KR100231331B1 - A treating method for waste water using electrolysis and waste water treating system - Google Patents

Abstract

The present invention is a method for treating malignant wastewater containing COD, BOD, SS, n-hexane, color and total nitrogen, in which an inorganic coagulant (eg, PAC, FeCl _3, etc.) Inject and cross-link, neutralize to maintain a constant pH, electrolyze contaminants using a suitable current in the primary electrolyzer, and inject a polyacrylamide-based polymer coagulant to form a large floc. The remaining pollutants are completely electrolyzed in the secondary electrolyzer by adding activated carbon and zeolite, and the floc separated at the same time flows into the filter bag to separate the solids and discharge the treated water. A method of treating wastewater and a system used in the method.

The wastewater of the present invention can effectively treat malignant wastewater containing COD, BOD, SS, n-hexane, color and total nitrogen by electrolyzing contaminants in the presence of an inorganic coagulant. In other words, by combining chemical treatment methods such as pH adjustment and coagulation extraction, electrochemical methods such as electrolysis, and physical methods such as adsorption and filtration, various pollutants such as COD, BOD, SS, n-hexane, total nitrogen, and color can be greatly reduced. Can give

Description

Wastewater Treatment Method and Wastewater Treatment System Using Electrolysis

The present invention relates to a wastewater treatment method using electrolysis and a wastewater treatment system used in the method. More specifically, the present invention is a method for treating malignant wastewater containing COD, BOD, SS, n-hexane, color, and total nitrogen, in which an inorganic flocculant is injected into the wastewater, with or without coagulant aid, And neutralize to maintain a constant pH, electrolyze contaminants in the primary electrolyzer in the presence of an inorganic flocculant, and inject a polyacrylamide-based coagulant to form a large floc. And the flock which is completely electrolyzed in the secondary electrolyzer by adding zeolite and flotation is flowed into the filter bag and separated into solid and liquid, and the treated water is discharged. It relates to the system used in this method.

Conventional methods for the electrolysis of contaminants in factory wastewater can treat heavy metal components, but COD, BOD, n-hexane and all nitrogen components are not sufficiently treated. Irradiation and ozone treatment are performed.

The malignant wastewater containing all COD, BOD, SS, n-hexane, color and total nitrogen can be purified by simple electrolytic oxidation method such as electrolytic oxidation after coagulant treatment or treatment with coagulant after electrolytic acid treatment. Could not.

The inventors of the present invention have confirmed that the electrolytic oxidation in the presence of an inorganic coagulant significantly improves the purification efficiency while seeking a method for purifying the malignant wastewater relatively easily.

The reason why the pollutants in the wastewater can be purified by electrolytic oxidation is that when the DC voltage is applied to the pollutants in the wastewater and the decomposition voltage is reached, the redox reactions of the metal ions, minerals and organics contained in the wastewater occur. This is because particles having charged easily aggregate together.

However, the general inorganic coagulant plays a role of promoting the coagulation between particles having different charges in the aqueous solution. When the electrolytic reaction is carried out in the presence of the inorganic coagulant, the coagulation efficiency due to the electrolytic oxidation is inevitably increased. This invention is completed using the principle.

Accordingly, an object of the present invention is to inject an inorganic coagulant into the waste water in the presence or absence of a coagulant, neutralize it to maintain a constant pH, and in the presence of the inorganic coagulant, electrolysis using a constant current in a primary electrolytic cell, followed by polyacrylamide Injecting a polymer coagulant to form a large floe, the remaining pollutant is introduced into the secondary electrolyzer by adding activated carbon and zeolite, and the floc separated from the flotation flows into the filter bag and is separated into solid solution. Is to provide a method for treating wastewater consisting of effluent.

