WO2007102379A1

WO2007102379A1 - Apparatus for treating organic waste water containing microbiologically degradable matters and treatment method

Info

Publication number: WO2007102379A1
Application number: PCT/JP2007/053799
Authority: WO
Inventors: Yuji Senda; Norio Yamada; Robert Masahiro Serikawa
Original assignee: Ebara Corporation
Priority date: 2006-02-28
Filing date: 2007-02-28
Publication date: 2007-09-13
Also published as: JP2007229565A; JP4956016B2

Abstract

It is intended to provide a low cost method, whereby waste water is treated in a manner fitting for organic matters contained therein by taking the advantage of an electrochemical treatment method, and an apparatus therefor. First, untreated waste water (1) is introduced into a biological treatment step (a biological treatment device) (2) wherein highly biologically degradable matters are separated and removed to give biologically treated water (3) containing a large amount of hardly biologically degradable matters. Next, this biologically treated water (3) is introduced into an electrolysis step (an electrolysis tank) (4) wherein the hardly biologically degradable matters are degraded into highly biologically degradable matters such as VFA, carbon dioxide, water, etc. and the water is discharged as electrolyzed water (5). A portion of this electrolyzed water (5) is returned into the biological treatment step (the biological treatment device) (2) as returned electrolyzed water (6) and the highly biologically degradable matters contained in the returned electrolyzed water (6) are biologically treated.

Description

Specification

Processing equipment and processing method for organic wastewater containing hardly biodegradable substances

[0001] The present invention relates to a treatment apparatus and treatment method for organic wastewater containing a hardly biodegradable substance.

Background art

[0002] Wastewater or waste liquid is discharged from private industrial facilities, public facilities, third sector facilities, etc. in various forms such as aqueous solutions, slurries, emulsions, micelles, suspensions, concentrated liquids, sludge mixed liquids, etc. Yes. These effluents or effluents must be rendered harmless by water treatment before being discharged into public waters. The most commonly used water treatment method for waste water or waste liquid is biological treatment. Biological treatment is widely used for a long time because the treatment cost is relatively low. Biological treatment is broadly divided into aerobic treatment and anaerobic treatment. The former is mainly used when the chemical oxygen demand (CODCr) of wastewater is several tens to several thousand mg / L or less, and the latter is mainly used when CODCrl000 mg / L or more of wastewater. In addition, denitrification treatment cannot be completed by aerobic treatment or anaerobic treatment alone in human waste treatment or sewage treatment. For this reason, there is a case where a combination of an aerobic biological treatment and an anaerobic biological treatment is used by virtue of the characteristics of both.

[0003] However, it has drainage containing chemical substances or chemically synthesized substances derived from petrochemicals, and has hard walls and cell walls such as organic sludge or methane fermentation sludge from sewage treatment plants. It may be difficult to apply biological treatment to wastewater that contains many substances with low biodegradability, such as when cells are contained. In addition, even a naturally occurring substance such as lignin and humin may be very low in biodegradability when it is a polymer having a benzene ring functional group in the molecule.

[0004] Furthermore, if a pigment component is contained in the wastewater, such as dyed wastewater, biological treatment may be extremely difficult. Since pigment components are generally difficult to biodegrade to microorganisms, when wastewater containing pigment components is subjected to biological treatment, even if CODCr and BOD can be removed sufficiently, chromaticity cannot be obtained. There is. [0005] Generally and in the present specification, the "refractory biodegradable substance" refers to a substance that is difficult to biodegrade.

[0006] As a method for treating such a hardly biodegradable substance, an electrochemical treatment method has been proposed. The electrochemical treatment method is relatively easy to control and can be treated with equipment on a small scale compared to biological treatment. In recent years, a treatment method using a conductive diamond electrode has attracted attention as an example of a method for electrochemically treating an organic substance dissolved in water. Conductive diamond electrodes have the same characteristics as conventional noble metal electrodes. When a DC voltage is applied to the conductive diamond electrode in water, the water is oxidized at the anode to generate hydroxy radicals (OH radicals). Since this OH radical has a very high oxidation ability, almost all organic substances can be decomposed into carbon dioxide and water. Conventional noble metal electrodes have very low generation efficiency of OH radicals. However, it has been shown in the literature that OH radicals can be generated very efficiently when a conductive diamond electrode is used. (Ghrar dim et A1 .: Electrochemical Oxidation of 4-chlorophenol for wastewater treatment, J. Electrochemical Society, 148, D78—D82, 2001).

[0007] In water treatment with a conductive diamond electrode, the theoretical amount of electricity required to decompose organic matter contained in 1 L of organic wastewater equivalent to CODCrlg / L by electrolytic treatment (hereinafter, the theoretical amount of electricity, Is about 3.4Ah / g-CODCr. When conducting an electrolytic reaction, the cell voltage of the conductive diamond electrode should be at least 4-5V. Although it depends on the operating current density, the electrolyte temperature, and the electrical conductivity of the drainage, an example of a typical operating value of the cell voltage (voltage between electrodes of a single electrolytic cell) is about 7V. Therefore, the power required to decompose the organic matter contained in 1 L of organic wastewater equivalent to CO DCrlg / L by electrolytic treatment is 3.4Ahx7V = 23.8VAh. This value has a problem that the treatment cost is higher than that of biological treatment equivalent to approximately 24 Wh / g_CODCr or 24 kWh / kg-CODCr.

[0008] In general, organic wastewater contains a hardly biodegradable substance and an easily biodegradable substance. When direct electrolysis is performed on such wastewater, for example, OH radicals generated by electrolysis using a conductive diamond electrode are non-selectively distinguished between readily biodegradable substances and hardly biodegradable substances. Oxidation treatment of organic matter is performed. Because of this, biodegradation Even in the treatment of the active substance, electrolytic treatment with a high treatment cost is applied. As a result, processing costs may increase.

