial operating conditions are set at pH 10.3-10.5, and the reaction pH is adjusted according to the magnesium hardness of the effluent. That is, the alkalinity and calcium hardness of the incoming water are tested first to calculate the theoretical dosage of sodium carbonate, and then the alkalinity, calcium hardness, and magnesium hardness of the effluent are tested.

[0090] If the magnesium hardness of the effluent exceeds the standard, the system will be fed back to increase the amount of sodium hydroxide added to raise the reaction pH. As the reaction pH increases, the magnesium hardness of the effluent will gradually decrease. When the magnesium hardness meets the standard, the reaction pH will remain stable.

[0091] If the calcium hardness of the effluent exceeds the standard, the system will be notified to increase the amount of sodium carbonate added. During the reaction process, the reaction may be incomplete, so the actual amount of sodium carbonate added will usually be slightly greater than the theoretical amount (usually 1 to 1.3 times the theoretical amount).

[0092] The control system prioritizes magnesium hardness treatment because increasing the reaction pH also facilitates the reaction between calcium ions and carbonate ions. Therefore, adjusting the sodium carbonate dosage at the optimal reaction pH is the most efficient way to save on reagents.

[0093] In the first and third operating modes, the control system prioritizes the treatment of magnesium hardness. Since increasing the reaction pH also facilitates the reaction between calcium ions and carbonate ions, adjusting the sodium carbonate dosage at the optimal reaction pH is the most effective way to save on reagents.

[0094] In the second operating mode, the control system prioritizes the treatment of alkalinity and calcium hardness. Both indicators are controlled by pH. Magnesium hardness removal typically requires a higher pH. Therefore, the system first meets the lower pH requirement for calcium hardness removal, then addresses the higher pH requirement for magnesium hardness removal, which is beneficial for system stability. After sufficient hardness and alkali removal, the effluent pH is adjusted to 6-8 (sulfuric acid can be added to adjust the pH; if the pH is too high, scaling can easily occur, leading to clogging of downstream filtration and membrane equipment).

[0095] The system can freely switch between the three modes described above to treat various types of hardening wastewater, achieving multi-purpose use of a single tank. It also boasts strong shock resistance and can handle wastewater with significant quality variations. With minimal chemical dosage, it can treat effluent calcium hardness to <70mg / L, magnesium hardness to <70mg / L, and alkalinity to <100mg / L. Furthermore, intelligent dosing saves on reagents, and the automatic system control reduces manual operation, resulting in an overall operating cost reduction of 20% compared to conventional technologies.

[0096] The present invention will now be described in detail with reference to embodiments thereof. These examples are provided by way of explanation and not by way of limitation. In fact, those skilled in the art will recognize that modifications and variations can be made to the present invention without departing from its scope or spirit. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desirable that the present invention encompass such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0097] In the embodiments of the present invention, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0098] Example 1

[0099] A company in Dalian received raw water for hardening treatment. Inlet water testing revealed the following: pH 7.3, alkalinity 300 mg / L, calcium hardness 800 mg / L, and magnesium hardness 200 mg / L. This inlet water data was fed back to the control system. Calculations showed that 2 × m(alkalinity) = 600 < 800 = m(calcium hardness). Therefore, a sodium hydroxide + sodium carbonate dosing mode was selected, and the system automatically calculated the theoretical sodium carbonate dosage as m(sodium carbonate) = [m(calcium hardness) - 2 × m(alkalinity)] × 1.06 = (800 - 600) × 1.06 = 212 mg / L. The raw water entered the coagulation tank for coagulation and then entered reaction tank 1 where sodium hydroxide was added to adjust the reaction pH. The system initially operated at pH 10.3. Sodium carbonate was then added to reaction tank 2, initially at the theoretical dosage. The solution then entered the flocculation tank for flocculation and finally settled in the sedimentation tank. Effluent data analysis showed that after stable operation under these conditions, the effluent alkalinity was <100 mg / L, calcium hardness was 150 mg / L, and magnesium hardness was 180 mg / L. Since both calcium and magnesium hardness exceeded the standards, feedback was sent to the control system. Magnesium hardness was considered first, and the sodium hydroxide dosage was gradually increased to raise the reaction pH. When the reaction pH reached 10.8, the effluent magnesium hardness was 70 mg / L, meeting the standard. At this point, the effluent calcium hardness was 90 mg / L. Calcium hardness still exceeded the standard, so the sodium carbonate dosage was gradually increased. When the sodium carbonate dosage reached 230 mg / L, the effluent calcium hardness was 70 mg / L, meeting the standard.

[0100] Comparative Example 1

[0101] Unlike Example 1, a conventional hardening high-density tank was used, meaning the treatment unit was the same as in Example 1, except that an intelligent dosing system was not installed. Because the intelligent dosing system was not set up, the dosing could not be adjusted intelligently, which led to the frequent addition of excessive sodium carbonate in order to remove hardness, resulting in excessively high alkalinity of the effluent.

