CN116282668A - A system and method for the treatment and reuse of circulating water and sewage based on ceramic membranes - Google Patents

Abstract

The invention discloses a ceramic membrane-based treatment and recycling system and method for circulating water discharge sewage, and belongs to the technical field of water treatment. The device comprises a pretreatment unit, a high-grade oxidation unit, a ceramic membrane treatment unit and a high-pressure reverse osmosis unit which are sequentially connected; the pretreatment unit is used for adjusting the pH of the water body to be treated and reducing suspended matters and comprises a mixing tank and a triple tank which are connected in sequence; the advanced oxidation unit comprises a catalytic oxidation tower, wherein a catalyst is filled in the catalytic oxidation tower and is connected with an ozone generator; the ceramic membrane treatment unit comprises a process tank and a ceramic membrane filtration assembly which are connected in sequence; the high-pressure reverse osmosis unit comprises a filtering tank, a buffer tank, a cartridge filter, a reverse osmosis high-pressure pump and a high-pressure reverse osmosis component which are connected in sequence. In the whole, the treatment and recycling system of the circulating water sewage based on the ceramic membrane can reduce the amount of the circulating water sewage by more than 85%, and the whole system can stably run for a long time.

Description

A system and method for the treatment and reuse of circulating water and sewage based on ceramic membranes

technical field

The invention belongs to the technical field of water treatment, and in particular relates to a system and method for treating and reusing circulating water and sewage based on ceramic membranes.

Background technique

The information disclosed in this background section is only intended to increase the understanding of the general background of the present invention, and is not necessarily taken as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

At present, with the continuous increase of environmental pressure, zero discharge of wastewater is the development trend of the current wastewater treatment industry. Zero discharge of wastewater refers to the pretreatment, reuse, concentration, and solidification of wastewater, and finally forms solid waste to be transported abroad, which is no longer carried out from the factory area. drain. Generally, the supplementary water of circulating water and sewage is usually of poor water quality, water quality pollutants are highly concentrated, and various pollution indexes are high, especially the high content of suspended solids, high salt content, and complex types of metal ions. To achieve zero discharge of wastewater, the treatment and concentration of circulating water and sewage is the key step for zero discharge of factory wastewater. The establishment of an efficient and stable zero discharge treatment process for circulating water and sewage is the core that determines the stability of the process of zero discharge of factory wastewater. The key steps of the sewage zero discharge treatment process are the pretreatment and concentration of circulating water and sewage. A stable pretreatment and concentration unit can greatly reduce the final evaporation of circulating water and sewage, reduce energy consumption and water treatment costs, Promote the construction and promotion of zero-discharge technology for circulating water and sewage.

The recovery and concentration of circulating water sewage is usually the membrane method. Although the membrane method has obtained many application cases for the concentration of circulating water sewage and concentrated water, membrane fouling and membrane fouling usually occur, which makes it difficult to restore the membrane flux and eventually affects the membrane. normal operation of the system. This is because the normal operation of the membrane system depends on the pretreatment process. The treatment efficiency of the pretreatment process not only affects the operation stability and service life of the membrane system, but also affects the treatment efficiency of the membrane system, that is, the concentration rate of wastewater by the membrane system. .

Therefore, there is an urgent need to develop a new and stable pretreatment and concentration process for circulating water effluent to achieve zero discharge of wastewater.

Contents of the invention

In order to solve the deficiencies of the prior art, the purpose of the present invention is to provide a system and method for the treatment and reuse of circulating water sewage sewage based on ceramic membranes. The water quality of the concentrated sewage sewage of power plant circulating water provided by the present invention is designed to be suitable for The circulating water sewage concentrated water pretreatment unit and membrane unit, based on the efficient and stable circulating water sewage pretreatment and membrane unit, realize the high concentration rate recovery of circulating water sewage.

In order to achieve the above object, the technical solution of the present invention is:

The first aspect of the present invention provides a ceramic membrane-based circulating water sewage treatment and reuse system, including a pretreatment unit, an advanced oxidation unit, a ceramic membrane treatment unit and a high-pressure reverse osmosis unit connected in sequence;

The pretreatment unit is used to adjust the pH of the water body to be treated and reduce suspended solids, including a mixing tank and a triple box connected in sequence;

The advanced oxidation unit includes a catalytic oxidation tower, which is filled with a catalyst and connected to an ozone generator;

The ceramic membrane processing unit includes a process tank and a ceramic membrane filter assembly connected in sequence;

The high-pressure reverse osmosis unit includes a filter tank, a buffer tank, a security filter, a high-pressure reverse osmosis pump, and a high-pressure reverse osmosis component connected in sequence.

