JPS61161197A - Treatment of organic waste water - Google Patents

Abstract

PURPOSE:To remove economically and highly the suspended matter in waste water by circulating and reusing sludge separated at the intermediate stage as a flocculant, and separating an appropriate amt. of sludge to the outside of the system in accordance with the Ca sulfate concn. in the sludge. CONSTITUTION:A flocculant consisting essentially of a ferric salt is added to org. waste water to regulate the pH to 3-5.5 at the first stage, an the contaminants, etc. are flocculated and separated along with the flocculated ferric hydroxide. At the second stage, an iron salt as the oxidation catalyst and hydrogen peroxide as the oxidizing agent are added to the water treated at the first stage to oxidize and decompose org. materials, etc. At the third stage, after a reducing agent is added to decompose and remove the hydrogen peroxide, an alkaline agent is added to regulate the pH to >=4, and the iron salt catalyst is deposited as ferric hydroxide and removed. At the fourth stage, after an appropriate amt. of sludge is separated to the outside of the system in accordance with the Ca sulfate concn. in the sludge, the deposited and separated ferric hydroxide is dissolved by adding a mineral acid, and regenerated as the flocculant which is circulated and reused.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for treating wastewater containing organic substances, and more specifically, it relates to a method for treating wastewater containing organic substances. The present invention relates to a new and economical treatment method whose main purpose is to remove components.

(Prior art) In recent years, regulations on the quality of water discharged into closed water bodies have been further strengthened from the viewpoint of eutrophication countermeasures, and in particular, at the same time as nitrogen phosphoric acid and other components, chemical oxygen demand (hereinafter abbreviated as CODM11)
Coupled with the introduction of regulations on the total amount of wastewater substrate, there is an urgent need to establish a technical removal method.

Normally, biological treatment methods used to treat organic wastewater reduce the biological oxygen demand value (BOD) due to its nature; CODMn treatment of organic wastewater is ineffective against CODMII caused by substances, and CODMn is maintained at a high level compared to BOD due to the accumulation of waste materials discharged as a result of biological metabolism. making it even more difficult.

In response to the tightening of wastewater regulations, new methods are being tried in wastewater treatment technology, including Tanpo et al. (Tanpo, Kamei: Water Works Association Magazine, No. 502, 2-24 (19
78), Nambu Kaze et al.
Abstracts of the Annual Academic Conference, Part 2, 501-502
(197B)), the evaluation of wastewater by gel chromatography was progressed, and conventionally BOD or CODMn
Organic substances in wastewater, which had been measured indirectly based on oxygen consumption potential such as A new water quality evaluation method that measures water quality more precisely has been established, and research into advanced treatment of organic wastewater is being actively conducted.

For example, if we look at leached sewage from the waste physical stage, organic matter in the waste remains in the landfill layer for a long period of time after being landfilled with food waste or non-combustible materials.

As a result of undergoing anaerobic or aerobic decomposition, the organic matter contained in the waste effluent contains some easily biodegradable sugars, protein amino acids, fatty acids, etc., as well as non-biodegradable substances and Most of them are organic polymer compounds such as mucopolysaccharide, humic acid, and fulvic acid, which are waste substances discharged as a result of biological metabolism, and have a high organic pollution load and are colored black or brown, making them biologically With only the standard processing method,
It is impossible to achieve a high degree of saturation.

On the other hand, in human waste treatment, the organic substances contained in large amounts in human waste are usually anaerobically digested.

Although it is treated using aerobic digestion or a combination thereof, the amount of CODMll remaining is large compared to BOD due to biometabolic waste substances that newly accumulate during the biological treatment process. Not only is the removal of bile pigments contained in human urine insufficient, but also the chromaticity of biometabolic waste substances that accumulate during the course of biological history usually results in a brown color.

