JP2000153264A - Gelling agent of scum-containing waste water and treatment of scum using the agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treating agent and a treating method capable of easily recovering the scum in the sewage discharged from homes and factories. SOLUTION: The gelling agent consisting of a water-soluble or water- dispersible urethane prepolymer obtained by subjecting polyisocyanate to addition reaction with a hydrophilic alkyleneoxide copolymer in which (i) the content of an ethylene oxide unit in alkylene oxide polymeric chain is >=40 wt.% and <70 wt.% and (ii) average mol.wt. found from hydroxy group value is 6,000-9,000, in NCO/OH- equivalent ratio of 3.5-8, is used. By using this gelling agent, waste water containing scum is solidified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solidifying agent for solidifying an organic suspended substance generated on the surface of sewage, so-called scum, and a method for treating a scum-containing liquid using the same.

[0002]

2. Description of the Related Art Organic suspended matter (scum) generated on the surface of sewage is formed by various factors.

[0003] For example, oil in drainage floats and convects in a first sedimentation tank of a sewage treatment plant to form a scum rich in oil. In addition, when actinomycetes in the influent water are aerated and propagated in the terminal treatment plant, they foam in the reaction tank to form scum and float in the reaction tank and the final sedimentation basin.

[0004] The cause of the formation of oily scum is given as an example as follows.

[0005] Wastewater from a cafeteria, a home kitchen, or a factory contains various oils. Various edible fats and oils are dispersed and suspended in sewage discharged from a canteen and a kitchen at home. For example, vegetable oils such as sesame oil used for tempura and fried foods, and beef tallow and lard contained in meat and instant noodles. In addition, wastewater from the factory includes engine oil, gear oil, grease, lubricating oil waste oil, and the like. These oils float up and stay near the water surface together with other suspended solids in places where the flow velocity is reduced, such as a headrace of a sewage treatment plant or a first sedimentation tank. If left as it is, it accumulates and deposits on the surface layer, forming a thick layer.

[0006] Scum is difficult to treat with a water treatment agent or activated sludge, and is usually manually collected and landfilled.

However, as regulations on landfill disposal and repulsion of nearby residents have become stronger, it has become increasingly difficult to secure land for disposal. In addition, it is extremely difficult to collect scum accumulated and deposited on the surface of the water surface.

[0008] In the case of a scum containing a large amount of oil, it is conceivable to add a dispersant to emulsify the wastewater and burn it together with fuel oil. However, there is a problem that not only large-scale dedicated equipment is required, but also a supply pipe to the boiler is clogged by solid fats and oils and other solid waste.

Japanese Patent Application Laid-Open No. 53-108070 discloses a method of solidifying waste oil by adding water of the same weight or less and about the same weight of a polyisocyanate (polymeric MDI in the example) together with an amine catalyst and stirring. Is disclosed. However, when such a method of treating waste oil is applied to wastewater in which a relatively low concentration of fats and oils floats, strong stirring and mixing is required to disperse the polyisocyanate in water, and special equipment is required. I do. Further, the use of a large amount of polyisocyanate results in high cost.

[0010]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a chemical and a method for treating scum in sewage, which has been extremely difficult to recover. Provided is a solid which can be easily converted into a solid, which can be easily disposed of, and which does not require special equipment.

[0011]

The gelling agent for scum-containing wastewater according to claim 1 is a gelling agent which is added to and mixed with scum-containing wastewater to gel the wastewater. A polyisocyanate is added to an alkylene oxide polymer having the features of (i) to (ii) by NCO- / OH
-It is characterized by comprising a water-soluble or water-dispersible urethane prepolymer obtained by an addition reaction at an equivalent ratio of 3.5 to 8.

(I) The content of ethylene oxide units in the polymerized alkylene oxide chain is from 40% by weight to less than 70% by weight, and (ii) the average molecular weight determined from the hydroxyl value is from 6,000 to 9000.

The scum-containing wastewater can be easily converted into a gel which can be easily handled by the gelling agent having the above structure. Further, since the ratio of the hydrophilic group and the non-hydrophilic group, that is, the balance of hydrophilicity-hydrophobicity becomes very appropriate, the consolidation property to scum-containing wastewater is very good, and the crushability is good. Yes, and furthermore, a high degree of water separation can be obtained due to moderate partial gelation.