Another object of the present invention is a metering tank having a wastewater inlet through which the wastewater is introduced by the raw water pump from the wastewater tank and a wastewater mixture solution outlet through which the wastewater mixture is discharged quantitatively, and neutralizing the wastewater mixture solution discharged from the metering tank to a constant pH. Primary electrolyzer with electrolytic bath to electrolyze the tank and wastewater mixture, polymer flocculation tank which injects polyacrylamide-based polymer flocculant into the inflowed wastewater, and injects activated carbon and zeolite into the influent wastewater. Secondary electrolysers, which are electrolyzed and at the same time with electrodes having a structure in which flocs can be separated and floated, are connected to each other, and a transport tube is provided between the polymer agglomeration tank and the secondary electrolyzer so that the polymer The flocculated wastewater from the coagulation tank is transferred to the secondary electrolyzer, and the floating matter is separated from the top of the secondary electrolyzer. A floc conveying device is installed to transfer the scum to a scum tank by means of a rubber plate installed on a chain conveyor, and an ionization unit and a filtration unit equipped with a filter bag for separating liquids from flotation at the lower outlet of the scum tub. It is to provide a wastewater treatment system having a device.

1 is a process chart showing an example of the wastewater treatment method of the present invention.

2 is a schematic diagram of a wastewater treatment system used in the wastewater treatment method of the present invention.

3 is a diagram showing the electrode connection diagram of the primary electrolyzer and the secondary electrolyzer in the wastewater treatment system of the present invention (A: electrode connection diagram of the primary electrolyzer, b: electrode connection diagram of the secondary electrolyzer).

Explanation of symbols for main parts of the drawings

1: Inlet 1 ': Outlet

2: weighing tank 3: neutralization tank

4: primary electrolytic cell 5: polymer coagulation tank

6: secondary electrolyzer 7: transfer pipe

8: discharge flow control tank 9: discharge tank

10 reusable tank or outlet 11 scum

12 filter bag 13 treated water tank

In the wastewater treatment method of the present invention, an inorganic coagulant is injected into the waste water in the presence or absence of a coagulant, neutralized to maintain a constant pH, and in the presence of the inorganic coagulant, electrolyzed using a constant current in a primary electrolytic cell, and then Injecting an amide polymer coagulant to form a large floc, the remaining pollutant is completely electrolyzed in secondary cell by adding activated carbon and zeolite, and floc separated flotation flows into filter bag for solid-liquid separation and treatment The water consists of the discharge.

The wastewater treatment method of the present invention will be described step by step with reference to FIG.

1) The wastewater is transferred to the weighing tank at a flow rate of 17 liters per minute, and the inorganic coagulant is metered in the presence or absence of the flocculating aid at a ratio of 51 cc / Min to form a wastewater mixture. Inorganic coagulants include aluminum sulfate (Al ₂ (SO ₄ ) _{3 18} H ₂ O), ferrous sulfate (FeSO _{4 ·} 7H ₂ O), ferric sulfate (Fe ₂ (SO ₄ ) ₃ ) Ferric chloride, FeCl ₃ · 6H ₂ O, aluminum potassium sulfate, Al ₂ (SO ₄ ) ₃ K ₂ SO _{4 ·} 24H ₂ O), polyaluminum chloride, Al (OH) _n Cl _6-n (hereinafter referred to as PAC), sodium aluminate (NaAlO ₂ ), aluminum ammonium sulfate, Al ₂ (SO _{4) 3} (NH ₄ ) ₂ SO _{2 ·} 24H ₂ O, Chlorinated copperas (FeCl + Fe (SO)), waste look (FeCl ₂ + FeSO ₄ · 7H ₂ O), and the like. The use of these inorganic coagulants allows the contaminants in the wastewater to aggregate to form flocs and to be easily charged during electrolysis.

Meanwhile, the coagulant aid may be added to the inorganic coagulant of the present invention to improve the coagulation effect.The coagulant aid may include clay (bintonite, Al ₂ O ₃ , Fe ₂ O ₃ , 3MgO, 4SiO ₂ , 7H ₂ O), calcium hydroxide ( calcium hydroxide, Ca (OH) ₂ ), calcium oxide (calcium oxide, CaO), activated silica (xSiO ₂ ).

