Wastewater treatment and recycling system and wastewater treatment process

Abstract

The invention discloses a wastewater treatment and recycling system which comprises a pH (potential of hydrogen) regulating tank, a silicon removal reaction tank, a first ceramic flat sheet membrane ultrafiltration tank, a fluorine removal reaction tank and a second ceramic flat sheet membrane ultrafiltration tank which are sequentially connected in series through a pipeline, and the pH regulating tank, the silicon removal reaction tank and the first ceramic flat sheet membrane ultrafiltration tank are alkaline wastewater treatment systems; the fluorine removal reaction tank and the second ceramic flat sheet membrane ultrafiltration tank are an acidic wastewater treatment system which is used for wastewater treatment, acid-alkali wastewater is subjected to quality-divided treatment and then input into the system for wastewater treatment, and alkaline wastewater is subjected to chemical silicon removal in the alkaline wastewater treatment system and then input into the acidic wastewater treatment system to be mixed with the acidic wastewater; according to the present invention, the common chemical method is adopted to remove fluorine, such that the wastewater treatment process is shortened, the ceramic flat sheet membrane ultrafiltration tank is adopted to perform filtration after the silicon removal and the fluorine removal, the flux is large, the membrane aperture is small, the water recovery amount can be improved, the extremely small reactant can be directly separated, the occupation area of the whole system is further reduced, and the process flow is simplified.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, in particular to a wastewater treatment and reuse system and a wastewater treatment process. Background Art

[0002] In recent years, the treatment of fluorine- and silicon-containing acid-base wastewater has become a hot topic, especially the treatment of acid-base wastewater generated by the photovoltaic power generation industry. The rapid development of the photovoltaic power generation industry has led to a surge in the global market demand for photovoltaic cells. Photovoltaic cells are mainly made of silicon wafers as raw materials. In the production process of photovoltaic cells, one of the basic principles of the wet process used in the front end is to use hydrofluoric acid, sodium hydroxide and other media to react with silicon wafers. The process includes immersing the silicon wafers in an acid tank or an alkali tank, taking them out and then washing them with pure water. Therefore, the wet process will produce a large amount of acid-base wastewater, and the main pollutant of acidic wastewater is fluorine, also known as fluorine-containing wastewater. Alkaline wastewater is mainly alkaline pollution and contains a large amount of silicon. Therefore, from the perspective of energy conservation and emission reduction, acid-base wastewater needs to develop a corresponding wastewater reuse process system.

[0003] The Chinese invention patent with application number 202211406173.4 and patent name "A TOPCon photovoltaic cell wastewater treatment and reuse system and treatment method" discloses a photovoltaic cell wastewater treatment and reuse system and treatment method, the system includes a concentrated acid / concentrated alkali wastewater treatment system, a dilute acid / dilute alkali wastewater treatment system and a biochemical treatment system; concentrated acid wastewater and concentrated alkali wastewater are input into the concentrated acid / concentrated alkali wastewater treatment system, and pass through the primary reaction tank, primary sedimentation tank, secondary reaction tank, secondary sedimentation tank, tertiary reaction tank and tertiary sedimentation tank of the system in sequence, thereby achieving wastewater Fluoride removal; dilute acid wastewater and dilute alkali wastewater are input into the dilute acid / dilute alkali wastewater treatment system, and pass through the acid-base neutralization rough adjustment tank, acid-base neutralization fine adjustment tank, pretreatment system, ultrafiltration system and RO reverse osmosis system of the system in sequence. The generated fresh water is pumped to the reuse point, and the impurities intercepted by the ultrafiltration system and the concentrated water treated by the RO reverse osmosis system are then introduced into the primary reaction tank of the concentrated acid / concentrated alkali wastewater treatment system for subsequent tertiary reaction and precipitation treatment; the biochemical treatment system includes an ammonia nitrogen wastewater / domestic sewage collection tank and a denitrification tank, A / O biochemical tank and secondary sedimentation tank connected in sequence, which are used to treat ammonia nitrogen wastewater and domestic sewage.

