JP2002361277A - Treating method and treating apparatus for organic contaminated water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biological treating method for organic waste water which enables a high degree phosphor removal, does not cause the deterioration of COD of the treated water, recovers phosphor resources and greatly reduces the amount of generation of excessive sludge. SOLUTION: In the biological treating method of organic contaminated water and an apparatus therefor, the organic contaminated water is subjected to the biological treatment by using an iron or aluminium hydroxide or oxide-coexisting activated sludge and, at the same time, a part of the metallic hydroxide-containing activated sludge of the biological treatment process is extracted, is subjected to sludge solubilizing treatment, and is thereafter returned to the biological treatment process. Therein, at the same time, the other part of metallic hydroxide containing sludge in the biological treatment process is subjected to alkali treatment by the addition of a caustic alkali and, thereafter, is separated into separated sludge and separated liquid in a solid-liquid separation process, the separated sludge is returned to the biological treatment process, the separated liquid of the solid-liquid separation process is guided to a chemical phosphor deposition process under alkaline conditions and phosphor is deposited and separated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology for highly purifying phosphorus-containing organic sewage such as sewage.
The present invention relates to a novel organic sewage treatment technology capable of highly removing COD, recovering phosphorus as a resource, and significantly reducing the amount of excess biological sludge generated.

[0002]

2. Description of the Related Art The most typical technique for removing phosphorus from organic wastewater such as sewage is a biological phosphorus removal method. In this technology, organic sewage is supplied to an anaerobic tank to discharge phosphorus from activated sludge (in which dephosphorylated bacteria coexist) in returned sludge, and then supplied to an aerobic tank to remove phosphorus from dephosphorized bacteria. After ingestion, the activated sludge is precipitated and separated, and the precipitated sludge is recycled to the anaerobic tank.

However, the above-mentioned conventional biological dephosphorization method has the following disadvantages. (1) The phosphorus concentration in the treated water cannot be reduced to 0.5 mg / liter or less, and the phosphorus removing effect is insufficient. (2) When the BOD / P ratio of the raw water decreases, the discharge of phosphorus from the dephosphorylated bacteria in the anaerobic tank becomes insufficient, and as a result, the intake of phosphorus to the dephosphorylated bacteria in the aerobic tank also worsens. (3) Since phosphorus is not removed except in the form of being taken up by biological sludge, the material balance of phosphorus cannot be established unless the sludge containing phosphorus is discharged out of the system. In many cases, sludge treatment becomes a burden. That is, it is difficult in principle to reduce the amount of excess sludge generated.

[0004] As a conventional method for reducing the amount of excess sludge generated, a part of the activated sludge (an amount larger than the amount of excess sludge generated) is extracted from the activated sludge treatment system of sewage, subjected to ozone oxidation treatment, and then to sewage treatment. An “aerobic treatment method for organic wastewater” is known, in which a system is supplied to a system aeration tank to biodegrade solubilized sludge to reduce the amount of excess sludge generated. However, when this technology is applied, surplus sludge is not generated, so there is a serious drawback that the phosphorus removal rate of activated sludge treatment of wastewater becomes zero in principle, and the advanced removal of phosphorus is now strongly desired. Go against the demands of the times. Moreover, in this conventional technique, in the solubilization treatment step and the process of biologically decomposing the solubilized sludge, hardly biodegradable COD is inevitably generated, and the COD of the treated water is deteriorated.
There was a major drawback that the degree of OD deterioration increased as the amount of surplus sludge decreased.

As a method of removing phosphorus in the activated sludge treatment step, a technique called an activated sludge method with a flocculant has been put into practical use. However, this technique cannot remove phosphorus unless the flocculant is constantly added. However, there is a major drawback in that extremely hard-to-dehydrate metal hydroxide sludge is generated in large quantities, making sludge treatment and disposal difficult.

[0006]

SUMMARY OF THE INVENTION The present invention has established a new technology which has solved the drawbacks of the conventional technology for reducing excess sludge by solubilizing sludge such as ozone and ultrasonic waves. It is an object of the present invention to provide a new system capable of recovering a phosphorus resource without deteriorating COD and reducing the amount of generated excess sludge.

