JP2012024729A - Plating wastewater treatment method using microbubble, and chemical liquid for plating wastewater treatment used for the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for collecting and removing the floating suspended substances comprising heavy metals such as zinc at high efficiency when separating such substances from the water to be treated using microbubbles to remove in treatment of wastewater discharged from a plating facility.SOLUTION: The method includes blending, in the water to be treated: a collecting agent comprising amines having 8-14C alkyl or the salts thereof, or sulfuric ester of 8-14C higher alcohol or the salt thereof; a collection auxiliary agent comprising the hydroxide salt or acid of alkali metals or alkaline-earth metals; and a foaming agent comprising ≤8C lower alcohols or ≤8C lower ketones.

Description

  The present invention relates to a treatment method for removing environmentally regulated substances contained in plating wastewater discharged from establishments related to plating, and in particular, heavy metals such as zinc, iron, chromium, nickel, lead and the like using microbubbles and their The present invention relates to a plating wastewater treatment method for separating and removing suspended suspended matter having a size of several tens of μm or less from a water to be treated, and a chemical solution for plating wastewater treatment used in the treatment method.

  Conventionally, heavy metals such as zinc, iron, chromium, nickel, lead, etc. contained in the wastewater discharged from plating-related establishments have been removed by using hydroxides and sulfides. An alkali coagulation precipitation method or a sulfide coagulation precipitation method has been used in which a flocculant is used instead of a flocculant instead of a product to cause precipitation. In these coagulation sedimentation methods, the supernatant water from which the coagulation sediment has been separated is filtered and then discharged. However, there is a problem of the outflow of fine particles due to insufficient performance or failure of the filtration device, particle miniaturization, etc. On the other hand, in recent years, there is a tendency that emission standards such as zinc are reinforced and the conventional coagulation precipitation method is used. A situation that cannot be handled by processing alone has appeared. For this reason, in the plating industry, a new treatment technique for further reducing the concentration of heavy metals such as zinc and chromium in the effluent is demanded.

  By the way, as a technique for removing suspended substances in wastewater, a wastewater treatment method using microbubbles by applying a flotation method (flotation method) has been proposed. In this wastewater treatment technology, microbubble-containing water produced in a micro (nano) bubble generation tank is mixed with wastewater, and then the wastewater containing microbubbles is introduced into a pressurized flotation tank so that the microbubbles It is attached to fine suspended matter, and the suspended matter to which the microbubbles are attached is floated and separated from the waste water. And in order to improve the generation efficiency of the microbubble in a microbubble generation tank, surfactant is added to a microbubble generation tank as a microbubble generation aid (for example, refer patent documents 1 and 2).

JP 2009-34683 A (page 5, page 9, FIG. 4) JP 2008-36518 A (Page 5, Pages 9-10, FIG. 4)

  Patent Documents 1 and 2 disclose a method of treating waste water using microbubbles. However, when microbubbles are to be used for the treatment of wastewater discharged from plating-related business establishments, simply bringing the water to be treated and microbubbles into contact with each other in the treatment tank makes it possible to float in the wastewater. Suspended material cannot be separated and removed with high efficiency. Patent Documents 1 and 2 describe that a surfactant is added to the waste water as a microbubble generation aid, but the surfactant is added to improve the generation efficiency of microbubbles. Thus, it does not directly increase the effect of collecting suspended suspended solids.

  The present invention has been made in view of the circumstances as described above, and in processing wastewater discharged from plating related establishments, zinc, iron, chromium, nickel, lead, etc. contained in the water to be treated When microbubbles are used to separate and remove suspended solids consisting of heavy metals and their compounds from treated water, suspended suspended solids in treated water are collected and removed with high efficiency. An object of the present invention is to provide a plating wastewater treatment method that can be used, and to provide a plating wastewater treatment chemical that is preferably used in the treatment method.

