JPS6117556B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating high COD (chemical oxygen demand) waste liquid, etc., and more specifically, to waste liquid or sludge that has a high concentration of COD and is difficult to remove. By applying a combination of mixing treatment using a combination of carbon agents and acidifying agents with different particle sizes, energization treatment, and coagulation sedimentation treatment, the waste liquid is separated into a supernatant liquid from which COD components have been removed and a flocculation floc of COD components. Regarding the method.

Pharmaceutical manufacturing factory wastewater, asphalt refinery factory wastewater, Metsuki wastewater, dye manufacturing factory wastewater, dyeing processing wastewater, paper and pulp factory black liquor, chemical factory wastewater, laboratory wastewater, sulfonic acid wastewater, textile synthesis wastewater, food processing wastewater, saccharification factory Wastewater, sugar manufacturing wastewater, starch wastewater, garbage washing wastewater, garbage incinerator ash cooling wastewater, petrochemical factory wastewater, photographic development wastewater, etc. have particularly high COD values.
It is difficult or almost impossible to remove this to a satisfactory level only by ordinary treatments such as activated sludge method, pressure flotation method, electrolytic method, etc.

BOD components, which are mainly composed of organic impurities, can be removed relatively easily by conventional methods, but complex chemical treatments such as redox, acidification/alkalinization, neutralization, and heating can also be used. The COD components in the waste liquid produced as a result of repeated processes are not of a nature that can be easily removed by those common water treatment technology steps.

Of course, there are cases in the laboratory where these COD components have been successfully removed to a satisfactory level, but these are economically and technically difficult to implement on a scale that deals with large volumes of waste liquid. is also extremely difficult and has not yet achieved commercial success.

The present inventor has previously demonstrated that by using particle size-adjusted pulverized coal for the treatment of various types of sludge or waste liquid, the solid content in these sludge or waste liquid can be coagulated and settled together with the pulverized coal, and the resulting coagulated sediment can be proposed that over-dehydration is easy, but
The objective of substantially completely removing COD components has not yet been fully satisfied.

As a result of extensive research aimed at completely removing COD components from high-COD waste liquid, the present inventors have found that particle size-adjusted pulverized coal, fine granule, etc. An operation of mixing carbon and an acidifying agent, an operation of applying an electric current to this suspension, and an operation of coagulating and precipitating the COD component through neutralization and addition of a polymer flocculant to this electric treatment liquid as necessary. When applying in combination,
It has been found that substantially all of the COD components in the waste liquid can be coagulated and precipitated.

That is, an object of the present invention is to provide a treatment method that can effectively separate high COD waste liquid and the like into clean water that does not substantially contain COD components and flocs of COD components.

Another object of the present invention is to rapidly separate not only the COD component but also the BOD component and other solid contents in the waste liquid as aggregates from the medium water, and furthermore, this aggregate can be separated very easily. The purpose of the present invention is to provide a new treatment method that can perform excessive dehydration.

Still another object of the present invention is to provide a waste liquid treatment method that allows COD components, etc. in waste liquid to be recovered as a cake with a low moisture content, and incinerated by utilizing the self-combustion power of the cake. .

According to the present invention, (a) particle size-adjusted pulverized coal containing 85% by weight or more of particles with a particle size of 9 to 500 mesh, (b) fine particulate carbon, and (c) an acidifying agent are added to high COD waste liquid. After mixing, the resulting mixed solution is treated with electricity in the presence of an electrolyte, and then this energized solution is neutralized and a polymer flocculant is added, followed by a supernatant liquid from which COD components have been substantially removed and COD. Provided is a method for treating high COD waste liquid, etc., which is characterized by separating the components into flocs and flocs.

The present invention can be widely applied to wastewaters that have a high concentration of COD and are difficult to remove, ie, the various industrial wastewaters mentioned above. Although these industrial wastewaters differ depending on the type, they generally contain more than 200 ppm, especially
Although it contains COD components reaching 1000 ppm or more, and in some cases BOD components and other solid contents, according to the treatment method of the present invention,
Not only the COD component but also the BOD component and other solids can be coagulated and precipitated.

