Water treatment hardness removal method with pretreatment and deep pretreatment

Abstract

The invention relates to a pretreatment and deep pretreatment water treatment hardness removal method which comprises the following steps: providing an adjusting tank, adding wastewater into the adjusting tank, and pretreating the wastewater in the adjusting tank, so that liquid in the adjusting tank reacts and precipitates; carrying out solid-liquid separation on the wastewater in the regulating tank to obtain a primary reaction solution, adding the primary reaction solution into a reaction tank, carrying out pH regulation on the primary reaction solution in the reaction tank, and adding sodium carbonate into the reaction tank, so that the primary reaction solution in the reaction tank reacts and precipitates; adding the first reaction liquid in the reaction tank into a tubular membrane for solid-liquid separation to obtain a second reaction liquid, intercepting a precipitate after a chemical reaction of the second reaction liquid through the tubular membrane, and removing scaling substances; and adding the separated second reaction liquid into a resin unit to obtain a third reaction liquid, and carrying out hardness removal on the second reaction liquid through the resin unit.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial wastewater treatment, and particularly to a water treatment hard removal method with pretreatment and advanced pretreatment. Background Art

[0002] With the rapid economic development and the progress of industrial production technology, the discharge of industrial wastewater and the treatment of water quality have become more complicated. During the production process, treating and reusing the discharged wastewater is an important way to reduce production costs, and higher requirements for water treatment are put forward to meet the reuse standards. Based on the production purpose of the project, the discharged wastewater is all high-alkali and high-salt wastewater, and efficient hard removal treatment must be carried out to ensure the reuse standards.

[0003] During the industrial wastewater treatment process, due to the presence of calcium and magnesium scaling ions and silicon compounds in the water, equipment scaling and fouling often occur, resulting in increased water treatment energy consumption and reduced treatment efficiency, and at the same time affecting the effluent water quality. The hard removal process is an essential process. The traditional hard removal method is to add lime or sodium hydroxide for chemical precipitation and then filtration. This method has poor treatment effects, while some new methods have strong treatment effects but high costs. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a water treatment hard removal method with pretreatment and advanced pretreatment. First, the wastewater is pretreated, then sodium carbonate is added to react with the substances in the solution and precipitate, then the components that are likely to cause scaling in the subsequent reuse process are effectively removed through a tubular membrane to purify the water quality, and finally the liquid is softened through a resin unit.

[0005] The technical solution to achieve the above purpose is a water treatment hard removal method with pretreatment and advanced pretreatment, including the following steps:

[0006] Provide an adjustment tank, add the wastewater into the adjustment tank, and pretreat the wastewater in the adjustment tank so that the liquid in the adjustment tank reacts and precipitates;

[0007] Perform solid-liquid separation on the wastewater in the adjustment tank to obtain a first reaction liquid, add the first reaction liquid into a reaction tank, adjust the pH of the first reaction liquid in the reaction tank, and add sodium carbonate into the reaction tank so that the first reaction liquid in the reaction tank reacts and precipitates;

[0008] Add the first reaction liquid in the reaction tank into a tubular membrane for solid-liquid separation to obtain a second reaction liquid, intercept the precipitate after the chemical reaction of the second reaction liquid through the tubular membrane, and remove the scaling substances;

[0009] Add the separated second reaction solution to the resin unit to obtain a third reaction solution, and remove hardness from the second reaction solution through the resin unit.

[0010] Further, when pretreating the wastewater, add soda ash lye to the adjustment tank to generate precipitates, and stir the solution in the adjustment tank until no more precipitates are formed.

[0011] Further, after the stirring is completed, add PFS coagulant to the adjustment tank to coagulate the floating substances in the wastewater and generate flocs, and add PAM flocculant to the adjustment tank to coagulate the flocs and form large flocs. After the large flocs settle, discharge the large flocs through a sludge scraper.

[0012] Further, when adjusting the pH of the first reaction solution in the reaction tank, monitor the pH of the liquid in the reaction tank, provide a standard pH value range, add soda ash to the reaction tank, and stir to control the pH value of the liquid in the reaction tank within the pH value range.

[0013] Further, when adding sodium carbonate to the reaction tank, monitor the pH of the liquid in the reaction tank, provide a pH maintenance range, add liquid caustic soda to the reaction tank and stir to keep the pH value of the liquid in the reaction tank within the pH maintenance range.

[0014] Further, after adding sodium carbonate to the reaction tank and generating precipitates, add PFS coagulant to the reaction tank to coagulate the floating substances in the first reaction solution and generate flocs, and add PAM flocculant to the reaction tank to coagulate the flocs and form large flocs. After the large flocs settle, discharge the large flocs through a sludge scraper.

