JP2001038370A - Waste water treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove phosphorus in sludge generating by treatment by sewerage, to reduce the burden of a waste water treatment equipment, and to prevent inflow of phosphorus into a secondary treatment water. SOLUTION: This device is provided with a solid liquid separation tank 10 for settling and separating solids in phosphorus-containing sludge, and a dephosphorizing tank 20 in which a dephosphorizing agent and calcium ions are added to the separation liquid from which the solids separated in the solid liquid separation tank 10 and phosphorus in the separation liquid is allowed to react with the added calcium to deposit solids and then phosphorus is removed from the separation liquid.

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 biological dephosphorization method for removing sludge containing a high concentration of phosphorus and orthophosphate ionic phosphorus contained in anaerobic digested sludge. The present invention relates to a wastewater treatment apparatus for reducing the concentration of phosphorus in sludge return water and performing wastewater treatment by a biological phosphorus removal method in a stable state.

[0002]

2. Description of the Related Art Sludge generated by the treatment of sewage contains a large amount of organic substances, and if left untreated, causes a problem such as decay and gives off a bad smell. There is a need.

[0003] Anaerobic digestion of sludge decomposes organic substances in sludge by the action of anaerobic microorganisms to generate methane gas, and is significant from the viewpoint of energy recovery by recovering methane. is there. However, the sludge after treatment, that is, digested sludge, contains ammonia nitrogen,
Orthrin is contained in a high concentration, which cannot be sufficiently removed at the return destination, and there is a concern about release into secondary treatment water.

[0004] On the other hand, digested sludge reacts with magnesium ions in the sludge to form scale of magnesium ammonium phosphate hexahydrate on the wall surface of the digested sludge tube, causing blockage of the digested sludge tube. This also progresses in the dewatering device, and for example, hastening the progress of clogging of the filter cloth of the belt press and generating scale on the inner wall surface of the ball of the centrifugal dewatering machine, thus causing a serious problem in maintenance.

In aerobic digestion, sludge is kept in an aerobic state by aeration or mechanical stirring aeration, and organic matter is oxidized and decomposed to stabilize the sludge. This method has drawbacks such as high operating costs due to the need for oxygen supply.Although there are few examples in Japan so far, the driving operation is easy and there are few bad smells. The potential remains widespread for small-scale sewage treatment. However, also in this method, high concentration of orthrin is contained in the digested sludge dewatered filtrate, and this is returned to the water treatment system, so that the load increases, which is one of the causes of deterioration of the secondary treatment water quality. Become.

[0006] Further, phosphorus removed from raw water by the biological phosphorus removal method accumulates in sludge at a high concentration and is re-released to the water side under anaerobic conditions, which adversely affects water treatment. Is concerned. Therefore, there is a need for a method for efficiently removing re-released phosphorus.

[0007]

The conventional removal of phosphorus is as follows.
The coagulation sedimentation method of coagulating phosphorus in sewage using a coagulant composed of a metal salt such as ferric salt or aluminum sulfate (salt) and lime, and precipitating and removing this is most commonly performed. However, this method has a problem that the amount of generated sludge is large, and they are difficult to dehydrate.

Therefore, the present invention can efficiently remove phosphorus in sludge generated by sewage treatment, reduce the load on wastewater treatment equipment, and prevent phosphorus from flowing into secondary treated water. It aims at providing a wastewater treatment device.

[0009]

In order to achieve the above object, a wastewater treatment apparatus according to the present invention comprises a solid-liquid separation tank for separating and separating solids in phosphorus-containing sludge, and a solid-liquid separation tank for separating solids in the solid-liquid separation tank. A dephosphorization tank that removes phosphorus from the separated liquid by adding a dephosphorizing agent and calcium ions to the separated liquid and reacting and depositing phosphorus in the separated liquid with the added calcium; And a path for mixing the solid separated in the solid-liquid separation tank with the dephosphorized solution from which phosphorus has been removed in the dephosphorization tank and sending it to a sludge concentration facility. .