  According to the first aspect of the present invention, the water to be treated is brought into contact with the microbubbles in the treatment tank, the suspended suspended solids in the treated water are attached to the microbubbles, and the suspended suspended solids are separated from the treated water. In the plating wastewater treatment method using microbubbles, the wastewater after treatment is discharged from the top of the treatment tank and discharged from the bottom of the treatment tank. A collection aid comprising an alkaline earth metal hydroxide salt or acid and a foaming agent comprising a lower alcohol having 8 or less carbon atoms or a lower ketone having 8 or less carbon atoms are mixed with the water to be treated, and As a collecting agent, an amine having an alkyl group having 8 to 14 carbon atoms or a salt thereof, or a sulfate ester of a higher alcohol having 8 to 14 carbon atoms or a salt thereof is used. When the carbon number of the alkyl group of alkylamine or alkylsulfuric acid ester is smaller than 8, hydrophobicity becomes weak and adhesion to microbubbles becomes insufficient. On the other hand, when the number of carbon atoms in the alkyl group of alkylamine or alkylsulfate is greater than 14, it becomes difficult to handle due to low solubility in water.

The above-described collection agent has the role of (i) increasing the probability of attachment of suspended suspended matter to microbubbles by adsorbing to suspended suspended matter in the treated water and making the particle surface hydrophobic. In addition, (b) the oily dirt is removed together with the suspended suspended solids by adsorbing the oily dirt in the treated water and adhering to the suspended suspended solids. Easy to form aggregates required for rapid separation by lowering the surface potential by adsorbing to suspended suspended solids and oily dirt in water and lowering the electric repulsion between particles, Have the role.
The above-mentioned collection assistant adsorbs to suspended suspended solids in the water to be treated and promotes adsorption of the collected agent to suspended suspended solids, thereby improving the removal rate of metal compounds intended for treatment. Have the role of Further, the foaming agent described above has a role of helping to generate microbubbles in the water to be treated and to stably form a foam layer of microbubbles necessary for separating and removing the metal compound.

  The invention according to claim 2 is the plating wastewater treatment method according to claim 1, wherein the collection agent is 0.0001 w / v% to 1 w / v% in the water to be treated stored in the treatment tank. It is contained at a concentration, and the collection aid and the foaming agent are mixed so as to be contained at a concentration of 1 w / v% or less. When the concentration of the collection agent is lower than 0.0001 w / v%, the adhesion force to the microbubbles becomes insufficient, and the collection power of the suspended suspended matter by the microbubbles decreases. On the other hand, if the concentration of the collection agent is higher than 1 w / v%, the collection agent is stabilized by forming micelles, and in this case also, the collection power of the suspended suspended matter is reduced.

  The invention according to claim 3 is the plating wastewater treatment method according to claim 2, wherein n-dodecylamine hydrochloride is used as the collection agent, sodium hydroxide is used as the collection aid, Ethanol is used as a foaming agent.

  The invention according to claim 4 is the plating wastewater treatment method according to claim 2, wherein sodium n-dodecyl sulfate is used as the collection agent, sodium hydroxide is used as the collection aid, and the foaming Ethanol is used as the agent.

  In the invention according to claim 5, the water to be treated is brought into contact with the microbubbles, the suspended suspended solids in the treated water are attached to the microbubbles and floated, and the suspended suspended solids are separated from the treated water and removed. The plating wastewater treatment chemical used for discharging to the water is an amine having an alkyl group having 8 to 14 carbon atoms or a salt thereof, or a higher alcohol sulfate having 8 to 14 carbon atoms or a salt thereof. An agent, a collection aid comprising an alkali metal or alkaline earth metal hydroxide salt or acid, and a foaming agent comprising a lower alcohol having 8 or less carbon atoms or a lower ketone having 8 or less carbon atoms. It was prepared.

  The invention which concerns on Claim 6 WHEREIN: In the chemical | medical solution for plating waste water treatment of Claim 5, the mixing ratio of the said collection aid with respect to the said collection agent and the said foaming agent is 1 or less in weight ratio, respectively. Features.

  The invention according to claim 7 is the chemical solution for plating waste water treatment according to claim 6, wherein the collection agent is n-dodecylamine, the collection aid is sodium hydroxide, and the foaming agent is It is characterized by being ethanol.

  The invention according to claim 8 is the chemical solution for plating waste water treatment according to claim 6, wherein the collection agent is sodium n-dodecyl sulfate, the collection aid is sodium hydroxide, and the foaming agent. Is ethanol.

