Membrane concentration pretreatment system and method

Abstract

The invention provides a membrane concentration pretreatment system and method. The system comprises an activated carbon adsorption unit, a silicon and fluorine removal unit, a softening and hardness removal unit and an ultrafiltration unit which are sequentially connected in series through pipelines, the silicon and fluorine removal unit comprises a silicon removal reaction cavity, a fluorine removal reaction cavity and a first precipitation assembly which are communicated in sequence, and the first precipitation assembly is communicated with the softening and hardness removal unit through a pipeline; the softening and hardness removal unit comprises a hardness removal reaction cavity and a second precipitation assembly which are communicated in sequence; the second precipitation assembly is communicated with the ultrafiltration unit through a pipeline. According to the invention, the concentrated water of the first-stage membrane system can be pretreated, so that the concentrated water meets the water inlet standards of second-stage membrane systems such as a high-pressure reverse osmosis membrane system, a high-pressure nanofiltration membrane system and the like.

Description

Technical Field

[0001] The invention relates to the field of water treatment, and in particular to a membrane concentration pretreatment system and method. Background Art

[0002] As one of the industrial wastewaters discharged during the steel production process, the treatment and reuse of coking wastewater is of great strategic significance to the sustainable development of the steel industry. The concept of "zero discharge" of industrial wastewater in the steel industry refers to the extraction of salt from industrial wastewater after deep treatment, membrane system purification and other treatment methods, while the pollutants are highly concentrated and recycled for reuse. The coking wastewater in the steel industry has complex and diverse pollutants, high concentrations of organic pollutants, and high indicators such as fluoride ions and silica.

[0003] The zero-discharge salt separation treatment process of coking wastewater mainly includes primary membrane pretreatment, primary membrane treatment unit (including low-pressure reverse osmosis system), secondary membrane pretreatment, secondary membrane treatment unit (including nanofiltration salt separation system and high-pressure reverse osmosis concentration and purification system) and evaporation crystallization unit. Among them, after the coking wastewater is pretreated by the primary membrane and then concentrated by the primary reverse osmosis membrane of the primary membrane treatment unit, the pollutant concentration in the wastewater reaches a new high, and the stable operation of the back-end membrane system (secondary membrane treatment unit) cannot be guaranteed. Therefore, it is necessary to further pretreat the primary membrane concentrated water discharged from the primary membrane treatment unit to meet the water inlet requirements of the nanofiltration salt separation system and the high-pressure reverse osmosis concentration and purification system. The stable operation of the membrane system mainly focuses on the following water quality indicators: organic pollutants COD, silica, fluoride ions, calcium and magnesium ions. However, the traditional single pretreatment method consumes more reagents, has high operating costs, a large labor load, and weak shock load resistance. The water quality fluctuation has a greater impact on the stable operation of the membrane system, and it is impossible to systematically coordinate the treatment of organic pollutants in concentrated brine and inorganic substances such as calcium and magnesium ions. Summary of the invention

[0004] The object of the present invention is to provide a membrane concentration pretreatment system and method, which can pretreat the concentrate of a primary membrane system to make it meet the water inlet standards of a secondary membrane system such as a high-pressure reverse osmosis membrane system and a high-pressure nanofiltration membrane system.

[0005] In order to achieve the above object, the present invention provides a membrane concentration pretreatment system, which includes an activated carbon adsorption unit, a silicon removal and fluorine removal unit, a softening and hardness removal unit and an ultrafiltration unit which are sequentially connected in series through a pipeline;

[0006] The desiliconization and defluorination unit comprises a desiliconization reaction chamber, a defluorination reaction chamber and a first precipitation component which are connected in sequence, and the first precipitation component is connected to the softening and dehardening unit through a pipeline;

[0007] The softening and hardness removal unit comprises a hardness removal reaction chamber and a second precipitation component which are connected in sequence, and the second precipitation component is connected to the ultrafiltration unit through a pipeline.

[0008] Optionally, the activated carbon adsorption unit includes a first reflux pipe, an activated carbon adsorption tower and an activated carbon replenishing device, the activated carbon replenishing device is used to replenish activated carbon to the activated carbon adsorption tower, the first reflux pipe connects the inlet and outlet of the activated carbon adsorption tower, when the effluent COD concentration of the activated carbon adsorption tower exceeds a first preset value, the effluent of the activated carbon adsorption tower returns to the inlet of the activated carbon adsorption tower through the first reflux pipe for reprocessing.