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view showing one embodiment of a waste water treatment apparatus according to the present invention. The wastewater treatment apparatus includes a solid-liquid separation tank 10 that precipitates and separates solids in phosphorus-containing sludge,
Dephosphorization tank 20 for reacting and removing phosphorus and calcium
And a calcium compound storage tank 30 and a pH adjusting agent storage tank 31. The solid-liquid separation tank 10 has an inflow pipe 11 for phosphorus-containing sludge drawn from a digestion tank or the like of a wastewater treatment facility, and a solid-liquid separation tank 10. A separation liquid supply pipe 12 for supplying the separated upper layer separation liquid to the dephosphorization tank 20 and a solid substance extraction pipe 13 for extracting solid substances settled at the bottom of the tank are provided.

The dephosphorization tank 20 is a bottomed cylinder having a large diameter at the top and a funnel-shaped bottom, and two large and small diameter cylinders 21 and 22 are provided therein. Have been. The outlet of the separated liquid supply pipe 12 is located above the inner peripheral part of the large-diameter cylindrical body 21, and further, a calcium compound supply pipe 23, a pH adjusting agent supply pipe 24, and a dephosphorizing agent supply pipe 25 are provided. Each is provided. Further, a stirrer 26 for generating a downward flow in the cylindrical body 22 is provided inside the small-diameter cylindrical body 22.

Further, on the bottom of the dephosphorization tank 20, phosphorus and calcium react with each other to precipitate phosphorus on the surface of the dephosphorizing agent.
A product discharge portion 27 for discharging crystals of a calcium compound (calcium phosphate, calcium hydrogen phosphate, hydroxyapatite, etc.) is provided, and a dephosphorization solution discharge portion 28 is provided on the upper portion. Further, a pH meter 29 is provided at an appropriate position of the dephosphorization tank 20, and a pH adjuster is supplied from the pH adjuster supply pipe 24 in accordance with a measured value of the pH meter 29.

The large-diameter cylindrical body 21 is provided in the large-diameter portion above the dephosphorization tank, and the upper end is installed so as to be located above the water surface. The small-diameter cylindrical body 22 installed inside the large-diameter cylindrical body 21 has a draft tube-type stirring section between the inner peripheral part of the large-diameter cylindrical body 21 and the lower inner peripheral part of the dephosphorization tank 20. Then, a downward flow is formed on the inner periphery of the small-diameter cylindrical body 22 by the stirrer 26, and an upward flow is formed on the outer periphery, thereby forming a circulating flow.

A separation liquid inflow pipe 1 is provided between the outer peripheral portion of the large-diameter cylindrical body 21 and the inner peripheral portion of the large-diameter portion above the dephosphorization tank 20.
The liquid substantially corresponding to the amount of the separated liquid flowing in from 2 rises, and acts as a crystal separation section for sedimenting and separating the crystals generated by the reaction in the rising process. This portion is formed with a sufficient water area to surely settle even small crystals.

In the dephosphorization tank 20, the separation liquid flowing from the separation liquid inflow pipe 12 and the calcium compound supplied from the calcium compound supply pipe 23 are mixed in the process of circulating around the small-diameter cylindrical body 22, and are separated. The phosphorus contained therein reacts with the added calcium to produce a phosphorus / calcium compound, which is initially deposited on the surface of a phosphorus phosphate or other dephosphorizing agent such as calcium phosphate crystals or phosphate rock previously introduced as seed crystals. Further, the reaction proceeds on this surface, and the crystal grows gradually. When the crystal becomes a certain size, the crystal separates from the circulating flow due to a difference in specific gravity and settles at the bottom of the tank.

At this time, the solid matter in the inflow sludge is sufficiently settled and separated in advance in the solid-liquid separation tank 10 in the former stage, so that the high purity and fertilizer can be obtained from the product discharge part 27 at the bottom of the dephosphorization tank 20. Phosphorus / calcium compounds that can be effectively used as a sulphate can be obtained.

