JP6838404B2 - Sludge dewatering agent and sludge dewatering method - Google Patents

Description

The present invention mainly relates to a sludge dewatering agent and a sludge dewatering method suitable for dewatering excess sludge generated in civil engineering / construction work such as dredging work, boring work, pile work, underground continuous wall work, and shield work. , Specifically, using a low molecular weight anionic organic polymer flocculant, or a low molecular weight anionic organic polymer flocculant and a general-purpose inorganic flocculant and / or a cationic organic polymer flocculant, a low water content. The present invention relates to a sludge dewatering agent and a sludge dewatering method for efficiently obtaining a dewatered cake.
The present invention is not limited to the excess sludge generated in the above-mentioned civil engineering / construction work, but is generated in the treatment of sewage, urine, steel wastewater, pulp and paper wastewater, food factory wastewater, automobile factory wastewater, petrochemical factory wastewater, and machine factory wastewater. It is also applicable to sludge.

Polyaluminum chloride (PAC), an inorganic flocculant, is applied as a dehydrating agent to dehydrate excess sludge generated in civil engineering and construction works such as dredging work, boring work, pile work, underground continuous wall work, and shield work. Often.
When PAC is added to sludge, it forms aluminum hydroxide in water and exhibits a dehydrating action by forming fine flocs while entraining suspended substances in sludge.
However, there is a limit to the effect of improving dehydration by PAC, and even if a certain amount or more is added, the dehydration of sludge is not further improved.
This is because the isoelectric point (optimal pH value) of aluminum hydroxide formed by PAC is around pH 5.8, but when a certain amount or more of PAC is added, the pH of the acidic PAC itself exceeds the appropriate pH range. Therefore, it is not possible to expect a further improvement effect on dehydration.
Therefore, the application of PAC is inappropriate for sludge whose dehydration property cannot be expected to be improved by adding a small amount of PAC.

Patent Document 1 proposes a method of adding an anionic organic polymer flocculant, or an anionic polymer flocculant and a cationic organic flocculant as a dehydrating agent to sludge generated in civil engineering work together with an inorganic flocculant. Has been done. In Patent Document 1, it is preferable that the anionic organic polymer flocculant has a molecular weight of 10 million or more and an intrinsic viscosity of 15 dl / g or more, and in Examples, an anionic organic polymer flocculant having a molecular weight of 15 million or more is used.

Patent Document 2 proposes a method of adding an anionic organic polymer flocculant as a dehydrating agent in the first stage and a cationic organic polymer flocculant in the second stage to sludge generated in civil engineering work. Since each organic polymer flocculant used in Patent Document 2 has a dissolution concentration of about 0.2 to 1.0%, it is in the form of a powder having a molecular weight of about 10 million and an intrinsic viscosity of about 15 dl / g. It is presumed that an organic polymer flocculant is applied.

As described above, the organic polymer flocculants used in Patent Documents 1 and 2 have a molecular weight of about 10 million and an intrinsic viscosity of about 15 dl / g, and thus have a general concentration of 0.1 to 0.2. Even if it is dissolved in%, the obtained polymer solution has high viscosity, so there are the following problems.
(1) Increases the viscosity of sludge itself and worsens drainage.
(2) As the viscosity increases, the reaction rate with the suspended substance particles in the sludge slows down, and the cohesiveness of the suspended substance deteriorates.
(3) Due to (1) and (2), poor dehydration occurs, and a sufficiently dehydrated dehydrated cake cannot be obtained.

Japanese Unexamined Patent Publication No. 10-272306 Japanese Unexamined Patent Publication No. 2008-114142

The dehydrated cake obtained by the dehydration treatment is often disposed of as industrial waste, and when dehydration failure occurs, water remains in the dehydrated cake, and the amount of the dehydrated cake to be treated as industrial waste increases. In other words, since industrial waste costs are high, a dehydration method that reduces the water content of the dehydrated cake is required.

In addition, among the dehydrators, the filter press is an efficient dehydrating means because the water content of the obtained dehydrated cake is very low, but since it is performed in batch, the dehydration processing speed is higher than that of the continuous dehydrator. Inferior. Therefore, since the dehydration treatment may become the rate-determining factor for civil engineering work due to the poor dehydration treatment, it is also required to improve the filtration speed in the dehydration treatment by the filter press.

However, as described above, the conventional dehydration methods such as Patent Documents 1 and 2 cannot satisfy the above-mentioned required characteristics.

The present invention overcomes the problems of the prior art, and can obtain a dewatering effect higher than that of the prior art even for sludge generated in general civil engineering work and other refractory sludge, and the obtained dehydrated cake. It is an object of the present invention to provide a sludge dewatering agent and a sludge dewatering method capable of further reducing the water content of the sludge and improving the filtration rate.

