JPH1128500A - Sludge treating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively dehydrate anaerobic sludge and also to effectively remove and recover phosphorus. SOLUTION: Sludge, to which a cation polymer is added, is flocculated by a first flocculating means 1, and the flocculated sludge is concentrated by a gravity concentrating means 2. The concentrated sludge, to which an inorganic flocculant is added, is flocculated by a second flocculating means 3, and the flocculated sludge, to which an ampholytic polymer flocculant is added, is flocculated by a third flocculating means 4. The flocculated sludge is dehydrated by a dehydrating means 5. The separated water of the gravity concentrating means 2 is treated by a MPA (magnesium ammonium hydrogenphosphate) forming means 6. In this way, when after sludge is flocculated by the cation polymer and is concentrated by gravity, the inorganic flocculant is added, charge neutralization is completely performed, and by adding the ampholytic polymer after that, firm flocs can be formed, allowing the recovery efficiency and the dehydration efficiency of sludge to be markedly improved. By treating the separated water from the gravity concentrating means by the MAP forming means, phosphorus discharged from sludge can be effectively removed and recovered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sludge treatment apparatus, and more particularly to a method for improving the dehydration of anaerobic digested sludge.
The present invention relates to a sludge treatment device that performs efficient phosphorus treatment.

[0002]

2. Description of the Related Art Conventionally, as a method of treating organic sludge generated in a treatment step of sewage, human waste, or organic industrial wastewater, a cationic organic polymer flocculant (hereinafter referred to as "cationic polymer") is used. Addition of a cationic polymer to the sludge and concentration by gravity.Addition of a cationic polymer with high cation strength and an inorganic coagulant to the concentrated sludge and dehydration by a belt press etc. There is a method of adding an inorganic coagulant to sludge, adding an amphoteric organic polymer coagulant (hereinafter referred to as “amphoteric polymer”), and dewatering with a dehydrator. Further, as a sludge treatment method capable of further improving the sludge treatment efficiency and reducing the water content of the dewatered cake than these treatment methods, an inorganic aggregating agent is added to the sludge, and then the amphoteric polymer is added. A method has also been proposed in which sludge is gravity-dehydrated, and then an inorganic flocculant is added to the gravity-dewatered sludge, and then centrifugally dewatered by the centrifugal dehydrator while injecting an amphoteric polymer into the centrifugal dehydrator.

On the other hand, as a method of treating phosphorus-containing wastewater, magnesium ions are added to the phosphorus-containing wastewater, and phosphorus is removed and recovered as MAP (magnesium ammonium phosphate) by the reaction of phosphorus, ammonia and magnesium ions in the wastewater. A method has been proposed.

[0004]

When the above-mentioned conventional sludge treatment method is applied to anaerobic digested sludge, coagulation and dewatering efficiency are poor, and a dewatered cake having a low water content cannot be obtained. In addition, since phosphorus released from sludge is contained in the dehydrated filtrate and discharged out of the system, there has been a problem that the quality of discharged water deteriorates.

On the other hand, the method of removing and recovering phosphorus from the phosphorus-containing wastewater as MAP has been conventionally applied to a separated liquid obtained by solid-liquid separation of digested sludge, and also considers the improvement of dewaterability of digested sludge. However, phosphorus has not been removed and collected as part of the sludge treatment.

An object of the present invention is to solve the above-mentioned conventional problems and to provide an apparatus for efficiently dehydrating phosphorus-containing sludge such as anaerobic digested sludge and efficiently removing and recovering phosphorus. And

[0007]

The sludge treatment apparatus of the present invention is obtained by a first flocculating means for adding a cationic organic polymer flocculant (cationic polymer) to sludge, and the first flocculating means. Gravity concentration means for condensing coagulated sludge, second coagulation means for adding an inorganic coagulant to the concentrated sludge of the gravity condensing means, and amphoteric organic polymer coagulant for coagulated sludge obtained by the second coagulation means (Amphoteric polymer), a dewatering means for dewatering the flocculated sludge obtained by the third flocculation means, and a MAP generating means for processing water separated from the gravity concentrating means. It is characterized by comprising.

