JP4439040B2 - Wastewater treatment equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wastewater treatment apparatus, and more specifically, removes sludge containing a high concentration of phosphorus by a biological dephosphorization method or orthophosphoric acid ion phosphorus contained in anaerobic digested sludge to remove phosphorus in sludge return water. The present invention relates to a wastewater treatment apparatus for reducing the concentration of water and performing wastewater treatment by a biological dephosphorization method in a stable state.
[0002]
[Prior art]
The sludge generated by the sewage treatment contains a lot of organic matter, and if left untreated, it will rot and give off a bad odor, so it must be decomposed and mineralized to stabilize its quality.
[0003]
The anaerobic digestion of sludge decomposes the organic matter in the sludge by the action of anaerobic microorganisms and generates methane gas. The recovery of methane is also significant in terms of energy recovery. However, sludge after treatment, that is, digested sludge contains ammonia nitrogen and ortholine at high concentrations, and these cannot be sufficiently removed at the return destination, so there is a concern of release into the secondary treated water. ing.
[0004]
On the other hand, digested sludge reacts with magnesium ions in the sludge to generate magnesium ammonium phosphate hexahydrate scale on the wall of the digested sludge tube, causing the digested sludge tube to become clogged. This also progresses in the dehydrating apparatus, and for example, the progress of clogging of the filter cloth of the belt press is accelerated, or scale is generated on the inner wall surface of the ball of the centrifugal dehydrator.
[0005]
In the aerobic digestion, the sludge is kept in an aerobic state by aeration or mechanical stirring aeration, and the sludge is stabilized by oxidizing and decomposing organic matter. This method has disadvantages such as high operating costs because it requires oxygen supply, and although there are few examples in Japan so far, it is easy to operate and has few bad odors. There is still the possibility of spreading for small-scale sewage treatment. However, even in this method, the digested sludge dehydrated filtrate contains a high concentration of ortholine, which is returned to the water treatment system, which increases the load and contributes to the deterioration of the quality of the secondary treated water. Become.
[0006]
In addition, phosphorus removed from raw water by the biological phosphorus removal method accumulates at a high concentration in sludge and is re-released to the water side under anaerobic conditions. The Therefore, there is a need for a method that efficiently removes re-released phosphorus.
[0007]
[Problems to be solved by the invention]
The conventional method for removing phosphorus is the coagulation-precipitation method in which phosphorus in the sewage is agglomerated using a coagulant composed of a metal salt such as ferric salt or aluminum sulfate (porous earth) and lime, and this is precipitated and removed. Generally done. However, this method has a problem that the amount of sludge generated is increased and they are hardly dehydrated.
[0008]
Accordingly, the present invention provides a wastewater treatment apparatus that can efficiently remove phosphorus in sludge generated by sewage treatment, and can reduce the load on wastewater treatment equipment and prevent the outflow of phosphorus into secondary treated water. The purpose is to provide.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a wastewater treatment apparatus of the present invention includes a solid-liquid separation tank that precipitates and separates solids in phosphorus-containing sludge, and a dephosphorizing agent and a separation liquid separated from the solids in the solid-liquid separation tank. A dephosphorization tank that removes phosphorus from the separation liquid by adding calcium ions to react and precipitate the phosphorus in the separation liquid and the added calcium, and the solids separated in the solid-liquid separation tank and the desorption It is characterized by a route that mixes with a dephosphorization solution from which phosphorus has been removed in a phosphorus tank and sends it to a sludge concentration facility .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Figure 1 is an explanatory diagram showing a reference example of wastewater treatment apparatus. This waste water treatment apparatus includes a solid-liquid separation tank 10 that precipitates and separates solid matter in phosphorus-containing sludge, a dephosphorization tank 20 that reacts and removes phosphorus and calcium, a calcium compound storage tank 30, and a pH adjuster storage. In the solid-liquid separation tank 10, the phosphorus-containing sludge inflow pipe 11 drawn from the digestion tank of the wastewater treatment facility and the upper-layer separated liquid separated into the solid-liquid separation are supplied to the dephosphorization tank 20. A separation liquid supply pipe 12 to be supplied and a solid substance extraction pipe 13 for extracting the solid substance settled on the bottom of the tank are provided.
[0011]
The dephosphorization tank 20 has a bottomed cylindrical shape with a large diameter at the top and a funnel shape at the bottom, and two large diameter and small diameter cylinders 21 and 22 are provided therein. . Above the inner peripheral part of the large-diameter cylindrical body 21, the outflow part of the separation liquid supply pipe 12 is located. Further, a calcium compound supply pipe 23, a pH adjuster supply pipe 24, and a dephosphorization agent supply pipe 25 are provided. Each is provided. In addition, a stirrer 26 that generates a downward flow in the cylindrical body 22 is provided inside the small diameter cylindrical body 22.
[0012]
Further, at the bottom of the dephosphorization tank 20, the phosphorus and calcium react with each other to form crystals for phosphorus / calcium compounds (calcium phosphate, calcium hydrogen phosphate, hydroxyapatite, etc.) deposited on the surface of the dephosphorization agent. An object discharge part 27 is provided, and a dephosphorization liquid discharge part 28 is provided at the top. Further, a pH meter 29 is provided at an appropriate position of the dephosphorization tank 20, and a pH adjuster is introduced from the pH adjuster supply pipe 24 in accordance with the measured value of the pH meter 29.
[0013]
