Method and system for filter-pressing treatment of production wastewater in construction period of railway tunnel engineering

Abstract

The invention discloses a railway tunnel engineering construction period production wastewater filter pressing treatment method and system, and relates to the technical field of environmental engineering and water treatment.The railway tunnel engineering construction period production wastewater filter pressing treatment method comprises the following steps that S1, quality-divided collection and hardening and tempering are conducted; the method comprises the following steps: respectively collecting high-specific-gravity rock powder-containing wastewater generated in tunneling and organic colloid-containing wastewater generated in a tunnel field area; s2, performing multi-stage coagulation and reinforced solid-liquid separation; feeding the conditioned wastewater into an efficient vortex coagulation device, and instantaneously adding an inorganic coagulant under the condition of violent turbulence so as to destabilize fine particles; s3, carrying out chemical conditioning and mechanical filter pressing on the sludge; s4, synergistically purifying and recycling the filtrate; by adopting the filter pressing treatment method and the filter pressing treatment system for the production wastewater in the construction period of the railway tunnel engineering, reduction and recycling are realized; and meanwhile, through ultrafiltration deep purification, the wastewater is reused for a high-standard construction process, near-zero emission of the production wastewater and resource utilization of solid wastes are finally achieved, and remarkable environmental protection and economic benefits are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of environmental engineering and water treatment technology, and particularly relates to a railway tunnel engineering construction period production wastewater pressure filtration treatment method and system. BACKGROUND

[0002] The most common method currently used in construction sites is to add PAC, PAM and other reagents for flocculation and sedimentation, and then use ordinary compartment filter presses or belt filter presses for dewatering. The water content of the treated sludge is usually higher than 60%, and even up to 80%. The mud cake is viscous and bulky, and the subsequent disposal is difficult. For complex tunnel wastewater (especially containing stable colloids such as shield lubricant), the traditional flocculation process cannot completely destroy the stability of the colloids, resulting in poor solid-liquid separation effect and large fluctuations in effluent quality. The produced water usually contains residual colloids and trace pollutants, and the water quality cannot meet the high-standard reuse requirements, so it is mostly used for simple purposes such as dust reduction, and the water resource utilization rate is low. High-moisture sludge is defined as hazardous waste, which needs to be outsourced for disposal, resulting in high cost and environmental risk.

[0003] The existing technology integrates wastewater pretreatment, sludge dewatering, and clean water reuse as independent unit operations, lacks systematic integration and linkage design, and each unit operates independently, requiring a large amount of manual intervention and monitoring, and having low automation degree. There is a lack of connection between the treatment units, especially the filtrate and backwash water cannot be effectively recovered and treated, making it difficult to achieve the true "zero discharge" goal. The dispersed layout is not suitable for efficient deployment in the tunnel construction temporary site area where land is scarce. Traditional dewatering usually only adds PAM or single lime for conditioning. For tunnel sludge rich in organic matter, a single reagent cannot change the cell structure and water occurrence form of the sludge, and the dewatering performance is limited, making it difficult to achieve deep dewatering. SUMMARY

[0004] The present application aims to provide a railway tunnel engineering construction period production wastewater pressure filtration treatment method and system, which realizes reduction and resource utilization. At the same time, through ultrafiltration deep purification, the wastewater is reused in high-standard construction processes, ultimately achieving near-zero discharge of production wastewater and resource utilization of solid waste, and having significant environmental and economic benefits.

[0005] The present application provides a railway tunnel engineering construction period production wastewater pressure filtration treatment method and system, which comprises the following steps:

[0006] Step S1, collecting and conditioning according to quality;

[0007] High-specific-gravity rock powder wastewater generated by tunneling and organic colloid wastewater generated in the tunnel site are collected separately and pumped into a grid conditioning tank for mixing and water quality balancing to form homogeneous wastewater. A gel breaker is added to the homogeneous wastewater to destroy the stable colloid system formed by the tunnel shield lubricant.