The particle size-adjusted pulverized coal (MFC) used in the method of the present invention is composed of low-grade precipitated pulverized coal by-produced in the coal mining process, pulverized coal of young coals such as lignite, lignite, and peat. These are usually classified using a sieve, and 85% by weight or more of particles with a particle size of 9 to 500 mesh, especially those with a particle size of 16 to 325 mesh.
It is adjusted to be 85% by weight or more. Although high-grade bituminous coal whose particle size has been adjusted can be used, the above-mentioned relatively low-grade pulverized coal is advantageous industrially. In addition, low-grade coal that is classified as non-grade coal, such as one with a high ash content that has a calorific value of only 3500 Kcal/Kg to 5000 Kcal/Kg, can be advantageously used by adjusting the particle size to the above range. In short, the particle size is 9 to 500 mesh, preferably 16 to 325 mesh (1 m/
85% by weight of particles with a particle size of m ~ 0.04m/m)
or more, particularly preferably true specific gravity is 1.2
~1.6, any quality charcoal can be used as long as the ash content is in the range of 10 to 40%.

Furthermore, the fine particulate carbon as component (b) of the present invention has a particle size of
Fine particles of about 100 mμ or less, such as naphtha carbon or oil carbon, are suitable, but carbon as a by-product obtained by dry distillation activation of sludge is rather a pollutant or has low utility value. , even those that are inexpensive and easily available can be used to great advantage.

In the present invention, COD
In order to convert the components into a form that can be coagulated and precipitated together with the particle size-adjusted pulverized coal and the finely divided carbon, it is important to add the acidifying agent described in (c) above.

As such an acidifying agent, an inorganic flocculant that releases acid radicals by hydrolysis and can itself form aluminum hydroxide or aluminum hydroxide and iron hydroxide is preferably used. For example, aluminum sulfate, aluminum sulfate-iron sulfate complex,
Aluminum alum, red mud treated with sulfuric acid, etc. are included, but in the method of the present invention, a flocculant EDEX-
S (manufactured by Hikari Seiko Co., Ltd., trade name: Patent No. 814837) can be particularly advantageously used industrially.

Other suitable examples of acidifying agents are mineral acids such as sulfuric acid, hydrochloric acid, nitric acid, which may also be used in combination with mineral flocculants. For example, inorganic flocculants such as silica sol are stable in the presence of acid, and thus it is of course possible to use silica sol and the like as an acidifying agent. Examples of other inorganic flocculants include stannic acid sol, sulfur hydrosol, iron sulfate, and chlorinated green bean.

In the present invention, the particle size-adjusted pulverized coal (a) is generally added in an amount of 0.1 to 5% by weight based on the raw waste liquid, and within this, COD and BOD in the raw waste liquid are
Using an amount that is 0.2 to 5 times the content, especially 0.5 to 2 times the content, will quickly convert the COD and BOD components in the raw waste liquid into a form that can be coagulated and precipitated, and will also prevent coagulation and sedimentation. This is convenient for effectively carrying out excessive dehydration.

Fine granular carbon is generally added in an amount of 0.05 to 0.5 weight on a dry basis to the raw waste liquid, and within this, 0.05 to 1 times by weight, especially 0.1 to 0.5 times by weight of particle size-adjusted pulverized coal. It is better to use it in quantity.

In the present invention, the use of a combination of particle size-adjusted pulverized coal and fine granular carbon makes it possible to reduce the
It is extremely important to separate COD components through electrolytic treatment and coagulation sedimentation treatment. In other words, since fine particulate carbon has a particle size less than 1/1000 of that of the pulverized coal, the surface area in contact with the waste liquid is extremely large, and the interaction with the waste liquid is large during electrolytic treatment. I believe that it is. On the other hand, pulverized coal acts as a core during the coagulation and sedimentation treatment following the electrolytic treatment, adsorbing the COD component (carbon) to its surroundings and causing it to rapidly coagulate and sediment. When used in combination, effective sedimentation separation of COD components becomes possible. If the amount ratio of carbon (b) is higher than the above range, the dehydration rate will decrease even when dewatering the coagulated sediment, and there will be problems such as clogging of the cloth and an increase in the amount of solids that pass through the grains of the cloth. It tends to cause inconvenience.

The acidifying agent (c) changes the pH of the waste liquid to be treated to the acidic side.
In particular, it is used in an amount sufficient to bring about a pH of 2 to 4. Generally, waste liquid is often adjusted to a state close to neutrality at the end of its life. Accordingly, the present invention has found that in order to convert the COD component in the waste liquid into a form that can be coagulated and precipitated by electrolytic treatment, the pH thereof must be maintained within the above range.

