JP2001062496A - Sludge concentrating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the concentration of concentrated sludge and the recovery of a solid material and to keep stable flux by treating the sludge with one process of acid-alkali treatment, ozone treatment and ultrasonic treatment as a pretreatment in the concentration of the sludge generated from a water treating system. SOLUTION: The sludge generated in the water treating system is introduced into an acid.alkali treating vessel 2 from a sludge introducing pipe 1 and is pretreated and reformed by adding a prescribed chemical from a chemical supply pipe 3. The sludge is introduced into a membrane concentration vessel 4 and concentrated by drawing membrane permeated liquid through a membrane permeated liquid drawing pipe 7 while impressing negative pressure to a membrane unit 5 dipped in the vessel by a membrane permeated liquid drawing pump 6. Air is supplied to a diffusion pipe 8 arranged at the lower part of the membrane unit 5 from a blower 9 to suppress the clogging of the membrane and to obtain the stable flux. The concentrated sludge is transferred to a sludge treating facility of a post process from a concentrated sludge flow-out pipe 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for concentrating sludge generated in the treatment of sewage such as sewage, human waste and industrial wastewater.

[0002]

2. Description of the Related Art Conventionally, sludge concentration methods include a gravity concentration method, a centrifugal concentration method, a pressure flotation concentration method, a normal pressure flotation concentration method, and a granulation concentration method. It is running. However, the former three have a poor solids recovery rate, and the latter have a high concentration of concentrated sludge and the solids recovery rate is generally satisfactory. Agents and amphoteric polymers must be used together. Also,
In the concentration method using a membrane, the viscosity increases with an increase in the concentration of the concentrated sludge, the flux decreases, and the frequency of cleaning the membrane increases, which is problematic in practical use. In the conventional concentrated sludge method, the concentration of the concentrated sludge has been targeted at approximately 4%, except for the gravity type concentration method.

[0003]

In view of the above, the present invention aims at a concentrated sludge concentration of 4% or more, preferably 5% or more, and a solids recovery rate of 95% or more, and preferably 98% or more. In order to improve the concentrated sludge concentration and solids recovery rate in membrane filtration concentration, centrifugal concentration and gravity concentration by sludge reforming, especially in the method of membrane filtration concentration, there is no need to use a flocculant. It is an object of the present invention to provide a sludge concentration method capable of maintaining a stable flux at all times.

[0004]

Means for Solving the Problems In order to solve the above-mentioned problems, a method for concentrating sludge according to the present invention according to claim 1 is a method for concentrating sludge generated from a water treatment system with an enrichment device, wherein acid and sulfur are pretreated. Sludge is treated in at least one of an alkali treatment, an ozone treatment, and an ultrasonic treatment.

[0005] The method for concentrating sludge of the present invention according to claim 2 comprises:
As the concentrator, at least one of a membrane concentrator having a microfiltration membrane or an ultrafiltration membrane, a centrifugal concentrator, and a gravity concentrator is used. With the above configuration, sludge generated in the water treatment system includes primary sludge and surplus activated sludge, and surplus activated sludge is particularly poor in concentrating property, and the viscosity increases as the concentrating concentration increases. This is thought to be largely due to the gelatinous mucous membrane covering the surface of the microorganism. Therefore, by oxidizing and decomposing sludge prior to concentration, it reduces the molecular weight and viscosity of gelatinous mucosa, which is a complex polysaccharide substance, and decomposes and solubilizes fine particles in sludge. In addition, the concentration limit of the concentrated sludge can be raised.

