JP3122654B2 - Method and apparatus for treating highly concentrated wastewater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a wastewater treatment for efficiently purifying high-concentration organic matter, particularly livestock wastewater or organic industrial wastewater containing nitrogen and phosphorus by utilizing soil microorganisms. Method and apparatus.

[0002]

BACKGROUND OF THE INVENTION Inducing eutrophication in surrounding water systems,
Livestock or organic industrial wastewater, which is recognized as a major source of environmental pollution, is treated by co-treatment plants or individual purification facilities depending on the size of the industry. But,
In the case of the livestock wastewater co-treatment plant, most of them cannot perform their original functions due to improper design load, etc., and even in the case of individual septic tanks, lack of adaptability to the type of barn and the concentration of wastewater due to livestock species. In many cases, the original function cannot be exhibited. In addition, the costs invested for treating livestock wastewater or organic industrial wastewater are excessive compared to the scale of the related industry, and it is difficult to secure the competitiveness of the industry.

In general, various methods such as anaerobic digestion, activated sludge method, and oxidation pond method are applied in connection with treatment of high-concentration sludge wastewater such as livestock wastewater. For example, Jose R. Bicudo and Ivo F. Svoboda,
“Intermittent aeration ofpig slurry-farm scale ex
periments for carbon and nitrogen removal ”. Wat.
Sci. & Tech. Vol. 32, No. 12, pp 83-90 (1985)
The results of treating pig sewage wastewater with dilution intermittent aeration have been reported. However, depending on such a purification process,
When the F / Mv ratio (substrate load ratio per unit time per unit mass of microorganism in the reaction tank) is 0.8 kg-BOD / kg-Mv / d or more, nitrification inhibition occurs.

On the other hand, CintoliC., Di Sabantino, B., Gal
eotti, L. and Bruno, G., “Ammonia uptake and trea
tment in UASB reactor of piggery wastewater ”, Wa
Vol. 32, No. 12, pp. 76-83 (1995) shows that centrifugation of swine wastewater and removal of NH ₄ ⁺ by ion exchange method with zeolite, Anaerobic Sludge Blanke (UASB)
t) method and UASB-anaerobic filter method,
It is disclosed to remove OD to 95%, TN to 90% and TP to 80%. Bortone G., Ge
meli, S. and Rambaldi, A., “Nitrification, denitr
ification and biological phosphate removal in SBR
treating piggery wastewater ”, Wat. Sci. & Tech. V
ol.26, No.5, pp 977-985 (1992), the wastewater of a piggery was centrifuged and treated in a batch reactor to reduce COD to 9%.
The results of removing 3%, TN 93% and TP 95% are reported. Yang, PY, Chen, H. Kongsr
ichareon, N. and Polprasert, C., “A swine waster p
ackage biotreatment plant for the tropics ”, Wat.
Sci. & Tech., Vol.28, No.2, pp. 211-218 (1993) reports the results of treatment of high-concentration wastewater by simple anaerobic method in a small-scale pig house. Martin, JH a
nd Loehr, RC, “Aerobic treatment of poultry was
tes ”, J. Agri. Eng. Res. Vol. 21, pp 157-167 (1976)
Report the results of treating poultry wastewater by the oxidation ditch method.

However, most of the wastewater treatment examples disclosed in the above-mentioned documents, except for the anaerobic digestion method, are performed on diluted wastewater. Therefore, application to small-scale livestock wastewater requires considerable improvement in the state of wastewater, with considerable differences.

[0006] Livestock wastewater or manure has also been generally recognized as a major factor in water eutrophication. However, existing treatment facilities mainly for organic matter removal cannot solve such environmental problems as eutrophication. Therefore, in order to improve the treatment efficiency of livestock wastewater and solve the above-mentioned problems, the existing facilities are operated by introducing technologies such as the B3 method using a microbial activator or a bio-reactor. However, not only is the operation cost of the treatment facility associated with the supply of microbial products, etc. uneconomical, but also because the facility mainly targets the treatment of organic matter, it is a cause of eutrophication. Nitrogen compounds and phosphorus compounds are not properly removed. Here, the B3 method means Bio Best Bacil
lus Sytem, a variant of the existing aerobic digestion method, selectively cultivates and predominates only Gram-positive Bacillus, a type of filamentous fungus, to induce the removal of organic matter and nutrients It is a construction method. Therefore, there are many problems in actually applying this method.

[0007]

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a wastewater treatment method and apparatus capable of efficiently treating high-concentration wastewater.

It is another object of the present invention to provide a wastewater treatment method and apparatus capable of economically and efficiently treating livestock wastewater and organic industrial wastewater by utilizing soil microorganisms.

Yet another object of the present invention is to utilize solidified soil microorganisms to improve the adaptability of the device to rapid changes in wastewater concentration, and to remove not only organic matter but also high concentrations of nitrogen and phosphorus. It is an object of the present invention to provide a wastewater treatment method and apparatus for effectively treating nutrients containing the same at low cost.

Yet another object of the present invention is applicable to a small-scale wastewater generation facility, which can reduce the processing cost for the joint treatment of livestock wastewater and solve the problem of pollution generated during the processing. It is to provide an efficient and economical wastewater treatment method and apparatus.