Disclosure of the invention

Problems to be solved by the invention

[0009] An object of the present invention is to provide a low-cost treatment method and apparatus in accordance with the properties of organic substances contained in wastewater, taking advantage of the characteristics of the electrochemical treatment method.

Means for solving the problem

[0010] As a result of intensive studies, the present inventors first biologically treated a readily biodegradable substance, and then electrolytically treated the hardly biodegradable substance using a conductive diamond electrode. In addition, wastewater containing easily biodegradable substances and hardly biodegradable substances can be treated with lower power than in the case of electrolytic treatment alone; It was found that biodegradable substances such as organic acids (volatile fatty acids (VFAs), hereinafter referred to as VFA) are produced as intermediate products of molecules, and the biodegradability of treated water is improved. That is, in the electrolytic treatment process, the organic matter is subjected to electrolytic treatment with an electric power that does not lead to complete decomposition of carbon dioxide and water to obtain electrolytic treated water containing an easily biodegradable substance. By returning a part to the biological treatment process and performing biological treatment, it is possible to further reduce the cost of the electrolytic treatment and reduce the cost of the entire treatment process. In addition, when the biological treatment process is anaerobic treatment, there is an advantage that the amount of biogas generated is increased by increasing the load of easily biodegradable substances introduced into the biological treatment process.

[0011] A first aspect of the present invention includes a biological treatment apparatus, an electrolytic treatment tank that is located downstream of the biological treatment apparatus and includes a conductive diamond electrode, and at least water discharged from the electrolytic treatment tank. An organic wastewater treatment apparatus containing a hardly biodegradable substance, comprising a return line for returning a part to the biological treatment apparatus.

[0012] A second aspect of the present invention is a biological treatment apparatus, an electrolytic treatment tank located downstream of the biological treatment apparatus and provided with a conductive diamond electrode, and a concentrating device located downstream of the electrolytic treatment tank. And an organic wastewater treatment apparatus containing a hardly biodegradable substance, and a return line for returning at least a part of the concentrated water from the concentration apparatus to the biological treatment apparatus. [0013] A third aspect of the present invention includes a biological treatment device, a concentration device located downstream of the biological treatment device, and a conductive diamond electrode located downstream of the concentrated water side of the concentration device. An organic wastewater treatment apparatus containing a hardly biodegradable substance, and a return line for returning effluent water from the electrolytic treatment tank to the biological treatment apparatus.

[0014] The fourth aspect of the present invention is a biological treatment step of biologically treating an organic wastewater containing a hardly biodegradable substance to obtain biologically treated water, and the biological treatment using a conductive diamond electrode. An organic material containing a hardly biodegradable substance, comprising: an electrolytic treatment step of electrolytically treating at least a part of water to obtain electrolytically treated water; and a return step of returning at least a portion of the electrolytically treated water to the biological treatment step. This is an effluent treatment method.

[0015] In a fifth aspect of the present invention, a biological treatment step of biologically treating an organic wastewater containing a hardly biodegradable substance to obtain biologically treated water, and the biological treatment using a conductive diamond electrode. An electrolytic treatment step of electrolytically treating water to obtain electrolytically treated water; a concentration step of concentrating the electrolytically treated water to obtain concentrated water; and a returning step of returning at least a part of the concentrated water to the biological treatment step; The organic waste water treatment method containing a hardly biodegradable substance.

[0016] A sixth aspect of the present invention is a biological treatment step of biologically treating an organic wastewater containing a hardly biodegradable substance to obtain biologically treated water, concentrating the biologically treated water, A concentration step for obtaining the electrolyzed water, an electrolysis step for electrolyzing at least a portion of the concentrated water using a conductive diamond electrode to obtain electrolyzed water, and a return step for returning the electrolyzed water to the biological treatment step. The organic waste water treatment method containing a hardly biodegradable substance.

[0017] In any of the embodiments, it is preferable to provide an electric amount of 10 to 90% of the theoretical electric amount in the electrolytic treatment step.

[0018] Hereinafter, the present invention will be described in detail.

[0019] According to the present invention, a biological treatment step of biologically treating organic wastewater containing a hardly biodegradable substance to obtain biologically treated water, and electrolytic treatment by electrolyzing at least a part of the biologically treated water There is provided an organic wastewater treatment method containing a hardly biodegradable substance, comprising: an electrolytic treatment step for obtaining water; and a return step for returning at least a part of the electrolytic treatment water to the biological treatment step.

[0020] Wastewater that can be treated by the organic wastewater treatment method of the present invention includes a sewage treatment plant and a water treatment plant. Mixed sludge from the barber shop; various sludges such as methane fermentation processes; wastewater from waste oil refineries and petroleum products; wastewater from wastewater from chemical factories; wastewater from wastewater from chemical manufacturing plants; wastewater from wastewater from pharmaceutical manufacturing plants and hospitals; semiconductor processes ( Photoresist process, cleaning process, plating process) Wastewater; Waste liquid; Photodevelopment waste liquid; Various used cutting oil (oil-based and water-soluble) waste liquid of machining factory; Washing water for painting processes at can factories, car body factories, sheet metal factories'drainage; wastewater from agricultural chemical manufacturing processes · wastewater; dyeing wastewater; dyestuff wastewater; ion exchange regeneration wastewater from power plants (condemi wastewater); contains organic matter and ammonia Examples include the plating waste liquid and plating washing water of the plating factory. However, the present invention is not limited to these, and other than these, it can be applied to wastewater that is difficult to treat effectively with biological treatment alone.

[0021] The biological treatment process of the present invention may be a biological treatment usually performed in the wastewater treatment field.

