JP2000189998A - Method and device for concentrating sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To concentrate sludge into high concentration by using a membrane. SOLUTION: At the time of flocculating by adding an aluminum based flocculant in a water treating process and taking out settled sludge to concentrate, the sludge 6 is charged to a concentration tank 4, in which a membrane module 5 is mounted to be dipped, is adjusted to a prescribed acidic pH range with sulfuric acid, filtered with the membrane module 5 and concentrated by discharging the filtrate 16 outside the tank. As a result, the filtration is performed by decreasing the viscosity of the sludge? 6 to make easily flowable, metal oxides or microorganisms are hardly stuck to the membrane surface, which is kept acidic, and then, the clogging of the membrane module 5 and the plugging of the flow passage between membranes are prevented and the sludge is highly concentrated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for concentrating sludge such as coagulated sediment sludge generated in the field of water treatment such as purified water and sewage, and sludge such as filter pond backwash drainage sludge.

[0002]

2. Description of the Related Art Conventionally, sludge such as coagulated sediment sludge generated in the field of water treatment such as purified water and sewage, and sludge such as filtration pond backwash drainage sludge are concentrated and then dewatered. As an apparatus for sludge concentration, there are a natural sedimentation type concentration tank using natural sedimentation, and a mechanical concentration apparatus using a filtration membrane or the like.

[0003]

However, in recent years, sludge generated in coagulation sedimentation ponds such as water purification plants has increased organic matter due to deterioration of raw water quality, and added aluminum-based coagulant (sulfuric acid band, PAC, etc.). Increasing rates have led to poor enrichment. In particular, an aluminum-based flocculant is used in sludge in Al (OH) ₃ Forms a hydrated floc, and since this floc easily holds water molecules around,
This is a factor that deteriorates the concentration.

[0004] As a result, in the natural sedimentation type thickening tank, the concentration of sludge becomes low, and the dewatering property of the dewatering machine becomes low.
Dehydration equipment must be increased. Concentration devices that use filtration membranes have the advantages of shortening the processing time and reducing the installation area of the device.However, the viscosity increases significantly as the concentration of sludge increases, resulting in clogging of the filtration membrane and inter-membrane space. Since a situation that hinders the operation such as blockage of the flow path may occur, it is difficult to concentrate at a high concentration.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to enable sludge to be concentrated at a high concentration using a filtration membrane.

[0006]

Means for Solving the Problems To solve the above problems, the sludge concentrating method of the present invention is characterized in that, in the water treatment step, an agglomeration agent is added by adding an aluminum-based coagulant, and the separated sludge is extracted and concentrated. Sludge is put into a concentration tank in which the membrane is immersed and installed, filtered by the separation membrane while adjusting the pH to a predetermined acidic side with an acid, and concentrated by drawing the filtrate out of the tank.

[0007] The present invention is characterized in that the filtrate is injected into raw water flowing into the coagulation treatment facility.

The sludge concentrating apparatus of the present invention is a sludge concentrating apparatus for performing the above-described sludge concentrating method, and comprises a thickening tank into which sludge to which an aluminum-based coagulant is added is placed, and a separating tank immersed in the tank. A membrane, a filtrate discharge system communicating with the membrane permeation side of the separation membrane, a pH measuring means for measuring the pH of the sludge in the tank, a chemical injecting means for injecting a pH adjusting agent into the sludge in the tank, and the pH A controller provided to be connected to the measuring means and the chemical injecting means, and controlling the injection amount of the pH adjusting agent by the chemical injecting means based on the pH measurement value measured by the pH measuring means, I do.

Here, the predetermined acidic pH range is defined as Al (OH) formed in the sludge by the aluminum-based flocculant.
_Three It is an acidic pH range where the floc is redissolved as Al ³⁺ , and has a pH of about 3 to 5. If it is higher than this, re-dissolution becomes insufficient, and if it is lower than this, the pH adjuster is wasted.

The acid may be any one that acts as a pH adjuster, such as sulfuric acid or hydrochloric acid.

As the separation membrane, an acid-resistant separation membrane which is not damaged in the above-mentioned acidic pH range, such as a ceramic membrane and an organic membrane, is used.