  According to the plating wastewater treatment method of the invention according to claim 1, it is contained in water to be treated, such as wastewater obtained by neutralizing plating wastewater discharged from plating-related establishments with an alkali agent, and wastewater obtained by further coagulating and precipitating it. Suspended suspended substances consisting of heavy metals and their compounds can be efficiently removed from the water to be treated using microbubbles. And in this processing method, even if the oily dirt discharged in the plating process is mixed in the water to be treated, the effect of removing suspended suspended solids is not changed, and the oily dirt mixed in the water to be treated is also removed at the same time. Therefore, the concentration of BOD (biochemical oxygen demand) or COD (chemical oxygen demand) and organic suspended solids in the treated water (discharged water) can also be reduced. As described above, according to this plating wastewater treatment method, it is possible to discharge a lot of environmentally regulated substances to a concentration lower than the regulated value. In addition, it is no longer necessary to install a filtration device that was used to filter fine particles (floating suspended solids) in the conventional wastewater treatment method that only uses the coagulation sedimentation method. Troublesome maintenance work such as replacement is not required. In addition, when wastewater that has been neutralized with alkaline agent is used as plating wastewater discharged from plating-related establishments, there is no need for flocculant treatment or precipitation (sedimentation) operations. Moreover, the equipment for that is unnecessary.

  In the plating wastewater treatment method according to each of the inventions according to claims 2 to 4, the above-described effect of the invention according to claim 1 can be obtained with certainty.

  When the plating wastewater treatment method using microbubbles using the chemical solution for plating wastewater treatment of the invention according to claim 5 is carried out, wastewater obtained by neutralizing the plating wastewater discharged from the plating-related establishments with an alkaline agent or the like The suspended suspended material consisting of heavy metals and their compounds contained in the water to be treated such as wastewater that has been further coagulated and precipitated can be efficiently removed from the water to be treated using microbubbles.

  When the chemical solution for plating waste water treatment of each invention according to claims 6 to 8 is used, the above-described effect of the invention according to claim 5 can be obtained with certainty.

It is a schematic block diagram of the apparatus used for the experiment for confirming the effect by the plating waste water treatment method concerning this invention. It is a graph which shows the result of above-mentioned experiment, Comprising: The relationship between the molar concentration of n-dodecylamine hydrochloride used as a collection agent and the residual concentration of various heavy metals is shown. It is a graph which shows the result of 2nd experiment, Comprising: The relationship between the molar concentration of various alkylamine hydrochloride used as a collection agent, and the residual concentration of zinc is shown. It is a graph which shows the result of 3rd experiment, Comprising: The relationship between the molar concentration of sodium n-dodecyl sulfate used as a collection agent and the residual concentration of various heavy metals is shown. It is a graph which shows the result of 4th experiment, Comprising: The relationship between the molar concentration of two types of sodium alkyl sulfate used as a collection agent, and the residual concentration of zinc is shown. It is the schematic which shows one example of the apparatus structure used in order to implement the plating waste water treatment method concerning this invention.

The best mode of the present invention will be described below.
The water to be treated in the wastewater treatment method according to the present invention is a plating wastewater discharged from a plating-related establishment, and the plating wastewater is neutralized with an alkaline agent to produce zinc, iron, and chromium. Waste water after particles of heavy metals are agglomerated by changing heavy metal ions such as nickel and lead into hydroxides or treating plating wastewater with sodium sulfide to convert heavy metal ions into metal sulfides Waste water after flocking with an agent to form a precipitate, or supernatant water after agglomerated precipitate is settled and separated from the waste water. Moreover, depending on the case, the current discharge water after filtering the supernatant water after sedimentation of the aggregated sediment may be used as treated water. In this wastewater treatment method, the suspended water having a size of several tens of μm or less of heavy metals such as zinc and its compounds in the treated water is contacted with the microbubbles in the treatment tank. It floats by adhering to the bubble, and the suspended suspended solids are separated and removed from the water to be treated.

  What is necessary is just to use what is marketed as a microbubble generator which generates a microbubble in to-be-processed water. A microbubble is generally a fine bubble having a diameter of 1 μm to several tens of μm. Here, an ultrafine bubble (nanobubble) having a diameter of several hundred nm or less due to a contraction movement after the generation of the microbubble. Also, what is contained is called microbubbles.

