JP3260257B2 - Sludge dewatering method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dewatering sludge generated in a water purification system, a sewage system or the like.

[0002]

2. Description of the Related Art Conventionally, sedimentation sludge and biologically treated sludge (such as activated sludge) are generated in a water purification treatment facility or a sewage treatment facility during a treatment process. The sludge is concentrated, dehydrated, and dried before being incinerated or landfilled. There are various forms of sludge concentration and dewatering methods, and in order to perform each treatment economically, a pretreatment or refining operation is performed to improve the properties of the sludge. Examples of the pretreatment and the refining operation include washing with water to reduce the alkalinity and chemical coagulation for coagulating fine solid particles.

[0003] Coagulants used for chemical cohesion include inorganic coagulants and polymer coagulants. When a polymer coagulant is used, only a small amount of coagulant is required, the sedimentation speed is high, and flocs are hard. There are advantages. As a polymer flocculant, a cationic flocculant is effective, but in order to enhance the effect, it is often used in combination with an anionic flocculant rather than alone.

[0004]

When the above-mentioned flocculant is used, if a cationic polymer is added to the sludge to completely neutralize the anionic groups on the sludge particle surface with the cationic polymer, the loss in the reaction process is lost. In consideration of the above, it is necessary to add the cationic polymer slightly more than necessary. If the amount of the cationic polymer is too large, the flocs flocculated are re-dispersed. For this purpose, an appropriate amount of an anionic polymer is added to the sludge to coagulate the redispersed sludge. However, it is difficult to adjust the addition amount of the anionic polymer to an appropriate amount, and there is a problem that when the addition amount of the anion polymer is excessive, the dehydration performance in a subsequent dehydration step is significantly reduced. As described above, when both cationic and anionic coagulants are used, there is a problem that the apparatus configuration is complicated and that adjustment and control of the addition amount are difficult.

The present invention solves the above-mentioned problems, and
An object of the present invention is to provide a sludge dewatering method that does not require the addition of an anionic polymer and can simplify the device configuration.

[0006]

In order to solve the above-mentioned problems, a method for dewatering sludge according to the present invention comprises introducing sludge from a sludge storage tank to a primary coagulation mixing tank, and adding an appropriate amount of a cationic coagulant. And perform rapid agitation, and the suspended solids in the sludge have
In addition to neutralizing the charge of the anion , it promotes the formation of flocs, guides the flocculated sludge from the primary flocculation and mixing tank to the secondary flocculation and mixing tank, and adds an appropriate amount of unadjusted sludge from the sludge storage tank. In a newly added unadjusted sludge with rapid stirring
Of cationic charge in coagulated sludge by anion content
In addition to flocculation , flocculation of the coagulated sludge is further promoted , and the coagulated sludge in the secondary coagulation mixing tank is guided to a dehydrator to perform a dewatering treatment.

[0007]

According to the above construction, in the primary flocculation mixing tank, charge neutralization of the hydrophilic anion groups of the suspended matter in the sludge is achieved by the added cationic flocculant. At this time, the frequency of contact between the cationic coagulant and the suspended substance is increased by rapid stirring, so that flocking can be promoted together with charge neutralization. The addition amount of the cationic coagulant in the primary coagulation mixing tank is slightly more than necessary to completely neutralize the anionic groups of the suspended substances in the concentrated sludge. For this reason, at the end of the charge neutralization reaction process, the surface of some suspended matter forming the flocs is charged with cations, and the aggregated flocs are redispersed to reduce the diameter of the flocs.

[0008] In the secondary flocculation and mixing tank, the anions contained in the newly added unadjusted sludge neutralize the charged cation-suspended substances and neutralize the flocs while slowly stirring. Combine to form coarse flocs. The dewatering efficiency of the dewatering machine is improved by dewatering the flocculated sludge containing the coarse flocs in the secondary flocculation mixing tank in the dewatering machine.

