JP6886426B2 - Dehydration method of organic sludge and treatment equipment used for this - Google Patents

Description

The present invention relates to a method for dehydrating organic sludge and a treatment apparatus used for the method.

In recent years, there has been a demand for reduction of the amount of waste and reuse of waste. Organic sludge is usually treated as waste after dewatering, but insufficient dewatering affects the amount generated and subsequent processes. Therefore, it is desired to develop an efficient and effective method for dehydrating organic sludge.

As a method for dehydrating organic sludge, a method of coagulating sludge with a polymer flocculant and then mechanically dehydrating it (referred to as a "one-component method") or a method of coagulating sludge with a polymer flocculant is performed. , A method of mechanically dehydrating by adding a polymer flocculant to sludge dehydrated by gravity concentration (referred to as "polymer coagulant two-component addition method"), a dehydration aid such as an inorganic flocculant or an organic coagulant. Is generally added to sludge and then agglomerated with a polymer flocculant to perform mechanical dehydration (referred to as "inorganic coagulant or organic coagulant / pre-addition method").

As a method of dehydrating sludge by a centrifugal dehydrator, sludge and a polymer flocculant are supplied into the dehydrator to aggregate sludge particles, and an inorganic coagulant is added in the process of centrifugal dehydration to perform centrifugal dehydration and solid-liquid separation. A method (referred to as "in-flight two-component tempering method") is known.

In recent years, as another dehydration method for organic sludge, after aggregating sludge with a polymer flocculant, the aggregated sludge is gravity-concentrated, and a dehydration aid such as an inorganic coagulant or an organic coagulant is added to the sludge. , A method of performing mechanical dehydration (referred to as "inorganic flocculant or organic coagulant / post-addition method") has been proposed.

On the other hand, in the process of dehydrating organic sludge, especially when an inorganic flocculant is added, the concentration of soluble calcium and the concentration of sulfate ions in the sludge and the dehydration filtrate become high, so gypsum scale is applied to the dehydrator and surrounding piping. Is generated. Since the gypsum scale adheres strongly, it requires a lot of labor to remove and clean.

Patent Document 1 describes a step of adding and stirring a cationic polymer flocculant I, a step of solid-liquid separation of agglomerated sludge by gravity, and a polymer flocculant having a stronger cation strength than the polymer flocculant I in a dehydrated cake. A method for dehydrating organic sludge, which comprises a step of adding and stirring II and a step of mechanically dehydrating, is disclosed.

Further, there is a description that the cationic strength of the cationic polymer flocculant II is preferably 3.5 or 5.0 meq / g or more, and in the example, a polyamine-based polymer flocculant is used.

In Patent Document 2, as a method for dehydrating sludge, sludge and a high-molecular-weight cationic polymer flocculant are stirred and mixed at a slow speed in a first treatment tank to aggregate the sludge into coarse flocs. Coarse flock-like sludge is sent to a gravity dehydrator to concentrate, and the obtained concentrated sludge and a high cationic polymer flocculant are sufficiently stirred and mixed in a second treatment tank to further agglomerate the sludge, and then the sludge is further aggregated. A method of supplying this coagulated sludge to a mechanical dehydrator to dehydrate it is described.

Patent Document 3 describes a sludge dewatering method and an apparatus for a primary coagulation step in which a first coagulant is added to sludge to coagulate and generate a primary coagulation floc, and a primary coagulation floc is dehydrated to produce a primary coagulation floc. A primary dehydration step of obtaining a dehydrated cake, and a secondary flocculation step of adding a second flocculant composed of a dispersion or emulsion-state polymer flocculant to the primary dehydrated cake to coagulate and generate a secondary coagulation floc. And a method and apparatus including a secondary dehydration step of dehydrating the secondary aggregated floc.

Patent Document 4 describes a method for dehydrating organic sludge by adding a cationic organic polymer flocculant to organic sludge to mix and form flocs, and then adding an iron salt to the gravity-concentrated coagulated sludge. A method of pressure dehydration is described.

Patent Document 5 describes a method and apparatus for dehydrating organic sludge by adding a polymer flocculant to organic sludge to form agglomerated sludge and pressurizing the coagulated sludge to squeeze the coagulated sludge. A machine for mechanically dehydrating a dewatered cake to which an inorganic coagulant has been added, and a step of adding an inorganic coagulant to the dewatered cake formed in the coagulated sludge pressure dehydration step for dehydration, and a dewatering cake to which the inorganic coagulant has been added. The method performed by the dewatering step and the sludge squeezer used in the coagulated sludge pressurized dewatering step are described.

