JP5037002B2 - Coagulation dewatering treatment method of sludge using polymer coagulant and coagulation sedimentation treatment method of waste water - Google Patents

Description

  The present invention relates to a method for coagulating and dewatering sludge using a polymer flocculant and a method for coagulating and precipitating wastewater.

Conventionally, a treatment method in which a polymer flocculant is added to wastewater to coagulate and precipitate a solid content has been widely used.
In addition, sludge generated during wastewater treatment is usually subjected to agglomeration dehydration treatment in which the solid content is agglomerated with a polymer flocculant for dehydration.
In these treatment methods, a method of adding a dilute aqueous solution of a polymer flocculant to waste water or sludge is widely employed.
There are various types of polymer flocculants with different molecular weights and ionic properties, etc., usually depending on the nature of the sludge to be treated (eg solid content concentration, surface charge amount of sludge particles, organic component content, etc.) The most suitable one is selected and used. Polymer flocculants are sold in the form of powder or W / O emulsion, but the powder type is superior in terms of product stability and ease of transportation, etc. Widely used.

  On the other hand, the properties of sludge vary widely depending on the type of wastewater and the treatment method. In addition, it is known that the properties of sludge vary with time due to rot and the like. Furthermore, even when two or more types of sludge are collected and processed, the sludge faces the problem of property variation according to the change in the mixing ratio of the sludge, as described above. For example, in the treatment of municipal sewage, etc., primary sludge and surplus sludge are usually mixed and treated as mixed raw sludge. In that case, the mixing ratio of these two types of sludge changes. Sludge properties vary greatly. In addition, the wastewater properties greatly change in the coagulation sedimentation treatment of the wastewater.

For this reason, it is necessary to adjust the type and amount of the polymer flocculant that is optimal for the treatment in accordance with changes in the properties of sludge or wastewater. However, the polymer flocculant is usually dissolved and stored in a powdered polymer flocculant and added to sludge or wastewater in the form of an aqueous solution. However, it takes time to dissolve the powdered polymer flocculant. Therefore, it is difficult to adjust the type of the flocculant even though the addition amount of the aqueous solution is not adjusted yet.
For example, in Patent Document 1, as a water treatment method in which an inorganic flocculant is added to raw water and then a polymer flocculant is added to form a floc and then subjected to filtration treatment, according to the filtration characteristics of the raw water after floc formation Thus, a treatment method for controlling the addition amount of the flocculant is shown, and this method can be applied to sludge treatment. However, only the addition amount of the flocculant is adjusted by this treatment method, and it is difficult to cope with the sludge treatment with large property fluctuations only by adjusting the addition amount of the flocculant.

Various methods have been proposed to deal with such problems.
For example, Patent Documents 2 and 3 disclose a method of dewatering sludge using a flocculant obtained by blending a cationic flocculant and an amphoteric flocculant. Patent Document 4 discloses a method of dewatering sludge using a flocculant composed of two or more amphoteric polymers having different ion equivalents. These methods may be applicable to a wide variety of sludges compared to the case where a single flocculant is used.
Patent Document 5 discloses a method in which two types of cationic flocculants having different cation degrees are dissolved separately, and each solution is added at a ratio that gives a cation degree suitable for sludge aggregation. ing.
JP 2004-25109 A Japanese Patent No. 2933627 Japanese Patent No. 3183809 JP 2002-177706 A JP-A-57-63200

However, in the methods described in Patent Documents 2 to 4, a flocculant obtained by blending a plurality of flocculants at a specific ratio in advance is used, so that it cannot sufficiently cope with fluctuations in sludge properties. Therefore, in order to cope with the sludge property variation, it is necessary to prepare flocculants having various blend ratios and use them according to the property variation.
Further, in the method described in Patent Document 5, since the amount of both coagulants used varies depending on the use ratio of the solution, the retention time of the solution of the coagulant with a small amount of use is extended, and the performance of the coagulant deteriorates. There's a problem. For this reason, it is difficult to extremely change the use ratio of each solution, and there is a limit to the response to sludge property fluctuations. Moreover, there is a problem that the equipment becomes large, such as the need for two dissolution tanks for dissolving and holding the respective flocculants, which is not practical.
The present invention has been made in view of the above circumstances, and is capable of widely dealing with fluctuations in the properties of sludge or wastewater, has little deterioration of the flocculant, and has excellent practicality. It aims to provide a method.

