Process method for simultaneously removing hardness and turbidity of sewage

Abstract

The invention relates to the technical field of sewage treatment, and discloses a process method for simultaneously removing hardness and turbidity of sewage, which comprises the following steps: S1, raw water pretreatment: raw water enters a pre-sedimentation regulating tank, and large-particle suspended matters are removed through sedimentation and regulation of water quality and water quantity; s2, adding chemicals for softening reaction: adding lime, sodium carbonate or caustic soda into the raw water to enable hardness ions to generate insoluble compounds, and settling the insoluble compounds; s3, filtering by a direct-filtration softening membrane: pressurizing the softened water into a direct-filtration softening membrane system, and filtering to remove residual suspended matters and precipitates; and S4, treating and recycling the effluent, namely directly discharging the effluent according to the purpose, and carrying out advanced treatment. According to the technical scheme of combining dosing softening with a direct filtration softening membrane, hard ions in water are removed by chemical reaction, and water is further purified by physical filtration, so that the purpose of simultaneously removing hardness and turbidity is achieved, the process flow is simplified, the occupied area is small, the installation and operation cost of equipment is reduced, and meanwhile, the treatment efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and specifically provides a process method for simultaneously removing hardness and turbidity from sewage. Background Art

[0002] In the field of sewage treatment, the treatment of high-hardness and high-turbidity wastewater is an important topic in industrial water use and urban water resource management. High-hardness wastewater usually contains a large amount of calcium and magnesium ions, which are prone to scale formation on the surfaces of pipelines and equipment, affecting industrial production and equipment operation efficiency. High-turbidity wastewater contains suspended particles, organic impurities, and colloidal substances, which are not easily settled and will increase the load on downstream treatment equipment. In the prior art, for the treatment of high-hardness and high-turbidity wastewater, processes such as chemical softening, coagulation sedimentation, filtration, or reverse osmosis are usually used for step-by-step treatment. For example, chemical softening can remove calcium and magnesium ions through chemical reactions to reduce hardness; coagulation sedimentation and filtration further remove suspended solids and particulate impurities to reduce turbidity. Reverse osmosis technology can achieve synergistic removal of hardness and turbidity in a single unit. These technologies have played an important role in practical applications and have good effects in meeting certain treatment objectives.

[0003] Although the prior art has made certain progress in the treatment of high-hardness and high-turbidity wastewater, there are still some problems that need to be optimized. The multi-stage treatment process usually has a relatively complex flow, occupies a large area, especially in scenarios with high treatment capacity requirements, its equipment investment and operation and maintenance costs are high. In addition, this type of process usually requires a large amount of flocculants (such as PAC, PAM) or acidic agents to achieve softening and precipitation, resulting in high consumption of chemical agents and being not conducive to reducing the treatment cost. At the same time, although some membrane separation technologies can achieve synergistic removal of hardness and turbidity, their operation has high requirements for the influent water quality, is prone to membrane fouling or scaling, affects the operation stability, increases the maintenance workload and energy consumption cost. In addition, due to the weak adaptability of the prior art to influent changes and insufficient automation level, the operation is complex in actual operation and has high technical requirements for personnel. Therefore, there is still a large room for optimization in the application scenarios and economy of the prior art in the treatment of high-hardness and high-turbidity wastewater. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a process method for simultaneously removing hardness and turbidity from sewage, which solves the problems of complex process flow, high operation cost, easy membrane fouling, and poor adaptability to water quality fluctuations in the prior art.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: A process method for simultaneously removing hardness and turbidity from sewage, comprising the following steps: S1. Raw water pretreatment: Introduce the raw water into the pre-sedimentation and regulation tank, remove large particulate suspended matters in the water by natural sedimentation and equalizing the water quality and quantity. S2. Chemical softening reaction: Add chemical agents such as lime, soda ash or caustic soda to the pretreated raw water, make the hardness ions in the water react with the agents to form insoluble compounds, and remove part of the hardness ions by sedimentation. S3. Direct filtration softening membrane filtration: Pressurize the softened water into the direct filtration softening membrane system, remove the residual suspended matters and the non-settled hardness precipitates in the water by filtration to obtain purified water. S4. Effluent treatment and reuse: According to the use of the effluent, directly discharge the purified water or send it to the advanced treatment process.