Preferably, the pretreatment unit also includes a flocculant dosing pump and a flocculant tank, the flocculant tank is connected to the flocculant dosing pump, the flocculant dosing pump is connected to the flocculation tank in the triple box, and the flocculant tank The flocculant is transported to the flocculation box.

Preferably, the pretreatment unit also includes a cyclone, a filter feed box, and a sludge treatment device;

The cyclone is connected with the sewage outlet of the settling tank in the triple box, and is used for solid-liquid separation of sludge impurities. The solid outlet is connected with the material inlet of the filter feeding box, and the liquid outlet is connected with the mixing tank; the filter feed The material outlet of the material box is connected with the material inlet of the sludge treatment device.

Further preferably, the sludge treatment device is a vacuum disc filter or a vacuum belt dehydrator, and its liquid outlet is connected to a mixing tank.

Preferably, the advanced oxidation unit also includes a hydrogen peroxide dosing device, a dosing pump, a pipeline mixer, a cyclone, and a circulation pump;

The hydrogen peroxide dosing device is connected to the pipeline mixer through a pipeline, and the pipeline between the two is provided with a dosing pump; the pipeline mixing device is connected to the material inlet of the catalytic oxidation tower for mixing the water body to be treated with the hydrogen peroxide ; The cyclone is connected with the gas inlet of the catalytic oxidation tower, and is used to deliver air to the catalytic oxidation tower; the part between the top of the catalyst of the catalytic oxidation tower and the discharge port is provided with a circulation pipe, and the circulation pipe is connected with the circulation pump. It is used to retransmit the catalytically oxidized liquid in the catalytic oxidation tower to the bottom of the catalytic oxidation tower through the circulation pump, so that it can be catalytically oxidized.

Preferably, the advanced oxidation unit further includes a booster pump, and the material outlet of the catalytic oxidation tower is connected to the booster pump through a pipeline for pumping the water body to the ceramic membrane treatment unit.

Preferably, the ceramic membrane treatment unit further includes a plate heat exchanger, a cleaning tank, a feed pump, a main circulation pump, and a concentrated liquid transfer pump;

The ceramic membrane filter assembly includes multiple sets of parallel ceramic membrane tubes and water supply tanks connected to the ceramic membrane tubes; the main circulation pump connects different water supply tanks through pipelines;

The pipeline between the process tank and the ceramic membrane filter module is provided with a plate heat exchanger; the outlet pipe of the ceramic membrane filter module is provided with a branch connected to the cleaning tank, and the water from the cleaning tank is sent to the dope transfer pump or through the feeder The water is pumped out to the ceramic membrane filter assembly, so that the water body is filtered again.

Preferably, the filtration precision of the ceramic membrane tube is 50nm.

Preferably, the filter of the high-pressure reverse osmosis unit is a sand filter and an activated carbon filter connected in sequence;

The high-pressure reverse osmosis unit also includes a clean water tank, a first cleaning water delivery pump, a concentrated water tank, and a second cleaning water delivery pump; the clean water outlet of the high-pressure reverse osmosis module is connected to the water inlet of the clean water tank, and the clean water tank is passed through the first cleaning water delivery pump The water is discharged to the inlet of the high-pressure reverse osmosis module; the concentrated water outlet of the high-pressure reverse osmosis module is connected to the water inlet of the concentrated water tank, and the concentrated water tank is discharged to the high-efficiency evaporation unit through the second cleaning water pump for further processing.

In the second aspect of the present invention, a method for treating and reusing circulating water and sewage is provided, using the above-mentioned ceramic membrane-based circulating water and sewage treatment and recycling system to treat circulating water and sewage;

The catalytic oxidation tower is filled with the original sheet-shaped TiO ₂ catalyst with a thickness of 0.5cm, a diameter of 1.5cm, and a specific surface area of 55m ² /g; the ratio of the catalyst to the concentrated sewage of circulating water is 1:60; Ozone, the feeding time is 0.5h-2.5h; the transmembrane pressure difference of the high-pressure reverse osmosis treatment unit is always maintained at 0.1bar;

Send the water to be treated to the pretreatment unit, and adjust the pH to 9-10; the water from the pretreatment unit is sent to the advanced oxidation unit, and the COD, ammonia nitrogen and suspended solids in the water are removed in the advanced oxidation unit; the water from the advanced oxidation unit is sent to the ceramic membrane treatment unit , to filter the water body; the water from the ceramic membrane treatment unit is sent to the high-pressure reverse osmosis unit to desalinate and concentrate the water body.