[0004] However, this type of wastewater treatment and reuse system and wastewater treatment process has the following problems: (1) It only uses the concentration of wastewater as the standard for input into the concentrated acid / concentrated alkali wastewater treatment system and the dilute acid / dilute alkali wastewater treatment system. Concentrated acid wastewater, concentrated alkali wastewater, dilute acid wastewater and dilute alkali wastewater are only collected and classified according to the acidity and alkalinity of the wastewater during the static pretreatment in the front-end collection tanks of the two systems. However, the acid and alkali wastewaters are still mixed and treated in the subsequent treatment stages such as fluoride removal, resulting in many processes and being relatively cumbersome. (2) In the concentrated acid / concentrated alkali wastewater treatment system, since the reactant particles produced by chemical fluoride and silicon removal are extremely fine and difficult to precipitate, a three-stage precipitation and reaction tank is used, which makes the overall system occupy a large area. The process flow is complicated. A large amount of flocculants and PAM reagents need to be added to each stage of the reaction tank to improve the sedimentation efficiency and obtain the supernatant. The dosage of the reagents is large and the cost is high. (3) In the dilute acid / dilute alkali wastewater treatment system, the RO reverse osmosis system has high requirements for the quality of the influent water. Therefore, it is necessary to set up sand filtration and activated carbon pretreatment in the upstream of the ultrafiltration system. At the same time, the water treated by the ultrafiltration system and the RO reverse osmosis system cannot meet the water quality requirements of the ultrapure water used in the photovoltaic cell factory and can only be downgraded for use. The amount of recycled water is generally only about 75%. Compared with the higher investment and operation and maintenance costs of the RO reverse osmosis system, the performance and function of the RO reverse osmosis system are not fully utilized, the cost performance is low, and resources are wasted. Summary of the invention

[0005] In view of the shortcomings of the above-mentioned existing wastewater treatment and reuse systems, such as acid-base mixed wastewater being classified according to concentration and then left to stand and then mixed for treatment, complicated procedures, difficulty in precipitating fine reactants produced by chemical fluorine and silicon removal and the need to increase the amount of chemicals added and the area occupied by the sedimentation tank, excess treatment performance of the RO reverse osmosis system, and low cost performance, the applicant provides a wastewater treatment and reuse system with a reasonable structure, which respectively inputs the acid-base wastewater into the alkaline wastewater treatment system and the acidic wastewater treatment system for water treatment after separation treatment, and utilizes a ceramic flat membrane ultrafiltration tank to precipitate and filter and separate the fine reactants, thereby replacing the original sedimentation tank and RO reverse osmosis system, saving the amount of chemicals added and the overall area occupied by the system. The wastewater treatment process using this system shortens the wastewater treatment process and improves the efficiency of wastewater treatment and water recovery while ensuring that the final water quality meets the reuse standard.

[0006] The technical solutions adopted by the present invention and the technical effects achieved are as follows: A wastewater treatment and reuse system comprises a pH regulating tank, a silicon removal reaction tank, a first ceramic flat membrane ultrafiltration tank, a fluorine removal reaction tank and a second ceramic flat membrane ultrafiltration tank which are sequentially connected in series through pipelines, wherein the pH regulating tank, the silicon removal reaction tank and the first ceramic flat membrane ultrafiltration tank are alkaline wastewater treatment systems, and the fluorine removal reaction tank and the second ceramic flat membrane ultrafiltration tank are acidic wastewater treatment systems.

[0007] As a further improvement of the above technical solution: The alkaline wastewater enters the pH adjustment tank of the alkaline wastewater treatment system; part of the acidic wastewater enters the pH adjustment tank to mix with the alkaline wastewater, and part enters the defluorination reaction tank of the acidic wastewater treatment system.

[0008] The first ceramic flat membrane ultrafiltration tank and the second ceramic flat membrane ultrafiltration tank both have a bottom aeration device, a plurality of membrane filtration components in the middle, and a top backwashing device, and ceramic flat membranes are arranged in the membrane filtration components.

[0009] A spray device is also provided on the top of the first ceramic flat membrane ultrafiltration tank and the second ceramic flat membrane ultrafiltration tank.