[0006] Preferably, in the step S2, the chemical agents added in the chemical softening reaction include one or more of the following: lime, soda ash, caustic soda.

[0007] Preferably, in the step S2, the chemical reaction process of the chemical softening reaction includes: (a) Calcium ions react with carbonate ions to form calcium carbonate precipitate; (b) Magnesium ions react with hydroxide ions to form magnesium hydroxide precipitate.

[0008] Preferably, in the step S3, the direct filtration softening membrane is made of polytetrafluoroethylene material, and the membrane pore size range is 0.01 μm to 1 μm.

[0009] Preferably, in the step S3, the operating pressure of the direct filtration softening membrane filtration is 0.2 MPa to 0.3 MPa, and the filtration flux is 30 LMH to 50 LMH.

[0010] Preferably, in the step S3, the material of the direct filtration softening membrane filaments used in the direct filtration softening membrane is mainly carbon and fluorine.

[0011] Preferably, in the step S4, the direct filtration softening membrane device adopts an external pressure filtration method, the influent is pressurized outside the membrane shell, and the purified water flows out from the inside of the membrane.

[0012] Preferably, in the step S4, the effluent treatment includes direct discharge or advanced treatment, and the advanced treatment adopts a reverse osmosis device.

[0013] Preferably, in the step S1, the volume of the pre-sedimentation and regulation tank is 1.5 times the daily maximum water treatment capacity, and the hydraulic retention time is 30 min to 60 min.

[0014] Preferably, in the step S2, the remaining precipitates after the softening reaction are regularly discharged through the sludge discharge pipe.

[0015] The present invention provides a process for simultaneously removing hardness and turbidity from sewage. It has the following beneficial effects: 1. The present invention adopts a technical solution combining chemical softening with direct filtration softening membrane. By means of chemical reactions, hardness ions in water are removed, and then physical filtration is used to further purify the water quality, achieving the purpose of simultaneously removing hardness and turbidity. Compared with the technical solutions in the prior art that require multiple complex treatment units connected in series, the present invention simplifies the process flow, occupies a small area, reduces the installation and operation costs of equipment, and improves the treatment efficiency at the same time.

[0016] 2. The direct filtration softening membrane of the present invention is made of polytetrafluoroethylene material, with the characteristics of high strength, chemical corrosion resistance and scale resistance. It can adapt to the influent conditions with suspended solids and high hardness, has a long operation life and stable performance. Compared with the membrane technologies in the prior art that are prone to scaling, require frequent cleaning and have a short replacement cycle, the present invention solves the problems of easy damage and high maintenance cost of traditional membrane systems, and significantly improves the stability and reliability of the system.

[0017] 3. By optimizing the chemical dosing method, the present invention only needs to add lime, soda ash or caustic soda to complete the softening reaction, avoiding the need for flocculants such as PAC and PAM widely used in the prior art. At the same time, the scale resistance of the direct filtration softening membrane reduces the frequency of acid cleaning. Compared with the methods of high chemical consumption and frequent chemical treatment in the prior art, the present invention greatly reduces the chemical dosage and system operation cost, achieving the effect of emphasizing both economy and environmental protection.