[0014] In the gelling agent for scum-containing wastewater according to claim 2, in the gelling agent for scum-containing wastewater according to claim 1, the alkylene oxide polymer is diol or triol, and the polyisocyanate is aromatic. Characterized in that it is an aromatic diisocyanate.

In the gelling agent for scum-containing wastewater according to claim 3, the scum-containing wastewater gelling agent according to claim 1 is added to and mixed with wastewater containing scum having a concentration of 50% by weight or less. It is characterized by.

According to a fourth aspect of the present invention, in the method for treating scum, a polyisocyanate is added to the alkylene oxide polymer having the following features (i) to (ii) by NCO- / OH.
The wastewater is obtained by mixing and adding 0.5 to 50 parts by weight of a gelling agent consisting of a urethane prepolymer obtained by an addition reaction at an equivalent ratio of 3.5 to 8 with respect to 100 parts by weight of wastewater containing scum; Is characterized by being gelled.

(I) The content of ethylene oxide units in the polymerized alkylene oxide chain is from 40% by weight to less than 70% by weight, and (ii) the average molecular weight determined from the hydroxyl value is from 6,000 to 9000.

According to a fifth aspect of the present invention, there is provided the scum processing method according to the fourth aspect, wherein the scum contained in the wastewater at a concentration of 50% by weight or less is treated. .

According to a sixth aspect of the present invention, there is provided a method of treating scum according to the fourth aspect, wherein the scum is burnt and disposed after the gelation.

According to the above configuration, the gelled material can be easily discarded.

According to a seventh aspect of the present invention, in the scum processing method of the sixth aspect, the scum is dried to a water content of 30% or less and the obtained solid is used as a fuel. Features.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the scum treatment method of the present invention, a water-soluble or water-dispersible urethane prepolymer obtained by adding a polyisocyanate to a hydrophilic polyether polyol (alkylene oxide polymer) is used. The resulting gelling agent is added to waste water containing scum to gel. Thereby, the scum is trapped in the hydrous urethane gel.

The scum-containing wastewater suitable for the treatment according to the present invention includes those having a scum concentration of 0.3 to 50% by weight,
In particular, those having a concentration of 1 to 40% by weight.

The method of the present invention is applicable to scum generated in sewage. In the case of a scum containing a large amount of oil, in addition to those composed of vegetable and animal fats such as sesame oil and beef tallow, even those composed of engine oil, gear oil, grease, lubricating oil waste oil, etc. can be easily treated. it can. Further, in addition to such fats and oils or oils, even those containing a large amount of solid waste or those caused by actinomycetes can be treated similarly.

The alkylene oxide constituting the alkylene oxide polymer in the present invention includes hydrophilic ethylene oxide and non-hydrophilic propylene oxide, butylene oxide, styrene oxide and the like.

The alkylene oxide polymer of the present invention has a hydrophilic ethylene oxide unit content of 40% by weight or more and less than 70% by weight, preferably 50-70% by weight.

When the content of the ethylene oxide unit in the alkylene oxide polymer is less than 40% by weight, the hydrophilicity of the gelling agent is reduced, so that the scum-containing wastewater having a high water content (and therefore a low scum concentration) is used. Gelation performance is reduced. Here, the gelation performance includes the solidifying property (performance of gelling within a certain short time to become a solid substance) and crushing property (gel for crushing into a small-sized lump which is easy to handle). Hardness).

When the content of the ethylene oxide unit in the polymerized alkylene oxide chain is 40% by weight or more and less than 70% by weight, the solidification property with respect to the waste water containing scum is good, and it is relatively hard and easily crushed. In addition, since it is liable to partially gel, the later-described water separation (the degree of leaching of water from the hydrogel during standing) is increased, which is preferable. In general,
When the content is in the range of 40 to 90% by weight, the lower the content, the easier it is to form a partial gel, and the greater the water separation effect.

The type of copolymerization of ethylene oxide and non-hydrophilic alkylene oxide may be random copolymerization or block copolymerization. However, in general, a random copolymer is preferred in view of the viscosity of the obtained urethane prepolymer solution and the dispersibility in wastewater.