In addition, wastewater from the brewing and fermentation industries is a result of fermentation and decomposition of organic materials (especially grains such as soybeans, rice, and wheat) as raw materials over a long period of time using microorganisms such as yeast and fungi during the production process. The wastewater discharged from the process is highly subject to microbial decomposition, so biologically degradable fatty acids, alcohols, proteins, amino acids, and sugars are expected to be removed by biological treatment methods. It contains a large amount of biologically persistent substances, which are waste substances of biological metabolism, and is usually brown to pale yellow in color.

(Problem to be solved by the invention) Biological treatment methods are usually used to treat wastewater, human waste, sewage, or organic wastewater discharged from various industries, due to the equipment costs and running costs. It is used for wastewater treatment due to its low cost, but although it is an excellent method for decomposing and removing biodegradable substances, it is naturally produced as a result of the treatment of biodegradable substances and biological metabolism. Due to the accumulation of waste materials, this method is not always satisfactory as an advanced treatment method for organic wastewater.

Various treatment methods have been developed to treat wastewater containing biorefractory substances or biometabolic waste substances.
Typical of these methods include methods that mainly involve physicochemical treatments such as activated carbon adsorption and ozone oxidation. These methods are effective in treating wastewater with a high pollution load.
Although it requires large-scale equipment and huge running costs,
Contains problems related to wood quality in processing technology.

In other words, in the activated carbon adsorption method, the biometabolic waste substances accumulated in biologically treated water are organic polymer compounds such as glycoproteins, humic acids, and fulvic acids with molecular weights of several thousand or more. Adsorption and diffusion into pores are extremely poor, and the organic matter removal effect is low.

Although the ozone treatment method oxidizes and decomposes organic polymer compounds in wastewater and partially lowers C0Dr'-(n, its treatment effect is low, and the low-molecular organic compounds produced during the oxidative decomposition process are easily bioactive. Both types have become a major problem in practice, as they are converted into degradable substances and are recognized to have defects that increase BOD.

As a result of extensive research under these circumstances, the present inventors have discovered an excellent method that can simultaneously, efficiently, and economically remove suspended solids, organic substances, and color components from organic wastewater. They discovered this and completed the present invention.

(Means for Solving the Problems) That is, the present invention provides a method for treating organic wastewater, in which (a) a flocculant mainly containing ferric stone is added to the organic wastewater, and the pH is adjusted to 3 to 5. After adjusting to the range of 5, pollutants,
The first step is to coagulate and separate organic substances and color components together with ferric hydroxide flocs.

(b) A second step in which an iron salt as an oxidation catalyst and hydrogen peroxide as an oxidizing agent are newly added to the treated water of the first step to oxidize and decompose organic substances and chromaticity components.

(c) The oxidized water in the second step can be used as is, or if unreacted hydrogen peroxide remains, a reducing agent is added to decompose and remove the hydrogen peroxide, and then an alkaline agent is added to adjust the pH.
4 or more, and the third step is to precipitate and separate the iron salt catalyst as ferric hydroxide; The fourth step consists of removing and separating the sludge from the system, adding mineral acid to dissolve it, regenerating it as a flocculant mainly using the ferric salt from the first step, and recycling and reusing it. This is a method for treating organic wastewater, characterized in that slaked lime is used as an alkali agent in any or all of the three steps, and sulfuric acid is used as the mineral acid in the fourth step.

To explain the present invention in more detail, the above-mentioned method of the present invention includes:
It is a simple process to remove organic substances and color components, including biorefractory substances and biometabolic waste substances, in organic wastewater, with a simple processing method, low processing cost, and an extremely high rate of removal. It's a method.

The organic wastewater to be treated by the present invention is preferably waste physical wastewater, biologically treated wastewater, sewage, human waste, collected dust water, incinerator wastewater such as pit sewage, and organic factory wastewater. If biodegradable sugars, fatty acids, alcohols, and other water-soluble organic substances are contained in the wastewater, the activated sludge method, trickling filter method, rotating disk method, or anaerobic digestion method should be used in advance. It is necessary to reduce the BOD as much as possible to 100 PPII or less using a biological treatment method in order to significantly reduce the amount of chemicals used in the present invention, such as iron salt catalysts and hydrogen peroxide. It is processing.