[0015] Further, when the resin unit removes hardness from the second reaction solution, use macroporous weakly acidic acrylic cation resin to remove hardness from the second reaction solution.

[0016] Further, before the resin unit removes hardness from the second reaction solution, add the second reaction solution to the pH callback tank, provide a standard pH value range, adjust and monitor the pH of the liquid in the pH callback tank so that the pH value of the second reaction solution is within the standard pH value range.

[0017] Further, when the resin unit removes hardness from the second reaction solution, provide a standard water temperature range and control the temperature of the second reaction solution within the standard water temperature range.

[0018] Further, after pre-treating the wastewater, a sedimentation tank is provided to perform solid-liquid separation on the wastewater through the sedimentation tank.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] By first pre-treating the wastewater, then reacting and precipitating substances in the solution by adding sodium carbonate, then effectively removing components that are likely to cause scaling in the subsequent reuse process through a tubular membrane to purify the water quality, and finally softening the liquid through a resin unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a flowchart of a water treatment method for removing hardness by pre-treatment plus advanced pre-treatment;

[0022] Legend: 1, regulating tank; 2, reaction tank; 3, concentration tank; 4, tubular membrane; 5, PH callback tank. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0024] Refer to Figure 1 , a water treatment method for removing hardness by pre-treatment plus advanced pre-treatment, comprising the following steps: providing a regulating tank 1, adding wastewater into the regulating tank 1, pre-treating the wastewater in the regulating tank 1 so that the liquid in the regulating tank 1 reacts and precipitates; performing solid-liquid separation on the wastewater in the regulating tank 1 to obtain a first reaction liquid, adding the first reaction liquid into the reaction tank 2, adjusting the PH of the first reaction liquid in the reaction tank 2, and adding sodium carbonate into the reaction tank 2 so that the first reaction liquid in the reaction tank 2 reacts and precipitates; adding the first reaction liquid in the reaction tank 2 into the tubular membrane 4 for solid-liquid separation to obtain a second reaction liquid, intercepting the precipitate after the chemical reaction of the second reaction liquid by the tubular membrane 4, and removing the scaling substances; adding the separated second reaction liquid into the resin unit to obtain a third reaction liquid, and removing hardness from the second reaction liquid through the resin unit.

[0025] In the present invention, a preferred embodiment is: pre-treating the wastewater, adding soda ash solution to the wastewater, adding soda ash to the reaction tank to react with the carbonate hardness in the water to generate CaCO 3 and Mg(OH) 2Precipitation reduces the hardness and alkalinity of water. Sodium carbonate is added, and liquid caustic soda is added to maintain the pH value, controlling the pH value above 10.5. The key is to form calcium carbonate precipitation. It stays for no less than 30 minutes with stirring and pH monitoring, and then enters the tubular membrane 4 (TMF) system. A 0.2μm microfiltration membrane is used to filter the hardness-removing precipitate generated from the front-end treatment. Extreme solid-liquid separation is carried out in the cross-flow mode, with the cross-flow velocity controlled at 3 - 4m / s. The precipitate after the chemical reaction is intercepted to remove scale-forming substances, and then it enters the resin unit. Macroporous weakly acidic acrylic cation exchange resin is used. Through the sodium-type cation exchange resin, the excess Ca 2+ , Mg 2+ in the water is exchanged with Na + in the resin, thereby adsorbing Ca 2+ , Mg 2+ in the water. When exchanging, the water temperature is controlled at 15 - 35°C, and the total hardness of the final effluent water quality is ≤10mg / L.

[0026] Furthermore, when pre-treating the wastewater, soda ash lye is added to the regulating tank 1 to generate precipitates, and the solution in the regulating tank 1 is stirred until no more precipitates are formed. Preferably, for the pre-treatment of wastewater, soda ash lye is added and stirred for reaction, reacting with calcium ions and magnesium ions in the sewage to generate CaCO3 and Mg(OH)2 precipitates. At the same time, silicon dioxide in the water reacts with OH and Mg to generate Mg(OH)2SiO3 precipitates.

[0027] Furthermore, after the stirring is completed, PFS (polyferric sulfate) coagulant is added to the regulating tank 1 to coagulate the floating substances in the wastewater and generate flocs. PAM (polyacrylamide) flocculant is added to the regulating tank to coagulate the flocs and form large floc masses. After the large floc masses precipitate, the large floc masses are discharged by a sludge scraper.