[0007]

The present invention has solved the above-mentioned problems by the following means. (1) Organic sludge is biologically treated with activated sludge coexisting with iron or aluminum hydroxide or oxide, and a part of the activated sludge containing metal hydroxide in the biological treatment step is withdrawn to perform a solubilization treatment. After returning to the biological treatment step, the caustic alkali is added to another part of the metal hydroxide-containing sludge in the biological treatment step, alkali treatment is performed, and the separated sludge and the separated liquid are separated in the solid-liquid separation step. Separating, returning the separated sludge to the biological treatment step, guiding the separated liquid of the solid-liquid separation step to a chemical phosphorus precipitation step under alkaline conditions, and separating and separating phosphorus by organic wastewater. Processing method. (2) Biological treatment of organic sewage with activated sludge coexisting with iron or aluminum hydroxide or oxide, and a part of the activated sludge containing metal hydroxide in the biological treatment step is subjected to sludge solubilization treatment. After returning to the biological treatment step, the caustic alkali is added to another part of the metal hydroxide-containing sludge in the biological treatment step, and alkali treatment is performed. And returning the sludge from which phosphorus has been removed to the biological treatment step. (3) A method for treating organic sewage, comprising returning the alkaline separated liquid flowing out of the solid-liquid separation step after the chemical phosphorus precipitation step in (1) to the sludge solubilization step or the alkali treatment step. .

(4) An aeration tank for purifying organic sewage by a biological treatment method using activated sludge coexisting with iron or aluminum hydroxide or oxide, and a sedimentation tank for sedimenting and collecting microorganisms at the latter stage of the aeration tank as sludge. Having a return system for directly supplying a part of the sludge extracted from the sedimentation tank as return sludge to the aeration tank, introducing another part of the extracted sludge into the sludge solubilization treatment tank, After sludge solubilization treatment,
A return system for supplying this to the aeration tank, another part of the extracted sludge is introduced into an alkali treatment tank, treated with caustic alkali, and then subjected to solid-liquid separation by a solid-liquid separation device to obtain the obtained separation. A return system for supplying sludge to the aeration tank, a system for sending a phosphate ion-containing separated solution separated by the solid-liquid separator to a phosphorus recovery device, and recovering a precipitate formed by addition of Ca ions or Mg ions; and An apparatus for treating organic sewage, comprising a return system for returning a separated liquid from a recovery apparatus to the alkaline treatment tank.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of the present invention. That is, an organic sewage (hereinafter also referred to as “raw water”) 1 is supplied for simplicity, and an inorganic coagulant 3 selected from iron or aluminum hydroxide or oxide is added in the tank, whereby inorganic water is added. An aeration tank 2 that purifies by a biological treatment method using activated sludge coexisting with a flocculant, and a sedimentation tank 5 that is a microbial solid-liquid separation step at the subsequent stage of the aeration tank 2 are incorporated, and organic wastewater that discharges treated water 6 outside the system In the treatment apparatus, a pipe for returning a part of the settled sludge 7 extracted from the settling tank 5 directly to the aeration tank 2 as return sludge 8 and another part 9 of the settled sludge are introduced into the solubilization treatment tank 11. A pipe, a pipe for introducing and supplying the solubilized sludge 12 after the solubilization treatment into the return pipe for returning the returned sludge 8 to the aeration tank 2, and another part 10 of the settled sludge 7 to the alkali treatment tank 13. Piping to be introduced, then Al Li sludge 14
And a supply pipe for introducing the separated sludge 17 into the solubilized sludge return pipe in the solid-liquid separation device 15, a supply pipe for introducing the phosphate ion-containing liquid 16 to the phosphorus recovery device 18, and calcium phosphate or phosphoric acid in the phosphorus recovery device 18. A discharge pipe for recovering magnesium ammonium as recovered phosphorus 19 and a conduit for introducing and supplying the strongly alkaline separated liquid 20 from the phosphorus recovery apparatus 18 into the pipe for introducing a part 10 of the settled sludge into the alkali treatment tank 13 are provided. Thereby, the flow and the reaction of the respective substances described above are configured to occur.

The activated sludge treatment shown in FIG. 1 (normal activated sludge method,
Any biological treatment such as a biological nitrification denitrification method, a biological dephosphorization method, and a carrier addition method may be applied).
C, an inorganic coagulant such as ferric chloride or iron sulfate is added, and a metal hydroxide is made to coexist with the activated sludge, and a biological treatment is performed while coagulating or adsorbing and removing phosphorus and COD. The addition of the inorganic coagulant may be performed only at the beginning of operation. Instead of generating a hydroxide in the biological treatment tank by adding an inorganic flocculant, phosphorus-adsorbing iron oxide and aluminum oxide fine particles are added to the biological treatment step at a rate of about 1000 to 5000 mg / liter before starting the operation. You can keep it.