Specifically, an aerobic biological treatment process or an anaerobic biological treatment process can be mentioned. An appropriate biological treatment process can be used according to the properties of the organic waste water to be treated.

[0022] The aerobic biological treatment method that can be used in the present invention is not particularly limited. For example, it may be a floating type activated sludge treatment method (a sludge floats in an aeration tank) that is a standard aerobic biological treatment, or a biofilm filtration method in which microorganisms are immobilized on a membrane. . Further, the aerobic biological treatment may be performed by aerobic microorganisms immobilized on a carrier such as activated carbon, anthracite (coal-based carbon) or sand. Further, as a floatation variation, a method may be used in which microorganisms are immobilized using a granular or sponge-like hydrophilic polymer or activated carbon as a carrier. Further, it may be a catalytic oxidation type aerobic biological treatment in which microorganisms are immobilized on a string-like, net-like or honeycomb-like carrier. Alternatively, it may be a rotating disk type aerobic biological treatment that takes in oxygen directly from the air without performing air aeration. Rotating disc type aerobic biological treatment is a disk on which a sponge or the like is attached, the upper half of which is exposed in the air from the drainage, and this disk rotates directly from the air. This is an aerobic biological treatment method characterized by oxygen uptake into wastewater.

[0023] The anaerobic biological treatment system that can be used in the present invention may be a standard 20-day methane fermentation, or a high-temperature methane fermentation operated at a temperature of about 55 ° C. Moyore. In the case of high-temperature methane fermentation, the speed of biological treatment There is an advantage that the interval can be shortened to 10-15 days. In the present invention, as biological treatment, the UASB method (Upflow Anaerobic Sludge Blanket) in which granules (granulated methane-fermenting bacteria are granulated) or the EGSB method (EGSB method capable of higher speed and high load operation) Expand ed Granular Sludge Bed) can also be adopted. When these anaerobic treatments are performed as biological treatments in the present invention, there is an advantage that energy recovery can be performed in the form of methane gas.

In the present invention, in the biological treatment process, the readily biodegradable substance in the organic wastewater is biologically treated and removed. Therefore, the biodegradable substances present in the organic wastewater remain mainly in the biologically treated water obtained in the biological treatment process. This biologically treated water is then sent to the electrolytic treatment step for electrolytic treatment. The electrolytic treatment process of the present invention is characterized by using a conductive diamond electrode. The conductive diamond electrode that can be used in the present invention may be a conductive diamond electrode having any configuration known in the art. For example, a conductive diamond thin film is deposited on the surface of a conductive metal material such as nickel (Ni), tantalum (Ta), titanium (Ή), molybdenum (Mo), tungsten (W), or zirconium (Zr) as an electrode substrate. A conductive diamond electrode formed by depositing a conductive diamond thin film on the surface of a semiconductor material such as a silicon wafer as an electrode substrate, and a deposited conductive polycrystalline diamond in the form of a plate Examples thereof include conductive diamond electrodes. The conductive diamond thin film is provided with conductivity by doping a predetermined amount of a dopant such as boron or nitrogen when forming a diamond thin film on a substrate. As a dopant, boron is generally used. In the present invention, a conductive diamond electrode may be used for both the anode and the cathode, or a conductive diamond electrode may be used only for the anode.

In the electrolytic treatment process of the present invention, the density of OH radicals generated in the conductive diamond electrode can be controlled by the current density applied to the conductive diamond electrode. In the electrolytic treatment process, several different current densities may be applied depending on the CODCr concentration of the wastewater to be treated. In this case, high current density is given to wastewater with high CODCr concentration, while low current density is given to wastewater with low CODCr concentration. Therefore, excessive generation of OH radicals can be prevented. In this way, the consumption of the conductive diamond electrode by OH radicals can be reduced, the life of the electrode can be extended, and the electric power can be saved.

[0026] In the electrolytic treatment step, the temperature of the waste water contacting the conductive diamond electrode is 40 ° C to 95 ° C, preferably 60 ° C to 85 ° C. The electrical conductivity is temperature dependent, and the higher the temperature, the higher the electrical conductivity. When the electrical conductivity is increased, the required voltage can be kept low, so the above range is preferable. Ability to capture heat from an external heat source to maintain the electrolytic treatment temperature within the above range. Efficient use of heat generated as the temperature of wastewater rises due to electrolysis using a conductive diamond electrode It is more preferable to do. In particular, it is desirable to install heat exchangers at the inlet and outlet of the electrolytic cell so that heat can be exchanged so that the heat generated in the electrolytic cell can be reused efficiently.

[0027] In the electrolytic treatment process, organic substances in the wastewater to be treated are neutralized to carbon dioxide and water, and a large amount of easily biodegradable low-molecular intermediate products such as VFA are used as intermediate products. This increases the biodegradability of the wastewater. In electrolysis using a conductive diamond electrode, in order to obtain electrolyzed water containing a large amount of readily biodegradable substances, the quantity of electricity is 10 to 90% of the theoretical quantity of electricity (3.4Ah / g-CODCr), preferably A 30 to 80% electric charge may be applied.

[0028] In order to easily estimate the biodegradability of electrolyzed water, BOD / COD Cr or pH in the electrolyzed water can be measured. BOD / CODCr force S The higher the S, the higher the biodegradability of all organic matter. Therefore, although it depends on the properties of the raw wastewater, it is desirable to perform the electrolytic treatment in the electrolytic treatment process so that the BOD / CODCr value S0.3 or higher, more preferably 0.4 or higher, in the electrolytically treated water. In addition, the pH decreases when the proportion of VFA is high. Although it depends on the composition of the raw wastewater, it can be considered that the pH value is low and the VFA concentration is high, that is, the electrolyzed water contains a lot of readily biodegradable substances.