[0008] Step S2, multi-stage coagulation and enhanced solid-liquid separation;

[0009] The conditioned wastewater is fed into a high-efficiency vortex coagulator, in which inorganic coagulant is instantaneously added under intense turbulent flow conditions to destabilize the fine particles; then the wastewater enters a flocculation tank, in which special flocculant is slowly added under laminar flow conditions to form high-density and easily-settled flocs; the coagulated wastewater enters a slant-tube sedimentation tank with a slant-tube module for enhanced sedimentation to obtain supernatant and concentrated sludge;

[0010] Step S3, chemical conditioning and mechanical pressure filtration of sludge;

[0011] The concentrated sludge discharged from the slant-tube sedimentation tank is transported to a sludge conditioning tank, in which CaO and FeCl3 are sequentially added for chemical conditioning to change the cell structure and water existing form of the sludge; the conditioned sludge is pumped into a diaphragm-type plate-and-frame filter press by a high-pressure pump, and sequentially subjected to low-pressure filling, high-pressure squeezing and compressed air stripping to produce dried sludge cake with a water content of less than 50%;

[0012] Step S4, synergistic purification and reuse of filtrate;

[0013] The supernatant produced by the slant-tube sedimentation tank and the pressure filtrate produced by the filter press are collected into an intermediate tank, and then pumped into an immersed ultrafiltration membrane system for deep purification, and the produced clear water is stored in a reuse water tank; the clear water is reused for concrete mixing, grouting operation or equipment cleaning in tunnel construction.

[0014] Preferably, in step S1, the gel breaker is sodium hypochlorite or persulfate.

[0015] Preferably, in step S2, the special flocculant is cationic polyacrylamide with a network structure.

[0016] Preferably, in step S3, the specific process of chemical conditioning is to first add CaO at 10%-20% of the weight of dry sludge to the sludge, and react for 20-30 minutes; then add FeCl3 at 3%-8% of the weight of dry sludge, and react for 10-15 minutes; the high-pressure squeezing pressure of the diaphragm-type plate-and-frame filter press is 1.5-2.0 MPa, and the squeezing time is 15-30 minutes.

[0017] Preferably, in step S4, the immersed ultrafiltration membrane system adopts a membrane pore size of 0.01-0.1 μm, and the operation mode is constant-flow filtration alternated with air-water backwashing, the cycle of air-water backwashing is 40-60 minutes, and during backwashing, the clear water in the reuse water tank is used and supplemented with compressed air scrubbing.

[0018] Preferably, in step S3, the dried sludge cake is used as roadbed filling material together with tunnel spoil for resource utilization.

[0019] Preferably, a railway tunnel engineering construction period production wastewater pressure filtration treatment system, including grid regulation pool, high-efficiency vortex coagulator, flocculation tank, inclined tube sedimentation tank, sludge conditioning tank, diaphragm type plate and frame filter press, high-pressure pump, intermediate water pool, submerged ultrafiltration membrane system and reuse water pool, the grid regulation pool is connected with high-efficiency vortex coagulator, high-efficiency vortex coagulator is connected with flocculation tank, flocculation tank is connected with inclined tube sedimentation tank, one side of flocculation tank is connected with sludge conditioning tank, sludge conditioning tank is connected with diaphragm type plate and frame filter press, diaphragm type plate and frame filter press is connected with intermediate water pool, the other side of inclined tube sedimentation tank is connected with intermediate water pool, intermediate water pool is connected with submerged ultrafiltration membrane system and reuse water pool, submerged ultrafiltration membrane system and reuse water pool are connected with reuse water pool.

[0020] Therefore, the railway tunnel engineering construction period production wastewater pressure filtration treatment method and system are used to realize reduction and resource utilization, and through deep purification of ultrafiltration, the wastewater is reused in high-standard construction procedures, so that near-zero discharge of production wastewater and resource utilization of solid waste are achieved, and remarkable environmental protection and economic benefits are obtained.

