JP2002361279A - Method and apparatus for treating waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove or suppress the generation excessive sludge to the utmost and to perform sludge treatment without occurrence of odor. SOLUTION: Raw waste water is let to flow into an inflow tank 2, electron acceptor adjusting water 11 for micro-organisms is mixed from an electron acceptor adjusting water storage tank 1 to the inflow tank 2 and the raw waste water is aerated under a condition that the amount of dissolved oxygen is substantially 1 mg/L or less. Subsequently, the aerated treated water is sent to a reaction tank 3 and is aerated under a condition that the amount of dissolved oxygen is substancially 1 mg/L or less. Subsequently, the treated water is treated in such a manner that the sludge is settled and separated in a sedimentation tank 4 and the supernatant water is discharged. Subsequently, the settled sludge is sent to a sludge digesting tank 5 and is aerated under a condition that the amount of dissolved oxygen is substancially 1 mg/L or less. The supernatant water of the aerated water is returned to the electron acceptor adjusting water storage tank 1 as the electron acceptor adjusting water 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a wastewater treatment method and a wastewater treatment apparatus for purifying wastewater containing organic matter by microbial treatment.

[0002]

2. Description of the Related Art As a method for purifying wastewater containing organic substances by microbial treatment, activated sludge treatment is widely used in sewage treatment, industrial wastewater treatment and the like.

The process of a general activated sludge treatment method is as follows. First, inflow wastewater that has been subjected to pretreatment such as filtration and precipitation is sent to an aeration tank, and activated sludge is stirred and aerated to mineralize water-soluble organic compounds and colloidal organic compounds in the wastewater.

Next, the wastewater is sent to a sedimentation tank to separate sludge.
After sedimentation, the supernatant water is sterilized so as to be below the legal standard value, and then discharged to rivers and the like. Sludge settled in the lower layer of the sedimentation tank is sent to the storage tank, and when it accumulates in a predetermined amount, it is appropriately disposed of. If necessary, a part of the sludge in the sedimentation tank may be returned to the aeration tank and used for adjusting the concentration of microorganisms in the sludge in the aeration tank.

The above-mentioned conventional activated sludge treatment method generally uses an aerobic microorganism, keeps the dissolved oxygen (DO) in the aeration tank at a high level, promotes the active growth of the aerobic microorganism, and promotes the aerobic respiration. Oxidatively decomposes organic waste as a substrate. For this reason, the dirt in the wastewater coagulates together with the dead bodies of microorganisms, and a large amount of sludge is generated.

Although a part of the sludge is returned to the aeration tank as described above, a large amount of excess sludge has been subjected to landfill treatment, incineration treatment, and the like. However, surplus sludge also contains harmful substances, which itself causes various environmental pollutions. Therefore, it is desired that surplus sludge should be produced as little as possible.

Further, in the activated sludge treatment method, since odor is generated in each treatment step, a deodorizing device must be installed, and equipment costs, running costs, and the like are burdensome.

On the other hand, there is known a sludge treatment method using anaerobic or aerobically anaerobic microorganisms in combination with the above-mentioned activated sludge treatment method. However, since a new anaerobic treatment device is required, new equipment is required. There is a problem that the cost and the burden of the running cost increase.

For these reasons, various studies have been conducted for the purpose of reducing the amount of generated sludge and taking measures against deodorization, and Japanese Patent Application Laid-Open No. 11-47787 has been proposed as an example. The wastewater purification system is based on microbial treatment of wastewater using anaerobic and aerobically anaerobic microorganisms. In order to maintain this, a method is employed in which the supernatant water and the settled sludge provided after the aeration tank are returned to the aeration tank at a predetermined ratio.

[0010] However, this wastewater purification system has a problem that a sufficient amount of microorganisms cannot be maintained depending on the inflow conditions and aeration conditions of raw wastewater, and stable purification treatment cannot be performed. In addition, since the supernatant water and the settled sludge of the settling tank are returned to the aeration tank at a predetermined ratio, there is a problem that the control system becomes complicated.

