Synchronous hardness and silicon removal process and system for wastewater

Abstract

The invention discloses a synchronous hardness and silicon removal process and system for wastewater, and the process comprises the following steps: S1, silicon removal treatment: conveying to-be-treated wastewater to a silicon removal area, adding a silicon removal agent and a pH regulator, and carrying out silicon removal treatment; s2, hardness removal treatment: conveying the effluent subjected to silicon removal treatment to a hardness removal area, and adding a hardness removal agent for hardness removal treatment; s3, flocculation treatment: conveying the effluent subjected to hardness removal treatment to a flocculation zone, and adding a flocculant for flocculation treatment; and S4, precipitation treatment: enabling the effluent subjected to flocculation treatment to overflow into a precipitation area for precipitation. The total hardness and the silicon dioxide concentration in water are reduced by adding chemical agents, the requirement that effluent enters back-end reverse osmosis can be met, the method can be well applied to a pretreatment process for preparing ultrapure water by recycling reclaimed water in the new energy industry, the scaling problem of membrane equipment, pipelines and an evaporation crystallizer can be avoided, and the water quality is improved. The long-term stable operation of the ultrapure water preparation process is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of ultrapure water preparation, and in particular to a wastewater simultaneous hardness and silicon removal process and system. Background Art

[0002] In recent years, with the increasing scarcity of resources and the increasing awareness of environmental protection among the people, not only are higher requirements placed on water quality indicators, but some processes in the previous preparation of ultrapure water that cause water waste and environmental pollution must be innovated. These have promoted the continuous development of ultrapure water preparation technology.

[0003] In the conventional preparation process, raw water is pretreated and then treated with reverse osmosis, EDI and polishing resin to prepare ultrapure water. Reverse osmosis, EDI and polishing resin have high requirements for the quality of influent water, but raw water often contains calcium, magnesium ions and silica, which will cause scaling problems in membrane equipment and pipelines. The scale is difficult to completely remove. If the raw water enters the reverse osmosis system directly without pretreatment, the long-term operation will reduce the desalination rate of the reverse osmosis membrane. The effect of pretreatment will directly affect the efficiency and life of membrane concentration. Therefore, in order to ensure the high efficiency of the ultrapure water system, hardness and silica must be effectively removed in the pretreatment part. At present, the hardness and silicon removal technologies include dosing coagulation technology, membrane treatment technology, electrochemical technology and ion exchange resin technology.

[0004] Chemical coagulation technology is currently widely used in industrial wastewater treatment. It mainly refers to adding chemical agents to wastewater to generate CaCO based on the solubility product principle. 3 Mg(OH) 2 and silicate precipitation, and then flocculation and sedimentation are used to achieve the purpose of hardness and silicon removal. As a wastewater treatment technology that has developed rapidly in recent years, membrane treatment has been widely used to remove pollutants such as inorganic colloids, soluble organic matter and heavy metals in wastewater. Such as nanofiltration (NF) and ultrafiltration (UF), the main characteristics of nanofiltration and ultrafiltration membranes are low retention rate for monovalent ions, high retention rate for divalent ions, and large membrane flux. However, the equipment investment and operating costs are high, and the technical requirements for operation are high. Electrochemical hardness and silicon removal technology is mainly divided into electrochemical precipitation and electrocoagulation. The basic principle of electrochemical precipitation is to release OH through the reduction reaction of water and oxygen -, creating a high pH condition around the cathode to remove hardness. Electrochemical precipitation has been widely reported, but because of its large cathode area requirements and complex surface cleaning, the application of this technology in industry is very limited. The principle of ion exchange resin technology for removing hardness and silicon is simple, mainly because the resin contains a large number of special functional groups. These functional groups have the ability to exchange with calcium, magnesium ions and silica in wastewater. According to the type of functional groups contained, it can be divided into cation exchange resin and anion exchange resin, and according to its skeleton structure, it can be divided into macroporous resin and gel resin. The effluent from ion exchange resin technology is of good quality and will not cause secondary water pollution, but its investment and operating costs are relatively high, and the operating conditions are demanding. Compared with the above treatment methods, the dosing coagulation technology has low cost, simple operation and can be applied to occasions with different requirements for deep treatment.

[0005] The hardness (Ca 2+ Mg 2+ ) is a major problem in industrial applications. Common scaling compounds include CaCO 3 、CaSO 4 and Mg(OH) 2 Acidification of wastewater to reduce alkalinity can prevent the formation of Ca 2+ Mg 2+ precipitate, but acid treatment may lead to more serious SiO 2 Scaling problem. SiO in high-salinity wastewater 2 The main form is Si a (monosilicic acid and dimerized silicic acid), Si b (oligosilicic acid) and Si c (High polysilicic acid and inactive silicon). When pH <7, SiO in wastewater 2 Mainly high polysilicic acid [(H 2 SO 3 ) n ] form, high polysilicic acid can aggregate and deposit on the film surface, and some SiO 2 It can also polymerize on the membrane surface to form an amorphous pollution layer; when the wastewater pH>7, SiO 2 Scaling problem also exists. SiO in wastewater 2 Mainly silicate ions (SiO 3 2- ) exists in the form of SiO 3 2- will react with metal cations (such as Ca 2+ Mg 2+ 、Al 3+ , Fe 3+) reacts to form metal silicate scale. Silica scale is difficult to completely remove from the reverse osmosis membrane, which eventually leads to deterioration of wastewater treatment system performance, such as reduced reverse osmosis efficiency and shortened system operating life.

