JP7645670B2 - Wastewater treatment method and wastewater treatment device - Google Patents

Description

The present invention relates to a wastewater treatment method and a wastewater treatment device.

Traditionally, wastewater containing oil, organic nitrogen, suspended solids (SS), etc. has been discharged from factories and business establishments, regardless of industry. In particular, wastewater discharged from slaughterhouses, meat processing facilities, meat processing plants, etc. contains a lot of animal blood. The components in such wastewater are mostly organic nitrogen, and also contain oil and SS.

The common methods of treating wastewater with high organic nitrogen concentrations include pretreatment (primary treatment), biological treatment (secondary treatment), and advanced treatment (tertiary treatment). Pretreatment is a process to remove impurities from the wastewater, and includes physicochemical treatment methods (screens, pressure flotation treatment, coagulation sedimentation treatment, natural solid-liquid separation, etc.). After pretreatment, the wastewater is biologically treated, and if a large amount of nutrients or components that could not be removed by biological treatment remain, advanced treatment is used. The treated water is discharged from the system, but the screen residue, oil-containing sludge (flotation separation scum), excess sludge, etc. generated in each process require separate treatment. After removing the water from the screen residue, it is disposed of or composted. The oil-containing sludge and excess sludge go through a sludge treatment process (concentration, dehydration, drying, incineration, etc.) before being finally disposed of or reused.

JP 2019-37955 A (Patent Document 1) describes an example of a water treatment method and water treatment device for wastewater containing oil, which includes a flocculation step in which a cationic organic polymer flocculant is added to and mixed with the oil-containing wastewater to form flocs, and a solid-liquid separation step in which the generated flocs are separated from the separated liquid. Patent Document 1 also describes the addition of a natural polymer-based oil remover or a synthetic polymer-based oil remover before the addition of the cationic organic polymer flocculant in the flocculation step.

JP 2002-346306 A (Patent Document 2) describes a blood wastewater treatment method and blood wastewater treatment system that includes a coagulation process in which hydrochloric acid and an aqueous solution of ferric chloride are added to blood wastewater to coagulate organic matter in the blood, a process in which a precipitate is precipitated and precipitated by neutralization with an alkali, and a removal process in which the wastewater and the precipitate are separated and the precipitate is removed, and in which a coagulant can be added in the removal process. It also describes that the precipitate is dehydrated using a dehydrator and then disposed of as sludge waste.

JP 2014-147859 A (Patent Document 3) describes a water treatment method and system for a blood wastewater treatment system that includes a settling tank that adds a coagulant to blood wastewater to separate it into a sedimentation portion containing blood components and an upper wastewater, a microbubble treatment tank that uses microbubbles to perform foam separation on the upper wastewater to produce separated water, an ozone oxidation treatment tank that oxidizes the separated water to produce sterilized water, and a filtration tank that treats the sterilized water with activated carbon to produce reclaimed water, and that has a circulation pump for circulating the treated water through the microbubble treatment tank and the ozone oxidation tank.

JP 3-127944 A (Patent Document 4) describes a device for recovering and reusing high-quality protein, the main component of which is high-concentration blood discharged from fish, at low cost. The device includes a process for heating high-concentration fish blood juice at 50-55°C to produce a colorless gel, a process for diluting the gel with salt water to produce a diluent, a process for adjusting the pH of the diluent to produce flocs, a process for adding a polymer coagulant to the diluent and flocs to thicken the flocs, a process for electrically separating the thickened flocs, a process for dehydrating the separated sludge and recovering high-quality protein, and a device for adding and reusing the recovered protein as a raw material for the factory. It also describes how the treatment device reduces SS and BOD in the wastewater, making wastewater treatment easier.

JP 4-27492 A (Patent Document 5) describes a water treatment method that includes the steps of adding 5 to 200 wt % of an inorganic flocculant (one type or a mixture of two or more types) to water containing animal protein, based on the total organic carbon in the animal protein, adjusting the pH of the wastewater after the addition of the flocculant to 3 or higher, heating the wastewater after the pH adjustment to 60°C or higher, and filtering the wastewater after the heating treatment.

JP 3-93689 A (Patent Document 6) describes a method and an apparatus for treating recovered products, including a process in which a returned food product (solidified form) containing or not containing protein is heated and held, and drained and separated, and the solidified product after draining and separation is fermented and decomposed to produce recycled products such as fertilizer, and a process in which a flocculant is added to a returned food product (liquid form) containing or not containing protein, a pH adjustment process, a process in which the returned food product is heated and held, and drained and separated, and the solidified product after draining and separation is fermented and decomposed to produce recycled products containing feed ingredients and fertilizer ingredients.

JP 2002-143862 A (Patent Document 7) describes a method for treating protein-containing wastewater, which includes a step of adding a protein-clotting enzyme to protein-containing wastewater (mainly milk protein) to coagulate the protein, a step of separating the coagulated protein from the liquid after treatment, and a step of biologically treating the liquid.

JP 2019-37955 A JP 2002-346306 A JP 2014-147859 A Japanese Patent Application Publication No. 3-127944 Japanese Patent Application Publication No. 4-27492 Japanese Patent Application Publication No. 3-93689 JP 2002-143862 A

However, Patent Document 1 does not describe an effective treatment method for wastewater that contains a large amount of organic nitrogen in addition to oil and SS. When performing solid-liquid separation on wastewater that contains a large amount of organic nitrogen, there is a problem that the adhesion of the flocs cannot be reduced, and the amount of cationic organic polymer coagulant injected becomes large. Similarly, Patent Document 2 does not take into consideration the problem of the adhesion of the flocs during solid-liquid separation. Furthermore, Patent Document 2 requires dehydration of the sediment using a separate dehydrator, the oil in the wastewater requires a separate floating treatment and is difficult to remove simultaneously with components such as BOD and SS, and the treatment process takes a long time, so there is still room for improvement in terms of efficiency.

In Patent Document 3, blood components and proteins are removed in separate tanks, so it cannot be said to be effective in terms of equipment size and efficiency. In addition, the flocculant used in Patent Document 3 is inorganic, and the adhesion of flocs during solid-liquid separation is not taken into consideration. Furthermore, Patent Document 3 has problems in that it includes many treatment methods with high running costs (microbubble treatment, ozone oxidation treatment, activated carbon treatment, etc.) and does not assume a specific treatment method for the removed solids. Patent Document 4 has problems in that it requires the combined use of heat treatment and pH adjustment to acidic conditions, the polymer flocculant is not cationic, the solid-liquid separation method is high-cost electric flotation separation and requires separate dehydration, and does not assume the simultaneous removal of oil in addition to SS and BOD in the wastewater treatment.

Patent Document 5 leaves room for further study in that it requires the addition of a coagulant, pH adjustment to acidic conditions, and the use of heat treatment in combination, that the coagulant is mainly inorganic, that it does not assume the simultaneous treatment of SS and oil in addition to soluble organic components, and that it does not consider the treatment or disposal method of concentrated sludge after solid-liquid separation methods (filtration and centrifugation).Patent Document 6 leaves room for further study in that it hardly assumes water treatment methods such as the simultaneous removal of oil, SS, and organic matter, that it uses an acid as a coagulant and does not assume a cationic organic polymer coagulant, that the warming (standing) time after heating and the draining and separation time are very long, and that it has a method for solid-liquid separation of the coagulated material.

Patent Document 7 focuses on wastewater containing milk proteins and soybean-derived proteins that are coagulated by enzymes, uses enzymes and their auxiliary components (metal salts) as coagulants, and does not consider cationic organic polymer flocculants, and while it considers the removal of nitrogen and phosphorus, it does not consider the removal of oil, SS, or organic components (including soluble matter). Thus, with conventional methods, it has been difficult to comprehensively solve the various problems associated with the treatment of wastewater that simultaneously contains oil, organic nitrogen, and SS.

Therefore, the present invention provides a wastewater treatment method and wastewater treatment device that can efficiently treat wastewater containing oil, organic nitrogen, and SS using simpler equipment.

As a result of intensive research conducted by the present inventors to solve the above problems, it was discovered that it is effective to carry out a modification process for modifying the organic nitrogen in the treated water, which contains oil, organic nitrogen, and SS.

In one aspect, an embodiment of the present invention, which has been completed based on the above findings, is a wastewater treatment method comprising a flocculation process in which a cationic organic polymer coagulant is added to water to be treated that contains oil, organic nitrogen, and SS to form flocs, a solid-liquid separation process in which the water to be treated in which the flocs have been formed is subjected to solid-liquid separation to obtain treated water, and a modification treatment process in which a modification treatment is performed on the water to be treated prior to the flocculation process so that at least the flocs formed in the flocculation process have the floc strength required for solid-liquid separation and the treated water obtained by solid-liquid separation has clarity.

In one embodiment of the wastewater treatment method according to the present invention, the weight ratio of organic nitrogen to SS (organic nitrogen/SS) in terms of nitrogen in the treated water is 0.1 or more.

In another embodiment of the wastewater treatment method according to the present invention, the molecular weight of the cationic organic polymer flocculant is 5 million or more, and the cationic degree is 50 mol% or more.