The beneficial effects of the present invention are:

In the present invention, the circulating water sewage concentration and weight reduction process is mainly based on the reduction of waste water COD-suspension sedimentation-ceramic membrane treatment-reverse osmosis treatment. By optimizing and screening the COD reduction process, a pretreatment unit is established and a heterogeneous ceramic catalyst and The advanced oxidation treatment unit combined with hydrogen peroxide can reduce the COD of wastewater to 70%. At the same time, due to the destruction of the current steady state of the water body, some high-valent ions in the circulating water sewage also form particulate matter and separate from the water body, and then settle the suspended matter to form in the water. After the circulating water sewage after separating the large particles enters the ceramic membrane treatment unit, the ceramic membrane treatment unit can achieve a wastewater concentration efficiency of more than 96% on the basis of ensuring high-quality effluent, and the effluent of the ceramic membrane treatment unit After entering the high-pressure reverse osmosis unit, the high-pressure reverse osmosis treatment unit can achieve a wastewater recovery rate of more than 70%, and a desalination rate of more than 97%, which greatly reduces the amount of water that the circulating water blowdown concentrated water enters the evaporation unit. On the whole, the ceramic membrane-based circulating water sewage treatment and reuse system of the present invention can reduce the volume of circulating water sewage concentrated water by more than 85%, and the whole system can run stably for a long time.

Description of drawings

The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention.

Fig. 1 is the structure diagram of the treatment and reuse system of circulating water and sewage based on ceramic membrane in the present invention;

Fig. 2 is the structural diagram of the pretreatment unit in the treatment and reuse system of circulating water and sewage based on ceramic membrane in the present invention;

Fig. 3 is the structural diagram of the advanced oxidation treatment unit in the treatment and reuse system of circulating water and sewage based on ceramic membrane in the present invention;

Fig. 4 is the structural diagram of the difficult unit of the ceramic membrane in the treatment and reuse system of the circulating water and sewage based on the ceramic membrane in the present invention;

Fig. 5 is a structural diagram of a high-pressure reverse osmosis unit in the ceramic membrane-based circulating water sewage treatment and reuse system of the present invention.

Among them, 1: mixing tank, 2: raw water pump, 3: triple box, 4: flocculant dosing pump, 5: flocculant tank, 6: hydrocyclone, 7: filter feeding box, 8: sludge Processing device, 9: first process pump, 10: hydrogen peroxide dosing device, 11: dosing pump, 12: pipeline mixer, 13: cyclone, 14: catalytic oxidation tower, 15: circulation pump, 16: second process Pump, 17: process tank, 18: plate heat exchanger, 19: ceramic membrane filter assembly, 191: ceramic membrane tube, 192: water supply tank, 20: cleaning tank, 21: main circulation pump, 22: feed pump, 23 : concentrated liquid transfer pump, 24: sand filter, 25: activated carbon filter, 26: buffer tank, 27: security filter, 28: reverse osmosis high pressure pump, 29: high pressure reverse osmosis component, 30: concentrated water tank, 31 : clean water tank, 32: the second cleaning water delivery pump, 33: the first cleaning water delivery pump.

Detailed ways

In order to enable those skilled in the art to understand the technical solution of the present invention more clearly, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

Example 1

A treatment and reuse system for circulating water and sewage based on ceramic membranes, including a pretreatment unit, an advanced oxidation unit, a ceramic membrane treatment unit and a high-pressure reverse osmosis unit connected in sequence.

The pretreatment unit is used to adjust the pH of the water body to be treated and reduce suspended solids, including a mixing tank 1, a raw water pump 2, a triple tank 3, and a first process pump 9 connected in sequence, and the first process pump 9 is used to discharge the triple tank 3 Pumped to advanced oxidation unit; also includes flocculant dosing pump 4, flocculant tank 5, hydrocyclone 6, filter feeding box 7, sludge treatment device 8. The flocculant tank 5 is connected to the flocculant dosing pump 4, and the flocculant dosing pump 4 is connected to the flocculation tank in the triple box 3, and the flocculant in the flocculant tank 5 is transported to the flocculation tank. The hydrocyclone 6 is connected to the sewage outlet of the settling tank in the triple box 3, and is used for solid-liquid separation of the sludge impurities. Its solid outlet is connected to the material inlet of the filter feeding box 7, and its liquid outlet is connected to the mixing tank 1; The material outlet of the filter feeding box 7 is connected to the material inlet of the sludge treatment device 8 , and the liquid outlet of the sludge treatment device 8 is connected to the mixing tank 1 . The sludge treatment device 8 is a vacuum disc filter or a vacuum belt dehydrator.

Advanced oxidation unit comprises catalytic oxidation tower 14, is filled with catalyzer and is connected with ozone generator in catalytic oxidation tower 14; Second process pump 16 . Hydrogen peroxide dosing device 10 links to each other with pipeline mixer 12 by pipeline, and the pipeline between the two is provided with dosing pump 11; The hydrogen peroxide is mixed; the cyclone 13 is connected with the gas inlet of the catalytic oxidation tower 14, and is used to deliver air to the catalytic oxidation tower; the part between the top of the catalyst of the catalytic oxidation tower 14 and the discharge port is provided with a circulation pipe, and the circulation pipe and the circulation pump 15 Connected, it is used to retransmit the catalytically oxidized liquid in the catalytic oxidation tower to the bottom of the catalytic oxidation tower through the circulation pump, so that it can be catalyzed and oxidized. The second process pump 16 pumps the output from the catalytic oxidation tower 14 to the ceramic membrane treatment unit.

