CN104529018A - Electrocoagulation in printing and dyeing wastewater treatment and reuse process - Google Patents

Abstract

The invention relates to the field of sewage treatment technology, and in particular to the electro-flocculation in the treatment and reuse of printing and dyeing wastewater, which integrates electrochemical technology and traditional chemical precipitation technology, realizes deep removal of ions at the same time under the action of direct current electric field, and the plate reacts with the current continuously, and electron migration occurs between the cathode and anode of the electrolytic bed, causing electrochemical reaction, and at the same time, water produces oxygen discharge at the anode to produce oxidation reaction, oxidizes inorganic and organic matter in water, and cathode ions are electrified to form hydrogen. This primary ecological hydrogen has the strongest reducing ability. Therefore, it can effectively remove dissolved salts, colloids, microorganisms, and organic matter in water, produce coagulation precipitation of iron ions and metal ions in water, and no additional agent is needed to be added, and flocculants are produced by themselves.

Description

Electrocoagulation in printing and dyeing wastewater treatment and reuse process

Technical field:

The invention relates to the technical field of sewage treatment, in particular to electrocoagulation in the treatment and recycling of printing and dyeing wastewater.

Background technique:

Printing and dyeing wastewater is wastewater produced by textile printing and dyeing factories in the production and processing of cotton, linen, chemical fibers and blended products. The main characteristics of printing and dyeing wastewater are large water volume, high chroma, high CODCr, strong alkalinity and large changes in water quality. 100-200 tons of water is needed for printing and dyeing 1 ton of textiles, of which 80% to 90% become waste water. Wastewater contains dyes, pulp, chemical additives, oils, acids and bases, fibers and entrained impurities, inorganic salts and minerals, etc. Belongs to difficult to treat industrial wastewater. In addition, the printing and dyeing industry is a large discharge of industrial wastewater (accounting for about 80% of the total discharge). Therefore, it is particularly important to find a process for effectively treating printing and dyeing wastewater!

Traditional treatment methods and limitations. The main methods used in traditional industries to treat printing and dyeing wastewater include physical and chemical methods, biochemical methods, chemical methods, and process-combined treatment methods (such as diversion aerated biological filters, etc.). However, the traditional treatment process cannot grasp the characteristics of printing and dyeing wastewater well to make a breakthrough. The traditional process still has many limitations in the treatment of printing and dyeing wastewater: 1. The process is cumbersome and occupies a large area; 2. The treatment effect is single, and there is no systematic and comprehensive treatment; Biochemical treatment brings instability and processing pressure; 4. The debugging cycle is long; 5. Relying on human operation, it is prone to hidden dangers such as operational errors leading to system paralysis; 6. Because traditional chemical treatment requires a large amount of chemical drugs, resulting in The salinity of the water body increases, which increases the load on the recycling system, makes the system clean frequently, cannot normally meet the recycling requirements, and has high operating costs.

Invention content:

The purpose of the present invention is to provide electrocoagulation in printing and dyeing wastewater treatment and recycling process in view of the deficiencies of the prior art. Electrochemical reaction converts electrical energy into chemical energy. A single electrocoagulation device can perform oxidation-reduction reactions on organic or inorganic substances in wastewater to generate stable and easy-to-separate substances. Separating the pollutants from the water body to achieve the effect of purifying the water body.

In order to achieve the above object, the present invention adopts the following technical scheme, and the process steps of the processing method are as follows:

Electrocoagulation is used in the treatment and reuse of printing and dyeing wastewater. The process steps of the treatment method are as follows:

(1) Combining electrochemical technology with traditional chemical precipitation technology, under the action of a direct current electric field, the deep removal of ions is realized simultaneously, and the continuous reaction of the plate with the current, and the electron migration between the cathode and anode of the electrolytic bed , causing an electrochemical reaction.

(2) At the same time, the water generates an oxygen discharge at the anode to generate an oxidation reaction, which oxidizes the inorganic and organic substances in the water.

(3) Cathode ions are electrified to form nascent hydrogen, which has the strongest reducing ability to remove chroma in water and reduce hexavalent chromium.

(4) Since the iron plate produces iron ions and metal ions in the water for coagulation and precipitation during electrolysis, no additional chemicals are needed, and the flocculant is self-produced.

(5) Enter the ultrafiltration and reverse osmosis devices for deep removal and reuse. In order to prevent the ultrafiltration membrane from being polluted by microorganisms, add an appropriate amount of oxidant (generally 10-20ppm) to kill algae and bacteria during ultrafiltration backwashing; ultrafiltration The effluent enters the reverse osmosis for reuse, in order to prevent the reverse osmosis membrane from being oxidized by the excessive addition of oxidant for ultrafiltration, and a reduction (sodium bisulfite) is installed at the reverse osmosis water inlet. At the same time, the system is equipped with a chemical cleaning device. When the system is seriously polluted , the cleaning device can be started for chemical cleaning to meet the normal operation of the system.