[0006] Therefore, it is necessary to improve the existing technology to provide a reliable wastewater treatment process for application in the pretreatment of preparing ultrapure water. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a wastewater simultaneous hardness and silicon removal process and system in view of the deficiencies in the above-mentioned prior art.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is: In a first aspect of the present invention, a process for simultaneous hardness and silicon removal from wastewater is provided, comprising the following steps:

[0009] S1. Silicon removal treatment:

[0010] The wastewater to be treated is transported to a desiliconization area, and a desiliconization agent and a pH regulator are added for desiliconization treatment, wherein the desiliconization agent is at least one of magnesium chloride, magnesium oxide, lime, and sodium aluminate;

[0011] S2, hardness removal:

[0012] The effluent after silicon removal treatment is transported to a de-hardening area, and a de-hardening agent is added for de-hardening treatment; the de-hardening agent is at least one of sodium carbonate and polyaluminium chloride (PAC);

[0013] S3, flocculation treatment:

[0014] The effluent after hardness removal treatment is transported to the flocculation area and flocculants are added for flocculation treatment;

[0015] S4, precipitation treatment:

[0016] The effluent after flocculation treatment overflows into the sedimentation area for sedimentation. Part of the sludge obtained at the bottom of the sedimentation area flows back to the flocculation area, and the remaining part enters the sludge concentration area for concentration and then is discharged. The overflow water from the sedimentation area is discharged as treated clean water.

[0017] Preferably, in step S1, the mass ratio of the amount of silicon removal agent added to the silicon dioxide content in the sewage is (2-4):1;

[0018] In step S1, the pH value is adjusted to 8-9, and the pH adjuster used is an acid or a base, the acid is hydrochloric acid, and the base is at least one of sodium hydroxide and potassium hydroxide;

[0019] The time for the silicon removal treatment in step S1 is 20-40 minutes, and continuous stirring is maintained during the treatment.

[0020] Preferably, the molar ratio of the amount of the hardness removal agent added in step S2 to the total amount of calcium and magnesium in the sewage is (1.5-2):1;

[0021] The time for the hardness removal treatment in step S2 is 5-30 minutes, and continuous stirring is maintained during the treatment.

[0022] Preferably, the flocculant added in step S3 is PAM, and the dosage is 1-2 mg / L.

[0023] The precipitation time in step S4 is 5-10 min.

[0024] Preferably, the wastewater simultaneous hardness and silicon removal process comprises the following steps:

[0025] S1. Silicon removal treatment:

[0026] The wastewater to be treated is transported to the desiliconization area, and continuously stirred. Sodium aluminate is added. The mass ratio of the amount of sodium aluminate added to the silica content in the wastewater is (2-4):1. A pH regulator is added to adjust the pH value of the wastewater to 8-9, and the residence time of the wastewater in the desiliconization area is 20-40 minutes.

[0027] S2, hardness removal:

[0028] The wastewater after silicon removal treatment is transported to the hardness removal area, kept stirred, and sodium carbonate is added for hardness removal treatment. The molar ratio of the amount of sodium carbonate added to the total amount of calcium and magnesium in the wastewater is (1.5-2):1, so that the residence time of the wastewater in the silicon removal area is 5-30 minutes;

[0029] S3, flocculation treatment:

[0030] The effluent after hardness removal treatment is transported to the flocculation area, kept stirred, and flocculant PAM is added for flocculation treatment. The dosage of PAM is 1-2 mg / L;

[0031] S4. Sedimentation treatment:

[0032] The effluent after flocculation treatment overflows into the sedimentation area for sedimentation. The water stays in the sedimentation area for 5-10 minutes. Part of the sludge obtained at the bottom of the sedimentation area flows back to the flocculation area, and the remaining part enters the sludge concentration area for concentration and then discharged. The overflow water from the sedimentation area is discharged as treated clean water.

[0033] In a second aspect of the present invention, a wastewater simultaneous hardness and silicon removal system is provided, which uses the above-mentioned process to carry out wastewater simultaneous hardness and silicon removal treatment, and the system comprises:

[0034] A desiliconization subsystem, which uses the method of step S1 to remove silicon from the wastewater to be treated;

[0035] The hardness removal subsystem uses the method of step S2 to remove hardness from the effluent of the silicon removal subsystem;

[0036] A flocculation subsystem, which uses the method of step S3 to flocculate the effluent of the hardness removal subsystem;

[0037] and a sedimentation subsystem, which uses the method of step S4 to perform sedimentation treatment on the effluent of the flocculation subsystem.

[0038] Preferably, the desiliconization subsystem comprises a desiliconization container, a desiliconization stirring device arranged in the desiliconization container, and a desiliconization water outlet pipe arranged at the bottom of the desiliconization container. The desiliconization container is provided with a water inlet, a first dosing port, and a second dosing port. The desiliconization container is also provided with a pH meter. The first dosing port and the second dosing port are used to add a desiliconization agent and a pH adjuster, respectively.