As a result of diligent studies to solve the above problems, the present inventor uses a low molecular weight anionic organic polymer flocculant having an intrinsic viscosity of 3 dl / g or less, preferably an inorganic flocculant and / or a cation. It was found that even poorly dehydrating sludge can be efficiently dehydrated by using it in combination with an organic polymer flocculant, and the present invention has been reached.
That is, the gist of the present invention is as follows.

[1] Excess sludge generated in civil engineering and construction work, or sludge generated in the treatment of sewage, rabbit urine, steel wastewater, paper and pulp wastewater, food factory wastewater, automobile factory wastewater, petrochemical factory wastewater, and machine factory wastewater. A sludge drainage agent containing an anionic organic polymer flocculant having an intrinsic viscosity of 3 dl / g or less.

[2] The sludge dehydrating agent according to [1], which comprises the anionic organic polymer flocculant and an inorganic flocculant and / or a cationic organic polymer flocculant.

[3] The sludge dehydrating agent according to [1] or [2], which contains the anionic organic polymer flocculant as an aqueous solution having a dissolution concentration of 10% by weight or more.

[4] The sludge dehydrating agent according to any one of [1] to [3], wherein the sludge is a poorly dehydrating sludge having a CST / ds value of 50 sec /% or more.

[5] Unique to excess sludge generated in civil engineering and construction work, or sludge generated in the treatment of sewage, rabbit urine, steel effluent, paper and pulp effluent, food factory effluent, automobile factory effluent, petrochemical factory effluent, and machine factory effluent. A sludge dewatering method in which an anionic organic polymer flocculant having a viscosity of 3 dl / g or less is added to perform coagulation treatment and then dehydration treatment.

[6] After adding the anionic organic polymer flocculant to the sludge for coagulation treatment, an inorganic coagulant and / or a cationic organic polymer flocculant is added for coagulation treatment, and then dehydration treatment is performed [5]. The sludge dewatering method described in.

[7] The sludge dewatering method according to [5] or [6], wherein the anionic organic polymer flocculant is added as an aqueous solution having a dissolution concentration of 10% by weight or more.

[8] The sludge dewatering method according to any one of [5] to [7], wherein the sludge is a poorly dehydrating sludge having a CST / ds value of 50 sec /% or more.

According to the present invention, an excellent dehydration effect can be obtained even for sludge that is difficult to dehydrate, and a dehydrated cake having a low water content can be efficiently obtained by improving the dehydration property and the filtration rate.

It is a graph which shows the relationship between the PAC addition amount of Example II-1 and Comparative Examples II-1, 3 and CST / ds of agglutinating sludge. It is a graph which shows the relationship between the addition amount of DADMAC of Example II-2 and Comparative Example II-2, 4 and CST / ds of agglutinating sludge. It is a graph which shows the relationship between the PAC addition amount of Example III-1 and Comparative Example III-1 and CST / ds of agglutinating sludge. It is a graph which shows the relationship between the amount of DAM addition of Example III-2 and Comparative Example III-2, and CST / ds of agglutinating sludge. It is a graph which shows the relationship between the addition amount of DADMAC of Example III-3 and Comparative Example III-3, and CST / ds of agglutinating sludge. It is a graph which shows the relationship between the amount of epichloro addition of Example III-4 and Comparative Example III-4, and CST / ds of agglutinating sludge. It is a graph which shows the relationship between the PAC addition amount of Example VI-1 and Comparative Example VI-1 and CST / ds of agglutinating sludge. It is a graph which shows the relationship between the addition amount of DADMAC of Example VI-2 and Comparative Example VI-2, and CST / ds of agglutinating sludge.

Embodiments of the present invention will be described in detail below.

[Working mechanism]
The anionic organic polymer flocculant having an intrinsic viscosity of 3 dl / g or less used in the present invention has a molecular weight of about 10 million and an intrinsic viscosity of about 15 dl / g or more, which is conventionally used for general sludge treatment. The molecular weight is much smaller than that of the organic polymer flocculant. Such a low molecular weight anionic organic polymer flocculant can be used as an aqueous solution having a dissolution concentration of about 20% by weight, and even such a high concentration polymer solution has low viscosity and viscosity of sludge. There is no risk of worsening drainage by increasing the amount. In addition, since the viscosity is low, the reaction rate with the suspended substance particles in the sludge is fast, the coagulation property of the suspended substance can be effectively increased, the dehydration property is improved, the filtration rate is improved, and the water content is low. Dehydrated cake can be obtained efficiently.

Moreover, if it is a low molecular weight anionic organic polymer flocculant, a water-soluble product of about 20% by weight can be applied as it is, and a solid high molecular weight anionic organic polymer flocculant is 0.1% by weight. It eliminates the need for labor to dissolve to a certain concentration and water for dissolving the anionic organic polymer flocculant, and can save space when installing a chemical tank or the like.