The ultrafiltration membrane is a membrane element made of PAN material. the

The ultrafiltration device is a hollow fiber ultrafiltration membrane, and the outer diameter of the hollow fiber is the inside diameter of The hollow fiber tube wall is covered with micropores.

The reverse osmosis cleaning system consists of a stainless steel cleaning pump, a cleaning medicine box, a 5 μm filter and piping.

The dosage concentration of the sodium sulfite is usually 10%, and the dosage is 20-30 mg/L.

The beneficial effects of the present invention are as follows: (1) Combining the electrochemical technology with the traditional chemical precipitation technology, under the action of a direct current electric field, the deep removal of ions is simultaneously realized, and the plate continuously reacts with the current, and the cathode and anode of the electrolytic bed Electron migration occurs between the two, causing an electrochemical reaction.

(2) At the same time, the water generates an oxygen discharge at the anode to generate an oxidation reaction, which oxidizes the inorganic and organic substances in the water.

(3) Cathode ions are electrified to form nascent hydrogen, which has the strongest reducing ability to remove chroma in water and reduce hexavalent chromium.

(4) Since the iron plate produces iron ions and metal ions in the water for coagulation and precipitation during electrolysis, no additional chemicals are needed, and the flocculant is self-produced.

(5) Enter the ultrafiltration and reverse osmosis devices for deep removal and reuse. In order to prevent the ultrafiltration membrane from being polluted by microorganisms, add an appropriate amount of oxidant (generally 10-20ppm) to kill algae and bacteria during ultrafiltration backwashing; ultrafiltration The effluent enters the reverse osmosis for reuse, in order to prevent the reverse osmosis membrane from being oxidized by the excessive addition of oxidant for ultrafiltration, and a reduction (sodium bisulfite) is installed at the reverse osmosis water inlet. At the same time, the system is equipped with a chemical cleaning device. When the system is seriously polluted When the time comes, the cleaning device can be started for chemical cleaning to meet the normal operation of the system; the effect of treating printing and dyeing wastewater by high-voltage pulse electrocoagulation is remarkable. Short commissioning period, low labor and operating costs, high stability, and greatly reduce the pressure of later biochemistry. After electrocoagulation treatment, the COD removal rate reaches 50% to 70%, the color degradation rate reaches 98.5%, and the SS removal rate reaches 90%. , The acidity and alkalinity of the effluent is weakly alkaline, which further improves the wastewater treatment capacity and reduces energy consumption, effectively and practically solves the difficulties and problems.

Detailed ways:

The present invention adopts the following technical scheme, and the process steps of the treatment method are as follows: (1), the electrochemical technology and the traditional chemical precipitation technology are combined, and the deep removal of ions is simultaneously realized under the action of a direct current electric field, and the plate continuously reacts with the current , Electron migration occurs between the cathode and anode of the electrolytic bed, causing an electrochemical reaction.

(2) At the same time, the water generates an oxygen discharge at the anode to generate an oxidation reaction, which oxidizes the inorganic and organic substances in the water.

(3) Cathode ions are electrified to form nascent hydrogen, which has the strongest reducing ability to remove chroma in water and reduce hexavalent chromium.

(4) Since the iron plate produces iron ions and metal ions in the water for coagulation and precipitation during electrolysis, no additional chemicals are needed, and the flocculant is self-produced.

(5) Enter the ultrafiltration and reverse osmosis devices for deep removal and reuse. In order to prevent the ultrafiltration membrane from being polluted by microorganisms, add an appropriate amount of oxidant (generally 10-20ppm) to kill algae and bacteria during ultrafiltration backwashing; ultrafiltration The effluent enters the reverse osmosis for reuse, in order to prevent the reverse osmosis membrane from being oxidized by the excessive addition of oxidant for ultrafiltration, and a reduction (sodium bisulfite) is installed at the reverse osmosis water inlet. At the same time, the system is equipped with a chemical cleaning device. When the system is seriously polluted , the cleaning device can be started for chemical cleaning to meet the normal operation of the system.

The ultrafiltration membrane is a membrane element made of PAN material. the

The ultrafiltration device is a hollow fiber ultrafiltration membrane, and the outer diameter of the hollow fiber is the inside diameter of The hollow fiber tube wall is covered with micropores.

The reverse osmosis cleaning system consists of a stainless steel cleaning pump, a cleaning medicine box, a 5 μm filter and piping.

The dosage concentration of the sodium sulfite is usually 10%, and the dosage is 20-30 mg/L.

Said adding an appropriate amount of oxidizing agent at a concentration of 10% (generally 10-20ppm) during ultrafiltration backwashing.

Compared with the traditional electrolysis method, the current efficiency of the high-voltage pulse electrocoagulation method is 20%-30% higher; the electrolysis time is shortened by 30%-40%; the power saving reaches 30%-40%; the amount of sludge is less; the removal rate of heavy metals can reach 96% -99%.