[0009] Optionally, the activated carbon replenishing device includes an activated carbon regeneration component and an activated carbon replenishing component, wherein the activated carbon regeneration component is used to receive the activated carbon discharged from the activated carbon adsorption tower and regenerate the activated carbon, and transport the regenerated activated carbon to the activated carbon adsorption tower, and the activated carbon replenishing component is used to replenish activated carbon to the activated carbon adsorption tower through a pipeline.

[0010] Optionally, the silicon removal and fluorine removal unit includes a first pH adjustment chamber connected to the silicon removal reaction chamber, and the first pH adjustment chamber is connected to the outlet of the activated carbon adsorption unit; the softening and hardness removal unit includes a second pH adjustment chamber connected to the hardness removal reaction chamber, and the second pH adjustment chamber is connected to the water outlet of the first precipitation component; the silicon removal and fluorine removal unit includes a sodium aluminate addition component and an aluminum sulfate addition component, the addition port of the sodium aluminate addition component leads to the silicon removal reaction chamber, and the addition port of the aluminum sulfate addition component leads to the fluorine removal reaction chamber; the softening and hardness removal unit includes a sodium carbonate addition component, and the addition port of the sodium carbonate addition component leads to the hardness removal reaction chamber.

[0011] Optionally, the first sedimentation component includes a first flocculation chamber and a first sedimentation chamber that are connected, the first flocculation chamber is connected to the defluorination reaction chamber, and the first sedimentation chamber is connected to the softening and hardness removal unit through a pipeline, for conveying the effluent of the first sedimentation chamber to the softening and hardness removal unit; the second sedimentation component includes a second flocculation chamber and a second sedimentation chamber that are connected, the second flocculation chamber is connected to the defluorination reaction chamber, and the second sedimentation chamber is connected to the ultrafiltration unit through a pipeline, for conveying the effluent of the second sedimentation chamber to the ultrafiltration unit.

[0012] Optionally, the membrane concentration pretreatment system includes a sludge treatment unit, which includes a sludge thickening tank, which is connected to the first sedimentation component and the second sedimentation component through pipelines, respectively, for receiving and treating sludge discharged from the first sedimentation component and the second sedimentation component.

[0013] Optionally, the sludge thickening tank is connected to the silicon removal and fluorine removal unit, so that the supernatant of the sludge thickening tank is transported to the silicon removal and fluorine removal unit for silicon removal and fluorine removal treatment.

[0014] Optionally, the ultrafiltration unit has a water production port and a concentrate water port, and the concentrate water port of the ultrafiltration unit is connected to the silicon removal and fluorine removal unit through a pipeline, so that the concentrate water of the ultrafiltration unit is transported to the silicon removal and fluorine removal unit for silicon removal and fluorine removal treatment, and the water production port of the ultrafiltration unit is used to connect with the back-end membrane system.

[0015] Based on another aspect of the present invention, the present invention also provides a membrane concentration pretreatment method, which is applied to the membrane concentration pretreatment system as described above. The membrane concentration pretreatment method comprises:

[0016] The wastewater is sequentially transported to the activated carbon adsorption unit, the silicon and fluorine removal unit, the softening and hardness removal unit and the ultrafiltration unit for treatment;

[0017] Wherein, when the COD concentration of the effluent from the activated carbon adsorption unit exceeds a first preset value, the effluent from the activated carbon adsorption unit is transported to the inlet of the activated carbon adsorption unit for reprocessing;

[0018] When the silica concentration of the effluent from the silicon removal and fluorine removal unit exceeds a second preset value or the fluorine ion concentration exceeds a third preset value, the effluent from the silicon removal and fluorine removal unit is transported to the inlet of the silicon removal and fluorine removal unit for reprocessing;

[0019] When the hardness of the outlet water of the softening and hardness-removing unit exceeds a fourth preset value, the outlet water of the softening and hardness-removing unit is transported to the inlet of the softening and hardness-removing unit for reprocessing.

[0020] Optionally, the pH value of the influent water entering the desiliconization reaction chamber is adjusted to 8-9, sodium aluminate is added to the desiliconization reaction chamber, and aluminum sulfate is added to the defluorination reaction chamber; the pH value of the influent water entering the hardness removal reaction chamber is adjusted to 10-12, and sodium carbonate is added to the hardness removal reaction chamber.