For this reason, primary sludge, surplus activated sludge and a mixed sludge thereof are subjected to acid / alkali treatment, ozone treatment,
It is modified by ultrasonic treatment or a combination thereof. Sludge reduced in molecular weight, reduced in viscosity, and easily concentrated by this reforming can maintain and secure a stable flux in membrane filtration and concentration. In addition, a high concentrated sludge concentration can be obtained without adding a flocculant in a centrifugal concentrator, and a high solids recovery rate can be obtained because the SS concentration in the separated liquid is low. Furthermore, in the two-stage concentration equipment combining the gravity concentrator and the membrane filtration concentration, the solid matter having excellent sedimentation is concentrated at the bottom of the tank, the SS concentration in the separated liquid decreases, and the sludge concentrated by gravity concentration Is further concentrated by membrane filtration concentration, so that a concentrated sludge concentration equal to or higher than that of centrifugal concentration can be obtained.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, sludge generated in a water treatment system as sludge to be treated is passed through a sludge inflow pipe 1 to form an acid.
It is received in the alkali treatment tank 2 and pretreated to reform sludge. In the acid / alkali treatment tank 2, a predetermined amount of an acid solution and an alkali solution are added to the sludge from the chemical supply pipe 3, and the gelatinous polysaccharide substance covering the surface layer of the sludge is oxidized and decomposed to reduce the molecular weight and the molecular weight. Viscous.

The easily concentrated sludge is introduced into a membrane thickening tank 4. In the membrane concentration tank 4, a negative pressure is applied to the membrane unit 5 immersed in the tank by a membrane permeate extraction pump 6, and the membrane permeate having passed through the membrane is withdrawn through a membrane permeate extraction pipe 7 to remove sludge. Concentrate to more than%. At this time, the sludge has been reduced in molecular weight, reduced in viscosity, and easily concentrated by reforming, so that a stable flux can be maintained and secured in membrane filtration and concentration.

In addition, air is supplied from a blower 9 to an air diffuser 8 disposed below the membrane unit 5 and is constantly or intermittently aerated to generate an upward flow. This upward flow acts as a sweep on the membrane surface, thereby suppressing clogging of the membrane and obtaining a stable flux. The concentrated sludge is sent through a concentrated sludge outflow pipe 10 to a sludge treatment facility in a subsequent process. In FIG. 2, the sludge to be treated is received in an ozone reactor 11 through a sludge inflow pipe 1 and pretreated to reform the sludge. In the ozone reaction tank 11, ozonized air is supplied from an ozone generator 13 to an air diffuser 12 disposed in the tank, and 0.03 is supplied into the tank.
1~0.02g-O ₃ / g-SS about blowing the amount of ozone. Ozone oxidizes and decomposes a gelatinous polysaccharide substance covering the surface layer of sludge to lower the molecular weight and lower the viscosity. The easily concentrated sludge is concentrated to 5% or more in the membrane concentration tank 4.

In FIG. 3, the sludge to be treated is a sludge inflow pipe l.
Through the ultrasonic treatment tank 14 and pre-treated to reform sludge. In the ultrasonic treatment tank 14, the ultrasonic generator 1
By irradiating the ultrasonic wave generated in 5 to the sludge for a predetermined time, the surface layer of the sludge covered with the gelatinous substance is destroyed to reduce the molecular weight and the viscosity. The easily concentrated sludge is concentrated in the membrane concentration tank 4 to 5% or more.

In FIG. 4, the sludge to be treated is a sludge inflow pipe l.
To the ozone reactor 11 for pretreatment to reform sludge. In the ozone reaction tank 11, ozonized air is supplied from the ozone generator 13 to the air diffuser 12 disposed in the tank, and an ozone amount of about 0.01 to 0.02 g-O ₃ / g-SS is blown into the tank. . Ozone oxidizes and decomposes a gelatinous polysaccharide substance covering the surface layer of sludge to reduce the molecular weight and viscosity.

The easily concentrated sludge is centrifuged by a centrifugal concentrator 1
6 to obtain a concentrated sludge having a high concentration and a separated liquid having a low SS concentration by performing solid-liquid separation. In this case, since the ozone treatment is performed as a pretreatment, the predetermined concentrated sludge concentration and the SS concentration can be obtained without adding a flocculant and with a lower centrifugal effect than usual (usually 1000 G, 800 G in the present invention). , And the energy consumption can be reduced. The centrifugally concentrated sludge is sent to a sludge treatment facility in a subsequent process through a concentrated sludge discharge pipe 17, and the separated liquid is returned to a water treatment system through a difficult liquid discharge pipe 18.