Further, when such a low molecular weight anionic organic polymer flocculant is used in combination with an inorganic flocculant and / or a cationic organic polymer flocculant, treatment with only the inorganic flocculant or the cationic organic polymer flocculant is performed. Compared with the case, the dehydration effect can be further enhanced by the more excellent coagulation action.

The details of the mechanism of action of the effect of improving the dehydration property when the anionic organic polymer flocculant and the inorganic flocculant and / or the cationic organic polymer flocculant are used in combination are not clear, but are presumed as follows.
First, the anionic group of the anionic organic polymer flocculant is adsorbed on the positively charged end face of the clay particles in the sludge. Then, the nonionic group of the anionic organic polymer flocculant is physically adsorbed on the clay particles to first condense the solid content in the sludge. Next, the layer surface of the clay particles negatively charged in the sludge by the addition of the inorganic flocculant and / or the cationic organic polymer flocculant as the cationic component, or the anion of the anionic organic polymer flocculant added earlier. By further adsorbing the cationic group of the cation component to the sexual group and causing secondary coagulation, a more effective coagulation action is exerted than when the cation component is used alone, and a high dehydration effect can be obtained.

<Sludge that is difficult to dehydrate>
The sludge to be treated in the present invention is excess sludge generated in civil engineering / construction work, or treatment of sewage, urine, steel wastewater, pulp and paper wastewater, food factory wastewater, automobile factory wastewater, petrochemical factory wastewater, and machine factory wastewater. It is the sludge generated in. The dehydrating agent of the present invention is also effective for poorly dehydrating sludge in which sufficient dehydration cannot be obtained by treatment with PAC alone.

In the present invention, the poorly dehydrated sludge is the total solid content concentration ds in the sludge based on the CST value evaluated by the CST (Capillary Suction Time) measurement method (Filtration / Squeezing Technology Manual, edited by Japan Powder Industry Technology Association, pp. 305 to 309). Refers to sludge having a CST / ds (sec /%) value divided by 50 sec /% or more.
In CST measurement, the time for free water in sludge to permeate the filter paper for a certain distance by capillarity: CST value is measured. The CST value is an index of sludge dewatering property, and the shorter the time, the better the dewatering property.

Sludge with a CST / ds value of 50 sec /% or more without treatment has a sufficient dewatering effect even if the standard design PAC is added to the sludge generated during shield construction at a standard design addition amount of 25 kg / ss-t. Is not obtained, so it is defined as "sludge that is difficult to dehydrate".

Such refractory sludge is mainly used for civil engineering and construction works such as dredging work, boring work, pile work, underground continuous wall work, shield work, sewage, urine, paper and pulp drainage, and food factory drainage. , Occurs in the treatment of wastewater from petrochemical plants.

<Anionic organic polymer flocculant>
The anionic organic polymer flocculant used in the present invention has an intrinsic viscosity of 3 dl / g or less. The anionic organic polymer flocculant having an intrinsic viscosity of 3 dl / g or less is a low molecular weight aqueous solution anionic organic polymer flocculant having a molecular weight of 3 million or less, and is 5 to 50% by weight, preferably about 10 to 40% by weight. Can be added to sludge as a relatively high concentration aqueous solution (polymer solution) of.
When the intrinsic viscosity of the anionic organic polymer flocculant exceeds 3 dl / g, the viscosity of the obtained polymer solution is high.
(1) Increases the viscosity of the sludge itself and worsens drainage. (2) The reactivity with the suspended substance particles in the sludge is slowed down, and the cohesiveness of the suspended substance deteriorates, so the desired effect is obtained. Can't

The intrinsic viscosity of the anionic organic polymer flocculant used in the present invention is more preferably 2.5 dl / g or less. The lower limit of the intrinsic viscosity of the anionic organic polymer flocculant is usually 0.1 dl / g. Anionic high content with intrinsic viscosity of 0.1 dl / g or less acts as a dispersant for suspended substances and does not function as a flocculant.

Here, the intrinsic viscosity of the anionic organic polymer flocculant is a value measured at 30 ° C. in a specified aqueous solution of sodium nitrate.

The anionic organic polymer flocculant used in the present invention is not particularly limited as long as it satisfies the above intrinsic viscosity, but is anionic in the polymer in order to obtain the effect as an anionic organic polymer flocculant. Those containing 5 mol% or more of groups, particularly 10 mol% or more, are preferable. If the content of the anionic group is less than 5 mol%, the effect as an anionic organic polymer flocculant may not be obtained.