In the present invention, at least a part of the electrolytically treated water is returned to the biological treatment process. Electrolytic treatment Return the entire amount of water to the biological treatment process. The amount of electrolyzed water that is returned to the biological treatment process varies depending on various factors such as the initial concentration of organic matter in the raw wastewater, the allowable concentration of the electrolyzed water, and the treatment capacity of the biological treatment process. For example, if the initial organic matter concentration of raw wastewater is high In this case, it is possible to relatively reduce the concentration of the hardly biodegradable substance by diluting the raw water discharged from the biological treatment process by increasing the amount of electrolytically treated water returned to the biological treatment process.

[0030] Further, as another aspect of the present invention, a biological treatment step of biologically treating an organic wastewater containing a hardly biodegradable substance to obtain biologically treated water, and electrolytic treatment of the biologically treated water, An electrolysis process for obtaining electrolyzed water; a concentration process for concentrating the electrolyzed water to obtain concentrated water; and a returning process for returning at least a part of the concentrated water to the biological treatment process. A method for treating organic waste water containing a substance capable of decomposing is provided.

[0031] This mode is suitable when it is desirable to perform advanced cleaning treatment that is required to achieve drainage standards that are discharged directly into the natural environment such as rivers and sea areas that are not covered by sewerage discharge standards.

[0032] This embodiment is characterized in that the electrolytically treated water is concentrated to obtain concentrated water, and this concentrated water is returned to the biological treatment step. As a mode of concentration, an appropriate method known in the field of solute concentration can be used. For example, membrane separation and concentration such as reverse osmosis (RO) membrane and loose RO membrane (NF membrane), evaporation concentration by evaporating water by heating or decompression, concentration by electrodialysis and the like can be preferably used. Loose RO membrane (NF membrane) separation with high inorganic ion permeability is most preferred because it suppresses the generation of scale by inorganic compounds such as calcium carbonate.

[0033] It should be noted that the separation process separation water has a different name depending on the concentration mode. For example, in the case of membrane separation concentration, the concentration process separation water means permeated water, in the case of evaporation concentration, it means distilled water, and in the case of electrodialysis, it means demineralized water.

[0034] Concentrated water contains easily biodegradable substances generated in the electrolytic treatment process, and they are easily decomposed in the biological treatment process. Concentrated water contains various inorganic ions, such as calcium, magnesium, and phosphorus, contained in ordinary organic wastewater. These inorganic ions are taken into the sludge during the biological treatment process. Since inorganic ions taken into sludge can be discharged to the outside as surplus sludge, scale generation can be prevented.

[0035] When the concentrated water contains a large amount of solutes such as calcium, magnesium, and phosphorus that cause scale formation, a part of the concentrated water is discharged to the outside regularly or intermittently, or For one or more of treated water, electrolytically treated water or concentrated water, H AP (hydroxyapatite, Ca (OH) (PO)) or MAP (magnesium phosphate ammonium)

5 4 3

, Mg (NH) PO) treatment to produce scales such as calcium, magnesium and phosphorus

4 4

The causative component may be crystallized and removed. Alternatively, before the concentration step, an acid such as hydrochloric acid or sulfuric acid may be added to prevent scale formation.

[0036] Further, as another aspect of the present invention, a biological treatment step of biologically treating an organic wastewater containing a hardly biodegradable substance to obtain biologically treated water, and concentrating the biologically treated water, A concentration step for obtaining concentrated water, an electrolytic treatment step for electrolytically treating at least a part of the concentrated water to obtain electrolytic treated water, and a returning step for returning the electrolytic treated water to the biological treatment step. An organic wastewater treatment method containing a biodegradable substance is provided.

[0037] This embodiment is characterized in that after biologically treated water is concentrated, electrolytic treatment is performed, and this electrolytically treated water is returned to the biological treatment step. By returning the electrolytically treated water to the biological treatment process, the easily biodegradable low molecular weight intermediate product produced by the electrolytic treatment is treated in the biological treatment process and not introduced into the concentration process. In other words, since the water separated from the concentration process does not contain easily biodegradable low-molecular intermediate products, the water quality can be greatly improved and can be released into the environment as it is.

[0038] The concentration ratio in the concentration step of the present embodiment affects the processing efficiency and processing cost of the electrolytic processing step. The higher the concentration of salt in the concentrated water, the lower the power consumption in the electrolytic treatment process. The lower the concentration of organic matter in the concentrated water, the lower the electrolytic treatment efficiency.

[0039] According to the present invention, organic wastewater containing a hardly biodegradable substance is biologically treated to obtain biologically treated water, the biologically treated water is electrolytically treated to obtain electrolytically treated water, and the electrolytically treated water. By returning to the biological treatment process again, the load in the biological treatment process can be increased while the load in the electrolytic treatment process can be reduced, resulting in the ability to reduce the amount of power required for the electrolytic treatment. . Thus, significant cost savings can be achieved with the present invention. In addition, when the biological treatment process is an anaerobic biological treatment process, the amount of biogas generated increases as the biological treatment load increases, and the amount of energy recovered increases. The recovered energy can be used as part of the electrical energy required for the electrolytic treatment process. Furthermore, the electrolyzed water whose water temperature has risen due to Joule heat in the electrolysis process can be returned to the biological treatment process and used as part of the thermal energy required in the biological treatment process. it can. As described above, the organic wastewater treatment method of the present invention can use the energy generated with the material flow in each process as the required energy of the system, and achieves significant energy savings for the entire system. be able to.

Brief Description of Drawings

[0040] [Fig. 1] Fig. 1 shows an example of the relationship between the amount of electricity input (Ah / g -CODCr) and CODCr (mg / L) and BOD (mg / L) in electrolysis using a conductive diamond electrode. It is a graph which shows.

[FIG. 2] FIG. 2 is a graph showing an example of the relationship between the amount of electricity input (Ah / g-CODCr) and BOD / CODCr in electrolytic treatment using a conductive diamond electrode.

