KR20160078793A - Treatment method of wastewater comprising phenol - Google Patents

Abstract

The present invention relates to a method for disposal of wastewater containing phenol, capable of effectively removing phenol and various pollutants, wherein the method comprises: an oxidative decomposition step of adding divalent ferrous salt and peroxide to wastewater containing phenol; a coagulative precipitation step of adjusting the pH of the resultant material of the oxidative decomposition step to 6.8-8.5; and a step of solid-liquid separating the resultant material of the coagulative precipitation step.

Description

TECHNICAL FIELD The present invention relates to a method for treating wastewater containing phenol,

The present invention relates to a method for treating wastewater containing phenol, and more particularly, to a method for effectively removing phenol and various contaminants from wastewater containing phenol and various contaminants, reusing final treated water, And more particularly to a method for treating a non-discharge type phenol waste water discharging only sludge.

As a treatment method of phenol wastewater, a method of adsorbing using activated carbon and a method of decomposing into a harmless substance through biological treatment are generally applied. However, in the case of the activated carbon treatment, the treatment of the phenol at high concentration limits the treatment efficiency and the excessive use amount of activated carbon. In the case of biological treatment, the treatment cost is relatively low. However, in the case of treatment of phenol wastewater in high concentration, the efficiency is somewhat ineffective, the treatment time is long, and the influence on the external environment is likely to act as a variable.

In the case of a treatment method using a membrane or a reverse osmosis membrane, it is known that various contaminants such as ion components, particulate substances, chromaticity, and chemical oxygen demand can be efficiently treated at the same time in addition to phenol, and the reuse of the treated water is effectively promoted . However, it is generally known that the reverse osmosis membrane has a disadvantage in that the treatment efficiency is somewhat low due to the hydrophilicity of phenol.

Also, in the case of the treatment method using vacuum evaporation, although the technique does not substantially generate the discharge water, it is not widely used because of cost problems due to energy use.

The present invention relates to a method for treating unsanitary phenol wastewater, which effectively removes phenol and various contaminants from wastewater containing phenol and various contaminants, reuses final treated water, and discharges solids in solid form only will be.

In this specification, an oxidative decomposition step of adding a dihydric metal salt and hydrogen peroxide to wastewater containing phenol; A flocculation and precipitation step comprising adjusting the pH of the resultant product of the oxidative decomposition step to 6.8 to 8.5; And solid-liquid separation of the resultant product of the flocculation and sedimentation step.

The present inventors have found that by adding the above-mentioned dihydric iron salt and hydrogen peroxide to the wastewater containing phenol and adjusting the pH of the resultant obtained by oxidative decomposition of phenol and the like by adjusting pH to 2.5 to 3.5 in order to increase the reaction efficiency, , It can be decomposed and treated with high efficiency. In this process, the separated solution can be recycled directly into industrial water, etc. Through experiments, it has been confirmed that only the solid slurry is discharged It is possible to provide an environmentally friendly wastewater treatment method of no-discharge type that does not carry out other purification treatment or the like.

The divalent iron ion (Fe ^{2 +} ) contained in the bivalent iron salt is oxidized to a ^trivalent iron ion (Fe ^{3 +} ) by hydrogen peroxide to generate an OH radical, and the OH radical decomposes organic matters such as phenol . Specific examples of the divalent iron salt include divalent iron sulfate and chloride.

The wastewater containing phenol may contain 5 mg / L to 2,000 mg / L of phenol. In addition, it means wastewater containing particulate matter, chemical oxygen demand and petroleum hydrocarbons, Is not greatly affected by the concentration range, and the treatment method can effectively treat even in the presence of phenol alone.

The method for treating wastewater containing phenol may further include a pretreatment step for removing oil or particulate matter contained in wastewater containing phenol using a floatation separator or an oil-water classifier before the oxidative decomposition step.

The wastewater containing phenol may contain particulate matter, chemical oxygen demand, petroleum hydrocarbons, and other components. The flotation apparatus or the oil separator may be used to remove the other components to improve the efficiency of the downstream process. .

The method for treating wastewater containing phenol may further include a step of adjusting the pH of the wastewater containing phenol to 2.5 to 3.5 before the oxidative decomposition step.