Examples of the anionic monomer as a raw material of the anionic organic polymer flocculant include carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid, styrene sulfonic acid, vinyl sulfonic acid and aryl sulfonic acid, 2 Examples thereof include sulfonic acids such as −acrylamide-2-methylpropanesulfonic acid and 3-allyloxy-2-hydroxypropanesulfonic acid, or salts thereof.

The anionic organic polymer flocculant may be one or more homopolymers or copolymers (anionic group content 100 mol%) of these anionic monomers, and one or two of the above anionic monomers. It may be a copolymer of one or more species and one or more nonionic monomers such as acrylamide and methacrylamide. When the anionic organic polymer flocculant is a copolymer of an anionic monomer and a nonionic monomer, it preferably contains 5 to 90 mol% of anionic groups and 10 to 95 mol% of nonionic groups.

Only one type of anionic organic polymer flocculant may be used, or two or more types having different monomer compositions and intrinsic viscosities may be used in combination.

As described above, the anionic organic polymer flocculant is added to the sludge as an aqueous solution of about 5 to 50% by weight.

<Inorganic flocculant>
Examples of the inorganic flocculant used in combination with the anionic organic polymer flocculant include aluminum chloride, polyaluminum chloride (PAC), aluminum sulfate (sulfate band), sodium aluminate, ferrous chloride, ferric chloride, iron sulfate, etc. Water-soluble metal salts such as aluminum sulfate, calcium chloride, sodium borate, and sodium silicate can be mentioned, but an aluminum salt having a particularly high valence is efficient and is preferably used.
Only one kind of inorganic flocculant may be used, or two or more kinds may be used in combination.

<Cationic organic polymer flocculant>
As a cationic organic polymer flocculant to be used in combination with an anionic organic polymer flocculant, 5 mol% or more, particularly 10 mol% or more of cationic groups are contained in the polymer in order to obtain the effect as a cationic organic polymer flocculant. Those containing are preferable. If the content of the cationic group is less than 5 mol%, the effect as a cationic organic polymer flocculant may not be obtained.

Examples of the cationic monomer as a raw material for the cationic organic polymer flocculant include acrylate-based, methacrylate-based, diallylamine-based, alkylamine / epichlorohydrin condensate-based, imine-based, polyvinylamidine-based, and Mannich-modified acrylamide compounds. Examples thereof include these salts or quaternized compounds.

Examples of the cationic organic polymer flocculant include a copolymer (preferably containing a cationic group) of one or more nonionic monomas such as acrylamide and methacrylamide and one or more of the above cationic monomers. A homopolymer or copolymer (cationic group content) consisting of only one or more cationic monomers and a nonionic group content of 5 mol% or more, particularly 10 mol% or more in an amount of 5 mol% or more, particularly 10 mol% or more. 100 mol%).

The intrinsic viscosity of the cationic organic polymer flocculant is not particularly limited, and a general-purpose intrinsic viscosity of about 0.1 to 15 dl / g can be used.
Here, the intrinsic viscosity of the cationic organic polymer flocculant is a value measured at 30 ° C. in a specified sodium nitrate aqueous solution.

Only one type of cationic organic polymer flocculant may be used, or two or more types having different monomer compositions and intrinsic viscosities may be used in combination.

The cationic organic polymer flocculant is usually added to sludge as an aqueous solution of about 0.1 to 50% by weight.

<Agglomeration / dehydration method>
In the present invention, only the above-mentioned anionic organic polymer flocculant may be added to the sludge for aggregation and dehydration treatment, or the anionic organic polymer flocculant and the inorganic flocculant and / or the cationic organic polymer may be added. A flocculant may be added in combination for coagulation and dehydration treatment. When an inorganic flocculant and / or a cationic organic polymer flocculant is used in combination, the order of addition is as follows: the anionic organic polymer flocculant is added, and then the inorganic flocculant and / or the cationic organic polymer flocculant is added. It may be added, and the anionic organic polymer flocculant may be added after the inorganic flocculant and / or the cationic organic polymer flocculant is added, but the anionic organic polymer flocculant is preferably added first. In terms of dehydration effect, a method of adding an inorganic flocculant and / or a cationic organic polymer flocculant to perform the flocculation treatment is preferable.

Therefore, when the sludge dehydrating agent of the present invention contains an anionic organic polymer flocculant and an inorganic flocculant and / or a cationic organic polymer flocculant, the anionic organic polymer flocculant and the inorganic flocculant and / or cationic. It is included as a separate agent from the organic polymer flocculant.

When only an anionic organic polymer flocculant is used as the sludge dehydrating agent, the amount of the anionic organic polymer flocculant added varies depending on the sludge properties and is not particularly limited, but it is difficult to have a CST / ds value of about 50 to 500 sec /%. In the case of dehydrating sludge, the amount of pure content (anionic organic polymer flocculant) added is ^{about 0.01 to 1 kg / m 3, and the} mixture is mixed by stirring for about 20 seconds to 5 minutes to coagulate. After that, dehydration treatment is preferable.