In this wastewater treatment method, a chemical solution prepared by mixing a collection agent, a collection aid, and a foaming agent is used, and the chemical solution is mixed with water to be treated.
The collection agent is added to the water to be treated for the purpose of adsorbing to the suspended solids in the treated water to make the particle surface hydrophobic and increasing the adhesion probability of the suspended suspended material to the microbubbles. In addition, by adding a collection agent to the water to be treated, it is adsorbed to the oily dirt that has become oil droplets in the water to be treated, causing the oily dirt to adhere to the suspended solids, and the oily dirt together with the suspended suspended substances. Remove or adsorb to suspended suspended solids and oily dirt in treated water to lower the surface potential and reduce the electric repulsive force between particles, forming aggregates required for rapid separation The role of making it easy. As such a collector, an amine having an alkyl group having 8 to 14 carbon atoms (C _n H _{2n + 1} −, n = 8 to 14) or a neutralized salt thereof with an acid is used. The alkyl group is not limited to a linear structure. The amine is not limited to a primary amine but may be a secondary amine, a tertiary amine, or a quaternary ammonium. The salt is hydrochloride, acetate, nitrate or sulfate. Specifically, cationic surfactants such as n-octylamine hydrochloride, n-nonylamine hydrochloride, n-decylamine hydrochloride, n-dodecylamine hydrochloride, n-tridecylamine hydrochloride, n-tetra Decylamine hydrochloride or the like is used as a collector. Alternatively, a higher alcohol sulfate (alkyl sulfate) or a salt thereof having 8 to 14 carbon atoms is used as a collector. Specifically, sodium dodecyl sulfate, which is an anionic surfactant, is used as a collector. The amount of the collection agent added is set so that the concentration in the water to be treated is, for example, 0.0001 w / v% to 1 w / v%.

  The collection aid is added to the water to be treated for the purpose of adsorbing on the suspended solid in the water to be treated and promoting the adsorption of the collecting agent to the suspended solid. Such a collection aid is made of an alkali metal or alkaline earth metal hydroxide salt or acid, and the pH of the water to be treated is adjusted by addition to the water to be treated. Specifically, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide and the like are used as a collection aid, and hydrochloric acid, sulfuric acid, nitric acid and the like are used as a collection aid. The foaming agent is added to the water to be treated for the purpose of helping to generate microbubbles in the water to be treated and stably forming a foam layer of microbubbles. As such a foaming agent, a lower alcohol having 8 or less carbon atoms or a lower ketone having 8 or less carbon atoms is used. Specifically, methanol, ethanol, propanol, butanol and the like are used as the foaming agent, and methyl isobutyl ketone, methyl isobutyl carbinol and the like are used as the foaming agent. Each addition amount of the collection aid and the foaming agent is set such that the concentration in the water to be treated is, for example, 1 w / v% or less. Moreover, each mixing ratio of the collection assistant and the foaming agent with respect to the collection agent is, for example, 1 or less in weight ratio.

Next, an experiment for confirming the effect when the wastewater treatment method according to the present invention is carried out and the result of the experiment will be described.
As the waste water sample, second pH adjusted water (hereinafter referred to as “neutralized raw water”) obtained by neutralizing the plating waste water discharged from the plating establishment with an alkali agent (not coagulating and precipitating) was used. The zinc concentration in the drainage sample was about 100 ppm. In the experiment, as shown in FIG. 5 (pore size: 4 μm to 5.5 μm) glass filter plate 2 is attached and nitrogen gas is blown from the bottom of cylindrical container 1 so that fine bubbles (diameter: several μm) can be generated. An experimental apparatus provided with a side hole 3 for extracting treated water at the bottom of the cylindrical container 1 was used.