Thereafter, the activated sludge coexisting with metal hydroxide in the biological treatment step is solid-liquid separated by solid-liquid separation means such as sedimentation, membrane separation, and dynamic filtration. Obtain treated water 6 and separated sludge. Since the sedimentation tank 5 is used in FIG. 1, the separated sludge is the sedimentation sludge 7. Most of the separated sludge is returned to the biological treatment tank as return sludge 8.

The remaining part 9 of the separated sludge is ozone oxidized,
It is led to a solubilization tank 11 to which a means for solubilizing sludge such as ultrasonic treatment, mill grinding, heat treatment, and high-temperature aerobic microorganisms is applied, and activated sludge in the activated sludge coexisting with iron hydroxide or aluminum hydroxide is removed. It is solubilized and the biodegradability of the activated sludge is significantly improved.

When ozone is applied to the solubilizing means,
The hardly biodegradable COD component to which iron hydroxide and aluminum hydroxide flocs are adsorbed is also degraded by ozone oxidation to improve biodegradability, and is biologically removed in the biological treatment tank. When the solubilized sludge is returned to the activated sludge treatment step (aeration tank), microorganisms and C
Since the biodegradability of OD is improved, the amount of surplus activated sludge generated by biodegradation is reduced, and the ability of iron hydroxide and aluminum hydroxide floc to remove COD is restored.

On the other hand, when a caustic alkali such as NaOH is added to the other portion 10 of the activated sludge coexisting with metal hydroxide, and the pH of the sludge is increased to 11.5 or more, the sludge is adsorbed on iron hydroxide and aluminum hydroxide. The phosphate ions that have been exchanged with hydroxide ions elute to the liquid side. At this time, the activated sludge is simultaneously solubilized by hydrolysis with alkali, and biodegradability is improved. Next, alkali-treated sludge 1
4 is subjected to solid-liquid separation. Separated sludge 1 obtained by solid-liquid separator 15
7 is returned to the aeration tank 2 and undergoes biodegradation and decreases.
Further, since the metal hydroxide from which phosphorus has been eluted has recovered its phosphorus adsorption ability, it can adsorb and remove phosphorus in raw water.

Next, Ca ions or Mg ions are added to the solution from which phosphorus has been eluted to precipitate calcium phosphate or magnesium ammonium phosphate, and the precipitate is recovered. Strongly alkaline separation liquid 20 from phosphorus recovery device 18
Is strongly alkaline, having a pH of about 12, and is recycled to the alkali treatment tank 13 so that the amount of NaOH added can be reduced. It is preferable to add the strong alkaline separation liquid 20 from the phosphorus recovery device 18 to the sludge solubilization tank 11 by ozone, ultrasonic irradiation, or the like, because the alkali solubilization effect is added and the sludge solubilization effect is improved.

The alkali-treated sludge 14 is supplied to a calcium phosphate / magnesium ammonium phosphate crystallization tank (not shown) without solid-liquid separation, and the sedimentation rate of the generated calcium phosphate / magnesium ammonium phosphate crystals is reduced by biological The biological sludge may be supplied to the biological treatment tank after classification using the fact that the sludge is much larger than that of the sludge.

According to the above-mentioned process of the present invention, phosphorus, COD, BOD, SS and the like of raw water are permanently removed, and the generation of excess activated sludge is almost eliminated. Phosphorus can also recover resources in a form that can be easily used as fertilizer.

[0018]

The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 A verification test of the present invention was performed on sewage (average water quality is shown in Table 1) according to the process shown in FIG. Table 2 shows the test conditions.

[0020]

[Table 1]

[0021]

[Table 2]

As a result of the experiment, the average of the quality of the treated water from the sedimentation tank after two months from the start of the treatment and after the treatment state became stable was as shown in Table 3 in which phosphorus and BOD were highly removed. It had been. The amount of excess sludge withdrawn per year is 12
MLVS of activated sludge aeration tank
S was maintained at 3500 to 4000 mg / liter or less. From this result, it was found that the amount of surplus activated sludge generated was negligibly small.