[0039] Preferably, the hardness removal subsystem includes a hardness removal container, a hardness removal stirring device arranged in the hardness removal container, a guide tube is arranged inside the hardness removal container, the hardness removal stirring device is arranged inside the guide tube, and the silicon removal water outlet pipe is connected to the guide tube; a third dosing port for adding a hardness removal agent is arranged on the hardness removal container, and a hardness removal water outlet pipe is arranged at the bottom of the hardness removal container; an inverted triangle guide plate that can move up and down is arranged inside the guide tube.

[0040] Preferably, the flocculation subsystem includes a flocculation container and a flocculation stirring device arranged in the flocculation container. The flocculation container is provided with a fourth dosing port for adding flocculant. The flocculation container is also provided with a flocculation overflow port. The hard water removal outlet pipe is connected to the bottom of the flocculation container.

[0041] Preferably, the sedimentation subsystem comprises a sedimentation container, a scraper device disposed in the sedimentation container, the flocculation overflow port is connected to the sedimentation container, and the scraper device comprises a scraper motor, a scraper stirring shaft connected to the scraper motor, and a scraper plate connected to the scraper stirring shaft and capable of being raised and lowered;

[0042] The bottom of the sedimentation container is connected to a sludge return pipe, the other end of the sedimentation container is connected to the bottom of the flocculation container, and the sludge return pipe is provided with a sludge return pump;

[0043] The upper part of the sedimentation container is provided with a clean water outlet, the middle part of the bottom is provided with a mud outlet, the lower part of the mud outlet is provided with a sludge concentration area, the sludge concentration area is connected with a mud discharge pipe, and the mud discharge pipe is provided with a sludge discharge pump.

[0044] The beneficial effects of the present invention are:

[0045] The present invention provides a wastewater simultaneous hardness and silicon removal process and system, which utilizes the addition of chemical agents to reduce the total hardness and silicon dioxide concentration in the water, and can meet the requirements for the effluent to enter the back-end reverse osmosis. The present invention can be well applied to the pretreatment process for preparing ultrapure water by recycling reclaimed water in the new energy industry. The present invention can avoid the scaling problem of membrane equipment, pipelines and evaporation crystallizers, and ensure the long-term stable operation of the ultrapure water preparation process. The process flow of the present invention is short, the effluent water quality is stable, and the effluent water fully meets the various water quality requirements for entering the back-end reverse osmosis desalination, and has a good prospect for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic structural diagram of the wastewater simultaneous hardness and silicon removal system of the present invention.

[0047] Description of reference numerals:

[0048] 1—silicon removal subsystem; 11—silicon removal container; 12—silicon removal stirring device; 13—silicon removal water outlet pipe; 14—water inlet; 15—first dosing port; 16—second dosing port; 17—pH value meter; 18—silicon removal overflow port; 121—stirring motor; 122—stirring shaft; 123—stirring paddle;

[0049] 2—hardness removal subsystem; 21—hardness removal container; 22—hardness removal stirring device; 23—flow guide tube; 24—third dosing port; 25—hardness removal water outlet pipe; 26—hardness removal overflow port; 231—inverted triangle guide plate;

[0050] 3—flocculation subsystem; 31—flocculation container; 32—flocculation stirring device; 33—fourth dosing port; 34—flocculation overflow port;

[0051] 4—precipitation subsystem; 41—precipitation container; 42—sludge scraper device; 43—sludge return pipe; 44—sludge return pump; 45—clean water outlet; 46—sludge outlet; 47—sludge concentration area; 48—sludge discharge pipe; 49—sludge external discharge pump; 421—sludge scraper motor; 422—sludge scraper stirring shaft; 423—sludge scraper plate. DETAILED DESCRIPTION

[0052] The present invention is further described in detail below in conjunction with embodiments so that those skilled in the art can implement the invention with reference to the description.

[0053] It should be understood that the terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

[0054] The test methods used in the following examples are conventional methods unless otherwise specified. The materials and reagents used in the following examples are all commercially available unless otherwise specified. In the following examples, if no specific conditions are specified, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, if the manufacturer is not specified, are all conventional products that can be purchased commercially.

[0055] The present invention provides a wastewater simultaneous hardness and silicon removal process, comprising the following steps:

[0056] S1. Silicon removal treatment:

[0057] The wastewater to be treated is transported to a desiliconization area, and a desiliconization agent and a pH regulator are added for desiliconization treatment, wherein the desiliconization agent is at least one of magnesium chloride, magnesium oxide, lime, and sodium aluminate;

[0058] S2, hardness removal:

[0059] The effluent after silicon removal treatment is transported to a de-hardening area, and a de-hardening agent is added for de-hardening treatment; the de-hardening agent is at least one of sodium carbonate and polyaluminium chloride (PAC);

[0060] S3, flocculation treatment:

[0061] The effluent after hardness removal treatment is transported to the flocculation area and flocculants are added for flocculation treatment;

[0062] S4, precipitation treatment:

[0063] The effluent after flocculation treatment overflows into the sedimentation area for sedimentation. Part of the sludge obtained at the bottom of the sedimentation area is returned to the flocculation area, and the remaining part enters the sludge concentration area 47 for concentration and then discharged. The overflow water from the sedimentation area is discharged as treated clean water.

[0064] In a preferred embodiment, in step S1, the mass ratio of the amount of silicon removal agent added to the silicon dioxide content in the sewage is (2-4):1.