The first experiment was performed as follows.
To 1000 ml of neutralized raw water, n-dodecylamine hydrochloride as a collecting agent is added to various concentrations, and 2 ml of ethanol is added as a foaming agent (ethanol concentration: 0.2%), and further collection aid After adding sodium hydroxide as an agent, the neutralized raw water was aged by stirring for 5 minutes. At this time, the pH of the neutralized raw water was adjusted to 7.6-8.4 by adding sodium hydroxide. 1000 ml of this neutralized raw water was poured into the cylindrical container 1, and nitrogen gas was blown into the cylindrical container 1 from the bottom of the cylindrical container 1 at a flow rate of 30 ml / min. Thereby, microbubbles were generated in the neutralized raw water, and the neutralized raw water in the cylindrical container 1 became cloudy. Then, the precipitated particles (floating suspended solids) were floated up to the water surface by the microbubbles, and a liquid layer in which the precipitated particles were condensed was formed near the water surface. Ten minutes after the start of the treatment, the treated water is extracted from the side hole 3 at the bottom of the cylindrical container 1, and zinc (Zn), iron (Fe), chromium (Cr), nickel (Ni), copper ( Each concentration of Cu) and manganese (Mn) was analyzed.

Analysis of residual zinc concentration and the like was performed as follows in accordance with JIS K 0102.
Collect 50 ml of sample water from the treated water, add 2.5 ml of nitric acid to the sample water, concentrate this solution to about 10 ml, and then add 0.5 ml of internal standard (yttrium: 1000 ppm) to the concentrate. Then, the volume up to 50 ml was used for analysis. The analysis was performed by an internal standard method using an inductively coupled plasma optical emission spectrometer (ICAP-55: manufactured by Nippon Jarrell-Ash Co., Ltd.).

  FIG. 2 is a graph showing the results of the experiment, and shows the relationship between the molar concentration (mmol / l) of n-dodecylamine hydrochloride used as a collector and the residual concentration of various heavy metals, The upper graph represents the concentration on the vertical axis with a scale of 0-100 ppm, and the lower graph represents the concentration on the vertical axis with a scale of 0-10 ppm. The molar mass of n-dodecylamine hydrochloride is 221.81 g / mol.

  From the experimental results shown in FIG. 2, the environment for all heavy metals to be analyzed is obtained by adding the appropriate amount of collection agent, collection aid and foaming agent to neutralized raw water and performing floating selection with microbubbles. It was found that the purification treatment can be performed to a concentration that is not more than the regulation value, for example, 2 ppm or less. Further, if the concentration of the collection agent is within the range of 0.0001% to 1%, heavy metals can be removed well from the neutralized raw water, but even if the concentration falls below the lower limit, the upper limit is exceeded. It has been found that it is difficult to remove heavy metals up to a concentration that is below the environmental regulation value in such a concentration region.

In addition, a second experiment conducted by changing the number of carbon atoms of the alkyl group of the alkylamine in various ways will be described.
In the second experiment, n-octylamine hydrochloride (C ₈ H ₁₇ NH ₂ .HCl: C ₈ ), n-decylamine hydrochloride (C ₁₀ H ₂₁ NH ₂ .HCl: C ₁₀ ), n -Dodecylamine hydrochloride (C ₁₂ H ₂₅ NH ₂ .HCl: C ₁₂ ) and n-tetradecylamine hydrochloride (C ₁₄ H ₂₉ NH ₂ .HCl: C ₁₄ ), respectively, and concentration analysis Only for zinc remaining in the treated water. Other experimental methods and concentration analysis methods are the same as in the first experiment described above.

  FIG. 3 is a graph showing the results of the second experiment, showing the relationship between the molar concentration (mmol / l) of various alkylamine hydrochlorides used as a collector and the residual concentration of zinc. The upper graph represents the concentration on the vertical axis on a scale of 0-100 ppm, and the lower graph represents the concentration on the vertical axis on a scale of 0-10 ppm. Based on the results of this experiment, a suitable amount of collector, collection aid and foaming agent was added to the neutralized raw water and the carbon number of the alkyl group of the alkylamine as the collector was changed to perform floating selection with microbubbles. At that time, it was found that any of the alkylamine hydrochlorides studied can reduce the concentration of residual zinc so that it is below the environmental regulation value (2 ppm or less). And when it looked at molar concentration, it turned out that there exists a removal effect of zinc in a low concentration area | region, so that carbon number of the alkyl group of alkylamine increases. In addition, it is difficult to remove zinc to a concentration that is below the environmental regulation value whether the concentration of the collector is below the lower limit of 0.0001% to 1% or exceeds the upper limit. I understood.