[0021] The technical scheme of the present application is further described below with reference to the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0022] Fig. 1 It is a flowchart of the railway tunnel engineering construction period production wastewater pressure filtration treatment method of the present application.

[0023] Fig. 2 It is a system block diagram of the system of the railway tunnel engineering construction period production wastewater pressure filtration treatment method of the present application. DETAILED DESCRIPTION

[0024] The technical scheme of the present application is further described below with reference to the drawings and examples.

[0025] Unless otherwise defined, technical terms or scientific terms used in the present application shall have the usual meaning understood by a person with ordinary skill in the art to which the present application belongs.

[0026] The terms "first", "second", and similar terms used in the present application do not indicate any order, number, or importance, but are only used to distinguish different components. The terms "include" or "contain" and similar terms mean that the elements or objects before the terms cover the elements or objects listed after the terms and their equivalents, and do not exclude other elements or objects. The terms "connect" or "connected" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms "up", "down", "left", "right", and the like are only used to indicate relative positional relationships, and when the absolute positions of the described objects change, the relative positional relationships may also change accordingly.

[0027] Embodiment one

[0028] As Figs. 1-2 shown, the railway tunnel engineering construction period production wastewater pressure filtration treatment method and system, comprising the following steps:

[0029] Step S1, quality collection and conditioning;

[0030] The tunneling generated with high specific gravity rock dust wastewater and tunnel site generated with organic colloid wastewater are collected respectively, and pumped into the grid conditioning pool for mixing and water quality balance, forming homogeneous wastewater. Add breaker to the homogeneous wastewater to destroy the stable colloid system formed by the tunnel shield lubricant, and the breaker is sodium hypochlorite or persulfate.

[0031] Source branch collection: tunneling generated with high specific gravity rock dust wastewater, high specific gravity rock dust wastewater is characterized by high suspended solids concentration (up to 5000-10000 mg / L), wide particle size distribution, but relatively low organic colloid content.

[0032] Special for collecting tunnel portal site generated with organic colloid wastewater, the characteristics of organic colloid wastewater is containing a large amount of emulsified oil and colloid formed by shield lubricant (such as saponified oil, polymer, etc.), and the organic matter concentration is relatively high, and the suspended solids concentration may be lower than that of rock dust wastewater but more stable. Mixing of the two types of wastewater at the source is strictly prohibited to avoid interference of different pollutants with each other and increase the difficulty of subsequent treatment.

[0033] Grid interception and conditioning: the wastewater of the two collection channels is intercepted by the coarse grid well after intercepting larger floating and particulate matters, and then flows into the same grid conditioning pool.

[0034] The effective volume of the grid conditioning pool should be able to accommodate at least 8-12 hours of wastewater production to ensure sufficient water quality and quantity balancing effect. Submersible mixer or multi-hole aeration pipe (blowing agitation) needs to be installed in the pool for continuous operation to prevent suspended solids from depositing and make the water quality uniform. The role of the grid is to regularly clean the debris intercepted by the grid to prevent the water pump and pipeline from being blocked. According to the signal of the liquid level meter in the pool, the booster pump is automatically started and stopped to deliver the wastewater to the subsequent treatment unit.

[0035] Breaker addition and reaction: add breaker to the conditioning pool through the breaker addition system (including metering pump, medicine tank and stirrer).

[0036] Medicine selection: first choose sodium hypochlorite (NaClO) solution (effective chlorine content 10%) or persulfate (such as ammonium persulfate). Sodium hypochlorite destroys the molecular structure of organic colloid and emulsified oil through strong oxidation; persulfate realizes high-efficiency oxidation by generating sulfate free radicals.

[0037] Dosing control: The optimum dosage is determined by small-scale test according to wastewater quality, which is generally controlled in the range of 50-200 mg / L. The dosing should be automatic through flow meter linkage or manual at the determined frequency.

[0038] Reaction requirement: Ensure the continuous operation of the stirring in conditioning tank, so that the breaker can be fully mixed with wastewater, and the reaction time should not be less than 15 minutes to completely destroy the stable colloidal system formed by lubricants.