[0010] The ceramic flat membrane comprises a support layer and a filter layer. The support layer is made of silicon carbide or alumina ceramic material, and the filter layer is made of silicon carbide material with a purity of more than 90%.

[0011] The system of the present invention treats acidic and alkaline wastewaters by separating them into different qualities before inputting them into the system for wastewater treatment. Alkaline wastewater is first desiliconized by chemical method in the alkaline wastewater treatment system and then inputted into the acidic wastewater treatment system for mixing with the acidic wastewater for chemical defluorination. The process of wastewater treatment is shortened and the wastewater treatment efficiency is improved. After desiliconization and defluorination, a ceramic flat membrane ultrafiltration tank is used for filtration, replacing a sedimentation tank and an RO reverse osmosis system. The ceramic flat membrane ultrafiltration tank can increase the amount of recycled water due to its high mechanical strength and large flux. The ceramic flat membrane has a small membrane pore size and can directly separate extremely small reactants generated by chemical desiliconization and defluorination, thereby achieving better precipitation and filtration effects, further reducing the floor space of the entire system and streamlining the process flow, and can also reduce maintenance costs. The ceramic flat membrane has a high cost-effectiveness ratio. The surface of the ceramic flat membrane is also relatively smooth and easy to clean, thereby improving work efficiency.

[0012] The inner cavity of the defluorination reaction pool is divided into two compartments connected in series; the input end and the output end of the first ceramic flat membrane ultrafiltration pool and the second ceramic flat membrane ultrafiltration pool are both provided with flow meters. In the present invention, the defluorination reaction pool is divided into two compartments, so that different defluorination agents can be added to the two compartments respectively to fully react and improve the defluorination efficiency.

[0013] A wastewater treatment process using a wastewater treatment and reuse system, comprising the following wastewater treatment steps: S1: Separate and treat acid and alkaline wastewater; S2: In the alkaline wastewater treatment system, the alkaline wastewater is sequentially input into the pH adjustment tank, the silicon removal reaction tank and the first ceramic flat ultrafiltration tank, a small amount of acidic wastewater is injected into the pH adjustment tank and the pH value of the wastewater is adjusted to 8-10, the wastewater is input into the silicon removal reaction tank and reacts with the silicon removal agent input therein to form a water-insoluble compound, the wastewater then enters the first ceramic flat ultrafiltration tank and the compound is precipitated and filtered to separate, thereby obtaining alkaline produced water and concentrated liquid, and the alkaline produced water is input into the defluorination reaction tank of the acidic wastewater treatment system; S3: In the acidic wastewater treatment system, the remaining acidic wastewater is mixed with the alkaline produced water obtained in S2 and sequentially input into the defluorination reaction tank and the second ceramic flat membrane ultrafiltration tank. The wastewater is input into the defluorination reaction tank and fully reacts with the defluorination agent input into the defluorination reaction tank to form water-insoluble compounds. The wastewater then enters the second ceramic flat membrane ultrafiltration tank and the compounds are precipitated, filtered and separated to obtain the final produced water and concentrated liquid.

[0014] The wastewater treatment process using the above wastewater treatment and reuse system is to first separate the acid and alkaline wastewater into different qualities before inputting it into the system for wastewater treatment; the alkaline wastewater is first desiliconized by chemical methods in the alkaline wastewater treatment system and then input into the acidic wastewater treatment system to be mixed with the acidic wastewater for chemical defluorination, thereby shortening the wastewater treatment process and improving the wastewater treatment efficiency.

[0015] As a further improvement of the above technical solution: The process also includes the following steps: the water flow rates of the first ceramic flat-plate ultrafiltration pool and the second ceramic flat-plate membrane ultrafiltration pool are both set to 50-100 liters / m2 / hour, the ratio of the inlet flow rate of the first ceramic flat-plate ultrafiltration pool and the outlet flow rate of its water production pump is set to 75%-85%, and the ratio of the inlet flow rate to the outlet flow rate of the second ceramic flat-plate membrane ultrafiltration pool is set to 85%-95%, and the remaining concentrated liquid is directly discharged continuously and treated separately.