Patent Document 6 describes a method and apparatus for treating sludge, a mixed sludge preparation step of adding a solution of a first polymer flocculant to sludge and mixing the sludge to obtain mixed sludge, and a second polymer flocculant. It has a coagulation floc forming step of mixing a solution with the mixed sludge to form agglomerated sludge to obtain agglomerated sludge, and an inorganic coagulant / pre-addition step of adding an inorganic coagulant to the sludge before the mixed sludge preparation step. It describes how to treat sludge.

In Non-Patent Document 1, the method of dehydrating organic sludge and the properties of sludge after dehydration are described in a step of adding a polymer to the concentrated sludge of a urine facility in a granulation tank and a first dehydration step of agglomerated sludge using a belt press dehydrator. , A sludge dewatering method having a step of adding a polymer (organic coagulant, chitosan, etc.) to the dewatered sludge and a second dewatering step of the sludge added sludge by a screw press dewatering machine (dewatering by applying steam heat), and dewatering. The sludge properties after dehydration, such as the sludge moisture content of the cake being 65 wt% or less, are described.

Japanese Unexamined Patent Publication No. 58-223500 Japanese Unexamined Patent Publication No. 6-344000 JP-A-2002-192199 JP-A-61-149300 Japanese Unexamined Patent Publication No. 2013-712 Japanese Unexamined Patent Publication No. 2014-50830

Ebara Infilco Time Signal, No. 88, 1983, pp. 41-49

However, Patent Document 1 aims only at the effect of reducing the water content, and no consideration is given to the prevention of scale generation and no measures are taken. In addition, the organic coagulant is not specified, and various conditions regarding the viscosity, molecular weight, step of making a diluted solution, and dilution ratio are not described.

Patent Document 2 aims to prevent a device from shortening its life due to corrosion of a dehydrator or the like, and does not aim to reduce the water content and suppress the formation of gypsum scale.

Patent Document 3 aims at lowering the water content of the dehydrated cake and high SS recovery rate, and does not aim at the effect of suppressing gypsum scale.

Patent Document 4 merely describes the addition of an inorganic coagulant (iron salt) to the coagulated sludge, and does not disclose the addition of an organic coagulant to the concentrated sludge.

In Patent Document 5, there is a possibility of producing gypsum scale by using an inorganic flocculant.

Patent Document 6 aims to reduce the injection amount of the polymer flocculant, reduce the water content of the dehydrated cake, and reduce the chromaticity of the dehydrated filtrate, and does not consider the effect of suppressing gypsum scale. In addition, there is a possibility of gypsum scale formation by using an inorganic flocculant.

Non-Patent Document 1 aims to reduce the water content of the dehydrated cake, and does not consider the effect of suppressing the formation of gypsum scale. In addition, mechanical dehydration is being studied only with a screw press dehydrator (partially using steel heat) and a belt press dehydrator, and other mechanical dehydration methods and devices and centrifugal dehydration methods and devices are not considered.

As described above, in the prior art, by adding a polymer flocculant or a dehydration aid to the organic sludge, the sludge water content reduction effect, the corrosion prevention effect of the dehydrator and the like, and the high SS recovery rate are aimed at. However, especially in the dehydration method in which an inorganic flocculant is added, the concentration of soluble calcium and the concentration of sulfate ions in the sludge are high, so that there is a problem that gypsum scale is generated in the dehydrator and the surrounding pipes. If gypsum scale is produced, it needs to be removed and cleaned. Further, as a method for concentrating agglomerated sludge, a gravity filtration method or the like is considered from the viewpoint of cost.

As described above, no method for dehydrating organic sludge has been reported in the conventional method, which can achieve the suppression of scale formation alone or the effect of reducing the water content of the dehydrated cake and the suppression of scale formation at the same time. In addition, if the water content of the concentrated sludge is high, the organic coagulant tends to disperse and permeate into the concentrated sludge, but the chemical tends to flow out to the filtrate side in the concentration step and dehydration step, and a large amount of organic coagulant is inevitably used. Must be used. In order to reduce the amount of organic coagulant used, there is a great need to reduce the water content of concentrated sludge.

Therefore, an object of the present invention is to provide a method for dehydrating organic sludge, which can achieve reduction in sludge water content, reduction in waste amount, and suppression of gypsum scale formation, and a treatment apparatus used for the method.

In order to solve the above problems, the present invention can have the following configuration.

(1) A step of adding a polymer flocculant to organic sludge to coagulate the organic sludge, and
The step of concentrating and pressurizing and dehydrating the agglomerated sludge, and
The step of adding an organic coagulant to the sludge after the concentration or the pressure dehydration, and
The step of mechanically dehydrating the sludge to which the organic coagulant is added is included.
The pH of at least one of the sludge to which the organic coagulant is added and the dehydrated filtrate thereof is 6 or more, and the evaporation residue (TS) of the concentrated and pressure-dehydrated sludge is 40 to 150 g / L. A method for dehydrating organic sludge.