The ceramic membrane treatment unit includes a process tank 17 and a ceramic membrane filter assembly 19 connected in sequence. It also includes a plate heat exchanger 18 , a cleaning tank 20 , a feed pump 22 , a main circulation pump 21 , and a dope transfer pump 23 . The ceramic membrane filter assembly 19 includes multiple sets of parallel ceramic membrane tubes 191 and a water supply tank 192 connected to the ceramic membrane tubes; the main circulation pump 21 connects different water supply tanks through pipelines. A plate heat exchanger 18 is provided on the pipeline between the process tank 17 and the ceramic membrane filter assembly 19; a branch connected to the cleaning tank 20 is provided on the water outlet pipeline of the ceramic membrane filter assembly 19, and the water from the cleaning tank 20 is sent to the dope transfer pump 23 or through the feed pump 22 to discharge the water to the ceramic membrane filter assembly 19, so that the water body is filtered again. The discharge port at the bottom of the process tank 17 is connected to the concentrated liquid transfer pump 23 and the feed pump 22 through a pipeline.

The filtration accuracy of the ceramic membrane tube is 50nm.

The high-pressure reverse osmosis unit includes a sand filter 24 , an activated carbon filter 25 , a buffer tank 26 , a security filter 27 , a high-pressure reverse osmosis pump 28 , and a high-pressure reverse osmosis component 29 connected in sequence. It also includes a clean water tank 31 , a first cleaning water delivery pump 33 , a concentrated water tank 30 , and a second cleaning water delivery pump 32 . The clean water outlet of the high-pressure reverse osmosis component 29 is connected to the water inlet of the clean water tank 31, and the clean water tank 31 is discharged to the inlet of the high-pressure reverse osmosis component 29 through the first cleaning water pump 33, and the process water is concentrated by the high-pressure reverse osmosis component 29 again; the high-pressure reverse osmosis component 29 The concentrated water outlet is connected to the water inlet of the concentrated water tank 30, and the concentrated water tank 30 is discharged to the high-efficiency evaporation unit through the second cleaning water pump 321 for further processing. The pipeline between the activated carbon filter 25 and the buffer tank 26 is connected to the water inlet of the concentrated water tank 30 .

The circulating water sewage treatment and reuse system based on the ceramic membrane of the present invention realizes efficient treatment of the circulating water sewage by setting a pretreatment unit, an advanced oxidation unit, a ceramic membrane treatment unit and a high-pressure reverse osmosis unit.

The most obvious advantage of the system of the present invention is that it reduces the COD of wastewater indicators, and the double-alkali softening usually has no effect on reducing COD, and the double-alkali method produces a large amount of sludge due to the large amount of chemicals added. If this part of the sludge cannot be effectively reused, it will be The formation of new solid waste increases the difficulty of treatment, and during the treatment process of the dual-alkali method, the ultrafiltration unit often needs to be backwashed, but the flushing effect is not good. At the same time, the security filter element will often need to be replaced. Under normal operation , It needs to be replaced in half a month. For a 300MW unit, the security filter needs to be replaced every year, which wastes production time and labor costs. However, during the operation of the ceramic membrane-based circulating water and sewage treatment and reuse system of the present invention, the security filter does not have any obvious change in pressure difference, which greatly saves the operation and maintenance cost.

In the ceramic membrane-based circulating water and sewage treatment and reuse system of the present invention, the cost of the advanced oxidation unit is about 2.1 yuan/t. Due to the high stability of the catalyst, it usually only needs to be replaced once every 3-5 years. After recalculation, The cost of the advanced oxidation unit is 2.4 yuan/t. The cost of ceramic membrane treatment unit is usually higher than that of organic membrane treatment unit. The price of ceramic membrane is about 40% higher than that of ultrafiltration membrane with the same scale of treatment capacity, and there is not much difference in treatment operation cost. In the high-pressure reverse osmosis unit, although the softening method can reduce the content of calcium and magnesium ions, adding new sodium ions and chloride ions to the wastewater does not reduce the conductivity of the circulating water sewage concentrated water. Under normal circumstances, the operating pressure and power consumption of the two are similar, so the cost is not much different.