[FIG. 3] FIG. 3 is a graph showing an example of the relationship between the amount of electricity input (Ah / g-CODCr) and VFA (mg / L) in electrolytic treatment using a conductive diamond electrode.

[FIG. 4] FIG. 4 is a graph showing an example of the relationship between the input electricity amount (Ah / g-CODCr) and pH in the electrolytic treatment using a conductive diamond electrode.

FIG. 5 is a schematic explanatory diagram of a processing flow according to the first embodiment of the present invention.

FIG. 6 is a schematic explanatory view showing an example of a circulating batch type electrolytic treatment tank used in the present invention.

FIG. 7 is a schematic explanatory diagram of a processing flow according to the second embodiment of the present invention.

FIG. 8 is a schematic explanatory diagram of a processing flow according to the third embodiment of the present invention.

[FIG. 9] FIG. 9 is a schematic explanatory diagram of a processing flow according to a conventional example used as a control in Example 1.

FIG. 10 is a schematic explanatory diagram of a treatment flow in which the electrolytically treated water used as a control in Example 3 is not sent to the biological treatment process.

FIG. 11 is a schematic explanatory diagram of a partial deformation process flow according to the second embodiment of the present invention.

[0041] In the drawings, reference numeral 1 represents raw waste water, 2 represents a biological treatment process (biological treatment apparatus), 3 represents biological treatment water, 4 represents an electrolytic treatment process (electrolytic treatment tank), 5 Indicates electrolytic treatment water, 6 indicates electrolytic treatment return water, 8 indicates a concentration step (concentration device), 9 indicates concentration water, 10 indicates concentration step separation water (permeate), 11 indicates The crystallization tank is shown.

DESCRIPTION OF PREFERRED EMBODIMENTS [0042] Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings, but the present invention is not limited thereto.

[Embodiment 1]

FIG. 5 is a schematic explanatory diagram illustrating one embodiment of the present invention. According to FIG. 5, the organic wastewater raw water (hereinafter simply referred to as “drainage raw water”) 1 containing a hardly biodegradable substance is first introduced into the biological treatment process (biological treatment device) 2. In biological treatment process 2, easily biodegradable substances in the raw wastewater are separated and removed, and biological treated water 3 containing a large amount of difficult biodegradable substances is obtained. Subsequently, the biologically treated water 3 is introduced into the electrolytic treatment step (electrolytic treatment tank) 4. In the electrolytic treatment process (electrolytic treatment tank) 4, the hardly biodegradable substances are decomposed into easily biodegradable substances such as VFA, carbon dioxide and water, etc., and discharged as the electrolyzed water 5. Part of the electrolyzed water 5 is returned to the biological treatment process (biological treatment device) 2 as electrolytic treatment return water 6. In the biological treatment process (biological treatment equipment) 2, the readily biodegradable substances contained in the electrolytic treatment return water 6 are biologically treated.

[0043] The biological treatment step 2 is an aerobic biological treatment step and / or an anaerobic biological treatment step usually used in the art. The biological treatment apparatus that can be used in the biological treatment step 2 includes an aerobic biological treatment tank such as an aeration tank, an anaerobic biological treatment tank, and a precipitation tank that are usually used in this field.

The form of the electrolytic treatment tank 4 is not particularly limited as long as it includes at least a conductive diamond electrode (not shown) as an anode. As a method for installing the conductive diamond electrode in the electrolytic treatment tank 4, it is preferable to have a structure that can vent the gas as well as possible. If the gas can not be vented well, bubbles will accumulate between the electrodes, causing the voltage between the electrodes to increase. Therefore, it is preferable to install the electrodes vertically rather than horizontally in the electrolytic treatment tank 4. In addition, when the electrode is installed horizontally in the electrolytic treatment tank 4, at least the conductive diamond electrode and / or the cathode that will be the anode is meshed, punched plate, etaspun metal, etc. It is desirable to have a structure that can be used. As a method for energizing the electrolytic treatment tank 4, a monopolar (single electrode) electrode method may be used, or a bipolar electrode method (bipolar electrode) may be used. When a large electrode area is required, there are the advantages of bipolar force S and compact equipment. The operation of the electrolytic treatment tank 4 may be a batch type, a circulating batch type, or a continuous type.

[0046] In the case of a batch type, the electrolytic treatment tank 4 is in the form of a tank having an anode and a cathode formed of conductive diamond electrodes. The biologically treated water 3 from the biological treatment process 2 is sent to the electrolytic treatment tank 4. The biologically treated water 3 is subjected to electrolytic treatment in the electrolytic treatment tank 4 for a certain period of time, and when the BOD / CODCr force S becomes 0.3 or more, the electrolytically treated water 5 containing an easily biodegradable substance can be obtained.

[0047] In the case of the circulating batch type, as shown in Fig. 6, an electrolytic cell 4a having a cathode and a cathode composed of conductive diamond electrodes is provided outside the tank 4b, and drainage is tanned with a pump or the like. The liquid can be sent from the tank 4b to the electrolytic cell 4a, while the treated water of the electrolytic cell 4a can be returned to the drain tank 4b. In this case, a forced flow of drainage by pumping can be performed between the anode and the cathode in the electrolysis cell 4a, so that the electrolysis efficiency can be maintained better than when the electrode is simply immersed in the drainage tank. Even in this circulating batch system, it is possible to obtain electrolytically treated water 5 containing readily biodegradable substances when the BOD / CODCr of the wastewater in the tank becomes 0.3 or more.