[0011]

Means for Solving the Problems To achieve the above object, the wastewater treatment method of the present invention comprises the steps of: (a) storing the effluent solid-liquid separated from the wastewater in a storage tank to adjust the concentration and the flow rate; (B) hydrolyzing the hardly decomposable organic matter in the effluent equalized in the storage tank by an anaerobic microorganism in an anaerobic fermentation tank into a state that is easy to ingest for subsequent microorganisms; (C) selecting aerobic microorganisms in the sludge transported from the dissolved oxygen controlled aeration tank to the microorganism activation tank in which the soil microorganism carrier is present, in the microorganism activation tank; Activating the aerobic microorganisms by selectively activating the biological adsorption capacity to grow the microorganisms filled in the soil microorganism carrier; (d) the effluent of the microorganism activating tank, the anaerobic Fermenter effluent, and sludge from the denitrification tank, And, if necessary, a step of mixing a filtrate sent from a dehydrator for solid-liquid separation of sludge from the anaerobic fermentation tank, the primary settling tank and the coagulation settling tank in a mixing tank; (e) mixing the mixed solution with Introducing the dissolved oxygen-regulated aeration tank to treat organic substances and phosphorus and nitrifying ammoniacal nitrogen; (f) converting the liquid treated in the aeration tank into endogenous microorganisms in an oxygen-free state. (G) separating the denitrified liquid into sludge and supernatant in a primary sedimentation tank; and (h) sedimenting in a primary sedimentation tank. The method is characterized by including a step of removing residual phosphorus and suspended solids from the separated supernatant in a coagulation sedimentation tank and releasing treated water.

Further, the wastewater treatment apparatus of the present invention comprises: (A) a storage tank for storing an effluent solid-liquid separated from wastewater to equalize the concentration and the flow rate; and (B) a storage tank downstream of the storage tank. An anaerobic fermentation tank provided with anaerobic microorganisms; (C) an internal activation tank containing a soil microbial carrier and a microbial activation tank provided with a diffuser; (D) the microbial activation tank and the anaerobic tank The effluent of each of the anaerobic fermenters, the sludge from the denitrification tank, and, if necessary, the filtrate sent from the dehydrator for solid-liquid separation of the sludge from the anaerobic fermenter, the primary sedimentation tank and the coagulation sedimentation tank. A mixing tank having an inflow port for receiving and mixing the inflow from the inflow port; (E) a dissolved oxygen-controlled aeration tank connected downstream of the mixing tank; (F) a mixing tank. A denitrification tank connected to the downstream side; (H) a primary sedimentation tank connected downstream of the nitriding tank; and (H) a coagulation sedimentation tank connected downstream of the primary sedimentation tank.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a wastewater treatment method and apparatus according to the present invention will be described in detail with reference to specific examples of the wastewater treatment apparatus according to the present invention shown in the accompanying drawings.

FIG. 1 is a block diagram of a livestock wastewater treatment apparatus according to the present invention. As shown in FIG. 1, the wastewater treatment apparatus (10) of the present invention comprises a storage tank (20), an anaerobic fermentation tank (3).
0), a microbial activation tank (40), a mixing tank (50), an aeration tank (60), a denitrification tank (70), a primary settling tank, for example, a multi-inclination settling tank (80), a coagulation settling tank (90) ) And preferably further comprises a dehydrator (100).

(A) The storage tank (20) contains the effluent discharged from the wastewater generated in the barn through solid-liquid separation, and is used as an anaerobic fermentation tank as treated wastewater having a uniform concentration and flow rate. (30).

(B) The anaerobic fermenter (30) anaerobically activates the phosphorus-free microorganisms and hydrolyzes the hardly decomposable organic matter in the treated wastewater flowing from the storage tank (20).

(C) The microbial activation tank (40) is charged with a bio-clad (42; bio-clod) which acts as a supply source of microorganisms applicable to high-concentration wastewater. Is selectively activated.

(D) The mixing tank (50) converts the wastewater treated in the anaerobic fermentation tank (30) into a microorganism activation tank (40).
Mixed with the effluent from the sludge and the conveyed sludge and sent to an aeration tank (60).

(E) The aeration tank (60) is provided with a mixing tank (5).
Organic substances and ammonia nitrogen in the wastewater flowing in from 0) are oxidatively decomposed by metabolism of microorganisms.

(F) The denitrification tank (70) is provided with an inflow port into which the aeration tank treatment liquid flows, and an internal contact filter medium, and is configured to mix nitrogen oxides of the liquid treated in the aeration tank (60). Nitrogen is removed by endogenous respiration of microorganisms contained in the liquid.

The sedimentation tank includes (G) a multi-inclination sedimentation tank (80) which functions as a primary sedimentation tank, for example, and (H) a coagulation sedimentation tank (90). The multi-slope sedimentation tank has an inlet and an outlet through which the treated supernatant flows, and separates the denitrified wastewater into solids and supernatant liquid. The coagulation sedimentation tank removes residual phosphorus and solids from the supernatant of the multi-tilt sedimentation tank (80).

The dehydrator (100) includes a coagulating sedimentation tank (90).
The residue such as sludge generated in the step is dewatered.