[0016] The method also includes the following steps: controlling the ratio of the inlet and outlet flow rates of the first ceramic flat membrane ultrafiltration pool and the second ceramic flat membrane ultrafiltration pool and maintaining a balance, not directly discharging the concentrated liquid and continuously retaining it in the two ultrafiltration membrane pools; when the water production flow rate of the two ultrafiltration membrane pools reaches 10 to 20 times the volume, stopping the filtration of the compound, discharging all the mixed liquids in the two ultrafiltration membrane pools as concentrated liquid, and restarting the filtration.

[0017] The present invention can control the water output of alkaline water production or final wastewater treatment and concentrated liquid by controlling the ratio of the water inlet of the first ceramic flat membrane ultrafiltration pool and the water outlet flow rate of the second ceramic flat membrane ultrafiltration pool and the water outlet flow rate of the water production pump, and fully utilizes the concentrating capacity of the ceramic flat membrane. Two different subsequent treatment schemes can be performed on the concentrated liquid, saving costs while avoiding pollution.

[0018] The defluoridation agent is composed of at least two or more of lime milk, calcium chloride, polymer defluoridation agent, and polyaluminium chloride; the desiliconization agent is composed of at least two or more of magnesium oxide, sodium metaaluminate, aluminium iron silicate polymer, and polyaluminium chloride. The present invention can select different desiliconization agents and defluoridation agents according to the cost of the agents, thereby improving the efficiency of defluorination and desiliconization and saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a process flow chart of the present invention.

[0020] Figure 2 It is a schematic diagram of the structure of the system of the present invention.

[0021] Figure 3 It is a schematic structural diagram of the first ceramic flat membrane ultrafiltration tank or the second ceramic flat membrane ultrafiltration tank of the present invention.

[0022] In the figure: 1. pH adjustment tank; 2. Silicon removal reaction tank; 3. First ceramic flat membrane ultrafiltration tank; 4. Fluoride removal reaction tank; 5. Second ceramic flat membrane ultrafiltration tank; 6. Membrane filtration assembly; 61. Support layer; 62. Filter layer; 7. Backwashing device; 8. Spraying device; 9. Aeration device; 10. Flow meter; 11. pH monitoring instrument; 12. Silicate online detection instrument; 13. Stirring device. DETAILED DESCRIPTION

[0023] The specific implementation of the present invention will be described below in conjunction with the accompanying drawings. Example

[0024] like Figure 1 , 2As shown, the wastewater treatment and reuse system of the present invention comprises a pH regulating tank 1, a silicon removal reaction tank 2, a first ceramic flat membrane ultrafiltration tank 3, a fluorine removal reaction tank 4 and a second ceramic flat membrane ultrafiltration tank 5 which are sequentially connected in series through pipelines, wherein the pH regulating tank 1, the silicon removal reaction tank 2 and the first ceramic flat membrane ultrafiltration tank 3 are alkaline wastewater treatment systems, the fluorine removal reaction tank 4 and the second ceramic flat membrane ultrafiltration tank 5 are acidic wastewater treatment systems, the acidic wastewater can be respectively input into the pH regulating tank 1 and the fluorine removal reaction tank 4 through pipelines and opening and closing valves, and the alkaline wastewater is input into the pH regulating tank 1. After the acid and alkaline wastewater is treated by separation, it is input into the system for wastewater treatment. The alkaline wastewater is first desiliconized by chemical method in the alkaline wastewater treatment system and then input into the acidic wastewater treatment system to be mixed with the acidic wastewater for chemical defluorination. This shortens the wastewater treatment process and improves the wastewater treatment efficiency. After desiliconization and defluorination, two ceramic flat membrane ultrafiltration tanks are used for filtration, replacing the sedimentation tank and RO reverse osmosis system. The ceramic flat membrane ultrafiltration tank has the characteristics of high mechanical strength and large water flow, which can increase the amount of recycled water. The ceramic flat membrane has a small membrane pore size and can directly separate the extremely small reactants produced by chemical desiliconization and defluorination, thereby achieving better precipitation and filtration effects, further reducing the footprint of the entire system and streamlining the process flow, which can also reduce maintenance costs and has a high cost performance. The surface of the ceramic flat membrane is also relatively smooth, easy to clean, and improves work efficiency.