In another embodiment of the wastewater treatment method according to the present invention, the denaturation treatment process includes an acid treatment process in which an acid is added to the water to be treated to make it acidic, and a neutralization treatment process in which an alkaline agent is added to the water to be treated after the acid treatment process to neutralize it.

In another embodiment of the wastewater treatment method according to the present invention, the denaturation treatment process includes a surfactant addition process in which a surfactant is added to the neutral or acidic water to be treated.

In another embodiment of the wastewater treatment method according to the present invention, the denaturation treatment process includes a heat treatment process in which the temperature of the water to be treated is heated to 50°C or higher.

In another embodiment of the wastewater treatment method according to the present invention, an alkaline treatment step is performed in which an alkaline agent is added to the water to be treated to make it alkaline at a pH of 10 or higher.

In another aspect, the present invention provides a wastewater treatment device that includes a flocculation means having a flocculation tank in which a cationic organic polymer coagulant is added to water to be treated that contains oil, organic nitrogen, and SS to form flocs, a solid-liquid separation means for performing solid-liquid separation on the water to be treated in which flocs have been formed, to obtain treated water, and a modification treatment means for performing a modification treatment on the water to be treated before it flows into the flocculation means, so that at least the flocs formed in the flocculation tank have the floc strength required for solid-liquid separation, and the treated water obtained by the solid-liquid separation means has clarity.

In one embodiment, the wastewater treatment device according to the present invention further comprises an acquisition means for acquiring water quality information or image information of the water to be treated in the flocculation tank, a prediction means for predicting the water quality of the water to be treated in the flocculation tank based on the water quality information or image information acquired by the acquisition means, and a control means for controlling the injection amount of the cationic organic polymer flocculant based on the prediction result of the prediction means.

The present invention provides a wastewater treatment method and wastewater treatment device that can efficiently treat wastewater containing oil, organic nitrogen, and SS using simpler equipment.

FIG. 1 is a flow diagram showing an example of a wastewater treatment method according to an embodiment of the present invention. FIG. 4 is a flow diagram showing an example of a wastewater treatment method according to a first modified example of the present invention. FIG. 11 is a flow diagram showing an example of a wastewater treatment method according to a second modified example of the present invention. FIG. 11 is a flow diagram showing an example of a wastewater treatment method according to a third modified example of the present invention. FIG. 13 is a flow diagram showing an example of a wastewater treatment method according to a fourth modified example of the present invention. 1 is a schematic diagram showing an example of a wastewater treatment device according to an embodiment of the present invention. FIG. 4 is a schematic diagram illustrating an example of a wastewater treatment device according to a first modified example of the present invention. FIG. 11 is a schematic diagram illustrating an example of a wastewater treatment device according to a second modified example of the present invention. FIG. 13 is a schematic diagram illustrating an example of a wastewater treatment device according to a third modified example of the present invention. FIG. 13 is a schematic diagram illustrating an example of a wastewater treatment device according to a fourth modified example of the present invention. FIG. 2 is a cross-sectional view showing an example of a mechanical solid-liquid separation means according to an embodiment of the present invention. 1 is a schematic diagram illustrating an example of an operating condition support system for a wastewater treatment device according to an embodiment of the present invention.

The following describes the embodiments of the present invention with reference to the drawings. In the following description of the drawings, identical or similar parts are given the same or similar reference numerals. Note that the embodiments shown below are examples of devices and methods for embodying the technical idea of this invention, and the technical idea of this invention does not specify the structure, arrangement, etc. of the components as described below.

(Wastewater treatment method)
As shown in FIG. 1 , the wastewater treatment method according to the embodiment of the present invention includes a modification treatment step of modifying organic nitrogen in the water to be treated, a flocculation step of adding a cationic organic polymer flocculant to the modified water to be treated and mixing the same to form flocs, and a solid-liquid separation step of separating the water to be treated in which flocs have been formed into flocs and a separation liquid (treated water).

<Water to be treated>
The water to be treated is not particularly limited as long as it is wastewater containing oil, organic nitrogen, and SS. For example, wastewater generated in various factories such as slaughterhouses, meat processing facilities, meat processing plants, food processing plants, food manufacturing plants, fertilizer manufacturing plants, machine factories, and automobile factories can be mentioned. In addition, wastewater (e.g., kitchen wastewater) generated in various facilities such as shopping centers, restaurants, supermarkets, hotels, and hospitals can be mentioned. In addition, the water to be treated may contain oil, organic nitrogen, and organic or inorganic substances other than organic nitrogen. SS may be organic or inorganic.

Oil refers not only to oils that are liquid at room temperature, but also to fats that are solid at room temperature, i.e., all types of oils and fats. For example, oils include vegetable oils, animal oils, mineral oils, etc., and one or more of these oils may be contained. Furthermore, the state of oil in wastewater is that it is emulsified with water, or the water and oil are separated, or the above states are mixed. Generally, the oil concentration in wastewater is measured as a hexane extractable substance (JIS K0102:2019).

Organic nitrogen refers to the nitrogen components contained in organic matter, and includes, for example, proteins, amino acids, nucleic acids, amide compounds such as urea, and azo compounds. Total nitrogen is a combined item of organic nitrogen and inorganic nitrogen. Inorganic nitrogen is divided into ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen.

The organic nitrogen contained in the water to be treated is not particularly limited, and may include one or more of the above-mentioned proteins, amino acids, nucleic acids, amide compounds such as urea, or azo compounds. The water to be treated may also contain inorganic nitrogen at the same time. The organic nitrogen may be any of animal, vegetable, and artificially synthesized substances. Generally, the concentration of organic nitrogen in wastewater is measured as the value obtained by subtracting ammonia nitrogen from Kjeldahl nitrogen.

The water to be treated may contain organic matter. The organic matter may contain all of the above-mentioned oil or organic nitrogen and organic matter other than the above-mentioned oil or organic nitrogen, or may contain the above-mentioned oil or organic nitrogen as well as organic matter other than the above-mentioned oil or organic nitrogen. Examples of organic matter include one or more types of organic matter such as carbohydrates, proteins, lipids, nucleic acids, vegetable oils, animal oils, mineral oils, alcohols, fatty acids, surfactants, and paints. The organic matter may be a substance derived from animal or vegetable oils or a chemically synthesized substance. It may be a substance manufactured from the above-mentioned substance or a decomposition product of the above-mentioned substance. The organic matter contained in the water to be treated according to this embodiment is not particularly limited, but may further contain inorganic matter.

SS (Suspended Solids) refers to solid suspended matter suspended in wastewater, and is the material that remains on filter paper with a pore size of 1 μm when filtered through filter paper. SS includes inorganic and organic substances. Inorganic SS includes soil-derived components and clay components. Organic SS includes components derived from the cells of animals, plants, and microorganisms, and from factories. The SS contained in the treated water of this embodiment is not particularly limited, but it contains a large amount of SS derived from animal meat pieces, oil, and blood components.

The temperature of the water to be treated is not particularly limited, but is preferably 5°C to 55°C, and can be 20°C to 50°C. When heat treatment is used in the denaturation treatment step described below, the temperature is preferably 50°C to 70°C, and more preferably 55°C to 70°C. If the temperature of the water to be treated is low and the temperature is lower than the melting point of the oil contained in the water, the oil may become solid, and the treatment may be insufficient. In addition, if the water temperature is extremely high, the components containing organic nitrogen may be excessively denatured, and the treatment may be insufficient when acid treatment, surfactant treatment, or alkali treatment is selected as the denaturation treatment. Conversely, when heat treatment is selected as the denaturation treatment, it is necessary to heat the water to be treated appropriately to denature the components containing organic nitrogen. Therefore, it is necessary to set the water temperature within an appropriate range.

When the ratio of organic nitrogen and SS in the treated water, which contains oil, organic nitrogen, and SS, is large, the adhesion of the flocs does not decrease even if a cationic organic polymer flocculant is added to perform flocculation treatment in the flocculation process, and poor flocculation and separation may occur. In this embodiment, by performing a modification treatment to impart the floc strength required for solid-liquid separation of flocs to the treated water, particularly for the treated water in which the weight ratio of organic nitrogen (in nitrogen equivalent) to SS (organic nitrogen/SS) contained in the treated water is 0.1 or more, the adhesion of the flocs can be weakened and the floc strength can be improved, so that poor flocculation in the subsequent flocculation process and poor separation in the solid-liquid separation process can be suppressed, and treated water with clarity can be obtained. If the modification treatment is not performed, the adhesion of the flocs becomes very strong, the amount of chemicals added increases, poor floc formation occurs, solid-liquid separation cannot be performed sufficiently, and the clarity of the treated water may be impaired.

In one embodiment, the weight ratio of organic nitrogen (in nitrogen equivalent) to SS (organic nitrogen/SS) is preferably 0.1 or more, more preferably 0.15 or more, and even more preferably 0.18 or more. The higher the weight ratio of organic nitrogen (in nitrogen equivalent) to SS (organic nitrogen/SS), the higher the adhesion of the flocs in the floc formation process. Therefore, there is no particular upper limit, but the weight ratio of organic nitrogen (in nitrogen equivalent) to SS (organic nitrogen/SS) can be 5 or less, further 3 or less, further 1.5 or less, and even further 0.5 or less.