(2) The organic coagulant has a cation degree of pH 4 of 5 meq / g or more.

(3) The organic coagulant is added after the sludge after the concentration and pressure dehydration is divided and formed into at least a block shape.

(4) The organic coagulant is a liquid having a viscosity of a stock solution of 50 mPa · s or more at 25 ° C.

(5) The organic coagulant has a molecular weight of more than 4000 and 1.5 million or less.

(6) The organic coagulant is added as a solution undiluted or diluted at a dilution ratio of 60 times or less.

(7) A coagulation means for coagulating the organic sludge by adding a polymer flocculant to the organic sludge.
Concentrating means for concentrating the agglomerated sludge and
A pressure dehydrating means for pressurizing and dehydrating the concentrated sludge,
An organic coagulant adding means for adding an organic coagulant to the sludge after the concentration or the pressure dehydration.
Includes a mechanical dewatering means for mechanically dewatering sludge to which the organic coagulant has been added.
At least one of the sludge to which the organic coagulant is added and the dehydrated filtrate thereof has a pH of 6 or more, and the evaporation residue (TS) of the concentrated and pressure-dehydrated sludge is 40 to 150 g / L. A treatment device used for dehydrating organic sludge, which is characterized by being present.

(8) A sludge dividing means provided between the concentrating / pressure dehydrating means and the organic coagulant adding means is provided to divide the concentrated / pressure dehydrated sludge to form at least a block shape.

According to the present invention, it is possible to reduce the water content of sludge, reduce the amount of waste, and suppress the formation of gypsum scale.

Flow chart showing the outline of the present invention Schematic diagram illustrating the processing apparatus of the first example Schematic cross-section of sludge squeezer Schematic diagram illustrating the processing apparatus of the second example The figure which shows the effect when the pressure concentrated sludge was divided and when it was not divided. Perspective view showing a dividing machine

Hereinafter, the present invention will be specifically described, but the present invention is not limited to a specific specific example.

FIG. 1 is a drawing for explaining the outline of the present invention. In the present invention, a step of adding a polymer flocculant to organic sludge to coagulate organic sludge, and concentration and addition of aggregated sludge. A step of pressure dehydration, a step of adding an organic coagulant to the sludge after concentration or pressure dehydration, and a step of mechanically dehydrating the sludge to which the organic coagulant is added are included, and finally the dehydrated sludge ( (Dehydrated cake) is discharged. This will be described in detail below.

[Organic sludge]
Organic sludge is organic sludge generated in sewage treatment, urine treatment, various industrial wastewater treatments, and the like. For example, first settling pond sludge, surplus sludge, anaerobic digestion sludge, aerobic digestion sludge, septic tank sludge, human waste including raw urine, and the like can be mentioned. Only one type of sludge may be treated alone, or two or more types of sludge may be mixed and treated. These organic sludges may contain inorganic substances.

The organic sludge preferably has a soluble calcium concentration range of 10 to 200 mg / L, more preferably 10 to 150 mg / L, still more preferably 10 to 100 mg / L, and particularly preferably 20 to 80 mg / L. The sulfate ion concentration range of the organic sludge is preferably 0.1 to 200 mg / L, more preferably 0.1 to 150 mg / L, and particularly preferably 0.5 to 120 mg / L.

When at least one of the soluble calcium concentration and the sulfate ion concentration of the organic sludge is within the above-mentioned preferable range, the formation of gypsum scale derived from the soluble calcium in the sludge is effectively suppressed.

The organic sludge before treatment usually has a pH of 6 or more, preferably 6 to 9, a calcium concentration of 100 to 700 mg / L, preferably 100 to 400 mg / L, and more preferably 100 to 350 mg / L. ing. When treating high-concentration sludge in which at least one of the soluble calcium concentration and the sulfate ion concentration exceeds the above-mentioned preferable concentration range, water, low-concentration sludge, and one or more dilution media selected from low-concentration wastewater are added. You may. "Low concentration" means that at least one of the calcium concentration and the sulfate ion concentration is lower than the upper limit of the above-mentioned suitable concentration. For example, a mixed sludge of low-concentration sludge and high-concentration sludge can be treated as organic sludge.

Soluble calcium concentration and sulfate ion concentration are present as water-soluble salts, ionized and dissolved in the sludge (Ca ^{2+, SO} 4 ^_2-) the method comprising the concentration present in the solubility of calcium concentration and The sulfate ion concentration can be measured by the ICP emission spectroscopic analysis method and the ion chromatograph method, which will be described later in Examples, respectively.