[0039] Step S2, multi-stage coagulation and enhanced solid-liquid separation

[0040] The conditioned wastewater is sent to a high-efficiency vortex coagulator, where inorganic coagulant is instantaneously added under intense turbulent flow conditions to destabilize the fine particles; then the wastewater enters a flocculation tank, where special flocculant is slowly added under laminar flow conditions to form high-density and easily-settleable floc; the coagulated wastewater enters a inclined-tube sedimentation tank with inclined-tube module for enhanced sedimentation to obtain supernatant and concentrated sludge. In step S2, the special flocculant is cationic polyacrylamide with network structure.

[0041] Vortex mixing and coagulant addition: The conditioned wastewater is sent to a high-efficiency vortex coagulator by a booster pump. The device produces intense turbulent flow through its special internal structure or tubular static mixer. At the inlet of the coagulator, inorganic coagulant is instantaneously and continuously added by a coagulant addition system. The commonly used agent is polyaluminum chloride, which can effectively compress the colloidal double layer through the hydrolysis of multiple high-valent cations to quickly destabilize fine particles. The PAC dosage is usually 200-400 mg / L. The addition point must be selected at the most intense turbulent flow to ensure that the agent can be uniformly mixed with the wastewater in an instant.

[0042] Flocculation reaction and flocculant addition: After instantaneous mixing, the wastewater immediately enters a flocculation tank.

[0043] Flow state control: The flocculation tank is usually designed with folded plate or mesh to make the water flow in a suitable laminar state, creating good conditions for floc growth.

[0044] Agent addition: In the first section of the flocculation tank, special flocculant, i.e., cationic polyacrylamide with network structure, is slowly added by a flocculant addition system. The molecular weight is recommended to be 8-12 million Daltons. The cationic groups can neutralize the negative charge on the particle surface, and the long molecular chains can connect the destabilized fine particles into large, dense, and easily-settleable alum flower flocs through "adsorption bridging" and "net trapping and sweeping" actions.

[0045] Control parameters: CPAM dosage is generally 2-5 mg / L. It needs to be prepared into a dilute solution of 0.1%-0.2% first, and attention should be paid to observe the formation of alum flowers when dosing. The alum flowers are large, clear and sink quickly, which is the best. The total flocculation reaction time should be controlled within 15-20 minutes.

[0046] Sedimentation separation by inclined tube: the flocculated wastewater flows into the inclined tube sedimentation tank by itself; a dense inclined tube assembly is installed in the tank, which greatly increases the sedimentation area and improves the sedimentation efficiency according to the "shallow pool theory". The water flows upward along the inclined tube, and the flocs settle on the wall of the inclined tube under the action of gravity and slide to the bottom sludge hopper. The supernatant is collected through the top water collecting tank; the surface load of the inclined tube sedimentation tank should be designed between 5-10 m3 / (m2·h). The clarity of the effluent should be observed regularly, and the concentrated sludge should be discharged from the bottom sludge hopper at regular intervals (such as every 4-8 hours). The moisture content of the discharged sludge is about 97%-98%.

[0047] Step S3, sludge chemical conditioning and mechanical pressure filtration; the concentrated sludge discharged from the inclined tube sedimentation tank is transported to the sludge conditioning tank, and CaO and FeCl3 are added in turn for chemical conditioning to change the cell structure and water existing form of the sludge. The conditioned sludge is pumped into the diaphragm plate and frame filter press by high pressure, and is sequentially subjected to low pressure filling, high pressure squeezing and compressed air stripping to produce dry cake with water content less than 50%.

[0048] In step S3, the specific process of chemical conditioning is to first add CaO with a weight of 10%-20% of the dry sludge to the sludge, and react for 20-30 minutes. Then add FeCl3 with a weight of 3%-8% of the dry sludge, and react for 10-15 minutes; the high pressure squeezing pressure of the diaphragm plate and frame filter press is 1.5-2.0 MPa, and the squeezing time is 15-30 minutes.