The alkylene oxide polymer of the present invention has 1 to 8, preferably 2 to 8, more preferably 2 to 4, and more preferably 2 to 3, active hydrogen groups. Therefore, as a starting material (initiator of polyether polyol formation) of the polyaddition reaction for adding the alkylene oxide, a low molecular weight compound having such a number of active hydrogen groups at the terminal (molecular weight of 1,000 or less, particularly 300
The following is used.

Particularly preferred starting materials are triols or diols. Triols include glycerin, trimethylolpropane, trimethylolethane,
In addition to triols having a simple structure such as 1,2,6-hexanetriol, triol compounds obtained by partially esterifying polyhydric alcohols such as sorbitol and pentaerythritol with fatty acids, and compounds such as triethanolamine are exemplified. Typical examples of the diol include ethylene glycol, diethylene glycol, and propylene glycol.
As the low molecular weight compound having 2 to 4 active hydrogen groups, tetraols such as pentaerythritol, diglycerin, and methyl glucoside can also be used. Instead of these polyols, a low molecular weight organic compound containing a phenolic hydroxyl group or an amino group as an active hydrogen group can be used alone or in combination with the polyol. For example, ethylenediamine or aromatic diamine can be used instead of tetraol.

The most common compounds having more than 4 and less than 8 active hydrogen groups are sorbitol having 6 functional groups and sucrose having 8 functional groups. However, these other various compounds are also suitably used as active hydrogen compounds.

The alkylene oxide polymer synthesized from a starting compound having one active hydrogen group (functional group) and therefore having one functional group cannot be used alone. If a urethane prepolymer is synthesized from a monol having one active hydrogen group, the viscosity is low and the storage stability is good, but the crosslink density in the urethane prepolymer is too low, and condensed with wastewater. Property becomes poor. However, it can be used as a mixture with an alkylene oxide polymer having two or more functional groups, and in particular, it can be added to and mixed with an alkylene oxide polymer having four or more functional groups to adjust the viscosity of the urethane prepolymer and storage stability. Can be improved.

The average molecular weight of the hydrophilic alkylene oxide polymer is from 6,000 to 9000. Average molecular weight of 60
If it is less than 00 or less, the ratio of isocyanate added for the urethane-forming reaction tends to increase. On the other hand, if the average molecular weight exceeds 9000 or further increases, the alkylene oxide polymer itself becomes highly viscous, so that filtration for purification becomes more difficult, and industrial production tends to be difficult. .

Here, the average molecular weight is a number average molecular weight calculated from the hydroxyl value. The hydroxyl value is measured by a known general method.

The above-mentioned alkylene oxide polymers can be used alone or in a suitable mixture for a reaction for producing a urethane prepolymer.

In the production of the gelling agent of the present invention, an acetalized polyol can be added to the above-mentioned alkylene oxide polymer, if necessary (Japanese Patent Publication No. 53 (1988)).
-19846).

As the polyisocyanate for producing the gelling agent of the present invention, TDI (tolylene diisocyanate in which the ratio of 2,4-TDI to 2,6-TDI is 100/0, 80/20) 65/35), NDI (naphthalene diisocyanate), pure MDI (4,4′- or 2,4′-diphenylmethane diisocyanate, monomeric MDI), liquid pure MDI (carbodiimide modification of pure MDI), In addition to aromatic polyisocyanates such as crude MDI (polymethylene polyphenyl isocyanate, polymeric MDI) and XDI (xylene diisocyanate),
Examples thereof include aliphatic polyisocyanates such as DI (hexamethylene diisocyanate) and trimethylhexamethylene diisocyanate, alicyclic polyisocyanates such as IPDI (isophorone diisocyanate), and mixtures thereof. Furthermore, 2 of each polyisocyanate
A dimer, a trimer, and an adduct with water or a low-molecular alcohol can also be used. Particularly preferred are aromatic diisocyanates.

In the above reaction of adding a polyisocyanate to the alkylene oxide polymer or a mixture thereof to form a polyurethane prepolymer, the equivalent ratio of isocyanate / hydroxyl group (NCO / OH) is 3.5 to 8. When the NCO / OH equivalent ratio is less than 3.5, the content of isocyanate groups that react with water in the obtained polyurethane prepolymer is relatively low, so that it is necessary to increase the amount added to the scum-containing wastewater. , Tends to be uneconomical. On the other hand, when the NCO / OH equivalent ratio exceeds 8, the amount of the isocyanate compound to be added increases, so that the hydrophilicity decreases, and the dispersibility and consolidation of the scum-containing wastewater decrease.