[0065] In a preferred embodiment, in step S1, the pH value is adjusted to 8-9, and the pH adjuster used is an acid or a base, the acid is hydrochloric acid, and the base is at least one of sodium hydroxide and potassium hydroxide.

[0066] In a preferred embodiment, the desiliconization treatment time in step S1 is 20-40 minutes, and continuous stirring is maintained during the treatment.

[0067] In a preferred embodiment, the molar ratio of the amount of hardness removal agent added in step S2 to the total amount of calcium and magnesium in the sewage is (1.5-2):1.

[0068] In a preferred embodiment, the hardness removal treatment in step S2 lasts for 5-30 minutes, and continuous stirring is maintained during the treatment.

[0069] In a preferred embodiment, the flocculant added in step S3 is PAM, and the dosage is 1-2 mg / L.

[0070] In a preferred embodiment, the precipitation time in step S4 is 5-10 min.

[0071] In a preferred embodiment, the wastewater simultaneous hardness and silicon removal process comprises the following steps:

[0072] S1. Silicon removal treatment:

[0073] The wastewater to be treated is transported to the desiliconization area, and continuously stirred. Sodium aluminate is added. The mass ratio of the amount of sodium aluminate added to the silica content in the wastewater is (2-4):1. A pH regulator is added to adjust the pH value of the wastewater to 8-9, and the residence time of the wastewater in the desiliconization area is 20-40 minutes.

[0074] S2, hardness removal:

[0075] The wastewater after silicon removal treatment is transported to the hardness removal area, kept stirred, and sodium carbonate is added for hardness removal treatment. The molar ratio of the amount of sodium carbonate added to the total amount of calcium and magnesium in the wastewater is (1.5-2):1, so that the residence time of the wastewater in the silicon removal area is 5-30 minutes;

[0076] S3, flocculation treatment:

[0077] The effluent after hardness removal treatment is transported to the flocculation area, kept stirred, and flocculant PAM is added for flocculation treatment. The dosage of PAM is 1-2 mg / L;

[0078] S4. Sedimentation treatment:

[0079] The effluent after flocculation treatment overflows into the sedimentation area for sedimentation. The water stays in the sedimentation area for 5-10 minutes. Part of the sludge obtained at the bottom of the sedimentation area flows back to the flocculation area, and the remaining part enters the sludge concentration area 47 for concentration and then discharged. The overflow water from the sedimentation area is discharged as treated clean water.

[0080] The present invention also provides a wastewater simultaneous hardness and silicon removal system, which uses the above process to carry out wastewater simultaneous hardness and silicon removal treatment, and the system comprises:

[0081] A silicon removal subsystem 1, which uses the method of step S1 to remove silicon from the wastewater to be treated;

[0082] The hardness removal subsystem 2 uses the method of step S2 to remove hardness from the effluent of the silicon removal subsystem 1;

[0083] Flocculation subsystem 3, which uses the method of step S3 to flocculate the effluent of hardness removal subsystem 2;

[0084] and a sedimentation subsystem 4, which uses the method of step S4 to perform sedimentation treatment on the effluent of the flocculation subsystem 3.

[0085] 1. The silicon removal subsystem 1 includes a silicon removal container 11, a silicon removal stirring device 12 arranged in the silicon removal container 11, and a silicon removal water outlet pipe 13 arranged at the bottom of the silicon removal container 11. The silicon removal container 11 is provided with a water inlet 14, a first dosing port 15, and a second dosing port 16. The silicon removal container 11 is also provided with a pH meter 17 for monitoring the pH value. The first dosing port 15 and the second dosing port 16 are used to add a silicon removal agent and a pH adjuster respectively.

[0086] The wastewater to be treated is transported to the desiliconization area and enters the desiliconization container 11. Under the rotating stirring action of the desiliconization stirring device 12, it is fully mixed with the desiliconization agent added from the first dosing port 15 to remove the soluble silicon concentration in the water. At the same time, the pH in the water is adjusted by adding a pH adjuster from the second dosing port 16, so that the residence time of the sewage in the desiliconization container 11 is 20-40 minutes.

[0087] 2. The hardness removal subsystem 2 includes a hardness removal container 21, a hardness removal stirring device 22 disposed in the hardness removal container 21, a guide tube 23 disposed inside the hardness removal container 21, the hardness removal stirring device 22 disposed inside the guide tube 23, and a silicon removal outlet pipe 13 connected to the guide tube 23; a third dosing port 24 for adding a hardness removal agent is disposed on the hardness removal container 21, and a hardness removal outlet pipe 25 is disposed at the bottom of the hardness removal container 21. An inverted triangular guide plate 231 that can move up and down is disposed inside the guide tube 23, and the inverted triangular guide plate 231 can promote the mixing of water and the agent by moving up and down.

[0088] The effluent from the desiliconization subsystem 1 enters the guide tube 23 of the dehardness removal container 21 through the desiliconization outlet pipe 13. Under the rotating stirring action of the dehardness removal stirring device 22, it is fully mixed with the dehardness removal agent added from the third dosing port 24 to reduce the hardness of the water, so that the residence time of the sewage in the dehardness removal container 21 is 5-30 minutes.