[0021] As configured above, the present invention makes full use of two process technologies, activated carbon adsorption and chemical coagulation and precipitation. The carbon content of the effluent of the activated carbon adsorption unit can further promote the chemical precipitation of the silicon removal and fluorine removal unit and the softening and hardness removal unit, while avoiding the influence of carbon powder on the membrane element (such as clogging the membrane element); the present invention comprehensively considers the order of adding drugs for silicon removal, fluorine removal, and hardness removal, makes full use of the reagents, and reduces the cost of the reagents; the present invention sets a silicon removal and fluorine removal unit and a softening and hardness removal unit before the ultrafiltration unit, and after two rounds of chemical coagulation and precipitation of the silicon removal and fluorine removal unit and the softening and hardness removal unit, the impact load resistance capacity of the membrane concentration pretreatment system is improved, and the influent water quality of the ultrafiltration unit is ensured to be stably controlled, and the technical effects of deep silicon removal, fluorine removal, hardness removal and solid-liquid separation are achieved. Through multi-step silicon removal, fluorine removal, and hardness removal, the frequency of clogging of the membrane element is greatly reduced. The present invention has the characteristics of high hardness removal rate and stable system operation. The concentrated water of the primary membrane system can meet the water inlet standards of secondary membrane systems such as high-pressure reverse osmosis membrane systems and high-pressure nanofiltration membrane systems after being treated by the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Those skilled in the art should understand that the drawings are provided for a better understanding of the present invention and do not constitute any limitation on the scope of the present invention.

[0023] Figure 1 Schematic diagram of a membrane concentration pretreatment system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] In this document, unless otherwise specified, the terms "upper", "lower", "left", "right", "inside", "outside", "front", "back", "top", "bottom", etc. are used to indicate directions or positional relationships based on the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction and operation. Therefore, they cannot be understood as limiting the present invention.

[0025] The specific implementation of the present invention will be described in more detail below in conjunction with the schematic diagram. The advantages and features of the present invention will become clearer based on the following description. It should be noted that the drawings are all in a very simplified form and are not in exact proportions, and are only used to facilitate and clearly assist in explaining the purpose of the embodiments of the present invention.

[0026] Figure 1 is a schematic diagram of a membrane concentration pretreatment system according to an embodiment of the present invention. Figure 1 An embodiment of the present invention provides a membrane concentration pretreatment system, which includes an activated carbon adsorption unit, a silicon and fluorine removal unit, a softening and hardness removal unit and an ultrafiltration unit which are connected in series in sequence through pipelines. The activated carbon adsorption unit plays a role in reducing the COD concentration.

[0027] The activated carbon adsorption unit includes a first reflux pipe, an activated carbon adsorption tower and an activated carbon supplementing device. The activated carbon supplementing device is used to supplement activated carbon to the activated carbon adsorption tower. The first reflux pipe connects the inlet and outlet of the activated carbon adsorption tower. When the COD concentration of the effluent of the activated carbon adsorption tower exceeds the first preset value, the effluent of the activated carbon adsorption tower returns to the inlet of the activated carbon adsorption tower through the first reflux pipe for reprocessing. Exemplarily, a COD detector is set at the outlet of the activated carbon adsorption tower. When the COD concentration detected by the COD detector here exceeds the first preset value, the effluent of the activated carbon adsorption tower at this time is transported back to the inlet of the activated carbon adsorption tower through the first reflux pipe for reprocessing to continue to reduce the effluent COD concentration until the effluent COD concentration is less than or equal to the first preset value. Further, the activated carbon supplementing device includes an activated carbon regeneration component and an activated carbon supplementing component. The activated carbon regeneration component is used to receive the activated carbon discharged from the activated carbon adsorption tower through a pipeline and regenerate the activated carbon, and transport the regenerated activated carbon to the activated carbon adsorption tower through a pipeline. In this way, the activated carbon can be reused, saving production costs. For example, the activated carbon regeneration component may include an activated carbon regeneration furnace, and when in operation, the activated carbon adsorption tower may be controlled to discharge carbon to the activated carbon regeneration furnace once every 2-3 minutes. The activated carbon supplement component is used to supplement the activated carbon to the activated carbon adsorption tower through a pipeline. For example, the first preset value may be 50% of the design concentration value. When the COD detector at the outlet of the activated carbon adsorption tower detects that the outlet COD concentration exceeds the design concentration value for 8 consecutive hours (even if the activated carbon is regenerated by the activated carbon regeneration component, there will inevitably be a loss of activated carbon, so this situation will occur), the activated carbon supplement component is used to supplement the activated carbon adsorption tower with additional activated carbon.

[0028] The silicon removal and fluorine removal unit comprises a silicon removal reaction chamber, a fluorine removal reaction chamber and a first precipitation assembly which are connected in sequence, the first precipitation assembly is connected to the softening and hardness removal unit through a pipeline, the first precipitation assembly comprises a first flocculation chamber and a first precipitation chamber which are connected, the first flocculation chamber is connected to the fluorine removal reaction chamber, the first precipitation chamber is connected to the softening and hardness removal unit through a pipeline, and is used to transport the effluent of the first precipitation chamber to the softening and hardness removal unit. Exemplarily, the first precipitation chamber can be an inclined plate precipitation chamber.