In the sludge treatment device of the present invention, a cationic polymer, an inorganic flocculant, and an amphoteric polymer are sequentially added, flocculated, concentrated and dehydrated, whereby a dehydrated cake having a low water content can be efficiently obtained. That is, when the sludge is coagulated with a cationic polymer and concentrated by gravity, and then an inorganic coagulant is added, the charge neutralization is completely performed, and a strong floc can be formed by the subsequent addition of the amphoteric polymer. The rate and dewatering efficiency are significantly improved.

[0009] Further, the separated water from the gravity concentrating means is subjected to MAP.
By treating with the generation means, phosphorus released from the sludge can be efficiently removed and collected.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 is a system diagram showing an embodiment of a sludge treatment apparatus according to the present invention.

In the figure, 1 is a first coagulation tank, 2 is a gravity concentrator,
2A is a separation water tank, 3 is a second coagulation tank, 4 is a third coagulation tank, 5
Is a belt press dehydrator, 6 is a MAP reaction tower, 7 is a cationic polymer storage tank, 8 is an inorganic flocculant storage tank, 9 is an amphoteric polymer storage tank, P ₁ , P ₂ , P ₃ , and P ₄ are pumps, M ₁ ,
M ₂ , M ₃ , M ₄ and M ₅ are agitators.

Phosphorus-containing sludge such as anaerobic digested sludge is first subjected to coagulation treatment in a first coagulation tank 1 by adding a cationic polymer from a cation polymer storage tank 7.

The coagulated sludge is concentrated by gravity in the gravity concentrator 2.
The concentrated sludge is then added with an inorganic coagulant from an inorganic coagulant storage tank 8 in a second coagulation tank 3. The inorganic coagulant neutralizes the charge of the sludge to condition the sludge, and also fixes the soluble phosphorus.

The coagulated sludge in the second coagulation tank 3 is further granulated and coagulated in the third coagulation tank 4 by adding an amphoteric polymer from the amphoteric polymer storage tank 9. This coagulated sludge is pump P
_It is fed to the belt press dewatering machine 5 by ₄ and dewatered. In this belt press dewatering machine, the sludge to be supplied is already sufficiently concentrated and agglomerated, the strength of the floc is strong, and the solid content is high, so that a dewatered cake with a sufficiently low water content can be efficiently obtained. Can be. The obtained dehydrated cake is discharged out of the system.

Separated water separated by concentration of sludge in the gravity concentrator 2 is extracted from the separation water tank 2A and treated in the MAP reaction tower 6. The dewatered filtrate of the belt press dewatering machine 5 is also processed in the MAP reaction tower 6.

In the MAP reaction tower 6, p
Under conditions of H, preferably pH 7.5 to 10, more preferably pH 8 to 9, alkali such as NaOH is injected, and when magnesium is insufficient for MAP precipitation, MgCl ₂ , Mg (OH ₂ ) A magnesium compound such as ₂ (may be any containing a magnesium compound, and may be seawater) is added (if ammonia is insufficient for MAP precipitation, ammonia is further added). The MAP is generated and precipitated by the reaction of the phosphorus and ammonia in the magnesium with magnesium, thereby removing the phosphorus in the liquid. The magnesium compound in the MAP reaction tower 6 is preferably added in such an amount that the molar ratio of Mg in the liquid to P in the liquid is about 1.2 to 1.5.

The treated water in the MAP reaction tower 6 usually has a phosphorus concentration of about 10 to 40 mg / L, and is returned to the sludge inflow point as return water.

The MAP particles generated in the MAP reaction tower 6 are extracted from the bottom of the MAP reaction tower and are effectively used as a fertilizer containing phosphorus and nitrogen.

In the present invention, the cationic polymer added in the first flocculation tank 1 includes dimethylaminoethyl acrylate, dimethylamino (meth) acrylate (DA
M), one or more homopolymers or copolymers such as dimethylaminopropyl (meth) acrylate.

The amount of the cationic polymer varies depending on the properties of the sludge and the type of the cationic polymer to be added.
Usually, 1 to 1.5% by weight based on sludge dry TS
It is said. The coagulation reaction in the first coagulation tank 1 is preferably performed under slow stirring, and the coagulation reaction time may be about 2 to 3 minutes.

