KR20050028127A - Wastewater treatment method - Google Patents

Abstract

To provide a new treatment process in which problems in physical, chemical and biological treatment processes are not generated, or which minimizes the problems although the problems are generated, i.e., a method for treating wastewater by electrolysis, and an apparatus for treating wastewater by the method. The method for treating dyeing wastewater comprises: a step of installing a power supply unit for supplying a DC power source and a pair of electrodes formed of Fe or Al such that distance between the electrodes is maintained to a range of 7 to 15 cm based on 100 L of wastewater amount, and flowing electrolyte having an electrolyte concentration of 0.1 to 1.0% into a reactor which is installed under the electrodes, and in which an agitator is installed in an amount corresponding to 3 to 5% of the wastewater amount in case that the waste water amount is 10 L or less and flowing the electrolyte into the reactor in an amount corresponding to less than 1% of the wastewater amount in case that the waste water amount is 50 to 200 L; a step of coagulating, adsorbing, precipitating and floating contaminants in the dyeing wastewater by metal ions produced from the electrodes, and hydrogen and oxygen by electrolyzing wastewater as impressing electric current having a current density of 0.1 to 0.15 A/cm^2 to the electrodes for 20 to 30 minutes in proportion to concentration of wastewater; and a step of removing scum and ozonizing filtered dyeing wastewater by filtering the electrolyzed dyeing wastewater.

Description

Wastewater treatment method using electrolysis {Wastewater treatment method}

The present invention relates to a method of treating dyeing wastewater by electrochemical oxidation and electroflatation at an appropriate pole spacing and current density using an iron (Fe) or aluminum (Al) electrode, that is, a wastewater treatment method using electrolysis. It is about.

In general, wastewater treatment methods are largely classified into physical, chemical and biological treatments. Physical treatment methods are chemical treatments that do not occur at all, and are merely treatments by physical action. It is called.

In addition, the chemical treatment industry is a method mainly using a chemical reaction, and is a treatment method using a neutralization tank, oxidation, reduction reaction tank, flocculation tank, adsorption tower and the like.

In addition, the biological treatment method is a method of treating wastewater using microorganisms, and is a treatment method using a reaction facility such as an activated sludge tank or an activated sludge tank.

However, the physical treatment method has the disadvantage that the waste water treatment rate is slow when the temperature is low or when the pollution is high, and the chemical treatment method uses a large amount of chemicals, and thus, the secondary pollution problem caused by the treatment reagent is followed. Followed, there is a problem that the sludge is excessively generated.

In addition, the biological treatment method has recently been in the spotlight because it can prevent the problem of secondary pollution, but the non-degradable wastewater containing heavy metals, flame retardant salts, such as wastewater discharged from dyeing factories, plating factories, etc. Since the oxygen transfer rate is lowered due to the high temperature of more than 40 ℃, often the inside of the aeration tank of the wastewater treatment system using microorganisms is difficult to survive the sludge protozoa, so the wastewater treatment efficiency is extremely low in the summer.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, the main object of the present invention is to solve the problem even if the problem does not occur or the problem occurs in the above-described physical, chemical, biological treatment method It is proposed to minimize the new treatment method, that is, wastewater treatment method using electrolysis.

An object of the present invention described above is to install a pair of electrodes made of iron or aluminum with a power supply device for supplying DC power at a distance of 7 to 15 cm, and an electrolyte concentration of 0.1 to 1.0 in a reactor provided with a stirring device under the electrode. Introducing a dye wastewater to which an electrolyte of% is added; Electrolyzing while applying a current density of 0.1 ~ 0.15A / cm ² to the electrode for 20-30 minutes to agglomerate, adsorption, precipitation, contaminants in the dye wastewater by the metal ions and hydrogen and oxygen generated in the electrode Levitating; The electrolytically treated dye wastewater is filtered by the electrolysis wastewater treatment method comprising the step of removing scum and ozone treatment.

In addition, a power supply means for supplying a direct current power source, a pair of electrodes made of iron or aluminum designed to a distance of 7 ~ 15cm, a stirring means installed in the lower portion of the electrode, dyeing means for filtering the electrolyzed dyed waste water And ozone treatment means for removing scum and ozone treatment.

Hereinafter, preferred embodiments of the present invention will be described in more detail.

For reference before the embodiment description, if you look at the history of the synthetic dye development (history) it can be seen that the design of the dye molecules based on the chromophore, the color tone. It is most effective when covalent double bonds (-N = N-) are arranged in a long chain between chromophores, whereas when -CH ₂ , -NH, -O-, -SO _2, etc. are inserted between the bonds in which double bonds are disconnected The effect is reduced, making the color lighter. In addition, when two or more negative groups such as -NO ₂ , -SO ₃ H, -COOH, and -CH ₃ are present in the ortho or para position, a dye having a deep color or dyeing ability is obtained. When they bring about changes in properties, water and bonding position by oxidation, sulfur source and substitution reaction, the color becomes pale or colorless. Such dye is the first component to be removed in wastewater treatment.