The first aspect of the present invention for solving the above problems is a method for coagulating and dewatering sludge by adding a flocculant aqueous solution containing a flocculant to sludge,
The sludge is sludge whose properties vary with time,
Two or more storage tanks for independently storing two or more kinds of powdery polymer flocculants, a feeder with adjustable feed amount connected to the storage tank, a mixing tank equipped with a water supply pump, and filtration Using a continuous dissolution supply device equipped with members,
Addition of the two or more kinds of powdery polymer flocculants by observing the properties of the sludge and setting the supply amount of the feeder connected to the two or more storage tanks according to the variation of the properties The amount is adjusted independently, and a powdery polymer flocculant supplied to the mixing tank through the feeder is mixed with water in the mixing tank to prepare a dispersion, and the dispersion is filtered through the filter member. Preparing the aqueous flocculant solution by passing it through ;
The sludge coagulation dewatering method is characterized in that an average residence time from dissolution of the powdery polymer flocculant to addition of the flocculant aqueous solution to the sludge is within 3 hours .
A second aspect of the present invention is a method for coagulating and precipitating wastewater by adding a flocculant aqueous solution containing a flocculant to wastewater,
The waste water is waste water whose properties vary with time,
Two or more storage tanks for independently storing two or more kinds of powdery polymer flocculants, a feeder with adjustable feed amount connected to the storage tank, a mixing tank equipped with a water supply pump, and filtration Using a continuous dissolution supply device equipped with members,
Addition of the two or more powdery polymer flocculants by observing the properties of the wastewater and setting the supply amount of the feeder connected to the two or more storage tanks according to the variation of the properties The amount is adjusted independently, and a powdery polymer flocculant supplied to the mixing tank through the feeder is mixed with water in the mixing tank to prepare a dispersion, and the dispersion is filtered through the filter member. Preparing the aqueous flocculant solution by passing it through ;
The method for coagulating and precipitating wastewater , wherein an average residence time from dissolution of the powdery polymer flocculant to addition of the aqueous flocculant solution to the wastewater is 3 hours or less .

  The sludge coagulation dewatering treatment method and waste water coagulation sedimentation treatment method of the present invention can cope with a wide variety of properties of sludge or waste water, have little deterioration of the coagulant, and are excellent in practicality. That is, when preparing an aqueous flocculant solution containing two or more kinds of flocculants, at least two kinds of powdery polymer flocculants are used as flocculants, and each of these powdery polymer flocculants is added independently. The amount and ratio of the various polymer flocculants in the aqueous flocculant solution are always adjusted to the optimum conditions most suitable for sludge flocculation and dewatering or waste water flocculation and precipitation. Can do. In addition, since the polymer flocculant is held in powder form and dissolved at the time of use, the performance of the flocculant is small and it can respond quickly to sudden changes in sludge or wastewater. It is unnecessary and highly practical.

Hereinafter, the present invention will be described in more detail.
The sludge coagulation dehydration method of the present invention is a method of adding a flocculant aqueous solution containing a flocculant to sludge.
Moreover, the coagulation sedimentation processing method of the waste water of this invention is a method of adding the coagulant aqueous solution containing a coagulant to waste water.
Hereinafter, these may be collectively referred to as the processing method of the present invention.
The aqueous flocculant solution is prepared by adjusting the addition amount of at least two powdery polymer flocculants, mixing and dissolving the powdery polymer flocculant and water. By adjusting the addition amount of two or more kinds of powdery polymer flocculants to prepare the flocculant aqueous solution, it is possible to easily cope with a wide range of properties of sludge or wastewater. Further, as the polymer flocculant, in general, powders, liquids, emulsions and the like are commercially available. However, the powdery polymer flocculants are in comparison with liquids and emulsions. The storage stability is good and the performance is not easily deteriorated during storage. Moreover, since the time of a solution state can be shortened by melt | dissolving and using a powdery polymer flocculant at the time of use, degradation of the performance of flocculant aqueous solution can be suppressed. Furthermore, since it is a powder, there are also advantages such as low transportation costs and less space required for storage.

As the powdery polymer flocculant, any one of powdery polymer flocculants conventionally used for the coagulation and dehydration treatment of sludge or waste water can be used.
There is no restriction | limiting in particular as an average particle diameter of the powdery polymer flocculent to be used. Considering the solubility in water, the average particle size is preferably 50 to 3000 μm, more preferably 100 to 2000 μm.

As the polymer flocculant, there are cationic, anionic, nonionic and amphoteric, and any of them can be used in the present invention.
Cationic polymer flocculants include (co) polymer of acryloyloxyethyltrimethylammonium chloride, (co) polymer of methacryloyloxyethyltrimethylammonium chloride, (co) polymer of (meth) acryloyloxyethylbenzyldimethylammonium chloride Examples thereof include acryloyl cationic polymer flocculants such as coalescence, amidine cationic polymer flocculants such as polyamidine, and polyvinylamine.
Examples of anionic polymer flocculants include copolymers of acrylamide and acrylic acid (salt), copolymers of acrylamide and acrylamide-2-methylpropanesulfonic acid, acrylamide, acrylate and acrylamide-2-methylpropanesulfone. Examples include acid copolymers.
Examples of nonionic polymer flocculants include acrylamide polymers.
Examples of amphoteric flocculants include (meth) acryloyloxyethyltrimethylammonium chloride-acrylamide-acrylic acid ternary or quaternary copolymers.

