JP2000296399A - Waste water treating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste water treating apparatus capable of efficiently removing the phosphorus contained in inflow water and surely preventing the leakage of the phosphorus into secondarily treated water even if the phosphorus load is high. SOLUTION: The rear stage of an anaerobic vessel 16 of waste water treatment equipment adopting a biological dephosphorization method is provided with a solid-liquid separating means 21 for executing the solid-liquid separation of the activated sludge C withdrawn from the inside of the anaerobic vessel and a dephosphorizing means 22 for removing the ammonia and phosphorus in the separated water in the form of ammonium magnesium phosphate hexahydrate by adding a magnesium compound E to the separated water D of the solid-liquid separating means 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater treatment apparatus, and more particularly, to a method for removing phosphorus efficiently in a wastewater treatment facility employing a biological dephosphorization method and a method for removing phosphorus from useful magnesium ammonium phosphate. The present invention relates to a wastewater treatment device for recovering as a hydrate.

[0002]

2. Description of the Related Art In recent years,
As shown in the system diagram of FIG. 3, the sand basin 11, the dust remover 12,
An anaerobic tank 16, a denitrification tank 17, and an aerobic tank 18 are connected from the inflow side as a treatment tank 14 of the standard activated sludge method formed by the first sedimentation tank 13, the treatment tank 14, and the final sedimentation tank 15,
By circulating the returned sludge A from the final sedimentation tank 15 to the anaerobic tank 16 and circulating the nitrification liquid B from the latter stage of the aerobic tank 18 to the denitrification tank 17, not only the removal of BOD etc. but also the removal of phosphorus and nitrogen. Wastewater treatment equipment is adopted.

[0003] Phosphorus is removed by a biological dephosphorization method using bacteria that accumulate polyphosphoric acid in the body in an anaerobic-aerobic state. In this method, the sludge is concentrated during the step of condensing excess sludge and storing sludge. Phosphate ions (orthophosphate ions) are released from the reactor, and high-concentration phosphorus is eluted in the return water from these, and this is returned to the water treatment system. The phosphorus removal rate was not always good.

Further, when the phosphorus load in the inflow water is high,
The content of phosphorus in the returned sludge is as high as 4 to 6%, so that phosphorus is easily released. Some of these may release phosphorus in the final sedimentation basin, so there is a risk that phosphorus will leak into the secondary treated water.

Accordingly, the present invention provides a wastewater treatment apparatus capable of efficiently removing phosphorus contained in influent water and preventing leakage of phosphorus into secondary treated water even when the phosphorus load is high. It is intended to be.

[0006]

In order to achieve the above object, the wastewater treatment apparatus of the present invention is drawn out of the anaerobic tank after the anaerobic tank in a wastewater treatment facility employing a biological dephosphorization method. A solid-liquid separation means for performing a solid-liquid separation of the activated sludge is provided, and a magnesium compound is added to the separated water of the solid-liquid separation means to remove ammonia and phosphorus in the separated water as magnesium ammonium phosphate hexahydrate. It is characterized in that phosphorus means is provided.

[0007]

FIG. 1 is a system diagram showing one embodiment of a wastewater treatment apparatus according to the present invention. This wastewater treatment apparatus includes a sand basin 11, a dust remover 12, and a
3, a treatment tank 14 in which an anaerobic tank 16, a denitrification tank 17 and an aerobic tank 18 are connected, and a final sedimentation tank 15,
A solid-liquid separation means 21 for performing solid-liquid separation of the activated sludge C drawn from the latter stage of the anaerobic tank 16, and a magnesium compound E and a pH adjuster F added to separation water D of the solid-liquid separation means 21 to separate the water. Dephosphorization means 2 for removing ammonia and phosphorus as magnesium ammonium phosphate hexahydrate
2 is provided.

The solid-liquid separation means 21 is provided to prevent the flow of solids into the dephosphorization means 22 and to efficiently perform the dephosphorization operation, and separates the solid content of the activated sludge C. Separation water D containing ammonia and phosphate is obtained, and for example, a generally used gravity precipitation method can be used, and a membrane separation method can also be used.

The dephosphorization means 22 is added with ammonium ions contained in the effluent of the first settling basin flowing into the anaerobic tank 16 from the first settling basin 13, phosphate ions released from the activated sludge C, and a required amount. and magnesium ions of the magnesium compound E, magnesium ammonium phosphate hexahydrate crystalline state by reacting with a predetermined pH (MAP: Stora _byte: MgNH 4 _PO 4 · 6H
_{2 O)} to generate, in which it is separated and recovered.

The sludge (phosphorus release sludge) G separated by the solid-liquid separation means 21 and the dephosphorized water H from which phosphorus and the like have been removed by the dephosphorization means 22 are returned to predetermined positions in the anaerobic tank 16.

Hereinafter, description will be made based on the processing procedure. First, the influent water J flows into the treatment tank 14 after the sediment K in the sand basin 11, the bulk L in the dust remover 12, and the initial sediment M in the first sedimentation basin 13. Processing tank 14
The first settling basin effluent N that has flowed into the anaerobic tank 16 is mixed with the returned sludge A in the preceding stage of the anaerobic tank 16, and in the latter stage, a part of the activated sludge C is drawn out to the solid-liquid separation means 21, and the phosphorus-releasing sludge is removed. After mixing with G and dephosphorized water H, it flows into the denitrification tank 17. Further, after mixing with the nitrification liquid B in the denitrification tank 17, the mixture flows into the aerobic tank 18.