[0049] In step S3, the dry cake is used as roadbed filling material together with the tunnel hole slag for resource utilization.

[0050] Sludge concentration: the sludge discharged from the inclined tube sedimentation tank first enters the sludge concentration tank; through natural gravity sedimentation, the moisture content and volume of the sludge are further reduced, and the chemical consumption of subsequent chemical conditioning and the treatment load of the filter press are reduced. The sludge is left to concentrate in the concentration tank for 6-12 hours, the supernatant overflows back to the conditioning tank, and the concentrated sludge (moisture content reduced to about 95%) at the bottom is pumped to the conditioning tank by a sludge pump.

[0051] Stepwise chemical conditioning: the core prerequisite for achieving deep dewatering. The concentrated sludge is transported to the sludge conditioning tank with a stirrer; add lime (CaO): add lime powder with a weight of 10%-20% of the dry sludge. Its main functions include: providing Ca2 +, promote flocculation; strong exothermic reaction, change the sludge colloidal structure, kill microorganisms, release internal bound water; improve the pH value of sludge, destroy the cell wall, release intracellular water; improve the pore structure of sludge, make it more easily dewatered.

[0052] Through the dry powder dosing machine or manual control dosing amount. After dosing, start the stirrer, stir at medium speed for 20-30 minutes to ensure that lime and sludge are fully mixed and reacted. Add ferric chloride (FeCl3): add 3%-8% of ferric chloride solution based on the weight of dry sludge. As a high-efficiency coagulant, FeCl3 hydrolysis produces Fe(OH)3 flocs that can further capture fine sludge particles, building a more robust skeletal structure that makes the sludge less likely to be compressed and deformed under high pressure, keeping the water outflow channel unobstructed. After the lime dosing reaction is complete, add FeCl3 solution and continue stirring for 10-15 minutes. It must be noted that the order of addition is lime first and then iron salt to achieve the best conditioning effect. The conditioned sludge should present a loose, granular, and non-viscous physical form.

[0053] Diaphragm press dewatering: The conditioned sludge is pumped into a diaphragm plate and frame filter press by a high-pressure plunger pump at high pressure. Filter press preparation: Check if the filter cloth is intact, and if the hydraulic system and electrical control system are normal. Close the filter plate to ensure good sealing.

[0054] Low-pressure filling period (feeding period): Start the feeding pump to fill all filter chambers with sludge at a relatively low pressure (usually 0.6-0.8 MPa). This stage mainly relies on the pressure of the pump for filtration and dewatering.

[0055] High-pressure pressing period: When the feeding pressure rises to the set value and the liquid output is very small, automatically switch to the high-pressure pressing stage. Start the hydraulic system to fill the elastic diaphragm with high-pressure water or compressed air, and the diaphragm expands to perform secondary extrusion on the sludge in the filter chamber. The pressing pressure in this stage should be maintained at 1.5-2.0 MPa, and the pressing time should last for 15-30 minutes. This is the key to further reducing the moisture content.

[0056] Compressed air stripping period: After pressing is completed, release the diaphragm pressure, then introduce 0.6-0.8 MPa of compressed air to penetrate from the inside of the sludge cake and blow away the residual interstitial water. The stripping time is about 10-15 minutes.

[0057] Unloading and cleaning: After stripping is completed, pull open the filter plate, and the mud cake is automatically detached. Check the filter cloth and clean it if it is clogged. Record the thickness and shape of the mud cake. Produce a hard, blocky, and low-moisture (less than 50%) dried mud cake.

[0058] Resource disposal of mud cake: The mud cake produced by pressure filtration is temporarily stacked in an impermeable yard. The heavy metal content and toxicity of the mud cake are detected. After confirming that the mud cake is non-toxic and harmless, the mud cake is mixed with the tunnel excavation waste at a certain ratio to serve as roadbed filling material for comprehensive utilization, thereby completing the resource closed loop.

