JP2779321B2 - Filter cloth for pressure filtration and dewatering of sewage sludge and filter press using the filter cloth - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a sewage treated sludge which has been subjected to filtration and dehydration under pressure to form a dewatered cake by performing solid-liquid separation, and is mounted on an apparatus used for the filtration and dehydration. The present invention relates to a filter cloth having an improved structure for detaching the cake from the filter cloth, and a filter press using the filter cloth.

[0002] Here, the refining means a pretreatment for adjusting the concentration and dewatering conditions of sludge so as to improve the concentration and dewatering efficiency or the apparatus performance.

[0003]

2. Description of the Related Art Effective sewage treatment sludge refining technology is required to efficiently dewater and filter sewage treatment sludge under pressure.

In recent years, the content of organic matter in sludge has increased due to a shift to a sewerage system of sewerage, a change in lifestyle, and the like, and the concentration of concentrated sludge has been decreasing. For this reason, the deterioration of dehydration is progressing, and improvement of the sludge conditioning method is strongly desired.

[0005] Generally, sludge conditioning is performed by adding a flocculant, and as the flocculant, ferric chloride, a polymer flocculant, or the like has been used. Among them, a method of adding iron oxide chloride and slaked lime as a filter aid and tempering has been widely used because a cake having the lowest moisture content can be obtained.

However, due to the recent deterioration of sludge properties,
Even in the addition and adjustment of slaked lime, it was difficult to reduce the water content of the cake, and the cake was not smoothly separated from the filter cloth.

[0007]

SUMMARY OF THE INVENTION The present invention shows good cake peeling properties with respect to a cake formed by such a hardly dewaterable sewage treatment sludge, and is also capable of washing and removing fine particles deposited on the middle layer of the filter cloth. An object of the present invention is to provide a filter cloth which is easy, hardly causes clogging, and can be used continuously for a long time, and a filter press having a mechanism suitable for the cloth.

On the other hand, according to the above-mentioned method for refining sewage sludge, although dewatering by filtration is somewhat improved, slaked lime is added in an amount of 40 to 60% based on the suspended solids (SS) content of sludge. There is a need for a further improved sewage sludge conditioning process, coupled with the increased volume and incorporation of slaked lime which is difficult to handle due to dry powder.

[0009] As one method for this purpose, a method of treating sewage sludge by electrolysis treatment and dewatering the treated sludge (hereinafter referred to as electrolytic sludge) by a filter press was also performed. The cake amount is 6
It decreased to 0-70% amount. However, this electrolytic sludge has finer particles than the sludge conditioned by the conventional method and is hardly dewaterable, and the cake cannot be easily detached from the surface of the filter cloth by a normal filter cloth or filter cake peeling operation. is there.

Accordingly, an object of the present invention is to provide a cake formed by subjecting this electrolytic sludge to pressure filtration and dewatering, so that the cake can be easily peeled off, and fine particles containing iron deposited on the middle layer of the filter cloth can be easily removed by washing and clogging. It is an object of the present invention to provide a filter cloth having a filter cloth which is unlikely to cause the above problem and a mechanism adapted thereto.

[0011]

In order to achieve the above-mentioned object, the present invention relates to a method for producing a synthetic resin monofilament in which a warp covering the surface is composed of a yarn mainly composed of a synthetic resin multifilament yarn. A filter fabric for pressure filtration and dewatering of sewage sludge or the like, characterized in that the fabric is formed of a single yarn or a twisted yarn and has a structure that forms a smooth surface such as a plain weave, a weft woven weave, or a woven weave. Is what you do.

Since the surface of the filter cloth is covered with multifilaments and has a simple structure such as a plain weave and a fold-like surface and is highly smooth, the peeling of the cake and the cleaning of the filter cloth during the operation of the dehydrator can be performed very smoothly. On the other hand, the deposition of Fe (OH) ₃ in the weft voids composed of monofilaments is extremely small, and the progress of clogging is slow.