When the pH in the oxidative decomposition step in which the dihydric metal salt and hydrogen peroxide are added to the wastewater containing phenol is in a neutral region, self-decomposition reaction of hydrogen peroxide occurs, and the added dihydric iron salt reacts with water in water to form iron hydroxide precipitate The treatment efficiency may be lowered. Accordingly, the treatment method can adjust the pH of the wastewater containing phenol to 2.5 to 3.5. For controlling the pH of such wastewater, conventionally known inorganic acids may be used.

When the concentration of phenol in the wastewater containing phenol is high, for example, when the content of phenol is 800 mg / L or more, the concentration of hydrogen peroxide and bivalent iron is high, and the pH of the wastewater is 3 or less There may be no need for an additional pH adjustment process.

In the oxidative decomposition step, the concentration ratio of hydrogen peroxide to bivalent iron salt ion concentration may range from 0.7 to 1.3. If the weight ratio of the hydrogen peroxide to the divalent iron salt is too low, the oxidative decomposition reaction may be adversely affected, and the generation of sludge may be greatly increased, and the efficiency of the treatment of the wastewater containing phenol may be greatly reduced. Also, if the weight ratio of hydrogen peroxide to divalent iron salt is too high, the rate of decomposition of hydrogen peroxide may be slowed down and the reaction time may be prolonged. Otherwise, hydrogen peroxide remaining in the reaction is decomposed to release bubbles of oxygen, You can give.

In the oxidative decomposition step, the concentration ratio of phenol to hydrogen peroxide ranges from 0.8 to 1.2. If the concentration of the hydrogen peroxide is high, sludge may float in the sedimentation tank. If the concentration of the iron catalyst is appropriate, the reaction tank is brown.

In the oxidative decomposition step, 99% or more of the phenol can be removed. PH adjustment is then required for effective precipitation of the reaction product. At this time, the iron salt is precipitated in hydroxide form, and the optimum pH is maintained at 6.8 to 8.5 or 7.5 to 8.5.

The step of adjusting the pH of the product of the oxidative decomposition step to 6.8 to 8.5 may include adding alkali such as sodium hydroxide or calcium hydroxide to the resultant product of the oxidative decomposition step.

The coagulating and precipitating step may further include adding a polymer coagulant to the result of the oxidative decomposition step wherein the pH is adjusted to 6.8 to 8.5.

The polymer flocculant may be selected from among cationic polymer flocculants.

In the coagulation sedimentation step, a step of removing a part of the produced precipitate through a settling tank may be included. Through the removal process through the settling tank, the load on the micro filter on the downstream side is reduced, thereby enabling smooth operation of the downstream process.

Meanwhile, the method for treating wastewater containing phenol may further include a reverse osmosis step of filtering the solid-liquid separated product into a reverse osmosis membrane.

In addition, the method for treating wastewater containing phenol may further include a step of filtering the solid-liquid separated product using a microfilter before the reverse osmosis step. As described above, since the particulate matter present in the water is completely removed by using a microfilter (pore size of about 0.05 μm to 0.1 μm), the load on the downstream reverse osmosis membrane can be minimized.

Filtration of the resultant solid-liquid separated product into a reverse osmosis membrane comprises filtering the solid-liquid separated product into a desalination reverse osmosis membrane; And filtering the resultant filtered through the desiccant-containing reverse osmosis membrane with a reverse osmosis membrane for seawater.

In the reverse osmosis process, it is possible to produce water that can be fully reused by industrial water or the like by removing ion components, removing chemical oxygen demand, and removing residual phenol components. In this case, the removal efficiency of phenol is high (60 ~ 70%) through the reverse osmosis membrane. In order to improve the efficiency thereof, the phenol removal efficiency may be increased to a level of 80 to 90% or more when the alkaline component is added to the influent of the reverse osmosis membrane to raise the pH to 10.5 to 11.0. This may cause a slight difference depending on the characteristics of the wastewater to be treated. Through this process, 70 to 75% of the incoming wastewater can be reused as industrial water, and the amount of concentrated water generated is 25 to 30%.

Also, in the case of the concentrated water generated in the reverse osmosis process, since the amount of the total dissolved solids of the wastewater itself and the amount of the ion component added through the oxidative decomposition step and the concentrated water excluding the salt component are the same, .