[0102] The effluent parameters of Example 1 and Comparative Example 1 were compared, and the results are shown in Table 1:

[0103] Table 1

[0104]

[0105] Example 2

[0106] A company in Luoyang received raw water for hardening treatment. Inlet water testing revealed the following: pH 7.8, alkalinity 500 mg / L, calcium hardness 600 mg / L, and magnesium hardness 100 mg / L. This inlet water data was fed back to the control system. Calculations showed that 2 × m(alkalinity) = 1000 > 600 = m(calcium hardness). Therefore, a lime + sodium hydroxide dosing mode was selected, and the system automatically calculated the theoretical lime dosage as m(lime) = [2 × m(alkalinity) - m(calcium hardness)] × 0.74 = (1000 - 600) × 0.74 = 296 mg / L. The raw water entered the coagulation tank for coagulation, and then the theoretical amount of lime was added to reaction tank 1. Sodium hydroxide was also added to adjust the reaction pH, with the system initially operating at pH 10.3. No sodium carbonate was added to reaction tank 2 before flocculation in the flocculation tank, followed by sedimentation in the sedimentation tank. Effluent data showed that after stable operation under these conditions, the effluent alkalinity was 200 mg / L, calcium hardness was 60 mg / L, and magnesium hardness was 100 mg / L. Since both alkalinity and magnesium hardness exceeded the standards, feedback was sent to the control system. First, magnesium hardness was considered, and the sodium hydroxide dosage was gradually increased to raise the reaction pH. When the reaction pH reached 10.6, the effluent magnesium hardness was 70 mg / L, meeting the standard. At this point, the effluent alkalinity was 150 mg / L. Alkalinity still exceeded the standard, so the lime dosage was gradually increased while the sodium hydroxide dosage was appropriately reduced to maintain the reaction pH. When the lime dosage increased to 330 mg / L, the effluent alkalinity was <100 mg / L, meeting the standard.

[0107] Comparative Example 2

[0108] Unlike Example 2, a conventional high-density hardness removal tank is used, meaning the treatment unit is the same as in Example 2, except that an intelligent dosing system is not installed. Because the dosing cannot be intelligently adjusted, the amount of lime added is excessive, which requires the addition of sodium carbonate to eliminate the excess calcium ions, resulting in waste of the reagents.

[0109] The effluent parameters of Example 2 and Comparative Example 2 were compared, and the results are shown in Table 2:

[0110] Table 2

[0111]

[0112] Example 3

[0113] A company in Fujian province received influent water for hardening treatment. Influent water testing revealed the following: pH 7.5, alkalinity 400 mg / L, calcium hardness 800 mg / L, and magnesium hardness 50 mg / L. This influent data was fed back to the control system. Calculations were performed to determine the optimal sodium hydroxide dosing mode: 2 × m (alkalinity) = 800 = 800 = m (calcium hardness). The raw water then entered a coagulation tank for coagulation and subsequently entered reaction tank 1 where sodium hydroxide was added to adjust the reaction pH. The system initially operated at pH 10.3. No sodium carbonate needs to be added to reaction tank 2 before flocculation in the flocculation tank, and finally sedimentation in the sedimentation tank. The effluent data shows that after stable operation under these conditions, the alkalinity of the effluent is 150 mg / L, the calcium hardness is 120 mg / L, and the magnesium hardness is 50 mg / L. The alkalinity and calcium hardness both exceed the standards. Feedback is sent to the control system, and the amount of sodium hydroxide added is gradually increased to raise the reaction pH. When the reaction pH is raised to 10.35, the calcium hardness of the effluent is 70 mg / L, and the alkalinity of the effluent is <100 mg / L.

[0114] Comparative Example 3

[0115] Unlike Example 3, a conventional hardening high-density tank is used, meaning the treatment unit is the same as in Example 1, except that an intelligent dosing system is not installed. Since the dosing cannot be intelligently adjusted, the reaction pH is controlled at a higher level to ensure that the hardness of the effluent meets the standard. This not only results in waste of sodium hydroxide dosing, but also in a relatively higher amount of acid added for subsequent pH adjustment.

[0116] The effluent parameters of Example 3 and Comparative Example 3 were compared, and the results are shown in Table 3:

[0117] Table 3

[0118]

[0119]

[0120] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An intelligent dosing system for hardening and alkali removal wastewater, characterized in that, include: Monitoring unit: includes units for monitoring calcium hardness, magnesium hardness, and alkalinity of influent and effluent, and units for monitoring pH value in reaction tank 1; Control system: It is connected to the monitoring unit to receive monitoring data, and is used to select the dosing mode and calculate the dosing amount based on the calcium hardness, magnesium hardness and alkalinity data of the influent, and adjust the dosing and pH value based on the feedback of the effluent monitoring data. The dosing unit includes a lime dosing device, a sodium hydroxide dosing device, and a sodium carbonate dosing device, which are respectively connected to the control system and dosing the corresponding reagents according to the instructions of the control system. The treatment unit includes, in sequence, a coagulation tank, a reaction tank 1, a reaction tank 2, a flocculation tank, and a sedimentation tank; the reaction tank 1 is connected to a lime dosing device and a sodium hydroxide dosing device, and the reaction tank 2 is connected to a sodium carbonate dosing device.