[0059] Step S4, synergistic purification and reuse of filtrate;

[0060] The supernatant produced by the inclined tube sedimentation tank and the pressure filtrate produced by the filter press are collected in an intermediate pool, and then pumped into an immersed ultrafiltration membrane system for deep purification. The clean water produced is stored in a reuse pool. The clean water is reused for concrete mixing, grouting operation or equipment cleaning in tunnel construction.

[0061] In step S4, the membrane pore size of the immersed ultrafiltration membrane system is 0.01-0.1 μm, and the operation mode is constant flow filtration and air-water backwashing alternately. The cycle of air-water backwashing is 40-60 minutes. During backwashing, the clean water in the reuse pool is used and supplemented with compressed air scrubbing.

[0062] Filtrate collection: The supernatant produced by the inclined tube sedimentation tank and the pressure filtrate produced by the filter press are collected in an intermediate pool by pipeline flow or pumping. The pool serves to collect, buffer and adjust the water volume.

[0063] Ultrafiltration membrane deep purification: the wastewater in the intermediate pool is lifted to the immersed ultrafiltration membrane system by a water pump.

[0064] The ultrafiltration membrane pore size is 0.01-0.1 μm, which can effectively intercept colloids, bacteria, microorganisms and macromolecular organic matter in water, and remove suspended solids. The system adopts constant flow filtration mode, and the clean water produced is pumped out by a suction pump. With operation, the membrane surface will be contaminated and the water permeability will decrease. Every 40-60 minutes of operation, the system automatically performs air-water backwashing. First, the membrane assembly is backwashed with clean water from the reuse pool, and at the same time, air is blown from the bottom of the membrane assembly. The strong agitation and scrubbing effect generated by compressed air can remove the dirt on the membrane surface. The backwashing wastewater is discharged back to the regulation pool for reprocessing. Chemical cleaning: according to the change of transmembrane pressure difference, chemical enhanced backwashing (CEB) or offline cleaning (CIP) is performed regularly (such as every month) to restore the membrane performance.

[0065] Clean water reuse and closed loop management: the clean water produced by the ultrafiltration membrane is stored in a reuse pool. The water quality in the reuse pool is detected regularly, with a focus on turbidity, pH value and other indicators. The clean water is 100% delivered to various water points through a reuse pump and pipe network, including a concrete mixing station in the tunnel, simultaneous grout preparation, shield machine and equipment cleaning, and site dust and landscaping flushing.

[0066] The application discloses a railway tunnel engineering construction period production wastewater pressure filtration treatment system, which comprises a grid adjusting pool, an efficient vortex coagulator, a flocculation pool, an inclined pipe sedimentation pool, a sludge conditioning tank, a diaphragm type plate and frame filter press, a high-pressure pump, an intermediate water pool, an immersed ultrafiltration membrane system and a reuse water pool, the grid adjusting pool is connected with the efficient vortex coagulator, the efficient vortex coagulator is connected with the flocculation pool, the flocculation pool is connected with the inclined pipe sedimentation pool, one side of the flocculation pool is connected with the sludge conditioning tank, the sludge conditioning tank is connected with the diaphragm type plate and frame filter press, the diaphragm type plate and frame filter press is connected with the intermediate water pool, the other side of the inclined pipe sedimentation pool is connected with the intermediate water pool, the intermediate water pool is connected with the immersed ultrafiltration membrane system and the reuse water pool, and the immersed ultrafiltration membrane system and the reuse water pool are connected with the reuse water pool.

[0067] The wastewater treatment main line is as follows: wastewater firstly enters the grid adjusting pool, water quality and quantity are homogenized and preliminary interception is carried out, then the wastewater sequentially flows through the efficient vortex coagulator, the flocculation pool and the inclined pipe sedimentation pool, and the core purification process of coagulation, flocculation and solid-liquid separation is completed.