[0011]

DISCLOSURE OF THE INVENTION The present invention has been proposed in view of the above-mentioned situation, and the first object of the present invention is to suppress the generation of excess sludge at all or to the utmost and to carry out the method without odor. It is an object of the present invention to provide a wastewater treatment method and a wastewater treatment device that can be used.

It is a second object of the present invention to provide a wastewater treatment method and a wastewater treatment apparatus capable of stably and efficiently purifying a microorganism by always maintaining a required amount of microorganisms. .

Further, a third object of the present invention is to provide a wastewater treatment method and a wastewater treatment which can be carried out at a low cost with a simple system configuration, which can reduce excess sludge treatment cost and installation cost of a deodorizing device. It is to provide a device.

[0014]

As a result of repeated studies, the present inventor has found that microorganisms can be used as an energy source in the treatment of microorganisms (anaerobic or facultative anaerobic microorganisms) in wastewater containing microorganisms. The present inventors have found that the above problem can be solved by adjusting the electron acceptor by focusing on the electron acceptor to be used. That is, the wastewater treatment method of the present invention, the raw water wastewater containing organic matter, mixed with microbial electron acceptor adjusted water,
Aeration under the condition that the dissolved oxygen amount is substantially 1 mg / L or less,
Next, the sludge contained in the aeration-treated water is subjected to sedimentation separation treatment, and then the precipitated sludge is dissolved in an amount of dissolved oxygen of substantially 1 m.
The aeration is performed under the condition of g / L or less, and the supernatant water is returned to the raw wastewater as electron acceptor adjusted water.

Further, in the wastewater treatment method limited to the preferred embodiment of the present invention, an electron acceptor adjusted water is mixed into raw wastewater containing organic matter, and aeration is performed under the condition that the dissolved oxygen amount is substantially 1 mg / L or less. Then, the first step of growing deodorant microorganisms, and the treated water of the first step, the dissolved oxygen amount is substantially 1
a second step of performing denitrification treatment with fermenting microorganisms by aerating under the condition of not more than mg / L, and a third step of subjecting the treated water of the second step to precipitation separation treatment and dephosphorization treatment by phosphorus-absorbing microorganisms And aerating the settled sludge of the third step under the condition that the amount of dissolved oxygen is substantially 1 mg / L or less to digest excess sludge with sludge digestive microorganisms and supply the electron acceptor to be supplied to the first step. A fourth step of producing conditioned water.

The wastewater treated by the wastewater treatment method of the present invention includes all domestic wastewater or industrial wastewater such as human wastewater, livestock manure wastewater, and industrial wastewater. In the aeration treatment in the present invention, a normal method of feeding air into the aeration tank to agitate and aerate the contents is sufficient. The amount of dissolved oxygen (DO) in the aeration tank is adjusted by adjusting the air supply amount. ) Is maintained in the above range.

The electron acceptor conditioned water used in the present invention is a liquid containing a large amount of a chemical substance that is used as an energy source by microorganisms, and specifically includes nitrate and sulfur compounds formed microbiologically. Is an inorganic solution containing a large amount of phosphate, phosphate and the like.

In the present invention, the amount of dissolved oxygen is substantially 1 mg / L.
The reason for the following is to supply a minimum amount of oxygen to the microorganism and to promote the consumption of electron acceptors other than oxygen, thereby promoting the active growth of the microorganism. Also, when the concentration is 1 mg / L or more, the aerobic microorganisms actively grow and the activated sludge treatment method is driven by oxygen.

Here, "substantially" means 1 mg / mg.
Even if it is L or more, it is intended to include a fine difference range in which the same effect as the present invention can be obtained. Note that the dissolved oxygen amount may be zero. This means that the microorganism includes a state of consuming more oxygen than the supplied oxygen amount.