[0018] 4. The present invention adopts an external pressure filtration method, combined with modular design and PLC automatic control system, realizing the high efficiency of system operation and the convenience of operation. Different from the technical solutions in the prior art that rely on manual intervention and have high operation energy consumption, the present invention can adjust operation parameters in real time through automatic operation, solving the problems of complex control and high labor cost in the prior art, and ensuring the high treatment capacity and operation flexibility of the system while reducing energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the process step flow chart of the present invention; Figure 2 is the process operation flow chart of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0021] Please refer to the attachedFigure 1 - Attachment Figure 2 An embodiment of the present invention provides a process method for simultaneously removing hardness and turbidity from sewage, comprising the following steps: S1. Raw water pretreatment: Introduce the raw water into a pre-sedimentation and regulation tank, remove large particulate suspended matters in the water by natural sedimentation and balancing the water quality and quantity, S2. Chemical softening reaction: Add chemical agents such as lime, soda ash or caustic soda to the pretreated raw water, so that the hardness ions in the water react with the agents to form insoluble compounds, and remove part of the hardness ions by sedimentation; S3. Direct filtration softening membrane filtration: Pressurize the softened water into a direct filtration softening membrane system, and remove the remaining suspended matters and non-settled hardness precipitates in the water by filtration to obtain purified water; S4. Effluent treatment and reuse: According to the use of the effluent, directly discharge the purified water or send it to a advanced treatment process.

[0022] Specifically, the raw water is first preliminarily treated through a pre-sedimentation and regulation tank. In the regulation tank, the water flow velocity is reduced, and large particulate suspended matters naturally settle to the bottom of the tank due to gravity. At the same time, the regulation tank balances the water quality and quantity through a slow stirring device to reduce the impact of the influent load fluctuation on the subsequent treatment links; the settled water is transported to a chemical softening reaction tank. At this stage, agents such as lime, soda ash or caustic soda are accurately added to the water through a metering pump, so that calcium and magnesium ions react with the agents to form insoluble precipitates such as calcium carbonate and magnesium hydroxide, and these precipitates are removed by natural sedimentation. The softened water is discharged to the clear water area, and the bottom sediments of the tank are discharged through regular sludge discharge to ensure stable operation in the tank; the softened water is then pumped into a direct filtration softening membrane system through a pressure pump. In this process, a direct filtration softening membrane made of polytetrafluoroethylene is used to physically filter the water to further remove the remaining fine suspended matters and softening precipitates in the water. At the same time, the membrane surface has anti-scaling ability, which can avoid the accumulation of calcium and magnesium deposits on the membrane and ensure long-term stable operation. The filtered purified water then enters the effluent diversion system; finally, effluent treatment is carried out according to the water quality requirements. When the purified water meets the discharge standard, it can be directly discharged to natural water bodies through a drainage pipeline; if higher water quality is required, it is sent to an advanced treatment system such as a reverse osmosis device to further remove dissolved salts and trace pollutants. At the same time, part of the purified water is reused for backwashing the direct filtration softening membrane equipment to reduce the water consumption of the system. The flushing wastewater can be recycled back to the pre-sedimentation and regulation tank for recycling, reducing resource waste and improving the overall economy and environmental protection of the system. Through the close connection and coordinated operation of the above four steps, the present invention realizes the simultaneous removal of hardness and turbidity from sewage, and can flexibly adapt to different water quality requirements and treatment objectives, achieving efficient, stable and environmentally friendly treatment effects.

[0023] In the S1 step, the volume of the pre-sedimentation adjustment tank is 1.5 times the maximum daily water treatment capacity, and the hydraulic retention time is 30 min to 60 min.

[0024] Specifically, in the S1 step of this embodiment, the raw water is introduced from a water source or a sewage system into the pre-sedimentation adjustment tank. The main function of the pre-sedimentation adjustment tank is to balance the water quality and quantity of the raw water, and at the same time remove the large particle suspended solids therein, creating stable inlet conditions for the subsequent chemical softening reaction.

[0025] Generally, the volume of the pre-sedimentation adjustment tank is designed to be 1.5 times the maximum daily water treatment capacity to adapt to the working conditions with large water volume fluctuations. The hydraulic retention time is usually controlled within 30 min to 60 min. This retention time range can be adjusted according to the actual water quality conditions. For example, when the suspended particle concentration in the water is high, a longer retention time is selected, which helps for more thorough particle sedimentation.

