JP4976032B2 - Organic wastewater treatment method - Google Patents

Description

  The present invention relates to a method for treating organic wastewater, and more particularly to a method for treating organic wastewater that can be applied to the field of general organic wastewater treatment such as public sewage, agricultural settlement drainage, human waste treatment, and industrial wastewater.

  In the wastewater treatment technology for biological treatment under aerobic conditions, the inventors pay attention to an increase in the number of vegetative cells (colony count) and the number of nitrifying bacteria, and increase the oxygen consumption rate and the nitrification rate. We are developing wastewater treatment technology that improves activity and realizes high-performance treatment of organic wastewater.

  As a result of such development research, it was found that high-performance treatment of organic wastewater was achieved by contact mixing of uniform solid particulates and sludge.

  Conventionally, technology that uses inorganic solid powder as a flocculant or coagulant for water treatment is known, but it focuses on sedimentation of sludge, increasing the number of vegetative cells (colony count) and the number of nitrifying bacteria. It is not a technology that focuses on.

  Moreover, the utilization technique as a support | carrier of an immobilized microorganism is also known. Patent Document 1 proposes a technique in which coal combustion ash (microorganism-immobilized fine particle carrier) having a particle diameter of 1 to 200 μm is introduced into an aeration tank to attach (aggregate) microorganisms.

Patent Document 2 discloses a microorganism-immobilized fine particle carrier having a particle size of 0.1 to 1000 μm. In this technology, as microbe-immobilized fine particle carriers, combustion ash such as coal combustion ash and sludge combustion ash, activated alumina, zeolite, titanium oxide, ferrite, various carbon materials (activated carbon, charcoal, etc.), etc., and spent disposal thereof Things are listed.
Japanese Patent Laid-Open No. 9-131178 Japanese Patent Laid-Open No. 2005-230783

  However, although the particles described in Patent Documents 1 and 2 use fine particles such as coal combustion ash, since the particle size distribution is wide, the increase in the number of vegetative cells (colony count) and the number of nitrifying bacteria is sufficient. There were no shortcomings.

  Therefore, the present invention treats organic wastewater using uniform fine particles to increase the number of vegetative cells (colony count) and the number of nitrifying bacteria, and to increase the oxygen consumption rate and nitrification rate to improve the treatment activity. It is an object to provide a method.

  Other problems of the present invention will become apparent from the following description.

  The above-described problems of the present invention are solved by the following inventions.

(Claim 1)
A gas-liquid contact process comprising a gas-liquid contact tank for biologically treating organic wastewater under aerobic conditions, and a solid-liquid separation of sludge suspension sent from the gas-liquid contact process into sludge and treated water. In a method for treating organic wastewater having a solid-liquid separation step equipped with a liquid separation means,
To the organic waste water or sludge in the gas-liquid contact process, an inorganic solid powder having an average particle diameter (major axis) of 10 μm or less and a distribution of 70 wt% or more within ± 5 μm is added or coexisted. a method of processing organic waste water that,
Part of the sludge separated in the solid-liquid separation step is introduced into a sludge acclimation tank, and the excess sludge in the sludge acclimation tank has an average particle size (major axis) of 10 μm or less, and the distribution is 70 weights within ± 5 μm. % Or more inorganic solid powder is added and the average time is allowed to coexist for 3 hours to 10 days, and then sent to the gas-liquid contact tank.

(Claim 2)
When adding inorganic solid powder to organic wastewater and coexisting, (1) A wastewater tank for storing organic wastewater is provided and added to the wastewater tank, or (2) Organic wastewater is gas-liquid It was added in the process of sending the contact tank, the method of treating organic waste water according to claim 1, characterized by using a method for coexistence.

(Claim 3)
The method for treating organic wastewater according to claim 1 or 2, wherein the average time for coexistence of the organic wastewater and the inorganic solid powder is in the range of 3 hours to 10 days.

(Claim 4 )
The method for treating organic wastewater according to any one of claims 1 to 3 , wherein the temperature of the sludge conditioned tank is adjusted to a range of 10 ° C to 60 ° C.

(Claim 5 )
The organic wastewater according to any one of claims 1 to 4, wherein the sludge acclimatization tank is adjusted to an aerobic degree within a range of redox potential +0.1 to -0.1 based on a standard hydrogen electrode potential. Processing method.