When an anionic organic polymer flocculant and an inorganic flocculant and / or a cationic organic polymer flocculant are used as the sludge dehydrating agent, the amount of each flocculant added varies depending on the sludge properties and is not particularly limited, but CST / ds. In the case of refractory sludge with a value of about 50 to 500 sec /%, an anionic organic polymer flocculant is added as a pure content (anionic organic polymer flocculant) of about ^{0.01 to 1 kg / m 3.} After mixing and coagulating with stirring for about 20 seconds to 5 minutes, in the case of an inorganic coagulant, the pure content (inorganic coagulant) is ^{about 0.1 to 5 kg / m 3} , and the cationic organic polymer coagulant. ^{In this case, it is preferable to add about 0.1 to 5 kg / m 3} as a pure component (cationic organic polymer flocculant), mix the mixture by stirring for about 20 seconds to 5 minutes, etc., and then perform dehydration treatment.

The sludge dehydrating agent and the sludge may be mixed in the transfer pipe or in a separately provided agglutination reaction tank. Further, if the dehydrator has a mixing mechanism such as a centrifugal dehydrator, the mixing step before dehydration can be omitted.

As the agglutination reaction tank, a general vertical agglutination reaction tank with stirring blades can be used, and no special reaction device is required. In addition, the applicable dehydrators are not particularly limited, and various dehydrations such as multiple disk dehydrators, screw press dehydrators, rotary pressurizing (rotary) dehydrators, filter press dehydrators, belt press dehydrators, centrifugal dehydrators, etc. Although a machine can be applied, the sludge dehydrating method using the sludge dehydrating agent of the present invention is particularly excellent in improving the filtration rate, so dehydration using a filter press dehydrator in which the filtration rate is important is preferable.

According to the present invention, such a dewatering treatment can efficiently obtain a dewatered cake having a low water content as compared with conventional sludge dewatering agents and sludge dewatering methods. The obtained dehydrated cake is used for incineration or landfill.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded.

[Evaluation method of dehydration]
The dehydration property of sludge was evaluated by the CST (Capillary Suction Time) measurement method under the following conditions.
-Filter paper: Whatman's "Chromatography Paper No. 17"
A filter paper after drying at 105 ° C. for 1 hour was used.
-Measurement: The time (CST) at which the filter water in the coagulated sludge permeates the filter paper by 1 cm due to the capillary phenomenon is measured, and this value is divided by the total solid content concentration ds of the sludge to be treated (CST / ds (sec /%). )) Was asked.
It is said that if the CST / ds value of the coagulated sludge is 10 sec /% or less, sufficient dehydration can be obtained even in the realization field, and the target value is 10 sec /% or less.

[Sludge to be treated]
The properties of the treated refractory sludge are shown in Table 1 below.

[Coagulant]
The following were used as the coagulant.

<Anionic organic polymer flocculant>
The acrylamide-sodium acrylate copolymer having the intrinsic viscosity and the anionic group content shown in Table 2 below was used.

<Inorganic flocculant>
PAC: Polyaluminum chloride 10-11 wt% aqueous solution (Thai Pack (Daimei Chemicals Co., Ltd.))

<Cationic organic polymer flocculant>
DADMAC: Polydialyldimethylammonium chloride (intrinsic viscosity: 0.7 dl / g, cationic group content: 100 mol%)
DAM: Polydimethylaminoethyl methacrylate / methyl chloride (intrinsic viscosity: 0.5 dl / g, cationic group content: 100 mol%)
Epichloro: Alkylamine-epichlorohydrin polycondensate (intrinsic viscosity: 0.1 dl / g, cationic group content: 100 mol%)

[Verification of the effect of anionic organic polymer flocculant single treatment on poorly dehydrated sludge: Examples I-1 to 10, Comparative Examples I-1 and 2]
<Test method>
Table 3 shows the anionic organic polymer flocculants shown in Table 3 as an aqueous solution having a dissolution concentration shown in Table 3 with respect to sludge A (CST / ds: 124 (sec /%) when untreated). The mixture was added so as to have a pure content (addition amount as an anionic organic polymer flocculant) and stirred for 30 seconds. The obtained coagulated sludge was used as a sample for CST measurement to evaluate the dehydration property, and the results are shown in Table 3.
Incidentally, CST / ds value described in Table 3 are represented the CST / ds value showing the minimum value in added in purity content of the anionic organic polymeric flocculant to 0.6 kg / ^{m 3.} The amount of pure content added is the amount of anionic organic polymer flocculant added when the CST / ds value shows the minimum value.