[Organic coagulant]
The organic coagulant is classified as a polymer flocculant in a broad sense, but is a small molecule and has a high degree of cation as compared with a drug classified as a polymer flocculant. Specifically, the molecular weight of the organic coagulant is several million or less, more specifically, the molecular weight is 1.5 million or less, preferably 1 million or less, more preferably 500,000 or less, and particularly preferably the molecular weight. It is 100,000 or less. The lower limit of the molecular weight is, for example, more than 4000, preferably 5000 or more, more preferably 10,000 or more, still more preferably 20,000 or more, and particularly preferably 30,000 or more. Specifically, it is more than 4000 and 1.5 million or less, preferably 5000 to 500,000 or less.

The molecular weight here is obtained by converting from the intrinsic viscosity (measured value at 25 ° C. in 0.2N-NaCl aqueous solution, unit is dl / g), and the viscosity formula of the polyacrylamide polymer: [η]. = 3.02 × 10 ^-4 × (Mw) ^0.68 (Mw) can be obtained for convenience from [Polymer coagulant, published by Tokyo Metropolitan Sewerage Service Co., Ltd., p. 113].

Further, as the organic coagulant, both powder and liquid exist, but in both cases, the viscosity when made into an aqueous solution is lower than that of the polymer flocculant, and the organic coagulant is usually a liquid. This may be referred to as a polymer flocculant, a polymer, a low molecular weight cationic flocculant, an organic coagulant, an organic coagulant, etc., but in the present specification, it is referred to as an organic coagulant. The organic coagulant according to the present invention is used in a method for dehydrating organic sludge, is cationic, and is preferably a liquid substance at room temperature (27 ° C.).

Examples of the organic coagulant used in this dehydration method include polyamine type, dicyandiamide type, polydicyandiamide type, polydiallyldimethylammonium chloride type (also referred to as "polyDADMAC type"), amino condensation type, and melamine colloid type. More than a species can be selected and used.

More specifically, polyalkylpolyamine, polyethyleneimine, diallyldimethylammonium chloride, ethylenediamine epichlorohydrin polycondensate, methylolmelamic acid colloid, dicyandiamide / ammonium chloride / formaldehyde polycondensate, polyethylene / polyamine / dimethylamine / epichlorohydrin polycondensate. , Dialkylamine / epichlorohydrin polycondensate (especially dimethylamine / epichlorohydrin polycondensate), polyallylamine hydrochloride, polydiallylmethylamine hydrochloride, copolymer of diallyldimethylammonium chloride and sulfur dioxide, diallyldimethylammonium chloride and acrylamide One or more kinds can be used from a copolymer, a copolymer of diallylamine hydrochloride and sulfur dioxide, and the like.

However, the concentration of the organic coagulant of the present invention (in the case of a mixture, the concentration of the entire mixture) is preferably 200 mg / L or less for metals and 200 mg / L or less for sulfate ions, and more preferably the concentration of metals. Is 100 mg / L or less, and the sulfate ion concentration is 100 mg / L or less. Therefore, organic coagulants containing sulfur atoms and metals, such as sulfur dioxide copolymers, should not be used, or if used, their amounts should be reduced. Among the above organic coagulants, polyamine-based, polyDADMAC-based, and polydicyandiamide-based ones have extremely low content of sulfur atoms and metals (may exist at the contamination level) and high sludge dehydration property. Organic coagulants are preferred, and polyamine-based organic coagulants are most preferred.

Here, the metals are substances selected from at least Ca, that is, any organic coagulant having a Ca concentration in the above-mentioned preferable range (eg, 200 mg / L or less) of the metals can be preferably used. However, more preferably, the concentration of the entire alkaline earth metal including Mg and the like is in the above-mentioned preferable range, and more preferably, it is composed of a transition metal such as Fe and a base metal such as Al in addition to the alkaline earth metal such as Ca. Use an organic coagulant having a total concentration of 200 mg / L or less of the metals.

The properties of the organic coagulant are high cationism (converted value of the organic coagulant component in the undiluted solution), and more specifically, the cationity as a component in the undiluted solution of the organic coagulant at pH 4 is preferably 5 meq / g or more. It is preferably 7 meq / g or more, and more preferably 10 meq / g or more. The viscosity of the undiluted solution of the organic coagulant (rotational viscometer, measured at 25 ° C.) is preferably 50 mPa · s or more, more preferably 150 mPa · s or more, and the upper limit is not particularly limited, but 4000 mPa · s or less is preferable.