Table 1 Softening method+membrane treatment and the treatment and reuse system engineering cost comparison of circulating water sewage based on ceramic membrane of the present invention

engineering cost Dosing treatment (10,000) Ultrafiltration treatment (10,000) Reverse osmosis (10,000) Softening method + membrane treatment 132 117 245 Advanced oxidation + film treatment 112 197 242

Table 2 Softening method+membrane treatment and the treatment and recycling system operating cost comparison of circulating water sewage based on ceramic membrane of the present invention

Operating costs Dosing treatment (yuan/t) Ultrafiltration treatment (yuan/t) Reverse osmosis (yuan/t) Softening method + membrane treatment 3.4 4.5 4.5 Advanced oxidation + film treatment 2.1 4.3 4.6

By comparison, it can be seen that although the engineering cost of the softening method is lower than the cost of the ceramic membrane-based circulating water and sewage treatment and reuse system of the present invention, the softening method cannot solve the problem of frequent replacement of influent COD and security filter elements. Although the operating cost of the ceramic membrane-based circulating water sewage treatment and reuse system of the present invention is slightly lower than the softening method + membrane treatment, the advanced oxidation in the ceramic membrane-based circulating water sewage treatment and reuse system of the present invention The amount of sludge produced by the unit is small, which reduces the cost of solid waste treatment. Therefore, in terms of the concentration and reduction process of circulating water sewage membrane method, the advanced oxidation + ceramic membrane + reverse osmosis of the present invention is a more reasonable treatment process , that is, the ceramic membrane-based circulating water sewage treatment and reuse system of the present invention is a more reasonable treatment system.

Example 2

A method for treating and reusing circulating water and sewage, using the above ceramic membrane-based circulating water and sewage treatment and recycling system to treat circulating water and sewage.

The processing parameters of each unit of the circulating water sewage treatment and reuse system based on ceramic membranes are optimized:

The COD index that affects the operation stability of the membrane system, and because the suspended matter in the concentrated water of the circulating water blowdown is mainly calcium sulfate particles, which is relatively viscous, it is easy to cause fouling to the membrane system, that is, in the pretreatment process, it should be considered to reduce this Two types of pollution indicators. Reagents and equipment required: Catalyst TiO ₂ , in original sheet shape, with a thickness of 0.5 cm, a diameter of 1.5 cm, and a specific surface area of 55 m ² /g. The effect of using ozone alone to treat concentrated sewage from circulating water is not obvious. Catalyst + ozone is a process that can effectively treat concentrated sewage from circulating water. It can significantly reduce the concentration of circulating water without adjusting the initial index of concentrated sewage from circulating water The COD index of sewage concentrated water can obtain a COD removal rate of 19.2% in 1 hour of reaction, and a COD removal rate of 51.6% in 2 hours. On the one hand, ceramic catalysts are stable in performance, and the adsorbed calcium sulfate is easy to fall off , and the pore size is large, not easy to be blocked, so it has good stability.

Judging from the changes in water quality before and after the advanced oxidation unit treatment, in addition to the significant decrease in the COD index of the water body, some metal ions and acid radicals that are prone to precipitate have also decreased to a certain extent. This is because the oxidation process will not only reduce the COD index, At the same time, it will also destroy the original water body in the concentrated water of circulating water sewage, such as destroying the colloidal structure, so that some of the original supersaturated ions are in a destabilized state, and then separated from the water body.

(1) Preprocessing unit optimization

The advanced oxidation unit relies on the hydroxyl radical formed by the oxidant to oxidize the organic matter in the wastewater. Under alkaline conditions, the formation of hydroxyl radicals will be inhibited, and the initial pH is an important factor affecting the formation of hydroxyl radicals. By adjusting the pH of the circulating water sewage produced by the triple box, it was found that as the pH increased from 5.0 to 10.0, the COD of the circulating sewage concentrated water decreased from 650mg/L to 157-218mg/L. When the pH is 7.0, COD can be reduced to 151mg/L. Further increase the pH to 9.0-10.0, COD slowly increased to 198mg/L-222mg/L. This is because the addition of the catalyst will activate the conversion of ozone into hydroxyl radicals, which partially offsets the effect of pH on the generation of hydroxyl radicals. When the pH=9.0, the ammonia nitrogen in the circulating water blowdown concentrated water can be reduced from 316.2mg/L to 35.3mg/L, and the removal rate reaches 89.2%. And during the process of treatment, flocculent precipitation appeared in the wastewater, and after the sedimentation, the content of suspended solids continued to decrease from 4700mg/L to 1280mg/L. From the above analysis, it can be seen that when the pH=9, the removal rates of COD, ammonia nitrogen and suspended solids in the concentrated water of circulating water blowdown reached 69.6%, 90%, and 76%, respectively, and the pH of the effluent of the triple box was 9-10, which is suitable for the use of this technology Require.

