JP2001137898A - Method for sludge dehydration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for sludge dehydration for further reducing the percentage of water content in surplus sludge after a dehydration treatment step, and for reducing the load of drying or waste treatment in the subsequent processes. SOLUTION: A method for sludge dehydration for dehydrating sludge containing water and discharged as wastes by adding carbide to the sludge is proposed, where is a rotary drum type vacuum precoat type filtering device is used for the dehydration treatment, and carbide is used as a precoat agent of the device. In particular, the carbide having a desired grain diameter obtained by carbonizing the sludge dehydrated by the rotary drum type vacuum precoat type filtering device is used as the precoat agent of the device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sludge dewatering method, and more particularly to a sludge dewatering method suitable for dewatering sludge (excess sludge) discharged from a sewage treatment plant or a factory wastewater treatment plant.

[0002]

2. Description of the Related Art As a method of dewatering sludge such as excess sludge discharged from sewage treatment equipment or factory wastewater treatment equipment, sludge dehydration using a belt press or a centrifugal dehydrator is conventionally performed. According to this method, as shown in FIG. 5, the excess sludge A containing water discharged in the sewage treatment step S1 is added with the coagulant B and the carbonized sludge C as a dehydration aid in the mixing treatment step S2. As a result, a large floc is generated, and surplus sludge K which facilitates sedimentation and separation of the sludge solid content is obtained. This excess sludge K is dewatered by a device such as a belt press machine or a centrifugal dehydrator in a dewatering process step S3, further dried in a drying process step S4, and then carbonized in a carbonization process step S5. Is used as the above-described carbonized sludge C, and is mostly discharged outside the plant in the discharge processing step S6.

[0003] In order to purify sludge and blue ash of lakes and marshes, there is an example in which a rotary drum type vacuum precoat type filtration device using diatomaceous earth as a filter aid is used. As a precoating method of a filter aid in this type of apparatus, see JP-A-Hei 3
In the method described in JP-A-193107, first, fine particles are precoated by a pressure method, and then coarse particles are similarly precoated by a pressure method.

Further, a method in which sludge incineration ash is pre-coated by a filter press method as a filter aid is disclosed in
No. 257322.

[0005]

In the dewatering process of the belt press and the centrifugal dewatering machine used in the dewatering process step S3 in the prior art shown in FIG. 5, the water content of the excess sludge K is reduced only to the 80% level. I can't do that. Therefore, a large amount of energy is consumed in the drying process in the subsequent process, and the coagulant added to the excess sludge contains a large amount of metal such as aluminum and a large amount of polymer-based organic substances. This may cause soil contamination when it is reused, and this permeated filtrate is very dirty, that is, it is not sufficiently filtered and cannot be discharged directly to the outside, so it must be returned to the explosive tank. For this reason, there is a problem that additives and impurities are concentrated and the treatment efficiency in the activated sludge treatment equipment is reduced.

On the other hand, in the case of a rotary drum type vacuum precoat filtration device, diatomaceous earth used as a filter aid is expensive and hardly used from the viewpoint of running cost. Furthermore, when sludge carbide is used as the filter aid, fine particles adhere to the filter cloth first and cause clogging, thereby deteriorating the dewatering performance, or conversely, when coarse particles adhere to the filter cloth, the filtration surface becomes rough. Therefore, there is a problem that impurities in the wastewater cannot be captured by the filter cloth portion, and the filtration performance is reduced.

Accordingly, an object of the present invention is to provide a sludge dewatering treatment capable of further reducing the water content of excess sludge after the dewatering treatment step and reducing the burden of drying and waste treatment in the post-process. It is to provide a method.

Still another object of the present invention is to provide a sludge dewatering method capable of capturing impurities in wastewater in a dewatering step and having excellent filtration performance.

It is still another object of the present invention to provide a sludge dewatering method which requires a low running cost.

[0010]

A feature of the present invention to achieve the above object is to provide a sludge dewatering method for dewatering a sludge containing water discharged as waste by adding carbide to the sludge. A rotary drum type vacuum precoat type filtration device, and a carbide as a precoat agent of the device.

Another feature of the present invention that achieves the above object is a sludge dewatering method for dewatering a sludge containing water discharged as waste by adding carbide to the sludge. It is to use a carbide having a desired particle diameter obtained by subjecting sludge dewatered by a precoat filtration device to a carbonization treatment, as a precoat agent for the device.

Further, the carbide as a precoat agent in the rotary drum type vacuum precoat type filtration device has a particle diameter of 25 to 600 μm in diameter. An object of the present invention is to use as a body feed agent sludge containing water to be subjected to dehydration treatment by a filtration device.

Still another object of the present invention is to use a charcoal of organic waste such as coffee grounds, beer grounds, and rice husk as a precoating agent for a rotary drum type vacuum precoating type filtration device.