The effect of treating printing and dyeing wastewater by high-voltage pulse electrocoagulation is remarkable. Compared with the treatment methods in traditional industries, high-voltage pulse electrocoagulation has the advantages of small treatment area, unified treatment, short commissioning cycle, low labor and operating costs, high stability and greatly Reduces biochemical stress in later stages. After electrocoagulation treatment, the COD removal rate reaches 50% to 70%, the color degradation rate reaches 98.5%, the SS removal rate reaches 90%, and the acidity and alkalinity of the effluent is weakly alkaline. It effectively and practically solves difficulties and problems for enterprises to further improve wastewater treatment capacity and reduce energy consumption.

The basic principle is that through the action of voltage and current, the organic matter and chromogenic groups in the water, as well as the complex complexation chain or chelation chain, are broken down into small molecules and ions, and the iron flocculant that dissolves spontaneously on the plate And under the action of electric field traction, floatation or sedimentation removal. At the same time, a certain amount of modified diatomite is added to the water treatment, with the help of diatomite's strong adsorption and flocculation ability, fine and ultrafine substances can be adsorbed to its surface, and the treatment effect is better.

Electrocoagulation has the characteristics of strong oxidation - self-produced oxidant, strong reduction - self-produced reducing agent, flocculation - self-produced flocculant, air flotation - self-produced air flotation ultra-fine bubbles, and seven functions of sterilization, decolorization and deodorization in one machine . It is particularly strong in the treatment and reuse of fine dust wastewater, high chroma wastewater, refractory wastewater, toxic and harmful wastewater, and industrial wastewater containing heavy metal ions.

After the electrocoagulation treatment, combined with the membrane recovery system, the water quality of the recycled water and the life of the reverse osmosis system can be greatly improved.

Membrane recycling technology:

At present, in the field of wastewater reuse, membrane filtration technology is mainly used. Its characteristics are: mature technology, stable operation, good effluent quality, fully automatic operation, beautiful appearance and small footprint. During operation, the backwashing and water production are automatically controlled by PLC. In addition, according to the operating conditions, chemical cleaning and maintenance can be performed once every 3-6 months. At present, membrane manufacturers of major brands have developed various anti-fouling membrane modules suitable for wastewater reuse.

Membrane separation technology can generally be divided into four categories: microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO), and their filtration accuracy is getting higher and higher in the above order. Users can choose a suitable membrane type or a combination of several layers according to the water quality requirements.

1) Microfiltration can intercept particles between 0.1 and 1 micron. The microfiltration membrane allows macromolecular organic matter and dissolved solids (inorganic salts) to pass through, but can block suspended solids, bacteria, some viruses and large-scale colloids. Permeation, the operating pressure difference (effective driving force) on both sides of the microfiltration membrane is generally 0.7bar.

2) Ultrafiltration can intercept particles and impurities between 0.002 and 0.1 microns. The ultrafiltration membrane allows small molecular substances and dissolved solids (inorganic salts) to pass through, but will effectively block colloids, proteins, microorganisms and macromolecular organic substances. The cut-off molecular weight used to characterize the ultrafiltration membrane is generally between 1,000 and 100,000, and the operating pressure difference on both sides of the ultrafiltration membrane is generally 1 to 7 bar.

3) Nanofiltration is a special and promising type of separation membrane. It is named after the size of the intercepted substance is about 1 nanometer (0.001 micron). The operating range of nanofiltration is between ultrafiltration and reverse osmosis. Between them, the molecular weight of its intercepted organic matter is about 200-400, and the ability to intercept soluble salts is between 20-98%. The removal rate of monovalent anion salt solutions is lower than that of high-valent anion salt solutions, such as sodium chloride and chlorine. The removal rate of calcium chloride is 20-80%, while the removal rate of magnesium sulfate and sodium sulfate is 90-98%. Nanofiltration membranes are generally used to remove organic matter and chroma in surface water, remove hardness and radioactive radium in well water, partially remove soluble salts, concentrate food and separate useful substances in medicines, etc. The operating pressure difference on both sides of the nanofiltration membrane Generally 3.5 ~ 16bar.

4) Reverse osmosis is the most precise membrane liquid separation technology. It can block all soluble salts and organic matter with a molecular weight greater than 100, but allows water molecules to pass through. The desalination rate of cellulose acetate reverse osmosis membranes can generally be greater than 95%. The desalination rate of the osmotic composite membrane is generally greater than 98%. They are widely used in desalination of seawater and brackish water, preparation of boiler feed water, industrial pure water and electronic grade ultrapure water, production of drinking pure water, wastewater treatment and special separation, etc. The use of reverse osmosis before ion exchange can greatly reduce Operating costs and wastewater discharge. The operating pressure difference on both sides of the reverse osmosis membrane is generally greater than 5bar when the feedwater is brackish water, and generally lower than 84bar when the feedwater is seawater.

In the membrane filtration system, the membrane is a key component, and the key to prolonging the life of the membrane and maintaining high flux is pretreatment. Effective pretreatment can reduce the load on the reverse osmosis membrane, improve stability and reliability, prolong the chemical washing cycle, and reduce the consumption of backwashing agents. Therefore, strict water inlet requirements are required when using membrane filtration.