<Discussion>
The following can be seen from Table 3.
The CST / ds value of untreated sludge A is 124 sec /%, whereas the low molecular weight anionic organic polymer flocculant used in Examples I-1 to 10 having an intrinsic viscosity of 3.0 dl / g or less. The CST / ds value was 40 sec /% or less under almost all conditions, showing an improvement effect on dehydration of nearly 70% in terms of the no-treatment ratio. On the other hand, when the anionic organic polymer flocculant having an intrinsic viscosity of 14.0 dl / g or more used in Comparative Examples I-1 and I-1 and 2 was added alone, the good dehydration improving effect as in the examples was confirmed. Can not.
From this example, it can be seen that a good dehydration improving effect can be obtained by applying a low molecular weight anionic organic polymer flocculant having an intrinsic viscosity of 3.0 dl / g or less.

If an anionic organic polymer flocculant is added alone and has an effect of improving dehydration, a better dehydration treatment effect can be obtained when used in combination with an inorganic flocculant or a cationic organic polymer flocculant. Since it is presumed to be possible, the effect will be verified below.

[Verification of the combined effect of an inorganic flocculant or a cationic organic polymer flocculant on poorly dehydrating sludge: Examples II-1 and 2, Comparative Examples II-1 to 4]
<Test method>
PAC was used as the inorganic flocculant, DADMAC was used as the cationic organic polymer flocculant, and DADMAC was used as a 10% by weight aqueous solution.

To the poorly dehydrated sludge A, the anionic organic polymer flocculant shown in Table 4 was added as an aqueous solution having a dissolution concentration of 0.2% by weight so that the ^{pure content was 0.075 kg / m 3.} After stirring for 30 seconds, PAC or DADMAC was added in different amounts and stirred for 30 seconds, and the obtained coagulated sludge was used as a sample for CST measurement to evaluate dehydration.

Here, in order to unify the dilution factor of the muddy water with the anionic organic polymer flocculant, the dissolution concentration of the anionic organic polymer flocculant used in the examples is 0.2% by weight, which is the same as the upper limit of the dissolution concentration of the comparative example. And said.

The relationship between the amount of PAC added or the amount of DADMAC added and the evaluation result of aggregated sludge is shown in FIGS. 1 and 2, respectively.

<Discussion>
As shown in FIGS. 1 and 2, in Examples II-1 and 2, CST / ds = 10 sec /% or less can be achieved only by adding the anionic organic polymer flocculant without adding PAC and DADMAC.
On the other hand, in Comparative Examples II-1 to II-4, it is possible to reduce CST / ds by increasing the amount of PAC and DADMAC added, but the dehydration effect is inferior to that of Examples.

From these results, even when used in combination with an inorganic flocculant or a cationic organic polymer flocculant, a low molecular weight anionic organic polymer flocculant has a more dehydrating effect than a high molecular weight anionic organic polymer flocculant. It turns out that it is excellent.

Therefore, the dehydration effect when the low molecular weight anionic organic polymer flocculant is used in combination with the inorganic flocculant which is a cationic component or the cationic organic polymer flocculant is examined below.

[Verification of the combined effect of the cation component and the low molecular weight anionic organic polymer flocculant on the poorly dehydrating sludge: Examples III-1 to 4, Comparative Examples III-1 to 4]
<Test method>
PAC was used as the inorganic flocculant, DAM, DADMAC, or Epiclo was used as the cationic organic polymer flocculant, DAM and DADMAC were used as an aqueous solution having a dissolution concentration of 10% by weight, and Epiclo was used as an aqueous solution having a dissolution concentration of 50% by weight.

In Examples III-1 to 4, the anionic organic polymer flocculant No. 2 was applied to the sludge B which is difficult to dehydrate. 7 (intrinsic viscosity: 2.3 dl / g, the anionic group content: 81 mol%) as an aqueous solution of the dissolved concentration of 15.0 wt%, was added to a pure content amount 0.23 kg / ^{m 3} 30 After stirring for 2 seconds, the inorganic flocculant or cationic organic polymer flocculant shown in Table 5 was added in different amounts, and the mixture was stirred for 30 seconds. The obtained coagulated sludge was used as a sample for CST measurement to evaluate dehydration.
In Comparative Examples III to 1-4, the anionic organic polymer flocculant was not added, but the inorganic flocculant or the cationic organic polymer flocculant shown in Table 5 was added to the sludge B in different amounts. The mixture was stirred for 30 seconds. The obtained coagulated sludge was used as a sample for CST measurement to evaluate dehydration.

The relationship between the amount of the inorganic coagulant added or the amount of each cationic organic polymer coagulant added and the evaluation result of the coagulated sludge is shown in FIGS. 3 to 6, respectively.