In the first step of the preferred embodiment, the electron acceptor of the deodorant microorganism is oxygen-active. Under the low dissolved oxygen content described above, deodorant microorganisms begin to use the nitrate contained in the electron acceptor conditioned water, and the oxygen entering the area is also used at the same time.

The deodorant microorganism is, for example, a chemically synthesized bacterium, a methophile, or the like. The deodorant microorganisms grown in the first step are used in all steps, and the generation of odor in all steps can be microbiologically suppressed. It should be noted that chemically synthesized bacteria produce nitric acid, and Methofile bacteria synthesize sulfide. These are used in the second and subsequent steps.

In the first step, in addition to the deodorant microorganisms, sulfur-reducing microorganisms (including archaebacteria) which promote the growth of the fermentative microorganisms used in the second step are also grown. The electron acceptor of the sulfur-reducing microorganism is a sulfide contained in the water for adjusting the electron acceptor. The phosphate contained in the electron acceptor conditioning water is effective in further promoting the growth of deodorant microorganisms and sulfur-reducing microorganisms.

In the second step, most of the organic substances contained in the treated water transferred from the first step are fermented and digested by the fermenting microorganisms. The fermenting microorganisms include, for example, yeast, Bacillus, Alcaligenes, Clostridium, Pseudomonas, lactic acid bacteria and the like. These use nitrate contained in the electron acceptor preparation solution as an electron acceptor, and denitrification (N ₂
The action of producing and releasing gas is performed. The electron donor is an organic substance and is decomposed into an organic substance having a smaller molecular weight. In addition, odor substances, which are volatile substances by fermentation, are consumed by the aforementioned deodorant microorganisms.

In order to proliferate the fermentative microorganism, products such as H ₂ and CO ₂ produced by the fermentative microorganism, especially H 2
₂ is decomposed by using a sulfur compound such as a sulfur-reducing microorganism as an electron acceptor, whereby the active growth of the fermenting microorganism is promoted, and the fermenting microorganism can always be maintained at a high concentration.

In the third step, the treated water of the second step is allowed to stand for a predetermined time, whereby sludge in the treated water precipitates and is separated from the supernatant water. In the third step, the organic matter is consumed by the fermenting microorganisms, and there is no oxygen supply by aeration, so that the microbial environment is anaerobic, and the growth of the fermenting microorganisms stops. Instead, a sulfur-reducing microorganism or the like having an electron acceptor with the sulfur compound increased through the first step and the second step grows, and the sludge is digested by these microorganisms, so that the amount of sludge decreases. Further, a phosphorus-absorbing microorganism using a sulfur compound as an electron acceptor grows to perform a phosphorus removal treatment.

The supernatant water treated in the third step is further subjected to a sterilization treatment, if necessary, and then discharged into a river or the like. The settled sludge is transferred to the next fourth step.

In the fourth step, the settled sludge generated in the third step is stored, and sludge digestive microorganisms using oxygen, sulfur compounds and the like as electron acceptors are actively grown. The sludge digestive microorganisms include methanogens, sulfur-reducing bacteria, chemically synthesized bacteria, methofile bacteria, and the like, and when these are actively grown, digestion of the sludge further proceeds, and the amount of excess sludge is reduced.

The fourth step is an inorganic solution in which most of the organic matter in the sludge is in a digested state, and has almost no active growth of fermentable microorganisms, and is substantially odorless. The sludge digestive microorganisms described above digest the sludge to generate nitrates, sulfur compounds, phosphates, and the like, thereby generating an inorganic solution rich in these components. The supernatant water generated in the fourth step is directly returned to the first step as electron acceptor adjusted water, or once collected in a dedicated storage tank, and then the concentration of which is adjusted if necessary in the first step. Will be returned to Hereinafter, the waste liquid is purified in the above-described cycle.