[0068] The sludge treatment auxiliary line is as follows: concentrated sludge generated by the inclined pipe sedimentation pool is transported to the sludge conditioning tank for chemical conditioning, the conditioned sludge is driven by the high-pressure pump and enters the diaphragm type plate and frame filter press for deep dewatering, and finally dry mud cake is formed.

[0069] The deep treatment and reuse are as follows: supernatant generated by the inclined pipe sedimentation pool and filter press liquid are collected into the intermediate water pool, the mixed liquid is pumped into the immersed ultrafiltration membrane system for deep purification, and the produced clean water is finally stored in the reuse water pool for reuse.

[0070] After being pretreated, the wastewater in the grid adjusting pool is quantitatively pumped into the inlet pipeline of the efficient vortex coagulator by a corrosion-resistant lifting pump (usually a submersible pump or a centrifugal pump), and the wastewater mixed by the vortex is directly self-flowed into the inlet of the flocculation pool by relying on the difference in height or the pipeline flow rate. The connection needs to ensure that the water flow is smooth and transition, so that the flocculation is not broken before entering the flocculation pool. The wastewater after flocculation is evenly and smoothly distributed to the water inlet area of the entire inclined pipe sedimentation pool through the water distribution device at the end of the flocculation pool, so that the water flow is uniformly raised and the sedimentation efficiency is improved. The water collecting tank at the upper part of the inclined pipe sedimentation pool is connected with the intermediate water pool through a channel or a pipeline, the supernatant after sedimentation is collected through the water collecting tank and is self-flowed into the intermediate water pool by relying on gravity, the sludge hopper at the bottom of the inclined pipe sedimentation pool is connected with the sludge conditioning tank through a sludge pump (such as a screw pump) and a pipeline, and the concentrated sludge deposited at the bottom of the pool is regularly pumped and transported to the sludge conditioning tank by the sludge pump for chemical conditioning.

[0071] The sludge conditioning tank is connected with a high-pressure pump (usually a high-pressure plunger pump) and a high-pressure pipeline, and the chemically conditioned sludge is pumped into each filter chamber of the diaphragm plate and frame filter press by the high-pressure plunger pump at high pressure. The diaphragm plate and frame filter press is connected with an intermediate water pool through a pipeline, and the filter press liquor generated in the filter pressing process is collected in a collecting tank below the filter press, and then is pumped or flows by itself to the intermediate water pool through the pipeline, and is mixed with the supernatant of the inclined tube sedimentation tank for subsequent deep treatment. The mixed filtrate in the intermediate water pool is delivered to the membrane pool of the immersed ultrafiltration membrane system by a feed water pump at a constant flow rate, the water produced by the ultrafiltration membrane (clean water) is pumped out from the inside of the membrane wire by a vacuum suction pump, and is delivered to a clean reuse water pool for storage through a pipeline; the clean water in the reuse water pool is used for construction production on one hand, and on the other hand, when the ultrafiltration membrane needs air-water backwashing, is pumped out by a backwashing water pump, and is used for backwashing the membrane assembly to ensure the membrane flux; the backwashing wastewater generated by the ultrafiltration system is rich in pollutants, and is returned to the grid regulation pool at the front end through a pipeline, and is treated again to realize zero discharge of wastewater.

[0072] Therefore, the railway tunnel engineering construction period production wastewater pressure filtration treatment method and system are adopted, so that the reduction and resource utilization are realized; meanwhile, the wastewater is reused for high-standard construction procedures through ultrafiltration deep purification, so that the production wastewater near-zero discharge and the resource utilization of solid waste are finally achieved, and remarkable environmental protection and economic benefits are achieved.