  Further, the molecular weight of the polymer flocculant is not particularly limited. There are various types of high molecular flocculants, including high molecular weight types having a molecular weight of 10 million or more and relatively low molecular weight types having a molecular weight of several millions, but the present invention is effective for both. The higher the molecular weight, the longer the time required for dissolution of the polymer flocculant. However, in the present invention, even a polymer having a high molecular weight can be dissolved quickly, and an undissolved portion called Mamako is not left.

The combination of two or more kinds of powdery polymer flocculants used in the present invention is not particularly limited as long as their properties such as molecular structure, molecular weight, ionicity and the like are not identical.
Specific combinations include, for example, combinations of two or more cationic polymer flocculants, combinations of cationic polymer flocculants and amphoteric polymer flocculants, anionic polymer flocculants and cationic polymer flocculants. A combination, a combination of an anionic polymer flocculant and an amphoteric polymer flocculant, and the like can be mentioned. Further, a combination of a high molecular weight type polymer flocculant and a relatively low molecular weight type polymer flocculant may be mentioned.
As a combination of two or more kinds of cationic polymer flocculants, more specifically, a low cationic high molecular weight type polymer flocculant having a low cationic degree and a high molecular weight type, and a high cationic degree and low molecular weight type. And a combination of a high cationic low molecular weight type polymer flocculant and a combination of an acryloyl cationic polymer flocculant and an amidine cationic polymer flocculant.
Moreover, as a combination of a cationic polymer flocculant and an amphoteric polymer flocculant, a combination of two or more cationic polymer flocculants as described above and an amphoteric polymer flocculant, an amphoteric system Examples include a combination of a flocculant and an amidine-based cationic polymer flocculant, a combination of two or more amphoteric polymer flocculants having different compositions, and the like, but are not limited to these combinations. Moreover, you may combine a 3rd component with 2 or more types of flocculants mix | blended previously.

What is necessary is just to determine these combinations suitably in consideration of the kind and property of sludge or wastewater which are treatment objects.
For example, when the sludge is an organic sludge containing an organic substance, a combination of two or more cationic polymer flocculants, or a combination of a cationic polymer flocculant and an amphoteric polymer flocculant is particularly preferable.
Specific examples of combinations include, for example, a combination of a methacryloyl cationic polymer flocculant and an amidine cationic polymer flocculant for dewatering of sewage mixed sludge (mixed sludge of primary sludge and excess sludge) with a belt press dehydrator. Is preferred. When the mixing ratio of the initial settling sludge is high, the drainage speed is large, the methacryloyl-based cationic flocculant with good releasability from the filter cloth is increased, and the mixing ratio of the excess sludge that is difficult to dehydrate becomes high. By increasing the ratio of the amidine flocculant having a low viscosity of the polymer and a high cation density, it is possible to maintain good drainage and the like. Moreover, since an effective amidine type flocculant is not used excessively, it is economically excellent.

The properties of sludge to be considered at the time of combination are usually properties to be considered when selecting a polymer flocculant to be added to sludge, for example, moisture content of sludge, floc diameter at the time of aggregation, drainage speed at the time of dehydration The moisture content of a dehydrated cake is mentioned.
Properties of wastewater to be considered in combination usually include properties to be considered when selecting a polymer flocculant to be added to the wastewater, such as turbidity of wastewater, SS content, and PH.
By observing these properties, the amount of powdered polymer flocculant added, etc., so that the composition of the flocculant aqueous solution (type of flocculant and blending ratio) is the composition that exhibits the most flocculating effect (optimum composition). Adjust.

In preparing the flocculant aqueous solution, a liquid or emulsion polymer flocculant may be added in addition to the powdered polymer flocculant.
Moreover, you may add to the coagulant | flocculant aqueous solution the arbitrary inorganic coagulants conventionally used for the coagulation dehydration process of sludge, or the coagulation sedimentation process of wastewater. Examples of such inorganic flocculants include sulfuric acid band, polyaluminum sulfate, ferrous sulfate, ferric chloride, and polyferric sulfate.
Further, when an amphoteric polymer flocculant or an anionic polymer flocculant is used, an acid or the like for adjusting the pH may be blended in order to increase the solubility thereof.