The dephosphorized solution from which phosphorus has been removed is withdrawn from the dephosphorized solution discharge section 28 at the top of the tank, returned to an appropriate position in the wastewater treatment facility, and reprocessed. Further, the solid-liquid separation tank 1
The solid extracted from the solid extraction pipe 13 is sent to a sludge concentration facility or the like, where a predetermined process is performed.

By thus removing phosphorus, it is possible to prevent a large amount of phosphorus from being accumulated in sludge,
It is possible to prevent phosphorus from flowing out into the secondary treatment water, to prevent scale from adhering to the piping, to reduce the amount of sludge, and to reduce the load on the wastewater treatment equipment.

FIG. 2 is an explanatory view showing another embodiment of the present invention. Since the device configuration of the present embodiment is substantially the same as that of the above-described embodiment, the same components as those of the above-described embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, the solid-liquid separation in the solid-liquid separation tank 10 is limited only to separation of a substance having a large specific gravity, such as sand, and most of the sludge is directly supplied to the dephosphorization tank 20 for dephosphorization. The solid matter withdrawn from the solid matter extraction pipe 13 of the solid-liquid separation tank 10 and the sludge-containing dephosphorization liquid withdrawn from the dephosphorization liquid discharge unit 28 of the dephosphorization tank 20 merge into the merge path 41. Then, it is sent to the sludge concentration equipment 42.

At this time, in the dephosphorization tank 20, the sludge supplied from the solid-liquid separation tank 10 is prevented from settling at the bottom of the tank together with the crystals, and the dephosphorization solution discharge section 2 is used together with the dephosphorization water.
8 and sedimentation without causing the crystal to flow out, the sedimentation velocity V1 of the crystal, the cross-sectional flow velocity V2 of the ascending flow in the crystal separation part on the outer periphery of the large-diameter cylindrical body 21, and the solid-liquid separation tank 10 The relationship between the sectional flow velocity V3 of the upward flow and V1
>V2> V3.

As described above, in the case of the wastewater treatment equipment provided with the sludge concentration equipment 42, only those having a large specific gravity in the solid-liquid separation tank 10 that precipitate together with the crystals generated in the dephosphorization tank 20. By setting so as to separate the wastewater, the capacity of the solid-liquid separation tank 10 can be significantly reduced as compared with the embodiment described above, so that the size of the apparatus can be reduced and the digestion tank and sludge in the existing wastewater treatment equipment can be reduced. It can be easily installed even in a limited space between the concentration equipment 42.

[0023]

As described above, according to the wastewater treatment apparatus of the present invention, phosphorus contained in digested sludge and the like can be efficiently removed, so that it is ensured that phosphorus flows out into the secondary treated water. And the load on the water treatment equipment can be reduced, and a stable water treatment operation can be performed.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of a wastewater treatment apparatus according to the present invention.

FIG. 2 is an explanatory view showing another embodiment of the wastewater treatment device of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Solid-liquid separation tank, 11 ... Inflow pipe, 12 ... Separation liquid supply pipe, 13 ... Solid substance extraction pipe, 20 ... Dephosphorization tank, 21 ... Large diameter cylinder, 22 ... Small diameter cylinder, 23 ... Calcium compound supply Pipe, 24: pH adjuster supply pipe, 25: dephosphorizer supply pipe, 26: stirrer, 27: product discharge section, 28: dephosphorization liquid discharge section, 29: pH meter, 30: calcium compound storage tank, 31: pH adjusting agent storage tank, 41: Merging path, 42:
Sludge thickening equipment

Claims (2)

[Claims] 1. A solid-liquid separation tank for precipitating and separating solids in a phosphorus-containing sludge, and a dephosphorizing agent and calcium ions are added to the separated liquid from which solids are separated in the solid-liquid separation tank, and A wastewater treatment apparatus comprising: a phosphorus removal tank that removes phosphorus from a separated solution by reacting phosphorus and added calcium to cause precipitation. 2. A path for mixing a solid separated in the solid-liquid separation tank with a dephosphorized solution from which phosphorus has been removed in the dephosphorization tank and sending the mixture to a sludge concentration facility. Item 2. A wastewater treatment device according to Item 1.