Accordingly, when the reverse osmosis membrane is used in the reverse osmosis process, generally, when the total dissolved solids concentration is less than 7,000 mg / L, operation is possible but normal operation is impossible. In the case of concentrated water, the total dissolved solids are likely to be more than 10,000 mg / L. The reverse osmosis membrane for seawater can be applied to recover the industrial water production up to 85 ~ 95% through the combination of the reverse osmosis membrane for sea water and the reverse osmosis membrane for seawater at the recovery rate of 60 ~ 70%.

The method for treating wastewater containing phenol may further include evaporating and concentrating the result of the reverse osmosis step. The amount of wastewater discharged finally in the method of treating wastewater containing phenol is 5 to 15% of the number of contaminated wastewater, so that it is easy to apply the evaporation concentration process at a relatively low cost. Through the evaporation and concentration step, it becomes possible to constitute a treatment process in which water is not substantially discharged in the entire treatment process and only the solid content is discharged.

According to the present invention, there is provided a method for treating an unpurified phenol wastewater which effectively removes phenol and various pollutants from wastewater containing phenol and various pollutants, reuses final treated water, and discharges only sludge in a solid state do.

Further, the phenol wastewater treatment method effectively removes phenol and other contaminants from wastewater containing phenol (several ppm to several thousand ppm concentration) and other pollutants (ion component, chemical oxygen demand, petroleum hydrocarbon, etc.) Most of the water can be reused by industrial water.

The method of treating the no-discharge type phenol wastewater is more effective in treating phenol-contaminated water that may occur in the manufacturing process of producing magnesium by the Pigeon process.

The invention will be described in more detail in the following examples. However, the following examples are illustrative of the present invention, and the present invention is not limited by the following examples.

[ Example  1 to 6: Treatment of wastewater containing phenol at a high concentration]

Raw water containing phenol shown in Table 1 below was pretreated by using a flotation separator, hydrogen peroxide and FeSO ₄ .7H ₂ O were added thereto, and oxidation decomposition reaction was carried out.

After the oxidative decomposition reaction, the pH of the reaction product was adjusted as shown in Table 1 by using calcium hydroxide, cationic polymer flocculant was added, and the solution was transferred to a sedimentation tank for solid-liquid separation.

The resulting filtrate was filtered through a microfilter (pore size of about 0.1 um), and the filtrate was treated with a reverse osmosis membrane to remove additional phenol and other contaminants, The concentrated water from which phenol and other pollutants were removed was filtered again using a reverse osmosis membrane for seawater.

The composition of the filtered water filtered through the microfilter in Example 1 is shown by the RO number of water in Table 2 below. Concentration of the RO water obtained through the bale-bearing reverse osmosis membrane is shown by RO concentrated water in Table 2 below, The results of the treatment through RO membranes are shown in Table 2 below.

The concentrated water obtained from the seawater reverse osmosis membrane was concentrated by evaporation to separate only the solid sludge without discharging water. The concentration of phenol in the final product is as shown in Table 1 below.

Hydrogen peroxide
Addition amount
(mg / L) Divalent Iron Sulfate Addition Rate (mg / L) In the pH adjustment step
The added calcium hydroxide
(mg / L) Oxidative degradation
after
Adjusted pH The concentration of phenol in the final product
(mg / L) enemy 840.75 Example 1 5,000 1,000 8 7.87 0.250 Example 2 5,000 1,500 8 7.07 0.290 Example 3 6,500 1,000 9 7.11 0.225 Example 4 6,500 1,500 9 6.90 0.215 Example 5 8,000 1,000 9 7.00 0.190 Example 6 8,000 1,500 10.2 6.85 0.220

pH Phenols COD TOC Ca Fe Cl SO4 RO enemy 8.02 188.00 608 712.2 129.50 1.34 1869 2868 RO concentrated water 8.23 214.750 710 773.9 147.80 1.32 2169.6 3336 RO process number 7.38 1.435 5.4 5.845 0.012 <0.002 1.131 0.261 Removal rate (%) - 99.2 99.1 99.2 100 100 99.9 100

[ Example  7 to 15: Treatment of wastewater containing phenol in medium concentration]

As shown in the following Table 2, the phenol concentration of the raw water, the amount of the hydrogen peroxide, the amount of the sulfate of the bivalent iron, the pH of the raw water, and the pH adjusted after the oxidative decomposition were changed, And the wastewater containing medium-dense wastewater was treated to separate only the solid sludge without generating effluent water. The concentration of phenol in the final product is as shown in Table 1 below.