The waste liquid treatment apparatus for effectively carrying out the above-described waste liquid treatment method of the present invention stores waste water raw water containing organic substances, mixes the electron acceptor conditioned water of microorganisms, and makes the dissolved oxygen amount substantially 1 mg. / L or less, an aeration tank for aeration, a sedimentation tank for precipitating treated water in the first aeration tank, and a sedimentation sludge in the sedimentation tank having a dissolved oxygen amount of substantially 1
a second aeration tank for aerating under the condition of not more than mg / L, and means for returning the supernatant water generated in the second aeration tank to the first aeration tank as electron acceptor adjusted water.

Further, the waste liquid treatment apparatus according to a preferred embodiment of the present invention comprises: an inflow tank for storing wastewater raw water and aerating the wastewater raw water under a condition in which the amount of dissolved oxygen is substantially 1 mg / L or less; The amount of dissolved oxygen in the treated water in the tank is substantially 1 mg.
/ L, a reaction tank for aeration and denitrification treatment, a sedimentation tank for precipitating treated water in the reaction tank, and a sedimentation sludge in the sedimentation tank, wherein the dissolved oxygen amount is substantially 1 mg / L or less. A sludge digestion tank that is aerated under the conditions described above, and an electron acceptor for storing supernatant water generated in the sludge digestion tank as electron acceptor adjusted water and mixing a predetermined amount of electron acceptor adjusted water into the inflow tank. And a conditioned water storage tank.

It may be provided before the electron acceptor conditioned water storage tank and the inflow tank for the raw wastewater, or may be provided behind the sludge digestion tank. Further, in order to maintain the dissolved oxygen amount in the above range, a dissolved oxygen amount measuring means is provided in each tank, and the air supply amount of the air supply means to be supplied to each tank is changed from the dissolved oxygen amount measuring means. Control is performed so that a predetermined dissolved oxygen amount is obtained according to the output information.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to FIG. In the figure, 1 is an electron acceptor adjusted water storage tank, 2 is a wastewater raw water inflow tank, 3 is a reaction tank, 4 is a sedimentation tank, 5
Is a sludge digester.

In the electron acceptor adjusted water storage tank 1, the electron acceptor adjusted water 11 returned from the sludge digestion tank 5 is stored. The electron acceptor conditioning water 11 includes a nitrate, a sulfur compound,
It is an inorganic solution containing a large amount of phosphate, and is used after diluted to an appropriate concentration as necessary. When the sludge treatment device is started, the electron acceptor conditioning water 11 generated by another sludge treatment device is supplied.

The raw wastewater inflow tank 2 is supplied with the raw wastewater 10 to be treated, is subjected to a pretreatment such as a screening process, and temporarily stores the wastewater raw water 10 to adjust the flow rate of the wastewater raw water that changes every moment. Is made. Further, a predetermined amount of the electron acceptor conditioned water 11 from the electron acceptor conditioned water storage tank 1 is mixed into the inflow tank 2, and the dissolved oxygen amount is 1 mg /
The aeration process is performed under the condition of L or less. Thereby, as described above, oxygen is used as the electron acceptor, and the electron acceptor conditioning water 11 is used.
Deodorant microorganisms grow while consuming the nitrate and the like contained in the water.

The treated water in the wastewater raw water treatment tank 2 is transferred to the reaction tank 2, and the amount of dissolved oxygen is 1 in the same manner as in the wastewater raw water inflow tank 2.
The aeration process is performed for a predetermined time (number of days) under the condition of mg / L or less. In the reaction tank 2, the fermenting microorganisms ferment and digest most of the organic substances in the treated water by using nitrate as an electron acceptor to generate and release nitrogen (denitrification). The products of fermenting microorganisms, in particular H ₂ is methemoglobin file bacteria, archaea, is consumed by the sulfur-reducing bacteria or the like, and the growth of fermenting microorganisms, organic matter digestion is promoted associated therewith. The odor components generated by the fermenting microorganisms are propagated in the inflow tank 2 and consumed by the transferred deodorant microorganisms.

With the ecological cycle of such microorganisms,
A large amount of organic matter in the treatment liquid is decomposed and consumed, and the amount of microorganisms in the reaction tank 2 can be kept stable. In the experiment, the MLSS (mixed liquid suspended solid) in the reaction tank 2 was reduced to 10%.
It could be maintained at around 000 mg / L.