As the gravity dewatering machine 3 for gravity-concentrating the coagulated sludge in the first coagulation tank 1, an inclined screen (wedge wire screen), a filter cloth traveling type (belt press), a rotary screen type, or the like can be used. Preferably, a screen having a mesh size of about 1 to 2 mm is used.

The gravity concentrator 2 generally has a sludge concentration of 3
Although it is dehydrated to about 6%, in order to stably perform the processing in the subsequent step, a part of the separated water is overflowed from the separated water tank 2A of the gravity dehydrator 2 to the second flocculation tank 3 as necessary. It is preferable to adjust the concentration of the sludge in the second flocculation tank 3 to 3 to 4%.

Examples of the inorganic flocculant to be added to the second flocculation tank 3 include ferric chloride, aluminum sulfate, aluminum chloride, polyaluminum chloride (PAC), ferric sulfate, and polyiron sulfate. Although the amount of addition depends on the type of the inorganic coagulant used, it is preferably 20 to 35% by weight based on the dry TS of the sludge. This second
The aggregation reaction in the aggregation tank 3 is preferably performed by rapid stirring, and the aggregation reaction time may be about 1.5 to 2 minutes.

The amphoteric polymer added in the third flocculation tank 4 has a colloid equivalent value (a value) determined by colloid titration at pH 3, which indicates the amount of a cationic structural unit (cation group) (hereinafter referred to as “cation amount”). 1.0 to 3.7 meq / g,
P indicating the difference between the amount of the anionic constitutional unit (anion group) (hereinafter referred to as “the amount of anion”) and the amount of the cationic constitutional unit
The colloid equivalent value (b value) determined by colloid titration with H7 is-
1.7 to 0.7 meq / g, and the value of (ab) / a indicating the ratio of the amount of anion / the amount of cation is 0.8 to 1.
8 are preferable. Examples of such amphoteric polymers include copolymers of anionic monomer components and cationic monomer components, anionic monomer components, cationic monomer components, and nonionic monomers. Mannich-modified or Hoffman-decomposed products of a copolymer of the components, or a copolymer of an anionic monomer component and a nonionic monomer component.

Here, examples of the anionic monomer component include acrylic acid (AA), sodium acrylate (NaA), methacrylic acid, sodium methacrylate and the like. Examples of the cationic monomer component include dimethylaminoethyl acrylate, dimethylaminoethyl (meth) acrylate (DAM),
Examples thereof include dimethylaminopropyl (meth) acrylate and quaternized products thereof. Specific examples of the quaternary compound include dimethylaminoethyl acrylate quaternary compound (DAA). Also,
Dimethylaminopropylacrylamide hydrochloride (DA
PAAm) may be used. Examples of the nonionic monomer component include acrylamide (AAm), methacrylamide, and N, N′-dimethyl (meth) acrylamide. Specific examples of the copolymer of these compounds include DAA / AA / AAm copolymer, DAM / AA / AAm copolymer, and DAPAAm /
AA / AAm copolymer, DAA / AA copolymer, or N
Mannich-modified aA / AAm copolymers can be mentioned.

The amount of the amphoteric polymer to be added is preferably 0.2 to 0.3% by weight based on the dry sludge TS. The aggregation reaction in the third aggregation tank 4 is preferably performed with slow stirring, and the aggregation reaction time may be 3 to 4 minutes.

As a dehydrator for dehydrating the coagulated sludge in the third coagulation tank 4, a screw press dehydrator, a centrifugal dehydrator or the like may be used in addition to a belt press dehydrator.

In FIG. 1, the dewatered filtrate of the belt press dewatering machine 5 is also supplied to the MAP reaction tower 6 for treatment. However, since the dewatered filtrate has a relatively low phosphorus concentration, the MAP is depleted.
Without being treated in the reaction tower 6, the water may be discharged out of the system as it is, or may be returned to the inflow point as return water.

Although the sludge treatment apparatus of the present invention is effective for treating phosphorus-containing sludge such as anaerobic digested sludge, it is also effective for mixed sludge of digested sludge and excess sludge.

[0031]

EXAMPLES The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples unless it exceeds the gist.

In the following examples and comparative examples, raw sludge was treated with unwashed digested sludge in the sewage treatment digestion tank having the following properties. The following were used as the cationic polymer, the inorganic flocculant and the amphoteric polymer.