[0073] The above embodiments are only used to illustrate the technical solutions of the present application but not to limit them, and although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for pressure filtration treatment of production wastewater during railway tunnel engineering construction period, characterized in that, The method comprises the following steps: Step S1, collecting and conditioning according to quality; The tunneling generated high specific gravity rock powder wastewater and the tunnel site generated organic colloid wastewater are collected respectively and pumped into a grid conditioning pool for mixing and water quality balancing to form homogeneous wastewater; a gel breaker is added to the homogeneous wastewater to destroy the stable colloid system formed by the tunnel shield lubricant; Step S2, multi-stage coagulation and enhanced solid-liquid separation; The conditioned wastewater is sent into a high-efficiency vortex coagulator, in which an inorganic coagulant is instantaneously added under intense turbulent flow conditions to make the fine particles unstable; Subsequently, the wastewater enters a flocculation tank, in which a special flocculant is slowly added under laminar flow conditions to form high-density and easily-settled flocs; the coagulated wastewater enters an inclined-tube sedimentation tank with a slanted tube module for enhanced sedimentation to obtain supernatant and concentrated sludge; Step S3, sludge chemical conditioning and mechanical pressure filtration; The concentrated sludge discharged from the inclined-tube sedimentation tank is transported to a sludge conditioning tank, in which CaO and FeCl3 are sequentially added for chemical conditioning to change the cell structure and water existing form of the sludge; the conditioned sludge is sent into a diaphragm plate-and-frame filter press by a high-pressure pump to sequentially undergo low-pressure filling, high-pressure squeezing and compressed air stripping to produce dry sludge cake with a water content of less than 50%; Step S4, filtrate cooperative purification and reuse; The supernatant generated by the inclined-tube sedimentation tank and the pressure filtrate generated by the filter press are collected into an intermediate pool, and then pumped into an immersed ultrafiltration membrane system for deep purification, and the produced clean water is stored in a reuse water pool; the clean water is reused for tunnel construction concrete mixing, grouting operation or equipment cleaning.

2. The method according to claim 1, wherein the method is characterized by, In step S1, the gel breaker is sodium hypochlorite or persulfate.

3. The method according to claim 1, wherein the method is characterized by, In step S2, the special flocculant is a cationic polyacrylamide with a network structure.

4. The method according to claim 1, wherein the method is characterized by, In step S3, the specific process of chemical conditioning is as follows: first, CaO accounting for 10%-20% of the dry sludge weight is added to the sludge, and the reaction lasts for 20-30 minutes; then, FeCl3 accounting for 3%-8% of the dry sludge weight is added, and the reaction lasts for 10-15 minutes; the high-pressure squeezing pressure of the diaphragm plate-and-frame filter press is 1.5-2.0 MPa, and the squeezing time is 15-30 minutes.

5. The method according to claim 1, wherein the method is characterized by, In step S4, the immersed ultrafiltration membrane system adopts a membrane pore size of 0.01-0.1 μm, and the operation mode is constant flow filtration and air-water backwashing alternately, with a cycle of 40-60 minutes; during backwashing, the clean water in the reuse water pool is used and supplemented with compressed air scrubbing.

6. The method according to claim 1, wherein the method is characterized by, In step S3, the dry sludge cake is reused as a roadbed filling material together with tunnel spoil.

7. A railway tunnel engineering construction period production wastewater pressure filtration treatment system, characterized in that, The system comprises a grid conditioning pool, a high-efficiency vortex coagulator, a flocculation tank, an inclined-tube sedimentation tank, a sludge conditioning tank, a diaphragm plate-and-frame filter press, a high-pressure pump, an intermediate pool, an immersed ultrafiltration membrane system and a reuse water pool, wherein the grid conditioning pool is connected to the high-efficiency vortex coagulator, the high-efficiency vortex coagulator is connected to the flocculation tank, the flocculation tank is connected to the inclined-tube sedimentation tank, one side of the flocculation tank is connected to the sludge conditioning tank, the sludge conditioning tank is connected to the diaphragm plate-and-frame filter press, the diaphragm plate-and-frame filter press is connected to the intermediate pool, the other side of the inclined-tube sedimentation tank is connected to the intermediate pool, the intermediate pool is connected to the immersed ultrafiltration membrane system and the reuse water pool, and the immersed ultrafiltration membrane system and the reuse water pool are connected to the reuse water pool.

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