When the NCO / OH equivalent ratio is 3.5 to 8, the hydrophilicity is slightly reduced as compared with the case where the NCO / OH equivalent ratio is less than 3.5. Since the content is high, the solidification of scum-containing wastewater is improved. Therefore, wastewater can be gelated with a smaller amount of addition than a gelling agent having an NCO / OH equivalent ratio of less than 3.5.

When the NCO / OH equivalent ratio is in the range of 3.5 to 8 and the average molecular weight of the hydrophilic alkylene oxide polymer is in the range of 6,000 to 9000 as described above, the base polyol ( The balance between the amount of the alkylene oxide polymer) and the amount of the isocyanate compound is good. In particular, when the content of the ethylene oxide unit in the alkylene oxide polymerized chain is 40% by weight or more and less than 70% by weight, the ratio between the hydrophilic group and the non-hydrophilic group, that is, the balance between hydrophilicity and hydrophobicity is very appropriate. Becomes Therefore, the solidification property with respect to the scum-containing wastewater is very good, the crushing property is good, and a high degree of water separation is obtained because moderate partial gelation is observed.

The gelling agent of the present invention is a water-soluble or water-dispersible urethane prepolymer itself obtained by such a urethane-forming reaction, or a mixture obtained by adding an inert solvent thereto as a diluting solvent as appropriate. .

The diluting solvent preferably has a high boiling point and a large viscosity reducing effect. Examples of such a high-boiling-point diluent include dibasic acids (glutaric acid, succinic acid, and adipic acid) dimethyl ester (DBAM), γ-butyrolactone, dioctyl adipate (DOA), ethylene glycol diacetate (EGDA), and dibutyl phthalate (DBP). ), Dioctyl phthalate (DOP) and the like.

However, in addition to the high boiling point diluting solvent, a general inert solvent can be used.

By adding the diluting solvent as described above, the solubility and dispersibility of the obtained polyurethane prepolymer in water can be improved.

The amount of the gelling agent to be added is 0.5 to 80 parts by weight, preferably 0.5 to 50 parts by weight, based on 100 parts by weight of the wastewater containing scum.

If the amount of the gelling agent is too large, it is not economical. If the amount of the gelling agent is too small, the gelling performance such as caking and crushing properties becomes insufficient.

[0048]

EXAMPLES <Production of gelling agent> An example of the production of a gelling agent used in the scum treatment method of the present invention will be described below.

(1) Synthesis of Alkylene Oxide Polymer (Base Polyol as Gelling Agent) The following describes Production Example 6 in Table 1 below as an example.

Potassium hydroxide is added to glycerin at 0.4% by weight based on the target reaction yield, and dehydration and nitrogen replacement are performed under reduced pressure. A mixed alkylene oxide obtained by mixing ethylene oxide and propylene oxide at a weight ratio of 40/60,
Reaction temperature 100-130 ° C, reaction pressure 1-5Kg / cm
^The mixture is introduced at ^{2 for} 9 to 12 hours to carry out addition polymerization, and after the reaction pressure is lowered, the mixture is aged until equilibrium is reached, and then the reaction is terminated.

To the reaction crude product, 3% by weight of synthetic magnesium silicate was added, 31 is added at 0.5% by weight, and a vacuum neutralization treatment is performed at a temperature of 110 to 120 ° C. for about 1 hour. Thereafter, the mixture is filtered with a filter to obtain a highly pure and transparent ethylene oxide-propylene oxide random copolymer. The purified product after filtration is a high-purity hydrophilic polyol having an alkali metal content of 10 ppm or less and a water content of 0.05% or less.

(2) Synthesis of Water-Soluble or Water-Dispersible Urethane Prepolymer A description will be given of Production Example 1 in Table 1 below as an example.