In the wastewater treatment apparatus (10) of the present invention, the first transport path (b) through which the microorganism sludge in the aeration tank (60) flows into the microorganism activation tank (40), and the denitrification tank (70)
A second transport path c through which the sludge flows into the mixing tank (50) and a third transport path d through which the microbial sludge from the multi-inclination sedimentation tank (80) flows into the anaerobic fermenter (30) are formed. Is preferred.

Further, the wastewater treatment apparatus (10) of the present invention has a fourth dewatering device (100) for flowing a filtrate generated during dewatering of sludge into a mixing tank (50) for processing.
A transport path e and, if necessary, a fifth transport path i through which the treated water of the multi-tilt settling tank (80) flows into the storage tank in order to adjust the concentration of the storage tank (20). Is preferred.

The wastewater treatment method of the present invention is typically performed as follows using the above wastewater treatment apparatus.

That is, livestock wastewater, manure, and the like generated in a barn or the like are first subjected to solid-liquid separation before being treated by the wastewater treatment device (10). The effluent generated by the solid-liquid separation contains high-concentration organic substances including hardly decomposable organic substances, and nitrogen compounds and phosphorus compounds.

(A) Step of Equalizing Concentration and Flow Rate Such wastewater is introduced into the storage tank (20) and stored. The storage tank is installed as a tank having a residence time of about 2 days for a flow rate of about 1.5 times the daily average flow rate of the wastewater, for example. In the storage tank, if necessary, the concentration of the wastewater is adjusted by the treatment water of the multi-inclination sedimentation tank (80) flowing along the fifth transport path i, and then the wastewater is discharged at a constant concentration and flow rate. The wastewater maintained at a constant concentration flows into the anaerobic fermenter (30) by a pump (not shown) or the like along the path indicated by arrow a in FIG.

(B) Step of Activating Dephosphorus Microorganism FIG. 2 schematically shows the structure of an anaerobic fermenter (30). An anaerobic microorganism is provided inside the anaerobic fermenter, and the organic matter contained in the wastewater flowing from the storage tank (20) is decomposed by the metabolic action of the anaerobic microorganism. In particular, aerobic microorganisms hydrolyze hard-to-degrade organic substances contained in wastewater into a state that is easy for them to ingest, and the phosphorus-ingesting microorganisms release phosphorus in the body to become an energy source, and organic acid in the form of organic acids. Will be stored in the body. That is, in the wastewater treatment apparatus according to the present invention,
Since the load of organic matter is appropriately adjusted in the anaerobic fermentation tank, the decomposition step by the anaerobic microorganism is a pretreatment step of the step of treating phosphorus in the aeration tank (60).

The anaerobic fermenter (30) shown in FIG.
It has an upright cylindrical shape, a first inlet (36) above which wastewater flows in from a storage tank (20), and a multi-incline sedimentation tank (80) to secure a third transport path to secure dephosphorized microorganisms. d through which the sludge flows along the second inlet (3
7), and an outlet (38) for discharging wastewater fermented in an anaerobic state.

The wall of the anaerobic fermenter (30) comprises a heat retaining wall (34) in which an electric coil (not shown) is built in to heat the inside thereof. An electric current is passed through the electric coil in the heat insulation wall to heat the inside of the anaerobic fermenter to a predetermined temperature or more, and the temperature of the wastewater discharged through the outlet (38) and the activated dephosphorized microorganisms described below The temperature of 30
C. or more to maintain the aeration tank (6
During the process in 0), it is possible to prevent the efficiency of the nitrification reaction or the like from being lowered by a low outside air temperature.

Further, inside the anaerobic fermenter (30),
A stirring blade (32) is provided for effectively mixing the anaerobic microorganisms and the wastewater. The inside of the anaerobic fermenter is also provided with a sludge discharge valve (35), a sludge discharge baffle (33), and a scum crusher (31). The sludge discharge valve and the sludge discharge baffle serve to discharge sludge residue remaining inside the anaerobic fermenter. The scum crusher acts to remove scum formed on the upper inside of the anaerobic fermenter.

On the other hand, the sludge settled in the lower part of the below-described multi-inclination sedimentation tank (80) is transferred to the inside of the anaerobic fermentation tank (30) by a third transfer path indicated by an arrow d in FIG. . Dephosphorized microorganisms contained in the transported sludge are activated under anaerobic conditions in an anaerobic fermenter,
Phosphate phosphate ions in the microbial cells (PO ₄ ^{3 -)} and released in the form of, it accumulates an organic acid anaerobic fermentor in the body.
The dephosphorus microorganisms in the aeration tank, which is an energy source for ingesting phosphorus by performing metabolism in the aeration tank (60), generate much more phosphorus than the amount of phosphorus released in the anaerobic fermentation tank. Ingest and remove.

The anaerobic fermenter (30) has a retention time of about 1.5 to 2.5 days for the dephosphorus microorganism so that the anaerobic fermentation is maintained due to the production of organic acids and the methanation does not proceed. It is desirable to operate so as to control the temperature.

