JP2013193046A - Dehydrating method and device of pressure floating sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device of dehydrating pressure floating sludge which easily dehydrate organic sludge from a pressure flotation tank to obtain a low water content ratio.SOLUTION: Pressurized water is added to organic drainage, and flotation separation treatment is carried out in a pressure floatation tank 1. Separated scum is introduced in a scum receiving tank 3, and an ampholytic polymer coagulant is added. Then the scum is introduced in a sludge sedimentation tank 7, is stirred by a stirrer 7a, and adherent bubbles are separated, and the sludge is settled and concentrated. An iron salt-based coagulant is added to concentrated sludge in a sludge storage tank 11, and then is dehydrated by a dehydrator 13.

Description

  The present invention relates to a dewatering method and apparatus for pressurized flotation sludge that dehydrates organic sludge from a pressurized flotation tank using a dehydrator, and in particular, pressurized flotation sludge capable of dehydrating sludge to a low water content. The present invention relates to a dehydration processing method and apparatus.

  As a method and apparatus for dewatering organic sludge that has been floated and separated in a pressurized flotation tank, the sludge from the pressurized flotation tank is introduced into a coagulation agitation tank, and a polymer flocculant is added and mixed in Patent Document 1. In addition, it is described that the floc shape having a large particle size is supplied to a dehydrator and dehydrated.

JP-A-8-71551

  In the above-mentioned Patent Document 1, since the organic sludge from the pressurized flotation tank is made into a floc form having a large particle size with a polymer flocculant, it is presumed that the dewatering efficiency is improved as compared with the case where the polymer flocculant is not added. However, after the polymer flocculant is added to the organic sludge, the entire amount of the sludge is supplied to the dehydrator. Therefore, the load on the dehydrator is large, and the moisture content of the sludge after dehydration is difficult to decrease.

  An object of the present invention is to provide a method and an apparatus for dewatering pressurized floating sludge that can easily dehydrate organic sludge from a pressurized flotation tank so as to have a low water content.

  The method of dewatering a pressurized flotation sludge according to the present invention includes a step of adding an amphoteric polymer flocculant to the organic sludge from the pressure flotation tank, and introducing the sludge to which the amphoteric polymer flocculant has been added into the settling tank. , A step of stirring with a stirrer to separate bubbles from sludge and settling the sludge, and a step of dewatering the settling sludge from the settling tank with a dehydrator.

  The dewatering apparatus for pressurized flotation sludge of the present invention accepts a polymer flocculant addition means for adding an amphoteric polymer flocculant to the organic sludge from the pressure flotation tank, and sludge to which the amphoteric polymer flocculant is added, It has a settling tank with a stirrer which stirs with a stirrer, isolate | separates bubbles from sludge, and makes sludge settle, and a dehydrator which dehydrates the settled sludge from the settling tank.

  In this invention, it is preferable that the to-be-processed water introduce | transduced into a pressurized levitation tank is the biological treatment liquid which processed the organic waste_water | drain with the carrier-type biological treatment means.

  Moreover, in this invention, after adding an iron salt type flocculant to the sedimentation sludge from a sedimentation tank, it is preferable to spin-dry | dehydrate with the said dehydrator.

  In the dewatering method and apparatus for pressurized flotation sludge of the present invention, when an amphoteric polymer flocculant is added to the organic sludge from the pressurized flotation tank, the charge of the organic sludge is neutralized and adheres to the organic sludge Air bubbles (micro air) that have been removed are easily removed. This charge neutralization makes it easy for organic sludge particles to adhere to each other and grow. Moreover, when the bubbles are detached, the granulated sludge is likely to settle. Therefore, the sludge to which the amphoteric polymer flocculant is added is introduced into the settling tank and stirred, thereby generating granulated sludge that is easy to settle due to bubbles being discharged, and this granulated sludge settles at the bottom of the settling tank. The settled sludge is easily dehydrated with a large particle size and is concentrated by sedimentation. By dehydrating the settled sludge with a dehydrator, a dehydrated sludge having a low water content can be obtained efficiently. .

  By adding an iron salt flocculant to the settled sludge, the stickiness of the organic sludge decreases, making it difficult for the organic sludge to adhere to the inner surface of the dehydrator, filter cloth, etc. Dewatering efficiency is improved.

It is a systematic diagram explaining embodiment of this invention. It is explanatory drawing of an Example.

  Hereinafter, the present invention will be described in more detail.

  In the present invention, to-be-treated water in which organic sludge-containing water and pressurized water are mixed is introduced into the pressurized flotation tank, and the organic sludge is floated and separated.

  As organic sludge containing water, what biologically treated organic substance containing water is suitable. In particular, biologically treated water that contains biologically treated cells and therefore has high sludge adhesiveness is preferred.