The base polyol obtained in the same manner as described above under the conditions described in the column of Production Example 1 in Table 1 was heated at 120 ° C.
The solution was dehydrated under reduced pressure for 1 hour and once cooled to 60 ° C. Its 600
g was charged into a one-liter four-neck separable flask, and thereafter, 10 million pure MDI (p-MDI) Millionate MTF (Nippon Polyurethane Industry Co., Ltd.) was added.
0 g was added, and the mixture was stirred at 80-100 ° C. for 2 hours under a nitrogen atmosphere to carry out a reaction. The NCO- / OH-equivalent ratio at this time is 4. The reaction product obtained is a viscous urethane prepolymer having a free isocyanate group content of 4.1% by weight.

(3) Addition of high-boiling-point diluting solvent
C., and then cooled to dibasic acid dimethyl ester (DBA
M) was added and mixed thoroughly by stirring for 30 minutes. By adding such a high boiling point diluting solvent, the apparent viscosity of the urethane prepolymer was appropriately reduced.

The gelling agent thus obtained (Production Example 1) has a viscosity in a range where it can be easily handled, is water-soluble, and has excellent dispersibility in scum wastewater slurry. Further, as described later, the gelling performance is also excellent.

Table 1 summarizes the production conditions of the production examples of the gelling agent produced as described above.

[0057]

[Table 1] Only in Production Example 5, an ethylene oxide-butylene oxide (BO) copolymer was used as a base polyol for producing a urethane prepolymer, but in all other Production Examples, an ethylene oxide-propylene oxide copolymer was used. Further, only in Production Example 4, the block copolymer was used alone as the base polyol.
In 3, 5, 7 and 10, only random copolymers are used. In Production Example 8, a random copolymer was mixed mainly with a block copolymer, and in Production Example 9,
A block copolymer or the like is mixed mainly with a random copolymer.

The base polyols in Production Examples 8 and 9 are obtained by mixing two kinds of separately polymerized alkylene oxide polymers at a molar ratio shown in the column of "Mixing molar ratio".

The number of functional groups of the starting material to which the alkylene oxide is added, that is, the number of functional groups of the alkylene oxide polymer is 2 or 3 except for Preparation Examples 7 and 9.
In Production Example 7, sorbitol having 6 functional groups was used.
In Production Example 9, one having 8 functional groups was used in combination with one having 1 functional group.

In Production Example 8, 0.1 mol of an ethylene oxide-propylene oxide random copolymer was added to 0.9 mol of the same ethylene oxide-propylene oxide block copolymer used in Production Example 4.
Since the molecular weights of these two types of alkylene oxide polymers vary, the addition ratio of the homopolymer of ethylene oxide is considerably small in terms of weight ratio.

In Production Example 9, an ethylene oxide-propylene oxide block copolymer having a functional group number of 0.1 was prepared.
2 moles and 0.8 moles of an ethylene oxide-propylene oxide random copolymer having 8 functional groups are mixed and used.

In the reaction for producing a urethane prepolymer by adding an isocyanate compound, NCO- / O
All the H-equivalent ratios are set in the range of 3.5 to 8.

In Production Example 10, the same base polyol as in Production Example 3 was used, but in Production Example 3, the number of isocyanate groups (NCO number) was 2
While -80 is added at an NCO- / OH-equivalent ratio of 4, in Production Example 10, crude MDI having an average NCO number of 2.7 (c-MDI, polymeric MDI) was added to NCO-.
/ OH-added at an equivalent ratio of 6.

In all of the production examples, a high boiling point diluting solvent for decreasing the viscosity is added. The right end of Table 1 shows the weight concentration of the high-boiling diluent in the gelling agent product containing the high-boiling diluent.

Table 2 below summarizes the production conditions of the gelling agents of Comparative Production Examples produced by the same steps.

[0066]

[Table 2] Comparative Production Examples 1 and 3 show that propylene oxide units
A weakly hydrophilic ethylene oxide-propylene oxide random copolymer containing 80% by weight or 80% by weight is used. In particular, in Comparative Production Example 3, an ethylene oxide-propylene oxide random copolymer having the same number average molecular weight of 10,000 as Comparative Production Example 2 and a number average molecular weight of 6
A mixture of ethylene glycol of No. 2 with a molar ratio of 0.7 / 0.3 was used as the base polyol of the urethane prepolymer.