[0029] The softening and hardness removal unit includes a hardness removal reaction chamber and a second precipitation component connected in sequence, the second precipitation component is connected to the ultrafiltration unit through a pipeline, the second precipitation component includes a second flocculation chamber and a second precipitation chamber connected, the second flocculation chamber is connected to the hardness removal reaction chamber, and the second precipitation chamber is connected to the ultrafiltration unit through a pipeline, for conveying the effluent of the second precipitation chamber to the ultrafiltration unit. Exemplarily, the second precipitation chamber can be an inclined plate precipitation chamber.

[0030] Furthermore, the silicon removal and fluorine removal unit includes a first pH adjustment chamber connected to the silicon removal reaction chamber, the first pH adjustment chamber is connected to the outlet of the activated carbon adsorption unit, in the present embodiment, the first pH adjustment chamber is connected to the water outlet of the activated carbon adsorption tower, and the first pH adjustment chamber is used to adjust the pH value of the inlet water of the silicon removal reaction chamber; the softening and hardness removal unit includes a second pH adjustment chamber connected to the hardness removal reaction chamber, the second pH adjustment chamber is connected to the water outlet of the first precipitation component, in the present embodiment, the second pH adjustment chamber is connected to the water outlet of the first precipitation chamber, and the second pH adjustment chamber is used to adjust the pH value of the inlet water of the hardness removal reaction chamber; the silicon removal and fluorine removal unit includes a sodium aluminate addition component and an aluminum sulfate addition component, the addition port of the sodium aluminate addition component leads to the silicon removal reaction chamber, and the addition port of the aluminum sulfate addition component leads to the fluorine removal reaction chamber; the softening and hardness removal unit includes a sodium carbonate addition component, and the addition port of the sodium carbonate addition component leads to the hardness removal reaction chamber.

[0031] The silicon removal and fluorine removal unit can be a whole pool, which is divided into 5 interconnected chambers, namely the first pH adjustment chamber, silicon removal reaction chamber, fluorine removal reaction chamber, first flocculation chamber and first sedimentation chamber; the softening and hardness removal unit can be a whole pool, which is divided into 4 interconnected chambers, namely the second pH adjustment chamber, hardness removal reaction chamber, second flocculation chamber and second sedimentation chamber.

[0032] Preferably, the membrane concentration pretreatment system includes a sludge treatment unit, and the sludge treatment unit includes a sludge thickening tank, which is connected to the first precipitation component and the second precipitation component through pipelines, respectively, for receiving and processing the sludge discharged from the first precipitation component and the second precipitation component. Further, the sludge thickening tank is connected to the silicon removal and fluorine removal unit, so that the supernatant of the sludge thickening tank is transported to the silicon removal and fluorine removal unit for silicon removal and fluorine removal. In this embodiment, the sludge thickening tank is connected to the first precipitation chamber and the second precipitation chamber through pipelines. The sludge concentrated liquid obtained after the treatment in the sludge thickening tank is transported to a filter press, such as a plate and frame filter press, and the filter press outputs the mud cake after treatment. The supernatant of the sludge thickening tank and the filtered liquid of the filter press are transported to the first pH adjustment chamber through pipelines and continue to be processed along the subsequent process flow. Preferably, cationic PAM is added to the sludge thickening tank, and the precipitation is slowly stirred.

[0033] The ultrafiltration unit has a water outlet and a concentrate outlet. The concentrate outlet of the ultrafiltration unit is connected to the silicon removal and fluorine removal unit through a pipeline, so that the concentrate of the ultrafiltration unit is transported to the silicon removal and fluorine removal unit for silicon removal and fluorine removal. For example, the ultrafiltration unit is connected to the first pH adjustment chamber through a pipeline. The water outlet of the ultrafiltration unit is used to communicate with the back-end membrane system. In this embodiment, the concentrate of the primary membrane system enters the activated carbon adsorption unit, and the water outlet of the ultrafiltration unit is connected to the water inlet of the secondary membrane system. The ultrafiltration unit includes an immersed ultrafiltration tank. The ultrafiltration unit can separate insoluble impurities and particulate matter. At the same time, compared with conventional internal and external pressure ultrafiltration, the use of immersed ultrafiltration can effectively reduce the organic pollution formed by floccules such as PAM (polyacrylamide) on the surface of the ultrafiltration membrane, thereby reducing the use of agents for cleaning the ultrafiltration membrane and the operating cost. The submerged ultrafiltration tank discharges concentrated water every 1-2 hours to the first pH adjustment chamber. The bottom of the submerged ultrafiltration tank adopts intermittent aeration with adjustable intermittent time. Aeration can vibrate the ultrafiltration membrane, thereby reducing the probability of ultrafiltration membrane clogging.

