KR19990000168A - Wastewater Treatment Method and Wastewater Treatment System Using Electrolysis - 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 flocculant (eg, PAC, FeCl _3, etc.) is injected into the wastewater in the presence or absence of a coagulant aid. Cross-linked, neutralized to maintain a constant pH, electrolyzed using a suitable current in a primary electrolyzer, and then injected with a polyacrylamide-based polymer coagulant to form a large floe, and the remaining pollutant The activated floc and zeolite are completely electrolyzed in the secondary electrolyzer, and the floc separated at the same time flows into the filter bag, solid-liquid separated, and the treated water is discharged. And to systems used in this method.

The wastewater treatment method of the present invention can treat malignant wastewater including COD, BOD, SS, n-hexane, color and total nitrogen. 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, NH, TN, and chromaticity can be removed or reduced. .

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 the flocculant is injected into the wastewater in the presence or absence of a coagulant, and reacted with each other. , Neutralization to maintain a constant pH, and electrolyzed using a suitable current in the primary electrolyzer, and then injected into a polyacrylamide-based coagulant to form a large floe (Flock), the remaining pollutants are activated carbon and zeolite The floc which was electrolyzed in the secondary electrolyzer and flotation separated at the same time flows into the filter bag and solid-liquid separation, and the treated water is discharged. It is about the system used.

Conventional wastewater treatment methods are mainly focused on physical treatment, chemical treatment, and biological treatment. However, due to the limitations of physical treatment, the problems of secondary pollution after treatment, and the selectivity of treatable wastewater during biological treatment. Problems have been shown in the treatment of malignant wastewater.

The present invention has been studied to solve the above problems, by treating the wastewater in parallel with the electrochemical method using the electrolysis and the adsorption, filtration, which has never been used, COD, BOD, SS, NH, TN, Various environmental pollutants such as chromaticity were reduced and various pollutants could be easily removed.

Accordingly, an object of the present invention is to inject a flocculant into the waste water in the presence or absence of a coagulant, to react and collect, neutralize to maintain a constant pH, and polyacrylamide crab polymer after electrolysis using a constant current in a primary electrolyzer. A flocculant is injected to form a large floe, and the remaining pollutant is introduced into the secondary electrolyzer by adding activated carbon and zeolite, while flotation separated from the flotation flows into the filter bag to separate the liquid and discharge the treated water. The present invention provides a method for treating wastewater.

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;

Figure 3 is a view 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 first electrolyzer, b: electrode connection diagram of the secondary electrolyzer).

* Description of the symbols for the 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 rate control tank 9: discharge tank

10: reuse tank or outlet 11: scum fitting

12: filter bag 13: treated water tank

In the wastewater treatment method of the present invention, a flocculant is injected into the wastewater in the presence or absence of a coagulant, the reaction mixture is collected, neutralized to maintain a constant pH, and electrolyzed using a constant current in the primary electrolyzer, and then polyacrylamide-based A large floe is formed by injecting a polymer flocculant, and the remaining pollutant is completely electrolyzed in the secondary electrolytic cell by adding activated carbon and zeolite, while flotation separated from the flotation flows into the filter bag to separate the solid and liquid. Discharge.

The wastewater treatment method of the present invention will be described step by step with reference to FIG. 1 as follows:

1) The wastewater is transferred to the weighing tank at a flow rate of 17 liters per minute, and then the coagulant is metered in the presence or absence of the coagulant at a ratio of 51 cc / Min to form a waste water mixture. At this time, an inorganic coagulant or an organic coagulant may be used as the coagulant. 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), potassium potassium sulfate (Al ₂ (SO ₄ ) ₃ K ₂ SO ₄ · 24H ₂ O), polyaluminum chloride, Al (OH) _n Cl _6-n ), 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, and organic coagulants include polyacrylamines, polymer flocculants such as polyethylene amines, dodecylamine, and octadecylamine. Cationic surfactants such as acetates or anionic surfactants such as sodium laurate and dodecyl benzene sulfonate. The use of these flocculants causes the contaminants in the wastewater to aggregate to form flocs and to be easily charged during electrolysis.

On the other hand, the coagulant of the present invention can be added to the coagulant aid to improve the coagulation effect, such coagulant aid, such as clay (bentonite, 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 apply DC voltage (6-12V) and stir while gradually increasing the voltage to 20V.

4) Inject the polyacrylamide polymer flocculant at the rate of 120cc / Min into the wastewater mixture of the previous stage and flocculate it. As the polyacrylamide polymer coagulant, a polyacrylamide system having a molecular weight of about 1200 such as SS-200H, SS-200, SS-300, SS-500, SS-100, SS-120, SS-130, SS-140 is possible. Of these, SS-120 is preferable.