According to the present invention, the thus-formed mixture of the waste liquid, the combined carbon material, and the acidifying agent is then subjected to energization (electrolysis) treatment. This energization process is easily performed by passing a direct current between the two electrodes in an electrolytic cell equipped with a stirring device. As the cathode plate and the anode plate, any known electrode plates can be used, such as a graphite plate, an iron plate (cathode), a titanium clad steel plate (anode), and the like.

The conditions for energization treatment vary depending on the type of waste liquid to be treated, the amount of acidifying agent added, the amount of electrolyte mixed, etc., and cannot be unconditionally specified, but generally speaking, the current density is 0.01 to 1A. /cm ² , especially from 0.05 to
It is preferable to perform the treatment under conditions such that the current is 0.5A/cm ² . The energization process generally takes 10 minutes to 2 hours.
Particularly, 30 minutes to 1 hour is sufficient, and the end point of the energization treatment can be easily confirmed when the pH of the treatment liquid near the cathode becomes neutral.

In the present invention, the waste liquid to be treated can be energized in the presence of an electrolyte. As such an electrolyte, common salt (NaCl) is preferred, but other electrolytes such as mirabilite (NaSO ₄ ), sodium nitrate (NaNO ₃ ), and calcium chloride can also be used. Although such an electrolyte can be added prior to the start of the energization treatment, it is generally added at an intermediate stage of the energization treatment to reduce COD in the treatment solution.
This is preferable in order to effectively remove components and enhance the decolorizing effect of the treatment liquid. The amount of electrolyte added varies depending on the type of waste liquid to be treated, but generally 100
It can be varied within the range of 2000 ppm to 2000 ppm.

In order to suspend and disperse particle size-adjusted pulverized coal and fine-grained carbon in the waste liquid to be treated during energization treatment,
Stirring is preferable. In this case, it is important to avoid rapid stirring, and it is desirable to stir intermittently or at a low speed in order to effectively carry out the energization process.

In the present invention, the exact reason why the COD components in the waste liquid are converted into a form capable of coagulation and sedimentation by the above-described energization treatment is still unknown. However, considering that the combination of the addition of a combined carbon material, acidification of the waste liquid to be treated, and energization treatment is effective in removing COD components, the added combined carbon material acts as an electrode and adsorbent dispersed between the negative and positive electrodes. It is presumed that this is due to the fact that it acts as an agent and effectively electrolytically adsorbs COD components in the acidified waste liquid to be treated.

Next, add an alkali (d) such as caustic soda, soda carbonate, or lime to the waste liquid after the energization treatment to neutralize the pH of the liquid to near neutrality, or further add a polymer flocculant (e). The supernatant liquid is then separated into a supernatant liquid from which the COD component has been substantially removed and an aggregated floc of the COD component. Generally, a relatively short time of 1 minute to 20 minutes is sufficient for this coagulation and sedimentation treatment, and at this stage, the COD components in the waste liquid rapidly form coagulated flocs using the particle size-adjusted pulverized coal as nuclei. Furthermore,
Usually, the coagulation effect can be further improved by using the organic polymer flocculant component (e) in combination. Examples of such flocculants include commonly known anionic, cationic, or nonionic agents such as polyacrylic acid, polymethacrylic acid, CMC, and sodium alginate. The amount used varies depending on the condition of the waste liquid and the concentration of the mixed liquid before addition of the neutralizing agent, but usually a very small amount of addition of 1 ppm or less of 20 ppm or more of the amount of waste liquid will bring about a sufficient effect. If the energization (electrolysis) treatment is carried out sufficiently,
In some cases, the above-mentioned neutralization with alkali can be omitted, but in general, it is desirable to carry out the energization treatment in a short time and to return the liquid properties of the entire treatment liquid to neutrality by adding alkali, in order to shorten the total treatment time. .

The mixture of waste liquid and components (a) to (e) that has been thoroughly mixed and stirred is introduced into a settling tank where rapid solid-liquid separation is performed, the aggregates settle, and the waste liquid is mixed with COD and other substances. Impurities are removed and the water is purified and overflowed in the form of supernatant water, which is then discharged through a discharge stabilization tank. Even in the case of continuous treatment, it is sufficient if the capacity of the sedimentation tank is large enough to accommodate the amount of water to be treated for 2 hours. The flocs settled at the bottom of the settling tank are continuously pulled out from the bottom pipe and fed to a continuous filtration device.