[0025] The alkaline wastewater to be treated and a small amount of existing acidic wastewater are input into the pH adjustment tank 1, and the pH of the wastewater is adjusted. The pH adjustment tank 1 is provided with a stirring device 13, a pH monitoring instrument 11 and a silicate online detection instrument 12. The stirring device 13 is used to stir and mix the acidic and alkaline wastewater, the pH monitoring instrument 11 is used to monitor the pH value change of the wastewater, control the amount of acidic wastewater added to adjust the wastewater to the required pH value, and the silicate online detection instrument 12 is used to monitor the silicate content in the water, and then adjust and control the amount of silicon removal agent added in the subsequent silicon removal reaction tank 2.

[0026] A desiliconizing agent is added to the desiliconizing reaction tank 2 to chemically treat the wastewater. The desiliconizing agent is composed of at least two or more of magnesium oxide, sodium aluminate, aluminum iron silicate polymer, and polyaluminium chloride, and can be selected for use according to the cost of the agent. An aeration device 9, a mechanical stirring device 13 and a pH monitoring instrument 11 are provided in the desiliconizing reaction tank 2. The stirring device 13 facilitates the desiliconizing agent to fully react with the silicon in the water to produce a reactant insoluble in water. The aeration device 9 ensures that while the desiliconizing reaction is fully carried out, the lime milk in the desiliconizing agent is prevented from precipitating and hardening.

[0027] The defluorination reaction tank 4 is input with the acidic wastewater to be treated and the alkaline produced water output by the first ceramic flat membrane ultrafiltration tank 3. The defluorination reaction tank 4 is provided with an aeration device 9, a stirring device 13 and a pH monitoring instrument 11. The pH monitoring instrument 11 can be used to monitor the pH value change in the defluorination reaction tank 4, and then control the acid-base ratio of the incoming water and the dosage of the defluorination agent. The defluorination reaction tank 4 is divided into two compartments connected in series, and different defluorination agents are respectively added to the two compartments. The defluorination agent is composed of at least two or more of lime milk, calcium chloride, polymer defluorination agent, and polyaluminum chloride, and can be selected according to the cost of the agent.

[0028] like Figure 3 As shown, the first ceramic flat membrane ultrafiltration tank 3 and the second ceramic flat membrane ultrafiltration tank 5 are used to filter the reactants in the wastewater output from the silicon removal reaction tank 2 and the fluorine removal reaction tank 4, respectively. Both ultrafiltration tanks have a bottom aeration device 9, a plurality of membrane filtration components 6 in the middle, and a top backwashing device 7 and a spraying device 8. The number of membrane filtration components 6 can be determined according to the project water volume. An asymmetric ceramic flat membrane is arranged on the membrane filtration component 6, which includes a support layer 61 and a filter layer 62. The support layer 61 is made of silicon carbide or alumina ceramic material, and the filter layer 62 is a silicon carbide material with a purity of more than 90%. The filtration accuracy of the ceramic flat membrane is 20~100 nanometers. In this embodiment, the support layer 61 and the filter layer 62 are both made of pure silicon carbide material. The filtration accuracy of the ceramic flat membrane is 100 nanometers. The filtration accuracy is relatively high, and the fine reactants produced during silicon removal and fluorine removal can be filtered and separated, thereby ensuring the quality of the produced water, and there is no need to perform subsequent The wastewater is added into the traditional sedimentation tank and precipitated with chemicals, which saves the amount of chemicals added; the aeration device 9 can flush the surface of the ceramic flat membrane, slow down the fouling speed of the flat membrane, maintain a stable filtering capacity, and prevent the reactants in the wastewater from being calcified in the two ultrafiltration tanks; the backwashing device 7 and the spraying device 8 are arranged above the membrane filtration component 6, and the backwashing device 7 starts and closes the backwashing pump at a regular time, so as to reversely inject the produced water in the two ultrafiltration tanks into the membrane filtration component 6, so that the pollutants deposited on the surface of the ceramic flat membrane fall off to restore its filtering capacity, and the spraying device 8 can be used to spray washing water.