The ratio of organic nitrogen (in nitrogen equivalent) to COD _Mn contained in the water to be treated (organic nitrogen/COD _Mn ) is preferably 0.1 or more. There is no particular upper limit, but the ratio of organic nitrogen (in nitrogen equivalent) to COD _Mn (organic nitrogen/COD _Mn ) is preferably 3 or less, more preferably 1.5 or less, and even more preferably 0.5 or less.

In addition, the ratio (organic nitrogen/n-Hex) of the organic nitrogen (nitrogen equivalent) and the oil concentration (n-Hex) contained in the water to be treated is preferably 0.5 or more. There is no particular upper limit, but the ratio (organic nitrogen/n-Hex) of the organic nitrogen (nitrogen equivalent) and the oil concentration (n-Hex) is preferably 5 or less, more preferably 3 or less, and even more preferably 2 or less. The range of n-Hex contained in the water to be treated is typically 150 mg/L or more and 7,000 mg/L or less, more typically 170 mg/L or more and 6,500 mg/L or less, and even more preferably 1,000 mg/L or more and 6,500 mg/L or less. The water to be treated suitable for this embodiment has a relatively high ratio of organic nitrogen to SS, COD _Mn , and n-Hex. By subjecting such treated water to the modification treatment process according to this embodiment, the flocculation effect and separation property can be enhanced, and treated water with clarity can be obtained. This makes it possible to efficiently treat wastewater containing oil, organic nitrogen, and SS using simpler equipment.

<Cationic organic polymer flocculant>
-kinds-
The cationic organic polymer flocculant can be one or more selected from homopolymers or copolymers of cationic monomers, copolymers of cationic monomers and nonionic monomers, copolymers of cationic monomers and anionic monomers, etc. In this embodiment, the term "organic polymer" is used to clearly distinguish it from inorganic flocculants such as polyaluminum chloride and polyferric sulfate, but it is generally simply called a polymer flocculant.

As the cationic monomer, one or more selected from dialkylaminoalkyl (meth)acrylates or their neutralized salts, tertiary salts, or quaternary salts can be used. For example, dimethylaminoethyl (meth)acrylate or their neutralized salts, tertiary salts, or quaternary salts can be used. Among these, a quaternary salt of dimethylaminoethyl (meth)acrylate is preferred, and an ammonium salt is more preferred.

As the nonionic monomer, one or more selected from (meth)acrylamide, N,N-dimethyl(meth)acrylamide, (meth)acrylonitrile, vinyl acetate, etc. can be used. As the anionic monomer, one or more selected from (meth)acrylic acid, sodium (meth)acrylate, itaconic acid, maleic acid, fumaric acid, 2-(meth)acrylamide-methylpropanesulfonic acid, and metal salts or ammonium salts thereof can be used.

Note that (meth)acrylate is a concept that includes both acrylate and methacrylate, (meth)acrylic acid is a concept that includes both acrylic acid and methacrylic acid, and (meth)acrylamide is a concept that includes both acrylamide and methacrylamide.

In addition to non-amidine polymer flocculants, amidine polymer flocculants having amidine units can be used as cationic organic polymer flocculants, and polymer flocculants that are mixtures of amidine polymer flocculants and non-amidine polymer flocculants can also be used.

The form of the cationic organic polymer flocculant is not particularly limited, and examples include powder and liquid (dispersion, emulsion), etc.

-Cationicity-
Although the type of raw material monomer and the form of the organic polymer are not limited, this embodiment uses an organic polymer containing 50 mol% or more of cationic monomer in all monomer units, that is, a cationic organic polymer flocculant having a cationic degree of 50 mol% or more. That is, the cationic organic polymer flocculant used in this embodiment is produced by polymerizing raw material monomers containing 50 mol% or more of cationic monomer, and the amount of cationic monomer is more preferably 60 mol% or more, even more preferably 70 mol% or more, and particularly preferably 80 mol% or more.

In addition, a cationic organic polymer flocculant consisting essentially of cationic monomers (100 mol%) can also be used. The cationic degree can be defined as the proportion (mol%) of cationic monomers contained in the raw monomers of the organic polymer.

In general, oils and other substances contained in wastewater are finely dispersed in the wastewater by surfactants and alkaline components, and the surfaces of the oil particles are negatively charged. Compared to the zeta potential of general pollutants, the zeta potential of oil particles is significantly lower, and even if a normal cationic organic polymer flocculant is added, flocs are not formed, or even if flocs are formed, they are not strong enough to withstand mechanical solid-liquid separation.

On the other hand, when a cationic organic polymer flocculant with a cationic degree of 50 mol% or more is added and mixed, the highly positively charged (high positive charge density) molecular chains capture the oil finely dispersed in the wastewater, forming strong flocs that can withstand mechanical solid-liquid separation.

--Molecular weight--
The molecular weight of the cationic organic polymer flocculant is not particularly limited, but it is preferably 5 million or more, more preferably 6 million or more, particularly 7 million or more, and of these, preferably 8 million or more. Note that this molecular weight is a value measured and calculated by the intrinsic viscosity method, and the details of the measurement and calculation methods are described on pages 112 to 116 of "Polymer Flocculant Usage Guide" (published by Tokyo Metropolitan Sewerage Service Co., Ltd. in March 2002).

Because the oil in the wastewater is finely dispersed throughout the wastewater, adding a normal cationic organic polymer flocculant makes it difficult to form flocs, or even if flocs are formed, they are not strong enough to withstand mechanical solid-liquid separation. On the other hand, if a cationic organic polymer flocculant with a cationic degree of 50 mol% or more and a molecular weight of 5 million or more is used, the long molecular chains can capture the oil that is finely dispersed throughout the wastewater, forming stronger flocs that can withstand mechanical solid-liquid separation.

-viscosity-
From the same viewpoint as the molecular weight, the characteristics of the cationic organic polymer flocculant can also be defined by the solution viscosity. Specifically, the viscosity of the aqueous solution when the cationic organic polymer flocculant is dissolved in pure water at 1 g/L is preferably 100 mPa·s or more, more preferably 120 mPa·s or more, and particularly preferably 150 mPa·s or more.

When the cationic organic polymer flocculant is dissolved in pure water at 2 g/L, the viscosity of the aqueous solution is preferably 200 mPa·s or more, more preferably 220 mPa·s or more, and particularly preferably 250 mPa·s or more.

The above viscosity values, regardless of whether the concentration is 1 g/L or 2 g/L, are values measured at 25°C and a rotation speed of 60 min ^-1 using a B-type viscometer and spindle SB2 described in Appendix 1 (reference) of JIS K7117-1:1999. The spindle is also called the rotor.

-solvent-
The cationic organic polymer flocculant is preferably used as a flocculant solution dissolved or dispersed in a solvent. The solvent is not particularly limited, but can be selected from, for example, one or more of pure water (including distilled water), tap water, industrial water, groundwater, various wastewater treatment water, seawater, etc. From the viewpoint of maximizing the flocculating power of the cationic organic polymer flocculant, it is preferable to use pure water or tap water. On the other hand, from the viewpoint of economic efficiency, it is preferable to use industrial water, groundwater, and various wastewater treatment water. However, the above are examples and are not limited to these.

-Injection concentration-
Whether the cationic organic polymer flocculant is diluted or not, the amount of cationic organic polymer flocculant (active ingredient) injected is preferably from 1 mg/L to 500 mg/L, more preferably from 5 mg/L to 400 mg/L, and particularly preferably from 10 mg/L to 300 mg/L.

<Acid>
In the modification treatment step, the acid is used to make the pH of the water to be treated acidic and to modify the water to be treated, which contains organic nitrogen, SS, and oil.

The type of acid is not particularly limited, but inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and boric acid are commonly used. In particular, the use of sulfuric acid is preferred due to problems in maintaining and managing the reaction tank. An inorganic coagulant may be added before or at the same time as the addition of the pH adjuster. Types of inorganic coagulants that can be used include aluminum sulfate, polyaluminum chloride (PAC), aluminum chloride, polyferric sulfate (polyferric iron), ferric sulfate, ferric chloride, or mixtures of these. The use of an inorganic coagulant may make it possible to reduce the amount of cationic organic polymer coagulant used.

In the denaturation treatment step, it is preferable to add an acid to the water to be treated to create acidic conditions, thereby denaturing and coagulating components containing organic nitrogen, such as proteins, in the water to be treated. The denaturation and coagulation of organic nitrogen facilitates the subsequent formation of flocs. In addition, water to be treated with a high organic nitrogen ratio exhibits the effect of preventing the adhesion of flocs during the subsequent flocculation step from decreasing significantly in handleability.

<Surfactant>
Surfactants are used in the denaturation treatment process to denature the water to be treated, which contains organic nitrogen, SS, and oil. Surfactants are broadly classified into ionic surfactants and nonionic surfactants. Ionic surfactants are further classified into anionic surfactants, cationic surfactants, and amphoteric surfactants.