[0026] In a possible implementation manner, a sludge discharge pipe is provided at the bottom of the adjustment tank for regularly discharging the deposited solid particles to avoid accumulation affecting the normal operation of the tank body. The discharge frequency of the sludge discharge pipe can be set according to the deposition rate of the solid particles, such as once a day or once every 8 h.

[0027] Specifically, the sedimentation of large particle suspended solids in the water depends on the gravity. Through the design of the pre-sedimentation adjustment tank, the water flow velocity is significantly reduced, and the suspended particles sink to the bottom of the tank during this process. The sedimentation rate of the suspended particles satisfies the following formula: where: is the acceleration due to gravity, with the unit of m / s 2 ; is the density of the particle, with the unit of kg / m 3 ; is the density of water, with the unit of kg / m 3 ; is the particle diameter, with the unit of m; is the dynamic viscosity of water, with the unit of Pa·ps.

[0028] Through the above formula, the sedimentation efficiency of the adjustment tank can be further optimized. For example, controlling the water flow velocity to enhance the sedimentation effect, or appropriately extending the retention time when the particle density is low.

[0029] As an option, in order to improve the particle sedimentation efficiency, in some embodiments, auxiliary devices such as inclined plate settlers or slow stirring devices can be added to the pre-sedimentation adjustment tank. The inclined plates can increase the sedimentation area, while the stirring device can evenly distribute the particles in the water, avoiding excessive local concentration that affects the sedimentation effect.

[0030] Specifically, the designed angle of the inclined plates is usually between 45° and 60°, and the length is determined according to the size of the tank body, generally 1.2 to 1.5 times the width of the tank. In the settler, large suspended particles slide along the plate surface to the bottom of the tank, further reducing the suspension time of the particles in the water.

[0031] In addition, in order to ensure the uniformity of water quality, a low-speed stirring device can be set in the adjustment tank. The stirring speed is controlled within the range of 10 RPM to 15 RPM, maintaining the uniformity of the water body while avoiding water flow disorder. For example, when the concentration of particulate matter in the raw water is high or the water volume fluctuates greatly, low-speed stirring can effectively avoid uneven particle distribution in the tank body.

[0032] In some embodiments, an anti-floating grid is set at the outlet of the adjustment tank to intercept larger suspended particles that have not been fully sedimented. The aperture of the grid is designed to be 0.5 mm to 2 mm, and is specifically selected according to the average particle size of the particles in the water. This measure further ensures the water quality entering the subsequent chemical softening tank.

[0033] In the step S2, the chemical agents added in the chemical softening reaction include one or more of the following: lime, soda ash, caustic soda; In the step S2, the chemical reaction process of the chemical softening reaction includes: (a) Calcium ions react with carbonate ions to form calcium carbonate precipitate; (b) Magnesium ions react with hydroxide ions to form magnesium hydroxide precipitate; In the step S2, the remaining precipitate after the softening reaction is regularly discharged through the sludge discharge pipe.

[0034] Specifically, in the step S2, the raw water flows from the pre-sedimentation adjustment tank into the chemical softening reaction tank. Appropriate chemical agents will be added to this reaction tank according to the water quality characteristics to remove the hardness ions in the water (mainly calcium ions Ca 2+ and magnesium ions Mg 2+ ). Generally, the selected agents include lime (CaO), soda ash or caustic soda (NaOH). The specific dosage of the agents can be adjusted according to the hardness of the water quality and the concentration of calcium and magnesium ions. The dosing amount of the metering pump is controlled in real time through an on-line monitoring system to ensure the efficient progress of the chemical reaction.

[0035] Specifically, the main principle of the softening reaction is to use the added chemicals to react with the hardness ions in the water to form insoluble precipitates, and the precipitates are separated from the water by natural sedimentation. The following is the specific content of the main chemical reactions: The calcium ions react with the carbonate ions to form insoluble calcium carbonate precipitate: Ca 2+ +CO3 2- →CaCO3↓ Among them, Ca 2 is the calcium ion in the water, with the unit of mg / L, and CO 2 3 is the carbonate ion, with the unit of mg / L.