The treated water in the reaction tank 3 is then transferred to the sedimentation tank 4, where the treated water is allowed to stand for a predetermined time (the number of days) to precipitate sludge contained in the treated water and separate from the supernatant water. In the sedimentation tank 4, the organic matter is mineralized, and oxygen and nitrate, which are the electron acceptors of the microorganisms, are deficient and in an anaerobic state, and the active growth of the fermenting microorganisms is stopped.

In the settling tank 4, the inflow tank 2 and the reaction tank 3
, Sulfur-reducing microorganisms that use this as an electron acceptor actively grow and digest digested sludge, so that the sludge capacity is reduced. Further, the phosphorus-absorbing microorganisms actively grow and consume phosphorus (dephosphorization), and the phosphorus component in the supernatant water decreases.

A part of the settled sludge in the settling tank 4 is returned to the reaction tank 3 if necessary, and is used for adjusting the concentration of microorganisms in the reaction tank 3. The remaining settled sludge is transferred to the next sludge digestion tank 5.
The supernatant water is subjected to a sterilization treatment if necessary, and then discharged 12.

In the sludge digestion tank 5, excess sludge transferred from the reaction tank 3 is subjected to aeration treatment under the condition of a dissolved oxygen amount of 1 mg / L or less to activate sludge digestive microorganisms using oxygen and sulfur compounds as electron acceptors. And sludge excess sludge to reduce the amount. In this sludge digestion tank 5, nitrate, sulfur compounds,
Electron acceptor adjusted water containing phosphate and the like is generated, and the electron acceptor adjusted water is supplied to the electron acceptor adjusted water storage tank 1.

In the above-described wastewater treatment apparatus, the inflow tank 2 and the reaction tank 3 for the raw wastewater are separately provided. However, if the flow rate of the wastewater is constant, the inflow tank 2 is omitted, and the flow into the reaction tank 3 is omitted. The function of the tank 2 may be provided.

Although the electron acceptor conditioned water storage tank 1 is provided before the wastewater raw water inflow tank 2, it may be provided behind the sludge digestion tank 5. Further, if necessary, a small amount of residual sludge settled in the lower layer of the electron acceptor adjusted water storage tank 1 may be returned to the sludge digestion tank 4 for re-digestion.

In the present invention, the BOD in the inflow tank 2 is 10
2,000mg / L or more can be processed, and BOD20
General wastewater of about 0 mg / L can be treated.

[0044]

EXAMPLES Specific examples according to the present invention are shown in Table 1.
The table shows the measured values of the environment before and after the treatment of wastewater according to the present invention.
The measured values of the discharge water (supernatant water) from the sludge digestion tank 4 are compared.

[0045]

[Table 1]

As shown in the above table, the treated water according to the present invention has cleared the standard value that can be discharged into a river. In addition, it was almost odorless in all treatment steps, and surplus sludge could be significantly reduced as compared with the conventional method. In addition, MLSS
Was constantly maintained at 5600 or more (conventionally, the microorganisms in the aeration tank decreased during the off season).

[0047]

According to the present invention as described above, by adjusting the electron acceptor of the microorganism and promoting the active proliferation of the microorganism required in each treatment step, the wastewater can be purified to an environmental standard value or less, and Sludge generation can be completely eliminated or minimized. In addition, all the processing steps can be performed in an odorless state. Therefore, it is possible to reduce the sludge treatment cost and the equipment cost of the deodorizing device and the like.

Further, according to the present invention, since the amount of microorganisms in the treatment step, especially in the reaction tank, can be kept in a stable state, even wastewater with a low BOD concentration can be stably and efficiently purified. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of a wastewater treatment apparatus for carrying out the present invention.