(Claim 6 )
The method for treating organic wastewater according to any one of claims 1 to 5, wherein at least one selected from an iron compound, a magnesium compound and a calcium compound is added to a sludge acclimation tank.

(Claim 7 )
The method for treating organic wastewater according to any one of claims 1 to 6 , wherein the inorganic solid powder is a clay mineral powder or a shell powder.

(Claim 8 )
The method for treating organic wastewater according to any one of claims 1 to 7 , wherein the inorganic element powder has an aluminum element content of 15% or less.

  According to the present invention, treatment of organic wastewater using uniform fine particles to increase the number of vegetative cells (colony count) and the number of nitrifying bacteria, and to increase the oxygen consumption rate and nitrification rate to improve the treatment activity. A method can be provided.

  Embodiments of the present invention will be described below.

  FIG. 1 is an explanatory view showing an example of an apparatus for carrying out a method for treating organic wastewater according to the present invention. 1 is a gas-liquid contact process in which organic wastewater is introduced and biologically treated under aerobic conditions. It is equipped with a gas-liquid contact tank (aeration tank). 2 is a solid-liquid separation step for solid-liquid separation of the suspension sent from the gas-liquid contact step 1 into activated sludge and treated water, and is constituted by solid-liquid separation means such as a sedimentation tank (precipitation basin) or a membrane treatment device, for example. Is done. In the following description, an example using a sedimentation tank (sedimentation basin) will be described.

  Most of the sludge settled and separated in the solid-liquid separation step 2 is returned to the gas-liquid contact step 1 through the return pipe 3, and a part thereof is sent to a sludge treatment facility (not shown) as surplus sludge.

  Part of the sludge (also referred to as surplus sludge) returned to the gas-liquid contact step 1 is sent to the sludge acclimatization tank 4.

  In the present invention, an inorganic solid powder having an average particle size (major axis) of 10 μm or less and a distribution of 70 wt% or more within ± 5 μm is added directly or indirectly to sludge in an organic waste water or gas-liquid contact process. And process to coexist.

  When adding or coexisting inorganic solid powder to organic wastewater, (1) A method for adding and coexisting with a wastewater tank for storing organic wastewater, or (2) Gas-liquid for organic wastewater A method of adding and coexisting in the process of sending to the contact tank can be adopted.

  In the former method (1), it is preferable that the capacity of the wastewater tank is designed so as to ensure the coexistence time of the wastewater and the inorganic solid powder. The average time for coexisting the waste water and the inorganic solid powder is preferably in the range of 3 hours to 10 days in order to exert the effect of biological treatment of the waste water (raw water) and sludge.

  In addition, when an aeration means is employed in the wastewater tank, the contact between the wastewater and the inorganic solid powder can be made sufficient, which is preferable in promoting the oxidative decomposition of the organic matter.

  In the latter method (2), the waste water and the inorganic solid powder can be mixed and stirred by providing a static mixer such as a line mixer in the process of sending the organic waste water to the gas-liquid contact tank.

  In order to add and coexist inorganic solid powder to the sludge in the gas-liquid contact process, it may be added directly to the aeration tank, but the sludge returned to the aeration tank is once accepted into the sludge acclimation tank, and the sludge acclimatization An inorganic solid powder can be added to the tank, and the added sludge can be returned to the aeration tank to indirectly add and coexist.

  The inorganic solid powder used in the present invention has an average particle size (major axis) of 10 μm or less and a distribution of 70% by weight or more within ± 5 μm. That is, “the distribution is 70% by weight or more within ± 5 μm” means that the particle size is fine and uniform, and those within ± 5 μm are less than 70% by weight. Too many coarse particles that reduce the treatment efficiency of biological treatment due to, or conversely, the proportion of too fine particles with extremely poor agglomeration properties increases, and none of the objects of the present invention can be achieved.

  As the inorganic solid powder, mineral powder selected from slate, igneous rock, plutonic rock, sedimentary rock and artificial mineral, or calcium powder such as oyster shell, scallop, and animal bone is preferable.

  The content of aluminum element in the inorganic solid powder is preferably 15% or less. This is because if it exceeds 15%, the effect of aluminum that inhibits the metabolism of bacteria increases.