  In the flocculant aqueous solution, the concentration of the polymer flocculant (the total of the powdered polymer flocculant and the liquid or emulsion polymer flocculant optionally added) is preferably 0.5% by mass or less. A concentration of 05 to 0.5% by mass is more preferable. If the concentration exceeds 0.6% by mass, the liquid viscosity is too high, and the miscibility with sludge or wastewater may be reduced. When the concentration of the polymer flocculant is low, the polymer flocculant is more likely to deteriorate.

In the present invention, in order to prevent deterioration of the performance of the powdery polymer flocculant, the average residence time from the dissolution of the powdery polymer flocculant to the addition of the flocculant aqueous solution to sludge or waste water, It is preferably 3 hours or shorter, more preferably 10 seconds or longer and 1 hour or shorter, and further preferably 1 minute or longer and 30 minutes or shorter. When the average residence time exceeds 3 hours, the polymer flocculant may be greatly deteriorated. The deterioration of the polymer flocculant is considered to have occurred from the initial stage of dissolution.
Here, “average residence time” refers to the time from the start of dissolution of the powdery polymer flocculant to the start of addition of the prepared flocculant aqueous solution to sludge or wastewater, It is the average time from the start of dissolution of the molecular flocculant to the end of the addition of the flocculant aqueous solution to sludge or wastewater. The powdery polymer flocculant is added to water at a substantially constant rate (unit: volume / hour). When a continuous melting facility is used, it is the residence time in the apparatus, and can be calculated by dividing the hold-up amount of the melting apparatus, supply line, etc. by the flow rate per unit time.
In the case of the conventional batch type, the average residence time can be shortened by reducing the amount of dissolution for each batch, but the operation tends to be complicated.
In order to shorten the dissolution time of the polymer flocculant, it is necessary to reduce the particle size of the powdered polymer flocculant to increase the dissolution rate, and to reduce the storage tank after dissolution to shorten the average residence time. There is.

In the treatment method of the present invention, it is preferable to use a continuous dissolution supply apparatus for the preparation and supply of the flocculant aqueous solution. The continuous dissolution and supply apparatus has few restrictions as described above and is suitable for an industrial scale.
Here, the continuous dissolution supply device is not particularly limited, but it is preferable to use a device capable of rapidly dissolving the powdery polymer flocculant in order to reduce the deterioration of the flocculant. The type of the apparatus is not limited as long as the powdery polymer flocculant can be dissolved quickly. For example, the apparatus shown in Japanese Patent Nos. 3184729 and 318497 is available. Praised. The apparatus has a merit that the powdered polymer flocculant is dispersed and swollen in water, the swollen gel is rubbed against a mesh-like filter member, the gel is refined and dissolved, and the flocculant is less dissolved and degraded.

  The treatment method of the present invention particularly comprises two or more storage tanks for independently storing two or more kinds of powdery polymer flocculants, a feeder with adjustable feed amount connected to the storage tank, and water supply Using a device provided with a mixing tank equipped with a pump and a filtration member, the powdery polymer flocculant stored in the storage tank is supplied to the mixing tank via a feeder, and water and water are contained in the mixing tank. It is preferable to prepare a dispersion by mixing and preparing the aqueous flocculant solution by passing the dispersion through a filter member.

The filter member preferably has an opening of 10 to 500 μm, and more preferably 50 to 200 μm. If the mesh size exceeds 500 μm, the dissolution efficiency of the polymer flocculant decreases, and if it is less than 10 μm, it takes time for filtration and excessive force is applied to the polymer flocculant during filtration, and the polymer flocculant tends to deteriorate.
The material of the filter member is not particularly limited as long as it is a material that can withstand the pressure when the dispersion is passed, but usually a wire mesh is used. Further, the filtering member may be a single layer or a multilayer, but a multilayer is preferable in terms of strength. In the case of multiple layers, several layers with the same opening may be stacked, or layers with different opening may be stacked.
The speed at which the dispersion is passed through the filter member (filtration speed) is preferably 1 m ³ / min or less per 1 m ² of the filtration surface of the filter member, although it depends on the method of applying pressure to the dispersion. If the filtration rate is 1 m ³ / min or less per 1 m ² of the filtration surface of the filtration member, the polymer flocculant can be further prevented from deteriorating, but if it exceeds 1 m ³ / min per 1 m ² , it tends to deteriorate.
When the dispersion is passed through the filter member, a flow resistance is generated, and therefore pressure may be applied to the dispersion. Examples of the method of applying pressure include a method of pressing the dispersion liquid with a sliding plate or roller onto a cylindrical filtration member having a net-like peripheral surface.