The texture of the tatami-like (tatami weave) surface referred to herein is a warp double weave as shown in FIG.
1) and the back warp (22) are entangled and formed at every intermediate position for every three wefts (23).

As the material of the warp and the weft constituting the filter cloth, polypropylene having excellent chemical resistance is suitable.

The thickness of the single filament of the multifilament of the warp constituting the filter cloth is preferably 5 to 35 denier in order to increase the trapping rate and reduce the leakage of filtration. When the denier is less than 5 denier, the surface of the yarn is easily fluffed, the fluff is formed on the surface of the filter cloth with the use of the filter cloth, the cake formed in the filter chamber is entangled with the fluff, and the peeling of the cake is deteriorated. If it is larger, the surface of the filter cloth is covered with thick fibers and has a rough surface, so that cake peeling is poor, and in any case, the filter cloth is clogged at an early stage.

Further, the present invention provides an apparatus for tempering sewage treated sludge with a coagulant such as ferric chloride and a filter aid added as required, and filtering and dewatering the tempered sludge under pressure.
Between many parallel filter plates, the warp covering the surface is composed of a yarn mainly composed of a synthetic resin multifilament yarn, and the weft in the middle layer is composed of a synthetic resin monofilament single yarn or twisted yarn. A filter cloth having a structure that forms a smooth surface such as a weft ridge weave or a tatami weave is hung freely, and the temper sludge is supplied between the filter cloths. It is an object of the present invention to provide a filter press characterized in that the cloth is caused to travel downward, and from the lower position, the filter cloths are driven in reverse so as to be separated from each other via rollers and discharged.

The refined sludge supplied to the filter press may be refined by electrolysis.

[0018]

The filter cloth according to the present invention is covered with multifilaments and has a simple structure such as a plain weave and a fold-like surface and is highly smooth. While it can be performed very smoothly, the deposition of Fe (OH) ₃ in the weft voids composed of monofilaments is extremely small, and the progress of clogging can be slowed.

In the following, the concept of the above-mentioned refining sludge refining method, in which the cake peeling operation is difficult and the filter cloth is likely to be clogged, the behavior of the filter cloth for the dewatering of the sludge, and the filter press peeling operation will be described.

Sewage sludge is a kind of aqueous electrolyte solution.
When a DC voltage is applied by inserting a pair of electrodes into this, positive ions of the electrolyte aqueous solution move to the cathode, and negative ions move to the anode, and current flows (FIG. 2). As a result, a chemical change occurs at the interface between the electrode surface and the sludge (FIG. 2A). In FIG. 2B, an iron material is used as the electrode material in consideration of the relationship with a later-described reforming accelerator.

First, an elution reaction of iron ions occurs from the anode.

[0022] ^{Fe → Fe 2+ + 2e - Fe} → Fe 3+ + 3e - Next, gas of chlorine and hydrogen generated by electrolysis.

2Cl− → Cl ₂ ↑ + 2e ⁻ (anodic reaction) 2H ⁺ → 2e ⁻ + H ₂ ↑ (cathodic reaction) The eluted iron ions form iron hydroxide by a hydration reaction.

Fe ²⁺ +2 (OH) − → Fe (OH) ₂ Fe ³⁺ +3 (OH) − → Fe (OH) _{3 The} produced iron hydroxide acts on the sludge to generate floc. In addition, an oxidation reaction by electric force and generated chlorine is expected.

Theoretically, sludge is reformed according to the above principle and concept. However, problems such as reforming efficiency, power consumption, deterioration of electrode function, etc. are involved. It becomes necessary to add an agent. Reforming performance, electrode function retention,
The ferric chloride is the most suitable in view of economy and the merit that the ferric chloride addition equipment which has been conventionally used can be diverted as it is.

The SS floc of the sludge conditioned in this manner is strong as the floc itself, but the formed particle mass is agglomerated with the conventional ferric chloride, which is then added to quicklime as a filter aid. Tend to be finer than the sludge particle mass that has been tempered. Therefore, the filter cake formed on the surface of the filter cloth tends to be compacted, has a high filtration resistance, is thin, has no rigidity, and tends to stick to the surface of the filter cloth.