Next, a third experiment conducted by changing the collection agent to an alkyl sulfate ester will be described.
In the third experiment, sodium n-dodecyl sulfate as a collection agent was added to 1000 ml of neutralized raw water so as to have various concentrations, and 2 ml of ethanol was added as a foaming agent (ethanol concentration: 0.2%). Furthermore, after adding sodium hydroxide as a collection aid so that the pH of the neutralized raw water was 8.5, the neutralized raw water was aged by stirring for 5 minutes. The subsequent operation and concentration analysis method are the same as in the first experiment described above.

  FIG. 4 is a graph showing the results of the third experiment, showing the relationship between the molar concentration (mmol / l) of sodium n-dodecyl sulfate used as a collector and the residual concentrations of various heavy metals. Yes, the upper graph represents the concentration on the vertical axis on a scale of 0-70 ppm, and the lower graph represents the concentration on the vertical axis on a scale of 0-10 ppm. In addition, the molar mass of sodium n-dodecyl sulfate is 288.38 g / mol.

  From the experimental results shown in FIG. 4, an alkyl sulfate ester is used as a collection agent, and together with the collection agent, an appropriate amount of a collection aid and a foaming agent are added to the neutralized raw water, and floating selection is performed with microbubbles. Thus, it was found that all heavy metals to be analyzed can be purified to a concentration that is below the environmental regulation value, for example, 2 ppm or less. In addition, it is difficult to remove heavy metals to a concentration that is below the environmental regulation value whether the concentration of the collector is below the lower limit of 0.0001% to 1% or exceeds the upper limit. I found out.

Further, a fourth experiment conducted by changing the number of carbon atoms of the alkyl sulfate alkyl ester will be described.
In the fourth experiment, sodium n-dodecyl sulfate (C ₁₂ H ₂₅ OSO ₃ Na: C ₁₂ ) and sodium n-tetradecyl sulfate (C ₁₄ H ₂₉ OSO ₃ Na: C ₁₄ ) were used as collection agents, Concentration analysis was performed only for zinc remaining in the treated water. Other experimental methods and concentration analysis methods are the same as in the third experiment described above.

  FIG. 5 is a graph showing the results of the fourth experiment, showing the relationship between the molar concentration (mmol / l) of the two types of sodium alkyl sulfate used as the collector and the residual concentration of zinc. Yes, the upper graph represents the concentration on the vertical axis on a scale of 0-70 ppm, and the lower graph represents the concentration on the vertical axis on a scale of 0-10 ppm. Based on the results of this experiment, a suitable amount of a collection agent, collection aid and foaming agent was added to the neutralized raw water, and the carbon number of the alkyl group of the alkyl sulfate ester, which is the collection agent, was changed to perform floating selection with microbubbles. It was found that the concentration of residual zinc can be reduced to be below the environmental regulation value (2 ppm or less) by any of the two types of alkyl sulfates studied. And when it looked at molar concentration, it turned out that the one where the carbon number of the alkyl group of the alkyl sulfate ester is larger has the effect of removing zinc in a lower concentration region. In addition, it is difficult to remove zinc to a concentration that is below the environmental regulation value whether the concentration of the collector is below the lower limit of 0.0001% to 1% or exceeds the upper limit. I understood.

In the experiment described above, the wastewater sample was batch-treated, but in the actual plating wastewater treatment, the wastewater is continuously treated. FIG. 6 schematically shows an example of an apparatus configuration for performing continuous processing.
The plating waste water treatment apparatus includes a treatment tank 10 having a double wall structure. The processing tank 10 includes a cylindrical outer tank 12 erected in the vertical direction, a cylindrical inner tank 14 disposed inside the outer tank 12 so as to extend from the vicinity of the bottom thereof to the middle thereof, and A waste water receiving tank 16 is attached to the upper outer wall of the outer tub 12 so as to surround the upper part, and a discharge passage for treated water is provided between the inner peripheral surface of the outer tub 12 and the outer peripheral surface of the inner tub 14. 18 is formed. A siphon type level pipe 20 is connected in communication with the bottom of the processing tank 10, and treated water having a flow rate corresponding to the flow rate of the water to be treated flowing into the processing tank 10 passes through the siphon type level pipe 20. It is configured to be discharged. Further, a scraping machine for scraping out to the waste liquid receiving tank 16 a liquid layer in which precipitated sludge, that is, suspended particles suspended to the vicinity of the water surface by microbubbles, is condensed on the upper part of the treatment tank 10. 22 is installed. In the vicinity of the bottom of the inner tank 14 of the treatment tank 10, an inlet 24 for water to be treated is provided, and a supply pipe 26 for water to be treated is connected to the inlet 24.