(2) Advanced oxidation unit optimization

A. The effect of ozone introduction time on the reduction of COD, ammonia nitrogen and suspended solids in the concentrated water of circulating water sewage

Generally speaking, it is not advisable to use too high ozone concentration for ozone treatment. On the one hand, the ozone destruction device may have a problem of limited processing capacity. On the other hand, high-concentration ozone requires pure oxygen as a gas source, which increases the difficulty and requirements of on-site chemical management. . Prolonging the ozone penetration time is an effective way to increase the contact probability of pollutants and oxidants in wastewater, which can enhance the contact probability of pollutants in wastewater with ozone and the formation of hydroxyl radicals, which is conducive to reducing COD, ammonia nitrogen and suspended objects and other indicators.

With the continuous prolongation of the ozone injection time, the indicators of circulating water and sewage showed a downward trend. From 0.5h, COD and ammonia nitrogen decreased rapidly. When the time was 0.5h-2.5h, COD decreased from 601mg/L to 184mg/L, and ammonia nitrogen decreased from 275.8mg/L to 30.7mg/L. After 2.5 hours, the decline of wastewater indicators tended to be flat. After continuing to pass ozone for 2 hours, COD only decreased from 201mg/L to 158mg/L, and ammonia nitrogen decreased from 34.3mg/L to 28.2mg/L, indicating that the effect of continuous oxidation treatment is limited . This is because as the content of pollutants in wastewater continues to decrease, the effective contact probability of ozone and hydroxyl radicals with pollutants decreases, and some pollutants form more difficult-to-degrade substances after being oxidized, making it impossible to obtain Ideal processing effect.

From the above analysis, it can be seen that when the ozone injection time is 0.5h-2.5h, the removal rate of COD, ammonia nitrogen and suspended solids in the concentrated water of circulating water sewage is high and the cost is relatively low. Therefore, the ozone injection time is selected to be 0.5h-2.5 h can meet the requirements.

B. The effect of catalyst addition on the reduction of COD, ammonia nitrogen and suspended solids in circulating water sewage

The contact efficiency between ozone and the catalyst greatly affects the generation of hydroxyl radicals. Increasing the amount of catalyst used can provide a larger specific surface area for the gas-liquid two-phase contact, increase the contact probability between ozone and the catalyst, and increase the generation of hydroxyl radicals, thereby enhancing the reduction effect of circulating water sewage COD and other indicators.

With the increase of the amount of catalyst added, the COD, ammonia nitrogen, suspended solids and other indicators of circulating water sewage decreased, which proved that increasing the amount of catalyst added can increase the contact probability between ozone and catalyst and strengthen the formation of hydroxyl radicals. When the amount of catalyst added increased to 50g, COD decreased from 640mg/L to 197mg/L, and ammonia nitrogen decreased from 310.7mg/L to 25.7mg/L. When continuing to increase the amount of catalyst added to 100g, COD only decreased to 161mg/L, ammonia nitrogen only decreased to 29.1mg/L. At the same time, with the increase of the amount of catalyst added, in order to maintain the fluidized state of the reaction system, it is necessary to increase the amount of explosive gas, resulting in an increase in energy consumption. Considering comprehensively, the optimal amount of catalyst addition is 50g, that is, the ratio of the amount of catalyst to the concentration of circulating water blowdown is 1:60.

(3) Optimization of ultrafiltration treatment unit (ie, ceramic membrane treatment unit)

The main purpose of the pretreatment unit is to separate various impurities in the water to the greatest extent, reduce the processing burden of the subsequent membrane system treatment unit, and maintain the treatment efficiency and operation stability of the subsequent membrane treatment unit. The main pollutants affecting the membrane treatment system are suspended solids, scaling ions and organic matter. The source of suspended solids is mainly calcium sulfate, silicon salt, phosphate and other precipitates formed in the concentrated water of circulating water sewage. The suspended solids in the concentrated water of circulating water sewage are mostly amorphous substances with small particles and high dispersion degree. Due to the existence of a large amount of salt and colloid in the concentrated water of circulating water sewage, it is difficult to treat such substances. The key to treating suspended solids in the concentrated water of circulating water sewage is to use anti-pollution ultrafiltration treatment unit to avoid the function of the ultrafiltration unit being unable to recover due to the fouling of particles in the concentrated water of circulating water sewage. Therefore, the present invention treats the circulating water sewage concentrated water by selecting the anti-pollution ceramic membrane. The filtration accuracy of the ceramic membrane is 50nm. The operation stability and treatment efficiency of the same circulating water sewage concentrated water treated by the ceramic membrane are significantly improved. Under the same membrane area, the water volume of the ceramic membrane treated circulating water sewage concentrated water is significantly higher than that of the organic membrane. Improvement, the overall treatment efficiency is 16.7% higher, and in terms of recovery rate index, the ceramic membrane system can reach 86.7% on average, while the organic ultrafiltration membrane can only reach 67.7%, so in terms of ultrafiltration units, ceramic membrane filtration components It is an ultrafiltration unit that is very suitable for the treatment of circulating water sewage concentrated water.