[0023]

[Table 3]

[0024]

According to the present invention, the following (1) to (4)
The effect of is obtained. (1) Combining activated sludge solubilization by ozone, desorption of phosphate ions from metal hydroxide by alkali treatment, and hydrolysis of activated sludge by alkali treatment based on a new concept, resulting in surplus activated sludge. Generation is almost negligible, and phosphorus, COD
Removal is stable and phosphorus resources can be recovered. (2) As a result, it is possible to fundamentally solve the serious drawbacks that the conventional activated sludge method of reducing the amount of generated excess sludge cannot remove phosphorus and the COD of treated water deteriorates. (3) Since the alkali agent used in the alkali treatment can be reused, the required amount of caustic is reduced. (4) The above effects can be obtained by utilizing the secondary processing equipment without providing the tertiary processing equipment, so that the equipment cost and the installation area can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the method for treating organic wastewater of the present invention.

[Explanation of symbols]

 Reference Signs List 1 organic wastewater (raw water) 2 aeration tank (biological treatment tank) 3 inorganic coagulant 4 coagulation activated sludge mixed liquid 5 sedimentation tank 6 treated water 7 settled sludge 8 returned sludge 9 part of settled sludge 10 other settled sludge Part 11 Solubilization tank 12 Solubilized sludge 13 Alkaline treatment tank 14 Alkaline treated sludge 15 Solid-liquid separator 16 Phosphate ion-containing liquid 17 Separated sludge 18 Phosphorus recovery device 19 Recovered phosphorus 20 Strong alkaline separation liquid

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C02F 11/00 C02F 11/00 J ZAB ZABZ (72) Inventor Kiyomi Arakawa 11th Asahimachi Haneda-cho, Ota-ku, Tokyo No. 1 Inside EBARA CORPORATION (72) Inventor Takuya Kobayashi 11-1 Haneda Asahimachi, Ota-ku, Tokyo F-term in EBARA CORPORATION (Reference) 4D024 AA04 AB12 BA13 BA14 BC04 DA06 DA07 DB03 DB05 DB06 DB10 DB12 DB15 DB20 DB21 DB24 4D028 AA08 AB00 AC01 AC03 BC17 BD11 BD17 4D038 AA08 AB45 AB48 BA04 BB06 BB17 BB18 BB19 4D059 AA05 AA19 BC02 BE49 BF02 BF14 BK11 BK12 BK22 CA21 CA28 DA01 DA43 EB05

Claims (4)

[Claims] 1. An organic wastewater is subjected to biological treatment with activated sludge coexisting with iron or aluminum hydroxide or oxide, and a part of the activated sludge containing metal hydroxide in the biological treatment step is withdrawn to solubilize the sludge. And then return to the biological treatment step, add caustic to another part of the metal hydroxide-containing sludge in the biological treatment step, add alkali treatment, and separate the sludge from the separated sludge in the solid-liquid separation step. Separating the liquid into liquid, returning the separated sludge to the biological treatment step, guiding the separated liquid from the solid-liquid separation step to a chemical phosphorus precipitation step under alkaline conditions, and separating and separating phosphorus. Wastewater treatment method. 2. An organic wastewater is subjected to biological treatment with activated sludge coexisting with iron or aluminum hydroxide or oxide, and a part of the activated sludge containing metal hydroxide in the biological treatment step is withdrawn to solubilize the sludge. After returning to the biological treatment step, the caustic alkali is added to another part of the metal hydroxide-containing sludge in the biological treatment step, and alkali treatment is performed. A method for treating organic wastewater, comprising returning sludge from which phosphorus has been removed by separation to the biological treatment step. 3. The treatment of organic sewage, wherein the alkaline separation liquid flowing out of the solid-liquid separation step after the chemical phosphorus precipitation step according to claim 1 is returned to the sludge solubilization step or the alkali treatment step. Method. 4. An aeration tank for purifying organic sewage by a biological treatment method using activated sludge coexisting with iron or aluminum hydroxide or oxide, and a sedimentation tank for sedimenting and collecting microorganisms at a later stage of the aeration tank as sludge. A return system for directly supplying a part of the sludge extracted from the sedimentation tank to the aeration tank as return sludge; introducing another part of the extracted sludge to a sludge solubilization treatment tank; After solubilization treatment, a return system for supplying this to the aeration tank, another part of the extracted sludge is introduced into an alkali treatment tank, treated with caustic alkali, and then subjected to solid-liquid separation with a solid-liquid separation device. , A return system for supplying the obtained separated sludge to the aeration tank, a phosphate ion-containing separation solution separated by the solid-liquid separation device to a phosphorus recovery device, and recovery of a precipitate formed by addition of Ca ions or Mg ions. System And a return system for returning a separated liquid from the phosphorus recovery device to the alkali treatment tank.