1. Process: electrocoagulation + ultrafiltration + reverse osmosis;

2. The main equipment adopts ultrafiltration membrane and selects PAN material membrane element;

3. The design considers a 20% margin to adjust the impact load of water quality and water quantity.

4. System water balance: Under normal circumstances, the design recovery rate of ultrafiltration is 90-95%, and the design recovery rate of reverse osmosis is 60-65%.

6. System drainage and mud discharge:

The electrocoagulation device regularly discharges sludge, and the sludge returns to the raw water adjustment tank.

Manganese sand filter, multi-media filter backwash water discharge: backwash water: about 3m3/time for each filter, discharged once a day, and discharged to the front-end waste water pool for treatment.

Ultrafiltration concentrated water discharge: about 10%, continuous discharge, discharged to the front-end comprehensive wastewater pool.

Reverse osmosis concentrated water discharge: about 40%, continuous discharge, discharged to the concentrated water tank, and discharged after the ion exchanger removes heavy metal ions and adds oxidant to meet the standard; ion exchanger regeneration discharge wastewater enters the comprehensive wastewater pool.

Sludge treatment: discharged into the filter press system, and the water from the filter press is returned to the front-end wastewater tank for treatment. Sludge is transported and processed by qualified manufacturers.

7. Control system:

The reuse water pretreatment part adopts manual and automatic control, and the electrocoagulation host, ultrafiltration and reverse osmosis systems adopt PLC automatic control.

Electrocoagulation + flocculation sedimentation device

The working principle of electrocoagulation is to add a certain voltage to the water with a distance of 1cm-2cm to break and decompose various organic substances in the water, break the macromolecules into small molecules, and then participate in the electron flow movement in the water to obtain electrons or lose them. The electrons will eventually co-precipitate with the iron or aluminum salts precipitated on the iron or aluminum plates, while the heavy metal ions in the water will first break their complex complexation chains or chelation in water under a certain voltage and current. Then participate in the replacement reaction of gaining electrons or losing electrons (mainly with Fe and Al ions in water) and eventually partly become fine molecular particle state precipitation or still in the form of hydroxide precipitation of metal ions and Fe, Al hydrogen Co-precipitation of oxides. The reaction is a complex physical and electrochemical process, and theoretically the consumed electric energy can handle any equivalent of COD, molecular energy conversion, etc.

Electrocoagulation has the seven functions of strong oxidation - self-produced oxidant; strong reduction - self-produced reducing agent; flocculation - self-produced flocculant;

Electrocoagulation only needs one-tenth of the power consumption of electrolysis, electrochemical, eddy current and magnetized fluid effects, adjustable plate material (six types), plate spacing, voltage intensity, current density, PH value, conductivity, etc. Optimum processing performance. High decontamination rate, low initial investment cost, low operating cost, simple maintenance, wide range of sewage treatment, and small amount of sludge generated.

Factors affecting electrolysis efficiency:

A. plate material

The type of plate material has a great influence on the wastewater treatment effect. If it is not selected properly, it will increase the power consumption. Therefore, the actual operation should be selected according to the characteristics of the wastewater. According to experiments, the principle of electrocoagulation and flotation is mainly used in the treatment of textile and printing and dyeing wastewater. Soluble aluminum or iron plates should be selected as anodes, and iron plates should be used as cathodes; cyanide-containing wastewater should use graphite as anodes and iron plates as cathodes; For chromium wastewater, it is more appropriate to use iron plates as the anode and cathode. As for food waste water, there is no relevant performance data.

B. Plate spacing

The size of the plate spacing directly affects the power consumption and the residence time of wastewater in the electrolyzer. Generally speaking, the larger the spacing, the greater the wastewater residence time, voltage and power consumption will increase, and the treatment effect will also be affected; the smaller the spacing, the lower the power consumption and the shorter the wastewater residence time, but the number of electrode groups required will increase, the initial set-up cost is high, and installation and maintenance management are more difficult.

C. Current density

The anode current density refers to the current passing through the unit anode area. The size of the anode current density is related to the concentration of pollutants in the wastewater. When the wastewater concentration is constant, the higher the current density, the higher the voltage, the faster the reaction speed, the shorter the wastewater residence time, but the higher the power consumption and the shorter the plate life. On the contrary, the current density decreases, the plate area increases, and the initial setup fee increases. Therefore, the appropriate current density should be selected according to the water quality requirements.

D. to stir

Stirring can accelerate the diffusion of ions in wastewater, accelerate the reaction rate, and stabilize the quality of wastewater, thereby improving the treatment effect.

E.pH value

The electrocoagulation process is mainly used in wastewater treatment, so the pH value of wastewater needs to be controlled between 5 and 8. If the pH value is too high, the anode plate will be passivated, preventing the dissolution of the metal electrode, making electrocoagulation ineffective, and affecting the treatment. Effect.

F. Electrolyzer residence time

The length of the residence time directly affects the treatment effect and the volume of the electrolytic cell. The residence time of the electrolytic cell is related to the distance between the plates and the current density. In practical application, it must be determined after the feasibility test is carried out according to the characteristics of the wastewater quality.