[Explanation of symbols]

 1 is an electron receptor adjusted water storage tank 2 is a wastewater raw water inflow tank 3 is a reaction tank 4 is a sedimentation tank 5 is a sludge digestion tank

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tamiko Sadae 1086-152 F-term (reference) 4D028 AB00 BD06 BD13 BD16 CA07 CC07 CC09 4D040 BB02 BB32 BB91 DD01 DD14 DD18 4D059 AA06 BA09 BA21 CA28 DA70

Claims (9)

[Claims] 1. A method for treating wastewater containing organic matter sludge, comprising mixing raw water of wastewater with adjusted water for electron acceptors of microorganisms and aerating the solution under the condition that the amount of dissolved oxygen is substantially 1 mg / L or less. The sludge contained in the treated water is subjected to sedimentation separation treatment, and then the precipitated sludge is dissolved in an amount of substantially 1 mg / ml.
A method for treating wastewater, comprising aerating under a condition of L or less and returning supernatant water to said raw wastewater as electron acceptor adjusted water. 2. A method for treating wastewater containing organic sludge, comprising the steps of: mixing raw material wastewater with adjusted water for an electron acceptor; and aerating the solution under conditions where the amount of dissolved oxygen is substantially 1 mg / L or less. A first step of growing, and treating the treated water of the first step with a dissolved oxygen content of substantially 1 mg.
A second step of performing denitrification treatment with fermenting microorganisms by aerating under the conditions of / L or less, and a third step of performing a precipitation separation treatment of the treated water of the second step and a dephosphorization treatment with a phosphorus-absorbing microorganism. The precipitated sludge of the third step has a dissolved oxygen content of substantially 1 m.
a fourth step of aerating under a condition of not more than g / L to digest excess sludge with sludge digestive microorganisms and to generate electron acceptor conditioned water to be supplied to the first step. 3. The wastewater treatment method according to claim 1, wherein the electron acceptor conditioned water is an inorganic solution containing nitrate and sulfur compounds generated by the treatment with microorganisms. 4. The wastewater treatment method according to claim 3, wherein the electron acceptor conditioning water contains a phosphate. 5. The method according to claim 1, wherein the adjusted water of the electron acceptor produced in the fourth step is collected in a storage tank, and then a required amount of the adjusted water of the electron acceptor is mixed from the storage tank into the first step. The wastewater treatment method according to claim 2, wherein 6. An apparatus for treating wastewater containing organic sludge, comprising: storing wastewater raw water; mixing water containing microorganism electron acceptors; and reducing the amount of dissolved oxygen to substantially 1 mg / L or less. An aeration tank, a sedimentation tank for precipitating the treated water of the first aeration tank, and a sedimentation sludge of the sedimentation tank having a dissolved oxygen content of substantially 1 mg.
A wastewater treatment apparatus comprising: a second aeration tank for aerating under the condition of / L or less; and means for returning the supernatant water generated in the second aeration tank to the first aeration tank as electron acceptor adjusted water. 7. An apparatus for treating wastewater containing organic sludge, comprising: an inflow tank for storing wastewater raw water and aerating the wastewater raw water under a condition in which the amount of dissolved oxygen is substantially 1 mg / L or less; Water has a dissolved oxygen content of substantially 1 mg / L
A reaction tank for aeration and denitrification treatment under the following conditions; a precipitation tank for precipitating treated water in the reaction tank; and a settling tank in the precipitation tank having a dissolved oxygen content of substantially 1 mg.
A sludge digestion tank that is aerated under the conditions of / L or less, and the supernatant water generated in the sludge digestion tank is stored as electron acceptor adjusted water, and a predetermined amount of electron acceptor adjusted water is mixed into the inflow tank. A wastewater treatment device equipped with an electron acceptor conditioned water storage tank. 8. The wastewater treatment apparatus according to claim 7, wherein the electron acceptor conditioned water storage tank is provided in front of the inflow tank. 9. The wastewater treatment apparatus according to claim 7, wherein the storage tank for adjusting the electron acceptor water is provided on the rear side of the sludge digestion tank.