To explain the method of the present invention more specifically, the main feature of the present invention is that the slatch separated in the third step is
The point of recycling iron as a coagulant and the third point.
The point is to separate and remove an appropriate amount of the slatch that has precipitated during the process out of the system according to the concentration of calcium sulfate in the slatch. By adopting such means, the first step ~
Use slaked lime and sulfuric acid as the alkali agent added in any or all of the third step and as the mineral acid added in the fourth step, both of which are low cost and have good operability and processability. became the turning section. In addition, the gradually concentrated heavy metal hydroxides are separated and removed from the system along with the slatch, making it possible to reduce the amount of acid and alkali agents added in each process, resulting in a significant overall cost reduction. be done.

Therefore, first, the fourth step, which mainly characterizes the present invention, will be explained in detail based on the embodiment shown in FIG.
The Jl process to the third process will be explained in detail.

That is, in the fourth step of the present invention, the sludge separated in the final solid-liquid separation tank 7 of the third step is led to the 5 flocculant regeneration tank 8, where it is dissolved in sulfuric acid. Note that sludge can be dissolved with any strong acid, but all acids other than sulfuric acid are more expensive than sulfuric acid and are not easy to handle, especially nitric acid and Phosphoric acid causes problems such as eutrophication of treated water.

Furthermore, since slaked lime is used as an alkali agent in the first to third steps of the present invention, if sulfuric acid is used as a mineral acid in the fourth step of the present invention, calcium sulfate is not generated in the treatment system. Of course.

Under such conditions, if the sludge separated in the solid-liquid separation tank 7 is dissolved with sulfuric acid and the resulting ferric sulfate is recycled and reused as a flocculant, calcium sulfate in the treatment system will gradually be removed. Increase the concentration to 2,000 mg/ml ~
At 3,000 mg/a, a precipitation reaction occurs, and scale adheres to piping, water tanks, and other instrumentation equipment, causing blockages and malfunctions.

It comes from the tree! The problem caused by the use of sulfuric acid and slaked lime was solved as follows, and it became possible to use cheap and easy-to-handle slaked lime and sulfuric acid as the alkali agent and mineral acid used in the present invention. .

That is, a part of the sludge separated in the final solid-liquid separation tank 7 is separated and removed from the system until the calcium sulfate concentration in the entire sludge falls below a certain value, and fresh ferric salt is replenished. By doing so, the concentration of calcium sulfate in the entire treatment system is reduced, and the precipitation of calcium sulfate as described above can be prevented. Therefore, as the mineral acid added in the flocculant regeneration layer 8, sulfuric acid, which is low cost and easy to handle, can be used. Furthermore, it has become possible to use slaked lime, which is low cost, easy to handle, and has good floc flocculation and sedimentation properties, as the alkaline agent added in any or all of the first to third steps. Ta. Also,
Furthermore, it prevents the concentration of zinc, cadmium, etc. that precipitates in the pH range of 6 to 7! This makes it possible to reduce the amount of alkaline agents and mineral acids added in each process. This is because, as mentioned above, in the first solid-liquid separation tank, the pH is between 3 and 5.5, and most of the heavy metals that precipitate in the pH range of 6 to 7 are present in the wastewater in the form of ions, so they are not treated as sludge. It is impossible to remove it from the system.

On the other hand, in the final solid-liquid separation tank, if the sludge that precipitates as hydroxide is not separated and removed from the system as slurry 2 in the separation tank, the required amount of acid and alkali agents added in each process Not only does this increase the amount of flocs generated, but it also obstructs solid-liquid separation processing.

From the above, the sludge separated in the final solid-liquid separation tank 7 has a calcium sulfate concentration of 2, OOOI
When it reaches Ig/l~3, OOOrmg/l, the C degree is θ~2,500+ag/vertical, preferably 2,0
When the amount is continuously or intermittently introduced from the tube 26 to the tube 32 until the concentration is as low as 00+mg/d, it is separated and removed from the system.
It becomes possible to use inexpensive chemicals such as slaked lime and sulfuric acid as the acid and alkali agents added in each step, and processing performance and operability are also improved. Furthermore, the concentration of heavy metals such as zinc and cadmium can be suppressed, and the amount of acid and alkaline agents added in each process can also be reduced.