Raw phenol
density
(mg / L) Hydrogen peroxide
Addition amount
(mg / L) Divalent Iron Sulfate Addition Rate (mg / L) Enemy
PH
/ Adjusted pH Oxidative degradation
after
Adjusted pH The concentration of phenol in the final product
(mg / L) Example 7 300 1,015 302 7.45 / 2.97 7.31 7.45 Example 8 300 1,505 302 7.45 / 2.59 6.91 1.31 Example 9 300 2,030 302 7.45 / 2.89 6.90 0.39 Example 10 100 315 99 7.13 / 2.98 7.59 1.89 Example 11 100 490 99 7.13 / 2.97 6.94 0.33 Example 12 100 700 99 7.13 / 2.97 6.92 0.26 Example 13 50 105 38.5 6.98 / 2.91 6.98 10.39 Example 14 50 210 38.5 6.98 / 2.93 8.10 1.24 Example 15 50 315 38.5 6.98 / 2.91 6.97 0.33

As shown in Tables 1 to 3, in the above embodiments, phenol and various contaminants are removed at high efficiency from wastewater containing phenol and various contaminants, the final treated water is reused, and the final discharged material is a solid sludge Was released.

Claims (13)

An oxidative decomposition step of adding dihydric iron salt and hydrogen peroxide to wastewater containing phenol;
A flocculation and precipitation step comprising adjusting the pH of the resultant product of the oxidative decomposition step to 6.8 to 8.5; And
And subjecting the resultant of the flocculation and sedimentation step to solid-liquid separation
Process for treating wastewater containing phenol.
The method according to claim 1,
Wherein the wastewater containing phenol comprises from 5 mg / L to 2,000 mg / L of phenol,
Process for treating wastewater containing phenol.
The method according to claim 1,
Further comprising a pretreatment step for removing oil or particulate matter contained in wastewater containing phenol using a floatation separator or an oil sorter prior to the oxidative decomposition step,
Process for treating wastewater containing phenol.
The method according to claim 1,
Further comprising the step of adjusting the pH of the wastewater containing phenol to 2.5 to 3.5 prior to the oxidative decomposition step.
The method according to claim 1,
Wherein the hydrogen peroxide concentration is 0.7 to 1.3 relative to the divalent iron salt ion concentration in the oxidative decomposition step.
6. The method of claim 5,
Wherein the weight ratio of hydrogen peroxide to phenol in the oxidative decomposition step is from 0.8 to 1.2.
The method according to claim 1,
Wherein adjusting the pH of the result of the oxidative decomposition step to 6.8 to 8.5 comprises adding alkali to the result of the oxidative decomposition step.
Process for treating wastewater containing phenol.
The method according to claim 1,
Wherein the coagulation and precipitation step further comprises adding a polymer coagulant to the result of the oxidative decomposition step wherein the pH is adjusted to 6.8 to 8.5.
Process for treating wastewater containing phenol.
9. The method of claim 8,
Wherein the polymer flocculant comprises a cationic polymer flocculant.
The method according to claim 1,
And a reverse osmosis step of filtering the resultant solid-liquid separated product into a reverse osmosis membrane.
11. The method of claim 10,
Further comprising the step of filtering the solid-liquid separated product using a microfilter before the reverse osmosis step.
11. The method of claim 10,
And a reverse osmosis step of filtering the resultant solid-liquid separated product into a reverse osmosis membrane
Filtering the resultant solid-liquid separated product into a desiccant reverse osmosis membrane; And filtering the resultant filtered through the desiccant-containing reverse osmosis membrane with a reverse osmosis membrane for seawater.
Process for treating wastewater containing phenol.
11. The method of claim 10,
Further comprising the step of concentrating the resultant of the reverse osmosis step by evaporation.