An example of the processing method of the present invention using such an apparatus will be described with reference to FIG.
1 has a hopper (storage tank) 2 for storing a powdery polymer flocculant A and a hopper 3 for storing a powdered polymer flocculant B. Are respectively equipped with feeders 4 and 5 capable of adjusting the supply amount, and the powdery polymer flocculants A and B in the hoppers 2 and 3 can be supplied to the mixing tank 6 while adjusting the supply amount. It is like that.
The supply amount of each powdery polymer flocculant can be adjusted independently by setting the supply amount with the feeders 4 and 5. The supply amount may be set manually, or some physical property of the sludge or waste water or the liquid after the coagulation treatment is measured, and the setting may be automatically changed based on the physical property value.
When adjusting manually, the floc diameter during sludge aggregation, drainage speed during dehydration, moisture content of dehydrated cake, etc., or turbidity of wastewater, SS content, PH, etc. are observed, which is optimal for treatment. The amount of both coagulants added is adjusted so that the composition is obtained. In the case of automatic control, the above items are automatically measured and controlled based on the result.

  In the mixing tank 6, a stirring device 6a is disposed. In addition, a water supply pump (not shown) for supplying water is attached to the mixing tank 6, and water is supplied from the water supply pump through the water supply line 14 and supplied to the water by the feeders 4 and 5. The powdery polymer flocculants A and B are supplied while adjusting the viscosity, and the powdered polymer flocculant is swollen by stirring and mixing to prepare a dispersion containing the flocculant.

The continuous dissolution supply apparatus 1 further includes a cylindrical outer portion 7, a cylindrical filter 8 accommodated in the outer portion 7, a sliding plate 9 disposed in the filter 8, and the sliding plate And a filtering device 11 having a motor 10 for sliding 9. The mixing tank 6 and the filtration device 11 are connected to each other by a dispersion feed line 12, and the dispersion is supplied to the inside of the filter 8 by the dispersion feed line 12. By passing the dispersion thus supplied through the filter 8, an aqueous flocculant solution is obtained.
At this time, the undissolved flocculant in the dispersion does not pass through the filter 8, but by sliding the sliding plate 9, the dispersion is pressed against the filter 8, and the undissolved flocculant and water are efficiently used. Because it mixes well and swells, the flocculant can be dissolved quickly. Conventionally, it took a long time to dissolve the powdery polymer flocculant, and the deterioration of the aqueous flocculant solution was large. By using such an apparatus, the powdery polymer flocculant can be rapidly dissolved. Deterioration of the aqueous solution can be reduced.

Furthermore, in the continuous dissolution supply apparatus 1, an aqueous solution feed line 13 is connected between the outer portion 7 of the filtration apparatus 11 and the filter 8, and a pump (not shown) is attached to the aqueous solution feed line 13. Thus, the obtained flocculant aqueous solution can be continuously supplied to the sludge or waste water flocculation treatment tank.
According to such a continuous dissolution and supply apparatus, the deterioration of the flocculant can be further prevented, and a large-scale sludge treatment or wastewater treatment can be performed.

By adding and mixing the flocculant aqueous solution obtained as described above to sludge or wastewater, solids in the sludge or wastewater can be agglomerated. The agglomerated sludge is dehydrated with a dehydrator or the like. Moreover, about the wastewater which solid content aggregated and settled, the solid content separation process by gravity is performed.
There is no restriction | limiting in particular in the form of the dehydrator used for the dehydration of sludge, A press dehydrator, a centrifugal dehydrator, a multiple disk type dehydrator etc. are illustrated.

  There is no restriction | limiting in particular in the sludge and waste water used as the object of the processing method of this invention. Since the treatment method of the present invention can respond widely to changes in the properties of sludge or wastewater, for example, in mixed raw sludge where the mixing ratio of primary sludge and surplus sludge is changed, or in a relatively small treatment plant where sludge is extracted intermittently. For sludge whose degree of decay of sludge changes depending on the drawing time, sludge whose degree of corruption changes depending on the season, sludge generated by treatment of wastewater whose concentration changes greatly due to inflow of rainwater, wastewater whose pH varies, etc. The utility of the treatment method is remarkable.