Here, the wastewater treatment method of the present invention is summarized as electrolyzing raw wastewater and then treating it by electrochemical oxidation treatment and flotation.

When the wastewater is treated by electrolysis as described above, the electrode to be used as the positive electrode and the electrode to be used as the negative electrode are immersed in the electrolyte in the electrolytic cell and electrolytically applied by applying a DC power between the positive electrode plates. The electrolysis reaction decomposes the dye by oxidation and reduction at the interface between the solutions, and the metal ions precipitated at the anode are removed by suspended solids generated during electrolysis and by physicochemical actions such as precipitation, adsorption and aggregation.

At this time, wastewater treatment is performed by electrolytic oxidation by oxygen generated at the anode and electrolytic coagulation which occurs as the metal ions eluted from the anode are precipitated into the metal oxide. Strong activity and low zeta (zeta) has the advantage of excellent aggregation, adsorption and settling properties.

In the present invention, the iron (Fe) electrode and the aluminum (Al) electrode in the configuration of the electrode should be mixed, but the distance between the electrodes must be constant electrolysis. The reason why the iron electrode is mixed with the aluminum electrode is that if only the iron electrode is used for a certain time, the surface is severely contaminated and the electrode plate is reduced or the reactivity of the electrode is weakened and the electrolysis rate is lowered.

The distance between the two electrodes is preferably set to 7 to 15 cm (experimental value) based on 100 L of wastewater. If the distance between the electrodes is smaller than the set value, the conduction of current is uneven, and if the inter-pole distance is larger than the set value, the absorbance and concentration removal rate are lowered, resulting in waste of power.

In addition, in the present invention, to increase the electrical conductivity of the sample, an electrolyte having an electrolyte concentration of 0.1 to 1.0% was added. When the concentration of the electrolyte is out of the above set range, the power consumption increases or the excellent wastewater treatment effect cannot be obtained.

On the other hand, when water is electrolyzed, oxygen gas having a bubble size of 10 to 30 µ is generated at a ratio of 2: 1 at the cathode. That is, in an acidic solution, _{^{2H + + 2e - → H 2}} , H 2 O → 1/2 O 2 ↑ + 2H + + 2e - and, in the alkali solution ^{_{2H 2 O + 2e - → H}} 2 ↑ + 2OH -, 2OH ^- → 1 / 2O ₂ + H ₂ O + 2e and eventually H ₂ O → H ₂ + 1 / 2O ₂ .

When two aluminum electrodes are used as redox electrodes and a predetermined current is passed, the following electrochemical reactions occur on the surfaces of the two electrodes.

Oxidizing electrode: Al → Al ³⁺ + 3e ^-

^{_{2H 2 O → 4H + + O}} 2 ↑ + 4e -

_{^{↑ + 2OH → H 2 - 2H}} 2 O + 2e -: reducing electrode

In the anode, oxidation of aluminum, which is an electrode material, is actively performed, and H ⁺ ions and oxygen gas are generated by oxidation of water. On the other hand, the hydrogen gas generated by the reduction of water is generated on the surface of the cathode, and at the same time OH ^- ions are generated.

At this time, a precipitate of Al (OH) ₃ formed in the anode is formed and the precipitate of Al (OH) ₃ generated adsorbs the colloidal poorly soluble dye adsorbed on the surface. Colloidal flame-retardant dyes adsorbed on Al (OH) ₃ precipitated surface were produced by O ₂ And H ₂ is floated on the water surface in a foamed state, so that the dye can be removed from the wastewater by separating and collecting it.

In the case of treating wastewater by electrolysis in this manner, an operation technique is used in which the polarity of the electrodes is alternately changed at time intervals in order to balance the anode by dissolution of aluminum.

Factors affecting the treatment efficiency of the electrolytic flotation method described above are various, such as the current density applied to the electrode, the electrolysis time, the electrical conductivity of the wastewater, the hydrogen ion concentration, the temperature, the type of salt contained in the wastewater, and the distance between the electrodes. . As a result of the basic research on the various parameters in the present invention, it was found that the processing efficiency is the best when given a certain data condition.

Electroflation (electroflatation) is a kind of technique that is very similar in terms of the mechanism and the physicochemical treatment by the above-mentioned aggregation, adsorption, precipitation, filtration. It is a method that can exert an excellent effect on the treatment of wastewater containing dyes discharged in the colloidal phase due to these characteristics.