[0034] Preferably, a central industrial frequency agitator device is provided in the first pH adjustment chamber, the silicon removal reaction chamber, the fluorine removal reaction chamber, the second pH adjustment chamber and the hardness removal reaction chamber to improve the treatment effect; a central variable frequency agitator device is provided in the first flocculation chamber and the second flocculation chamber, so that the homogenized waste liquid reacts more fully after stirring and the treatment effect is better; a variable frequency agitator is provided at the bottom of the first sedimentation chamber and the bottom of the second sedimentation chamber, and the stirring speed is controlled so as not to destroy large particles.

[0035] This embodiment is equipped with multiple pH detectors. This embodiment can also be equipped with a pid control system. The pid control system is electrically connected to the pH detectors, various automatic valves, various electric pumps, and other equipment in the present invention to achieve automatic control.

[0036] Based on the above-mentioned membrane concentration pretreatment system, this embodiment also provides a membrane concentration pretreatment method, which includes: transporting the wastewater to an activated carbon adsorption unit, a silicon and fluorine removal unit, a softening and hardness removal unit and an ultrafiltration unit in sequence for treatment.

[0037] Wherein, when the COD concentration of the effluent from the activated carbon adsorption unit exceeds a first preset value, the effluent from the activated carbon adsorption unit is transported to the inlet of the activated carbon adsorption unit for reprocessing;

[0038] When the silica concentration of the outlet water of the silicon removal and fluorine removal unit exceeds the second preset value or the fluoride ion concentration exceeds the third preset value, the outlet water of the silicon removal and fluorine removal unit is transported to the inlet of the silicon removal and fluorine removal unit for reprocessing. The second preset value and the third preset value may be the same or different. The outlet and inlet of the silicon removal and fluorine removal unit are connected through a second reflux pipe (not shown in the figure).

[0039] When the hardness of the water outlet of the softening and hardening removal unit exceeds the fourth preset value, the water outlet of the softening and hardening removal unit is transported to the inlet of the softening and hardening removal unit for reprocessing. The outlet and inlet of the softening and hardening removal unit are connected through a third reflux pipe (not shown in the figure).

[0040] Optionally, the pH value of the influent water entering the desiliconization reaction chamber is adjusted to 8-9, sodium aluminate is added to the desiliconization reaction chamber, and aluminum sulfate is added to the defluorination reaction chamber; the pH value of the influent water entering the hardness removal reaction chamber is adjusted to 10-12, and sodium carbonate is added to the hardness removal reaction chamber.

[0041] As configured above, the present invention makes full use of two process technologies, activated carbon adsorption and chemical coagulation and precipitation. The carbon content of the effluent of the activated carbon adsorption unit can further promote the chemical precipitation of the silicon removal and fluorine removal unit and the softening and hardness removal unit, while avoiding the influence of carbon powder on the membrane element (such as clogging the membrane element); the present invention comprehensively considers the order of adding drugs for silicon removal, fluorine removal, and hardness removal, makes full use of the reagents, and reduces the cost of the reagents; the present invention sets a silicon removal and fluorine removal unit and a softening and hardness removal unit before the ultrafiltration unit, and after two rounds of chemical coagulation and precipitation of the silicon removal and fluorine removal unit and the softening and hardness removal unit, the impact load resistance capacity of the membrane concentration pretreatment system is improved, and the influent water quality of the ultrafiltration unit is ensured to be stably controlled, and the technical effects of deep silicon removal, fluorine removal, hardness removal and solid-liquid separation are achieved. Through multi-step silicon removal, fluorine removal, and hardness removal, the frequency of clogging of the membrane element is greatly reduced. The present invention has the characteristics of high hardness removal rate and stable system operation. The concentrated water of the primary membrane system can meet the water inlet standards of secondary membrane systems such as high-pressure reverse osmosis membrane systems and high-pressure nanofiltration membrane systems after being treated by the present invention.

[0042] The membrane concentration pretreatment method is described in detail through steps one to four below.

[0043] Step 1: Detect the pH value and COD, silica, fluoride ion, calcium, magnesium ion and bicarbonate concentration in the concentrated water (coking high-concentration brine) output from the primary membrane system.

[0044] The coking high-concentration brine is passed through an activated carbon adsorption tower to adsorb COD, and the regeneration and carbon discharge time interval of the activated carbon adsorption tower is controlled to be 2-3 minutes.