[0029] The input and output ends of the first ceramic flat membrane ultrafiltration pool 3 and the second ceramic flat membrane ultrafiltration pool 5 are both provided with flow meters 10, and the flow rates of the water production pumps of the two ultrafiltration pools can be controlled according to the values ​​of the flow meters 10, thereby directly controlling the ratio of the inlet and outlet flow rates and the discharge volume of the concentrated liquid of the first ceramic flat membrane ultrafiltration pool 3 or the second ceramic flat membrane ultrafiltration pool 5. The concentrated liquid contains a large amount of chemical reactants and needs further treatment. PAM reagents can be added to the concentrated liquid for precipitation treatment, and then it can be directly input into the external sludge concentration pool and pressed into mud cakes.

[0030] The wastewater treatment process using the system of the present invention is as follows: first, the acidic and alkaline wastewaters are treated separately. In the alkaline wastewater treatment system, the alkaline wastewater is sequentially input into the pH adjustment tank 1, the silicon removal reaction tank 2 and the first ceramic flat ultrafiltration tank 3. A small amount of existing acidic wastewater is injected into the pH adjustment tank 1 to adjust the pH value of the wastewater to 8-10. In this embodiment, the pH value is adjusted to 8.5. Under normal circumstances, the total amount of acidic wastewater generated by photovoltaic cell companies is more than that of alkaline wastewater. Therefore, only a small amount of acidic wastewater needs to be introduced into the pH adjustment tank 1. Then, the wastewater is input into the desiliconization reaction tank 2 and reacts with the desiliconization agent put into the tank. In this embodiment, the desiliconization agent is polyaluminum chloride and sodium aluminate. The dosage of polyaluminum chloride is 20 mg / L, and the dosage of sodium aluminate is selected according to the silicon concentration in the water. The chemical formula of the reaction in the tank is 2Na2SiO3+2NaAlO2+2H2O=Na2Al2Si2O8+4NaOH. After sufficient reaction, the mass ratio of silicate in the tank is 1.5~2:1, and the pH value is 8~10. A water-insoluble sodium aluminosilicate (Na2Al2Si2O8) compound is generated in the tank, and the particles of the compound are extremely small. The wastewater after silicon removal enters the first ceramic flat membrane ultrafiltration pool 3 for muddy water filtration and separation to obtain alkaline produced water and concentrated liquid. In this embodiment, the water flow rate of the first ceramic flat membrane ultrafiltration pool 3 is set to 50~100 liters / ㎡ / hour, and the ratio of the inlet water of the first ceramic flat membrane ultrafiltration pool 3 and the outlet water flow rate of its produced water pump is set to 75%-85%, 80% in this embodiment, and the remaining 20% ​​concentrated liquid is continuously discharged for separate treatment, and the alkaline produced water of the first ceramic flat membrane ultrafiltration pool 3 enters the defluorination reaction pool 4 of the acidic wastewater treatment system. The backwashing device 7 of the first ceramic flat membrane ultrafiltration pool 3 performs a backwashing operation on the ceramic flat membrane every 20 minutes. The water flow rate of the ceramic flat membrane during backwashing is 500 liters / ㎡ / hour, and the backwashing duration is 20 seconds.