There are no particular limitations on the type of surfactant, but anionic surfactants are preferred. Specific examples include sodium fatty acid, potassium fatty acid, sodium alpha sulfo fatty acid ester, sodium linear alkylbenzene sulfonate, sodium alkyl sulfate, sodium alkyl ether sulfate, sodium alpha olefin sulfonate, sodium alkyl sulfonate, and sodium lauryl sulfate. There are no particular limitations on the surfactant used, but sodium lauryl sulfate (sodium dodecyl sulfate) is preferred.

In the denaturation treatment process, a surfactant is added to the water being treated, and components in the water being treated, such as proteins and other organic nitrogen-containing components, are denatured into a form that is favorable for floc formation and solid-liquid separation. The denaturation of organic nitrogen and other components facilitates the subsequent floc formation with a cationic organic polymer flocculant. In addition, water being treated with a high organic nitrogen ratio exhibits the effect of preventing the flocs from becoming highly sticky during the subsequent floc formation process, and a significant decrease in handleability.

There are no particular limitations on the form of the surfactant, such as solid or liquid, but it can be diluted or dissolved in a solvent before injection. It can also be injected in powder form or as is.

<Alkaline agent>
The alkaline agent is used in the modification treatment step to modify the treated water containing organic nitrogen, SS, and oil, or for neutralization in the neutralization treatment step.

Types of alkaline agents include sodium hydroxide, magnesium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, calcium carbonate, potassium carbonate, magnesium carbonate, sodium hydrogen carbonate, ammonium hydroxide, ammonium carbonate, or hydrates of these. There are no particular limitations on the alkaline agent used, but sodium hydroxide is preferred.

In the denaturation treatment process, an alkaline agent is added to the water being treated, which denatures the components in the water, such as proteins and other organic nitrogen-containing components. Denaturation of the organic nitrogen facilitates the subsequent formation of flocs. In addition, water being treated with a high organic nitrogen ratio produces flocs that are highly sticky during the subsequent flocculation process, which is effective in preventing a significant decrease in handleability.

<Other drugs>
This embodiment does not limit the use of any agent other than the above-mentioned agent and cationic organic polymer flocculant. Specifically, before adding the cationic organic polymer flocculant, one or more agents such as a known inorganic flocculant or an organic polymer coagulant (a flocculant having a lower molecular weight than the cationic organic polymer flocculant) can be added.

Examples of inorganic coagulants that can be used include aluminum sulfate, polyaluminum chloride (PAC), aluminum chloride, polyferric sulfate (polyferric iron), ferric sulfate, ferric chloride, or mixtures of these. Examples of organic polymer coagulants include condensation polyamines, dicyandiamide-formaldehyde condensates, polyethyleneimine, polyvinyl imidaline, polyvinyl pyridine, diallylamine salt-sulfur dioxide copolymers, polydimethyl diallyl ammonium salts, polydimethyl diallyl ammonium salt-sulfur dioxide copolymers, polydimethyl diallyl ammonium salt-acrylamide copolymers, polydimethyl diallyl ammonium salt-diallyl amine hydrochloride derivative copolymers, and allylamine salt polymers.

Specific examples of condensation polyamines include condensates of alkylene dichloride and alkylene polyamine, condensates of aniline and formalin, condensates of alkylene diamine and epichlorohydrin, and condensates of ammonia and epichlorohydrin. Examples of alkylene diamines that condense with epichlorohydrin include dimethylamine, diethylamine, methylpropylamine, methylbutylamine, and dibutylamine.

(Modification process)
In the modification treatment step shown in Fig. 1, the organic nitrogen components contained in the inflowing treated water, which contains oil, organic nitrogen, and SS, are modified. The purpose of this step is a pretreatment step for forming good flocs in a short time and improving the water quality of the separated liquid in the subsequent flocculation step.

Conventional flocculation by adding only cationic organic polymer flocculants could treat oil and SS, but when the content of organic nitrogen in addition to oil and SS increases in the water being treated, problems such as the occurrence of floc stickiness and an increase in the amount of chemicals added become evident. According to this embodiment, by carrying out a modification treatment process before the flocculation process, it is possible to suppress the occurrence of floc stickiness and reduce the amount of chemicals added.

As shown in FIG. 2, the denaturing treatment process may include an acid treatment process in which an acid is added to the water to be treated to make it acidic, and a neutralization treatment process in which an alkaline agent is added to the water to be treated after the acid treatment process to neutralize it. Alternatively, as shown in FIG. 3, a surfactant addition process may be included in which a surfactant is added to the water to be treated. Alternatively, as shown in FIG. 4, a heat treatment process may be included in which the water to be treated is heated to a temperature of 50° C. or higher. Alternatively, as shown in FIG. 5, an alkali treatment process may be included in which an alkaline agent is added to the water to be treated to make it alkaline to a pH of 10 or higher.

In the acid treatment process and neutralization process shown in FIG. 2, acid is injected into the water to be treated to make the water acidic, and the organic nitrogen components are denatured, and then an alkaline agent is injected to perform neutralization. The pH of the acidic condition is preferably 5 or less, more preferably 4 or less, and even more preferably 3.5 or less, more preferably 1 or more, and even more preferably 2 to 3. The pH during neutralization is preferably 6 to 7.5, more preferably 6 to 7, and even more preferably 6.5 to 7.

In the surfactant addition step shown in FIG. 3, a denaturing treatment is performed by injecting a surfactant into the water to be treated. The concentration of the surfactant injected (relative to purity) is preferably 50 mg/L to 300 mg/L, more preferably 100 mg/L to 250 mg/L, and particularly preferably 150 mg/L to 200 mg/L. In the surfactant addition step, it is preferable to add the surfactant under neutral conditions, preferably acidic conditions, and even more preferably after adjusting the pH to 5 to 7, or even weakly acidic conditions of 5 to 6.

The heat treatment process shown in FIG. 4 performs denaturation treatment by heating the water to be treated. The water temperature after heat treatment is preferably 50°C or higher and 80°C or lower, and more preferably 55°C or higher and 70°C or lower. In addition, the water temperature in methods other than heat treatment is preferably 5°C or higher and 55°C or lower, and more preferably 20°C or higher and 50°C or lower.

In the alkaline treatment process shown in FIG. 5, an alkaline agent is injected into the water to be treated, and the water is denatured by creating alkaline conditions. The pH of the alkaline conditions is 10 or higher. In addition, in any of the denaturation treatment processes described above, it is preferable to provide a mixing process after the chemical injection, although there are no particular restrictions.

In the modification treatment step, when stirring and mixing is performed using a stirring device or the like, the stirring speed is not particularly limited, but is preferably 20 min ⁻¹ or more and 300 min ⁻¹ or less (times/min), more preferably 30 min ⁻¹ or more and 200 min ⁻¹ or less, and particularly preferably 40 min ⁻¹ or more and 150 min ⁻¹ or less.

It is preferable to shorten the time required for treatment by subjecting the water to the denaturation treatment process, i.e., the residence time in the equipment involved in the denaturation treatment process, to a relatively short period of time. The residence time of the water in the denaturation treatment process is preferably 1 minute or more and 30 minutes or less, more preferably 3 minutes or more and 20 minutes or less, and particularly preferably 5 minutes or more and 15 minutes or less.

To check the pH of the water to be treated, it is preferable to install a pH measuring means for the water to be treated before and after pH adjustment. An example of a pH adjustment means is a pH measuring device that continuously measures pH. In particular, a pH meter that can transfer and record the results in a separate recording device is preferable.

(Flocculation process)
In the flocculation process, a cationic organic polymer flocculant is injected into and mixed with the water to be treated that has been treated in the modification process to form flocs. Specifically, a cationic organic polymer flocculant is injected into and mixed with the water to be treated that has passed through the above-mentioned modification process. Through the above process, components in the water to be treated, such as oil, organic nitrogen, SS, and organic matter, react with the cationic organic polymer flocculant to form flocs. Furthermore, through the formation of flocs, the components that have been captured by the flocs are separated as a separated liquid.

When the materials are stirred and mixed by a stirring blade or the like in the flocculation step, the stirring speed is not particularly limited, but is preferably from 20 min ⁻¹ to 300 min ⁻¹ (times/min), more preferably from 30 min ⁻¹ to 200 min ⁻¹ , and particularly preferably from 40 min ⁻¹ to 150 min ⁻¹ .

This flocculation step is preferably divided into two or more steps, a high-speed stirring step and a low-speed stirring step. High-speed stirring means that the stirring speed of the stirring blade is 200 min ^-1 (revolutions/min) or more, and low-speed stirring means that the stirring speed is slower than 200 min ^-1 (revolutions/min). In the high-speed stirring step, the cationic organic polymer flocculant is uniformly dispersed and mixed by high-speed stirring. In the low-speed stirring step, flocs are grown by low-speed stirring.

The residence time required to allow flocs to grow sufficiently in the treated water varies depending on the type and conditions of the equipment, but in this embodiment, for example, the residence time in the equipment involved in floc growth is preferably 1 minute or more and 30 minutes or less, more preferably 3 minutes or more and 20 minutes or less, and particularly preferably 5 minutes or more and 15 minutes or less.

There are no particular restrictions on the water temperature during the flocculation process, but except for heat treatment, it is preferably 5°C to 55°C, more preferably 20°C to 50°C. If heat treatment is used, it is preferably 55°C to 70°C.