[0036] The magnesium ions react with the hydroxide ions to form insoluble magnesium hydroxide precipitate: Mg 2+ +2OH − →Mg(OH)2↓ Among them, Mg 2+ is the magnesium ion in the water, with the unit of mg / L, and OH − is the hydroxide ion, with the unit of mg / L.

[0037] In a possible implementation, in order to improve the reaction efficiency between the chemical and the hardness ions, a stirring device is equipped in the reaction tank, and low-speed stirring is used to promote the full mixing of the chemical and the water body. The specific rotation speed of the stirring is usually controlled between 30 RPM and 60 RPM to avoid re-mixing the suspended precipitate into the water due to too fast stirring.

[0038] As an option, for the water quality with a relatively high concentration of hardness ions, the dosage of the chemical can be appropriately increased. For example, in the water containing more than 400 mg / L of calcium and magnesium ions, the dosage of lime and soda ash can be calculated according to the following formulas respectively: Among them: is the dosage of lime; is the dosage of soda ash; is the calcium ion concentration; is the magnesium ion concentration.

[0039] In some embodiments, in order to avoid excessive or insufficient chemicals, the calcium and magnesium ion concentrations in the water can be detected in real time by an online hardness monitor, and the dosing rate of the chemical can be adjusted. For example, when the calcium ion concentration drops below 50 mg / L, the dosing amount of lime or soda ash can be automatically reduced to prevent waste.

[0040] Generally, the softening reaction tank is designed as a continuous flow type, and the reaction time is controlled between 10 min and 20 min to ensure that the hardness ions and the reagent fully react to form precipitates. In a possible design, to improve the sedimentation separation efficiency, the softening reaction tank and the sedimentation tank are integrally designed so that the generated precipitates can quickly sink to the bottom of the tank. The precipitates are regularly discharged through the sludge discharge system, and the sludge discharge frequency can be once a day or once per shift, depending on the amount of sedimentation.

[0041] Specifically, to ensure that the precipitates do not interfere with the subsequent treatment, a sludge discharge cone can be installed at the bottom of the tank, and together with a timed sludge discharge pump, the precipitated calcium carbonate and magnesium hydroxide are discharged. The discharged precipitates can be centrally recovered and processed for other industrial uses, such as being used as fillers for building materials.

[0042] As a possible optimization method, the inlet and outlet of the softening reaction tank are designed in an upper and lower stratified inlet and outlet mode to reduce the disturbance of the water body. Specifically, the inlet is set at the bottom of the tank body and is equipped with a diffuser to evenly distribute the water flow; the outlet is located at the upper part of the tank body and is designed in an overflow form to ensure that the clear water flows into the subsequent filtration step.

[0043] Through the chemical softening reaction, the hardness ions in the raw water are effectively converted into precipitates and removed, significantly reducing the hardness of the water, providing good inlet conditions for the subsequent direct filtration softening membrane filtration, and at the same time reducing the risk of membrane fouling. The above technical solution combines chemical reactions and physical separation, can operate efficiently in industrial sewage treatment, and has wide applicability and flexibility.

[0044] In the S3 step, the direct filtration softening membrane is prepared from polytetrafluoroethylene material, and the membrane pore size range is 0.01 μm to 1 μm; In the S3 step, the operating pressure of the direct filtration softening membrane filtration is 0.2 MPa to 0.3 MPa, and the filtration flux is 30 LMH to 50 LMH; In the S3 step, the material of the direct filtration softening membrane filaments used in the direct filtration softening membrane is mainly carbon and fluorine.

[0045] Specifically, in the S3 step, the softened water flowing out of the chemical softening tank enters the direct filtration softening membrane equipment for filtration treatment. The direct filtration softening membrane equipment is driven by pressure to intercept the residual suspended solids and the non-settled hardness precipitates in the water outside the membrane, thereby further purifying the water quality.