[0048] In the case of a continuous type, a plurality of tanks having batch-type electrodes and / or a plurality of electrolytic treatment tanks 4 composed of a combination of a circulation batch-type electrolytic cell and a tank are arranged in series. A predetermined residence time is ensured. When performing treatment with multiple electrolytic treatment tanks arranged in series, wastewater treated in the first-stage electrolytic treatment tank is sent to the next electrolytic treatment tank, and the conductive diamond electrode is also used in this electrolytic treatment tank. It is configured to perform electrolytic treatment using In the electrolytic treatment tank having such a configuration, the treated water obtained from the final-stage electrolytic treatment tank is the electrolytic treated water 5. In the electrolytic treatment tank 4 having such a configuration, there is an advantage that the operating conditions of the electrolytic cell in each stage can be set by the CODCr concentration of the waste water. For example, since the waste water in the high concentration C ○ DCr region from the biological treatment process flows into the first stage electrolytic treatment tank, it is a high current density electrolytic treatment tank. Since the waste water in the low concentration CODCr region flows into the second and subsequent electrolytic treatment tanks, the low current density electrolytic treatment tank will be used. Thus, an electrolytic treatment operation using a more efficient conductive diamond electrode can be performed.

[Embodiment 2] FIG. 7 is a schematic explanatory view showing another embodiment of the present invention. The water quality of the electrolyzed water 5 in Embodiment 1 may not be sufficiently clear, and although the exclusion criteria for discharging sewers are satisfied, the drainage standard for discharging directly into the environment such as rivers or sea areas May not be satisfied. When the treated water is directly discharged into the environment, the quality of the treated water can be improved by providing a concentrating step (concentrator) 8 after the electrolytically treated water 5 of the first embodiment.

In the embodiment shown in FIG. 7, raw waste water 1 is introduced into a biological treatment process (biological treatment device) 2 to separate and remove easily biodegradable substances, and biological substances rich in hardly biodegradable substances. Treated water 3 is obtained. The biologically treated water 3 flows into the electrolytic treatment process (electrolytic treatment tank) 4. In the electrolytic treatment process (electrolytic treatment tank) 4, the hardly biodegradable substance in the biologically treated water 3 is decomposed and discharged as the electrolytically treated water 5. Electrolyzed water 5 is introduced into a concentration process (concentration device) 8 to obtain concentrated water 9 and concentrated process separation water 10. Part or all of the concentrated water 9 is returned to the biological treatment process (biological treatment equipment) 2. The concentrator 8 is a solute concentrator, for example, a membrane separator / concentrator such as an RO membrane or a loose RO membrane (NF membrane), an evaporator / concentrator that evaporates water by heating or decompression, and a concentrator such as electrodialysis. It's okay. The concentration process separation water 10 means permeated water when the concentration process is a membrane separation method, distilled water when it is an evaporation concentration method, and demineralized water when it is electrodialysis.

[0050] The readily biodegradable substance contained in the concentrated water 9 can be easily treated in the biological treatment process (biological treatment apparatus) 2. In addition, components that cause scale formation such as calcium, magnesium, and phosphorus contained in the concentrated water 9 can be taken into sludge in the biological treatment process (biological treatment equipment) 2 and discharged to the outside as excess sludge. If the biological treatment process (biological treatment equipment) 2 includes an anaerobic 'aerobic treatment tank, more phosphorus can be fixed to the excess sludge.

[0051] Further, as shown by a dotted line in FIG. 11, in order to prevent scale formation, the crystallization tank 11 targets at least one of the biologically treated water 3, the electrolytically treated water 5 and the concentrated water 9, HAP (Hydroxysiapatite, Ca (OH) (PO)) or MAP (Magnesium phosphate ammonium, Mg (NH)

5 4 3 4

P〇) Processes that cause scale formation of calcium, magnesium, phosphorus, etc.

Four

It can also be configured to remove the hydrodynamic force in the form of crystals. [0052] Alternatively, it is also possible to add an acid such as hydrochloric acid'sulfuric acid before the concentrating device 8 to prevent scale formation.

[Embodiment 3]

FIG. 8 is a schematic explanatory view showing another embodiment of the present invention. In Embodiment 2, since the concentration device 8 is downstream of the electrolytic treatment tank 4, an easily biodegradable substance contained in the electrolytic treatment water 5 is introduced into the concentration device 8. Among the intermediate products generated in the electrolytic treatment tank 4, formic acid (molecular weight 46, boiling point 101 ° C), acetic acid (molecular weight 60, boiling point 118 ° C), etc. have low molecular weight and relatively low boiling point. For this reason, formic acid and acetic acid partially move to the permeate side in the case of membrane separation treatment, in particular, concentration treatment with a loose R ○ membrane, and partly move to the distilled water side in the case of evaporation concentration treatment. Therefore, there is a possibility that the water quality of the target concentration water 10 is not satisfied.

However, Embodiment 3 is suitable for improving the water quality of the separation water 10 in the concentration process. In the embodiment shown in FIG. 8, the raw waste water 1 is introduced into the biological treatment process (biological treatment device) 2. In the biological treatment process (biological treatment device) 2, readily biodegradable substances in the wastewater raw water 1 are separated and removed, and biologically treated water 3 containing a large amount of hardly biodegradable substances is obtained. The biologically treated water 3 is introduced into a concentration process (concentration device) 8 to obtain concentrated water 9 and concentrated process separation water 10. A part or all of the concentrated water 9 is introduced into the electrolytic treatment step (electrolytic treatment tank) 4. In the electrolytic treatment process (electrolytic treatment tank) 4, the hardly biodegradable substance is decomposed to obtain the electrolyzed water 5 containing the easily biodegradable substance. The electrolytically treated water 5 is then returned to the biological treatment process (biological treatment device) 2. In the biological treatment process (biological treatment equipment) 2, the readily biodegradable substances contained in the electrolyzed water 5 are separated and removed. In the present embodiment, since the low-molecular intermediate product contained in the electrolytically treated water 5 is not introduced into the concentration step (concentration device) 8, the water quality of the concentration step separation water 10 can be greatly improved.