Therefore, for the filtration and dewatering of the conditioned sludge,
In the subsequent filter cake discharging step, the cake is forcibly moved downward while being sandwiched between a pair of two filter cloths, and the pair of two filter cloths are driven at a lower end of the filter plate in a direction away from the cake. It must be operated so as to be forcibly separated from the filter cloth surface. The dewatering machine used for the filtration and dewatering of the sludge, if the surface structure of the filter medium is not made relatively dense, will result in extremely poor solids capture. Therefore, taking into account the situation of the cake discharge process, Japanese Patent Publication No. 55-38167. Gazette,
Japanese Patent Publication No. 51-42341, Japanese Utility Model Publication No. 54-2716
A single-type filter press to which a filter cloth or a filter cloth unit disclosed in Japanese Patent Publication No. 7 or the like is mounted is selected.

The operating condition of the filter cloth in the corresponding single type filter press will be described with reference to FIG.

A filter cloth (Ca, Cb) is set between a pair of filter plates (1a) and a squeezed filter plate (1b), and sludge (S) is put into a filter chamber (2) from a sludge feed port (F). Pressurized, the filtrate (FR) is discharged, and filtration proceeds. When pressurized water is fed into the diaphragm (D) after sludge injection, the cake (3) is squeezed and thinned.

After squeezing, the pair of filter plates (1a) and the squeezed filter plate (1b) are released from each other, and the filter cloth (Ca, Cb)
Is opened enough to separate the cake (3) and the filter cloth (Ca, Cb) is rolled by rollers (Ra, Rb).
And the cake (3) is forcibly separated from the filter cloth (Ca, Cb).
After the cake is peeled and discharged, the filter cloth (Ca, Cb) is washed from both sides thereof with a jet water stream (4).

As described above, the filter dewatered cake of the electrolyzed sludge is thin and highly sticky. Therefore, the surface of the filter cloth must have a simple structure and high smoothness. In other words, if the twill is made like a 2/2 twill weave, the cake will bite into the twill, and even if the cake is forcibly peeled, the bite will remain on the surface, and even if it is washed, it will not easily come off and clogging will proceed. .

On the other hand, the iron material used as an electrode is eluted as ferrous ions, most of which contributes to the coagulation of solids, but a part remains in the fibers of the filter cloth and becomes free from air during mechanical operation. Is oxidized by the contact of iron and solidifies and deposits as ferric hydroxide to promote clogging.

The filter cloth for pressure filtration and dewatering of the sewage sludge of the present invention examines the properties such as the floc state of the sludge particles and smoothes the separation and discharge of the filter cake formed by the filtration and pressing. Even if a small amount of cake remains on the surface, it is possible to easily wash off the remaining cake by washing with water during one cycle of the filtration operation, and furthermore, fine particle clumps and ferric hydroxide deposited inside the filter cloth The scale has a structure that can be easily decomposed and removed with dilute hydrochloric acid.

[0034]

EXAMPLES The structure and operation and effect of the filter cloth for pressurized dewatering of sewage sludge of the present invention will be described below based on the results of the above-mentioned electrolytic sludge filtration test performed on Examples and Comparative Examples.

The properties of the sludge subjected to the test, the conditioning conditions and the filtration and dewatering conditions are as shown in Tables 1, 2 and 3, respectively. In Table 1, TS is the solid concentration, SS
Represents the concentration of the suspended substance, and VTS represents the content of the organic substance.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

Table 4 shows the measurement results of the filtration performance.

[0040]

[Table 4]

Tables 5, 6 and 7 summarize the structures and performances of the filter cloths of Examples and Comparative Examples of the filter cloth for pressure filtration and dehydration of the present invention. In addition, in the column of "form of thread" in these tables, F represents a multifilament, M represents a monofilament, and F + M means a combination of both.