[0046] Under normal circumstances, softened water is pressurized by a lift pump and enters the direct filtration softening membrane system. The operating pressure during the filtration process is controlled between 0.2 MPa and 0.3 MPa. The pressure value range can be adjusted according to the pore size of the membrane, the filtration flux, and the influent water quality conditions. Specifically, when the suspended solid concentration in the influent water is relatively high, the operating pressure can be appropriately increased to enhance the filtration capacity and maintain the stability of the membrane flux.

[0047] The direct filtration softening membrane is prepared from polytetrafluoroethylene (PTFE) material, which has high chemical stability and physical strength. The main components in the membrane filaments are carbon and fluorine. The chemical properties of these two elements enable the membrane surface not to react with calcium and magnesium ions or other common chemical substances in water under normal operating conditions, so it is not prone to fouling. In addition, the polytetrafluoroethylene material has an extremely low friction coefficient and high hydrophilicity, enabling water flow to pass through the membrane pores smoothly while solid particles are efficiently intercepted.

[0048] In a possible implementation, the pore size range of the direct filtration softening membrane is designed to be 0.01 μm to 1 μm. The pore size selection is set according to the particle size distribution of suspended solids and precipitates in the water. For example, when the unsettled precipitates in the water mainly exist in the form of larger particles, a membrane pore size close to 1 μm can be selected; while when further removal of tiny suspended solids is required, a smaller pore size is chosen.

[0049] As an option, to improve the filtration efficiency and equipment lifespan, the membrane device adopts an external pressure filtration mode. Specifically, softened water is pressurized from the outside of the membrane housing, water molecules enter the interior of the membrane through the membrane pores, while the unpassed suspended solids and precipitate particles remain on the outer surface of the membrane to form a filter cake layer. The presence of the filter cake layer can further enhance the interception ability for tiny particles, but its thickness needs to be controlled by backwashing.

[0050] In some embodiments, the filtration flux of the membrane is controlled between 30 LMH and 50 LMH. The flux range mainly depends on the membrane material and the operating pressure. For example, when the membrane operating pressure is close to 0.3 MPa, a relatively high flux value can be selected; while when operating at a lower pressure, a low flux value is adopted to extend the service life of the membrane.

[0051] Specifically, the concentrated water part that does not pass through the membrane during the filtration process (i.e., the water containing suspended solids and precipitates) can be periodically discharged to the sludge treatment system to avoid the accumulation of impurities in the concentrated water causing cumulative pollution to the filtration process. The frequency and discharge volume of the concentrated water discharge can be adjusted in real time according to the water quality monitoring data to ensure that the filtration performance of the membrane is maintained in the best state.

[0052] To avoid membrane pore blockage or excessive accumulation of particles on the outer surface of the membrane, the membrane device needs to be backwashed regularly. As a possible design, the backwash water comes from the purified water part of the direct filtration membrane, and the particles attached to the membrane surface are flushed away by reverse water flow. The backwash cycle is generally 8h to 24h, which is set according to the impurity concentration of the influent. When the suspended solid content in the water is high, the backwash interval can be shortened; while in the case of relatively stable water quality, the backwash cycle can be extended.

[0053] In some embodiments, to ensure the long-term stable operation of the membrane, chemical cleaning can also be carried out once every 3 months. The chemical cleaning solution can use a 1% citric acid solution or other weak acid solutions to dissolve the calcium and magnesium ion residues on the membrane surface. During the cleaning process, the concentration and flow rate of the solution need to be strictly controlled to avoid physical damage to the membrane material.

[0054] As an optimization measure, a primary filtration device is provided at the inlet of the direct filtration softening membrane device to intercept larger particles and avoid direct impact on the membrane. The pore size range of the primary filtration device is generally set to 100μm to 300μm, and its specific selection is related to the influent water quality. For example, when the average particle size of the particles in the water is 200μm, it is more appropriate to select a pore size close to 100μm.