  In order to produce an inorganic solid powder having an average particle size (major axis) of 10 μm or less, a pulverizer or the like can be used. Among them, it is preferable to use a powdering apparatus described in US Pat. No. 5,839,671. A feature of this apparatus is that fine pulverization of 10 μm or less can be pulverized in a relatively narrow particle size range.

  An inorganic solid powder having an average particle size (major axis) of 10 μm or less can be prepared by using a cyclone or the like as the final step so that the particle size distribution is 70% by weight within ± 5 m.

  The mixing ratio when adding the inorganic solid powder to the organic wastewater is preferably in the range of 1 g / L to 1 mg / L (1000 ppm to 1 ppm), more preferably sufficient addition effect is obtained depending on the organic load. The range is from 1 g / L to 3 mg / L (100 ppm to 3 ppm).

  Next, based on FIG. 2, the structural example of a sludge acclimatization tank is demonstrated.

  The inorganic solid powder is stored in a hopper 400 provided above the sludge acclimatization tank 4 and is supplied to the sludge acclimatization tank 4 by opening the regulating valve 401.

  The sludge to be acclimatized in the sludge acclimatization tank 4 is preferably sludge to be subjected to sludge treatment as surplus sludge out of the sludge settled and separated by the solid-liquid separation means. This is because if the sludge is treated in the sludge acclimation tank 4, the sludge is reduced, and if the excess sludge is treated, the load on the sludge treatment facility can be reduced.

  The sludge acclimatization tank 4 includes a stirrer 402, a pH meter 403, and an oxidation-reduction potentiometer (ORP meter) 404.

  Reference numeral 405 denotes a temperature adjusting device. In the illustrated example, a temperature adjusting device using a hot water supply pipe is used, but there is no particular limitation as long as the temperature can be adjusted. In order to effectively perform biological treatment on the surface of the fine powder (biofilm), it is preferable that the temperature in the sludge acclimation tank 4 is adjusted to a range of 10 ° C. to 60 ° C.

  A blower 406 is an example of an air supply unit, and is connected to a pipe 407 that supplies air into the sludge acclimation tank 4. An aerobic environment can be formed by supplying air into the sludge acclimatization tank 4. In the present invention, the aerobic degree of the sludge acclimatization tank is defined by the oxidation-reduction potential.

  The preferred aerobic degree is in the range of redox potential +0.1 to -0.1 based on the standard hydrogen electrode potential. To adjust to this range, the air supply amount of the blower 406 may be adjusted.

  Although the pH in the sludge acclimatization tank 4 is not specifically limited, A preferable pH is the range of 6-9. When it is in such a range, it is preferable for performing an aerobic biological treatment of an organic substance effectively.

  In the present invention, it is preferable to add at least one selected from iron compounds, magnesium compounds and calcium compounds to the sludge acclimation tank 4 in order to improve the sludge weight loss rate. These compounds may be added in the form of powder, but liquids are preferred in view of ease of operation such as flow rate control.

  As the iron compound, an aqueous solution such as iron chloride is preferable. As the magnesium compound, an aqueous hydroxide solution such as magnesium hydroxide is preferable. As the calcium compound, an aqueous hydroxide solution such as calcium hydroxide is preferable. One of those iron compounds, magnesium compounds and calcium compounds may be used, but it is also preferred to use a combination of two or more.

  The illustrated example is an example in which an aqueous iron chloride solution (20-35% aqueous solution) and an aqueous magnesium hydroxide solution (20-40% aqueous solution) are used in combination, 408 is an iron chloride aqueous solution tank, 409 is a supply pump, 410 Is a magnesium hydroxide aqueous solution tank, 411 is a stirrer, and 412 is a supply pump.

  The blending ratio of the iron compound aqueous solution, magnesium compound aqueous solution and calcium compound aqueous solution to sludge is preferably in the range of 1 to 50 ppm.

  The mixing ratio when adding the inorganic solid powder to the sludge in the sludge acclimatization tank 4 is preferably in the range of several percent to several ppm per MLSS, and more preferably in the range of 0.1% to 10 ppm as a weight ratio. .

  The average time for coexistence of sludge and inorganic solid powder in the sludge acclimatization tank 4 is preferably in the range of 3 hours to 10 days in order to exert the effects of the present invention. After 10 days, the decomposition of organic components proceeds and the activity decreases.