In the flocculation process, it is also possible to inject the cationic organic polymer flocculant into the water to be treated in two or more separate injections. It is also possible to inject one or more inorganic flocculants into the water to be treated, either alone or together with the above-mentioned cationic organic polymer flocculant, and then inject further cationic organic polymer flocculant into the water to be treated after the injection. When an inorganic flocculant is injected, it is preferable that the injection position is upstream of the injection position of the cationic organic polymer flocculant.

By forming flocs, oil and SS in particular are removed from the treated water as flocs, and organic nitrogen and organic matter are also removed at the same time. Furthermore, by forming flocs with low adhesion and high floc strength, handling in the subsequent stages is greatly improved.

(Solid-liquid separation process)
In the solid-liquid separation step, the flocs formed in the flocculation step and the separated liquid are separated into solid and liquid by mechanical means (mechanical solid-liquid separation step). Specifically, the apparatus has a mechanical solid-liquid separation means. The water to be treated containing the flocs formed in the flocculation step is supplied to the mechanical solid-liquid separation means and separated into flocs and separated liquid by solid-liquid separation. During the separation, the flocs are concentrated and dehydrated at the same time, and the water generated during the process is also separated as separated liquid.

By using a mechanical solid-liquid separation means in the solid-liquid separation process, the flocs after solid-liquid separation do not need to be dehydrated using a separate dehydrator, and the solid-liquid separation time can be shortened. The method of disposing of the flocs after mechanical solid-liquid separation is not particularly limited, but examples include industrial waste disposal, raw material for methane fermentation, reforming as fuel for combustion or incineration, fuel additive during incineration, separating and extracting specific oils from oil flocs, and using as fertilizer. The separated liquid may be subjected to separate physicochemical or biological treatment, but if the regulated components in the treated water have been treated to a satisfactory concentration, it can also be discharged as treated water after disinfection.

According to the wastewater treatment method of the embodiment of the present invention, by carrying out a modification treatment step for modifying the organic nitrogen components in the water to be treated before the flocculation step, it is possible to reduce the increase in floc adhesion in the flocculation step, and to perform treatment more efficiently and stably than in the past while suppressing problems such as floc adhesion to equipment such as the coagulation tank, the coagulation tank agitator, and piping. The modification treatment step can exert its effect in a relatively short treatment time of about 30 minutes at most, so the treatment time can also be shortened.

(Wastewater treatment equipment)
As shown in FIG. 6 , a wastewater treatment device according to an embodiment of the present invention includes a modification treatment means 1 for modifying organic nitrogen in water to be treated that contains oil, organic nitrogen, and SS, a flocculation means 2 for adding and mixing a cationic organic polymer coagulant to the modified water to be treated and forming flocs in a flocculation tank 21, and a solid-liquid separation means 3 for performing solid-liquid separation of the water to be treated in which flocs have been formed into flocs and a separated liquid.

(Modification Treatment Means 1)
The modification treatment means 1 performs a treatment of modifying the organic nitrogen in the water to be treated in the modification treatment tank 11 by any of the following methods. Specifically, the modification treatment means 1 can change its device form depending on the mode of the modification treatment. The number of treatment tanks used as the modification treatment means 1 is not particularly limited. In addition, the modification treatment performed by the modification treatment means 1 may be a combination of one or more of the modification treatments shown below. When a chemical is injected into the modification treatment means 1 for the modification treatment, a stirring device can be provided to thoroughly mix the water to be treated with the chemical. The stirring device is not particularly limited, but examples thereof include a stirring blade. In addition, the shape, size, number, etc. of the stirring device are not particularly limited.

As shown in FIG. 7, the denaturation treatment means 1 according to one embodiment can include an acid treatment means 1a and a neutralization treatment means 1b. The acid treatment means 1a includes an acid treatment tank 12, an agitation device 12a for agitating the acid treatment tank 12, an acid storage tank 13, and an acid injection device (not shown) for injecting acid from the acid storage tank 13 into the acid treatment tank 12. In the acid treatment means 1a, an acid treatment process is performed in which acid is added from the acid storage tank 13 to the water to be treated, and the water to be treated in the acid treatment tank 12 is made acidic.

The neutralization means 1b includes a neutralization tank 14, an agitation device 14a for agitating the neutralization tank 14, an alkaline agent storage tank 15, and an alkaline agent injection device (not shown) for injecting an alkali from the alkaline agent storage tank 15 into the neutralization tank 14. In the neutralization means 1b, an alkaline agent is added from the alkaline agent storage tank 15 to the water to be treated after the acid treatment step by the acid treatment means 1a, and neutralization is performed.

As another embodiment of the denaturation treatment means 1, as shown in FIG. 8, a surfactant treatment means 1c for adding a surfactant to the water to be treated can be provided. The surfactant treatment means 1c includes a surfactant treatment tank 16, a surfactant storage tank 17, a surfactant injection device (not shown), and an agitation device 16a. The water to be treated flows into the surfactant treatment tank 16, and the surfactant is injected from the surfactant storage tank 17 by the surfactant injection device, mixed by the agitation device 16a, and denatured by the surfactant. In addition to being injected into the surfactant treatment tank 16, the surfactant can also be injected into the flocculation tank 21. Also, an injection point may be provided in the piping between the surfactant treatment tank 16 and the flocculation tank 21, and the surfactant may be injected from the injection point.

As yet another embodiment of the denaturation treatment means 1, as shown in FIG. 9, a heat treatment means 1d for heat-treating the temperature of the water to be treated can be provided. The heat treatment means 1d includes a heat treatment tank 18, a heat treatment device 19, and an agitator 18a. The water to be treated flows into the heat treatment tank 18, is heated by the heat treatment device 19, is mixed by the agitator 18a, and is denatured by heating. The heat treatment device 19 is not particularly limited, but examples include an electric heater, steam, and a heat pump.

As another embodiment of the denaturing treatment means 1, as shown in FIG. 10, an alkaline treatment means 1e for adding an alkaline agent to the water to be treated can be provided. The alkaline treatment means 1e includes an alkaline treatment tank 111, an alkaline agent storage tank 112, an alkaline agent injection device (not shown), and an agitation device 111a. The water to be treated flows into the alkaline treatment tank 111, an alkaline agent is injected from the alkaline agent storage tank 112 by the alkaline agent injection device, the water is mixed by the agitation device 111a, and the water is denatured by the alkaline agent. There are no particular limitations on the location where the alkaline agent is injected, and any of the following locations may be selected as long as it is before the cationic organic polymer flocculant is injected: the alkaline treatment tank 111, between the alkaline treatment tank 111 and the subsequent flocculation tank 21, or the subsequent flocculation tank 21.

(Flock forming means 2)
The flocculation means 2 injects and mixes a cationic organic polymer flocculant into the water to be treated that has passed through the modification treatment means 1. Specifically, it comprises a flocculation tank 21, a dissolution tank 22, a cationic organic polymer flocculant injector (not shown), and an agitator 21a. The specific configuration of these devices is not particularly limited, and it is sufficient that the cationic organic polymer flocculant is injected into the water to be treated in the flocculation tank 21 and mixed therein.

Two or more flocculation tanks 21 may be installed. When the flocculation tank 21 is a single tank as shown in FIG. 6, it is preferable that the agitator 21a has high-speed and low-speed agitation functions. Alternatively, two or more agitators each having high-speed or low-speed agitation functions may be installed. When the flocculation tank 21 is two or more tanks, it is also possible to install an agitator 21a having high-speed or low-speed agitation functions in each flocculation tank 21. There are no particular limitations on the number or arrangement of these flocculation tanks 21 and agitators 21a. In addition, when using a chemical other than a cationic organic polymer flocculant, it is preferable to install a chemical injection device for each chemical.

After the denaturation treatment, the water to be treated flows into the flocculation tank 21, and the cationic organic polymer flocculant supplied from the dissolution tank 22 is injected into the flocculation tank 21 by an injection device. The water to be treated and the cationic organic polymer flocculant are mixed by the agitation device 21a. The dissolution tank 22 is not particularly limited, and it is sufficient if it can dilute or dissolve the cationic organic polymer flocculant with a solvent and store it. In addition, an agitation device (not shown) for dilution or dissolution may be provided in the dissolution tank 22.

(Solid-liquid separation means 3)
As the solid-liquid separation means 3, various devices can be used as long as they are a solid-liquid separation device 31 for performing solid-liquid separation into flocs and separated liquid from the floc-containing water to be treated that has flowed in from the flocculation tank 21, and such devices can be used, including gravity settling treatment equipment, pressure flotation devices, mechanical solid-liquid separation devices, etc. Among these, in particular, the use of a mechanical solid-liquid separation device that mechanically separates the water to be treated into solid and liquid by pressurization, centrifugal force, reduced pressure (vacuum exhaust), or a combination of these can improve the efficiency of wastewater treatment.

As the mechanical solid-liquid separation device, for example, a concentrator conventionally used for sludge thickening or a dehydrator used for sludge treatment can be used. The concentrator is not particularly limited, but for example, a screw concentrator, a belt concentrator, a centrifugal concentrator, an elliptical plate concentrator, etc. can be used alone or in combination. The dehydrator is not particularly limited, but the same type of device as that used for further dehydration after solid-liquid separation described below can be used.