According to the method and apparatus for concentrating sludge as described above, Al (OH) ₃ By changing the floc to Al ³⁺ , the sludge becomes less viscous and flows more easily, making filtration easier, and the membrane surface is kept in an acidic region, so that metal oxides and microorganisms are reduced. Because it is difficult to adhere, clogging of the separation membrane can be prevented, and when multiple elements of the separation membrane are installed, it is difficult to block the flow path between the membranes. I can do it.

[0013] Further, by injecting the filtrate into the raw water flowing into the coagulation treatment equipment, Al ³⁺ contained in the filtrate permeating the separation membrane is reused to coagulate turbidity and algae in the raw water. And the amount of coagulant injected into the coagulation treatment equipment can be reduced.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

The sludge concentrating apparatus shown in FIG. 1 is for condensing sludge that has been coagulated and settled by adding an aluminum-based coagulant in a coagulation settling tank 2 into which raw water is introduced via a landing well 1 in a water purification plant. A membrane module 5 is provided in a concentration tank 4 in which a sludge supply pipe 3 from the coagulation sedimentation tank 2 is opened at an upper part, and a sludge extraction pipe 7 for extracting sludge 6 is opened at a lower part.

The membrane module 5 is, for example, as shown in FIG. 2, in which an acid-resistant membrane element 9 such as a tubular ceramic membrane is provided inside a casing 8 having an opening at the top and bottom and spaced apart from each other. The openings are arranged inside the formed water collecting chamber 10, and are stacked in a plurality of stages so as to be immersed in the sludge 6 with an appropriate gap between the tank and the bottom.

A filtrate outlet pipe 11 connected at one end to a water collecting chamber 10 of each membrane module 5 is provided with a pump device 12 and guided to a treated water tank 13. Below the membrane module 5, there is provided an air diffuser 15 for jetting a stirring gas such as air supplied from an air supply means such as a blower 14.

In the treated water tank 13, a treated water pipe 17 for guiding the filtrate 16 in the tank to a subsequent treatment step, a return pipe 19 provided with a pump device 18 and reaching the above-mentioned landing well 1, and a pump device 20 are provided. Washing water pipe 2 which is installed in the middle of the filtrate outlet pipe 7
1 is provided.

The concentrating tank 4 is also opened with a chemical injection pipe 25 guided from a chemical tank 23 containing an acid such as sulfuric acid 22 and provided with a chemical injection pump 24, and the pH of the sludge 6 in the tank.
Is provided.

A control device 27 connected to the pH meter 26 and the chemical injection pump 24 controls the discharge amount of the chemical injection pump 24 based on the pH measured by the pH meter 26. .

The operation of the above configuration will be described.

The sludge 6 introduced into the concentration tank 4 from the coagulation sedimentation tank 2 through the supply pipe 3 flows through the inside and outside of the casing 8 of the membrane module 5 by the agitated gas ejected from the air diffuser 15, while the pump device The filtrate 16 is filtered from the membrane surface by the suction pressure acting on the membrane element 9 through the filtrate outlet pipe 11, and the filtrate 16 that has passed through the membrane surface is collected by the collection chamber 1.
0, led out to the treated water tank 13 through the filtrate outlet pipe 11,
Thereby, the concentrated sludge 6 accumulates at the bottom of the tank. The filtrate 16 inside the treatment water tank 13 is guided to a subsequent treatment step through a treatment water pipe 17.

At this time, the pH of the sludge 6 in the concentration tank 4 is
The discharge amount of the chemical injection pump 24 is controlled by the control device 27 based on the measured pH value by the H meter 26, and the sulfuric acid 22 in the chemical tank 23 is injected through the chemical injection tube 25 by an appropriate amount. The sludge 6 is constantly adjusted to pH 3 to 5 as appropriate.

Thus, the A formed in the sludge 6
l (OH) ₃ The floc is converted to Al ³⁺ and redissolved, the viscosity of the sludge 6 is reduced, the sludge is sufficiently stirred by the stirring gas, the flow passage between the membrane elements 9 is prevented, and the membrane of the membrane element 9 is prevented. Since the surface is kept in an acidic region and metal oxides and microorganisms are unlikely to adhere thereto, clogging of the membrane element 9 is prevented, so that a high filtration flux is maintained and high concentration is efficiently performed. .