[0089] 3. The flocculation subsystem 3 includes a flocculation container 31 and a flocculation stirring device 32 arranged in the flocculation container 31. The flocculation container 31 is provided with a fourth dosing port 33 for adding flocculants. The flocculation container 31 is also provided with a flocculation overflow port 34. The hard water outlet pipe 25 is connected to the bottom of the flocculation container 31.

[0090] The effluent from the hardness removal subsystem 2 enters the flocculation container 31 through the hardness removal outlet pipe 25, and is mixed with the flocculant PAM added from the fourth dosing port 33 for flocculation under the rotating stirring action of the flocculation stirring device 32. The dosage is 1-2 mg / L, which is adjusted according to the alum floc effect in the flocculation zone.

[0091] 4. The sedimentation subsystem 4 includes a sedimentation container 41, a scraper device 42 disposed in the sedimentation container 41, the flocculation overflow port 34 is connected to the sedimentation container 41, and the scraper device 42 includes a scraper motor 421, a scraper stirring shaft 422 connected to the scraper motor 421, and a scraper plate 423 connected to the scraper stirring shaft 422 and capable of being raised and lowered;

[0092] The bottom of the sedimentation container 41 is connected to a sludge return pipe 43, and the other end of the sedimentation container 41 is connected to the bottom of the flocculation container 31. The sludge return pipe 43 is provided with a sludge return pump 44;

[0093] The sedimentation container 41 is provided with a clean water outlet 45 at the top and a mud outlet 46 at the middle of the bottom. A sludge concentration area 47 is provided below the mud outlet 46. The sludge concentration area 47 is connected to a mud discharge pipe 48. A sludge discharge pump 49 is provided on the mud discharge pipe 48.

[0094] The effluent of the flocculation subsystem 3 enters the sedimentation container 41 from the overflow port. The residence time of the water in the sedimentation container 41 is 5-10 minutes. The bottom of the sedimentation container 41 returns part of the sludge to the bottom of the flocculation container 31 through the sludge return pump 44. The sludge at the bottom of the sedimentation container 41 enters the sludge concentration area 47 for concentration and then is discharged for landfill or biocomposting and other rational utilization. The effluent discharged from the clean water outlet 45 at the top of the sedimentation container 41 can directly enter the rear-end reverse osmosis system for further desalination to produce ultrapure water.

[0095] In the present invention, the desiliconizing stirring device 12, the dehardening stirring device 22, and the flocculating stirring device 32 have the same structure, and all include a stirring motor 121, a stirring shaft 122 drivingly connected to the stirring motor 121, and a stirring paddle 123 connected to the stirring shaft 122 ( Figure 1 The desiliconizing stirring device 12 is used as an example for illustration), the stirring paddle 123 can rotate left and right, and can also rotate up and down, so that the water and the reagent can be fully mixed and reacted, thereby improving the efficiency of hardness and silicon removal.

[0096] In the present invention, the upper parts of the silicon removal container 11 and the hardness removal container 21 are respectively provided with a silicon removal overflow port 18 and a hardness removal overflow port 26 (generally, water does not flow out of the silicon removal overflow port 18 and the hardness removal overflow port 26, and their function is to prevent short-flow of pool water in each area), the water inlet 14 is higher than the silicon removal overflow port 18, the silicon removal overflow port 18 is higher than the hardness removal overflow port 26, the hardness removal overflow port 26 is higher than the flocculation overflow port 34, and the flocculation overflow port 34 is higher than the clean water outlet. This arrangement can prevent short-flow of pool water in each area.

[0097] The above is the overall concept of the present invention, and detailed embodiments and comparative examples are provided below on the basis of the overall concept of the present invention to further illustrate the present invention.

[0098] Example 1

[0099] A wastewater simultaneous hardness and silicon removal process, which uses the above system for water treatment, specifically comprises the following steps:

[0100] S1. The wastewater to be treated (recycled water) is transported to the desiliconization area and enters the desiliconization container 11. Under the rotating stirring action of the desiliconization stirring device 12, it is fully mixed with the desiliconization agent added from the first dosing port 15 to remove the soluble silicon concentration in the water. The desiliconization agent is sodium aluminate. The mass ratio of the amount of sodium aluminate added to the silica concentration in the wastewater is 3:1. At the same time, the pH of the water is adjusted to 8-9 by adding a pH adjuster (hydrochloric acid) from the second dosing port 16, so that the residence time of the sewage in the desiliconization container 11 is 30 minutes.

[0101] S2. The effluent from the silicon removal subsystem 1 enters the guide tube 23 of the hardness removal container 21 through the silicon removal outlet pipe 13. Under the rotating stirring action of the hardness removal stirring device 22, it is fully mixed with the hardness removal agent added from the third dosing port 24 to reduce the hardness of the water. The hardness removal agent is sodium carbonate. The molar ratio of the amount of sodium carbonate added to the total amount of calcium and magnesium in the sewage is 1.5:1, so that the sewage stays in the hardness removal container 21 for 20 minutes.

[0102] S3. The effluent from the hardness removal subsystem 2 enters the flocculation container 31 through the hardness removal outlet pipe 25. Under the rotation and stirring action of the flocculation stirring device 32, it is mixed with the flocculant PAM added from the fourth dosing port 33 for flocculation. The dosing amount is 2 mg / L.