Figure 11 is an example of a partial cross-sectional view of a mechanical solid-liquid separation device when a mechanical solid-liquid separation device is used as the solid-liquid separation device 31. The mechanical solid-liquid separation device has a floc moving means 35 that continuously processes flocs. The floc moving means 35 has, for example, a belt driving means 32 such as a rotating roll, and a belt 36 stretched around the belt driving means 32, and the separation liquid containing flocs supplied from the flocculation tank 21 is supplied onto the belt 36 through an inlet 33 at the top of the device.

Part or all of the belt 36 is made of filter cloth, and the water in the flocs 9 is separated into solid and liquid as it moves, the separated liquid is captured by the capture means 34 below the belt, and the separated flocs (sludge) are discharged from the discharge port 39. After discharging the flocs, the belt 36 returns to the inlet 33 side, and flocs are supplied again, but before returning to the inlet side, cleaning water from the belt cleaning means 37 may be sprayed to wash the belt 36.

The mechanical solid-liquid separation device in FIG. 11 is suitable for continuous processing of the separated liquid containing flocs, but more preferably, a pressurizing means 41 is installed. The pressurizing means 41 is a device that pressurizes (squeezes) the flocs 9, and has, for example, one or more pressurizing plates 42 arranged just before the discharge outlet 39.

The pressure plate 42 is inclined from the vertical plane toward the inlet 33, and there is a gap between its lower end and the belt 36. As the flocks 9 pass through the gap, they are pressed against the belt 36 by the pressure plate 42 and compressed (squeezed). The pressure applied at this time can be adjusted by changing one or more of the pressure conditions, which are the size of the gap, the inclination angle and number of the pressure plates 42, the movement speed and supply amount of the flocks, etc.

The pressure means 41 is not limited to the pressure plate 42, and pressure members of other shapes such as pressure rolls may be used. In either case, the pressure means 41 can efficiently reduce the moisture content of the flocs. The pressure applied to the flocs 9 can be changed appropriately depending on the device and solid-liquid separation conditions, but is preferably 200 kPa or less, particularly preferably 1 kPa to 150 kPa, more preferably 1 kPa to 100 kPa, more preferably 10 kPa or more, even more preferably 15 kPa or more, and particularly preferably 20 kPa or more. The pressure can be adjusted by the pressure conditions of the pressure plate 42, and in the case of a screw press dehydrator, the internal pressure can be adjusted by adjusting the screw rotation speed and the opening of the outlet.

In this embodiment, the flocculation tank 21 and the solid-liquid separation device 31 are separate devices, but a device that simultaneously performs the flocculation process and the solid-liquid separation process, such as a centrifugal dehydrator, can also be used. Furthermore, the flocs after solid-liquid separation from the water to be treated can be further dehydrated using a dehydrator used for sludge treatment, etc. The dehydrator used for this dehydration is not particularly limited, and any dehydrator that has been used conventionally for sludge dehydration can be used. Specifically, a screw press dehydrator, belt press dehydrator, centrifugal dehydrator, multiple disk type dehydrator, multiple disk type screw press dehydrator, rotary pressure dehydrator, vacuum dehydrator, elliptical disk type dehydrator, etc. can be used.

The wastewater treatment device according to the embodiment of the present invention is equipped with a modification treatment means 1, which allows the organic nitrogen components in the water to be treated to be modified into a form suitable for treatment by the flocculation means 2. The modification treatment means 1 does not require a particularly complicated configuration, and a relatively small device is sufficient for short-term treatment. Therefore, the wastewater treatment device according to the embodiment of the present invention can provide a wastewater treatment device that can efficiently treat wastewater containing oil, organic nitrogen, and SS using simpler equipment.

The present invention has been described using the above embodiments, but the descriptions and drawings that form part of this disclosure should not be understood as limiting this invention. In other words, this disclosure is not limited to the above-mentioned embodiments, and it is of course possible to combine and modify the components to embody the present invention without departing from the spirit of the present disclosure.

For example, FIG. 12 shows an example of an operating condition support system that optimizes the operating conditions of each piece of equipment using the wastewater treatment equipment shown in FIGS. 6 to 11. This operating condition support system includes a denaturing treatment means 1, a flocculation means 2, a solid-liquid separation means 3, an acquisition means 4 that acquires water quality information or image information of the water to be treated in the flocculation tank 21, a prediction means 7 that predicts the water quality of the water to be treated in the flocculation tank 21 based on the water quality information or image information acquired by the acquisition means 4, and a control means 5 that controls the injection amount of a cationic organic polymer flocculant based on the prediction result of the prediction means 7.

As the acquisition means 4, various devices capable of acquiring the state of the water to be treated in the flocculation tank 21 can be used. For example, water quality measuring devices such as a pH meter, BOD meter, COD meter, MLSS meter, colorimeter, turbidity meter, transparency meter, and absorptiometer for measuring the quality of the water to be treated, a particle counter for measuring the number of particles in the water to be treated in the flocculation tank 21, and a sensor or camera for acquiring an image of the suspended state of particles in the flocculation tank 21 can be used. The water quality information or image information acquired by the acquisition means 4 is output from the control means 5 to the prediction means 7, for example, via the network 6.

The prediction means 7 receives raw water information, water quality information or image information of the water to be treated in the flocculation tank 21, water quality information of the treated water related to the water quality information or image information, and operating condition information of the wastewater treatment device, all of which have been obtained over a specific period of time in the past (e.g., several years), and predicts the future state inside the flocculation tank 21 by water quality analysis or image diagnosis. Examples of raw water information include pH, hexane extractable substance concentration, SS, COD _Mn , BOD, organic nitrogen concentration, organic nitrogen concentration/SS ratio, organic nitrogen concentration/COD _Mn ratio, organic nitrogen concentration/n-Hex ratio, etc. Examples of operating condition information include the type and injection amount of cationic organic polymer flocculant, modification treatment conditions, and the type and addition amount of chemicals used in the modification treatment, etc. Examples of water quality information for the treated water include water quality information for the water to be treated in the flocculation tank 21, clarity evaluation information showing the evaluation result of the clarity of the treated water after solid-liquid separation treatment, hexane extractable substance concentration, SS (SS removal rate), COD _Mn (COD _Mn removal rate), BOD (BOS removal rate), organic nitrogen concentration, water content of dewatered sludge, etc. The prediction means 7 stores raw water information, water quality information or image information for the water to be treated in the flocculation tank 21, water quality information for the treated water, and operating condition information for the wastewater treatment equipment as one combination of teacher data, and accumulates a sufficient amount of data for the combination as actual values in a storage means (not shown).

The prediction means 7 predicts the future water quality of the treated water in the flocculation tank 21 and the treated water after solid-liquid separation treatment after a specific period of time based on the real-time water quality information or image information acquired by the acquisition means 4 and the teacher data stored in the memory means. For example, if the predicted water quality of the treated water after solid-liquid separation or the water quality of the treated water in the flocculation tank 21 does not meet a predetermined standard, a prediction model of operation change conditions is created in which the operating conditions are optimized, such as adjusting the injection amount of polymer flocculant, so that the water quality of the treated water meets the standard. The creation of the prediction model is not limited to the following, but can be performed by, for example, supervised learning using a known machine learning algorithm such as a neural network, and by optimizing the weighting function between neurons in the neural network.

The control means 5 receives information on the operation change conditions from the prediction means 7, and controls at least one of the injection device (not shown) that injects the cationic organic polymer flocculant from the dissolution tank 22, the acid injection device that injects acid from the acid storage tank 13 to the acid treatment tank 12, or the alkaline agent injection device that injects the alkaline agent from the alkaline agent storage tank 15 to the neutralization tank 14, thereby adjusting the injection amount of at least one of the cationic organic polymer flocculant, the acid, and the alkaline agent. Similarly, the control means 5 can automatically control the injection amount of the pH adjuster, the injection amount of the inorganic flocculant, the amount of the water to be treated, the rotation speed of the agitator, and whether or not it rotates.

According to the operating condition support system shown in FIG. 12, by being equipped with an acquisition means 4, a control means 5, and a prediction means 7, it becomes possible to treat wastewater containing oil, organic nitrogen, and SS more efficiently, with fewer treatment problems, and stably for a long period of time.

The following examples of the present invention are presented together with comparative examples, but these examples are provided to provide a better understanding of the present invention and its advantages, and are not intended to limit the invention.

In this example, the treatment water containing oil, organic nitrogen, and SS was denatured, and a cationic organic polymer flocculant was injected to form flocs. The floc shapes after solid-liquid separation were visually observed, and the water quality of the separated liquid (treated water) was analyzed, and the treatment performance of the wastewater treatment method according to the embodiment of the present invention was examined.

<Test Method>
In the test, wastewater from a meat processing plant was obtained as wastewater containing oil, organic nitrogen, and SS. Four types of wastewater (wastewater A, wastewater B, wastewater C, and wastewater D) were obtained by changing the time of collection. For comparison, five types of general oil-containing wastewater (wastewater E, wastewater F, wastewater G, wastewater H, and wastewater I) were also obtained. Note that the wastewaters shown in Tables 1 and 2 include wastewaters that do not show the effects of this embodiment in the following description, but all of these wastewaters are examples of wastewaters that are effective in the treatment of this embodiment.