G. Conductivity

The conductivity of wastewater directly affects the effect of electrocoagulation. If the conductivity of the wastewater to be treated is too high, it is easy to cause discharge between the cathode and anode plates in the electrolytic cell. The current passes quickly between the two plates, failing to produce electrocoagulation reaction on the pollutants in the wastewater, and the treatment effect will be greatly reduced. Therefore, the lower the conductivity of wastewater, the higher the effect of electrocoagulation treatment. Generally, it is better below 10000us/cm.

Electrocoagulation removal effect and application range:

A. Grease: animal, vegetable, mineral oil, hydration, emulsification, mixing, soluble oil or fat can be processed in form, and the removal rate can reach more than 99%.

B.SS: Including suspended and colloidal SS, such as wafer grinding chip wastewater in the IT industry and ultra-fine suspended solids in graphite factories, which can remove more than 99%.

C.BOD: It can be used as pretreatment of wastewater with high BOD concentration (strong oxidation bond breaking) to facilitate subsequent treatment. Medium and low concentration wastewater can be removed by 50%-60%.

D. COD: high-concentration COD wastewater, electrical neutrality is not easy to carry out physical and chemical treatment, it can be coagulated to remove or decompose into biodegradable small molecules due to strong oxidation breaking chemical bonds and destroying electrical neutrality for pretreatment. For low-to-medium-concentration waste water, the recycling standard can usually be reached after one treatment (a small test is required to confirm).

E.TN, TP: The removal of nutrients in surface water and river water is very effective, removing more than 85%

F. Heavy metals: removed by forming hydroxide plume. It has excellent low-cost processing benefits for CN- and Cr+6.

G. Bacteria, viruses, and cysts: all are killed by strong oxidation, and the removal rate is more than 99.9%.

H. Pigment removal: The color removal rate of printing and dyeing, dyeing and weaving industry wastewater is 98%, with superior special effects. The main principle is to destroy the functional groups of chromophores through strong oxidation and strong reduction.

I. Wastewater reuse, groundwater purification, surface water purification, cooling water purification,

J. Radioactive isotope removal; reverse osmosis RO, UF, nanofiltration, photocatalytic pretreatment.

Electrocoagulation equipment mainly includes: electrocoagulation machine, rectifier power supply, and dosing device. It is used together with an inclined tube reaction precipitator to effectively remove organic chromophores, colloidal substances and suspended pollutants in the printing and dyeing wastewater. The precipitator adopts an inclined tube for sedimentation, and the effluent of the electrocoagulation machine flows into the precipitator by itself.

J. Manganese sand filter

The reclaimed water treated by electrocoagulation equipment contains more Fe2+. After aeration and pH adjustment, most of the low-priced iron ions can be removed. However, due to the short reaction time, there are still residues in the effluent, which will affect the operation of subsequent membrane equipment. , need to be further removed. The manganese sand filter is filled with high-quality manganese sand and quartz sand filter materials, which can effectively remove iron and manganese ions in the water, and ensure that the produced water meets the water inlet requirements of the RO membrane.

The working principle of the manganese sand filter is to use the oxidation method to oxidize low-priced iron ions and low-priced manganese ions into high-priced iron ions and high-priced manganese ions, and then remove them by adsorption and filtration to reduce the iron and manganese content in the water. The filter material is refined manganese sand. After passing through the iron and manganese removal filter, it can ensure that the effluent Fe≤0.3mg/L. The equipment is controlled by a pneumatic butterfly valve.

Manganese sand iron removal principle: This equipment adopts the iron removal principle of aeration oxidation, manganese sand catalysis, adsorption, and filtration. The aeration device is used to dissolve the oxygen in the air into water, and then oxidize Fe2+ in water into Fe3+ insoluble in water. , combined with the catalysis, adsorption and filtration of natural manganese sand to remove iron ions in water.

The iron oxidation reaction formula is as follows:

Iron oxidation: Air: 4Fe2++3O2+6H2O＝4Fe(OH)3

Manganese sand: MnO.Mn ₂ O ₇ +4Fe ²⁺ +2O ₂ +6H ₂ O＝3MnO ₂ +4Fe(OH) ₃ ;

Under normal circumstances, the design operating velocity is about 8m/h-10m/h.

Under normal circumstances, the backwash cycle of a single filter is ≥24h.

Multimedia filter

The multi-media filter uses quartz sand and anthracite as the filter material to filter and remove particles and suspended solids in raw water. The upper layer is anthracite filter material with larger particles, and the lower layer is fine quartz sand particles. The filter materials in the filter are arranged from top to bottom, from small to large. When water flows through the filter layer from above, part of the solid suspended matter in the water enters the tiny pores formed by the upper filter material, and is trapped by the surface layer of the filter material due to adsorption and mechanical retention. At the same time, these intercepted suspended substances overlap and bridge, as if a thin film is formed on the surface of the filter layer, which continues to filter the suspended substances in the water, which is the so-called membrane filtration of the surface layer of the filter material. This filtering effect is not only on the surface of the filter layer, but also has this interception effect when water enters the middle filter layer, which is called osmotic filtration. In addition, because the filter materials are closely arranged with each other, when the suspended particles in the water flow through the tortuous channels in the filter material layer, they have more opportunities and time to collide and contact with the surface of the filter material, and the water The fine particles of impurities are intercepted, so that the water is further clarified and purified, and the turbidity of the water is reduced. Therefore, this filtration method provides good water intake conditions for the operation of subsequent equipment.