According to the present invention, it is possible to improve the dewatering property by using carbide for dewatering excess sludge, and to reduce the burden of drying treatment and waste treatment in the subsequent steps. According to the study of the present inventors, when a carbide is used as a precoat layer of a rotary drum type vacuum precoat type filtration device, dehydration of surplus sludge effectively proceeds, and particularly when the particle diameter (diameter) is 25 to 600 μm. It has been found that good dewatering / filtration can be carried out.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in FIG. FIG. 1 is a flow chart of a sludge dewatering method according to the present invention, in particular, a system for recycling the carbide (carbonized sludge H) of excess sludge A.

In FIG. 1, sewage treatment step S10
The excess sludge A obtained in (corresponding to the sewage treatment step S1 in FIG. 5) has a high water content of about 98 to 99%. In the subsequent mixing step S20 in the mixing tank, the carbonized sludge H obtained in the carbonizing step S50 described later is used as a precoat agent (carbonized sludge) E obtained by pulverizing and classifying in the pulverizing and classifying step S60. The excess sludge is mixed with the excess sludge A as a body feed agent (dehydration aid) C. For this reason, the solid content in the excess sludge A is increased, and the next dewatering treatment step S30
Is easy to separate solid-liquid, that is, surplus sludge D that can be easily filtered and dewatered. In addition, by using carbonized sludge as the body feed agent C, the odor of excess sludge A (which may be referred to as a filtration stock solution because it contains a large amount of water) is adsorbed and deodorized. It has the advantage of not only improving but also not bringing in complaints from the surroundings.

Next, in the dewatering step S30, the surplus sludge D is dewatered. This dehydration treatment is performed by the rotary drum type vacuum precoat type filtration device 100 shown in FIG.

Rotary drum type vacuum precoat type filtration device 1
The details of the structure and operation of the precoat layer 105 made of a precoat agent (carbonized sludge E) will be described later.
As shown in FIG. 2, a range of 25 to 600 μm suitable for carbonized sludge H as a pre-coating agent, and a range of 50 to 150 μm (= diameter; diameter is omitted hereafter) for higher efficiency. What has been pulverized and classified is used.

By the dewatering step S30, dewatered sludge F whose dewatering performance is improved and water content is reduced to at least about 70% as compared with the prior art is obtained as described later.

The dewatered sludge F is dried in the next drying step S
At 40, the dried sludge is dried by a suitable dryer to obtain dried sludge G having a reduced water content of about 15 to 30%, which is efficient for carbonization in the next carbonization step S50. Then, a carbonization treatment is performed by a suitable carbonization device (carbonization treatment step S50) to obtain a sludge carbide (carbonized sludge H).

The carbonized sludge H is reused as the above-mentioned precoating agent E and body feed agent C through the pulverizing / classifying step S60. The remaining carbonized sludge H is
It is appropriately discharged in the discharge processing step S70, but since no coagulant such as metal is added in the mixing processing step S20, it can be used as a compost for agriculture without any worry. No problem.

Next, the configuration of the rotary drum type vacuum precoat type filtration apparatus 100 and the precoat performance of the precoat layer 105 will be described. In FIG. 2, reference numeral 101 denotes a tank of a rotary drum type vacuum precoat type filtration apparatus 100 containing a stock solution for filtration (excess sludge D), 102 denotes a side plate of a rotary drum, 103 denotes a bearing portion of the rotary drum, and 104 denotes a filter cloth. The components 102 to 104 constitute a rotating drum. Reference numeral 105 denotes a precoat layer adhered onto the filter cloth 104; 107, a filter cake cake layer which is separated from the undiluted filtrate (excess sludge D) by filtration to become dehydrated sludge F fixed to the precoat layer 105; Of the cake cake layer 107 with the pre-coat layer 1
This is a scraper that is scraped off together with 05 to make dewatered sludge F.

A suction nozzle 106 is provided in the rotary drum through the bearing 103 to suction the inside of the drum.
Therefore, the undiluted filtrate (excess sludge D) in the tank 101 is filtered by the precoat layer 105, and the water is sucked into the rotating drum and discharged to the outside. At this time, the cake cake layer 107 is fixed on the precoat layer 105.

Rotary drum type vacuum precoat type filtration device 1
The precoat performance of the precoat layer 105 in 00 is (1) adhesion of the filter aid, (2) permeability of filter cake to the filter aid, and (3) machinability of the precoat layer. The details of the evaluation will be described below.

First, (1) the adhesion of a filter aid (carbide) is determined by the degree of operation vacuum, the filtration area and the concentration of the precoat liquid. The rotary drum of the rotary drum type vacuum precoat type filtration apparatus 100 is immersed in the lower half of the filtrate undiluted solution D stored in the tank 101, and a vacuum pump (not shown) installed from the inside of the rotary drum to the outside through the suction nozzle 106 It is structured to suck.