[0045] Step 2: The effluent from the activated carbon adsorption unit enters the first pH adjustment chamber, the silicon removal reaction chamber, the fluorine removal reaction chamber, the first flocculation chamber and the first precipitation chamber in sequence.

[0046] The pH value of the first pH adjustment chamber is controlled at 8-9 to adjust the pH value of the water inlet of the silicon removal reaction chamber. Specifically, alkali (which can be liquid alkali) and acid (which can be hydrochloric acid) addition points are set in the first pH adjustment chamber, and the pH value of the first pH adjustment chamber is controlled at 8-9 by alkali and acid dosing pumps; sodium aluminate solution is added to the silicon removal reaction chamber, and sodium aluminate reacts with silicon salt to precipitate to remove silicon dioxide in the wastewater; aluminum sulfate solution is added to the fluoride removal reaction chamber, and aluminum sulfate reacts with fluoride ions to precipitate to remove fluoride ions in the wastewater; the pH value of the first flocculation chamber is maintained at a neutral 7-7.5, and anion PAM is added to the first flocculation chamber to improve the coagulation and flocculation effect and neutrally precipitate aluminum salt; the first precipitation chamber is used to remove silicate and fluoride precipitates.

[0047] The dosage of sodium aluminate (L / h) is k1×Q1×[(C1-C2) / 60×82]×10 -3 / C3, where Q1 is the water flow rate of the desiliconization reaction chamber, C1 is the silica concentration of the water inlet of the desiliconization reaction chamber (mg / L), C2 is the target silica concentration (mg / L), C3 is the concentration of the agent in the sodium aluminate dosing box (%), and k1 is a constant with a value range of 1-2.5. It can be understood that C1 can be measured by the first pH adjustment chamber, and Q1 can be measured by setting a flow meter at the water inlet of the desiliconization reaction chamber.

[0048] The dosage of aluminum sulfate solution (L / h) is equal to k4×Q3×[(C9-C10) / 19×342]×10 -3 / C11, where Q3 is the water flow rate of the defluorination reaction chamber, C9 is the fluoride ion concentration of the water of the defluorination reaction chamber (mg / L), C10 is the target fluoride ion concentration mg / L, C11 is the concentration of the aluminum sulfate solution (%), and k4 is a constant with a value range of 2-3. It can be understood that C9 can be measured in the first pH adjustment chamber, and Q3 can be measured by setting a flow meter at the water inlet of the defluorination reaction chamber.

[0049] The pH value in the first pH adjustment chamber needs to be adjusted to 8-9 to facilitate the subsequent removal of silicon dioxide. In the defluorination reaction chamber, the pH value can be reduced to 7-8 by adding aluminum sulfate, which not only ensures the effectiveness of defluorination and desiliconization, but also effectively reduces the dosage of hydrochloric acid and sodium hydroxide.

[0050] The second preset value can be 1.2 times of C2, and the third preset value can be 1.2 times of C10. When the silica concentration in the effluent of the silicon removal and fluorine removal unit, that is, the effluent of the first sedimentation chamber, exceeds 1.2 times of C2, or the fluoride ion concentration in the effluent of the first sedimentation chamber exceeds 1.2 times of C10, it can be regarded as abnormal effluent water and needs to return to the inlet of the silicon removal and fluorine removal unit through the second reflux pipe for reprocessing, that is, return to the first pH adjustment chamber.

[0051] Step 3: The effluent from the first sedimentation chamber enters the second pH adjustment chamber, the hardness removal reaction chamber, the second flocculation chamber, and the second sedimentation component in sequence.

[0052] Alkali (which can be liquid alkali) and acid (which can be hydrochloric acid) addition points are set in the second pH adjustment chamber, and the pH value of the second pH adjustment chamber is controlled at 10-12 by alkali and acid dosing pumps. If the magnesium ion concentration of the water entering the second pH adjustment chamber is equivalent to the calcium ion concentration, the pH range is adjusted to 11.5-12; sodium carbonate (which can be 8% sodium carbonate solution) is added to the hardness removal reaction chamber for stirring reaction; anion PAM is added to the second flocculation chamber to improve the coagulation and flocculation effect; the second sedimentation chamber is used to separate calcium carbonate and magnesium carbonate sedimentation sludge.

[0053] Among them, the dosage of sodium carbonate (L / h) is {k2×Q2×[(C4-C5) / 40×106]×10 -3 / C6}+{k3×Q2×[(C7-C8) / 61×106]×10 -3 / C6}, wherein Q2 is the water inlet flow rate of the hardness removal reaction chamber, C4 is the calcium ion concentration of the inlet water of the hardness removal reaction chamber (mg / L), C5 is the target calcium ion concentration (mg / L), C6 is the reagent concentration of sodium carbonate solution (%), C7 is the target bicarbonate concentration (mg / L), C8 is the bicarbonate concentration of the inlet water of the hardness removal reaction chamber (mg / L), k2 is a constant and its value range is 1-3, k3 is a constant and its value range is 1-1.5.