  Next, an example of a preferable apparatus for carrying out the processing method of the present invention will be described with reference to FIG.

  As shown in FIG. 3, after the inorganic solid is sent to the pulverizer 5 and pulverized, extremely fine particles are removed by the cyclone 6, the average particle size (major axis) is 10 μm or less, and the particle size distribution is within ± 5 μm. To obtain an inorganic solid powder (hereinafter referred to as a uniform inorganic solid powder if necessary). The obtained uniform inorganic solid powder is stored in the hopper 7. The uniform inorganic solid powder in the hopper 7 is supplied to the sludge acclimatization tank 4 by a predetermined amount by adjusting the opening / closing of the regulating valve 8.

  On the other hand, in organic wastewater such as sewage, coarse impurities are separated and removed by the screen 9, and are first sent to the sedimentation tank 10 for solid-liquid separation, and heavy substances such as sand are separated and removed. Thereafter, the waste water is sent to the aeration tank 11 and treated with microorganisms under aerobic conditions. In the present invention, the aerobic nitrification reaction is mainly promoted.

  The sludge suspension treated in the aeration tank 11 is solid-liquid separated in the final sedimentation basin 12 and separated into clear treated water and sludge. Most of the settled sludge is returned to the aeration tank 11 via the return pipe 13, and a part thereof is sent to the sludge acclimatization tank 4 as surplus sludge, and the surplus sludge is sent to a sludge treatment facility (not shown). It is processed.

  The surplus sludge sent to the sludge acclimatization tank 4 is aerobic adjusted by the blower 406 and temperature-controlled by the temperature adjusting device 405.

  Also, an iron chloride aqueous solution is supplied from the iron chloride aqueous solution tank 408, and a magnesium hydroxide aqueous solution is supplied from the magnesium hydroxide aqueous solution tank 410.

  The average time during which the sludge and the inorganic solid powder are allowed to coexist in the sludge acclimation tank 4 is in the range of 3 hours to 10 days, and more preferably in the range of 10 hours to 10 days.

  Examples of the present invention will be described below, but the present invention is not limited to such examples.

Example 1-4 and Comparative Example 1-3
Wastewater treatment was carried out at the raw water treatment plant in MK City under the following conditions by the process shown in FIG.

The wastewater to be treated is sewage of 17 m ³ / D, and its wastewater state is BOD: 170 mg / L, COD: 90 mg / L, SS: 170 mg / L, TN: 34 mg / L, TP: 4 mg / L Met.

The aeration tank had a capacity of 6 m ³ and the sludge concentration in the aeration tank (MLSS) was about 3000 mg / L. The sludge acclimatization tank had a capacity of 1.5 m ³ .

  The types and blending ratios of the inorganic solid powders used are as shown in Table 1, and the particle sizes are also shown in Table 1. The particle size distribution is shown in Table 1 by actually measuring 100 particles, calculating how many particles are within an average particle size of ± 5 μm, and determining the particle existence ratio.

<Evaluation>
Number of vegetative cells Disperse the sludge sample with a homogenizer at 15000 rpm for 1 minute, dilute with 0.7% physiological saline, plate on a Nutrientro broth agar medium containing starch, and culture at 32 ° C for 48 hours Then, after growing, the number of grown colonies was counted as the number of vegetative cells.

  The number of vegetative cells is represented by the number of counts per mg of organic component (Vss) in the sludge, and the results are shown in Table 1.

amoA
AmoA, which is a functional gene of ammonia-oxidizing bacteria, was quantified by real-time quantitative PCR. The copy number of amoA (ammonia oxidation functional gene) is expressed as the copy number of amoA per mg of sludge (Vss). The results are shown in Table 1.

Oxygen consumption rate for wastewater treatment The amount of oxygen (mg) consumed by 1 g of sludge (Vss) per unit time was determined, and the results are shown in Table 1.

Nitrification rate The amount of nitrogen (mg) nitrified by 1 g of sludge (Vss) per unit time was determined, and the results are shown in Table 1.

  From the results shown in Table 1, by reducing the particle size of the inorganic solid fine particles and making the particle size distribution uniform, the number of vegetative cells and the number of nitrifying bacteria are increased. As a result, the oxygen consumption rate and the nitrification rate are reduced. Improved. That is, it can be seen that the treatment activity is improved by the increase in the bacterial cell concentration due to the reduction in particle size, which is effective for organic matter treatment and nitrogen treatment.