Examples of water that contains oil, organic nitrogen, and SS and has a high organic nitrogen/SS ratio and can be used in this embodiment are shown in Table 1. The pH of wastewater A, wastewater B, wastewater C, and wastewater D were 6.6, 6.7, 6.6, and 6.6, respectively, the organic nitrogen was 242 mg/L, 265 mg/L, 233 mg/L, and 222 mg/L, respectively, the hexane extractable substances (hereinafter, n-Hex) were 266 mg/L, 174 mg/L, 290 mg/L, and 362 mg/L, respectively, and the suspended solids (hereinafter, SS) were 1,170 mg/L, 900 mg/L, 980 mg/L, and 1,230 mg/L, respectively. The COD _Mn was 838 mg/L, 737 mg/L, 810 mg/L, and 833 mg/L, respectively, and the BOD was 2,620 mg/L, 1,920 mg/L, 2,360 mg/L, and 2,230 mg/L, respectively. The organic nitrogen/SS ratios of wastewater A, B, C, and D were in the range of 0.18 to 0.29, and all were above 0.1. The organic nitrogen/n-Hex ratios were all above 0.5.

Details of typical oil-containing wastewater are shown in Table 2. These are examples of wastewater quality typically obtained from food processing plants and dairy product manufacturing plants, and show examples of wastewater from different industries and raw material components. The organic nitrogen/SS ratio is less than 0.1. In addition, the organic nitrogen/COD _Mn ratio and organic nitrogen/n-Hex ratio are both lower than the target wastewater of this example, and show examples with low organic nitrogen content.

The water quality items pH, n-Hex, SS, COD _Mn , and BOD were measured in accordance with the Sewage Testing Method (issued by the Japan Sewage Works Association, Sewage Testing Method). Organic nitrogen was calculated by subtracting the measured value of ammonia nitrogen from the measured value of Kjeldahl nitrogen. The measurement methods for Kjeldahl nitrogen and ammonia nitrogen were in accordance with the Sewage Testing Method.

The physical properties of the cationic organic polymer flocculant used in the test are shown in Table 3. Oil separating agent a was used as the cationic organic polymer flocculant. Oil separating agent a (polyacrylic acid ester type, molecular weight 9 million, rotational viscosity 372 mPa·s, cationic degree 85 mol%) was dissolved in pure water and used at a dissolved concentration of 20 g/L.

<Test procedure>
- Basic procedure -
(1) Wastewater was placed in a beaker and the pH was adjusted with an aqueous sulfuric acid solution or an aqueous sodium hydroxide solution.
(2) A cationic organic polymer flocculant (hereinafter, referred to as oil separating agent a) was added little by little to the wastewater after the pH adjustment, and the mixture was stirred with a spatula to generate flocs.
(3) The state of the reactive flocs and the appearance of the underlying water (hereinafter referred to as treated water) were visually confirmed to determine the appropriate dosage of chemicals and pH.
(4) The quality of the treated water was measured with the appropriate amount of chemicals. The concentrated reaction flocs (concentrated sludge) were dehydrated by pressing the reaction flocs on the sieve with a pressure plate.
(5) The dewatered flocs (= concentrated sludge) were dried (105°C, overnight) and the moisture content was measured.

- Procedure when using an acid denaturation treatment step -
In the acid denaturation treatment, the wastewater was denatured by adjusting it to the acidic side (pH 2-4) using hydrochloric acid or sulfuric acid as step (1), and stirred with a magnetic stirrer for about 10 minutes until the water surface was slightly rippling. Next, an alkaline agent was added to neutralize the wastewater to a near neutral pH (pH 6-7), and the test was carried out according to steps (2) to (4) above.

- Procedure when using a denaturing treatment step with a surfactant -
In examining the surfactant dosage, 0 mg/L, 100 mg/L, 150 mg/L, and 200 mg/L of sodium dodecyl sulfate (hereinafter, SDS) was added to the wastewater, and the pH was adjusted to 5 as in procedure (1), and then tests were carried out according to the above procedures (2) to (4). In addition, in order to examine the effect of the denaturation treatment process using a surfactant and the pH of the water to be treated, the pH of the wastewater was adjusted to 5, 5.5, 6, 7, and 8 using hydrochloric acid, sulfuric acid, and sodium hydroxide in the pH adjustment procedure in (1) above, and 150 mg/L of SDS was added, and then tests were carried out according to the above procedures (2) to (4).

- Procedure when using a denaturing treatment step by heat treatment -
Wastewater (250 mL or 500 mL) was placed in a beaker and immersed for 30 minutes to 1 hour in thermostatic baths with heating temperatures of 20 to 25° C. (no heating), 50° C., 55° C., and 60° C. After the wastewater was returned to room temperature, tests were carried out according to the above procedures (2) to (4).

- Procedure when using a denaturing treatment step using alkali treatment -
In the study of pH adjustment by alkaline treatment, the pH of the wastewater was adjusted to each of the conditions of 5, 6.3, 7, 8, 9, and 10 in the procedure (1), and then tests were carried out in the procedures (2) to (4) above.

- Procedures for testing organic nitrogen content and content ratio -
For wastewaters E and G, in which the organic nitrogen concentration was less than 120 mg/L and the organic nitrogen/SS ratio was less than 0.1, the pH was adjusted to 7 using an aqueous sodium hydroxide solution in the procedure (1), and tests were conducted in accordance with the procedures (2) to (4) above.

<Method of determining reactive flocs>
The size of the flocs was measured with a ruler. The strength of the flocs was judged based on whether the flocs did not crumble or whether they crumbled and dispersed when pressed with a spatula. When the flocs had a certain degree of strength and were not easily crumbled when pressed, they were rated as "floc strength: present." When the flocs had weak strength and were easily crumbled and dispersed when pressed, they were rated as "floc strength: weak."

The adhesion of the flock was evaluated by visually checking whether it adhered to the spatula or the wall of the beaker when pressed with a spatula, and was judged as follows:
A: No adhesion B: Weak adhesion, can be peeled off with light pressure using a spatula C: Difficult to judge between B and D D: Strong adhesion, cannot be peeled off immediately with a spatula

In addition, the feasibility of mechanical solid-liquid separation was judged by satisfying three criteria: floc size: 1 mm or more, floc strength: strong, and floc adhesion: within the range of A to C.

<Method for determining the clarity of treated water>
The clarity of the treated water was visually confirmed and judged as follows. When it was difficult to judge one of the following criteria, it was judged as "○-◎". In this example, ◎ and ○ were judged as the applicability of this example.
◎: Transparent, low turbidity, and high visibility ○: Slightly turbid but almost transparent, slight turbidity, but high visibility to a certain extent △: Compared to the raw water, it can be seen that the turbidity has been gradually removed, but the turbidity is high and visibility is low ×: High turbidity and low visibility (close to the raw water state)

The color of the treated water, the hexane extractable substance removal rate, the SS removal rate, the COD _Mn removal rate, and the BOD removal rate were evaluated by measuring the water quality of the treated water before the modification treatment and the water quality of the treated water according to the Sewage Testing Method (published by the Japan Sewage Works Association, Sewage Testing Method).

<Test Results>
Example 1: Study of modification treatment in case of neutralization treatment after acid modification treatment
The results of the treatment test are shown in Table 4. As shown in Examples 1-1 to 1-3, when the pH after the modification treatment was set to 2 or 3, the amount of oil separating agent a injected could be reduced, and the state of the reaction flocs was also good. In Examples 1-1 to 1-3, the hexane extract removal rate was 96 to 98% or more, the SS removal rate was 93 to 96%, and the BOD removal rate was 73 to 79%, all of which were high, and it was possible to simultaneously remove oil, SS, and organic matter. No significant differences were observed in the amount of chemical injection, the state of the flocs, or the quality of the treated water, whether the pH after neutralization was 6 or 7. The sludge water content in Examples 1-2 and 1-3 was 86.7% and 85.1%, respectively.

In Example 1-4, in which the pH after modification treatment was 4, the amount of oil separating agent a was slightly larger, the COD _Mn removal rate was slightly lower than in Examples 1-1 to 1-3, and the color was slightly higher, but the state of the reaction flocs and the clarity of the treated water were good. According to Example 1, it was found that the adhesion of the flocs could be reduced and the size and strength of the flocs could be improved by adding an acidic condition, more specifically, a pH of 5 or less, or even less than pH 4, or even a pH of 2 to 3, through modification treatment, and then neutralizing the condition to a neutral condition of pH 6 to 7. This improved the quality of the treated water and made mechanical solid-liquid separation possible.

Example 2: Using a denaturing treatment step with a surfactant
(1) Study on the amount of surfactant injected The results of the treatment test are shown in Table 5. In Comparative Example 2-1, in which no modification treatment was performed, the amount of oil separating agent a injected was small, and the state of the reactive flocs was relatively good, but the clarity of the treated water showed almost no change, and good results were not obtained. As shown in Examples 2-1 to 2-3, the amount of oil separating agent a injected increased with an increase in the amount of SDS injected. However, the state of the flocs improved with the increase in the amount of SDS injected. The clarity of the treated water improved with the increase in the amount of SDS injected, but no extreme change in each removal rate was confirmed with the increase in the amount of injection. According to Example 2 , it can be seen that by adding about 100 to 200 mg/L of SDS , or even about 120 to 170 mg/L, after adjusting the pH to the acidic side, the flocs were made into a state in which solid-liquid separation was possible, and the quality of the treated water was improved.