[0028] Furthermore, when adjusting the pH of the first reaction liquid in the reaction tank 2, the pH of the liquid in the reaction tank 2 is monitored, and the standard pH value range is provided. Soda ash is added to the reaction tank 2 and stirred to control the pH value of the liquid in the reaction tank 2 within the pH value range. Preferably, after the pre-treatment is completed, deep pre-treatment is carried out. The incoming water undergoes secondary chemical treatment, enters the reaction tank 2, liquid caustic soda or lime is added, and stirred for reaction. The key is to form magnesium hydroxide precipitates, control the pH at about 11.2, stay for no less than 30 minutes with stirring and pH monitoring.

[0029] Further, when adding sodium carbonate into the reaction tank 2, monitor the pH of the liquid in the reaction tank 2, provide a maintained pH range, add liquid caustic soda into the reaction tank 2 and stir to keep the pH of the liquid in the reaction tank 2 within the maintained pH range. Preferably, add sodium carbonate and add liquid caustic soda to maintain the pH value, control the pH value above 10.5, mainly form calcium carbonate precipitate, stay for no less than 30 minutes and carry out stirring and pH monitoring.

[0030] Further, after adding sodium carbonate into the reaction tank 2 and generating precipitate, add PFS coagulant into the reaction tank 2 to coagulate the floating substances in the first reaction liquid and generate floccules, add PAM flocculant into the reaction tank 2 to coagulate the floccules and form large flocculent masses. After the large flocculent masses precipitate, discharge the large flocculent masses through a sludge scraper.

[0031] Further, when the resin unit removes hardness from the second reaction liquid, use macroporous weakly acidic acrylic cation exchange resin to remove hardness from the second reaction liquid. Preferably, enter the resin unit, use macroporous weakly acidic acrylic cation exchange resin, and through sodium-type cation exchange resin, make the excess Ca 2+ 、Mg 2+ in the water exchange with Na + in the resin, so as to adsorb Ca 2+ 、Mg 2+ in the water. When exchanging, control the water temperature at 15 - 35 °C, and the total hardness of the final effluent quality ≤ 10 mg / L.

[0032] Still further, when entering the tubular membrane 4, supply the liquid to the concentration tank 3 and the tubular membrane 4 through cross-flow water supply and receiving concentrated sludge, maintain the sludge concentration between 2 - 5%, stay for no less than 30 minutes and carry out stirring and liquid level control; enter the tubular membrane 4 (TMF) system, use a 0.2 μm microfiltration membrane to filter the hardness removal precipitate generated by the front-end treatment, carry out extreme solid-liquid separation in the cross-flow mode, control the cross-flow velocity at 3 - 4 m / s, intercept the precipitate after the chemical reaction, and remove the scaling substances.

[0033] Further, before the resin unit removes hardness from the second reaction liquid, add the second reaction liquid into the pH callback tank 5, provide a standard pH range, adjust and monitor the pH of the liquid in the pH callback tank 5 to make the pH of the second reaction liquid within the standard pH range.

[0034] Further, when the resin unit removes hardness from the second reaction liquid, provide a standard water temperature range and control the temperature of the second reaction liquid within the standard water temperature range.

[0035] Further, after pre-treating the wastewater, a sedimentation tank is provided to perform solid-liquid separation on the wastewater through the sedimentation tank.

[0036] The following describes the usage process of a water treatment and hardness removal method with pre-treatment and advanced pre-treatment according to the present invention.

[0037] The incoming wastewater is first pre-treated. The hardness removal in the pre-treatment adopts the high-density sedimentation method. By adding lime / liquid caustic soda to the reaction tank, lime or liquid caustic soda and soda ash are added to the reaction tank to react with the carbonate hardness in the water, generating CaCO 3 and Mg(OH) 2 precipitates, reducing the hardness and alkalinity of the water. At the same time, by adding PFS and PAM, the newly formed CaCO 3 and Mg(OH) 2 precipitates with a large surface area adsorb a large amount of suspended solids, colloids, bacteria, viruses, etc. in the raw water during the sedimentation process, and then the precipitates are discharged through the sludge outlet to obtain the primary hardness-removed treated wastewater. At this time, the hardness of the wastewater ≤ 300 mg / L; after the pre-treatment is completed, advanced pre-treatment is carried out. The wastewater after the pre-treatment enters the concentrated brine tank for advanced pre-treatment, and then undergoes chemical precipitation again. Then, agents are added in the tubular membrane 4 (TMF) filtration to form precipitates of divalent cations such as calcium, magnesium, barium, strontium, etc. and silicon dioxide in the water. Then, using the good solid-liquid separation effect of the tubular microfiltration membrane under high-concentration suspended solids, these components that are likely to cause scaling in the subsequent reuse process are effectively removed. In most cases, the calcium ion concentration in the produced water is less than 20 mg / L, the magnesium ion concentration is less than 20 mg / L, and the silicon dioxide concentration is less than 10 mg / L; the filtered wastewater enters the resin unit, and the total hardness of the incoming water from the front end is removed through the resin softening system, adopting the weak acid cation resin type. The system mainly consists of a resin tank, an acid metering tank, an alkali metering tank (softening resin), a controller, etc. The raw water passes through the sodium-type cation exchange resin, so that the Ca 2+ and Mg 2+ in the water are exchanged with the Na + in the resin, thereby adsorbing the Ca 2+ and Mg 2+ in the water to soften the water, and finally the hardness of the produced water quality ≤ 10 mg / L.