Raw mud properties pH: 7.0 Electric conductivity (ms / m): 310 TS (%): 1.15 VTS (%): 65 Fiber content (%): 7.51 PO ₄ -P (mg) / L): 31 cationic polymer : Kurita Kogyo Co., Ltd. “Crifix CP604” inorganic flocculant : polyiron sulfate or ferric sulfate amphoteric polymer : colloid equivalent (a) value at pH 3 is 2.6 meq / g, pH 7 Equivalent (b)
DAA / with a value of 0 meq / g and a value of (ab) / a of 1
AA / AAm copolymer The following were used as a screen concentrator and a belt press dehydrator as gravity concentrators.

Screen Concentrator : Wedge Wire Gravity Screen Belt Press Dehydrator : Belt Press Dehydrator Example 1 Sludge treatment was performed by the sludge treatment apparatus shown in FIG.

First, a cationic polymer was added to the raw sludge in the first flocculation tank 1 at 0.87% by weight with respect to the sludge TS, and 50 r
The mixture was stirred at pm for 3 minutes and concentrated twice by gravity concentrator 2.

Thereafter, 34.8% by weight of polyiron sulfate was added to the sludge TS in the second flocculation tank 3 and the mixture was added at 150 rpm for 2 hours.
After stirring for 3 minutes, the amphoteric polymer is sludge T
0.26% by weight of S was added, and the mixture was stirred at 40 rpm for 4 minutes.

The coagulated sludge from the third coagulation tank 4 was dewatered by a belt press dewatering machine.

Separated water from the gravity concentrator 2 and dewatered filtrate from the belt press dehydrator were treated in the MAP reaction tower 6. The processing conditions of the MAP reaction tower 6 were as follows.

PH: 8.2 MgCl ₂ added: 77 mg-Mg / L LV: 60 m / hr Table 1 shows the water content, sludge recovery, and treatment rate of the dehydrated cake obtained by this treatment.

Table 1 also shows the phosphorus concentration of the separated water and the dehydrated filtrate supplied to the MAP reactor 6 and the phosphorus concentration of the treated water of the MAP reactor 6.

Example 2 The procedure of Example 1 was repeated, except that ferric sulfate was added in an amount of 15.7% by weight to the sludge TS instead of polyiron sulfate. The results are shown in Table 1. Was.

Comparative Example 1 In Example 1, the amount of the cationic polymer added was changed to sludge T
S was set to 1.13% by weight, and the same treatment was performed except that the obtained coagulated sludge was directly dewatered by a belt press dehydrator.
No AP recovery was performed. ).

[0043]

[Table 1]

As is clear from Table 1, Examples 1 and 2 in which a cationic polymer, an inorganic flocculant and an amphoteric polymer are used in combination.
According to 2, the treatment speed is twice or more, the water content of the dehydrated cake is improved by 6 to 7%, and the sludge recovery rate is improved by 10 to 15% as compared with Comparative Example 1 in which the treatment is performed only with the cationic polymer.

Further, according to the present invention, phosphorus in sludge can be efficiently removed and recovered as MAP.

[0046]

As described in detail above, according to the sludge treatment apparatus of the present invention, phosphorus-containing sludge such as anaerobic digested sludge can be efficiently dehydrated, and phosphorus can be efficiently removed and recovered. Can be.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of a sludge treatment apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st flocculation tank 2 Gravity concentrator 2A separation water tank 3 2nd flocculation tank 4 3rd flocculation tank 5 Belt press dehydrator 6 MAP reaction tower 7 Cationic polymer storage tank 8 Inorganic coagulant storage tank 9 Amphoteric polymer storage tank

Claims (1)

[Claims] 1. A first flocculating means for adding a cationic organic polymer flocculant to sludge, a gravity concentrating means for condensing the flocculated sludge obtained by the first flocculating means, and a concentration of the gravity concentrating means. A second flocculating means for adding an inorganic flocculant to the sludge, a third flocculating means for adding an amphoteric organic polymer flocculant to the flocculated sludge obtained by the second flocculating means, and a third flocculating means A sludge treatment apparatus comprising: a dewatering means for dewatering the flocculated sludge obtained in the above step; and a MAP generating means for treating the separated water from the gravity concentration means.