<Discussion>
As shown in FIGS. 3 to 6, when only the inorganic flocculant or the cationic organic polymer flocculant is used, the required addition amount for obtaining CST / ds = 10 sec /% of the aggregated sludge is 15 kg / m in the case of PAC. ³ or more, in the case of a cationic organic polymer flocculant, the pure content addition concentration is 1.5 kg / m ³ or more (Comparative Examples III-1 to 3-4). On the other hand, when the low molecular weight anionic organic polymer flocculant and the inorganic flocculant or the cationic organic polymer flocculant are used in combination, the PAC is 3 kg / m ³ and the cationic organic polymer flocculant is the pure addition concentration. 10 sec /% can be achieved at 0.5 kg / m ³ or less (Examples III-1 to 4).

From the above, it is better to use the low molecular weight anionic organic polymer flocculant together than to use only the inorganic flocculant or the cationic organic polymer flocculant to add the inorganic flocculant or the cationic organic polymer flocculant. It can be seen that the amount and the total amount of the flocculant added can be significantly reduced.
The mechanism of action for obtaining the above effects is presumed as described above.

From this example, it can be seen that the low molecular weight anionic organic polymer flocculant used in the present invention can be applied to various difficult-to-dehydrate sludges. Further, it can be seen that regardless of the composition of the cation component used in combination, a good dehydration effect can be obtained after reducing the required amount of the cation component added as compared with the dehydration treatment of the cation component alone.

[Verification of dehydration effect by filter press of anionic organic polymer flocculant alone on poorly dehydrating sludge: Example IV-1, Comparative Examples IV-1 to 3]
<Test method>
Using the following laboratory filter press, a dehydration test of refractory sludge A was conducted under the following conditions.
Test filter press: Round filter press (Nippon Steel & Sumitomo Metal Environment Co., Ltd.)
Filtration area: 0.008m ²
Filter chamber volume: 0.251L
Filter cloth: 1000 cm ³ / cm ² / min polypropylene filter cloth Test method: Test sludge mixed with a dehydrating agent was ^{continuously press-fitted into the filter chamber at a pressure of 5 kgf / cm 2} , and the test was completed after 1 hour. The dehydration property and the filtration rate (dehydration rate) were evaluated from the water content of the dehydrated cake obtained.
Sample preparation: Anionic organic polymer flocculant or PAC was added alone to the poorly dehydrated sludge A, and the mixture was stirred for 60 seconds. The obtained coagulated sludge was used as a sample for a filter press filtration test. In Example IV-1 and Comparative Examples IV-1 and IV-1, the anionic organic polymer flocculants shown in Table 6 were added so as to have the dissolution concentration shown in Table 6 and the pure amount added in Table 6. did. In Comparative Example IV-3, PAC was added in the amount shown in Table 6.

<Discussion>
As shown in Table 6, Example IV-1 using the low molecular weight anionic organic polymer flocculant of the present invention and Comparative Example IV-1 using the conventional high molecular weight anionic organic polymer flocculant. Comparing 2 and 2, the cake moisture content and the dehydration rate of Example IV-1 are superior by 5% or more and 20% or more, respectively. Further, as in Comparative Example IV-3, in Example IV-1, the standard design addition amount of 25 kg / ss-t was added as the dehydration treatment of sludge generated by the muddy water shield method. It can also be seen that good dehydration treatment is possible.
From these results, it can be seen that if the anionic organic polymer flocculant has an intrinsic viscosity of 3 dl / g or less, sufficient dehydration treatment can be performed even by a single treatment of the anionic organic polymer flocculant.

[Verification of dewatering effect by filter press in combination with cation component for refractory sludge and low molecular weight anionic organic polymer flocculant: Examples V-1, 2, Comparative Examples V-1 to 4]
<Test method>
A dehydration test of poorly dehydrating sludge B was carried out using the same laboratory filter press, filter chamber and filter cloth used in Example IV-1.
Test method: The test sludge mixed with the dehydrating agent was ^{continuously press-fitted into the filter chamber at a pressure of 6 kgf / cm 2} , and the test was completed 2 hours later. (Dehydration rate) was evaluated.
Sample preparation:
(When using an anionic organic polymer flocculant and a cation component together)
The anionic organic polymer flocculant shown in Table 7 was added to sludge B at the dissolution concentration shown in Table 7 so as to have the pure content shown in Table 7, and after stirring for 60 seconds, PAC or DADMAC was dissolved. An aqueous solution having a concentration of 10% by weight was added so as to have the pure content shown in Table 7, and the mixture was stirred for 60 seconds. The obtained coagulated sludge was used as a sample for a filter press filtration test.
(When adding only the cation component)
PAC or DADMAC was added to sludge B as an aqueous solution having a dissolution concentration of 10% by weight so as to have the pure content shown in Table 7, and the mixture was stirred for 60 seconds. The obtained coagulated sludge was used as a sample for a filter press filtration test.