(C) Step of Activating Aerobic Microorganism FIG. 3 schematically shows a cross-sectional structure of a microorganism activating tank (40) according to the present invention. An inlet (45) into which a part of the sludge containing aerobic microorganisms is conveyed and flows is provided at an upper part of the microorganism activating tank, and an outflow including the aerobic microorganisms activated in the microorganism activating tank. An outlet (46) for discharging water is provided, and a disc-type diffuser (41) is provided at the bottom thereof. Further, a valve (43) for discharging a residue inside the activation tank is provided at a lower portion of the microorganism activation tank.

As described in detail below, the sludge is transferred from the discharge end of the aeration tank (60) to the microbial activation tank (40) along a first transport path indicated by an arrow b in FIG. Can supply. By flowing the external air into the inside of the microbial activation tank through the air diffuser (41), the inside of the microbial activation tank is maintained in an aerobic atmosphere, and only the aerobic microorganisms in the sludge are selectively activated. Be transformed into

On the other hand, inside the microbial activation tank (40), there is provided an internal activation tank (44) composed of a porous wall. A bioclaude (42; soil microbial carrier) containing about 1% by weight of cultured microorganisms such as bacillus microorganisms and actinomycets is introduced.

The microorganisms filled in the bioclaude (42) are activated and grow under an aerobic atmosphere in the microorganism activation tank (40). The activated Claude microorganisms
It is separated from the bioclaude and discharged from the outlet (46) together with the activated aerobic microorganisms in the microorganism activation tank. Since the microorganisms filled in the bioclaude have a viability that can be adapted to high-concentration wastewater, even if they come into contact with high-concentration organic matter in the aeration tank (60), they will be active, as described later. Shows substance metabolism.

The transported sludge that has flowed into the microbial activation tank (40) may contain microorganisms that interfere with the sludge bulking, ie, solid-liquid separation, such as fungi containing filamentous bacteria. is there. The growth of such fungi is suppressed under the aerobic atmosphere in the microorganism activation tank, and the subsequent solid-liquid separation step is facilitated. Moreover, the microorganisms that decompose organic substances are operated in an aerated state in the microorganism activation tank, so that the organic substance biosorption ability can be improved. In order to suppress the growth of microorganisms such as fungi and maximize the activation of aerobic microorganisms, the microorganism activation tank is desirably operated with a residence time of about 1.5 to 2.0 days. .

(D) Mixing Step In the mixing tank (50), the wastewater treated in the anaerobic fermentation tank (30), the effluent from the microbial activation tank (40), and the condensate from the denitrification tank (70) described below. Forcibly mixing different properties such as sludge conveyed through the tube and, if necessary, filtrate from the dehydrator (100), and sending the mixture to the aeration tank (60). . Here, by uniformly mixing the microorganisms contained in the effluent from the microorganism activation tank with the food substance, a uniform action of the activated microorganisms in the aeration tank is induced.

(E) Dephosphorization and Nitrification Step of Ammonia Nitrogen FIG. 4 schematically shows the structure of the aeration tank (60). At one end of the aeration tank, an opening (62) through which the mixture obtained in the mixing tank (50) flows is formed, and at the other end, wastewater treated in the aeration tank is provided. An outlet (64) for discharging is formed. The bottom of the aeration tank is inclined at a predetermined angle, for example, 7 °, in order to prevent sludge from accumulating in the tank and to facilitate mixing action by air supply. The inside of the aeration tank is divided into a plurality of compartments by a plurality of partition walls. For example, the inside of the aeration tank shown in FIG.
6), the four compartments (60a, 60b, 60c, 6
0d).

When the external air flows into the aeration tank (60) through the air inlet pipe (61), the inside of the aeration tank is maintained in an aerobic atmosphere. It is desirable to maintain the amount of dissolved oxygen inside the aeration tank at 0.5 to 2.0 mg / L.

On the other hand, when nitrification proceeds rapidly in the aeration tank (60), the content of alkaline substances in the wastewater becomes a factor limiting the nitrification step. In addition, it is preferable that the amount of dissolved oxygen inside the aeration tank is maintained at different values depending on the compartment.
For example, in the aeration tank having the structure shown in FIG. 4, the first and fourth compartments (60a, 60a, 60a, 60b) are located at the inflow end of the aeration tank provided with the opening (62) and the outlet end provided with the outlet, respectively.
The amount of dissolved oxygen in 60d) is about 1.5 to 2.5 mg / L
And the amount of dissolved oxygen in the second and third compartments (60b, 60c) located between the inflow end and the outlet end is set to 0.
It is preferred to keep it at 5 to 1.5 mg / L. The dissolved oxygen amount in the second compartment (60b) adjacent to the inflow end is set to 1.0
It is particularly preferable to maintain the amount of dissolved oxygen in the third compartment (60c) adjacent to the outlet end at 0.5-1.0 mg / L while maintaining the concentration at ~ 1.5 mg / L. As described above, by keeping the dissolved oxygen concentration in the aeration tank relatively low, the aeration cost for the aerobic treatment can be kept to a minimum.

The decomposition of organic substances and the steps of denitrification and dephosphorization by the metabolic action of aerobic microorganisms in the aeration tank are as follows:
It is as follows.