[0055] Through the filtration treatment of the direct filtration softening membrane, the turbidity in the softened water can be effectively reduced to below 0.5 NTU. At the same time, the hardness precipitation and suspended solids are completely intercepted, providing high-quality purified water for subsequent effluent treatment. In addition, the concentrated water and filter cake generated during the filtration process can be recycled through the system and enter the sediment treatment link to achieve effective control of pollutants and resource recovery.

[0056] In the S4 step, the direct filtration softening membrane device adopts an external pressure filtration method, the influent is pressurized outside the membrane shell, and the purified water flows out from the inside of the membrane; In the S4 step, the effluent treatment includes direct discharge or advanced treatment, and the advanced treatment uses a reverse osmosis device.

[0057] Specifically, in the S4 step, the purified water filtered by the direct filtration softening membrane is diverted and treated according to specific uses. Generally, the effluent paths mainly include two methods: direct discharge and advanced treatment. The destination of the purified water is selectively designed according to water quality requirements, environmental protection discharge standards or reuse requirements.

[0058] As an option, if the hardness and turbidity of the purified water meet the environmental protection discharge standards or other water use requirements, it can be directly discharged into natural water bodies. Specifically, the water quality needs to meet the following parameters: Turbidity ≤ 0.5 NTU; Hardness ≤ 0.15 mmol / L; No obvious particles or other pollutants.

[0059] During the discharge process, the design of the drainage pipeline needs to consider hydraulic conditions and flow fluctuations. For example, when the daily treatment capacity of the system is large, the pipe diameter of the drainage pipeline can be selected in the range of 150 mm to 300 mm to avoid water flow blockage during the discharge process.

[0060] In a possible implementation, if the purified water needs to meet higher water quality standards (such as industrial ultrapure water or drinking water standards), it can enter the advanced treatment system. Advanced treatment generally uses a reverse osmosis device to further reduce the concentration of total dissolved solids (TDS) through membrane separation technology, while removing trace salts and other dissolved impurities in the water.

[0061] Specifically, the design parameters of the reverse osmosis device include: Membrane operating pressure: usually 2 MPa to 4 MPa; Water production rate: controlled at 50% to 75%; Membrane pore size: generally 0.0001 μm, which can intercept most dissolved salts and microorganisms.

[0062] The inlet conditions of the reverse osmosis device need to meet certain pretreatment requirements. For example, the SDI value (pollution index) of the inlet water is less than 3, and the turbidity is lower than 0.5 NTU. These conditions can be ensured by the aforementioned direct filtration and softening membrane filtration. The concentrated water part of the reverse osmosis device can be recycled or discharged after treatment according to the situation, depending on the nature and concentration of the pollutants.

[0063] Generally, in order to reduce the system operation cost, part of the purified water will be reused for backwashing the direct filtration and softening membrane equipment. The recycled water needs to be stored in the shunt regulation tank. The designed volume of the regulation tank is generally twice the daily backwashing water volume of the system to ensure a stable water supply during the backwashing process.

[0064] Specifically, the demand for backwashing water can be estimated by the following formula: Where: is the backwashing water volume, with the unit of m 3 ; is the filtration area of the direct filtration and softening membrane, with the unit of m 2 ; is the backwashing intensity, with the unit of m / h; is the backwashing time, with the unit of h As a possible optimization measure, the wastewater generated during the backwashing process can be refluxed to the pre-sedimentation regulation tank of the system to avoid environmental pollution caused by direct wastewater discharge. At the same time, this reflux design can reduce the overall waste of water resources.

[0065] In some embodiments, to ensure the stability of discharge or advanced treatment, the selection of the effluent path can be achieved through an automated control system. Specifically, parameters such as the hardness, turbidity, and flow rate of the purified water are monitored in real time by a PLC (Programmable Logic Controller), and the effluent path is automatically adjusted according to changes in water quality. For example, when the water quality monitoring system detects an increase in the turbidity value, the PLC will preferentially select the advanced treatment path to ensure that the final effluent quality meets the standards.