Comparative Production Example 4 uses the same alkylene oxide polymer as the base polyol as Production Example 4 in Table 1 and the isocyanate compound added thereto is the same, but only the amount of the isocyanate compound added is different. . In Comparative Production Example 4, although gelation occurred during the reaction for producing the urethane prepolymer, NCO- / OH
This is probably because the equivalent ratio was too low at 1.4.

<Scum-containing wastewater> The scum-containing wastewater used in the test is shown in Table 3 below.

The concentration of scum was measured by removing the water by heating and drying at 105 ° C. for 8 hours for waste water containing scum collected in a beaker.

In Table 3, in Example 5 of wastewater, scum was concentrated by a physical method such as normal pressure or pressure flotation, or centrifugation.

When the scum-containing wastewater is concentrated to a concentration of 50% or more, the fluidity is extremely low, so that mixing with the gelling agent becomes difficult. In addition, the process operation itself for concentration becomes very difficult.

[0072]

[Table 3] <Gelling of scum-containing wastewater and its evaluation> (1) Gelation treatment 100 g of the scum-containing wastewater of the above wastewater example was collected in a 200 ml beaker, and the gelling agent of the above production example was 2.5 to 50 g.
After stirring vigorously for 30 seconds with a hand mixer, the mixture was allowed to stand for a while. The temperature during the stirring and standing is 20 to 25 ° C.

Evaluation on gelation was performed as follows.

(2) Evaluation of Caking Property After the completion of the mixing and within 10 minutes thereafter,
When the gelation was completed and a solid substance having no tackiness was obtained, the sample was evaluated as "O", and when it was not, evaluated as "X".

When the time required for gelation is too long, for example, when gelation requires 10 hours to 1 day, the treatment becomes inefficient.

(3) Evaluation of crushability The obtained gel was tried to be crushed by a meat chopper, and those that could be crushed were evaluated as ○, and those that were soft and could not be crushed were evaluated as ×.

When a lump having an appropriate size can be easily formed by the crushing treatment, handling such as collection, transportation and incineration can be facilitated, and the following water separation and drying can be facilitated.

(4) Evaluation of Water Separation If crushing is possible, the crushed material is left, and if crushing is impossible, the obtained solidified material itself is left for a while. The amount of water separated from the gel and exuding was measured. The amount of the separated exuded water relative to the weight of the gel before standing is referred to as water separation. The water separation is 10% by weight or more. Less than was rated as ×.

In order to easily incinerate the gelled material by a normal incinerator, the water content must be 80% or less. However, if the concentration of scum in the wastewater is 10% by weight or more,
Combustion is possible without drying by water separation of 10% by weight or more. Usually, the concentration of scum is between 10 and 20% by weight.

In general, water separation tends to increase as the concentration of wastewater containing scum is lower, that is, as the proportion of water is larger. In addition, drying is usually performed to improve the incineration efficiency. In this case as well, those having water separation tend to have excellent drying properties.

(5) Evaluation Results Table 4 below summarizes gelling conditions and evaluation results.

The overall evaluation is shown at the right end of the table. Both of the solidification and crushability are evaluated as “「 ”, and those that can be incinerated as they are after water separation or solidification (solid content: 15% or more)
Was evaluated as “○” in the overall evaluation, and even one missing was evaluated as “X”.

[0083]

[Table 4] As shown in the above table, in all the examples, both the consolidation property and the crushability were good. As for the water separation, the water separation in Examples 2 to 11 was 10 to 20% by weight, and was evaluated as “○”. These gelling agents have a slightly lower hydrophilicity when the oxyethylene chain contained in the base polyol is 40 or more and less than 70% by weight, so that they are liable to form a partial gel when mixed with scum-containing wastewater,
It is considered that the water separation effect became large. In Examples 1 and 12, water separation was less than 2% by weight, and was evaluated as "x". However, these were also evaluated as “○” in the above comprehensive evaluation.

The reason why the water separation was small in Example 1 is considered to be that the amount of the gelling agent added was as high as 50 phr, and water was trapped in a dense urethane gel containing a large number of hydrophilic chains.

The reason why the water separation was small in Example 12 is considered to be that the concentration of scum in the wastewater was as high as 40%.

As shown in Comparative Examples 1 to 3 in Table 4, when the gelling agents of Comparative Production Examples 1 to 3 were used, no desired performance was obtained. As shown in Table 2, each of the gelling agents of Comparative Production Examples 1 to 3 had a non-hydrophilic alkylene oxide unit content of 70% by weight or more in the polyether chain, and exhibited dispersibility and reactivity in wastewater. Is considered to be low and the ability to form a hydrated gel is inferior.