Regarding the frequency of separation and removal of calcium sulfate, the amount of removal per separation can be determined by understanding the concentration and time at which calcium sulfate starts to precipitate, that is, the concentration rate. You can find it by understanding the relationship with the time it takes to reach it. Furthermore, the sludge that has been separated and removed is subjected to dewatering treatment together with the separated sludge in an intermediate solid-liquid separation tank.

Next, the dissolution method in the flocculant regeneration tank 8 will be described. The method involves adding sulfuric acid 24 and stirring for a certain period of time, or continuously. Here, slatch reacts with sulfuric acid and dissolves, and the amount of sulfuric acid used needs to be at least stoichiometric for ferric hydroxide to become iron salt of sulfuric acid.
In a separated liquid where the slatch concentration constantly fluctuates, pH 2
Complete dissolution can be achieved by controlling the amount of acid added. If the pH is 2 or more during the dissolution process, the dissolution of ferric hydroxide will be incomplete, and it is easy to imagine that the effect will be poor when reusing it as a flocculant in the first step. It is. In addition, when the pH is below 1, the dissolution rate is rapid, but unless the alkalinity of the organic wastewater flowing into the first step is sufficiently high, a large amount of It requires a neutralizing agent and is not economical.The higher the dissolution temperature, the more quickly and efficiently the reaction tends to occur. However, the purpose of the present invention can be sufficiently achieved even at room temperature, so the dissolution method is not particularly limited. Although the reaction time varies depending on the stirring intensity of the pH 1 flocculant regeneration tank and the ferric hydroxide concentration, the reaction is usually completed within 120 minutes. The ferric salt-based flocculant thus obtained is recycled through pipe 27 to the first step and reused.

Next, each of the other steps of the present invention from step 11 to step 3 will be explained in detail.

In the first step, the organic wastewater is led through the pipe 9 to the first mixing tank 1 while being stirred, a flocculant mainly containing ferric iron is added through the pipe 17, and the organic wastewater is introduced into the first mixing tank 2 through the pipe 17. with a given p
The organic matter and chromaticity components in the wastewater are precipitated together with the ferric hydroxide floc.

The flocculant mainly composed of ferric salt used here is f! A solution based on S2 iron salts is used, but fresh ferric J l 7 is used during equipment commissioning and for replenishment. The ferric salt used can be ferric sulfate, ferric chloride, ferric nitrate or polyferrous sulfate, but ferric nitrate is usually used because of its effect on the treated water. It cannot be used in consideration of

Although the amount of coagulant mainly composed of ferric salts varies depending on the amount of organic matter contained in the wastewater,
The treatment effect improves in proportion to the amount of iron salt added, but it is usually added in the range of 1 opps to 1,000pp in terms of iron atoms.

It is also possible to generate ferric hydroxide flocs by adding either an acid or an alkaline agent to the first mixing tank 1 at the same time as the addition of the ferric salt, but the pH at the time of aggregation is Since it is an important component of the present invention to strictly maintain the pH within the range of 3 to 5.5, preferably 4 to 4.5, a separate first pH adjustment tank 2 is provided to maintain the pH within the range of 4 to 4.5. It is preferable to adjust it within the above range.

For pH adjustment in the first pHal adjusting tank 2, an acidic or alkaline pH adjusting agent 18 is added depending on the nature of the wastewater to maintain the optimum pH within the above range. Biologically treated organic wastewater has a pH of 3 to 5.0 even when a strongly acidic ferric salt is added due to the pH pH of NH discharged as a result of biodegradation.
If the pH does not drop to the optimum pH of 5, add a mineral acid such as sulfuric acid or hydrochloric acid, but usually with the addition of a flocculant mainly composed of ferric salts, the pH will drop to 4 or less. Add agent to adjust to optimum pH. The alkali used for neutralization may be any strong alkali such as aqueous soda, caustic potash, slaked lime, quicklime, etc. However, as mentioned above, from the economical and ease of handling standpoints, it is better to use the saltpeter method. Preferably, the time required for neutralization is about 1 to 20 minutes, similar to normal strong acid or strong alkali neutralization reactions, and the generated secondary hydroxide
Iron precipitates and agglomerates together with biorefractory substances, biometabolic waste substances, and chromaticity components with a molecular weight of several thousand to 1,000, which precipitates as colloidal particles under acidic conditions.