The degree of cation at pH 4 can be measured by the following procedure. The polymer coagulant or the organic coagulant was dissolved in pure water to prepare a 500 mg / L polymer coagulant aqueous solution (component conversion) or an organic coagulant aqueous solution (component conversion in the stock solution). Next, 90 mL of pure water was mixed with 10 mL of a polymer coagulant aqueous solution or an organic coagulant aqueous solution, and the pH was adjusted to 4 with a 0.1N hydrochloric acid aqueous solution. Toluidine blue was added thereto, and the mixture was titrated with 1/400 standard potassium polyvinyl sulfate. In the titration, the end point was the time when the color changed from blue to magenta and held for 15 seconds or longer. The degree of cation (colloid equivalent value) was calculated from the following formula.
Cationicity (meq / g) = titration (mL) / 2

The organic coagulant can also be used in an undiluted stock solution. Here, the "undiluted solution" is, for example, a liquid product (eg, an aqueous solution) that can be distributed as an "organic coagulant", and in addition to an organic coagulant component (the above compound described as an organic coagulant), water or the like. The content of the organic coagulant component is 10% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more, and the content thereof. The upper limit is, for example, 90% by mass, preferably 70% by mass or less, and more preferably 50% by mass or less. Although the dehydration effect is high when used in such a stock solution, it is a diluted solution from the viewpoint of lowering the viscosity to facilitate impregnation and dispersion in the dehydrated cake, and increasing the volume by diluting to facilitate uniform dispersion. It is preferable to add it to the dehydrated cake after diluting it with (water). However, if the dilution ratio exceeds 60 times, the amount of water in the diluted solution increases, which may increase the amount of water in the dehydrated cake.

From the above viewpoint, the dilution ratio of the stock solution of the organic coagulant is preferably 60 times or less, particularly 2 to 60 times (mass ratio). A more preferable dilution ratio is 5 to 50 times. The diluent (solvent) contains water as a main component (50% by mass or more), preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 99% by mass or more of water, particularly substantially. Use a solvent consisting of water. Specifically, pure water, tap water, industrial water, groundwater, treated water for various wastewater treatments, seawater, etc. can be used, but from an economic point of view, industrial water, groundwater, and treated water for various wastewater treatments are preferable. ..

As described above, the diluent is not particularly limited, but if the metal concentration and the sulfate ion concentration of the diluent are high, the metal concentration and the sulfate ion concentration of the organic coagulant solution will be high as a result. The metal ion concentration and the sulfate ion concentration of the above are preferably 200 mg / L or less, more preferably 100 mg / L or less, and most preferably 50 mg / L or less. Therefore, from the viewpoint of these concentrations, it is preferable not to use hard water as the diluent, but to use tap water, pure water, or the like corresponding to so-called soft water (hardness 100 mg / L or less). When groundwater or the like having a high concentration of at least one of metals and sulfate ions is used, it can be mixed with the above-mentioned soft water or the like to prepare a diluted solution.

Regardless of whether the organic coagulant is diluted or not, the amount of the organic coagulant (stock solution in the case of liquid, solid content in the case of powder) is 0.1% by mass or more (0.1% by mass or more) with respect to the TS of the organic sludge. The dehydration effect can be enhanced by setting the mass% of the organic coagulant to the stock solution equivalent of the organic coagulant). On the other hand, even if the amount of organic sludge added to TS exceeds 3.0% by mass, the organic coagulant is wasted. Therefore, from this point of view, the amount of the organic coagulant added is preferably 0.1 to 3.0% by mass with respect to the TS of the organic sludge, particularly 0.5% by mass or more or 2.5% by mass. % Or less, more preferably 0.6% by mass or more or 2.0% by mass or less. When the amount of the organic coagulant added is 0.1% by mass or less, the component of the organic coagulant for promoting dehydration of the organic sludge becomes insufficient, and the dehydration of the organic sludge becomes insufficient.

[Polymer flocculant]
The polymer flocculant is not particularly limited as long as it contains a cationic group, and one or both of the cationic polymer flocculant and the amphoteric polymer flocculant can be used. It is also possible to use one or both of the anionic polymer flocculant and the nonionic polymer flocculant together with the polymer flocculant containing a cationic group, particularly the cationic polymer flocculant.

In either case, it is preferable to use a polymer flocculant having a cation content lower than that of the organic coagulant in the present invention. The cationicity of the polymer flocculant can be measured in the same manner as the organic coagulant. When two or more kinds of polymer flocculants are used, the value calculated from the cation degree and the mass ratio of each polymer flocculant can be estimated as the cation degree of the entire polymer flocculant.