The large-diameter cylindrical body 21 is provided in the large-diameter portion at the upper part of the dephosphorization tank, and is installed so that the upper end is located above the water surface. The small-diameter cylindrical body 22 installed inside the large-diameter cylindrical body 21 is a draft tube type stirring section between the inner peripheral portion of the large-diameter cylindrical body 21 and the lower inner peripheral portion of the dephosphorization tank 20. Then, a downward flow is formed on the inner periphery of the small-diameter cylindrical body 22 and an upward flow is formed on the outer periphery by the stirrer 26 to form a circulating flow.
[0014]
Further, between the outer peripheral portion of the large-diameter cylindrical body 21 and the inner peripheral portion of the large-diameter portion at the top of the dephosphorization tank 20, a liquid substantially corresponding to the amount of the separation liquid flowing from the separation liquid inflow pipe 12 rises. It acts as a crystal separation part that precipitates and separates the crystals generated by the reaction in the ascending process. This portion is formed with a sufficient water area so that the small crystals can be surely settled.
[0015]
In the dephosphorization tank 20, the separation liquid flowing in 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 phosphorus in the separation liquid is mixed. Reacts with the added calcium to form a phosphorus-calcium compound, which initially deposits on the surface of a dephosphorizing agent such as calcium phosphate crystals or phosphate rocks previously added as seed crystals. Furthermore, the reaction proceeds on this surface and the crystals gradually grow. When the crystals become a certain size, they separate from the circulation flow due to the difference in specific gravity and settle to the bottom of the tank.
[0016]
At this time, the solid matter in the inflow sludge is sufficiently precipitated and separated in advance in the solid-liquid separation tank 10 so that the product discharge part 27 at the bottom of the dephosphorization tank 20 has high purity and is effective as a fertilizer. Available phosphorus and calcium compounds can be extracted.
[0017]
Moreover, the dephosphorization liquid from which phosphorus has been removed is extracted from the dephosphorization liquid discharge section 28 at the top of the tank, returned to an appropriate position in the wastewater treatment facility, and reprocessed. Further, the solid matter extracted from the solid matter extraction tube 13 of the solid-liquid separation tank 10 is sent to a sludge concentration facility or the like and subjected to a predetermined process.
[0018]
By removing phosphorus in this way, it is possible to prevent a large amount of phosphorus from accumulating in the sludge, to prevent phosphorus from flowing out into the secondary treated water, and to prevent the scale from adhering to the piping. It is possible to reduce the load of the wastewater treatment facility without increasing the amount of sludge.
[0019]
Figure 2 is an explanatory view showing an embodiment of the present invention. Device configuration of the present embodiment, the reference example and because it is substantially the same, wherein the detailed description with the same reference numerals same components as those of the reference example will be omitted.
[0020]
In this embodiment, the solid-liquid separation in the solid-liquid separation tank 10 is limited to the separation of sand and other large specific gravity, and most of the sludge is supplied to the dephosphorization tank 20 as it is to perform the dephosphorization treatment. The solid matter extracted from the solid matter extraction tube 13 of the solid-liquid separation tank 10 and the sludge-containing dephosphorization liquid extracted from the dephosphorization liquid discharge unit 28 of the dephosphorization tank 20 are joined to the merging path 41 to form sludge. It is sent to the concentration facility 42.
[0021]
At this time, in the dephosphorization tank 20, the sludge supplied from the solid-liquid separation tank 10 is allowed to flow out from the dephosphorization liquid discharge section 28 together with dephosphorization water while preventing the sludge from being precipitated together with the crystals at the bottom of the tank. The sedimentation speed V1 of the crystal, the cross-sectional flow velocity V2 of the upward flow in the crystal separation part of the outer periphery of the large-diameter cylindrical body 21, and the cross-sectional flow velocity V3 of the upward flow in the solid-liquid separation tank 10 The relationship is preferably set so that V1>V2> V3.
[0022]
As described above, in the case of the wastewater treatment facility provided with the sludge concentration facility 42, the solid-liquid separation tank 10 separates only the large specific gravity that precipitates with the crystals generated in the dephosphorization tank 20. By setting as described above, the capacity of the solid-liquid separation tank 10 can be significantly reduced as compared with the above-described reference example. Therefore, the apparatus can be downsized, and the digester tank and the sludge concentrating equipment 42 in the existing wastewater treatment equipment. Can be easily installed in a limited space between the two.
[0023]
【The invention's effect】
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 phosphorus can be reliably prevented from flowing out into the secondary treated water, The load on the water treatment facility can be reduced, and a stable water treatment operation can be performed.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a reference example of a wastewater treatment apparatus.
FIG. 2 is an explanatory view showing an embodiment of the waste water treatment apparatus 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 cylindrical body, 22 ... Small diameter cylindrical body, 23 ... Calcium compound supply Tube, 24 ... pH adjusting agent supply tube, 25 ... dephosphorization agent supply tube, 26 ... stirrer, 27 ... product discharge part, 28 ... dephosphorization liquid discharge part, 29 ... pH meter, 30 ... calcium compound reservoir, 31 ... pH adjuster storage tank, 41 ... Confluence route, 42 ... Sludge concentration equipment

Claims (1)

A solid-liquid separation tank that precipitates and separates solids in phosphorus-containing sludge, and calcium added to the separated liquid by adding a dephosphorizing agent and calcium ions to the separated liquid separated in the solid-liquid separation tank A dephosphorization tank that removes phosphorus from the separated liquid by reacting and precipitating, a solid separated in the solid-liquid separation tank and a dephosphorization liquid from which phosphorus is removed in the dephosphorization tank A wastewater treatment apparatus comprising a route for sending to a sludge concentration facility .

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