The differential pressure across the filter will increase over time until it fails. At this time, it is necessary to use reverse water flow to backwash the filter material, so that the filler in the filter is suspended and loose, so that the intercepted matter adhering to the surface of the filler is peeled off and taken away by the water flow, and the filtering function is restored. There are two backwashing methods: independent water backwashing and air-water backwashing. : Water backwash strength alone 10-15L/(m2 s), expansion rate: 50%; air-water backwash: air intake intensity 18-25L/(m2 s), blowing for 3 minutes, backwash expansion rate 10-15%, water backwash strength: 5-8L/(m2·s), expansion rate: 15-25%

The multi-media filter has no special requirements on the condition of the raw water, and can adapt to various raw water with different water quality or pollution conditions. Quartz sand filter has the characteristics of low investment, low cost operation, stable operation and high efficiency.

The characteristics of the multimedia filter:

Due to the unique design of uniform water distribution and loading of filter material, the filtration can achieve the maximum effect, the capacity of dirt holding is large, and the SDI value of the effluent is greatly reduced.

It can effectively remove colloids and suspended solids that are very sensitive to the impact of the RO system.

The backwashing device is designed with compressed air scrubbing technology, which can enhance the backwashing effect. Make the recoil process achieve strong ability, low water consumption and short time.

Under normal circumstances, the design operating velocity is about 8m/h-12m/h.

Under normal circumstances, the backwash cycle of a single filter is ≥24h.

Under normal circumstances, the filter material is replaced once a year.

bag filter

Bag filter can further remove the particle suspension in the filter. At the same time, it can effectively prevent sand particles from entering the subsequent system and damaging the water pump and diaphragm. The filter bag is selected with a precision of 50 μm to meet the requirements of ultrafiltration water inflow. The bag filter has the characteristics of high filtration precision, large dirt holding capacity, and easy replacement.

Ultrafiltration device

The main function is to remove impurities, suspended sludge and inhibit the growth of organic matter to avoid clogging and pollution, thereby prolonging the service life of subsequent equipment and reducing operating costs.

Ultrafiltration is a screening process related to the pore size of the membrane. The pressure difference on both sides of the membrane is used as the driving force, and the ultrafiltration membrane is used as the filter medium. Under a certain pressure, when the raw liquid flows through the surface of the membrane, the ultrafiltration The many tiny micropores densely covered on the surface of the membrane only allow water and small molecular substances to pass through to become the permeate, while the substances in the raw solution whose volume is larger than the micropore diameter of the membrane surface are trapped on the liquid inlet side of the membrane and become concentrated liquid, thus achieving The purpose of purification, separation and concentration of the original solution. The microporous screening on the surface of the ultrafiltration membrane can trap particles and impurities with a diameter between 0.002-0.1 μm, and can effectively remove colloids, silicon, proteins, microorganisms and macromolecular organic substances in water.

Hollow fiber ultrafiltration membrane is the most mature and advanced form of ultrafiltration technology. The hollow fiber tube wall is covered with micropores, and the pore size is expressed by the molecular weight that can intercept substances, and the molecular weight interception can reach several thousand to hundreds of thousands.

A hollow fiber ultrafiltration membrane module is mainly composed of hundreds to thousands of tiny hollow fiber filaments and a membrane shell. There are many materials that can be used to make ultrafiltration membranes, including polyvinylidene fluoride (PVDF), polyethersulfone (PES), polypropylene (PP), polyethylene (PE), polysulfone (PS), polyacrylonitrile (PAN) ), polyvinyl chloride (PVC), etc. In the late 1990s, polyethersulfone materials were commercially applied; and in the late 1990s, polyvinylidene fluoride ultrafiltration membranes with better performance began to be widely used in the water treatment industry. Therefore, polyethersulfone and polyvinylidene fluoride have become the most widely used ultrafiltration membrane materials. PAN ultrafiltration membrane has good hydrophilicity, excellent anti-oxidation and anti-fatigue strength. It is anti-pollution and resistant to cleaning, which greatly prolongs the service life of the membrane filament. The end of the ultrafiltration membrane module is encapsulated by epoxy resin casting.

The hollow fiber ultrafiltration membrane is divided into two types: internal pressure type and external pressure type according to the water inlet method: internal pressure type: the raw liquid first enters the hollow fiber, driven by the pressure difference, and penetrates the hollow fiber from the inside to the outside in the radial direction to become The permeated liquid and the concentrated liquid stay inside the hollow fiber and flow out from the other end. The role of the epoxy resin end seal is to seal the gap between the membranes at the end of the hollow fiber membrane, so that the raw liquid and the permeable Liquid separation prevents the raw liquid from directly infiltrating into the permeate without passing through the membrane filter.