Examples of the cationic polymer flocculant include an acrylate-based polymer flocculant (also referred to as "DAA-based polymer flocculant"), a methacrylate-based polymer flocculant (also referred to as "DAM-based polymer flocculant"), and an amide group. , Polyvinylamidine containing a nitrile group, an amine hydrochloric acid group, a formaldehyde group, etc. (also referred to as an "amidine-based polymer flocculant"), a Mannig modified product of polyacrylamide, and the like can be mentioned.

The amphoteric polymer flocculant is generally a copolymer of a cationic monomer such as (meth) acrylic acid ester and an anionic monomer such as acrylic acid, and further copolymerizes a nonionic monomer such as acrylamide. In some cases. Specifically, a copolymer of dimethylaminoethyl acrylate quaternary ammonium salt, acrylamide and acrylic acid, a copolymer of dimethylaminoethyl methacrylate quaternary ammonium salt and acrylamide and acrylic acid, and dimethylaminoethyl acrylate quaternary ammonium. Examples thereof include a salt, a quaternary ammonium salt of dimethylaminoethyl methacrylate, and a copolymer of acrylamide and acrylic acid.

The molecular weight of the polymer flocculant is not particularly limited, but it is preferable to use at least a polymer coagulant having a higher molecular weight than the organic coagulant. For example, the molecular weight is several million or more, specifically 2 million or more, preferably more than 2.5 million, more preferably 3 million or more, and particularly preferably 5 million or more. Similar to the organic coagulant, this molecular weight can also be obtained by converting from the intrinsic viscosity.

The polymer flocculant may be used as it is, but in order to enhance the dispersibility in organic sludge, it is preferable to use a solution of the polymer flocculant dispersed or dissolved in a solvent. The solvent may be the same solvent as the diluted solution of the organic coagulant, for example, pure water, tap water, industrial water, groundwater, treated water for various waste water treatments, seawater, etc. Pure water is desirable from the viewpoint of maximizing the effect. On the other hand, from the viewpoint of economy, tap water, industrial water, groundwater, and treated water for various wastewater treatments are desirable.

The dehydration effect can be enhanced by adding 0.3% by mass or more of the polymer flocculant to the TS of the organic sludge (mass% of the polymer flocculant is converted into a component of the polymer flocculant). , Even if it is added in excess of 3.5% by mass, the polymer flocculant is wasted. Therefore, from this point of view, it is desirable that the amount of the polymer flocculant added (excluding the solvent) is 0.3 to 3.5% by mass with respect to the TS of the organic sludge, and in particular, 0.4% by mass or more or It is more preferable to add in a proportion of 3.0% by mass or less. TS (Total solid) is a residual evaporative substance, and the mass of the substance remaining after evaporating and drying organic sludge at 105 ° C to 110 ° C is divided by the mass of sludge before evaporating and drying to 100. It is the value multiplied by (unit is%). For the measurement of TS, organic sludge before treatment according to the present invention is used.

Next, the first example and the second example of the dehydration method of the present invention will be described together with the processing apparatus used therein, but the present invention is not limited thereto.

[First Example of Dehydration Method of the Present Invention and Processing Device Used for It]
Reference numeral 10 in FIG. 2 shows an example of a treatment device used in the dehydration method of the first example, in which the treatment device 10 is a coagulation means 11 for adding a polymer flocculant to organic sludge to coagulate the organic sludge. , The concentration / pressure dehydration means 12 for concentrating and pressurizing and dehydrating the aggregated sludge, the organic coagulant adding means 13 for adding the organic coagulant to the sludge after the concentration and pressure dehydration, and the organic coagulant are added. It is provided with a dewatering means 14 for mechanically dewatering the sludge. The organic sludge sent to the treatment apparatus 10 is first subjected to a coagulation step using a polymer coagulant in the coagulation means 11.

<Aggregation process>
The aggregating means 11 is not particularly limited, but preferably has a mixing tank 11a, and the mixing tank 11a contains a polymer coagulant solution in a mixed state dispersed or dissolved in the above solvent. The coagulation means 11 further has a coagulation tank 11b for treating organic sludge, and a polymer flocculant or a solution thereof supplied from the mixing tank 11a is added into the coagulation tank 11b.

A control means such as a flow rate adjusting means may be installed in the aggregating means 11, and the TS of the organic sludge may be measured in advance, or the TS may be measured from the information of the organic sludge (sludge source, past TS measured value, etc.). As expected, the amount of the polymer flocculant added may be controlled by the control means based on the TS and the supply amount of the organic sludge.

When organic sludge is supplied to the coagulation tank 11b and the polymer coagulant supplied from the mixing tank 11a and this organic sludge are stirred and mixed by the stirring means of the coagulation tank 11b, the organic sludge is produced by the polymer coagulant. Aggregates to form aggregated flocs. That is, in the processing device 10, a part or all of the device for the coagulation step is configured by the coagulation tank 11b and the mixing tank 11a. If organic sludge can be agglomerated, the configuration of the device, the form of the device, the number of devices, the dimensions of the device, or the number of water tanks used for coagulation, the structure of the water tank, the form of the water tank. There are no restrictions on the dimensions of the device, as well as the aggregation method and technique.