Rotary drum type vacuum precoat type filtration device 1
For use of 00, the part circled in FIG.
As shown in the enlarged view of FIG. 3A, a precoating liquid 110 containing a precoating agent is put into a tank 101, and through a suction nozzle 106 by vacuum suction, as shown in FIG. E is coated on the outer surface of the filter cloth 104 of the rotating drum with a precoat layer 105 having a thickness of about 50 to 100 mm.
Form as After the precoating is completed, the undiluted solution D is supplied to the tank 101, and the undiluted solution D is suction-filtered while rotating the rotating drum. As shown in FIG.
The filter cake is captured on the outer surface of the layer 105, and the cake cake layer 107 is fixed, and vacuum precoat filtration is performed.

With the rotation of the rotary drum, as shown in FIG. 2, a part of the precoat layer 105 is scraped together with the cake cake layer 107 by the scraper 108 to renew the precoat layer 105. That is, the undiluted solution is filtered at the lower part of the rotating drum,
The cake cake is dehydrated at the top.

It is important that the precoat layer 105 is formed by adhering to the filter cloth 104 on the outer surface of the drum of the rotary drum.
It was found that the precoat layer 105 attached to a thickness of about 00 mm was required, and the adhesion performance of the precoat layer 105 greatly varied depending on the particle diameter of the carbide as the precoat agent. Generally, as the particle size increases, the adhesion performance improves,
There is a range of particle sizes that can be used. In particular, for the smaller one, the filter cloth is clogged and the adhesion performance is reduced.

Next, as shown in FIG. 2, the rotary drum type vacuum precoat type filtration apparatus, which has the filter cake permeability of (2), forms sludge on the surface of the precoat layer 105 previously attached to the filter cloth 104 as shown in FIG. The cake cake layer 107 is firmly laminated by vacuum suction, and is scraped little by little with a scraper 108 together with a thin layer of the precoat layer 105 to obtain dehydrated sludge F.
The dewatered sludge F is obtained by updating the surface of the precoat layer 105 and continuing the above operations such as rotation of the rotary drum and vacuum suction for a certain period of time.

If the sludge filter cake penetrates deeply into the precoat layer 105 during filtration and dewatering, a clean precoat layer will not appear if the shaving method is thin.
Therefore, the thickness of the pre-coat layer 105 adhered to the pre-coat layer 105 becomes thinner in a short period of time, and the number of pre-coats increases. That is, filter cake permeability greatly affects the consumption of carbonized sludge (precoat layer) as a filter aid and the number of precoat batches. Therefore, the filter cake permeability is evaluated by the thickness at which the filter cake permeates the precoat layer during one rotation of the rotary drum.

Further, the machinability of the precoat layer 105, which is the filter aid of (3), is greatly affected by the particle size of the carbide constituting the precoat layer 105.
The smaller the particle diameter, the smoother the surface becomes and the pre-coat layer 10
5 can be thinned. Therefore, the machinability is evaluated based on the uniformity of the surface when the precoat layer 105 is shaved by the scraper 108. If the performance is as good as the filter cake permeability, the consumption of carbonized sludge, which is a filter aid, can be reduced, and the number of precoats is also reduced, resulting in a reduction in cost.

The three types of evaluation and confirmation items for the precoat performance were evaluated by experiments using the simulation test apparatus shown in FIG. 4 which simulated the outer surface of the rotary drum of the rotary drum type vacuum precoat filtration apparatus. In FIG. 4, a precoat liquid d is put in a container 1 corresponding to the tank 101 in FIG.
Vacuum suction is performed from above the simulation nozzle 6. A filter cloth 4 is inserted into the simulation nozzle 6, and carbonized sludge as a precoat agent is laminated on the filter cloth 4. Vacuum suction is applied to the separator 2
0, and is implemented by a vacuum pump 30 through a rotary drum type vacuum precoat filtration device 100.
Can be evaluated for precoating performance and dewatering performance.

Table 1 shows examples of the precoating characteristics of carbonized sludge performed using this method.

[0034]

[Table 1]

As is apparent from Table 1, 50 to 150 μm
When only the particle diameter of m is used, all of the adhesiveness, filter cake permeability and machinability are good. In the particle diameter ranges of 25 to 50 μm and 150 to 600 μm, the performance is slightly reduced, but it can be used. Therefore, carbonized sludge having a particle size range of 25 to 600 μm can be used.

Here, the adhesion was 30 mm or more in one minute for the first precoat layer, 1 mm or less for bad, and intermediate for good. Next, regarding the filter cake permeability, 300 μm or less was excellent, 600 μm or more was not good, and the middle was good because of the amount of impurities transmitted. Furthermore, regarding the machinability,
The surface was visually checked to see if it had been sharply cut, and excellent or good was determined.