5) Put the flocculant wastewater mixture into the secondary electrolyzer with electrodes, and add activated carbon and zeolite to BOD, COD, SS, NH, and TN that were not decomposed in the primary electrolyzer. The floc which is electrolyzed 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 steps 3) and 5), the DC current is supplied to the electrolyte solution and the voltage is gradually raised to increase the residual current, thereby rapidly increasing the current at a constant voltage, and simultaneously generating oxygen gas and hydrogen gas at the anode and cathode. . At this time, the residual current rises to about 100A.

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 the wastewater:

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

2) The ions contained in the wastewater generate electrons on the electrode surface, and the oxidizing agent, reducing agent and metal hydroxide produced 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 of the colloid or floe (ζ-Potenetial, interfacial electrokintic potential). 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-H, T-N, and chromaticity 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 - → 1}} / 2O 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 + 3HCl

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. 2.

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 is composed of eight sheets of ^W 100 × ^L 400 × ^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 surface of the polymer tank 5, and the transfer tube 7 is connected between the polymer agglomerate 5 and the secondary electrolyzer 6 so that the polymer agglomerate 5 is connected. Flocked wastewater of is introduced into the secondary electrolyzer (6). An ionization device is installed in the center of the electrolytic cell 6, and the ionization device is provided with 20 electrodes, such as the electrodes of the first electrolytic cell 4, and the electrodes are connected as shown in FIG. It is.

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 discharge port of the scum tank 11 and the floc of the scum tank 11 flows in, and the liquid is separated from the filter bag 12 to transfer the liquid to the treated water tank 13 and the solids in the bag. Should be packed in a bag and treated.

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

Hereinafter, the wastewater treatment method of the present invention will be described by way of example. However, the present invention is not intended to be limited to this embodiment.

EXAMPLE

Factory wastewater (pH 7, COD 120ppm is transferred to the weighing tank at a flow rate of about 17ℓ per minute, and then PAC is metered in at a rate of 51cc / Min to make the wastewater mixture. NaOH is injected with stirring to adjust the pH to 5.5-7.The pH-adjusted wastewater mixture is placed in a primary electrolytic cell with an electrode inserted in the center side and energized with a DC voltage (6-12V) and the voltage is gradually reduced to 20V. Inject the polyacrylamide (product name SS-100) as a polymer flocculant at a rate of 120 cc / Min into the wastewater mixture of the primary electrolyzer and flocculate the wastewater with stirring. 30 liters of activated carbon and 30 liters of zeolite were added to BOD, COD, SS, NH, and TN that were not decomposed in the secondary electrolyzer, and the DC voltage was energized and the voltage was gradually increased to 20V. Stirring while raising The floc separated from the flotation 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. Solid-liquid separation flows into the filter bag attached to the bottom of the comjo, and 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. Replace at a point not shown, which takes 48 hours after loading.

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

The wastewater treatment method of the present invention can treat malignant wastewater including COD, BOD, SS, n-hexane, color and total nitrogen. In other words, various chemical contaminants such as COD, BOD, SS, NH, TN, and chromaticity can be removed or reduced 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. .

Claims (3)

In the method of treating malignant wastewater containing COD, BOD, SS, n-hexane, color and total nitrogen, the flocculant is injected into the wastewater in the presence or absence of a coagulant, and the reaction is concentrated and neutralized to maintain a constant pH. After electrolysis using a constant current in the primary electrolyzer, a polyacrylamide-based polymer coagulant is injected to form a large floc, and the remaining pollutant is completely electrolyzed in the secondary electrolyzer by adding activated carbon and zeolite. At the same time, the floc separated from the flotation flows into the filter bag to separate the solid and the treated water is discharged. The coagulant according to claim 1, wherein the coagulant is aluminum sulfate, ferrous sulfate, ferric sulfate, ferric chloride, potassium alum, polyaluminum chloride, sodium aluminate, ammonium alum, chloride chloride, ferric, polyacrylamine, polyethylene amine, dodecylamine , Octadecyl amine acetate, sodium laurate, and dodecyl benzene sulfonate, wherein the coagulant is selected from clay, calcium hydroxide, calcium oxide, and activated silicic acid. 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 Primary electrolyzer with decomposing electrode, polymer coagulant injecting and flocculating polymer flocculant into the inflowed wastewater, and activated carbon and zeolite are introduced into the inflow wastewater to completely electrolyze and floc 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 waste water flocculated in the polymer agglomeration tank by the transfer pipes is installed. Rubber which is transported to the secondary electrolyzer and the floating material is separated from the upper part of the secondary electrolyzer in the chain conveyor The flock transport device for transporting the scum twos (Scum) is provided by which, Scotland keomjo bottom outlet is a water treatment system having an ionization chamber ionizing device and filter device that is installed to solid-liquid separation filter bag material injury.