First, the aerobic microorganisms are activated in the microbial activation tank (40) under superaeration conditions, and then flow into the aeration tank (60) in a state where the biological adsorption ability of the bait component is maximized. The decomposition reaction of organic matter by the metabolic action of aerobic microorganisms in the aeration tank is expressed by the following equation.

[0045]

Embedded image

The growth amount of new cells based on the amount of BOD thus removed is about 0.5 kg MLVSS / Kg BOD rem.

On the other hand, ammonia nitrogen is nitrified as follows.

[0048]

Embedded image

For nitrification of 1 mg / L of ammoniacal nitrogen, 4.6 mg O ₂ / L of oxygen and alkaline substances corresponding to 7.1 mg CaCO ₃ / L are consumed. As described above, in the second and third compartments (60b, 60c) located between the inflow end and the outlet end of the aeration tank (60), the dissolved oxygen amount is adjusted to 0.5 to 1.5 mg / L. In particular, by adjusting the concentration around 1.0 mg / L, rapid nitrification can be suppressed, and the nitrification inhibition phenomenon due to insufficient alkalinity can be prevented.

The dephosphorization step in the aeration tank (60) comprises:
It is explained as follows. That is, the anaerobic fermenter (3)
The dephosphorylated microorganisms that released the intracellular phosphorus in the form of phosphoric acid in step 0) may take up a relatively large amount of phosphorus when synthesizing cytoplasmic constituents under an aerobic atmosphere in an aeration tank. Become. For example, the amount of phosphorus released by dephosphorylated microorganisms in the form of phosphoric acid in an anaerobic fermenter and the amount of phosphorus taken by dephosphorized microorganisms in an aerobic atmosphere in an aeration tank are about 1:
It is maintained at a ratio of about 1.5. As described above, when the dephosphorized microorganism synthesizes a cytoplasmic constituent substance in the aeration tank, phosphorus is excessively taken up (luxury uptake) into the cell, thereby performing the dephosphorization step.

Based on the use of dephosphorylated microorganisms selectively activated in the anaerobic fermenter (30) to improve the dephosphorization capacity of the wastewater treatment apparatus, the following coagulation sedimentation tank (9) is used.
By the coagulation treatment in 0), the amount of chemical consumption required for the dephosphorization step can be minimized, and the water quality can be improved.

In the process of decomposing organic matter by the metabolic action of aerobic microorganisms in the aeration tank (60), a part of the sludge is discharged from the outlet (64) at the discharge end of the aeration tank in FIG. Is transported to the microorganism activation tank (40) along the first transport path indicated by. Such transport sludge contains aerobic microorganisms as described above.
The wastewater treated in the aeration tank flows into the denitrification tank via the outlet through the inlet (77) of the anoxic denitrification tank (70) while being mixed with the microorganisms.

(F) Denitrification Step FIG. 5 shows a denitrification tank (70) composed of a contact filter medium layer (70a) and a mixed layer (70b). The contact filter medium layer is filled with a contact filter medium (75) that performs a denitrification action of the mixed solution aerated in the aeration tank (60). The nitrogen gas denitrified in the contact filter medium layer is degassed in the mixed layer (70b) provided with the stirring blade (73), and the denitrified mixed solution is
Through the upper outflow weir (71; weir), the outlet (7
It is discharged through 2).

The mixture of microorganisms and wastewater flowing from the aeration tank (60) passes through the contact filter medium layer (70a) filled with the contact filter medium (75), and the microorganisms and the like adhere to the contact filter medium. It grows while performing a denitrification reaction using untreated organic matter and nitrate in wastewater. As microorganisms adhere to and grow on the contact filter medium, a sludge blanket is sequentially formed in the contact filter medium layer to perform a biological filtration action, thereby improving the solid-liquid separation effect of wastewater and sludge. You.

In the denitrification tank (70), microorganisms concentrated in the contact filter medium layer (70a) using sludge from untreated organic matter and nitrate contained in the mixture flowing from the aeration tank (60). , A denitrification reaction of the following formula is performed.

[0056]

Embedded image

In one example of the processing result, through the denitrification step,
Oxygen 2.86 g O ₂ / g N and alkaline substance 3.6 g CaCO ₃ /
gN is produced, and the residence time in the denitrification tank is about 0.75-1.
It is about 25 days, and the denitrification rate in this step is 0.03 g N /
g MLVSS / d.

In the denitrification tank (70), a part of the sludge is filtered and separated by the biological filtration action of the contact filter medium layer (70 a) and settles at the lower part, and then passes through the sludge discharge port (76). It is transported to the mixing tank (50) by the transport path c. As a result, the microorganism concentration in the aeration tank (60) can be kept constant.

The wastewater that has passed through the denitrification step passes through the discharge port (72) of the denitrification tank (70), and passes through the lower multi-tilt settling tank (8).
0).

(G) Separation Step FIG. 6 schematically shows the structure of a multi-inclination type settling tank (80) typically used as a primary settling tank.
The multiple inclined sedimentation tank has a plurality of inclined sedimentation plates (8
5) and a pair of inclined sediment pairs (86) supporting both ends of the inclined sedimentation plate, and a lower settling sludge reservoir.