[0054] When the hardness of the outlet water of the softening and hardness removal unit exceeds the fourth preset value, the outlet water of the softening and hardness removal unit is transported to the inlet of the softening and hardness removal unit for reprocessing. The fourth preset value is the hardness index entering the secondary membrane system. Let the calcium ion concentration (mg / L) of the outlet water of the softening and hardness removal unit be a and the magnesium ion concentration (mg / L) be b, then the hardness of the outlet water of the softening and hardness removal unit is 2.5a+4.1b. Exemplarily, the fourth preset value can be 100 mg / L.

[0055] Step 4: The effluent from the softening and hardness removal unit, i.e. the effluent from the second sedimentation chamber, enters the submerged ultrafiltration tank for filtration.

[0056] After a period of stable operation, the water quality analysis of the concentrated water output by the primary membrane system and the water produced by the ultrafiltration unit is shown in Table 1:

[0057]

[0058] Table 1

[0059] It can be seen from Table 1 that the COD, calcium ions, magnesium ions, silica and fluoride ions in the water produced by the ultrafiltration unit can be controlled within the requirements of the effluent water quality, and the water inlet requirements of the secondary membrane system are fully met; the membrane concentration pretreatment system of this embodiment operates stably for about 1 month, and there is no obvious abnormality in the pressure difference of the secondary membrane system, and the membrane system is less polluted. The COD of the water produced by the ultrafiltration unit of this embodiment is less than 150 mg / L, and the hardness can be calculated based on the concentrations of calcium ions and magnesium ions, and the hardness is less than 100 mg / L. Silica and fluoride ions are both controlled within 20 mg / L, and the water produced by the ultrafiltration unit meets the water inlet standards of secondary membrane systems such as high-pressure reverse osmosis membrane systems and high-pressure nanofiltration membrane systems.

[0060] It should be noted that references to "one embodiment", "an embodiment", "a specific embodiment", "some embodiments", etc. in the specification only indicate that the described embodiment may include a particular feature, structure or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. In addition, when a particular feature, structure or characteristic is described in conjunction with an embodiment, whether or not explicitly described, it is within the knowledge of a person skilled in the relevant art to implement such feature, structure or characteristic in conjunction with other embodiments.

[0061] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description.

[0062] It should also be noted that, although the present invention has been disclosed as a preferred embodiment, the above embodiment is not intended to limit the present invention. For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

[0063] It should also be understood that, unless otherwise specified or indicated, the terms "first", "second", "third", etc. in the specification are merely used to distinguish between the various components, elements, steps, etc. in the specification, and are not used to indicate the logical relationship or sequential relationship between the various components, elements, steps, etc.

[0064] It should also be recognized that the terms described herein are only used to describe specific embodiments and are not intended to limit the scope of the invention. It should be noted that the singular forms "a" and "an" used herein and in the appended claims include plural references unless the context clearly indicates otherwise. For example, a reference to "a step" or "a device" means a reference to one or more steps or devices, and may include secondary steps and secondary devices. All conjunctions used should be understood in the broadest sense. And, the word "or" should be understood to have the definition of a logical "or", rather than a logical "exclusive or", unless the context clearly indicates otherwise. In addition, the implementation of the method and / or device in the embodiments of the present invention may include performing the selected task manually, automatically, or in combination.

Claims

1. A membrane concentration pretreatment system, characterized in that: It includes an activated carbon adsorption unit, a silicon removal and fluorine removal unit, a softening and hardness removal unit and an ultrafiltration unit which are sequentially connected in series through pipelines; The desiliconization and defluorination unit comprises a desiliconization reaction chamber, a defluorination reaction chamber and a first precipitation component which are connected in sequence, and the first precipitation component is connected to the softening and dehardening unit through a pipeline; The softening and hardness removal unit comprises a hardness removal reaction chamber and a second precipitation component which are connected in sequence, and the second precipitation component is connected to the ultrafiltration unit through a pipeline.

2. The membrane concentration pretreatment system according to claim 1, characterized in that: The activated carbon adsorption unit includes a first reflux pipe, an activated carbon adsorption tower and an activated carbon replenishing device. The activated carbon replenishing device is used to replenish activated carbon to the activated carbon adsorption tower. The first reflux pipe connects the inlet and outlet of the activated carbon adsorption tower. When the COD concentration of the effluent from the activated carbon adsorption tower exceeds a first preset value, the effluent from the activated carbon adsorption tower returns to the inlet of the activated carbon adsorption tower through the first reflux pipe for reprocessing.