In addition, in the said continuous melt | dissolution supply apparatus 1, although the number of a storage tank and a feeder is 2, this invention is not limited to this, It is good also as 3 or more.
In addition, the continuous dissolution and supply apparatus 1 includes a number of storage tanks and feeders according to the type of the powdery polymer flocculant, one mixing tank 6, and one filtration apparatus 11. If necessary, a plurality of mixing tanks 6 and filtration devices 11 may be provided. Since it is easy to save space, it is easiest to use an apparatus including a number of storage tanks and feeders according to the type of the powdery polymer flocculant, one mixing tank 6 and one filtration device 11. It is.
Furthermore, in the present invention, when there is no restriction on the place or the like, two or more continuous dissolution and supply apparatuses as described above may be used, and after preparing the flocculant aqueous solution independently of each other, they may be line mixed. Further, a variety of flocculant aqueous solutions may be line-mixed by using a plurality of continuous dissolution and supply apparatuses as described above and a plurality of apparatuses capable of freely mixing and dissolving a single or a plurality of flocculants.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to this range as long as the gist of the present patent is not exceeded.
Example 1
Using the continuous dissolution and supply apparatus 1 shown in FIG. 1, the sludge generated at the A treatment site (oxidation ditch) was treated. As the filter 8, a mesh plate (100 micron opening) was used.
In the hopper 2 of the continuous dissolution and supply apparatus 1, KP7000 (powdered cationic polymer flocculant (polyamidine type), cation equivalent 6 meq / g, molecular weight 3 million) as a flocculant A, powder form as flocculant B Equipped with amphoteric polymer flocculant (acryloyloxyethyltrimethylammonium chloride / acrylamide / acrylic acid = 27.0 / 44.0 / 29.0 (mol%) copolymer, molecular weight 4 million) went.
September 24: Prepare a 0.2% by weight aqueous flocculant solution by dissolving powdery polymer flocculant in a blend ratio of flocculant A / flocculant B = 75/25 (mass%) in water. The flocculant aqueous solution was added to the sludge in an amount of 200 mg / L of the flocculant, and the sludge was dehydrated using a centrifugal dehydrator. The dehydration performance was the best at the start of operation, and the moisture content of the sludge after dehydration was 83.9%.
After operating for several days as it was, the sludge moisture content increased to 85.6% (dehydration performance decreased), so the blend ratio was adjusted to 50/50 (mass%) (concentration was the same). Dropped to 84%.
Furthermore, since the increase in moisture content was observed again on November 12, the blend ratio was set to 60/40, and by November 15, the blend ratio was changed from 60/40 to 70/30 (mass%). (Concentration is the same). During this time, the moisture content of the sludge was 83.2%.
As a result of adjusting the blend ratio as described above from September 24 to November 15, the average water content of the treated sludge was 84.5%.
In the above treatment, an aqueous flocculant solution within 3 hours after dissolving the powdery polymer flocculant in water was used.

Comparative Example 1
In the treatment plant A, the same apparatus and flocculant as in Example 1 were used, and a flocculant A / coagulant B = 50/50 flocculant aqueous solution (concentration 200 mg / L) was used for one month from 11/17 days. When the sludge treatment was performed without changing the blend ratio, the moisture content of the sludge treated for 1 month from 11/17 changed within the range of 84.2% to 88.2%. The average was 86.1%.

Example 2
B Purification Center (Oxidation Ditch) for 10 days, using the same apparatus as in Example 1, with KP7000 manufactured by Daianitrix Co. as flocculant A and powdered amphoteric polymer flocculant (methacryloyloxyethyltrimethylammonium chloride / Using acrylamide / acrylic acid = 18.6 / 71.3 / 10.1 (mol%) copolymer, molecular weight 4 million), blending the blend ratio so that the water content of the cake after dehydration is the lowest When the sludge treatment was performed by sequentially changing the agent A / flocculant B = 60/40 to 70/30, the average water content of the sludge treated for 10 days was 81%.

Comparative Example 2
At the B purification center for 5 days, using the same apparatus and flocculant as in Example 2, flocculant A / flocculant B = 60/40 0.2% flocculant aqueous solution (concentration 200 mg / L), blend ratio When the sludge treatment was performed without change, the average moisture content of the sludge treated for 5 days was 82.8%.

Example 3
In the C treatment plant (mixed raw sludge), the same apparatus as in Example 1 was used. The coagulant A was KP201G (powdered cationic polymer coagulant, methacryloyloxyethyltrimethylammonium chloride 100%), coagulant. B was subjected to sludge treatment using KP7000 manufactured by Dianitics.
For mixed raw sludge having a composition of initial settling sludge / surplus sludge = 60/40 (mass ratio), it is best when the treatment is performed with coagulant A / coagulant B = 100/0. The rate was 78.4%.
Next, with regard to the mixed raw sludge having the composition of the initially settled sludge / excess sludge = 20/80 (mass ratio), the treatment was performed with the coagulant A / coagulant B = 75/25 (mass ratio). The average water content of the sludge was 79.1%.

Comparative Example 3
When the sludge was processed using only the flocculant A under the same conditions as in Example 3, the water content was 82% on average.