In general, when each step for nutrient removal is operated for a long residence time of sludge, the cells lose their activity due to excessive oxidation, so that the fine cellular material which is dispersed and does not sediment, ie, the pin Flock (pin fl
oc) occurs. The multiple inclined sedimentation plate (85) is installed to prevent the occurrence of such pin flocks.
It is configured to increase the contact area with sludge.
That is, the wastewater flowing into the multiple inclined settling tank (80) flows upward along the surface of the inclined settling plate (85),
It flows over the sedimentation plate and along the surface of the next sedimentation plate. By installing a plurality of inclined sedimentation plates, the contact area with the sludge is increased, and the occurrence of pin flocks is suppressed.

After the aeration treatment and the denitrification treatment, the treated wastewater flowing into the multi-inclination sedimentation tank (80) is separated into a solid and a supernatant by gravity. Such solid-liquid separation is enhanced by suppressing the growth of fungi such as filamentous bacteria in the microbial activation tank (40), as described above. On the other hand, the solids settle at the lower end of the multi-slant settling tank and remain as sludge. As for the sludge, phosphorus-free microorganisms in a state where the residual concentration of nitrate is almost zero in an anoxic state become a more preferential state. The sludge flows from the sludge discharge port (83) into the anaerobic fermenter (30) along the third transport route d in FIG. 1, and the dephosphorized microorganisms in the sludge are activated.

The supernatant liquid separated into solid and liquid in the multi-inclination type sedimentation tank (80) flows into the coagulation sedimentation tank (90) via the upper outlet (82), and the residual phosphorus and suspended solids are suspended. Chemical treatment is performed so that the object is completely removed.

(H) Step of Removing Residual Phosphorus and Suspended Solids FIG. 7 schematically shows an example of the internal structure of the coagulation / sedimentation tank (90). An introduction pipe (92) into which the supernatant flows from the multi-inclination settling tank (80);
An injection tube (94) is provided for injecting a chemical such as sulfuric acid or a metal salt. A stirring blade (93) for appropriately mixing the supernatant flowing from the inlet tube and the chemicals flowing from the inlet tube is located below the inlet tube (94). Separation walls (96, 97, 98) and the like separated at predetermined intervals are provided inside the coagulation sedimentation tank.
A mixing chamber for the chemical and the supernatant, a flocculation chamber and a precipitation separation chamber are formed.

The operation in the coagulation sedimentation tank (90) will be described in detail. First, sulfuric acid is injected from the injection pipe (94) into the supernatant flowing into the coagulation sedimentation tank from the introduction pipe (92), and the stirring blade ( The mixture is adjusted according to 3) and the supernatant is adjusted to neutrality, ie the pH is preferably adjusted to 7.2 to 7.8, particularly preferably to about 7.5. Add the injection tube (94) to the neutralized supernatant.
, A predetermined amount of a metal salt, for example, an iron salt is injected and mixed.
Thereafter, the mixture is subjected to a chemical reaction between the iron salt and the supernatant to remove residual phosphorus and suspended solids in the supernatant.

The reaction formula for removing the residual phosphorus is as follows. _{^{Fe 3 + + PO 4 3 -}} ------ → Fe (PO 4) That is, the residual phosphorus in the supernatant can be reacted directly with the iron salt, are removed as an insoluble salt.

The iron in the iron salt reacts with the hydroxyl group in the supernatant as shown in the following reaction formula to form iron hydroxide and precipitate.
Removed. Fe ^{3 +} +3 (OH ⁻ ) ―――――― → Fe (OH) ₃ At this time, the suspended solids remaining in the supernatant are coagulated and precipitated together due to the viscosity of the precipitated iron hydroxide. And removed.

The arrow shown in the right half of FIG. 7 indicates a process in which the mixture of the supernatant and the chemical flows in the coagulation / sedimentation tank (90). Inside the primary separation wall (96), rapid mixing of the supernatant and chemicals takes place in the space defined by the separation wall for about 5 minutes while the impeller (93) rotates. Next, the mixed energy of the obtained liquid mixture decreases as it passes over the end of the primary separation wall. Aggregation of chemical sludge and growth of sludge particles progress between the primary separation wall and the secondary separation wall (97). As the mixture passes over the secondary separation wall (97), the residual mixing energy of the mixture disappears, so that sludge of the mixture precipitates out over the end separation wall (98). The final treated water generated in the coagulation sedimentation tank is discharged to the outside through a baffle (99) installed at the upper part of the coagulation sedimentation tank, and the sludge is discharged from the discharge port (91) installed at the lower part of the coagulation sedimentation tank. Then, it is transferred to the dehydrator (100) along the path indicated by the arrow h in FIG.

The dehydrator (100) has arrows f and g in FIG.
The sludge discharged from the anaerobic fermentation tank (30) and the sludge from the multiple sedimentation tank (80) both flow in along the paths indicated by. The sludge that has flowed into the dehydrator (100) is subjected to a dehydration treatment to be separated into a dehydrated sludge and a dehydrated filtrate. Dewatered sludge has a high organic content and is almost free of toxic substances, so it can be reused in fertilizer through solid composting. The filtrate generated by the dehydration flows into the mixing tank (50) via the transport path e in FIG.

[0070]

The present invention will be described below with reference to examples.
The present invention is not limited by this embodiment.