  The plating wastewater treatment apparatus is also provided with a chemical solution mixing tank 28. The chemical solution mixing tank 28 is connected to a feed pipe 30 of water to be treated, for example, neutralized raw water, and the neutralized raw water after neutralizing the plating wastewater discharged from the plating establishment with a neutralizing agent. It is fed into the chemical liquid mixing tank 28 through the liquid feeding pipe 30. Further, a chemical liquid tank 32 is attached to the chemical liquid mixing tank 28. In the chemical liquid tank 32, a collector such as n-dodecylamine hydrochloride and sodium n-dodecyl sulfate, a collection aid such as sodium hydroxide, and a foaming agent such as ethanol are mixed at a predetermined ratio. The plated plating wastewater treatment chemical 34 is stored. The chemical liquid 34 is poured from the chemical liquid tank 32 through the chemical liquid supply pipe 36 into the chemical liquid mixing tank 28, and the chemical liquid 34 is mixed with the neutralized raw water 38 in the chemical liquid mixing tank 28. The chemical liquid mixing tank 28 is provided with a stirrer 40, and the neutralized raw water 38 is stirred by the stirrer 40.

  The neutralized raw water 38 once stored in the chemical liquid mixing tank 28 and mixed with the chemical liquid 34 is fed to the processing tank 10 through the supply pipe 26. A liquid feed pump 42, a flow rate adjusting valve 44, and a flow meter 46 are inserted in the supply pipe 26. Further, a liquid circulation pipe 48 branched from the middle of the siphon type level pipe 20 is connected to the supply pipe 26 in communication. The liquid circulation pipe 48 is provided with a circulation pump 50 and an air blowing type microbubble generator 52, and an air pipe 54 connected to the compressed air supply source is connected to the microbubble generator 52. It is connected. Then, a part of the treated water discharged from the treatment tank 10 through the level pipe 20 flows into the liquid circulation pipe 48 and is mixed with the pressurized air while passing through the microbubble generator 52 to be microbubbles. The contained water is generated, and the microbubble-containing water merges with the neutralized raw water fed to the treatment tank 10 through the supply pipe 26 so that the neutralized raw water containing the microbubbles flows into the treatment tank 10. It is configured.

  In the apparatus having the configuration shown in FIG. 6, neutralized raw water containing microbubbles is continuously supplied into the treatment tank 10. In the processing tank 10, a liquid flows from the bottom of the inner tank 14 toward the upper part and reverses at the upper end of the inner tank 14, enters the discharge passage 18, and flows downward in the discharge passage 18. Then, treated water having a flow rate corresponding to the flow rate of the neutralized raw water supplied into the treatment tank 10 is discharged from the treatment tank 10 through the siphon type level pipe 20. While the neutralized raw water that has flowed into the treatment tank 10 flows upward in the inner tank 10, suspended suspended solids in the neutralized raw water adhere to the microbubbles and rise. Then, the suspended suspended matter adhering to the microbubbles is floated up to the upper end of the treatment tank 10, and a liquid layer (sludge layer) in which the suspended suspended matter is condensed is formed near the water surface. The condensate layer is scraped to the outside by the scraper 22 and is discharged into the waste liquid receiving tank 16 to be discharged and collected as a waste liquid containing heavy metals such as zinc. On the other hand, the treated water from which heavy metals have been separated and removed flows downward in the discharge passage 18 and flows out of the treatment tank 10, and is discharged as discharge water through the siphon type level pipe 20. The part circulates through the liquid circulation pipe 48.