[0031] In the acidic wastewater treatment system, the remaining acidic wastewater and alkaline wastewater treatment system alkaline water produced are sequentially input into the defluorination reaction tank 4 and the second ceramic flat membrane ultrafiltration tank 5. The defluorination reaction tank 4 is divided into two compartments connected in series. A mixture of lime milk and calcium chloride is added to the first compartment of the defluorination reaction tank 4, and polyaluminum chloride is added to the second compartment. The effect of each defluorination agent can be fully exerted. The pH value in the first compartment is adjusted to 8-9, and the pH value in the second compartment is adjusted to 7-8. The pH value in the second compartment is the pH value of the effluent. In this embodiment, the pH value of the wastewater in the first compartment is 9.0, and the pH value of the effluent is 7.0. The defluorination agent fully reacts with the fluoride ions in the wastewater to form a water-insoluble compound. The wastewater then enters the second ceramic flat membrane ultrafiltration pool 5 for precipitation, filtration and separation of compounds, and then obtains the final water production and concentrated liquid. The filtration water flow rate of the second ceramic flat membrane ultrafiltration pool 5 is set to 50~100 liters / ㎡ / hour, and the inlet and outlet flow rate ratio of the second ceramic flat membrane ultrafiltration pool 5 is set to 85%~95%, 90% in this embodiment, and the remaining 10% concentrated liquid is continuously discharged for separate treatment, and the turbidity of the final water production is ≤3NTU, fluoride ion ≤2.0mg / L, silicon ≤30mg / L, which can be directly reused to the pure water station as raw water, and the recovery rate of alkaline wastewater is 80%, and the reuse rate of mixed wastewater is 90%, saving water and reducing the total wastewater discharge. The second ceramic flat membrane ultrafiltration pool 5 backwashes the ceramic flat membrane once every 20 minutes. The water flow rate of the ceramic flat membrane during backwashing is 500 liters / ㎡ / hour, and the backwashing duration is 20 seconds. Example

[0032] The present embodiment is different from the embodiment 1 in that the concentrated liquid produced in the first ceramic flat membrane ultrafiltration pool 3 and the second ceramic flat membrane ultrafiltration pool 5 is not directly discharged for treatment. By controlling the flow rate of the water production pump, the ratio of the inlet and outlet flow rates of the first ceramic flat membrane ultrafiltration pool 3 or the second ceramic flat membrane ultrafiltration pool 5 and the discharge amount of the concentrated liquid are directly controlled. In the present embodiment, the inlet and outlet flow rates of the two ultrafiltration pools are kept balanced, and no concentrated liquid will be discharged from the two ultrafiltration membrane pools. The reactants in the wastewater will be continuously retained in the two ultrafiltration membrane pools, and will be discharged after being accumulated to a certain amount, making full use of the concentration capacity of the ceramic flat membrane. When the water production flow rate reaches 10 to 20 times the volume of the two ultrafiltration membrane pools, the filtration is stopped, and the mixed liquid in the two ultrafiltration membrane pools is completely discharged as concentrated liquid, and the filtration is restarted. The recovery rate of the mixed wastewater is 90% to 95%. Example

[0033] The present embodiment is different from the embodiment 1 in that, in the alkaline wastewater treatment system, hydrochloric acid or sulfuric acid is injected into the pH adjustment tank 1 to adjust the pH value of the wastewater to 8-10.

[0034] The above description is an explanation of the present invention, not a limitation of the present invention. The present invention may be modified in any form without violating the spirit of the present invention.

Claims

1. A wastewater treatment and reuse system, characterized in that: The invention comprises a pH regulating tank (1), a silicon removal reaction tank (2), a first ceramic flat membrane ultrafiltration tank (3), a fluorine removal reaction tank (4) and a second ceramic flat membrane ultrafiltration tank (5) which are sequentially connected in series via pipelines, wherein the pH regulating tank (1), the silicon removal reaction tank (2) and the first ceramic flat membrane ultrafiltration tank (3) are alkaline wastewater treatment systems, and the fluorine removal reaction tank (4) and the second ceramic flat membrane ultrafiltration tank (5) are acidic wastewater treatment systems.

2. The wastewater treatment and reuse system according to claim 1, characterized in that: The alkaline wastewater enters the pH adjustment tank (1) of the alkaline wastewater treatment system; part of the acidic wastewater enters the pH adjustment tank (1) to be mixed with the alkaline wastewater, and part of the acidic wastewater enters the defluorination reaction tank (4) of the acidic wastewater treatment system.

3. The wastewater treatment and reuse system according to claim 1, characterized in that: The first ceramic flat membrane ultrafiltration tank (3) and the second ceramic flat membrane ultrafiltration tank (5) both have a bottom aeration device (9), a plurality of membrane filtration components (6) in the middle, and a top backwashing device (7), wherein a ceramic flat membrane is arranged in the membrane filtration component (6).