In FIG. 5, the sludge to be treated is a sludge inflow pipe l.
And then ozone is blown into the reactor to oxidize and decompose the gelatinous polysaccharide material covering the surface layer of the sludge, reforming it by reducing its molecular weight and viscosity, and pretreating it. This easily thickened sludge is transferred to a gravity thickening tank 19.
To In the gravity concentration tank 19, by rotating the picket fence 21 linked to the driving device 20, sediment that tends to settle is settled and concentrated at the bottom of the tank, and the separated liquid is returned to the water treatment system via the separated liquid discharge pipe 22. I do.

The sludge concentrated in the gravity concentration tank 19 is withdrawn from the bottom of the tank by a concentrated sludge withdrawing pump 23 and put into the membrane concentration tank 4. In the membrane concentrating tank 4, a negative pressure is applied to the membrane unit 5 immersed in the tank by the membrane permeating liquid extracting pump 6, and the membrane permeating liquid having permeated the membrane is drawn through the membrane permeating liquid extraction pipe 7, whereby the sludge concentration concentration is increased. Enhance. At this time, the sludge has been reduced in molecular weight, reduced in viscosity, and easily concentrated by reforming, so that a stable flux can be maintained and secured in membrane filtration and concentration.

In addition, air is supplied from a blower 9 to an air diffuser 8 disposed below the membrane unit 5 and is constantly or intermittently aerated to generate an upward flow. This upward flow acts as a sweep on the membrane surface, thereby suppressing clogging of the membrane and obtaining a stable flux. The concentrated sludge is sent through a concentrated sludge outlet pipe 10 to a sludge treatment facility in a subsequent process. Thus, the two-stage concentration of gravity concentration and membrane filtration concentration makes 5
% Sludge is reliably obtained.

[0016]

As described above, according to the present invention, the sludge generated in the water treatment system is reformed to have a low molecular weight, a low viscosity, and a high concentration by pretreatment, thereby improving the concentration of the sludge. The concentration of the concentrated sludge can be increased, and the dewatering performance can be improved, the solids recovery rate can be improved, the coagulant addition rate can be reduced, the number of dehydrator facilities can be reduced, or the operating time of the dehydrator can be shortened.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing a sludge concentration method for performing acid / alkali treatment and membrane concentration in an embodiment of the present invention.

FIG. 2 is a flow sheet showing a sludge concentration method for performing ozone treatment and membrane concentration in another embodiment of the present invention.

FIG. 3 is a flow sheet showing a sludge concentration method for performing ultrasonic treatment and membrane concentration in another embodiment of the present invention.

FIG. 4 is a flow sheet showing a sludge concentration method for performing ozone treatment and centrifugal concentration in another embodiment of the present invention.

FIG. 5 is a flow sheet showing a sludge concentration method for performing ozone treatment, gravity concentration, and centrifugal concentration in another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sludge inflow pipe 2 Acid / alkali treatment tank 3 Chemical supply pipe 4 Membrane concentration tank 5 Membrane unit 6 Membrane permeate extraction pump 7 Membrane permeate take-out pipe 8 Air diffuser 9 Blower 10 Concentrated sludge outflow pipe

Continued on the front page (72) Inventor Tomoko Fujita 2-47, Shizitsuhigashi, 1-chome, Namiwa-ku, Osaka-shi, Osaka F-term (reference) 4D059 AA01 AA03 AA07 BC02 BE13 BE19 BE42 BK22 DA01 DA02 DA31 DA43

Claims (2)

[Claims] When the sludge generated from a water treatment system is concentrated by a concentration device, the sludge is treated in at least one of an acid / alkali treatment, an ozone treatment, and an ultrasonic treatment as a pretreatment. Sludge concentration method. 2. The sludge concentrator according to claim 1, wherein at least one of a membrane concentrator having a microfiltration membrane or an ultrafiltration membrane, a centrifugal concentrator, and a gravity concentrator is used as the concentrator. Method.