As a continuous filtration device, for example, a cloth is used as an endless belt, the direction of movement of the belt is tilted upward, and a side plate is provided to form a slurry supply section on the lower side of the front side, and a perforated plate is provided at the bottom of the belt. support the cloth,
The coarse particles of pulverized coal directly settle on the cloth to form a self-precoat, and while the moisture is naturally dehydrated, the coagulated sediment, that is, the fine particles of pulverized coal, carbon, and its aggregates are sequentially transferred upward. A deposited layer is formed on the self-precoated layer. The deposited layer transferred from the liquid reservoir then moves to the upper side of the box under low negative pressure (100 to 150 mmHg), is dehydrated by suction from the back side, and further transfers to the upper side of the box under low negative pressure (150 to 250 mmHg).
mmHg) on the top side of the box to reduce the moisture content to 50% or less. If the moisture content of the dehydrated cake is desired to be 40% or less, it can be brought to a predetermined low moisture content by passing it through a press-attached drum suction section with high negative pressure (300 to 350 mmHg) (Patent No. 808330). The carbon-containing sludge cake finally obtained is 3000Kcal/
Since it has a natural calorific value of Kg~5000Kcal/Kg, there is no need to supplement fuel when incinerating it.
It can be disposed of economically and without pollution.

The attached drawing is a process diagram of the present invention, in which 1 is an electrolytic cell, 2 is a neutralization tank, 3 is a flocculation tank, 4 is a sedimentation tank, 5 is a continuous filter, and electrolytic tank 1 is equipped with a stirrer. 6, an anode 7, and a cathode 8 are provided. Further, in the figure, P indicates a pump, M indicates a motor, and PV indicates a metering valve.

The excellent effects of the present invention will be explained with the following example.

Example: Photographic developer waste liquid with pH 11 (COD 5500ppm) in an electrolytic treatment tank equipped with a stirrer and a graphite electrode plate
In addition, iron sulfate-aluminum flocculant (EDEX-S Hikari Seiko)
Co., Ltd. product) 1500ppm was added, and then particle size adjustment pulverized coal (EDEX-MFC, Kouseiko Co., Ltd. product) was added.
3000 ppm and 400 ppm of fine carbon (EDEX-C Hikari Seiko Co., Ltd. product) were added. The pH of the mixture was 4.5. between the two poles while stirring at low speed or intermittently.
30 at a current density of 0.16A/ ^cm2 with a DC voltage of 25V applied.
Current was passed for a minute. When 500 ppm of common salt (NaCl) is added as an aqueous solution, the electrolysis of the mixed solution is promoted along with the electrolysis of the salt aqueous solution, and the mixed solution near the cathode reaches a neutralization point. When the area around the cathode became neutral, it generally indicated that the electrolysis accompanied by the bleaching effect was almost complete. After cutting off the electricity, 500 ppm of caustic soda (NaOH) was added, the pH of the mixture was adjusted to around 7, and 10 ppm of a polymer flocculant (Nippon Kayaku A-335) was added.
A floc with MFC as the core was formed instantly and separated and sedimented. The supernatant water becomes colorless and transparent with COD value
It became 25ppm.

In addition, as a comparative example, methods that omit electrolysis and salt addition, that is, EDEX-S, MFC, EDEX
In the coagulation reaction in which -C, caustic soda, polymer flocculant, etc. were used in exactly the same amounts as above and subjected to a mixed reaction, the COD value of the separated supernatant water was 78 ppm, and the COD removal rate was decreased.

[Brief explanation of the drawing]

The attached drawings are process diagrams of the present invention, in which 1 is an electrolytic cell, 2 is a neutralization tank, 3 is a flocculation tank, 4 is a sedimentation tank, 5 is a continuous filter, 6 is a stirrer, 7 is an anode, 8 is cathode, P is pump, M is motor, RV
indicate metering valves, respectively.

Claims (1)

[Claims] 1. In the high COD waste liquid, (a) particle size-adjusted pulverized coal containing 85% by weight or more of particles with a particle size of 9 to 500 mesh;
(b) fine particulate carbon and (c) acidifying agent are added and mixed;
The resulting mixed solution is treated with electricity in the presence of an electrolyte,
This energized solution is then neutralized and a polymer flocculant is added thereto, and then separated into a supernatant liquid from which the COD component has been substantially removed and a flocculated floc of the COD component. Processing methods for liquids, etc.