(4) Optimization of high pressure reverse osmosis unit

Due to the high salt content of the circulating water sewage concentrated water, the last step in the concentration of the circulating water sewage concentrated water is desalination and concentration. On the one hand, it can achieve effective desalination and reduce the amount of waste water. Low can realize recycling and save water resources. The invention adopts the domestic anti-pollution high-pressure reverse osmosis membrane as the reverse osmosis unit for treating the concentrated sewage of circulating water.

The main equipment includes:

(1) Security filter: 5um security filter, the material is SS361L stainless steel, and the pp cotton filter element with a precision of 5um is used inside. When the pressure difference between the two sides of the security filter is greater than 0.1MPa, it should be replaced.

(2) RO membrane module: BW-8040-400LP is used as the system membrane element, and the ceramic membrane outlet water is used as the reverse osmosis inlet water, and the treatment process is one stage and one stage.

(3) The cleaning system includes a cleaning tank and related cleaning pipelines. The cleaning liquid is manually configured, and the pump is used to circulate the material and liquid. When the pressure difference of the membrane module increases by 15-20%, or the generated flow rate drops by 15%, the Stop the system for chemical cleaning.

The water recovery rate of the high-pressure reverse osmosis unit of the present invention is controlled between 60% and 70%, the desalination rate is controlled above 98%, and the dosing amount of the reverse osmosis scale inhibitor is 1.0ppm according to the usage requirements. For the circulating water sewage concentrated water treated by the ceramic membrane treatment unit, during the continuous operation of one month, the inlet pressure and transmembrane pressure difference of the high pressure reverse osmosis unit did not change significantly, and the transmembrane pressure difference was always maintained at 0.1bar And the water recovery rate can reach between 60-70%, there is no obvious change. Using reverse osmosis to treat the circulating water sewage concentrated water after the ceramic membrane treatment does not cause problems such as fouling of the membrane, and at the same time, the circulation Impurities such as suspended solids, salt and other impurities in the concentrated water of sewage sewage are separated in several concentrated units, which avoids the problem of waste water and waste residue generated in each step of the circulating water sewage concentrated water treatment method, which leads to a shorter maintenance cycle of the intermediate treatment unit Short problem, and the desalination rate is always maintained above 98%.

Example 3

A method for treating and reusing circulating water and sewage, using the above ceramic membrane-based circulating water and sewage treatment and recycling system to treat circulating water and sewage;

The catalytic oxidation tower is filled with the original sheet-shaped TiO ₂ catalyst with a thickness of 0.5cm, a diameter of 1.5cm, and a specific surface area of 55m ² /g; the ratio of the catalyst to the concentrated sewage of circulating water is 1:60; Ozone, the feeding time is 0.5h-2.5h; the transmembrane pressure difference of the high-pressure reverse osmosis treatment unit is always maintained at 0.1bar;