[0103] S4. The effluent from the flocculation subsystem 3 enters the sedimentation container 41 from the overflow port. The water stays in the sedimentation container 41 for 10 minutes. The bottom of the sedimentation container 41 returns part of the sludge to the bottom of the flocculation container 31 through the sludge return pump 44. The sludge at the bottom of the sedimentation container 41 enters the sludge concentration area 47 for concentration and then is discharged for landfill or biocomposting and other rational utilization. The effluent discharged from the clean water outlet 45 on the top of the sedimentation container 41 can directly enter the back-end reverse osmosis system for further desalination to produce ultrapure water according to the water quality.

[0104] Example 2

[0105] A wastewater simultaneous hardness and silicon removal process, which uses the above system for water treatment, specifically comprises the following steps:

[0106] S1. The wastewater to be treated (recycled water) is transported to the desiliconization area and enters the desiliconization container 11. Under the rotating stirring action of the desiliconization stirring device 12, it is fully mixed with the desiliconization agent added from the first dosing port 15 to remove the soluble silicon concentration in the water. The desiliconization agent is sodium aluminate. The mass ratio of the amount of sodium aluminate added to the silica concentration in the wastewater is 2:1. At the same time, the pH regulator (hydrochloric acid) is added from the second dosing port 16 to adjust the pH in the water to 8-9, so that the residence time of the sewage in the desiliconization container 11 is 30 minutes.

[0107] S2. The effluent from the silicon removal subsystem 1 enters the guide tube 23 of the hardness removal container 21 through the silicon removal outlet pipe 13. Under the rotating stirring action of the hardness removal stirring device 22, it is fully mixed with the hardness removal agent added from the third dosing port 24 to reduce the hardness of the water. The hardness removal agent is sodium carbonate. The molar ratio of the amount of sodium carbonate added to the total amount of calcium and magnesium in the sewage is 2:1, so that the sewage stays in the hardness removal container 21 for 20 minutes.

[0108] S3. The effluent from the hardness removal subsystem 2 enters the flocculation container 31 through the hardness removal outlet pipe 25. Under the rotation and stirring action of the flocculation stirring device 32, it is mixed with the flocculant PAM added from the fourth dosing port 33 for flocculation. The dosing amount is 2 mg / L.

[0109] S4. The effluent from the flocculation subsystem 3 enters the sedimentation container 41 from the overflow port. The water stays in the sedimentation container 41 for 10 minutes. The bottom of the sedimentation container 41 returns part of the sludge to the bottom of the flocculation container 31 through the sludge return pump 44. The sludge at the bottom of the sedimentation container 41 enters the sludge concentration area 47 for concentration and then is discharged for landfill or biocomposting and other rational utilization. The effluent discharged from the clean water outlet 45 on the top of the sedimentation container 41 can directly enter the back-end reverse osmosis system for further desalination to produce ultrapure water according to the water quality.

[0110] Comparative Example 1

[0111] A wastewater simultaneous hardness and silicon removal process, which uses the above system for water treatment, specifically comprises the following steps:

[0112] S1. The wastewater to be treated (recycled water) is transported to the desiliconization area and enters the desiliconization container 11. Under the rotating stirring action of the desiliconization stirring device 12, it is fully mixed with the desiliconization agent added from the first dosing port 15 to remove the soluble silicon concentration in the water. The desiliconization agent is magnesium chloride. The mass ratio of the amount of magnesium chloride added to the silica concentration in the wastewater is 3:1. At the same time, the pH in the water is adjusted to 10-11 by adding a pH adjuster (sodium hydroxide) from the second dosing port 16, so that the residence time of the sewage in the desiliconization container 11 is 30 minutes.

[0113] S2. The effluent from the silicon removal subsystem 1 enters the guide tube 23 of the hardness removal container 21 through the silicon removal outlet pipe 13. Under the rotating stirring action of the hardness removal stirring device 22, it is fully mixed with the hardness removal agent added from the third dosing port 24 to reduce the hardness of the water. The hardness removal agent is PAC. The molar ratio of the amount of PAC added to the total amount of calcium and magnesium in the sewage is 1.5:1, so that the sewage stays in the hardness removal container 21 for 20 minutes.

[0114] S3. The effluent from the hardness removal subsystem 2 enters the flocculation container 31 through the hardness removal outlet pipe 25. Under the rotation and stirring action of the flocculation stirring device 32, it is mixed with the flocculant PAM added from the fourth dosing port 33 for flocculation. The dosing amount is 2 mg / L.

[0115] S4. The effluent from the flocculation subsystem 3 enters the sedimentation container 41 from the overflow port. The water stays in the sedimentation container 41 for 10 minutes. The bottom of the sedimentation container 41 returns part of the sludge to the bottom of the flocculation container 31 through the sludge return pump 44. The sludge at the bottom of the sedimentation container 41 enters the sludge concentration area 47 for concentration and then is discharged for landfill or biocomposting and other rational utilization. The effluent discharged from the clean water outlet 45 on the top of the sedimentation container 41 can directly enter the back-end reverse osmosis system for further desalination to produce ultrapure water according to the water quality.