  As such biological treatment water, an electronic component production process wastewater such as liquid crystal (especially, an electronic component production process wastewater having a BOD of 50 to 5000 mg / L, particularly about 100 to 1000 mg / L is suitable), a carrier-type biological treatment tank, In particular, biologically treated water which is biologically treated by passing it through a floating carrier type biological treatment tank such as a sponge can be mentioned. When raw water is passed through the carrier-type biological treatment tank, the biofilm of the carrier gradually grows. Then, the grown biofilm is peeled off and flows out from the biological treatment tank as a bacterial cell-containing sludge.

  The MLVSS concentration of this biologically treated water is preferably about 20 to 2000 mg / L, particularly about 50 to 500 mg / L, but is not limited thereto.

  The pressurized water added to the biologically treated water is water in which air is dissolved under pressure, and the amount added to the biologically treated water may be the same as that used in the normal flotation separation of the biologically treated water. What is necessary is just to determine experimentally according to a property.

  The configuration of the pressurized levitation tank is not particularly limited, and various types can be used as long as bubbles adhere to the sludge in the tank and the sludge floats and is separated.

  In the embodiment shown in FIG. 1, in the pressurized levitation tank 1, pressurized water-containing treated water is introduced into the feed well 1a, and this pressurized water-containing treated water is supplied to the upper part in the inner tank 1d by the distributor 1b. The sludge that floats (scum) is taken out from the scum box 1c by the transfer pipe 2 and transferred to the scum receiving tank 3 described later.

  The water from which the floating sludge has been separated descends in the inner tank 1d, wraps around the lower end of the inner tank 1d, rises between the inner tank 1d and the outer tank 1e, and is taken out from the treated water trough 1f to the outside of the tank. It is. The distributor 1b is rotated by a motor 1g. However, the type of the pressurized levitation tank 1 is not limited to this. A plurality of pressurized levitation tanks 1 may be installed in parallel.

  The SS concentration of the organic sludge (scum) that has been levitated and separated in the pressurized flotation tank 1 is usually about 0.6 to 2 wt%. This organic sludge is preferably introduced into the scum receiving tank 3, and the amphoteric polymer flocculant is added by the addition means 4 comprising a chemical tank and a chemical injection pump, and the organic sludge (scum) is not destroyed by the agitator 3a. Stir with moderate stirring intensity. As this amphoteric polymer flocculant, a so-called anion-rich type amphoteric polymer flocculant having more anions than those having an anion-cation ratio of 1: 1 (anion ratio 50%) is preferable. A cation ratio of about 1: 0.95 to 1: 0.4, particularly about 1: 0.93 to 1: 0.7 is preferred.

  Examples of such an amphoteric polymer flocculant include a copolymer of an anionic monomer component and a cationic monomer component, an anionic monomer component, a copolymer of a cationic monomer component and a nonionic monomer component, or Examples thereof include Mannich-modified products or Hoffmann degradation products of copolymers of anionic monomer components and nonionic monomer components.

  Examples of the anionic monomer component include acrylic acid (AA), sodium acrylate (NaA), methacrylic acid, and sodium methacrylate.

  Examples of the cationic monomer component include dimethylaminoethyl acrylate, dimethylaminoethyl (meth) acrylate (DAM), dimethylaminopropyl (meth) acrylate, and quaternized products thereof. Specific examples of the quaternized product include dimethylaminoethyl acrylate quaternized product (DAA). Further, dimethylaminopropylacrylamide hydrochloride (DAPAAm) may be used.

  Examples of the nonionic monomer component include acrylamide (AAm), methacrylamide, N, N-dimethyl (meth) acrylamide, and the like.

  The amount of amphoteric polymer flocculant added is preferably about 0.3 to 1.5% by weight, especially about 0.5 to 1.0% by weight per ds, based on the organic sludge (scum) from the pressurized flotation tank. .

  The addition of this amphoteric polymer flocculant neutralizes the charge of the organic sludge, dissociates the attached air bubbles, associates the sludge and grows particles, and increases the specific gravity and tends to settle. Become tinged.

The organic sludge to which this amphoteric polymer flocculant is added is introduced into the sludge settling tank 7 by the pump 5 and the pipe 6, and stirred with a stirring strength sufficient to prevent the sludge from collapsing by the stirrer 7a, thereby promoting sludge association and bubble separation. And let the sludge settle. The stirring strength G value at this time is preferably about 70 to 150 sec ⁻¹ , the residence time of the sludge settling tank 7 is preferably about 1200 to 2500 sec, and the G · T value is 14 × 10 ^{4 to} 25 ×. About 10 ⁴ is preferable.

This G value is a stirring gradient and is an index of stirring intensity, and is expressed by the following equation.
G = (Pg / μ) ^1/2 [1 / s]
P is the power [kg · m / m ³ / s] applied per unit volume of fluid, μ is the viscosity coefficient [kg / m / s], and g is the gravity conversion coefficient [m / s ² ].

  In the sludge settling tank 7, it is preferable to concentrate the sludge concentration 1.5 to 7 times, particularly 2 to 3 times.