2. The intelligent dosing system according to claim 1, characterized in that, The control system has a built-in dosing mode determination logic; based on the influent alkalinity m (alkalinity) and calcium hardness m (calcium hardness), it determines the following three modes: When 2×m (alkalinity) > m (calcium hardness), choose the lime + sodium hydroxide addition mode; When 2×m (alkalinity) ≈ m (calcium hardness), select the sodium hydroxide addition mode; When 2×m (alkalinity) < m (calcium hardness), the sodium hydroxide + sodium carbonate addition mode is selected.

3. The intelligent dosing system according to claim 2, characterized in that, The control system has a built-in dosing calculation model: In the lime + sodium hydroxide addition mode, the lime addition amount m(lime) = [2×m(alkalinity) - m(calcium hardness)]×0.74; In the sodium hydroxide + sodium carbonate addition mode, the sodium carbonate addition amount m(sodium carbonate) = [m(calcium hardness) - 2 × m(alkalinity)] × 1.

06.

4. A method for intelligent dosing of hardening and alkali-removing wastewater using the intelligent dosing system according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Monitoring steps: The calcium hardness, magnesium hardness, and alkalinity of the influent and effluent, as well as the pH value of reaction tank 1, are monitored in real time through the monitoring unit, and the data is transmitted to the control system. S2. Mode Selection and Calculation Steps: The control system uses the built-in dosing mode judgment logic and the dosing amount calculation model to calculate the theoretical dosage of the corresponding agent. S3. Chemical dosing reaction steps: The dosing unit adds lime and / or sodium hydroxide to reaction tank 1 and sodium carbonate to reaction tank 2 according to the control system instructions. The wastewater passes through the coagulation tank, reaction tank 1, reaction tank 2, flocculation tank and sedimentation tank in sequence to complete the hardening and alkali removal reaction. S4. Feedback and Adjustment Steps: The control system adjusts the dosing and pH value based on the effluent monitoring data to ensure that the effluent meets the following requirements: calcium hardness <70mg / L, magnesium hardness <70mg / L, and alkalinity <100mg / L.

5. The intelligent dosing method according to claim 4, characterized in that, The residence time of wastewater in reaction tank 1 is 6-8 minutes; the residence time of wastewater in reaction tank 2 is 10-12 minutes.

6. The intelligent dosing method according to claim 4, characterized in that, In the lime + sodium hydroxide addition mode, the alkalinity and calcium hardness of the influent are tested, the theoretical amount of lime is calculated, and sodium hydroxide is added to adjust the pH value in reaction tank 1 to 10.3-10.5; adjustments are made based on feedback from the magnesium hardness and alkalinity of the effluent; if the magnesium hardness of the effluent exceeds the standard, the amount of sodium hydroxide added is increased; if the alkalinity of the effluent exceeds the standard, the amount of lime added is increased.

7. The intelligent dosing method according to claim 6, characterized in that, In the sodium hydroxide dosing mode, sodium hydroxide is added to adjust the pH value in reaction tank 1 to 10.3-10.5; adjustments are made based on feedback from the magnesium hardness, alkalinity, and calcium hardness of the effluent; if the magnesium hardness of the effluent exceeds the standard, the amount of sodium hydroxide added is increased; if the alkalinity and calcium hardness of the effluent exceed the standard, the amount of sodium hydroxide added is increased.

8. The intelligent dosing method according to claim 7, characterized in that, In the sodium hydroxide + sodium carbonate dosing mode, the alkalinity and calcium hardness of the influent are detected, the theoretical dosage of sodium carbonate is calculated, and sodium hydroxide is added to adjust the pH value in reaction tank 1 to 10.3-10.5; adjustments are made based on feedback from the magnesium hardness and calcium hardness of the effluent; if the magnesium hardness of the effluent exceeds the standard, the dosage of sodium hydroxide is increased; if the calcium hardness of the effluent exceeds the standard, the dosage of sodium carbonate is increased.

9. The intelligent dosing method according to claim 8, characterized in that, In the lime + sodium hydroxide dosing mode and the sodium hydroxide + sodium carbonate dosing mode, the control system prioritizes meeting the treatment requirements for magnesium hardness in the effluent; in the sodium hydroxide dosing mode, the control system prioritizes meeting the treatment requirements for alkalinity and calcium hardness in the effluent.

10. The intelligent dosing method according to claim 8, characterized in that, The actual amount of lime added is 1 to 1.3 times the theoretical amount of lime added; the actual amount of sodium carbonate added is 1 to 1.3 times the theoretical amount of sodium carbonate added.

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