The pH adjustment liquid is led to the intermediate solid-liquid separation tank 3 through a pipe 11, where a flocculant 19 is added, and ferric hydroxide with organic substances or chromaticity components flocculated by flocculation sedimentation or flocculation pressure flotation, etc. The flocs are separated and removed by a pipe 25, concentrated in a slatch concentration tank (not shown) provided as required, and after dehydration, a neutralizing agent is mixed in to make the flocs neutral and then disposed of.

The treated water separated into solid and liquid in the first step passes through the pipe 12 to the second
While being led to the second mixing tank 4 of the process and being stirred, iron salt 20 as a fresh oxidation catalyst and hydrogen peroxide 21 as an oxidizing agent are newly added.

The iron salt added as an oxidation catalyst is a compound having Fe(II) ions such as ferrous sulfate salts and ferrous chloride salts, and Fe(DI) ions such as ferric sulfate salts and ferric chloride salts. Or their aqueous solutions, and nitrates such as ferrous nitrate and ferric nitrate crucibles can be expected to have sufficient oxidation catalytic action, but
In consideration of eutrophication of treated water, it is not used except in special cases, and ferrous sulfate is usually used because it has a high oxidation catalyst function and is cheap.

Iron salts react with hydrogen peroxide in wastewater to generate hydroxyl radicals with strong oxidizing properties and are hydrolyzed to the optimum pH of 4 or less for one reaction, but the optimum reaction pH may be adjusted as necessary.
Acid or alkaline pH adjuster 18
Add.

The amount of iron salt added as an oxidation catalyst can be determined depending on the type and concentration of the oxidizable substance, the amount of hydrogen peroxide injected, and the reaction time, but usually the iron salt used in Step 1I is This is determined according to the effective usage amount of the flocculant, and as in the first step, the amount is 1 opp to 1. oooPP Added in the intestinal range.

In addition, the amount of iMs hydrogen hydride added is not particularly limited, but is determined depending on the type of oxidizable substance in the wastewater, the degree of fa, the target water quality, etc.
0.1 to 2 in terms of effective oxygen in hydrogen peroxide
It is added in twice the range.

The mixed liquid is led to the reaction tank 5 through a pipe 13, where an oxidation reaction is carried out.The reaction tank 5 is mechanically or air agitated.1The oxidation reaction time in the reaction tank 5 is as long as the water in the waste water It varies depending on the type of oxidizable substance, concentration, reaction temperature, amount of iron salt catalyst, and amount of hydrogen peroxide.For example, in the case of wastewater where the reaction is completed in a short time, such as wastewater leached from a waste physical site, a second mixing tank is used. Although the reaction at 1 is usually sufficient, an oxidation reaction tank 5 is provided, and the reaction is completed sufficiently in a residence time of 5 minutes to 24 hours at room temperature.The higher the reaction temperature, the more quickly and efficiently the reaction tends to occur. However, since the object of the present invention can be sufficiently achieved even at room temperature, there is no particular limitation.

Next, the oxidation reaction treated water passes through the pipe 14 to the second stage of the third step.
The alkali agent 18' is introduced into the pH adjustment tank 6 while being stirred.
Alternatively, a reducing agent 22 may be added if necessary.

Neutralization p) I when the iron salt catalyst in the oxidation reaction treatment water is present in the form of Fe(m) ions, precipitates ferric hydroxide flocs at 4 or more E and in the form of Fe(ff) ions. If present, the pH is adjusted to 9 or higher with an alkaline agent, and while aeration is performed, Fe(IT) ions are oxidized and precipitated as ferric hydroxide flocs, and at the same time, organic matter in the wastewater is coagulated and separated.