  The supernatant water of the sludge settling tank 7 is taken out of the tank through the separated liquid take-out pipe 7b. The concentrated sludge settled in the sludge settling tank 7 is introduced into the sludge storage tank 11 through the pump 9 and the pipe 10, and the iron salt-based flocculant is added by the adding means 12 and the sludge is not destroyed by the stirrer 11a. Stir with stirring intensity. By adding this iron salt-based flocculant, the stickiness of the sludge is lowered, the adhesion to the filter cloth of the dehydrator in the latter stage, the inner surface of the equipment and the like is lowered, and the handling property of the sludge is improved.

  Examples of the iron salt-based flocculant include polyiron sulfate, ferric chloride, and ferric sulfate, and polyiron sulfate is particularly preferable. The addition amount of the iron salt-based flocculant is preferably about 300 to 1500 mg / L, particularly about 500 to 1000 mg / L per liter of concentrated sludge from the sludge settling tank 7. An aluminum flocculant or a cationic polymer flocculant may be added instead of or together with the iron salt flocculant. It is preferable to add only.

  Sludge to which a coagulant such as an iron salt coagulant is added is introduced into the dehydrator 13 and dehydrated. As the dehydrator, various types such as a filter press dehydrator, a belt press dehydrator, a centrifugal dehydrator, and an electroosmotic dehydrator can be used, but a filter press dehydrator is preferable because of low power cost.

  Hereinafter, examples and comparative examples will be described.

  The electronic component manufacturing process waste water (BOD 20 mg / L, SS 300 mg / L) was treated using the apparatus shown in FIG. The apparatus shown in FIG. 2 has a branch line 20 connected to the transfer pipe 2 in the apparatus shown in FIG. 1, and a part of sludge (scum) from the pressurized flotation tank 1 is directly centrifuged through the branch line 20. It is possible to send it to the dehydrator, and other configurations are the same as those in FIG.

The main conditions are as follows.
Processed water flow rate: 453 m ³ / day
Pressurized water addition amount: 80 m ³ / day
Capacity of scum receiving tank 3: 4 m ³
Amphoteric polymer flocculants:
Acrylate amphoteric polymer with anion-cation ratio = 1: 0.93
Weight average molecular weight = 6 million
Addition amount = 0.5 wt% (vs. scum)
Capacity of the sludge settling tank 7: 20 m ³
Capacity of the sludge storage tank 11: 15 m ³
Iron salt-based flocculant: iron polysulfate (added amount: 750 ppm (vs. concentrated sludge))
Dehydrator 13: Filter press dehydrator

Sludge (floating scum) branch flow B to branch line 20 is changed within the range of 335 to 95 m ³ / day, and sludge (floating scum) inflow A to scum receiving tank 3 is 100 to 340 m ³ / day.
The range was changed. Table 1 shows the number of rotations of the agitator 7 in the sludge settling tank 7. Table 1 shows the sedimentation sludge concentration Y (%) sent in the sludge sedimentation tank 7 and sent to the sludge storage tank 11, the dewatered sludge (cake) moisture content Z (%) from the dehydrator 13, and the evaluation results.

As Table 1, No stirring intensity G value agitator 7a of the sludge settling tank 7 ^{(sec -1)} and the product G · T value of the residence time T (sec) and 14 × ^{10 4} ~25 × ¹⁰ 4 . In 2, 3, and 4, the sedimentation sludge (concentrated sludge) concentration in the sludge sedimentation tank 7 was high, and the dehydrator 13 was able to perform the dehydration process stably. No. In 2, 3, and 4, the separation liquid in the sludge settling tank 7 was not turbid with fine SS.

Claims (6)

Adding an amphoteric polymer flocculant to the organic sludge from the pressurized flotation tank;
Introducing the sludge to which the amphoteric polymer flocculant has been added into a settling tank, stirring the mixture with a stirrer to separate bubbles from the sludge, and settling the sludge;
A method for dewatering pressurized floating sludge, comprising the step of dewatering sedimented sludge from a sedimentation tank with a dehydrator.   2. The method of dewatering treatment of pressurized levitation sludge according to claim 1, wherein the water to be treated introduced into the pressurized levitation tank is a biological treatment liquid obtained by treating organic wastewater with a carrier-type biological treatment means.   3. The method for dewatering pressurized floating sludge according to claim 1, wherein an iron salt flocculant is added to the sedimented sludge from the sedimentation tank and then dewatered by the dehydrator. A polymer flocculant addition means for adding an amphoteric polymer flocculant to the organic sludge from the pressurized flotation tank;
Accepting the sludge to which the amphoteric polymer flocculant has been added, separating the bubbles from the sludge by stirring with a stirrer,
A dewatering apparatus for pressurized floating sludge, comprising a dehydrator for dewatering the settled sludge from the settling tank.   5. The pressurized levitation sludge dewatering apparatus according to claim 4, wherein the water to be treated introduced into the pressurized levitation tank is a biological treatment liquid obtained by treating organic wastewater with a carrier-type biological treatment means.   6. The dewatering of pressurized flotation sludge according to claim 4 or 5, further comprising iron salt flocculant addition means for adding an iron salt flocculant to the sludge supplied from the settling tank to the dehydrator. Processing equipment.

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