Therefore, it is not necessary to separately add an anionic coagulant as a medicine, which reduces running costs and simplifies the apparatus configuration.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a sludge storage tank 1 has a stirrer 2 and an undiluted solution supply pipe 3 is open. Sludge generated in a water purification facility or a sewage treatment facility is supplied through the stock solution supply pipe 3. The sludge storage tank 1 communicates with a primary flocculation mixing tank 5 through a mud pipe 4, and the primary flocculation mixing tank 5 includes a rapid stirrer 6. The primary flocculation mixing tank 5 communicates with a high molecular polymer storage tank 7 serving as a cationic flocculant. The primary flocculation mixing tank 5 is in communication with the secondary flocculation mixing tank 8, and the secondary flocculation mixing tank 8 includes a slow stirrer 9.
In the secondary flocculation / mixing tank 8, the adjusting sludge supply pipe 1 whose base end communicates with the sludge feeding pipe 4 between the sludge storage tank 1 and the primary flocculation / mixing tank 5.
0 is open, and the secondary coagulation mixing tank 8 communicates with the dehydrator 11. As the dehydrator 11, a centrifugal dehydrator, a belt press, a filter press, a screw press, or the like can be used.

The operation of the above configuration will be described below. In the sludge storage tank 1, the sludge flowing from the stock solution supply pipe 3 is stirred and homogenized by the stirrer 2, and the sludge is led to the primary flocculation mixing tank 5 at a constant flow rate through the sludge pipe 4.

In the primary flocculation and mixing tank 5, an appropriate amount of a cationic flocculant such as a cationic polymer is added to the sludge from the storage tank 7, and the mixture is rapidly stirred by the rapid stirrer 6. In the primary flocculation mixing tank 5, the cationic flocculant neutralizes the charge of the hydrophilic anion group of the suspended substance in the sludge and forms a floc. At this time, the contact efficiency between the cationic coagulant and the suspended substance is increased by rapid stirring, so that flocking can be promoted together with charge neutralization. The amount of the cationic coagulant added in the primary coagulation mixing tank 5 is slightly more than necessary to completely neutralize the anionic groups of the suspended substances in the concentrated sludge. For this reason, at the end of the charge neutralization reaction process, the surface of some suspended matter forming the flocs is charged with cations, and the aggregated flocs are redispersed to reduce the diameter of the flocs. The flocculated sludge in the primary flocculation mixing tank 5 is guided to the secondary flocculation mixing tank 8.

In the secondary flocculation and mixing tank 8, an appropriate amount of unregulated sludge (3 to 20% of the target sludge) supplied through the sludge supply pipe 10 for adjustment is added to the flocculated sludge and slowly stirred. In the secondary flocculation / mixing tank 8, the anions contained in the newly added unadjusted sludge neutralize the charged cation-suspended substances and neutralize the flocs while stirring slowly. To form coarse flocs by reaggregation. The adjustment of the amount of anions to be supplied as unadjusted sludge can be performed by controlling the discharge amount of a pump constituting the pipe system and the like. Then, the coagulated sludge in the secondary coagulation mixing tank 8 containing coarse flocs is dewatered in the dehydrator 11.

When 2% of the cationic polymer was added to 500 ml of a certain type of sludge, the floc diameter was 1 mm or less. However, when 2% of the cationic polymer was added to 450 ml of the same sludge, and then 50 ml of the sludge was further added, the floc diameter became 3 to 4 mm.

[0015]

As described above, according to the present invention, an appropriate amount of unadjusted sludge is supplied as an anion agent to the coagulated sludge in the secondary coagulation mixing tank, so that an anionic coagulant is separately provided as a chemical. Is unnecessary, the running cost is reduced, and the device configuration can be simplified.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a sludge dewatering step in one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sludge storage tank 5 Primary coagulation mixing tank 6 Rapid stirrer 7 Storage tank 8 Secondary coagulation mixing tank 9 Slow stirrer 10 Sludge supply pipe for adjustment 11 Dehydrator

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-183808 (JP, A) JP-A-57-130600 (JP, A) JP-A-54-44269 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C02F 11/14 ZAB

Claims (1)

(57) [Claims] 1. Sludge from a sludge storage tank is introduced into a primary flocculation mixing tank, an appropriate amount of a cationic flocculant is added thereto, and the mixture is stirred rapidly to neutralize the anion charge of the suspended substance in the sludge. At the same time, the formation of flocs is promoted, the flocculated sludge in the primary flocculation mixing tank is led to the secondary flocculation mixing tank, and an appropriate amount of unadjusted sludge guided from the sludge storage tank is added, and the mixture is slowly stirred and newly added. Depending on the anion content of the unconditioned sludge added
A method for dewatering sludge, which comprises neutralizing cationic charges in flocculated sludge, further promoting flocculation of flocculated sludge, and conducting dewatering treatment by introducing flocculated sludge in a secondary flocculation mixing tank to a dehydrator.