Send the water to be treated to the pretreatment unit, and adjust the pH to 9-10; the water from the pretreatment unit is sent to the advanced oxidation unit, and the COD, ammonia nitrogen and suspended solids in the water are removed in the advanced oxidation unit; the water from the advanced oxidation unit is sent to the ceramic membrane treatment unit , to filter the water body; the water from the ceramic membrane treatment unit is sent to the high-pressure reverse osmosis unit to desalinate and concentrate the water body.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A treatment and reuse system for circulating water and sewage based on ceramic membranes, characterized in that it comprises successively connected pretreatment units, advanced oxidation units, ceramic membrane treatment units and high-pressure reverse osmosis units; The pretreatment unit is used to adjust the pH of the water body to be treated and reduce suspended solids, including a mixing tank and a triple box connected in sequence; The advanced oxidation unit includes a catalytic oxidation tower, which is filled with a catalyst and connected to an ozone generator; The ceramic membrane processing unit includes a process tank and a ceramic membrane filter assembly connected in sequence; The high-pressure reverse osmosis unit includes a filter tank, a buffer tank, a security filter, a high-pressure reverse osmosis pump, and a high-pressure reverse osmosis component connected in sequence. 2. The treatment and reuse system of circulating water and sewage based on ceramic membranes as claimed in claim 1, wherein the pretreatment unit also includes a flocculant dosing pump and a flocculant tank, and the flocculant tank and flocculant The dosing pump is connected, and the flocculant dosing pump is connected to the flocculation box in the triple box, and the flocculant in the flocculant tank is transported to the flocculation box. 3. The treatment and reuse system of circulating water and sewage based on ceramic membranes as claimed in claim 1, wherein the pretreatment unit also includes a cyclone, a filter feeding box, and a sludge treatment device; The cyclone is connected with the sewage outlet of the settling tank in the triple box, and is used for solid-liquid separation of sludge impurities. The solid outlet is connected with the material inlet of the filter feeding box, and the liquid outlet is connected with the mixing tank; the filter feed The material outlet of the material box is connected with the material inlet of the sludge treatment device. 4. The treatment and reuse system of circulating water and sewage based on ceramic membrane as claimed in claim 3, wherein the sludge treatment device is a vacuum disc filter or a vacuum belt dehydrator, and its liquid outlet is connected to the mixing tank connected. 5. The treatment and reuse system of circulating water and sewage based on ceramic membranes as claimed in claim 1, wherein the advanced oxidation unit also includes a hydrogen peroxide dosing device, a dosing pump, a pipeline mixer, a cyclone, circulation pump; The hydrogen peroxide dosing device is connected to the pipeline mixer through a pipeline, and the pipeline between the two is provided with a dosing pump; the pipeline mixing device is connected to the material inlet of the catalytic oxidation tower for mixing the water body to be treated with the hydrogen peroxide ; The cyclone is connected with the gas inlet of the catalytic oxidation tower, and is used to deliver air to the catalytic oxidation tower; the part between the top of the catalyst of the catalytic oxidation tower and the discharge port is provided with a circulation pipe, and the circulation pipe is connected with the circulation pump. It is used to retransmit the catalytically oxidized liquid in the catalytic oxidation tower to the bottom of the catalytic oxidation tower through the circulation pump, so that it can be catalytically oxidized. 6. The treatment and reuse system of circulating water and sewage based on ceramic membranes as claimed in claim 1, wherein the advanced oxidation unit also includes a booster pump, and the catalytic oxidation tower material outlet is connected to the booster pump through a pipeline , used to pump the water body to the ceramic membrane treatment unit. 7. The treatment and reuse system of circulating water and wastewater based on ceramic membranes as claimed in claim 1, wherein said ceramic membrane treatment unit also includes a plate heat exchanger, a cleaning tank, a feed pump, and a main circulation pump , and concentrated liquid transfer pump; The ceramic membrane filter assembly includes multiple sets of parallel ceramic membrane tubes and water supply tanks connected to the ceramic membrane tubes; the main circulation pump connects different water supply tanks through pipelines; The pipeline between the process tank and the ceramic membrane filter module is provided with a plate heat exchanger; the outlet pipe of the ceramic membrane filter module is provided with a branch connected to the cleaning tank, and the water from the cleaning tank is sent to the dope transfer pump or through the feeder The water is pumped out to the ceramic membrane filter assembly, so that the water body is filtered again. 8. The treatment and reuse system of circulating water and sewage based on ceramic membranes as claimed in claim 1, wherein the filtration accuracy of said ceramic membrane tubes is 50nm. 9. The treatment and reuse system of circulating water and sewage based on ceramic membrane as claimed in claim 1, wherein the filter of the high-pressure reverse osmosis unit is a sand filter and an activated carbon filter connected in sequence; The high-pressure reverse osmosis unit also includes a clean water tank, a first cleaning water delivery pump, a concentrated water tank, and a second cleaning water delivery pump; the clean water outlet of the high-pressure reverse osmosis module is connected to the water inlet of the clean water tank, and the clean water tank is passed through the first cleaning water delivery pump The water is discharged to the inlet of the high-pressure reverse osmosis module; the concentrated water outlet of the high-pressure reverse osmosis module is connected to the water inlet of the concentrated water tank, and the concentrated water tank is discharged to the high-efficiency evaporation unit through the second cleaning water pump for further processing. 10. A method for treating and reusing circulating water sewage, characterized in that, the circulating water sewage treatment and recycling system based on ceramic membranes according to any one of claims 1-9 is used to process circulating water sewage; The catalytic oxidation tower is filled with the original sheet-shaped TiO ₂ catalyst with a thickness of 0.5cm, a diameter of 1.5cm, and a specific surface area of 55m ² /g; the ratio of the catalyst to the concentrated sewage of circulating water is 1:60; Ozone, the feeding time is 0.5h-2.5h; the transmembrane pressure difference of the high-pressure reverse osmosis treatment unit is always maintained at 0.1bar; Send the water to be treated to the pretreatment unit, and adjust the pH to 9-10; the water from the pretreatment unit is sent to the advanced oxidation unit, and the COD, ammonia nitrogen and suspended solids in the water are removed in the advanced oxidation unit; the water from the advanced oxidation unit is sent to the ceramic membrane treatment unit , to filter the water body; the water from the ceramic membrane treatment unit is sent to the high-pressure reverse osmosis unit to desalinate and concentrate the water body.

Images