4. The wastewater treatment and reuse system according to claim 3, characterized in that: A spray device (8) is also provided on the top of the first ceramic flat membrane ultrafiltration tank (3) and the second ceramic flat membrane ultrafiltration tank (5).

5. The wastewater treatment and reuse system according to claim 3, characterized in that: The ceramic flat membrane comprises a support layer (61) and a filter layer (62); the support layer (61) is made of silicon carbide material or alumina ceramic material, and the filter layer (62) is made of silicon carbide material with a purity of more than 90%.

6. The wastewater treatment and reuse system according to claim 1, characterized in that: The inner cavity of the defluorination reaction pool (4) is divided into two compartments connected in series; the input end and the output end of the first ceramic flat membrane ultrafiltration pool (3) and the second ceramic flat membrane ultrafiltration pool (5) are both provided with flow meters (10).

7. A wastewater treatment process using the wastewater treatment and reuse system according to claim 1, characterized in that: The following wastewater treatment steps are included: S1: Separate and treat acid and alkaline wastewater; S2: In the alkaline wastewater treatment system, the alkaline wastewater is sequentially input into the pH adjustment tank (1), the silicon removal reaction tank (2) and the first ceramic flat ultrafiltration tank (3), a small amount of acidic wastewater is injected into the pH adjustment tank (1) and the pH value of the wastewater is adjusted to 8-10, the wastewater is input into the silicon removal reaction tank (2) and reacts with the silicon removal agent input therein to form water-insoluble compounds, the wastewater then enters the first ceramic flat ultrafiltration tank (3) and the compounds are precipitated and filtered to separate, thereby obtaining alkaline produced water and concentrated liquid, and the alkaline produced water is input into the fluorine removal reaction tank (4) of the acidic wastewater treatment system; S3: In the acid wastewater treatment system, the remaining acid wastewater is mixed with the alkaline produced water obtained in S2 and sequentially input into the defluorination reaction tank (4) and the second ceramic flat membrane ultrafiltration tank (5). The wastewater is input into the defluorination reaction tank (4) and fully reacts with the defluorination agent input into the defluorination reaction tank (4) to form water-insoluble compounds. The wastewater then enters the second ceramic flat membrane ultrafiltration tank (5) and the compounds are precipitated and filtered to separate, thereby obtaining final produced water and concentrated liquid.

8. The wastewater treatment process according to claim 7, characterized in that: The following steps are also included: The water flow rates of the first ceramic flat-plate ultrafiltration pool (2) and the second ceramic flat-plate membrane ultrafiltration pool (5) are both set to 50-100 liters / m2 / hour, the ratio of the inlet flow rate of the first ceramic flat-plate ultrafiltration pool (2) to the outlet flow rate of its water production pump is set to 75%-85%, and the ratio of the inlet flow rate to the outlet flow rate of the second ceramic flat-plate membrane ultrafiltration pool (5) is set to 85%-95%, and the remaining concentrated liquid is directly discharged continuously and treated separately.

9. The wastewater treatment process according to claim 7, characterized in that: The following steps are also included: The ratio of the inlet and outlet flow rates of the first ceramic flat membrane ultrafiltration pool (3) and the second ceramic flat membrane ultrafiltration pool (5) is controlled and kept in balance, and the concentrated liquid is not directly discharged and is continuously retained in the two ultrafiltration membrane pools. When the water production flow rate of the two ultrafiltration membrane pools reaches 10 times to 20 times the volume, the filtration of the compound is stopped, and the mixed liquid in the two ultrafiltration membrane pools is completely discharged as the concentrated liquid, and the filtration is restarted.

10. The wastewater treatment process according to claim 7, characterized in that: The defluorinating agent is composed of at least two or more of lime milk, calcium chloride, polymer defluorinating agent, and polyaluminium chloride; the desiliconizing agent is composed of at least two or more of magnesium oxide, sodium aluminate, aluminium iron silicate polymer, and polyaluminium chloride.

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