By passing through each of these tanks, phosphorus is taken into the body of bacteria accumulating polyphosphate and removed from the influent water, and nitrogen in the influent water is also removed by the nitrification and denitrification action. A predetermined purification treatment is performed in the treatment tank 14, and the treated water P from which the sludge has been separated in the final sedimentation basin 15 is discharged to a river or the like after sterilization. A part of the sludge Q extracted from the final sedimentation basin 15 is returned to the anaerobic tank 16 as returned sludge A.
And the remaining part is treated as surplus sludge R.

The activated sludge C extracted from the latter stage of the anaerobic tank 16 contains a large amount of phosphorus taken in as polyphosphoric acid from the influent water. Releases phosphorus when exposed to the environment. Therefore, the activated sludge C is subjected to solid-liquid separation by the solid-liquid separation means 21 so that the separated water D containing phosphorus is removed.
And the sludge releasing phosphorus (phosphorus releasing sludge G) are separated. As a result, the separated water D is discharged from the first sedimentation basin effluent N
It becomes a state containing ammonium ions contained therein and phosphate ions released from the activated sludge C.

In the dephosphorization means 22 into which the separated water D containing ammonium ions and phosphate ions has flowed, the aforementioned MA
Magnesium ions, which are insufficient for the P production reaction, are added, and a pH adjuster is added to adjust the pH to a predetermined value, thereby generating MAP. The precipitated MAP is recovered from the dephosphorization means 22 as the recovered material S. Taken out. The collected MAP can be used, for example, as a slow-release fertilizer. Further, by mixing a potassium salt and subjecting the mixture to granulation or the like, it can be effectively recycled as a fertilizer containing three major nutrients of a plant. Can be.

The dephosphorized water H from which ammonium ions and phosphate ions have been removed by the MAP generation reaction is returned to the latter stage of the anaerobic tank 16 and reprocessed as described above. Further, the phosphorus-releasing sludge G that has released phosphorus by the solid-liquid separation means 21 is also returned to the subsequent stage of the anaerobic tank 16.

As described above, by removing the activated sludge having accumulated phosphorus from the anaerobic tank 16 and performing a dephosphorization treatment,
Because the amount of polyphosphate accumulated in microorganisms can be reduced, stable biological dephosphorization operation can be performed, and even when the phosphorus load in the influent is high, it is ensured that phosphorus leaks into the secondary treated water. Can be prevented.

Further, since ammonium ions required for the MAP generation reaction are obtained from the ammonia nitrogen contained in the inflow water such as sewage, it is not necessary to add ammonium ions separately, so that phosphorus ions can be eliminated. The cost (chemical cost) required for removal can be reduced.

Furthermore, since the conventional wastewater treatment equipment shown in FIG. 3 can be implemented simply by providing the solid-liquid separation means 21 and the dephosphorization means 22 and these additional equipment and piping, the existing wastewater treatment equipment can be used. Can also be easily handled.

FIG. 2 is a system diagram showing another embodiment of the wastewater treatment apparatus of the present invention. This wastewater treatment apparatus is the same as the apparatus shown in FIG.
Is recycled to the upstream of the anaerobic tank 16 as returned sludge A, and a part of the phosphorus-releasing sludge G from which phosphorus has been released by the solid-liquid separation means 21 is extracted as surplus sludge T. .

As described above, by sending a part of the phosphorus-releasing sludge G having a low phosphorus content to the sludge treatment destination as surplus sludge T, the phosphorus treatment at the sludge treatment destination becomes unnecessary, and the burden on the sludge treatment destination is eliminated. Can be reduced.

The position for extracting the activated sludge C to the solid-liquid separation means 21 can be set to any position as long as the activated sludge having sufficiently accumulated phosphorus can be extracted.
The position for returning the phosphorus release sludge G and the dephosphorized water H is also arbitrary,
Depending on the state of the phosphorus-releasing sludge G or the dephosphorized water H, it can be treated as surplus sludge or discharged as treated water.

[0022]

As described above, according to the wastewater treatment apparatus of the present invention, a stable biological dephosphorization operation can be performed, and even when the phosphorus load in the influent water is high, phosphorus is contained in the secondary treated water. Leakage can be reliably prevented.
Moreover, the recovered phosphorus can be used as a fertilizer as it is, and the cost of chemicals required for the reaction for removing phosphorus can be minimized.

[Brief description of the drawings]

FIG. 1 is a system diagram showing one embodiment of a wastewater treatment device of the present invention.

FIG. 2 is a system diagram showing another embodiment of the wastewater treatment device of the present invention.

FIG. 3 is a system diagram showing an example of a wastewater treatment facility using a biological phosphorus removal method.

[Explanation of symbols]

11: sand basin, 12: dust remover, 13: first sedimentation basin, 14
... treatment tank, 15 ... final sedimentation tank, 16 ... anaerobic tank, 17 ... denitrification tank, 18 ... aerobic tank, 21 ... solid-liquid separation means, 22 ... phosphorus removal means

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Minoru Mamoru 1-3-3 Kyobashi, Chuo-ku, Tokyo Inside Maezawa Industrial Co., Ltd. (72) Inventor Tatsuhiko Suzuki 1-3-3 Kyobashi, Chuo-ku, Tokyo Maezawa Kogyo Co., Ltd. (72) Inventor Masaaki Yoshino 1-3-3 Kyobashi, Chuo-ku, Tokyo F Maezawa Kogyo Co., Ltd. F-term (reference) 4D038 AA08 AB28 AB43 BB17 BB19 4D040 BB72

Claims (1)

[Claims] Claims: 1. A solid-liquid separating means for performing solid-liquid separation of activated sludge drawn out of an anaerobic tank is provided downstream of an anaerobic tank in a wastewater treatment facility employing a biological dephosphorization method. A wastewater treatment apparatus comprising a phosphorus removing means for adding a magnesium compound to the separated water of the separating means to remove ammonia and phosphorus in the separated water as magnesium ammonium phosphate hexahydrate.