2) Transfer the wastewater mixture to the neutralization tank and inject NaOH or H ₂ SO ₄ to a fixed pH while stirring well. The process up to this stage can be adjusted automatically.

3) Put the pH-adjusted wastewater mixture into the first electrolytic cell with the electrode inserted in the center side and energize the DC voltage (6-12V) and stir while gradually increasing the voltage to 20V.

4) Inject the polyacrylamide polymer coagulant having a molecular weight of about 1200 at a rate of 120 cc / Min into the wastewater mixture of the previous step and floc the wastewater while stirring.

5) Insert the flocculant wastewater mixture into the secondary electrolyzer with electrodes and add activated carbon and zeolite to BOD, COD, SS, n-hexane, and all nitrogen which were not decomposed in the primary electrolyzer. As shown in FIG. 2, the floc which is completely discharged again and floated at the same time is transferred to the scum tank by the floc feeder located at the top of the secondary electrolyzer, and the treated water is transferred to the treated water tank.

At this time, the activated carbon and the zeolite adsorb the pollutant remaining after the first electrolysis and have the action of promoting the electrolysis by removing the decomposer of the fine particles after the electrolysis.

6) The floc collected in the scum tank and some of the water solution flow into the filter bag attached to the bottom of the scum tub to separate the solids. The separated treatment liquid is transferred to the treatment water tank, and the solids of the filter bag are treated in the bag state.

In the above steps 3) and 5), by applying a direct current voltage to the electrolyte aqueous solution and gradually raising the voltage, the residual current gradually increases, and the current rapidly rises at a constant voltage. At the same time, oxygen gas and hydrogen gas are generated at the anode and cathode, respectively. . At this time, the residual current rises to about 100 A.

The voltage applied in this process is the decomposition voltage, and when this voltage is reached, a significant amount of current flows to cause electrolysis. When electrolysis begins, it induces the following electrochemical reactions in wastewater:

1) Precipitation of metal ions in wastewater and oxidation and reduction of organic and inorganic substances

2) Ions contained in the wastewater generate electrons on the electrode surface, and the oxidizing agent, reducing agent and metal hydroxide generated at this time aggregate or react with the soluble materials in the wastewater.

3) The solute or colloid becomes a more stable colloid or compound, precipitates in an insoluble state, and is easily aggregated.

4) Discharges at the electrodes agglomerate by decreasing the zeta potential (ζ-Potential, interfacial electrokinetic potential) of the colloid or floe. Here, the zeta potential refers to the potential difference that occurs at the interface between the solid and the liquid in contact with each other.

5) Fine gas generated at the time of electrolysis is adsorbed on the floc and promotes flotation.

6) Sterilization of general bacteria and Escherichia coli by oxygen of generator

Various contaminants can be removed by the electrochemical reaction, and COD, BOD, SS, n-hexane, total nitrogen, and color of waste water can be reduced.

On the other hand, the ionization ionization reaction in the electrolytic cell can be expressed as follows.

1) Reaction of water at the anode (+) and the cathode (-)

Positive reaction

^{_{H 2 O - 2e - → ½O}} 2 + 2H +

Cathode (-) reaction

2H ^{+ +} 2e ^- → H ₂

2) Water reaction when chlorine ion is contained in water

2Cl ^{- -} 2e ^- → Cl ₂

_{Cl 2 + H 2 O ↔ HOCl} + H + + Cl -

HOCl ↔ H ^{+ +} OCl ^-

3) Underwater reaction of generated chlorine gas and ammonia

NH ₃ + HOCl → NH ₂ Cl (Monochloramine) + H ₂ O

NH ₂ Cl + HOCl → NHCl ₂ (Dichloramine) + H ₂ O

NHCl ₂ + HOCl → NCl ₃ (Nitrogen Trichloride) + H ₂ O

This reaction forms residual chlorine.