In addition, if unreacted hydrogen peroxide remains in the oxidation reaction, it is detected as a CODMII value during CODMn measurement and increases the apparent CO00Mn value. 1 iron, nitric acid 1
Reducing agents such as Fe(II) ions of iron or sodium sulfate or sodium thiosulfate are added to decompose unreacted residual hydrogen peroxide, but normally even if added in excess, the pH will not exceed 7. A ferric salt is used that is easily oxidized and precipitated into Fe(m) by aeration with F, and is separated and removed as ferric hydroxide at pH 9 or higher.

The neutralized treated water passes through a pipe 15 in the final solid-liquid separation tank 7, where a coagulation aid 19 is added, solid-liquid separation is performed by sedimentation or flotation, and the treated water is separated into ferric hydroxide flocs and treated water. is discharged through tube 16 with pH readjustment as necessary, or sent to other processing steps for higher-level processing. On the other hand, the ferric hydroxide separated in the final solid-liquid separation tank is passed through the pipe 26 and a part of it is removed or separated through the pipe z6 and the pipe 32, and the remaining part is sent to the flocculant regeneration tank 8. However, if ferrous hydroxide is contained in iron hydroxide, the performance of the ferrous flocculant in the first step will be reduced, so the pH of the slatch may be adjusted as necessary.
After being oxidized by aeration while maintaining the temperature at 7 or above to change Fe (■) to Fe (m), it is poured into the coagulant regeneration tank 8, where it is treated as described above and circulated to about 1T. Ru.

In addition, in the second illustrated example, if the oxidized water that has been oxidized in the third T contains Fe(H) ions, or in order to reduce and remove unreacted hydrogen peroxide in the third step, In order to oxidize and precipitate excessively added Fe(II) ions, a step of oxidizing with air 23 at a pH of 7 or higher in an aeration tank 28 is provided.

In the example shown in the third diagram, when the iron hydroxide slatch separated and removed in the third T or so contains Fe(II) ions,
A new iron hydroxide sludge oxidation tank 30 is installed, and oxidation is carried out with air 23 while maintaining the pH at 7 or higher.The principle of the treatment method in both the second and third illustrated examples is as follows. It will be easily understood that this example is exactly the same as the example shown in FIG.

(Operation/Effect) As described in 1-11, the present invention can highly remove organic matter and chromaticity components in wastewater, including biologically persistent substances and biologically metabolic waste substances, which were extremely difficult to treat in the past. At the same time, biological nitrification and denitrification methods and physicochemical denitrification methods are installed at the front stage to remove the ``N'' component and also perform treatments such as dephosphorization and sterilization.
The present invention enables the effective use of ferrous salts, which are often discharged as industrial waste, and improves running costs, processability, and operability. of['! This is extremely valuable as a J-type processing method.

Next, the method of the present invention will be explained in more detail with reference to Examples, but the treatment of undeveloped IJJ is not limited to these Examples.

Example 1: Sulfuric acid is added as the 4th T to the slatch mainly composed of ferric hydroxide that has been sedimented and separated in the S3T stage to adjust the pH to 1.5. A flocculant containing ferric salt as a superstructure, which was regenerated by stirring for 30 minutes, was added in an amount of 200 ppm in terms of iron atoms to the biological nitrification and denitrification treatment water of waste physical leaching wastewater, and slaked lime was added. The pH was adjusted to 4, and organic matter and chromaticity components in the wastewater were coagulated and separated together with ferric hydroxide flocs. To this 1L of treated water, 2009p of ferrous sulfate as an iron salt catalyst in terms of iron atoms and 50ppm of hydrogen peroxide as an oxidizing agent in terms of effective oxygen were added, and the liquid was adjusted to PN3 while stirring. Allow the oxidation reaction to proceed. 15
Slaked lime is added to the oxidation reaction treated water of about 2T which has been subjected to the oxidation reaction treatment for 30 minutes, and while keeping the pH at 7, air stirring is performed for 30 minutes to oxidize the ferrous iron in the mixed liquid to ferric iron, The generated ferric hydroxide flocs are separated by sedimentation and used as treated water for the final step. The entire amount of the slatch, which is mainly composed of ferric hydroxide that has been sedimented and separated, is sent to the slatch treatment process once every July for 24 hours continuously. In addition, the concentration rate of calcium sulfate in this equipment is 2 parts per liter/Hr,
If the entire amount of slatch sent from the final solid-liquid separation tank is separated and removed continuously for 24 hours, the calcium sulfate concentration will be reduced to about 30%. Further, the allowable amount of calcium sulfate is 2.50011 g/view.