  From the above results, Examples 1 to 3 in which the blend ratio was changed by adjusting the addition amount of the powdery polymer flocculant according to the change in the composition such as the moisture content of the sludge and the initial sludge / excess sludge ratio, The water content was low and the dehydration efficiency was high.

Example 4
The treatment of D paper mill wastewater sludge in which the SS content in the sludge was 2.5% and the ratio of the fiber content in the sludge SS content was varied in the range of 10% to 35% was carried out according to the following procedure.
Using the same apparatus as in Example 1 for 5 days, the powdery cationic polymer flocculant (acryloyloxyethyltrimethylammonium chloride / acrylamide = 30/70 (mol%) copolymer, molecular weight 5 million) was used as flocculant A. ), Powdery amphoteric polymer flocculant (copolymer of acryloyloxyethyltrimethylammonium chloride / acrylamide / acrylic acid = 25.0 / 50.0 / 25.0 (mol%), molecular weight 4 million) These flocculants are mixed at the following mixing ratio so that optimum processing is possible according to the ratio of the fiber content in the SS content of sludge (fiber content / SS, mass%), and the solid content A polymer flocculant dissolved in water so as to have a concentration of 0.2% by mass was added to the sludge, and after mixing, dehydration was performed with a screw press dehydrator. As a result, when the amount of the polymer flocculant added was 60 ppm, the moisture content of the cake after dehydration was 65% or less, and it was possible to maintain an SS-free leak from the dehydrator for 5 days.
Fiber content / SS: 10% or more and less than 25%: flocculant A / flocculant B = 70/30 (mass ratio)
Fiber content / SS: 25% or more and 35% or less: Coagulant A / Coagulant B = 95/5 (mass ratio)

Comparative Example 4
For the same sludge as in Example 4, as the polymer flocculant, flocculant A alone or a mixture in which the blend ratio is fixed to flocculant A / flocculant B = 70/30 (mass ratio) is used. When dehydration was performed, stable dehydration was not obtained as shown below.
[Example where polymer flocculant is flocculant A alone]
When the sludge fiber content / SS is 25 to 35%, the polymer flocculant addition amount was 60 ppm, and the dehydration was good, but when the fiber content / SS was 10 to 24%, the polymer flocculant addition amount was 40 to 100 ppm. In the range of, SS outflow from the dehydrator occurred.
[Example in which polymer flocculant is flocculant A / flocculant B = 70/30]
・ When the sludge fiber content / SS is 10 to 24%, the polymer flocculant addition amount was 60 ppm, and the dehydration was good, but when the fiber content / SS was 25 to 35%, the polymer flocculant addition amount was 90 ppm. The cake moisture content could not be maintained at 65% or less unless the content was increased up to.

Example 5
A paper mill wastewater having the following properties, in which the pH before addition of the polymer flocculant fluctuates in the range of 5.7 to 7.2, was treated according to the following procedure.
[Properties of wastewater]
-SS content: 1400-1500ppm
・ Sulfuric acid band addition amount: 70ppm
-PH fluctuation: 5.7-7.2
Using the same apparatus as in Example 1, flocculant A was powdered low anionic polymer flocculant (acrylamide / sodium acrylate = 95.0 / 5.0 (mol%) molecular weight 10 million), flocculant B Using anionic polymer flocculants in powder form (acrylamide / sodium acrylate = 88.0 / 12.0 (mol%) molecular weight 10 million), these flocculants can be used in order to obtain optimum flocculation. Depending on the pH, mixed at the mixing ratio shown below, the polymer flocculant dissolved in water to a solid content concentration of 0.1% by mass was added to the waste water to a concentration of 0.6 ppm, after mixing, Aggregation precipitation treatment was performed.
The pH of the wastewater is 5.7 to 6.1: flocculant A / flocculant B = 90/10 (mass ratio)
PH of waste water is 6.2 to 6.6: flocculant A / flocculant B = 50/50 (mass ratio)
PH of waste water is 6.7 to 7.2: flocculant A / flocculant B = 10/90 (mass ratio)
As a result, a stable coagulation sedimentation treatment could be maintained. For example, a part of waste water immediately after mixing is collected, and a floc settling time (time until no floc settling is observed) is measured with a jar tester (product name: Jar tester MJS-4P; manufactured by Miyamoto Seisakusho Co., Ltd.) The turbidity of the supernatant of the waste water after the sedimentation time was measured (after coagulation sedimentation) was measured with a turbidimeter (product name: Turbidimeter 2100N; manufactured by Central Science Co., Ltd.). The turbidity was 50 NTU or less.