Depending on the amount of turbidity and algae in the inflowing raw water, a part of the filtrate 16 flowing out of the treated water tank 13 is injected into the landing well 1 through the return pipe 19 by the pump device 18. As a result, the Al ³⁺ (A
l ₂ Since (SO ₄ ) ₃ ) exerts a flocculating action to flocculate turbidity and algae in the inflowing raw water, the amount of flocculant used in the flocculating sedimentation basin 2 can be reduced.

The filtrate 16 is used not in the landing well 1 but in the flocculation settling tank 2
Although the agglomerating action of Al ^{3+ in} the filtrate 16 can be used even if the flow is returned to the above, it is necessary to consider that the flow fluctuation caused by the filtrate 16 does not have an adverse effect.

Also, periodically or with the membrane element 9
When the permeation flux at the time is lowered, the filtrate 16 in the treatment water tank 13 is added to the filtrate outlet pipe 7 by the pump device 20 and the washing water pipe 21 after adding a washing reagent such as sodium hypochlorite as necessary. , And pressure-fed to the permeation side of the membrane element 9 to perform an operation of backwashing for chemically and physically removing clogging substances. However, as described above, clogging of the membrane element 9 hardly occurs even during the concentration process, so that the frequency of cleaning is reduced and the life of the membrane is prolonged.

[0028]

As described above, according to the present invention, when condensing sludge containing an aluminum-based flocculant, the sludge is filtered through a separation membrane immersed and installed in the sludge while being adjusted to a predetermined acidic pH range. Since the filtrate was led out of the tank, A
l (OH) ₃ It reduces the viscosity of sludge caused by flocs, prevents clogging of separation membranes and blockages of channels between membranes, enables efficient concentration with high filtration flux, and enables high-concentration sludge to be obtained. it can. Therefore, compared to the past,
Not only can the frequency of cleaning the separation membrane be reduced and the life of the membrane can be extended, but also the membrane area can be reduced at the stage of designing the apparatus.

Further, by injecting the filtrate containing Al ³⁺ into the raw water flowing into the coagulation treatment equipment, the amount of the coagulant used in the coagulation treatment equipment can be reduced by recycling Al ³⁺ .

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a schematic overall configuration of a sludge aggregation device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a conventional membrane module installed in the sludge flocculation apparatus.

[Explanation of symbols]

 4 Concentration tank 5 Membrane module 6 Sludge 11 Filtrate discharge pipe 24 Chemical injection pump 25 Chemical injection pipe 26 pH meter 27 Controller

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) C02F 1/44 C02F 1/44 K 1/52 1/52 EF term (reference) 4D006 GA02 HA21 HA93 HA95 KA33 KA43 KB13 KB30 KC03 KC16 KD11 KD24 KE15R MA02 MB12 MC03X PA02 PB08 PC64 4D015 BA04 CA01 CA14 DA04 DA06 EA32 FA12 FA17 FA28 4D059 AA06 AA30 BE03 BE14 BE42 BE49 BF12 BJ09 CA24 CA28 CB08 CA14 EB17 DA04 DA05 DA04 FA17 FA28

Claims (3)

[Claims] Claims: 1. In the water treatment step, when extracting and concentrating sludge that has been coagulated and precipitated by adding an aluminum-based coagulant, the sludge is put into a concentration tank in which a separation membrane is immersed and installed, and a predetermined acid-side pH is set with an acid. A method for concentrating sludge, wherein the sludge is filtered by the separation membrane while being adjusted to an area, and the filtrate is concentrated by drawing it out of the tank. 2. The sludge concentration method according to claim 1, wherein the filtrate is injected into raw water flowing into the coagulation treatment facility. 3. A concentration tank into which sludge to which an aluminum-based flocculant has been added is charged, and a separation membrane immersed and installed in the tank.
A filtrate discharge system connected to the membrane permeation side of the separation membrane, a pH measuring means for measuring the pH of the sludge in the tank,
A chemical injecting means for injecting the H adjusting agent, and an amount of the pH adjusting agent to be injected by the chemical injecting means based on the pH measured by the pH measuring means, the amount being provided connected to the pH measuring means and the chemical injecting means; And a control device for controlling the sludge concentration.