In Examples 1 to 4, only the structure of the filter cloth of Example 2 was a 3/1 double fold weave (FIG. 1), and all others were plain weaves. The fact that the warp is a combination of multifilament and monofilament, the weft is monofilament, and the material is polypropylene is common to all examples.
The thickness, density, thickness, and air permeability of the yarn were slightly changed.

In Comparative Examples 1 to 5, the material of the yarn was the same polypropylene as that of the example, but for comparison, the yarn shape, yarn thickness, density, thickness, air permeability, and texture were changed respectively. It is.

[0044]

[Table 5]

[0045]

[Table 6]

[0046]

[Table 7]

[0047]

As is evident from Tables 5, 6 and 7, all of Examples 1 to 4 of the present invention have a service life that is significantly longer than the service life of the filter cloth of each comparative example, and provide extremely smooth filtration.・ It can be seen that dehydration operation has become possible. This is because the cloth surface of the filter cloth of each embodiment is covered with multifilaments and has a simple structure such as a plain weave and a fold-like surface and is rich in smoothness. Can be carried out very smoothly, but the deposition of Fe (OH) ₃ in the weft voids composed of monofilaments is extremely small, and the progress of clogging is slowed down.

As described above, according to the present invention, the cake produced by the hardly dewaterable sewage treatment sludge exhibits good cake releasability, and the fine particles deposited on the middle layer of the filter cloth can be easily washed and removed. It is possible to provide a filter cloth which hardly causes clogging and can have a long continuous use time, and a filter press having a mechanism suitable for the cloth.

Although the above description has been made mainly on the electro-cleaning sludge belonging to the category in which cake peeling is difficult and clogging is likely to occur, the filter cloth (filter cloth) used in the present invention can be used for various conventional refining. Obviously, very advantageous results can be obtained even if the sludge is filtered and dewatered.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a fold-like structure in a warp direction.

FIG. 2 is an explanatory diagram of sludge treatment.

FIG. 3 is an explanatory view of a filter press.

[Explanation of symbols]

 Ca, Cb Filter cloth D Diaphragm S Sludge 1a Filter plate 1b Pressed filter plate 2 Filter chamber 3 Cake 4 Jet water flow 21 Warp 22 Warp 23 Weft

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁶ Identification code FI C02F 11/14 ZAB C02F 11/14 ZABB (56) References JP-A 4-57212 (JP, U) JP-A 63-94505 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) B01D 25/12 B01D 21/01 102 B01D 39/08 C02F 11/12 C02F 11/14

Claims (5)

(57) [Claims] 1. A filter cloth mounted on an apparatus for conditioning sewage sludge with a coagulant such as ferric chloride and a filter aid added as necessary, and filtering and dewatering the conditioned sludge under pressure. In, the warp covering the surface is composed of a yarn mainly composed of a synthetic resin multifilament yarn, the weft in the middle layer is composed of a synthetic resin monofilament single yarn or twisted yarn,
A filter cloth for pressure filtration and dewatering of sewage sludge and the like, wherein the cloth has a structure that forms a smooth surface such as a plain weave, a ridge weave, or a weave. 2. The filter cloth for pressure filtration and dewatering of sewage sludge and the like, wherein the material of the warp and the weft is polypropylene. 3. The multifilament single filament of the warp has a thickness of 5 to 35 denier.
Filter cloth for pressure filtration and dehydration of sewage sludge. 4. A sewage treatment sludge is conditioned by a coagulant such as ferric chloride and a filter aid added as required, and a plurality of filtration sewage sludges are filtered and dewatered in an apparatus. Between the plates, the warp covering the surface is composed of a yarn mainly composed of a synthetic resin multifilament yarn, and the weft in the middle layer is composed of a synthetic resin monofilament single yarn or twisted yarn, plain weave, weft ridge weave Or, a filter cloth having a structure forming a smooth surface such as a woven weave is hung freely, and the conditioned sludge is supplied between the filter cloths.
A filter press, wherein the filter cloth is driven downward so that the filter cloth is inverted from a lower position through rollers to be separated from each other and discharged. 5. The filter press according to claim 4, wherein said refining sludge is refined by electrolysis.