[0066] In addition, to cope with system fluctuations in special situations, such as water quality exceeding the standard or equipment failure within a short period of time, the system can be equipped with an emergency discharge device. The emergency discharge path should meet the following requirements: Be equipped with an automatic shut-off valve to prevent untreated water from entering natural water bodies; The drainage path should be connected to a wastewater storage tank to ensure that pollutants are discharged after subsequent treatment is completed.

[0067] Through the above effluent treatment design, this step can flexibly meet diverse water quality requirements, not only meeting the high-standard effluent requirements but also taking into account the economy and environmental protection of system operation. In addition, the reuse design of this step effectively reduces the overall water consumption of the system and enhances the sustainability of system operation.

[0068] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for simultaneously removing hardness and turbidity from sewage, characterized in that, It includes the following steps: S1. Raw water pretreatment: Introduce the raw water into the pre-sedimentation and regulation tank, remove large particulate suspended matters in the water by natural sedimentation and balancing the water quality and quantity; S2. Chemical softening reaction: Add chemical agents such as lime, soda ash or caustic soda to the pretreated raw water, make the hardness ions in the water react with the agents to form insoluble compounds, and remove part of the hardness ions by sedimentation; S3. Direct filtration softening membrane filtration: Pressurize the softened water into the direct filtration softening membrane system, remove the residual suspended matters and non-settled hardness precipitates in the water by filtration to obtain purified water; S4. Effluent treatment and reuse: According to the use of the effluent, directly discharge the purified water or send it to the advanced treatment process.

2. A process method for simultaneously removing hardness and turbidity from sewage according to claim 1, characterized in that, In the step S2, the chemical agents added in the chemical softening reaction include one or more of the following: lime, soda ash, caustic soda.

3. A process for simultaneously removing hardness and turbidity from sewage according to claim 1, characterized in that, In the step S2, the chemical reaction process of the chemical softening reaction includes: (a) Calcium ions react with carbonate ions to form calcium carbonate precipitate; (b) Magnesium ions react with hydroxide ions to form magnesium hydroxide precipitate.

4. A process method for simultaneously removing hardness and turbidity from sewage according to claim 1, characterized in that, In the step S3, the direct filtration softening membrane is prepared from polytetrafluoroethylene material, and the membrane pore size range is 0.01μm - 1μm.

5. A process for simultaneously removing hardness and turbidity from sewage according to claim 1, characterized in that, In the step S3, the operating pressure of the direct filtration softening membrane filtration is 0.2MPa - 0.3MPa, and the filtration flux is 30LMH - 50LMH.

6. A process method for simultaneously removing hardness and turbidity from sewage according to claim 1, characterized in that, In the step S3, the material of the direct filtration softening membrane filaments used in the direct filtration softening membrane is mainly carbon and fluorine.

7. A process for simultaneously removing hardness and turbidity from sewage according to claim 1, characterized in that, In the step S4, the direct filtration softening membrane device adopts the external pressure filtration method, the inlet water is pressurized outside the membrane shell, and the purified water flows out from the inside of the membrane.

8. A process for simultaneously removing hardness and turbidity from sewage according to claim 7, characterized in that, In the step S4, the effluent treatment includes direct discharge or advanced treatment, and the advanced treatment adopts a reverse osmosis device.

9. A process for simultaneously removing hardness and turbidity from sewage according to claim 1, characterized in that, In the step S1, the volume of the pre-sedimentation and regulation tank is 1.5 times the maximum daily water treatment volume, and the hydraulic retention time is 30min - 60min.

10. A process for simultaneously removing hardness and turbidity from sewage according to claim 1, characterized in that, In the step S2, the remaining precipitates after the softening reaction are regularly discharged through the sludge discharge pipe.

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