Using the wastewater treatment apparatus shown in FIG. 1, livestock wastewater generated in a scraper type pig house was purified. The biological oxygen demand (BOD), chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) of livestock wastewater subjected to the purification treatment were as shown in Table 1. .

[0072]

[Table 1]

Table 2 shows the specifications of the wastewater treatment equipment used in this test example.

[0074]

[Table 2]

Here, the pH meter is a coagulation sedimentation tank (90)
A transfer pump for transferring the wastewater in the storage tank (20) to the anaerobic fermenter (30); and a transfer pump for transferring sludge in the apparatus. The mixing motor rotates the mixing stirring blades (32, 73) in the anaerobic fermentation tank (30) and the denitrification tank (70), and the mixing stirring blade (93) in the coagulation sedimentation tank (90). And the blower is for supplying air to the microbial activation tank (40) and the aeration tank (60).

The bioclaude (42) charged into the microbial activation tank (40) contained about 1% of the weight of the bioclaude by separately cultured Bacillus microorganisms and actinomycetes. From the denitrification tank (70) to the mixing tank (5
The transfer rate of the sludge from the multi-slope sedimentation tank (80) to the anaerobic fermentation tank (30) is 75%, and the microbial activation from the aeration tank (60) is 125%. The sludge transfer rate to the tank (40) was 100%.

The whole amount of the dehydrated filtrate was conveyed from the dehydrator (100) to the mixing tank (50). The total volume of the apparatus excluding the storage tank (20) is 30.3 L, and air is 15 to 20 L / m.
in blast.

In the upper part of the anaerobic fermenter (30),
After about 10 days, scum formed. The oxidation-reduction potential (ORP) value is about -300 or less, and when considering the dilution effect by transportation, the soluble phosphorus content of the effluent increases about 1.5 to 2.2 times, and the soluble COD increases. The content of
It did not increase significantly. However, the total nitrogen (TN) was reduced by about 32.6%, and the pretreatment by the anaerobic fermenter (30) significantly reduced the subsequent nitrogen load and significantly reduced the amount of oxygen required for nitrification. Was.

The mixture of microorganisms in the aeration tank (60)
Maintained at a concentration of 1,000 to 14,000 mg / L, sludge production is about 0.5 / kg BOD removed.
kg MLVSS, and the discharged sludge concentration is about 18,000
mg / L. The dissolved oxygen amount in the aeration tank (60) was 2.0 mg / L in the compartment (60a) located at the inflow end, and 1 to 1.5 mg / L in the compartment (60b) adjacent to the inflow end. It was maintained at 0.5-1 mg / L in the compartment (60c) close to the head and 2.5 mg / L in the compartment (60d) located at the discharge end.
The pH in the aeration tank was 7.7 to 8.2. The alkalinity was reduced to about 2,325 mg CaCO ₃ / L in the nitrification step, forming good conditions that could reduce the required amount of flocculant due to hydroxide formation in the subsequent flocculation step.

The effluent quality of the multi-slant settling tank (80) is as follows:
BOD 128mg / L, TN 145mg / L and TP 75m
g / L, BOD and TN showed high removal rate of 95% or more, and TP removal rate was 86%. The effluent water quality of the coagulation sedimentation tank (90) in which an iron salt was added to the supernatant of the multi-inclination sedimentation tank (80) to perform coagulation sedimentation was BOD 42 mg /
L, stable solids (SS) 33 mg / L, TN 45 mg / L and TP 6.2 mg / L stable water quality. On this occasion,
Approximately four times the suspended solids (SS) in the multi-slant sedimentation tank (80) were generated, and 13.6 g / d of coagulated sludge was generated in the multi-slant sedimentation tank. / d, the sludge generated per COD removal of livestock wastewater is
The SS per 0.4 kg of COD removed was 0.4 kg.

The results of treating livestock wastewater according to this example are as shown in Table 3. During the treatment process, an aeration tank (6
The SVI of the microorganism mixture of 0) was 62 to 115, and the oxygen demand was 58 to 105 mg O / L / h, but the amount of oxygen actually supplied was defined assuming that the oxygen transfer rate was 0.1. About 36
It was 0 mg O / L / h. Therefore, the dissolved oxygen concentration in the aeration tank (60) was kept low, but the required amount was a value that could be satisfied. Thus, by controlling the dissolved oxygen concentration as in the present invention, a considerable saving in processing costs was achieved.

[0082]

[Table 3]

[0083]

As is evident from the above results, the present invention makes it possible to effectively and economically remove organic substances, nitrogen and phosphorus when treating high-concentration livestock wastewater, and to achieve a stable treatment. Excellent treated water quality can be secured economically. INDUSTRIAL APPLICABILITY The present invention can be applied to a small-scale wastewater generation facility, and can effectively solve environmental pollution problems related to livestock wastewater.
Also, sludge generated by the treatment of livestock wastewater, unlike municipal sewage, is not likely to contain heavy metals or other harmful pollutants. Therefore, the sludge can be composted and effectively used as a solid fertilizer.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a wastewater treatment process according to the present invention.

FIG. 2 is a schematic diagram of an anaerobic fermenter used in the wastewater treatment apparatus of the present invention.