4) the reaction of chloramine

NH ₂ Cl + NHCl ₂ + HOCl → 4HCl + N ₂

4NH ₂ Cl + 3Cl ₂ + H ₂ O → N ₂ + N ₂ O + 10HCl

2NH ₂ Cl + HOCl → N ₂ + H ₂ O + 3HCl

NH ₂ Cl + NHCl ₂ → N ₂ + 3 HCl

In this reaction, gas is produced by the disappearance of chloramine.

H ₂ , O ₂ , N _2, etc. generated during the electrolysis process are released in a gas state that does not dissolve in water.

On the other hand, the wastewater treatment system of the present invention is composed of a metering tank, a neutralization tank, a primary electrolytic bath, a polymer agglomeration tank, a secondary electrolytic bath, a scum bath and a filter bag.

Hereinafter, the wastewater treatment system of the present invention will be described in detail with reference to FIG.

The metering tank 2 has a wastewater inlet 1 through which wastewater is introduced by the raw water pump from the wastewater tank, and a wastewater mixture solution outlet 1 'through which the wastewater mixture is discharged quantitatively. In the metering tank 2, PAC is metered in and the wastewater mixed liquid is produced. In the bottom of the metering tank 2, the neutralization tank (3) is located, is introduced into the neutralized waste water mixture is quantitative discharge tank 3, suitably adjusting the pH to this injection the NaOH or H ₂ SO ₄ to the stirred do. The primary electrolytic cell 4 is provided in contact with the neutralization tank 3 side surface, and the electrode is inserted in the center side surface of the electrolytic cell 4. The electrode used in the present invention is made of an alloy of platinum and titanium and consists of eight sheets having a size of ^w 100 X ^L 400 X ^T 1, and the electrodes are connected as shown in FIG. 3. In the electrolytic cell 4, electrochemical reaction occurs by electrolyzing the wastewater introduced from the neutralization tank 3 while stirring.

The polymer agglomeration tank 5 is in contact with the side surface of the electrolytic cell 4, and the polymer flocculant is added to the wastewater introduced from the electrolytic cell 4 to stir to flush the waste water. The secondary electrolyzer 6 is in contact with the side of the polymer agglomeration tank 5, and the transfer tube 7 is connected between the polymer agglomeration tank 5 and the secondary electrolyzer 6 so that the polymer agglomeration tank 5 is connected. Flocked left waste water of) flows into the secondary electrolyzer (6). An ionization device is installed in the center of the electrolytic cell 6, and the ionization device is composed of 20 electrodes, such as the electrodes of the first electrolytic cell 4, as shown in FIG. It is connected.

Discharge flow rate control tank 8 and the discharge tank (9) is located at the top of the ionization device to suck the treated water from the bottom of the tank to discharge to the reuse tank or outlet (10). In the secondary electrolyzer 6, activated carbon and zeolite are charged to completely discharge the wastewater, and at the same time, flotation and separation. The floated floc flows to the scum tank 11 installed on the upper side of the electrolytic cell by a rubber plate mounted on the chain conveyor located at the top of the electrolytic cell.

The flock of the scum tank 11 flows into the bottom outlet of the scum tank 11, and the floc of the scum tank 11 flows in. The liquid is separated from the filter bag 12, and the liquid is transferred to the treated water tank 13. Solids are packaged and disposed of in bags.

In the drawings, reference numeral 14 denotes an overflow for flow control.

Hereinafter, the wastewater treatment method of the present invention will be described with reference to Examples. However, the present invention is not intended to be limited to this embodiment.