According to the scum-containing wastewater treatment method of the above-described embodiment, gelation was completed within a sufficiently short time even when the amount of the gelling agent added was as small as 2.5 phr. Further, the obtained gelled product was easily formed into a lump having an appropriate size by a crushing treatment, so that handling such as collection, transportation, and incineration could be facilitated.

Further, since the obtained gelled product has water separation property, the water content of the hydrogel is naturally reduced, so that the product can be easily transported, dried and incinerated. In particular, water separation and drying properties are improved by the above-mentioned crushing treatment. Since drying is facilitated in this way, high incineration efficiency can be obtained.

In particular, the NCO / OH equivalent ratio is in the range of 3.5-8, the average molecular weight of the hydrophilic alkylene oxide polymer is in the range of 6,000-9000, and the ethylene oxide unit in the alkylene oxide polymer chain is Since the content is 40% by weight or more and less than 70% by weight, the ratio between the hydrophilic group and the non-hydrophilic group, that is, the balance between hydrophilicity and hydrophobicity becomes very appropriate. Therefore, the solidification property with respect to the scum-containing wastewater is very good, the crushing property is good, and a high degree of water separation is obtained because moderate partial gelation is observed.

[0090]

According to the present invention, wastewater containing scum, which is extremely difficult to handle as it is, can be easily converted into solid matter that can be easily handled. Moreover, the obtained solid can be easily disintegrated and easily reduced in water content, and can be easily burned and discarded in a usual incinerator.

Therefore, it is possible not only to cope with environmental problems but also to greatly reduce the labor and cost for processing scum.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Sogabe 1403 Matano-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture 17-704 F-term (reference) 4D051 AA04 EA04 EA05 EA14 EB04 EC03 EC16 EC19 4D059 BB01 BD00 BK14 CC03 EB01 4J034 BA03 DA01 DB04 DB05 DG02 DG03 DG14 HA01 HA02 HA07 HB07 HC03 HC12 HC13 HC17 HC22 HC34 HC35 HC46 HC52 HC64 HC67 HC71 HC73 JA42 QA03 QA05 RA17

Claims (7)

[Claims] Claims: 1. A scum-containing wastewater is added and mixed,
A gelling agent for gelling the waste water, wherein an addition reaction of an alkylene oxide polymer having the following characteristics (i) to (ii) with an isocyanate at an NCO- / OH-equivalent ratio of 3.5 to 8 is carried out. A gelling agent for scum-containing wastewater comprising a water-soluble or water-dispersible urethane prepolymer obtained by the above method. (I) the content of ethylene oxide units in the alkylene oxide polymerized chain is 40% by weight or more and less than 70% by weight, and (ii) the average molecular weight determined from the hydroxyl value is 6,000 to 6,000.
9000. 2. The method according to claim 1, wherein said alkylene oxide polymer is a diol or a triol, and said polyisocyanate is an aromatic diisocyanate.
The scum-containing wastewater gelling agent according to claim 1. 3. The scum-containing wastewater gelling agent according to claim 1, which is added to and mixed with wastewater containing scum having a concentration of 50% by weight or less. 4. An alkylene oxide polymer having the following characteristics (i) to (ii):
A gelling agent consisting of a urethane prepolymer obtained by an addition reaction at an / OH-equivalent ratio of 3.5 to 8 is mixed and added in an amount of 0.5 to 50 parts by weight with respect to 100 parts by weight of wastewater containing scum. A method for treating scum, wherein the wastewater is gelled. (I) the content of ethylene oxide units in the alkylene oxide polymerized chain is 40% by weight or more and less than 70% by weight, and (ii) the average molecular weight determined from the hydroxyl value is 6,000 to 6,000.
9000. 5. The method for treating scum according to claim 4, wherein scum contained in the wastewater at a concentration of 50% by weight or less is treated. 6. The method for treating scum according to claim 4, wherein the scum is burned and discarded after the gelation. 7. The scum treatment method according to claim 6, wherein the scum is dried to a water content of 30% or less, and the obtained solid is used as a fuel.