Next, Table 2 shows an example of the dehydration performance similarly obtained by the experiment using the apparatus shown in FIG.

[0038]

[Table 2]

According to the sludge dewatering method of the present invention, Table 2
As shown in the figure, the water content indicating the dewatering performance of the excess sludge was about 80% in the conventional belt press method, which was about 80%.
To a degree. This means that the amount of water contained in the excess sludge is reduced by about 40%, and that when the excess sludge is disposed of as waste, the weight is reduced by about 30%.

It was also confirmed that the amount of suspended solids in the permeate filtrate discharged to the outside through the suction nozzle 106 exhibiting filtration performance can be reduced from several hundred PPM in the conventional method to several tens of PPM. This means that the suction nozzle 1
This indicates that there is an effect that the permeated filtrate discharged to the outside through 06 can be directly discharged to the outside without returning to the detonation tank as return water. As described above, the impurities in the wastewater can be trapped in the dewatering step, so that a sludge dewatering method excellent in filtration performance can be provided.

As described above, in the sludge dewatering treatment system of the present invention, the sludge waste is carbonized and recycled.
Recycling and volume reduction can be achieved, and thus running costs can be reduced. Furthermore, sludge waste is pure organic matter and can be reused as good compost and as a soil conditioner. Moreover, since the sludge carbide has the effect of humidity control and adsorption performance as a carbonization product, it also has the effect of improving the deodorizing effect of sludge and improving the working environment around the dewatering device.

The present invention may be modified as follows in addition to the above embodiment. (1) The carbides mentioned here are not limited to sludge carbides.
It can also be used for charcoal of organic waste such as arbor, beer lees, and rice husk. (2) The sludge carbide used in the present invention may be brought in from outside instead of from inside the treatment system. (3) The entire amount of the dried sludge G may be carbonized, or a portion thereof may be carbonized.

[0043]

As described above, according to the sludge dewatering method of the present invention, it is possible to further reduce the water content of the excess sludge after the dewatering step, and to perform drying and waste treatment in the post-process. The burden can be reduced.

Further, it is possible to provide a sludge dewatering method which can capture impurities in the wastewater in the dewatering step and has excellent filtration performance. Further, it is possible to provide a sludge dewatering method that requires a low running cost.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a sludge dewatering process according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a rotary drum type vacuum precoat type filtration device used in the sludge dewatering treatment of the present invention shown in FIG.

FIG. 3 is a view for explaining precoating of a filter aid and vacuum precoat filtration in the rotary drum type vacuum precoat filtration apparatus shown in FIG. 2;

FIG. 4 is a view showing a configuration of a simulation test facility used for examining a filter aid in the rotary drum type vacuum precoat type filtration device shown in FIG. 2;

FIG. 5 is a flowchart of a conventional sludge dewatering process.

[Explanation of symbols]

100: rotary drum type vacuum precoat type filtration device, 10
1: tank, 104: filter cloth, 105: pre-coat layer, 1
06: suction nozzle, 107: cake cake layer, 108: scraper, D: undiluted filtrate (excess sludge)

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Takayoshi Koyanagi 2-9-7 Ikenohata, Taito-ku, Tokyo F-term in Engineering Engineering Division, Hitachi Techno Engineering Co., Ltd. 4D026 BA03 BB03 BC24 BC26 BC29 BD02 BD05 BE05 BF11 BF21 4D059 AA05 BB05 BE11 BE14 BE21 BE62 BK02 CB18 CC05 DA70 4D066 BA01 CA05

Claims (4)

[Claims] 1. A sludge dewatering method for dewatering a sludge containing water discharged as waste by adding a carbide to the sludge, wherein a rotary drum type vacuum precoat type filtration device is used for the dehydration process, and a precoat agent for the filtration device is used. A sludge dewatering method characterized by using a carbide for the sludge. 2. The sludge dewatering method according to claim 1, wherein the sludge dewatered by the rotary drum type vacuum precoat type filtration device is carbonized to obtain a carbide having a desired particle diameter. A sludge dewatering method characterized by being used as a precoat agent. 3. The sludge dewatering method according to claim 1 or 2, wherein the carbide as a precoat agent of the rotary drum type vacuum precoat type filtration device has a particle diameter of 25 to 600 μm in diameter. Sludge dewatering method characterized in that particles having a particle diameter outside this range are used as a body feed agent for water-containing sludge to be dewatered by the rotary drum type vacuum precoat type filtration device. 4. The sludge dewatering method according to claim 1 or 3, wherein a charcoal of organic waste is used as a precoat agent in the rotary drum type vacuum precoat type filtration device. Sludge dewatering method.