[0038] The present invention has been described in detail above in combination with the embodiments in the accompanying drawings. Those of ordinary skill in the art can make various variations of the present invention according to the above description. Therefore, certain details in the embodiments should not constitute a limitation to the present invention, and the present invention will take the scope defined by the appended claims as the protection scope of the present invention.

Claims

1. A method for removing hardness from water by pretreatment plus deep pretreatment, characterized in that: The steps include: Providing a regulating tank, adding wastewater into the regulating tank, and pre-treating the wastewater in the regulating tank so that the liquid in the regulating tank reacts and precipitates; The wastewater in the regulating tank is subjected to solid-liquid separation to obtain a first reaction liquid, the first reaction liquid is added to a reaction tank, the pH of the first reaction liquid in the reaction tank is adjusted, and sodium carbonate is added to the reaction tank to make the first reaction liquid in the reaction tank react and precipitate; The first reaction liquid in the reaction tank is added to a tubular membrane for solid-liquid separation to obtain a second reaction liquid, and the precipitate after the chemical reaction of the second reaction liquid is intercepted by the tubular membrane, and the scaling substances are removed; The separated second reaction liquid is added to a resin unit to obtain a third reaction liquid, and the second reaction liquid is de-hardened by the resin unit.

2. The method for removing hardness from water by pretreatment plus deep pretreatment according to claim 1, characterized in that: When the wastewater is pretreated, soda ash solution is added into the regulating tank to generate precipitate, and the solution in the regulating tank is stirred until the precipitate is no longer generated.

3. The method for removing hardness from water by pretreatment plus deep pretreatment according to claim 2, characterized in that: After the stirring is completed, PFS coagulant is added to the regulating tank to coagulate the floating matter in the wastewater and generate flocs, and PAM flocculant is added to the adjusting tank to coagulate the flocs and form large flocs. After the large flocs are precipitated, they are discharged through a scraper.

4. The method for removing hardness from water by pretreatment plus deep pretreatment according to claim 1, characterized in that: When the pH of the first reaction liquid in the reaction tank is adjusted, the pH of the liquid in the reaction tank is monitored to provide a standard pH value range, soda ash is added to the reaction tank, and stirring is performed to control the pH value of the liquid in the reaction tank to be within the pH value range.

5. The method for removing hardness from water by pretreatment plus deep pretreatment according to claim 1, characterized in that: When sodium carbonate is added to the reaction tank, the pH value of the liquid in the reaction tank is monitored to provide a maintenance pH value range, and liquid alkali is added to the reaction tank and stirred so that the pH value of the liquid in the reaction tank is maintained within the maintenance pH value range.

6. The method for removing hardness from water by pretreatment plus deep pretreatment according to claim 1, characterized in that: After sodium carbonate is added to the reaction tank to generate precipitation, PFS coagulant is added to the reaction tank to coagulate the floating matter of the first reaction liquid to generate flocs, and PAM flocculant is added to the reaction tank to coagulate the flocs to form large flocs. After the large flocs are precipitated, they are discharged by a scraper.

7. The method for removing hardness from water by pretreatment plus deep pretreatment according to claim 1, characterized in that: When the resin unit is used to remove the hardness of the second reaction liquid, a macroporous weakly acidic acrylic cationic resin is used to remove the hardness of the second reaction liquid.

8. The method for removing hardness from water by pretreatment plus deep pretreatment according to claim 1, characterized in that: Before the resin unit is used to de-harden the second reaction liquid, the second reaction liquid is added to a pH adjustment tank, a standard pH value range is provided, and the pH of the liquid in the pH adjustment tank is adjusted and monitored so that the pH value of the second reaction liquid is within the standard pH value range.

9. The method for removing hardness from water by pretreatment plus deep pretreatment according to claim 1, characterized in that: When the resin unit is used to deharden the second reaction liquid, a standard water temperature range is provided, and the temperature of the second reaction liquid is controlled within the standard water temperature range.

10. The method for removing hardness from water by pretreatment plus deep pretreatment according to claim 1, characterized in that: After the wastewater is pretreated, a sedimentation tank is provided to separate the solid from the liquid in the wastewater.

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