The electrochemical treatment method employing two iron electrodes as an anode and a cathode is a colloidal poorly soluble dye on the surface of the iron hydroxide precipitate produced as a result of oxidation of the iron electrode, similar to the electrolytic flotation using aluminum described above. It corresponds to an electrolytic treatment method combining the adsorption and precipitation mechanism using the phenomenon of particle adsorption and the dye decomposition mechanism by Fe ³⁺ generated as a result of the electrode reaction.

Representative electrode reactions and solution phase reactions in the electrolytic treatment of dye wastewater using iron electrodes are as follows.

Anode: Fe → Fe ²⁺ + 2e

Fe ²⁺ = Fe ³⁺ + e

mFe ³⁺ + dye Fe ²⁺ → mFe ²⁺ + dye oxide

dyes → dye oxide + ne

Reduction ^{_{electrode: 2H 2 O + 2e - →}} H 2 + 2OH -

Fe ³⁺ + e ^- → Fe ²⁺

The Fe (OH) ₂ precipitate spontaneously oxidizes in solution and is slowly hydrolyzed to Fe ₂ O ₃ on the colloid in hydrated state. In this process, the chlorides of the heavy metal dyes are adsorbed onto the colloidal precipitated surface and can be removed from the wastewater.

This process corresponds to a kind of electrocoagulation, but it can be said that the decolorizing effect by the oxidation reaction of the dye by Fe ³⁺ generated as a result of the electrode reaction is unique.

The balance of the original wastewater chromaticity by the electrochemical effect of the redox reaction is broken, and the wastewater treatment effect is maximized by the precipitation, adsorption, flocculation, and flotation effects. At this time, the wastewater treatment by the electrolysis reaction is carried out by treating the dissolved metal ions by physicochemical methods such as sedimentation, adsorption, and flocculation by dissolving the dissolved metal ions by oxidation and reduction at the interface between the solutions.

Hereinafter, the present invention will be described in more detail with reference to Examples.

(Example 1)

In order to test the effect of wastewater treatment by electrolysis, the wastewater treatment effect was tested for red, yellow and blue acid dyes and other wastewater discharged from plating, leather, food, and paper mills. In this example, the dyeing wastewater was treated with dilute method using acidic wastewater, which is known to be the most difficult to decompose among various temperatures and chromaticities, and evaluated the effect according to the electrode material. The applicability of the electrolytic treatment of wastewater was tested by evaluating removal rates for power consumption.

In the present invention, the dyeing wastewater was treated with a dilution method using acidic wastewater, which is known to be the most difficult to decompose at various temperatures and chromaticities, and evaluated the effect according to the electrode material, and according to the distance, current density, electric current concentration, electrolyte concentration and consumption. The applicability of the electrolytic treatment of wastewater was tested by evaluating removal rates for power and the like.

Wastewater treatment effect test was evaluated by mixing the electrolyte in the test solution, electrolysis, filtration and measuring the concentration.

Printed wastewater concentration was 0.1 ~ 1.0% of electrolyte for 1000ppm and experimented with proper current density. After more than 20 ~ 30 minutes, more than 95% of chromaticity was removed. The lower the electrolyte concentration, the higher the power consumption and the removal rate. It improved, but over time, power consumption became nearly constant.

Under the same conditions of pH and voltage electrolyte concentration, COD yielded a high removal rate of 98.9% from 970 mg / 1 of raw wastewater to 50 ppm of treated water. According to the wastewater treatment method of the invention, when applied to the field was able to confirm the possibility of treating the wastewater very effectively.

As a result, the removal rate was improved as the current density increased. Especially, when the current density was 0.1 ~ 0.15A / cm ² , the removal rate was 98%. In addition, the inter-distance effect showed 98% removal rate when the distance between electrodes was 7-15cm.

(Example 2)

Depigmentation effect according to the interpolation distance as the experimental data value for the sample number of 200ppm of dye, electrode plate area 15cm ² , proper electric charge concentration 0.4 ~ 0.8Ahr / 1 and current density 0.1 ~ 0.15A / cm ² Was evaluated. As a result, when the electrolyte concentration was 0.1% to 1.0%, it was confirmed that the removal rate proceeded more than 98% after 20 minutes.

The results of these experiments are summarized as follows.

1) Current density

Current density acted as a very important parameter in the present invention. The most appropriate current density for dyeing wastewater treatment and 0.1 to 0.2 A / cm ² is suitable, we could get a universally good results in 0.1 ~ 0.15A / cm ² in a double. When the current density is too low, it takes a long time, and when the concentration of wastewater is high, electrolysis is not good. On the contrary, when the current density is above the above range, the electrolysis efficiency is increased, but it causes rapid corrosion and consumption of the electrode plate, and the ppm does not drop to some extent even after the filtration, and the color of the water after filtration is red. . Two euros showing a red color is iron ^2+, ions to be considered as 3 ⁺ are that through the Fe (OH) ₃ and present in excess after the Fe ₂ (OH) ₃ due to a high current density to be Fe ₂ O ₃ dysplastic Shown. These experiments were able to find the proper current density through many experiments, and when the experiment was conducted at the proper current density, turbidity can be obtained as clean water as tap water.