<Discussion>
As shown in Table 7, when a low molecular weight anionic organic polymer flocculant is used in combination with a cation component according to the present invention (Examples V-1, 2), a high molecular weight anionic organic polymer flocculant and a cation are used. The cake moisture content can be reduced by nearly 10% and the dehydration rate is 1 kg-ds / m as compared with the case where the components are used in combination (Comparative Examples V-1 and 2) and the case where the standard specification PAC treatment is performed (Comparative Example V-3). It can be made faster than ^{2 / h.}
From this example, it can be seen that according to the present invention, good dehydration can be obtained for sludge that is difficult to dehydrate even under conditions close to those of an actual machine.

[Verification of the combined effect of a low molecular weight anionic organic polymer flocculant and a cation component on ordinary dehydrating sludge: Examples VI-1 and 2, Comparative Examples VI-1 and 2]
<Test method>
PAC was used as the inorganic flocculant, DADMAC was used as the cationic organic polymer flocculant, and DADMAC was used as a 10% by weight aqueous solution.

In Examples VI-1 and 2, the anionic organic polymer flocculant No. 2 was added to the ordinary dehydrating sludge C. 7 (Intrinsic viscosity: 2.3 dl / g, anionic group content: 81 mol%) was added as an aqueous solution having a dissolution concentration of 15.0% by weight so as to have a pure content of 0.15 kg / m ^3. After stirring for 2 seconds, the inorganic flocculant or cationic organic polymer flocculant shown in Table 8 was added in different amounts, and the mixture was stirred for 30 seconds. The obtained coagulated sludge was used as a sample for CST measurement to evaluate dehydration.
In Comparative Examples VI-1 and VI-1, the anionic organic polymer flocculant was not added, but the inorganic flocculant or the cationic organic polymer flocculant shown in Table 8 was added to the sludge C in different amounts. The mixture was stirred for 30 seconds. The obtained coagulated sludge was used as a sample for CST measurement to evaluate dehydration.

The relationship between the amount of the inorganic coagulant added or the amount of each cationic organic polymer coagulant added and the evaluation result of the coagulated sludge is shown in FIGS. 7 and 8, respectively.

<Discussion>
As shown in FIGS. 7 and 8, when only the inorganic flocculant or the cationic organic polymer flocculant is used, the required addition amount for obtaining CST / ds = 10 sec /% of the aggregated sludge is 15 kg / m in the case of PAC. ³ or more, in the case of a cationic organic polymer flocculant, the pure content addition concentration is 1.5 kg / m ³ or more (Comparative Examples VI-1 and 2). On the other hand, when the low molecular weight anionic organic polymer flocculant is used in combination with the inorganic flocculant or the cationic organic polymer flocculant, the PAC is 5 kg / m ³ and the cationic organic polymer flocculant is the pure addition concentration. 10 sec /% can be achieved at 0.1 kg / m ³ or less (Examples VI-1 and 2).

From this example, the low molecular weight anionic organic polymer flocculant used in the present invention can obtain better dewatering property than adding the cation component alone to ordinary dewatering sludge, and is applicable. It turns out that there is.

Claims (8)

A surplus sludge dehydrating agent occurring in civil engineering and construction, intrinsic viscosity 3 dl / g observed including the following anionic organic polymer flocculants, the anionic organic polymeric flocculant is an acrylic acid and / or acrylic A sludge dehydrating agent that is a copolymer of acid salt and acrylamide. The sludge dehydrating agent according to claim 1, which comprises the anionic organic polymer flocculant and an inorganic flocculant and / or a cationic organic polymer flocculant. The sludge dehydrating agent according to claim 1 or 2, which contains the anionic organic polymer flocculant as an aqueous solution having a dissolution concentration of 10% by weight or more. The sludge dehydrating agent according to any one of claims 1 to 3, wherein the sludge is a poorly dehydrating sludge having a CST / ds value of 50 sec /% or more. The excess sludge generated in the civil engineering and construction, a sludge dewatering process for dewatering process after flocculation treatment by adding an anionic organic polymer flocculant follows intrinsic viscosity of 3 dl / g, the anionic organic polymer A sludge dehydration method in which the flocculant is a copolymer of acrylic acid and / or acrylate and acrylamide . The fifth aspect of claim 5, wherein the anionic organic polymer flocculant is added to the sludge for coagulation treatment, then an inorganic coagulant and / or a cationic organic polymer flocculant is added for coagulation treatment, and then dehydration treatment is performed. Sludge dehydration method. The sludge dewatering method according to claim 5 or 6, wherein the anionic organic polymer flocculant is added as an aqueous solution having a dissolution concentration of 10% by weight or more. The sludge dewatering method according to any one of claims 5 to 7, wherein the sludge is a poorly dehydrating sludge having a CST / ds value of 50 sec /% or more.

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