The ultrafiltration process is simple, there are few supporting devices, the operation is simple, and the maintenance cost is low. The ultrafiltration membrane is resistant to chemical corrosion, has a wide range of pH adaptability, has the largest membrane area per unit volume of the ultrafiltration device, the lowest investment cost, and is easy to clean.

If the water quality of the ultrafiltration is good (turbidity is less than 5NTU), in order to improve the recovery rate, the operation mode of dead-end filtration can be adopted, and the recovery rate can reach more than 95%; if the turbidity of the influent water is greater than 5NTU, in order to reduce the membrane surface For pollution, it is recommended to adopt the operation mode of cross-flow filtration, and the cross-flow is about 10%-30%. The system adopts the cross-flow filtration method, and 10% of the cross-flow flow is returned to the sewage station as concentrated water.

In the ultrafiltration system, sodium hypochlorite is added to the influent or backwash water to prevent microorganisms from multiplying in the ultrafiltration membrane. The concentration of sodium hypochlorite is 10%, and the concentration is 10-20ppm when backwashing. Sodium hypochlorite storage time is generally a week to half a month is appropriate.

The ultrafiltration device is mainly composed of an ultrafiltration host, a backwash pump, a sodium hypochlorite dosing device, a chemical cleaning device, and an automatic control system. Set backwashing time and interval according to time or pressure, automatic operation and backwashing. The chemical cleaning device is composed of a cleaning water tank, a cleaning circulation pump, a 5μm security filter, and related instruments. Chemical cleaning is performed every 3-6 months with manual control.

RO recovery host (concentration and separation function)

The main function of the RO membrane unit is to concentrate and separate harmful substances in the water, such as TDS, COD, Cu2+ plasma, and its removal rate can reach more than 99%; the quality of the effluent water can reach the water quality of tap water, or even better than that of tap water.

RO [Reverse Osmosis] reverse osmosis technology is a membrane separation and filtration technology powered by pressure difference. Its pore size is as small as nanometers (1 nanometer = 10-9 meters). Under a certain pressure, H2O molecules can pass through the RO membrane, while Impurities such as inorganic salts, heavy metal ions, organic matter, colloids, bacteria, and viruses in the source water cannot pass through the RO membrane, so that the permeable pure water can be strictly distinguished from the impermeable concentrated water.

The pure water and the solution containing the solute are separated by a semi-permeable membrane that can only pass through water. At this time, the water on the pure water side spontaneously passes through the semi-permeable membrane and enters the solution side, and the water level on the solution side rises. This phenomenon is known as penetration. When the liquid level rises to a certain height, the pressure on both sides of the membrane reaches equilibrium, and the liquid level on the solution side no longer rises. At this time, there is a pressure difference on both sides of the membrane, which is called osmotic pressure. If a pressure greater than the osmotic pressure is applied to the solution side, the water molecules in the solution will be squeezed to the pure water side. This process is just the opposite of osmosis, and we call it reverse osmosis. We can see from the process of reverse osmosis that due to the effect of pressure, the water molecules in the solution enter the pure water, the amount of pure water increases, and the solution itself is concentrated.

The reverse osmosis device is mainly composed of a high-pressure pump, an antiscaling dosing pump, a reverse osmosis membrane and a control part. The high-pressure pump pressurizes the source water. Except for water molecules that can pass through the RO membrane, almost all other substances in the water (minerals, organic matter, microorganisms, etc.) Walk.

High-pressure pump

The high-pressure pump provides sufficient water inlet pressure for the reverse osmosis membrane module to maintain the normal operation of the reverse osmosis membrane. The high-pressure pump is made of stainless steel, and the high-pressure pump is equipped with a soft starter to reduce the impact on the membrane when starting.

Reverse osmosis membrane group

The reverse osmosis membrane group is the actuator of the whole desalination system. It is mainly responsible for removing soluble salts in water and a small amount of metal ions, colloids, organic matter and microorganisms remaining in the pre-treatment. Ensure that the water quality of the product meets the design requirements.

This system adopts anti-pollution membrane elements, and is suitable for areas where strict pretreatment is required, but the effluent still contains organic matter and other pollutants. Because the membrane is electrically neutral, it greatly reduces the adsorption of bacteria and microorganisms on the surface of the membrane, and the widest water supply channel makes it not only have strong anti-pollution, but also have effective recovery after chemical cleaning, and are widely used. It is used in the field of regeneration of urban sewage and industrial wastewater, as well as desalination of polluted surface water, reuse of cooling cycle sewage and other fields.

Sodium bisulfite dosing device

Since sodium hypochlorite is added to the ultrafiltration backwash for sterilization, adding the reducing bactericide sodium bisulfite to the RO influent can complement the sterilization. In addition, oxidative residual chlorine can damage the reverse osmosis membrane, adding sodium bisulfite can completely remove residual chlorine. The sodium bisulfite solution remaining in the pipeline also has a strong antibacterial effect. The concentration of sodium sulfite is usually 10%, and the dosage is 20-30mg/L. The device adopts American Pasifida metering dosing pump, made of PVC, resistant to strong oxidation and corrosion.