Regardless of which device is used, the water content of the finally obtained dehydrated cake can be effectively reduced by the coagulation treatment using the polymer coagulant, and the amount of the organic coagulant used in the subsequent stage can be adjusted appropriately. can do.

In this processing apparatus 10, a concentration / pressure dehydration means 12 is installed after the coagulation tank 11b to concentrate the coagulated sludge obtained in the coagulation step and remove excess water. Next, this concentration / pressure dehydration step will be described.

<Concentration / pressure dehydration process>
In the concentration / pressure dehydration step, the aggregated sludge is concentrated and pressure dehydrated. "Pressure dehydration" refers to applying pressure to sludge from the outside by some method to pressurize it. Since the agglomerated sludge or the sludge after concentrating the agglomerated sludge contains a large amount of water, it is inevitably dehydrated by pressurization, and the final sludge TS is as described later. The concentrating / pressure dehydrating means 12 used in this step includes a sludge squeezing machine 12a. FIG. 3 shows an example of the sludge squeezer 12a. In the coagulation step, a separation liquid (also referred to as a filtrate or treated water) separated from the sludge during coagulation is generated together with the coagulation sludge, and the coagulation sludge and the separation liquid in a mixed state are charged from the coagulation sludge inlet 21. .. The charged sludge and the separated liquid (filter solution or treated water) are moved toward the sludge discharge port 29 on the belt 23 of the coagulated sludge moving means 22. The belt 23 has a mesh shape, and in the process of being moved, solid-liquid separation is performed, coagulated sludge is transferred to the pressurizing means 25, and the separation liquid (filter solution or treated water) is separated solution and filtrate capturing means 27. It is collected and discharged to the outside of the aircraft. The concentrated sludge is pressurized and dehydrated by the pressure plate 26 of the pressurizing means 25, and the sludge is further dehydrated as the solid-liquid separation progresses.

In the concentration / pressure dehydration step, the sludge after concentration and pressure dehydration (hereinafter, also referred to as “pressure concentrated sludge”) is concentrated and pressure dehydrated so that the TS is 40 to 150 g / L. More preferably, the sludge TS after concentration and pressure dehydration is 50 to 140 g / L, and more preferably, the TS is 60 to 120 g / L. When the TS is less than 40 g / L, the water content becomes high and the amount of the organic coagulant added later increases, while when the TS exceeds 150 g / L, the dispersibility / permeability of the organic coagulant added is increased. Decreases.

"TS" is a residual evaporative substance, and in this case, it is calculated from the mass of the substance remaining after evaporating and drying the sludge at 105 to 110 ° C. and the mass of the agglomerated sludge before evaporating and drying. be able to.

Focusing on the water content, the water content of the sludge sent to the next step after concentration and pressure dehydration is preferably more than 85% by mass, more preferably 87% by mass or more, and is a preferable upper limit of the water content. Is 96% by mass, more preferably 93% by mass or less, and even more preferably 92% by mass or less.

Focusing on the dispersibility and permeability of the chemicals in the concentrated and pressure-dehydrated sludge, the water content of the aggregated sludge increases if the sludge is simply gravity-concentrated without pressure, and the dispersibility and permeability of the chemicals. However, when the drug is added in the subsequent stage, the drug tends to flow out to the dehydration filtrate side in the concentration step or the dehydration step. On the other hand, when concentrated and pressure dehydrated, the dispersibility and permeability of the drug to the sludge after concentration and pressure dehydration are reduced as compared with ordinary gravity concentration, but the water content reduction effect and fluidity are reduced. It can be reduced. In addition, there is an advantage that the outflow of the drug can be prevented and the amount of the drug used can be reduced.

The means for concentrating and dehydrating sludge is not limited to the sludge squeezer, and a conventional sludge concentrator using pressurization can also be used. Further, although an example in which a concentration / pressure dehydration means is provided in one machine (sludge press) is shown, the concentration means for concentration and the pressure dehydration means for pressure dehydration are separately configured. May be good.

In the present invention, the pH of each sludge before being subjected to the concentration / pressure dehydration step including the organic sludge before the treatment and the agglomerated sludge is preferably 6 or more, more preferably in the range of 6 to 9. Is. This is because calcium is eluted from the sludge and causes gypsum scale in the above step in this step or earlier, and it is necessary to make the pH range of each sludge after this step within the above pH range. Because. Similarly, the pH of at least one of the concentrated and pressure-dehydrated sludge (pressure-concentrated sludge) and the dehydrated filtrate thereof is preferably 6 or more, and more preferably 6 to 9.