[0116] Comparative Example 2

[0117] A wastewater simultaneous hardness and silicon removal process, which uses the above system for water treatment, specifically comprises the following steps:

[0118] S1. The wastewater to be treated (recycled water) is transported to the desiliconization area and enters the desiliconization container 11. Under the rotating stirring action of the desiliconization stirring device 12, it is fully mixed with the desiliconization agent added from the first dosing port 15 to remove the soluble silicon concentration in the water. The desiliconization agent is calcium oxide, and the mass ratio of the amount of calcium oxide added to the silicon dioxide concentration in the wastewater is 3:1. At the same time, the pH of the water is adjusted to 11-12 by adding a pH adjuster (sodium hydroxide) from the second dosing port 16, so that the residence time of the sewage in the desiliconization container 11 is 30 minutes.

[0119] S2. The effluent from the silicon removal subsystem 1 enters the guide tube 23 of the hardness removal container 21 through the silicon removal outlet pipe 13. Under the rotating stirring action of the hardness removal stirring device 22, it is fully mixed with the hardness removal agent added from the third dosing port 24 to reduce the hardness of the water. The hardness removal agent is sodium carbonate. The molar ratio of the amount of sodium carbonate added to the total amount of calcium and magnesium in the sewage is 1.5:1, so that the sewage stays in the hardness removal container 21 for 20 minutes.

[0120] S3. The effluent from the hardness removal subsystem 2 enters the flocculation container 31 through the hardness removal outlet pipe 25. Under the rotation and stirring action of the flocculation stirring device 32, it is mixed with the flocculant PAM added from the fourth dosing port 33 for flocculation. The dosing amount is 2 mg / L.

[0121] S4. The effluent from the flocculation subsystem 3 enters the sedimentation container 41 from the overflow port. The water stays in the sedimentation container 41 for 10 minutes. The bottom of the sedimentation container 41 returns part of the sludge to the bottom of the flocculation container 31 through the sludge return pump 44. The sludge at the bottom of the sedimentation container 41 enters the sludge concentration area 47 for concentration and then is discharged for landfill or biocomposting and other rational utilization. The effluent discharged from the clean water outlet 45 on the top of the sedimentation container 41 can directly enter the back-end reverse osmosis system for further desalination to produce ultrapure water according to the water quality.

[0122] The water quality of the inlet and outlet water in the above embodiments and comparative examples is shown in Table 1 below:

[0123] Table 1

[0124]

[0125]

[0126] The difference between Example 1 and Example 2 is that the dosage of silicon removal and hardness removal agents is different. The dosage of Example 2 is higher than that of Example 1, and the chemical agents at each dosing port and the reaction time of each area are consistent. The reaction pH is adjusted to the pH for the optimal reaction of the hardness removal and silicon removal agents. However, from the perspective of effluent water quality, the higher the dosage of sodium carbonate, the higher the total hardness removal rate, but the higher the dosage of sodium aluminate, the lower the silicon dioxide removal rate.

[0127] The difference between Example 1 and Comparative Examples 1 and 2 is that the chemical agents used for hardness and silicon removal are different, but the dosage of each dosing port and the reaction time of each area are consistent, and the reaction pH is adjusted to the pH for the best reaction of the hardness and silicon removal agent. From the perspective of effluent water quality, the aluminum series silicon removal agent is more effective than the magnesium series and calcium oxide, and the sodium carbonate is much more effective in removing total hardness than PAC. Sodium aluminate can reduce silicon removal from 200 mg / L to 7 mg / L, with an efficiency of up to 96.5%; sodium carbonate can reduce total hardness by Ca 2+ The concentration decreased from 1500mg / L to 24mg / L, Mg 2+ The concentration is reduced from 3000mg / L to 36mg / L, with an efficiency of more than 97%, which is much higher than the efficiency of PAC in removing total hardness. It can completely solve the problem of silicon and Ca in the process of reclaimed water reuse. 2+ Mg 2+ Scaling problem.

[0128] The chemical agents added in Example 1 and Example 2 are reasonable, the effluent is stable, and the amount of chemical agents added is less than that of other processes, especially the desiliconizing agent. According to the silica concentration of the inlet and outlet water quality, the desiliconizing effect of the present invention is obvious, which means that the present invention can obtain better treatment effects while using less agents; and the effluent water quality does not need to adjust the pH and can directly enter the back-end reverse osmosis system for further desalination to produce ultrapure water.

[0129] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to specific details.

Claims

1. A process for simultaneous hardness and silicon removal from wastewater, characterized in that: The following steps are involved: S1. Silicon removal treatment: The wastewater to be treated is transported to a desiliconization area, and a desiliconization agent and a pH regulator are added for desiliconization treatment, wherein the desiliconization agent is at least one of magnesium chloride, magnesium oxide, lime, and sodium aluminate; S2, hardness removal: The effluent after silicon removal treatment is transported to a de-hardening area, and a de-hardening agent is added for de-hardening treatment; the de-hardening agent is at least one of sodium carbonate and polyaluminium chloride (PAC); S3, flocculation treatment: The effluent after hardness removal treatment is transported to the flocculation area and flocculants are added for flocculation treatment; S4, precipitation treatment: The effluent after flocculation treatment overflows into the sedimentation area for sedimentation. Part of the sludge obtained at the bottom of the sedimentation area flows back to the flocculation area, and the remaining part enters the sludge concentration area for concentration and then is discharged. The overflow water from the sedimentation area is discharged as treated clean water.