3. The membrane concentration pretreatment system according to claim 2, characterized in that: The activated carbon replenishing device includes an activated carbon regeneration component and an activated carbon replenishing component. The activated carbon regeneration component is used to receive the activated carbon discharged from the activated carbon adsorption tower and regenerate the activated carbon, and to transport the regenerated activated carbon to the activated carbon adsorption tower. The activated carbon replenishing component is used to replenish activated carbon to the activated carbon adsorption tower through a pipeline.

4. The membrane concentration pretreatment system according to claim 1, characterized in that: The silicon removal and fluorine removal unit includes a first pH adjustment chamber connected to the silicon removal reaction chamber, and the first pH adjustment chamber is connected to the outlet of the activated carbon adsorption unit; the softening and hardness removal unit includes a second pH adjustment chamber connected to the hardness removal reaction chamber, and the second pH adjustment chamber is connected to the water outlet of the first precipitation component; the silicon removal and fluorine removal unit includes a sodium aluminate addition component and an aluminum sulfate addition component, the addition port of the sodium aluminate addition component leads to the silicon removal reaction chamber, and the addition port of the aluminum sulfate addition component leads to the fluorine removal reaction chamber; the softening and hardness removal unit includes a sodium carbonate addition component, and the addition port of the sodium carbonate addition component leads to the hardness removal reaction chamber.

5. The membrane concentration pretreatment system according to claim 1, characterized in that: The first sedimentation component includes a first flocculation chamber and a first sedimentation chamber that are connected, the first flocculation chamber is connected to the defluorination reaction chamber, and the first sedimentation chamber is connected to the softening and hardness removal unit through a pipeline, which is used to transport the effluent of the first sedimentation chamber to the softening and hardness removal unit; the second sedimentation component includes a second flocculation chamber and a second sedimentation chamber that are connected, the second flocculation chamber is connected to the defluorination reaction chamber, and the second sedimentation chamber is connected to the ultrafiltration unit through a pipeline, which is used to transport the effluent of the second sedimentation chamber to the ultrafiltration unit.

6. The membrane concentration pretreatment system according to claim 1, characterized in that: The membrane concentration pretreatment system includes a sludge treatment unit, which includes a sludge concentration tank. The sludge concentration tank is connected to the first precipitation component and the second precipitation component through pipelines, respectively, for receiving and treating the sludge discharged from the first precipitation component and the second precipitation component.

7. The membrane concentration pretreatment system according to claim 6, characterized in that: The sludge concentration tank is communicated with the silicon removal and fluorine removal unit, so that the supernatant of the sludge concentration tank is transported to the silicon removal and fluorine removal unit for silicon removal and fluorine removal treatment.

8. The membrane concentration pretreatment system according to claim 1, characterized in that: The ultrafiltration unit has a water outlet and a concentrate outlet. The concentrate outlet of the ultrafiltration unit is connected to the desiliconization and defluorination unit through a pipeline, so that the concentrate of the ultrafiltration unit is transported to the desiliconization and defluorination unit for desiliconization and defluorination treatment. The water outlet of the ultrafiltration unit is used to connect with the back-end membrane system.

9. A membrane concentration pretreatment method, applied to the membrane concentration pretreatment system according to any one of claims 1 to 8, characterized in that: include: The wastewater is sequentially transported to the activated carbon adsorption unit, the silicon and fluorine removal unit, the softening and hardness removal unit and the ultrafiltration unit for treatment; Wherein, when the COD concentration of the effluent from the activated carbon adsorption unit exceeds a first preset value, the effluent from the activated carbon adsorption unit is transported to the inlet of the activated carbon adsorption unit for reprocessing; When the silica concentration of the effluent from the silicon removal and fluorine removal unit exceeds a second preset value or the fluorine ion concentration exceeds a third preset value, the effluent from the silicon removal and fluorine removal unit is transported to the inlet of the silicon removal and fluorine removal unit for reprocessing; When the hardness of the outlet water of the softening and hardness-removing unit exceeds a fourth preset value, the outlet water of the softening and hardness-removing unit is transported to the inlet of the softening and hardness-removing unit for reprocessing.

10. The membrane concentration pretreatment method according to claim 9, characterized in that: The pH value of the influent entering the desiliconization reaction chamber is adjusted to 8-9, sodium aluminate is added to the desiliconization reaction chamber, and aluminum sulfate is added to the defluorination reaction chamber; the pH value of the influent entering the hardness removal reaction chamber is adjusted to 10-12, and sodium carbonate is added to the hardness removal reaction chamber.

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