Example

Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1

[0054] Electrolytic treatment using a diamond electrode was performed on factory wastewater A, and changes in the biodegradability of the treated water accompanying the electrolytic treatment were examined. Factory wastewater A has a CODCr of 7500 (mg / L), BOD power S 1450 (mg / L), BOD / CODCr was about 0.2, which was a wastewater containing a lot of non-biodegradable substances.

[0055] As the electrolytic treatment tank, an electrolytic treatment tank using a conductive diamond electrode as an anode and a titanium electrode as a cathode was used. The diamond electrode is formed by depositing conductive diamond on a silicon wafer substrate by the hot filament CVD method. The electrode area was about 140 cm ² and the current value was 14 A. The experiment was carried out in a circulating batch system, with an initial water volume of 3L and a pumping flow rate from the tank to the electrolysis cell of lL / min.

[0056] Figure 1 shows the relationship between the input electricity (Ah / g_CODCr), CODCr (mg / l), and BOD (mg / L). Figure 2 shows the input electricity (Ah / gC0DCr) and BOD. Indicates the relationship of / C ○ DCr.

[0057] When the electrolytic treatment was started, CODCr decreased almost linearly. The BOD increased up to about 1.5Ah / g_CO DCr input, and then decreased with increasing input. At about 5Ah / g_CODCr, both CODCr and BOD were almost zero. BOD / CODCr was about 0.2 at the beginning of the experiment. When the amount of electricity of 2Ah / g-C ○ DCr was input, BOD / CODCr increased to about 0.5. This indicates that the biodegradability of the treated water has been improved. BOD / CODCr decreased when the input electricity exceeded 2Ah / g_CODCr.

[0058] Fig. 3 shows the relationship between the input electricity (Ah / g-CODCr) and VFA (mg / L). Figure 4 shows the relationship between the input electricity (Ah / g-CODCr) and pH. The most produced VFA was formic acid, followed by almost the same amounts of acetic acid and lactic acid. The sum of these concentrations is shown in Figure 3 as the VFA concentration. Up to about 2Ah / g-CODCr of input electricity, the amount of VFA generated increased as the amount of electricity increased, and the pH decreased. When the amount of electricity input exceeded about 2Ah / g-CODCr, the amount of VFA produced decreased with the increase of electricity, and the pH increased. When the amount of electricity input exceeded about 3Ah / g-CODCr, VFA decreased rapidly. The improved biodegradability of the treated water is due to the generation of VFA.

Example 2

[0059] A test was conducted on industrial wastewater B. The test was performed according to the processing flow shown in FIG. In the biological treatment process (biological treatment equipment) 2, medium temperature methane fermentation was performed. As the electrolytic treatment step (electrolytic treatment bath) 4, an electrolytic treatment bath using a conductive diamond electrode as an anode and a titanium electrode as a cathode was used. The diamond electrode is formed by depositing conductive diamond on a silicon wafer substrate by hot filament CVD. The electrode area was about 280 cm ² . As a control, figure The test was conducted with the treatment flow in which the electrolytic treatment step (electrolysis treatment tank) 4 shown in Fig. 9 was not returned to the biological treatment step (biological treatment equipment) 2.

[0060] Comparison of test results is shown in Table 1. “Experiment 1” and “Experiment 2” in Table 1 are the results of the test with the process flow shown in FIG. 5, and “Experiment 3” is the result of the test with the process flow shown in FIG. In Experiment 1, the flow rate of electrolyzed return water 6 was 3 times the raw water flow rate, and in Experiment 2, the flow rate of raw water was 6 times. In the table, “Influent” represents raw wastewater 1 and “Outflow” represents electrolytic water 5.

[0061] [Table 1]

Table 1 Comparison of test results

[0062] In Experiment 1, the required electrolysis power in the electrolytic treatment process (electrolytic treatment tank) 4 was about 30% lower than in Experiment 3, and the amount of methane gas generated by methane fermentation was about 1.3 times higher. Also, by increasing the return flow rate, the generated methane gas further increased and the electrolysis power decreased.

Example 3

[0063] A test was conducted on industrial wastewater C. The test was conducted according to the processing flow shown in FIG. In the biological treatment process (biological treatment equipment) 2, medium temperature methane fermentation was performed. Electrolytic treatment process (electrolysis treatment tank) 4 as an electrolytic treatment tank using a conductive diamond electrode as an anode and titanium electrode as a cathode; Concentration process (concentration device) 8 as a loose RO membrane (Product name: Nitto Denko) A membrane separation and concentration device equipped with NTR-7250) was used. The diamond electrode is formed by depositing conductive diamond on a silicon wafer substrate by the hot filament CVD method.

[0064] In the electrode area of about 280 cm ^2, the current value was set to 6A. The test was conducted using the process flow shown in Fig. 5.

[0065] Comparison of test results is shown in Table 2. In Table 2, “Experiment 4” is the result of the test with the process flow shown in FIG. 7, and “Experiment 5” is the result of the test with the process flow shown in FIG. In Experiment 4, the concentration factor in the concentration step (concentrator) 8 was tripled, and the concentrated water 9 was adjusted to the raw water flow rate. Returned to biological treatment process (biological treatment equipment) 2 at 3 times. In Experiment 5, the electrolytic treatment return water 6 was returned to the biological treatment process (biological treatment equipment) 2 at a flow rate three times the raw water flow rate. “Influent” in the table refers to raw wastewater1. “Outflow water” in the table represents concentrated process separation water 10 in the flow shown in FIG. 7, and electrolytic treatment water 5 in the flow shown in FIG.