EXAMPLE

After the factory wastewater (pH 7, COD 120 ppm) is transferred to the weighing tank at a flow rate of about 17 L per minute, PAC is metered in at a rate of 51 cc / Min to form a wastewater mixture. The wastewater mixture is transferred to the neutralization tank at a flow rate of 17 l / min, and the pH is adjusted to 5.5-7 by injecting NaOH while stirring well. The pH-adjusted wastewater mixture is placed in a first electrolytic cell with an electrode inserted in the center side and energized by direct current voltage (6-12 V) and stirred while gradually raising the voltage to 20 V. Into the wastewater mixture of the primary electrolyzer, polyacrylamide (product name SS-100) is injected as a polymer flocculant at a rate of 120 cc / Min, and the wastewater is flocculated with stirring. The flocculated wastewater mixture is placed in a secondary electrolyzer with electrodes, and 30 liters of activated carbon and 100 liters of zeolite are added to the BOD, COD, SS, NH, and TN that are not decomposed in the primary. Energize the voltage and slowly increase the voltage to 20 V, stir again to deliver it completely, and at the same time transfer the floc separated from the flotation to the scum tank by the floc feeder located at the top of the secondary electrolyzer. Transfer. The floc and some water solution collected in the scum tank are separated into solids by flowing into a filter bag attached to the bottom of the scum tub. The solid-liquid separated liquid is transferred to the treated water tank and the solids filled in the filter bag are treated in the filter bag state. Activated carbon and zeolite used in this process are replaced when no activity occurs. In this case, it takes 48 hours.

The treated water was collected from the treated water tank, and the measured BOD, COD, SS, and T-N were 55, 35, 25, and 60 ppm, respectively.

In the present invention, the wastewater can be effectively treated with malignant wastewater containing COD, BOD, SS, n-hexane, color and total nitrogen by electrolyzing contaminants in the presence of an inorganic coagulant. In other words, by combining chemical treatment methods such as pH adjustment and coagulation extraction, electrochemical methods such as electrolysis, and physical methods such as adsorption and filtration, various pollutants such as COD, BOD, SS, n-hexane, total nitrogen, and color can be greatly reduced. Can give

Claims (3)

In a method of treating malignant wastewater containing COD, BOD, SS, n-hexane, color and total nitrogen, the wastewater is neutralized to maintain a constant pH and electrolyzed contaminants in a primary electrolyzer in the presence of an inorganic coagulant, The polyacrylamide-based polymer coagulant is injected to form a large floe, and the remaining pollutant is completely electrolyzed in the secondary electrolyzer by adding activated carbon and zeolite, and the floc separated in the flotation flows into the filter bag and is separated into solid solution. Treatment method for wastewater consisting of effluent. The method of treating wastewater according to claim 1, wherein the inorganic coagulant is selected from aluminum sulfate, ferrous sulfate, ferric sulfate, ferric chloride, potassium alum, aluminum polychloride, sodium aluminate, ammonium alum, copper chloride, and ferric. A metering tank with a wastewater inlet from which the wastewater enters the wastewater from the wastewater tank and a wastewater mixture outlet through which the wastewater mixture is discharged quantitatively, a neutralization tank that adjusts the wastewater mixture discharged from the metering tank to a constant pH, and a wastewater mixture The first electrolytic cell in which the decomposing electrode is installed, the polymer coagulant injecting and flocculating the polymer flocculant into the inflowed wastewater, and the activated carbon and zeolite in the inflow of the inflow wastewater are completely electrolyzed. Secondary electrolysers, on which electrodes with separable structures are attached, are connected to each other, and a transfer pipe is installed between the polymer agglomeration tank and the secondary electrolyzer so that the wastewater flocculated in the polymer agglomeration tank by this transfer tube. Is transported to the secondary electrolyzer, and the upper part of the secondary electrolyzer is equipped with a floating material that is separated from the float on the chain conveyor. A floc feed device for transferring a scum tank to a scum tank by a flat plate is provided. A wastewater treatment system having an ionization unit and a filtration unit having a filter bag for separating solid-liquid matter from the lower outlet of the scum tank is installed.

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