2) electrolysis time

Electrolysis time is also a very important experimental factor. Electrolysis time is closely related to current density and is inversely related to each other. Appropriate electrolysis time was found to be about 20-30 minutes in total. This time is also related to the dyeing wastewater, which is sufficient for 15 ~ 20 minutes when the concentration of wastewater is below 400ppm ~ 500ppm, but it is necessary to give enough time above 500ppm.

3) Distance between electrodes

The distance between electrodes influences the current density, but the effect is not so large.

When determining the distance between electrodes, the proper distance between electrodes is just 7 ~ 15cm based on 100ℓ considering the bath size and the amount of waste water. Below this, there is a risk of leakage and difficulty in alternating by sparks. Its resistance has a large effect on power consumption and has a great effect on the removal rate.

4) electrolyte

The amount of electrolyte varies depending on the amount of wastewater. The amount of electrolyte added was about 3-5% when the amount of wastewater was less than 10 liters, and less than 1% at 50-200 liters.

The electrolyte has a good current flow and a low voltage. However, the electrolyte is required to be added in an excessive amount because excessive concentration of the electrolyte causes severe corrosion of the electrode plate and high concentration of Cl even after filtration.

5) Material of pole plate

According to various documents, Al, SUS, etc. are used for the positive electrode, but in the present invention, a high removal rate can be obtained when iron is used for the positive electrode and the negative electrode.

6) Filtration method

In the experiments, decompression filtration was performed, but in the mini pilot, it is expected that the use of flotation and sedimentation will allow for a smooth and rapid filtering. After the electrolysis, the scums all come to mind. By using this principle, a pipe is placed at the bottom of the bath, where only clean water can be separated.

The use of sedimentation takes some time and the scum that has been injured must sink, in which case the pipe must be installed on top, and the former is more practical and convenient than the latter. However, if the scale is to be performed in the field, more automated filtration system is required.

7) stirring

Agitation is also one of the most important factors. As a result of experiments with agitation to confirm the efficiency of agitation, it can be observed that electrolysis does not occur at all. There were also many differences in agitation and propagation experiments using propellers, and aeration agitation was more powerful than propeller agitation, and it was found to have a large effect on scum injury.

8) Ozone Treatment

The role of ozone treatment was to remove about 85% of COD by electrolysis after electrolysis, and to remove the remaining 5-10%. Ozone treatment was very good in color and turbidity, and the removal rate was about 5-10%. To increase the removal rate due to ozone treatment, it is effective to use an ozone having a high ozone production amount.

As described above, the wastewater treatment method of the present invention has the advantage that the treatment area can be reduced by half, and the continuous operation is possible, and the treatment time is 50% shorter than that of the chemical treatment, compared to the biological treatment method. In addition, secondary contamination by treatment reagents can be avoided, sludge production can be minimized compared to chemical treatment, and the operating conditions of the treatment equipment can be changed because the treatment conditions can be easily changed by simple current density adjustment according to the operating mechanism. Compared to the treatment method, it is simple and easy to automate. In addition, the present invention can be easily treated under conditions of normal temperature and atmospheric pressure and can be effectively treated regardless of the season, and does not require a separate process such as adjustment of pH or administration of auxiliary additives.

Claims (4)

A pair of electrodes consisting of a DC power supply and a pair of electrodes consisting of Fe or Al are spaced apart from each other by a distance of 7 to 15 cm based on 100 liters of wastewater, and an electrolyte concentration of 0.1 to Introducing the dyeing waste water added 1.0% electrolyte if the waste water amount is less than 10l 3 ~ 5% of the waste water amount, if the waste water amount is 50 ~ 200l less than 1% of the waste water amount; The dyeing wastewater by the metal ion, hydrogen and oxygen generated by the electrolysis by applying a current density of 0.1 ~ 0.15A / cm ² to the electrode for 20 to 30 minutes in proportion to the concentration (ppm) of the wastewater Flocculating, adsorbing, sedimenting, flocculating contaminants therein; Filtering the electrolyzed dyed wastewater to remove scum and ozone treatment; dyeing treatment method comprising a. The method of claim 1, And treating the polarity of the DC power applied to the pair of electrodes alternately every predetermined time. The method of claim 1, The stirring device is a treatment method for dyeing wastewater, characterized in that the aeration agitator. The method of claim 1, And said electrode is a plurality of electrode pairs.