2. The wastewater simultaneous hardness and silicon removal process according to claim 1, characterized in that: In step S1, the mass ratio of the amount of silicon removal agent added to the silicon dioxide content in the sewage is (2-4): 1; In step S1, the pH value is adjusted to 8-9, and the pH adjuster used is an acid or a base, the acid is hydrochloric acid, and the base is at least one of sodium hydroxide and potassium hydroxide; The time for the silicon removal treatment in step S1 is 20-40 minutes, and continuous stirring is maintained during the treatment.

3. The wastewater simultaneous hardness and silicon removal process according to claim 2, characterized in that: The molar ratio of the amount of the hardness removal agent added in step S2 to the total amount of calcium and magnesium in the sewage is (1.5-2):1; The time for the hardness removal treatment in step S2 is 5-30 minutes, and continuous stirring is maintained during the treatment.

4. The wastewater simultaneous hardness and silicon removal process according to claim 2, characterized in that: The flocculant added in step S3 is PAM, and the dosage is 1-2 mg / L. The precipitation time in step S4 is 5-10 min.

5. The wastewater simultaneous hardness and silicon removal process according to claim 1, characterized in that: The following steps are involved: S1. Silicon removal treatment: The wastewater to be treated is transported to the desiliconization area, and continuously stirred. Sodium aluminate is added. The mass ratio of the amount of sodium aluminate added to the silica content in the wastewater is (2-4):

1. A pH regulator is added to adjust the pH value of the wastewater to 8-9, and the residence time of the wastewater in the desiliconization area is 20-40 minutes. S2, hardness removal: The wastewater after silicon removal treatment is transported to the hardness removal area, kept stirred, and sodium carbonate is added for hardness removal treatment. The molar ratio of the amount of sodium carbonate added to the total amount of calcium and magnesium in the wastewater is (1.5-2):1, so that the residence time of the wastewater in the silicon removal area is 5-30 minutes; S3, flocculation treatment: The effluent after hardness removal treatment is transported to the flocculation area, kept stirred, and flocculant PAM is added for flocculation treatment. The dosage of PAM is 1-2 mg / L; S4, precipitation treatment: The effluent after flocculation treatment overflows into the sedimentation area for sedimentation. The water stays in the sedimentation area for 5-10 minutes. Part of the sludge obtained at the bottom of the sedimentation area flows back to the flocculation area, and the remaining part enters the sludge concentration area for concentration and then discharged. The overflow water from the sedimentation area is discharged as treated clean water.

6. A wastewater simultaneous hardness and silicon removal system, characterized in that: The process described in any one of claims 1 to 5 is used to simultaneously remove hardness and silicon from wastewater. The system comprises: A desiliconization subsystem, which uses the method of step S1 to remove silicon from the wastewater to be treated; The hardness removal subsystem uses the method of step S2 to remove hardness from the effluent of the silicon removal subsystem; A flocculation subsystem, which uses the method of step S3 to flocculate the effluent of the hardness removal subsystem; and a sedimentation subsystem, which uses the method of step S4 to perform sedimentation treatment on the effluent of the flocculation subsystem.

7. The wastewater simultaneous hardness and silicon removal system according to claim 6, characterized in that: The desiliconization subsystem includes a desiliconization container, a desiliconization stirring device arranged in the desiliconization container, and a desiliconization water outlet pipe arranged at the bottom of the desiliconization container. The desiliconization container is provided with a water inlet, a first dosing port, and a second dosing port. The desiliconization container is also provided with a pH meter. The first dosing port and the second dosing port are used to add a desiliconization agent and a pH adjuster, respectively.

8. The wastewater simultaneous hardness and silicon removal system according to claim 7, characterized in that: The hardness removal subsystem includes a hardness removal container, a hardness removal stirring device arranged in the hardness removal container, a guide tube is arranged inside the hardness removal container, the hardness removal stirring device is arranged inside the guide tube, and the silicon removal water outlet pipe is connected to the guide tube; the hardness removal container is provided with a third dosing port for adding a hardness removal agent, and the hardness removal water outlet pipe is provided at the bottom of the hardness removal container; an inverted triangle guide plate that can move up and down is provided inside the guide tube.

9. The wastewater simultaneous hardness and silicon removal system according to claim 8, characterized in that: The flocculation subsystem includes a flocculation container and a flocculation stirring device arranged in the flocculation container. The flocculation container is provided with a fourth dosing port for adding flocculants. The flocculation container is also provided with a flocculation overflow port. The hard water removal outlet pipe is connected to the bottom of the flocculation container.

10. The wastewater simultaneous hardness and silicon removal system according to claim 9, characterized in that: The sedimentation subsystem comprises a sedimentation container, a scraper device arranged in the sedimentation container, the flocculation overflow port is connected to the sedimentation container, and the scraper device comprises a scraper motor, a scraper stirring shaft connected to the scraper motor, and a scraper plate connected to the scraper stirring shaft and capable of being raised and lowered; The bottom of the sedimentation container is connected to a sludge return pipe, the other end of the sedimentation container is connected to the bottom of the flocculation container, and the sludge return pipe is provided with a sludge return pump; The upper part of the sedimentation container is provided with a clean water outlet, the middle part of the bottom is provided with a mud outlet, the lower part of the mud outlet is provided with a sludge concentration area, the sludge concentration area is connected with a mud discharge pipe, and the mud discharge pipe is provided with a sludge discharge pump.

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