FIG. 3 is a schematic diagram of a microorganism activation tank used in the wastewater treatment device of the present invention.

FIG. 4 is a schematic view of an aeration tank used in the wastewater treatment apparatus of the present invention.

FIG. 5 is a schematic diagram of a denitrification tank used in the denitrification treatment of the present invention.

FIG. 6 is a schematic view of a multi-tilt settling tank used in the wastewater treatment apparatus of the present invention.

FIG. 7 is an internal structural diagram of a coagulation sedimentation tank used in the wastewater treatment device of the present invention.

[Explanation of symbols]

 10: Wastewater treatment apparatus 20: Storage tank 30: Anaerobic fermentation tank 40: Microbial activation tank 42: Bioclaude 44: Internal activation tank 50: Mixing tank 60: Aeration tank 66: Partition wall 70: Denitrification tank 75: Contact Filter media 80: Multiple inclined sedimentation tank 84: Multiple inclined sedimentation plate 90: Coagulation sedimentation tank 100: Dehydrator

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-202196 (JP, A) JP-A-6-63588 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C02F 3 / 34,3 / 12

Claims (10)

(57) [Claims] (A) a step of storing the effluent solid-liquid separated from the wastewater in a storage tank to equalize the concentration and the flow rate; (b) a step of hardly decomposing the effluent equalized in the storage tank Anaerobic microorganisms in an anaerobic fermenter to hydrolyze the organic matter to a state that is easy for the subsequent microorganisms to ingest, thereby activating the phosphorus-free microorganisms; (c) from a dissolved oxygen-regulating aeration tank, Aerobic microorganisms in the sludge conveyed to the microbial activation tank where the soil microbial carrier is present were selectively activated in the microbial activation tank to increase the biological adsorption capacity, and were filled in the soil microbial carrier. Growing the microorganisms, activating the aerobic microorganisms; (d) the effluent of the microbial activation tank, the effluent of the anaerobic fermentation tank, and the sludge from the denitrification tank, and, if necessary, anaerobic. Fermentation tank, primary sedimentation tank and coagulation sedimentation tank Mixing a filtrate sent from a dehydrator for separating sludge into solid and liquid in a mixing tank; (e) introducing the mixed liquid into the dissolved oxygen-controlled aeration tank to treat organic substances and phosphorus, (F) denitrifying nitrate of the liquid treated in the aeration tank in anoxic condition by utilizing endogenous respiration of microorganisms; (g) denitrification treatment (H) separating residual phosphorus and suspended solids in the coagulating sedimentation tank from the supernatant liquid separated in the primary sedimentation tank. A method for treating wastewater, comprising the step of removing and discharging treated water. 2. The wastewater treatment method according to claim 1, further comprising a step of supplying a part of the microorganism sludge separated in the primary sedimentation tank to a microorganism activation tank. 3. The aeration tank treatment step is performed in a multistage aeration tank, and the dissolved oxygen concentration in the interval chamber in the aeration tank is adjusted to 0.5 to 1 mg / L. Wastewater treatment method. 4. The wastewater treatment method according to claim 1, wherein in the coagulation / sedimentation tank treatment step, a metal salt is injected after adjusting the pH in the coagulation / sedimentation tank to 7.2 to 7.8. 5. A step of solid-liquid separating a settling sludge of the coagulating sedimentation tank, a discharge sludge of the anaerobic fermentation tank and a sludge separated in the primary sedimentation tank by a dehydrator, and transporting the dehydrated filtrate to a mixing tank. The wastewater treatment method according to claim 4, further comprising: 6. The wastewater treatment method according to claim 1, wherein the denitrification tank and the anaerobic fermentation tank are separated from each other in order to eliminate the inhibition of the dephosphorization microorganisms by nitrates. 7. A storage tank for storing the effluent solid-liquid separated from the wastewater to equalize the concentration and the flow rate; and B. A anaerobic microorganism is located downstream of the storage tank. An anaerobic fermenter provided with; (C) an internal activation tank containing a soil microbial carrier and a microbial activation tank provided with an aeration tube; (D) an effluent of each of the microbial activation tank and the anaerobic fermenter; The sludge from the denitrification tank, and, if necessary, an inflow port into which a filtrate sent from a dehydrator for solid-liquid separation of sludge from the anaerobic fermentation tank, the primary sedimentation tank and the coagulation sedimentation tank is provided. A mixing tank for receiving and mixing the inflow from the inlet; (E) a dissolved oxygen controlled aeration tank connected downstream of the mixing tank; (F) a denitrification tank connected downstream of the aeration tank. (G) a primary sink connected downstream of the denitrification tank; (H) a wastewater treatment apparatus comprising: a coagulation sedimentation tank connected downstream of the primary sedimentation tank. 8. The wastewater treatment apparatus according to claim 7, wherein the microorganism activation tank includes an internal activation tank filled with a soil microorganism carrier. 9. The wastewater treatment apparatus according to claim 7, wherein the aeration tank is a multistage aeration tank. 10. A dehydrator and sludge from each of the primary sedimentation tank, coagulation sedimentation tank and anaerobic fermentation tank,
The wastewater treatment apparatus according to claim 7, further comprising a supply pipe for supplying the dewatering machine.