(2) Effect of pH adjustment The treatment test results are shown in Table 6. As the adjusted pH value increased, the injection amount of oil separating agent a increased. In Examples 2-4, 2-5, and 2-6, under the condition of adjusted pH value of 5 to 6, the state of the flocs did not change, and no significant change in the treated water quality was confirmed. In Example 2-7, when the adjusted pH was 7, the state of the flocs and the SS removal rate, the COD _Mn removal rate, and the BOD removal rate were not different from those in Examples 2-4 to 2-6, but the color increased. In Comparative Example 2-2, where the adjusted pH value was 8, flocs were not generated well, and the clarity of the treated water also deteriorated. From the above results, it was confirmed that in the denaturation treatment by adding a surfactant, it is preferable to add SDS after adjusting the adjusted pH to 5 to 7, or even to a weakly acidic condition of 5 to 6.

Example 3: When a denaturing treatment step by heat treatment is used
The results of the treatment test are shown in Table 7. As the heating temperature increased, the chromaticity of the treated water decreased and the COD _Mn removal rate improved. In Comparative Examples 3-1 and 3-2, in which no modification treatment by heating was performed, the size of the reactive flocs was insufficient or the strength was poor, making efficient treatment by mechanical solid-liquid separation difficult, and the clarity was also inferior to that of Examples 3-1 to 3-3. Comparing Example 3-1 and Example 3-2, the injection amount of the oil separating agent a, the state of the flocs, and the clarity of the treated water were about the same. However, the chromaticity of the treated water was greatly improved in Example 3-2. In addition, although the injection amount of the oil separating agent a in Example 3-3 was slightly increased, the adhesion of the flocs was improved more than in Example 3-2, and it was confirmed that the chromaticity of the treated water decreased and the COD _Mn removal rate improved. From the above results, it was confirmed that the heat modification treatment under conditions of a heating temperature of 50°C or higher, more preferably 55°C or higher, improves the quality of the treated water while making the flocs into a state in which solid-liquid separation is possible.

Example 4: In the case of using a denaturing treatment step by alkali treatment
In Comparative Examples 4-1 to 4-5, as the pH increased, the clarity of the treated water improved, but the amount of oil separating agent a injected increased, and the tendency for the stickiness of the reactive flocs to increase was confirmed. In particular, when the pH was set to 8 or 9, it could not be said that the modification treatment for imparting the floc strength required for solid-liquid separation to the flocs obtained in the flocculation step was properly performed, and a thread-like product with very strong stickiness was generated, making solid-liquid separation impossible. On the other hand, in Example 4-1, although the amount of oil separating agent a injected was large, the stickiness of the flocs was reduced, and the clarity of the treated water was good. According to this Example 4, the condition under which the state of the flocs and the clarity of the treated water were all good by pH adjustment alone was only the condition of pH 10. Therefore, it was confirmed that by adjusting the pH of the water to be treated to 10 by adding an alkaline agent and adding the oil separating agent a, reactive flocs could be well formed, efficient treatment by mechanical solid-liquid separation was also possible, and good results were obtained for the quality of the treated water.

Example 5: Impact of conventional oil-containing wastewater treatment
The results of the treatment test are shown in Table 9. The reactive flocs in Examples 5-1 and 5-2 had good floc shapes and little floc adhesion under near-neutral conditions. The clarity of the treated water was good, and the hexane extractable substance removal rate was high at 98% or more. From the above results, it was confirmed that good treatment is possible by using the oil separating agent a according to this embodiment for normal oil-containing wastewater with an organic nitrogen/SS ratio of less than 0.1. It is considered that treated water of even better water quality can be obtained by further carrying out the organic nitrogen modification treatment according to this embodiment according to the required water quality of the treated water.

1: Modification treatment means
1a: Acid treatment means
1b: Neutralization means
1c: Surfactant treatment means
1d: Heat treatment means
1e: Alkaline treatment means
2: Floc forming means
3: Solid-liquid separation means
4. Acquisition method
5: Control means
6. Network
7. Prediction methods
11: Flocculation tank
11a, 12a, 14a, 16a, 18a, 21a: Stirring device
12: Acid treatment tank
13: Acid storage tank
14: Neutralization tank
15: Alkaline agent storage tank
16: Surfactant treatment tank
17: Surfactant reservoir
18: Heat treatment tank
19: Heat treatment device
21: Flocculation tank
22: Dissolution tank
31: Solid-liquid separation device
32: Belt drive means
33: Insert port
34: Capture means
35: Flock Movement Method
36: Belt
37: Belt cleaning means
39: Exhaust port
41: Pressurizing means
42: Pressure plate
111: Alkaline treatment tank
111a: Stirring device
112: Alkaline agent storage tank

Claims (9)

a flocculation step of adding a cationic organic polymer flocculant to the water to be treated, which contains oil, organic nitrogen, and SS, to form flocs;
a solid-liquid separation step of subjecting the water to be treated in which the flocs have been formed to solid-liquid separation to obtain treated water;
a denaturing treatment step of performing a denaturing treatment on the water to be treated prior to the flocculation step so that at least the flocs formed in the flocculation step have a floc strength required for the solid-liquid separation and the treated water obtained by the solid-liquid separation has clarity,
The wastewater treatment method, wherein the denaturation treatment step includes a surfactant addition step of adding 50 to 300 mg/L of a surfactant to the neutral or acidic water to be treated . a flocculation step of adding a cationic organic polymer flocculant to the water to be treated, which contains oil, organic nitrogen, and SS and has a weight ratio of organic nitrogen to SS (organic nitrogen/SS) of 0.1 to 3 in terms of nitrogen, to form flocs;
a solid-liquid separation step of subjecting the water to be treated in which the flocs have been formed to solid-liquid separation by a mechanical solid-liquid separation means to obtain treated water;
a modification treatment step of performing a modification treatment on the water to be treated prior to the flocculation step so that at least the flocs formed in the flocculation step have a floc strength required for the solid-liquid separation and the treated water obtained by the solid-liquid separation has clarity;
having
The denaturing treatment step includes:
an acid treatment step of adding an acid to the water to be treated so that the pH of the water to be treated is 2 to 3;
a neutralization step of adding an alkaline agent to the water to be treated after the acid treatment step to neutralize the water to have a pH of 6 to 7;
A wastewater treatment method comprising the steps of: a flocculation step of adding a cationic organic polymer flocculant to the water to be treated, which contains oil, organic nitrogen, and SS and has a weight ratio of organic nitrogen to SS (organic nitrogen/SS) of 0.1 to 3 in terms of nitrogen, to form flocs;
a solid-liquid separation step of subjecting the water to be treated in which the flocs have been formed to solid-liquid separation by a mechanical solid-liquid separation means to obtain treated water;
a denaturing treatment step in which the water to be treated is denatured before the flocculation step so that at least the flocs formed in the flocculation step have a floc strength required for the solid-liquid separation and the treated water obtained by the solid-liquid separation has clarity;
having
The wastewater treatment method, wherein the denaturing treatment step includes an alkaline treatment step of adding an alkaline agent to the water to be treated to make the water to be treated alkaline at a pH of 10 or higher. 4. The wastewater treatment method according to claim 2, wherein a surfactant is added to the water to be treated in the denaturing treatment step. 2. The wastewater treatment method according to claim 1, wherein the weight ratio of organic nitrogen to SS (organic nitrogen/SS) in terms of nitrogen in the water to be treated is 0.1 or more and 3 or less . 5. The wastewater treatment method according to claim 1, wherein the cationic organic polymer flocculant has a molecular weight of 5,000,000 or more and a cationic degree of 50 mol % or more. 7. The wastewater treatment method according to claim 1 , wherein the denaturing treatment step includes a heat treatment step of heating the water to a temperature of 50° C. or higher. a flocculation means including a flocculation tank for adding a cationic organic polymer flocculant to the water to be treated, the cationic organic polymer flocculant being added ... cationic organic polymer flocculant to form f
a solid-liquid separation means for performing solid-liquid separation of the water to be treated in which the flocs have formed, to obtain treated water;
a modification treatment means for performing a modification treatment on the water to be treated before flowing into the flocculation means so that at least the flocs formed in the flocculation tank have a floc strength required for the solid-liquid separation and the treated water obtained by the solid-liquid separation means has clarity ;
a surfactant adding means for adding a surfactant to the water to be treated at 50 to 300 mg/L for the purpose of the denaturing treatment of the water to be treated;
A wastewater treatment device comprising: an acquiring means for acquiring water quality information or image information of the water to be treated in the flocculation tank;
a prediction means for predicting the water quality of the water to be treated in the flocculation tank based on the water quality information or the image information acquired by the acquisition means; and
The wastewater treatment device according to claim 8, further comprising: a control means for controlling an injection amount of the cationic organic polymer flocculant based on a prediction result of the prediction means.