Antiscalant dosing device

The main function of reverse osmosis is desalination. Some antiscalants specially used for reverse osmosis membranes have excellent effects on various carbonates, sulfates, silicates, phosphate scales and iron oxides that are easy to deposit on the surface of reverse osmosis membranes. Scale inhibition and dispersion performance. The amount of antiscalant added is 2-5ppm. Adding position: Water inlet of primary reverse osmosis security filter.

Reverse Osmosis Cleaning System

After long-term operation, the reverse osmosis module will be subject to certain pollutants that are difficult to wash away. If a small amount of insoluble salt scaling and organic matter accumulate for a long time, the performance of the membrane module will decrease, so it must be cleaned with chemicals. To restore its normal permeate flux and salt removal capacity. The reverse osmosis membrane module can be equipped with a common cleaning system. The reverse osmosis cleaning system consists of stainless steel cleaning pump, cleaning medicine box, 5μm filter and piping.

control instrumentation

In order to control and monitor the normal operation of the reverse osmosis system, a series of monitoring instruments and meters need to be configured: inlet/outlet water conductivity meter, inlet/outlet water PH/ORP meter, product water/concentrated water flow meter, Water pressure gauge, sampling device, etc. At the same time, PLC programmable control system and automatic valve group should be equipped to realize the automatic control of RO recovery system.

After aeration and precipitation, the effluent enters the ultrafiltration device and enters the reverse osmosis for reuse. In order to prevent the ultrafiltration membrane from being polluted by microorganisms, an appropriate amount of oxidant (generally 10-20ppm) is added to kill algae and bacteria during ultrafiltration backwashing. The ultrafiltration effluent enters the reverse osmosis for reuse, in order to prevent the reverse osmosis membrane from being oxidized by excessive oxidant added to the ultrafiltration, a reduction (sodium bisulfite) dosing device is installed at the reverse osmosis water inlet, and an ORP (oxidation potential ) instrument monitoring, and the system is equipped with a chemical cleaning system, which has the functions of sterilization, sterilization, decolorization, and deodorization. The pH of the effluent is weakly alkaline. The reuse system has the characteristics of long service life and low cleaning frequency. Further improving wastewater treatment capacity and reuse rate, reducing energy consumption effectively and practically solves difficulties and problems.

The above are only preferred embodiments of the present invention, so all equivalent changes or modifications made according to the structure, features and principles described in the scope of the patent application of the present invention are included in the scope of the patent application of the present invention.

Claims (5)

1. Electrocoagulation in printing and dyeing wastewater treatment and reuse process, characterized in that: the process steps of the treatment method are as follows: (1) Combining electrochemical technology with traditional chemical precipitation technology, under the action of a direct current electric field, the deep removal of ions is realized simultaneously, and the continuous reaction of the plate with the current, and the electron migration between the cathode and anode of the electrolytic bed , causing an electrochemical reaction. (2) At the same time, the water generates an oxygen discharge at the anode to generate an oxidation reaction, which oxidizes the inorganic and organic substances in the water. (3) Cathode ions are electrified to form nascent hydrogen, which has the strongest reducing ability to remove chroma in water and reduce hexavalent chromium. (4) Since the iron plate produces iron ions and metal ions in the water for coagulation and precipitation during electrolysis, no additional chemicals are needed, and the flocculant is self-produced. (5) Enter the ultrafiltration and reverse osmosis devices for deep removal and reuse. In order to prevent the ultrafiltration membrane from being polluted by microorganisms, add an appropriate amount of oxidant (generally 10-20ppm) to kill algae and bacteria during ultrafiltration backwashing; ultrafiltration The effluent enters the reverse osmosis for reuse, in order to prevent the reverse osmosis membrane from being oxidized by the excessive addition of oxidant for ultrafiltration, and a reduction (sodium bisulfite) is installed at the reverse osmosis water inlet. At the same time, the system is equipped with a chemical cleaning device. When the system is seriously polluted , the cleaning device can be started for chemical cleaning to meet the normal operation of the system. 2. The process of electrocoagulation in printing and dyeing wastewater treatment and reuse according to claim 1, characterized in that: the ultrafiltration membrane is a membrane element made of PAN material. 3. Electrocoagulation according to claim 1 in printing and dyeing wastewater treatment and recycling process, characterized in that: the ultrafiltration device is a hollow fiber ultrafiltration membrane, the outer diameter of the hollow fiber the inside diameter of The hollow fiber tube wall is covered with micropores. 4. The process of electrocoagulation in printing and dyeing wastewater treatment and reuse according to claim 1, characterized in that: the reverse osmosis cleaning system is composed of a stainless steel cleaning pump, a cleaning medicine box, a 5 μm filter and piping. 5. The process of electrocoagulation in printing and dyeing wastewater treatment and reuse according to claim 1, characterized in that: the concentration of the sodium sulfite is usually 10%, and the dosage is 20-30 mg/L.