Example 5 and Comparative Example 4
The slate powder used in Example 2 (average particle size of 8 μm, particle size distribution within 70% by weight within ± 5 μm) and the slate powder used in Comparative Example 1 (average particle size of 20 μm, particle size distribution within 50% by weight within ± 5 μm) In each case, 0.3% by weight was added to 5 L of concentrated sludge having a solid concentration of 2.8%, and stirring by air injection was performed to measure the rate of weight loss of sludge solids.

  The air flow rate was adjusted so as to be in the range of redox potential +0.1 to -0.1 based on the standard hydrogen electrode potential.

  Further, an aqueous solution of iron chloride, an aqueous solution of magnesium hydroxide, an aqueous solution of calcium hydroxide, and a mixed solution of an aqueous solution of iron chloride and an aqueous magnesium hydroxide solution were added so as to have the addition amounts shown in Table 2.

  The results of the sludge reduction rate are as shown in Table 2.

Explanatory drawing which shows an example of the apparatus which implements the processing method of the organic wastewater which concerns on this invention The figure which shows the structural example of a sludge acclimatization tank The figure which shows an example of the preferable apparatus which enforces the processing method of this invention

Explanation of symbols

1: Gas-liquid contact process 2: Solid-liquid separation process 3: Return pipe 4: Sludge acclimatization tank 400: Hopper 401: Adjustment valve 402: Stirrer 403: pH meter 404: Redox potential meter (ORP meter)
405: Temperature controller 406: Blower 407: Piping 408: Iron chloride aqueous solution tank 409: Supply pump 410: Magnesium hydroxide aqueous solution tank 411: Stirrer 412: Supply pump 5: Crusher 6: Cyclone 7: Hopper 8: Regulating valve 9 : Screen 10: First sedimentation tank 11: Aeration tank 12: Final sedimentation tank 13: Return pipe

Claims (8)

A gas-liquid contact process comprising a gas-liquid contact tank for biologically treating organic wastewater under aerobic conditions, and a solid-liquid separation of sludge suspension sent from the gas-liquid contact process into sludge and treated water. In a method for treating organic wastewater having a solid-liquid separation step equipped with a liquid separation means,
To the organic waste water or sludge in the gas-liquid contact process, an inorganic solid powder having an average particle diameter (major axis) of 10 μm or less and a distribution of 70 wt% or more within ± 5 μm is added or coexisted. a method of processing organic waste water that,
Part of the sludge separated in the solid-liquid separation step is introduced into a sludge acclimation tank, and the excess sludge in the sludge acclimation tank has an average particle size (major axis) of 10 μm or less, and the distribution is 70 weights within ± 5 μm. % Or more inorganic solid powder is added and the average time is allowed to coexist for 3 hours to 10 days, and then sent to the gas-liquid contact tank. When adding inorganic solid powder to organic wastewater and coexisting, (1) A wastewater tank for storing organic wastewater is provided and added to the wastewater tank, or (2) Organic wastewater is gas-liquid It was added in the process of sending the contact tank, the method of treating organic waste water according to claim 1, characterized by using a method for coexistence.   The method for treating organic wastewater according to claim 1 or 2, wherein the average time for coexistence of the organic wastewater and the inorganic solid powder is in the range of 3 hours to 10 days. The method for treating organic wastewater according to any one of claims 1 to 3 , wherein the temperature of the sludge conditioned tank is adjusted to a range of 10 ° C to 60 ° C. The organic wastewater according to any one of claims 1 to 4, wherein the sludge acclimatization tank is adjusted to an aerobic degree within a range of redox potential +0.1 to -0.1 based on a standard hydrogen electrode potential. Processing method. The method for treating organic wastewater according to any one of claims 1 to 5, wherein at least one selected from an iron compound, a magnesium compound and a calcium compound is added to a sludge acclimation tank. The method for treating organic wastewater according to any one of claims 1 to 6 , wherein the inorganic solid powder is a clay mineral powder or a shell powder. The method for treating organic wastewater according to any one of claims 1 to 7 , wherein the inorganic element powder has an aluminum element content of 15% or less.

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