Next, the running costs and wood quality results in the above examples will be described.

Table 1 shows the results of 10% of slatch when using hydrochloric acid and caustic soda as acid and alkali agents in each process, and when using sulfuric acid and slaked lime to separate and remove a part of the slatch from the system.
,000rrr of wastewater, and Table 2 compares the water quality at that time. still.

A using caustic soda or hydrochloric acid as an acid or alkali agent,
B indicates those using slaked lime and sulfuric acid.

-I L ≦ L 26 blood beans y yo 4 yu z yu 80,000
- Salt, Ugly, Koeeh te, ooo
-nJ';IM,':IZ
h 3,000m
Ugly Yuno) 4
．． 000 north suction j wing 1ji x l-1,000 -total 1 as,ooo
s,oo.

- Soichi Kado? −” The measurement item month is a lie ■ne and the practice is the tree and the plan is α
υ■O treated water volume A 43,800rn"7 years --B ae,ooom"7 years
--A 257.7ppm ft1
．． 3ppm (76.2%) 34.7ppm (8
13.5%) CODM” 8 2
80.4ppm 54.5ppm (79,1
%) 28.3ppm (89.9%) A
457.5° 41.5” (90, Ko)
14.9@(9L7%) Chromaticity B 4B
9.8° 32.0° (83, for) IQ,
2° (97, Akira) ss A 188ppm
52ppm (?2.OK) 28ppm (
8B, [)B 233ppm 48p
pm (79,4%) 8ppm (9B, 1l
n) * () indicates removal rate

[Brief explanation of drawings]

FIG. 1, FIG. 2, and FIG. 3 are process explanatory diagrams of the present invention. l... 1st mixing tank 2... 1st P) l adjustment tank 3...
Intermediate solid-liquid separation tank 4...First mixing tank 5...Reaction tank
6.1st pHJR1 tank? ...Final solid-liquid separation tank 8
...Flocculant regeneration tank 9-16...Pipe 17...Flocculant 18...Po adjuster 18'...Alkali agent 18...Flocculating aid 20...Iron salt 21...Inorganic acid 22...1 Agent 23...Air 2
4.Inorganic acid 25-27..Pipe 28..Aeration oxidation tank 28..Pipe 30..Iron hydroxide sludge oxidation tank 31-32..Pipe

Claims (2)

[Claims] (1) In the method for treating organic wastewater, (a) a flocculant mainly consisting of ferric salt is added to the organic wastewater to adjust the pH to a range of 3 to 5.5, and then the pollutants are removed. A first step in which organic substances and color components are coagulated and separated together with ferric hydroxide flocs. (c) The oxidized water in the second step may be used as it is, or if unreacted hydrogen peroxide remains, a reducing agent may be added. After decomposing and removing hydrogen peroxide, add an alkaline agent to adjust the pH.
4 or more, and a third step in which the iron salt catalyst is precipitated and separated as ferric hydroxide; The fourth step consists of removing and separating the iron from the system, adding mineral acid to dissolve it, regenerating the ferric salt from the first step as a flocculant, and recycling and reusing it. - A method for treating organic wastewater, characterized in that slaked lime is used as an alkali agent in any or all of the three steps, and sulfuric acid is used as the mineral acid in the fourth step. (2) The method for treating organic wastewater according to claim (1), wherein the calcium sulfate concentration is 2.500 mg/l or less.