[Table 2]

Table 2 Comparison of test results

[0067] Compared to Experiment 5, in Experiment 4, the effluent was further purified, and the amount of generated methane gas was 1.5 times higher. In Experiment 4, since the inorganic ions are concentrated in the concentration step (concentration device) 8 and the electrical conductivity is increased, the voltage required to pass a predetermined current in the electrolytic treatment step (electrolysis treatment tank) 4 is Low compared to Experiment 5.

Example 4

[0068] A test was conducted on industrial wastewater D having a relatively low CODCr concentration. The test was performed according to the process flow shown in Fig. 8. In biological treatment process 2, standard activated sludge treatment was performed. As the concentrator 8, a membrane separation and concentrator equipped with a loose RO membrane (product name: NTR-7250 manufactured by Nitto Denko) was used. As the electrolytic treatment tank 4, a conductive diamond electrode was used as an anode and a titanium electrode was used as a cathode. An electrolytic treatment tank was used. The diamond electrode is formed by depositing conductive diamond on a silicon wafer substrate by hot filament CVD. The electrode area was about 280 cm ² . As a control, the treatment flow shown in FIG. 7 and the treatment flow (FIG. 10) in which the electrolytically treated water 5 was introduced again into the concentration step (concentration device) 8 instead of the biological treatment step (biological treatment device) 2 were also tested. In the treatment flow shown in Fig. 10, in order to prevent scale formation due to calcium carbonate, it was necessary to add sulfuric acid before the concentrator 8 to lower the pH to about 5. In the treatment flow shown in Fig. 8 and Fig. 7, calcium was removed together with surplus sludge from the biological treatment process. For each processing flow In this case, the concentration factor in the concentrator 8 was tripled.

[0069] Table 3 shows the test results. “Experiment 6” represents the result of the process flow shown in FIG. 8, “Experiment 7” represents the test result of the process flow shown in FIG. 7, and “Experiment 8” represents the test result of the process flow shown in FIG. In the table, “influent water” represents raw wastewater 1 and “outflow water” represents concentrated process separation water (permeated water) 10.

[0070] From Table 3, it can be seen that in Experiment 6, the effluent water was highly purified compared to Experiment 7 and Experiment 8. This is because, in Experiment 6, an easily biodegradable low-molecular intermediate product such as VFA contained in the electrolytically treated water 5 is introduced into the biological treatment process (biological treatment equipment) 2 and then into the concentration process (concentration equipment) 8. This is because was not introduced. In Experiment 7 and Experiment 8, the electrolyzed water 5 was introduced into the concentration step (concentrator) 8 and a part of the VFA contained in the electrolyzed water 5 permeated through the loose RO membrane.

[0071] [Table 3]

Table 3 Comparison of test results Treatment Raw water Return Concentration Inflow water Outflow water Torrent Tortoise pressure Electrolysis Derivative flow Flow Direct flow Rate Magnification CODcr CODCr

L / h L / h mg L mg / L A V Wh / L

6 Fig. 8 1 3 3 1450 7 0.4 5.5 2.2

7 Fig. 7 1 3 3 1450 35 0.5 5.2 2.6

8 M 1 0 1 3 3 1450 45 0.5 5.2 2.6

Claims

The scope of the claims

[1] a biological treatment device;

An electrolytic treatment tank located downstream of the biological treatment apparatus and comprising a conductive diamond electrode;

A return line for returning at least a portion of the effluent from the electrolytic treatment tank to the biological treatment device;

An organic wastewater treatment apparatus containing a non-biodegradable substance.

[2] biological treatment equipment;

A concentrator located downstream of the electrolytic treatment tank;

A return line for returning at least a part of the concentrated water from the concentrator to the biological treatment device, and a non-biodegradable substance-containing organic waste water treatment device.

[3] biological treatment equipment;

A concentrator located downstream of the biological treatment device;

An electrolytic treatment tank located on the downstream side of the concentrated water side of the concentrator and having a conductive diamond electrode;

A return line for returning the effluent from the electrolytic treatment f to the biological treatment device;

[4] A biological treatment process for biologically treating organic wastewater containing a hardly biodegradable substance to obtain biologically treated water;

An electrolytic treatment step of electrolyzing at least part of the biologically treated water using a conductive diamond electrode to obtain electrolytically treated water;

A return step for returning at least a part of the electrolytically treated water to the biological treatment step, and a method for treating organic wastewater containing a hardly biodegradable substance.

[5] The organic wastewater treatment method containing a hardly biodegradable substance according to claim 4, wherein an amount of electricity of 10 to 90% of a theoretical amount of electricity is imparted in the electrolytic treatment step.

[6] Living organisms that obtain biologically treated water by biologically treating organic wastewater containing non-biodegradable substances Processing steps;

An electrolysis process of electrolyzing the biologically treated water using a conductive diamond electrode to obtain electrolyzed water;

A concentration step of concentrating the electrolytically treated water to obtain concentrated water;

Returning at least a portion of the concentrated water to the biological treatment process;

An organic wastewater treatment method containing a hardly biodegradable substance.

[7] The organic wastewater treatment method containing a hardly biodegradable substance according to claim 6, wherein an amount of electricity of 10 to 90% of a theoretical amount of electricity is imparted in the electrolytic treatment step.

[8] A biological treatment process for biologically treating organic wastewater containing a hardly biodegradable substance to obtain biologically treated water;

A concentration step of concentrating the biologically treated water to obtain concentrated water;

An electrolytic treatment process for obtaining electrolytically treated water by electrolytically treating at least a part of the concentrated water using a conductive diamond electrode;

Returning the electrolytically treated water to the biological treatment step;

[9] The organic wastewater treatment method containing a hardly biodegradable substance according to claim 8, wherein an electric quantity of 10 to 90% of a theoretical electric quantity is given in the electrolytic treatment step.