  By performing the wastewater treatment of the neutralized raw water using the apparatus configured as shown in FIG. 6, the concentration of zinc, its compound, chromium and its compound in the treated water is reduced to a concentration below the environmental regulation value such as 2 ppm. It is also possible to obtain treated water in which cadmium and its compounds, lead and its compounds, copper and its compounds, iron and its compounds, nickel and its compounds, etc. are reduced to a concentration below the environmental regulation value. It becomes possible. And the removal effect does not change even if the fat and oil stains discharged in the plating process are mixed in the water to be treated, and the fat and oil stains mixed in the water to be treated can be removed at the same time. For this reason, it becomes possible to reduce the concentration of BOD or COD in the treated water and the suspended suspended matter of the organic matter to a concentration of, for example, 600 ppm or less and discharge it.

  The plating wastewater treatment method according to the present invention is applied to remove environmentally regulated substances in plating wastewater at plating-related establishments, and is useful for water pollution prevention and environmental conservation. This can contribute to the reduction of environmental pollution countermeasure costs and maintenance work.

DESCRIPTION OF SYMBOLS 10 Treatment tank 12 Outer tank of treatment tank 14 Inner tank of treatment tank 16 Waste liquid receiving tank 18 Discharge passage of treated water 20 Siphon type level pipe 26 Supply pipe of treated water 28 Chemical liquid mixing tank 30 Treated water (neutralized raw water) Liquid feed pipe 32 Chemical liquid tank 34 Chemical liquid for plating wastewater treatment 36 Chemical liquid supply pipe 38 Neutralized raw water 42 Liquid feed pump 48 Liquid circulation pipe 50 Circulation pump 52 Micro bubble generator 54 Air pipe

Claims (8)

The treated water is brought into contact with the microbubbles in the treatment tank, the suspended suspended solids in the treated water are attached to the microbubbles and floated, and the suspended suspended solids are separated and removed from the treated water to remove the suspended suspension. In the plating wastewater treatment method using microbubbles, the wastewater after treatment is discharged from the bottom of the treatment tank,
An amine having an alkyl group having 8 to 14 carbon atoms or a salt thereof, or a collector comprising a sulfuric ester of a higher alcohol having 8 to 14 carbon atoms or a salt thereof, and an alkali metal or alkaline earth metal hydroxide salt Alternatively, a collecting aid comprising an acid and a foaming agent comprising a lower alcohol having 8 or less carbon atoms or a lower ketone having 8 or less carbon atoms are mixed with water to be treated, and plating using microbubbles Wastewater treatment method. The collection agent, the collection aid, and the foaming agent have concentrations of 0.0001 w / v% to 1 w / v%, 1 w / v% or less, respectively, in the water to be treated stored in the treatment tank. The plating wastewater treatment method using microbubbles according to claim 1, which is mixed so as to be 1 w / v% or less. The plating wastewater treatment method using microbubbles according to claim 2, wherein the collection agent is n-dodecylamine hydrochloride, the collection aid is sodium hydroxide, and the foaming agent is ethanol. . The plating wastewater treatment method using microbubbles according to claim 2, wherein the collection agent is sodium n-dodecyl sulfate, the collection aid is sodium hydroxide, and the foaming agent is ethanol. Used to bring the water to be treated into contact with the microbubbles, attach the suspended suspended solids in the treated water to the microbubbles, float up, separate the suspended suspended solids from the treated water, remove them, and discharge them outside the system A chemical for plating wastewater treatment,
A collector comprising an amine having an alkyl group having 8 to 14 carbon atoms or a salt thereof, or a sulfate ester of a higher alcohol having 8 to 14 carbon atoms or a salt thereof;
A collection aid comprising an alkali metal or alkaline earth metal hydroxide salt or acid;
A foaming agent comprising a lower alcohol having 8 or less carbon atoms or a lower ketone having 8 or less carbon atoms;
A chemical for plating wastewater treatment, characterized by being prepared by mixing. The chemical solution for plating waste water treatment according to claim 5, wherein a mixing ratio of the collection aid and the foaming agent to the collection agent is 1 or less by weight. The chemical solution for plating waste water treatment according to claim 6, wherein the collection agent is n-dodecylamine, the collection aid is sodium hydroxide, and the foaming agent is ethanol. The plating wastewater treatment chemical solution according to claim 6, wherein the collection agent is sodium n-dodecyl sulfate, the collection aid is sodium hydroxide, and the foaming agent is ethanol.

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