Comparative Example 5
For the same waste water as in Example 5, as a polymer flocculant, flocculant A or B alone or a mixture in which the blend ratio is fixed to flocculant A / flocculant B = 50/50 (mass ratio) is used. When the coagulation sedimentation treatment was performed, the following problems occurred.
When flocculant A was used alone, the turbidity of the supernatant after coagulation sedimentation was large in waste water of pH 6.2 or higher (for example, in the case of waste water of pH 7.2, the sedimentation time was within 30 seconds and the turbidity was 110 NTU. there were).
When flocculant B was used alone, the floc sedimentation time was long in wastewater having a pH of 6.6 or less (for example, in the case of wastewater having a pH of 5.7, the sedimentation time was 60 seconds and the turbidity was 50 NTU or less).
When a mixture of flocculant A / flocculant B = 50/50 was used, the sedimentation time of floc was increased in the region of pH 5.7 to 6.1 (for example, in the case of wastewater at pH 5.7, the sedimentation time was 47 Second, turbidity was less than 50 NTU). Moreover, the turbidity of the supernatant after coagulation sedimentation became large in the region of pH 6.7 to 7.2 (for example, in the case of pH 7.2 wastewater, the sedimentation time was within 30 seconds and the turbidity was 80 NTU).

It is the schematic of the continuous melt | dissolution supply apparatus used suitably for this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Continuous melt | dissolution supply apparatus, 2 ... Hopper, 3 ... Hopper, 4 ... Feeder, 5 ... Feeder, 6 ... Mixing tank, 7 ... Outer part, 8 ... Filter, 9 ... Sliding plate, 10 ... Motor, 11 ... Filtration Apparatus 12 ... Dispersion feed line 13 ... Aqueous solution feed line 14 ... Water supply line

Claims (5)

A method for coagulating and dewatering sludge, wherein a flocculant aqueous solution containing a flocculant is added to sludge,
The sludge is sludge whose properties vary with time,
Two or more storage tanks for independently storing two or more kinds of powdery polymer flocculants, a feeder with adjustable feed amount connected to the storage tank, a mixing tank equipped with a water supply pump, and filtration Using a continuous dissolution supply device equipped with members,
Addition of the two or more kinds of powdery polymer flocculants by observing the properties of the sludge and setting the supply amount of the feeder connected to the two or more storage tanks according to the variation of the properties The amount is adjusted independently, and a powdery polymer flocculant supplied to the mixing tank through the feeder is mixed with water in the mixing tank to prepare a dispersion, and the dispersion is filtered through the filter member. Preparing the aqueous flocculant solution by passing it through ;
A sludge coagulation dewatering method , wherein an average residence time from dissolution of the powdery polymer flocculant to addition of the flocculant aqueous solution to the sludge is within 3 hours . The two or more powdery polymer flocculants are a combination of two or more cationic polymer flocculants, a combination of a cationic polymer flocculant and an amphoteric polymer flocculant, an anionic polymer flocculant and an amphoteric polymer flocculant. The method for coagulating and dewatering sludge according to claim 1, which is a combination of molecular flocculants or a combination of two or more anionic polymer flocculants. The two or more powdery polymer flocculants are a combination of two or more cationic polymer flocculants, or a combination of a cationic polymer flocculant and an amphoteric polymer flocculant,
The method for coagulating and dewatering sludge according to claim 2 , wherein the cationic polymer flocculant is an acryloyl cationic polymer flocculant or an amidine cationic polymer flocculant. A method for coagulating and precipitating wastewater by adding an aqueous flocculant solution containing a flocculant to wastewater,
The waste water is waste water whose properties vary with time,
Two or more storage tanks for independently storing two or more kinds of powdery polymer flocculants, a feeder with adjustable feed amount connected to the storage tank, a mixing tank equipped with a water supply pump, and filtration Using a continuous dissolution supply device equipped with members,
Addition of the two or more powdery polymer flocculants by observing the properties of the wastewater and setting the supply amount of the feeder connected to the two or more storage tanks according to the variation of the properties The amount is adjusted independently, and a powdery polymer flocculant supplied to the mixing tank through the feeder is mixed with water in the mixing tank to prepare a dispersion, and the dispersion is filtered through the filter member. Preparing the aqueous flocculant solution by passing it through ;
A method for coagulating and precipitating wastewater , wherein an average residence time from dissolution of the powdery polymer flocculant to addition of the aqueous flocculant solution to wastewater is within 3 hours . The two or more powdery polymer flocculants are a combination of two or more cationic polymer flocculants, a combination of a cationic polymer flocculant and an amphoteric polymer flocculant, an anionic polymer flocculant and an amphoteric polymer flocculant. The method for coagulating and precipitating wastewater according to claim 4, which is a combination of molecular flocculants or a combination of two or more anionic polymer flocculants.

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