As shown in FIGS. 2 and 3, the above-mentioned concentration and pressure dehydration steps and means thereof have shown an example in which concentration and pressure dehydration are simultaneously performed or pressure dehydration is performed together with concentration, but the present invention is limited to this. Instead, for example, as in the flow shown in FIG. 1, it may be concentrated and then dehydrated under pressure.

<Sludge squeezer>
The sludge squeezing machine shown in FIG. 3 will be further described. The sludge squeezing machine 12a separates the coagulated sludge and the separated liquid in solid and liquid, and moves only the coagulated sludge toward the sludge discharge port 29. And the apparatus having the pressurizing means 25 for obtaining the pressurized concentrated sludge by pressurizing and concentrating the coagulated sludge.

In the coagulation step, a separation liquid (filter solution or treated water) separated from the sludge is generated together with the coagulation sludge, but the coagulated sludge and the separation liquid (filter solution or treated water) in a mixed state are combined with the coagulation sludge inlet 21. Put in from. In the sludge squeezing machine 12a, there is a coagulated sludge moving means 22 including a belt 23, a belt driving device 24 for driving the belt 23, and a belt cleaning pipe 30 for cleaning the belt 23. The charged sludge and the separated liquid (filter solution or treated water) are moved toward the sludge discharge port 29 on the belt 23 of the coagulated sludge moving means 22. In the process of being moved, solid-liquid separation is performed, sludge is collected by the pressurizing means 25, and the separated liquid (filter solution or treated water) is collected by the separation solution and the filtrate capturing means 27, and discharged to the outside of the machine. Will be done.

The pressurizing means 25 concentrates the agglomerated sludge by pressurizing the agglomerated sludge with the pressurizing plate 26. Concentration of sludge by pressurization can be carried out more effectively than gravity filtration or the like. The coagulated sludge is pressure-dehydrated by the pressure plate 26 of the pressure means 25, and further solid-liquid separation progresses, so that the sludge is concentrated and becomes pressure-concentrated sludge.

When the coagulated sludge is pressure-dehydrated, the pressure applied to the coagulated sludge may be appropriately adjusted so that the TS of the pressure-aggregated sludge is within the above range. As a guideline for the pressure applied to the coagulated sludge, it is preferable to apply a pressure of 1 to 200 kPa to the coagulated sludge, preferably 5 kPa or more and 150 kPa or less, more preferably 10 kPa or more or 100 kPa or less, still more preferably 10 kPa or more or 50 kPa. It is even more preferable to apply the following pressure to the coagulated sludge.

The pressurized concentrated sludge is discharged from the sludge discharge port 29 as it is, but it is preferable to install a dividing machine 28a described later at the sludge discharge port 29.

In the example shown in FIG. 3, pressure dehydration is performed after concentration, but concentration and pressure dehydration may be performed at the same time.

<Organic coagulant addition process>
Next, the step of adding the organic coagulant will be described. The coagulant adding means 13 shown in FIG. 2 is not particularly limited, but for example, it has a storage tank 13a for the organic coagulant, and the stock solution or the diluted solution of the organic coagulant is stored in the storage tank 13a. The properties and usage patterns of the organic coagulant used are as described above.

In this step, the dehydration efficiency can be further improved by adding the above-mentioned organic coagulant to the sludge that has undergone the above-mentioned aggregation step and the concentration / pressure dehydration step (and any division step described later). In this example, an example of adding an organic coagulant to the sludge that has been concentrated and pressure-dehydrated has been described. However, as shown in FIG. 1, organic coagulation is performed on the sludge after the above concentration and before pressure dehydration. The same effect can be obtained by adding an agent.

Similar to the aggregating means 11, the organic coagulant adding means 13 may be provided with a control means such as a flow rate adjusting means, and the TS of untreated (before the addition of the polymer aggregating agent) organic sludge may be measured. Predict the TS from the information of organic sludge (sludge source, past TS measurement value, etc.), and based on this TS and the supply amount of organic sludge, the amount of organic coagulant added (stock solution) by the control means. Alternatively, the solid content) may be controlled within the above-mentioned preferable range (0.1% by mass or more with respect to TS).

It is also possible to use an inorganic coagulant or a coagulant (inorganic coagulant) together with the organic coagulant. However, since both aluminum-based and iron-based general inorganic flocculants are acidic, when the inorganic flocculant is added to the concentrated sludge, calcium existing in the form of a sparingly soluble salt or the like is eluted in the organic sludge. , Soluble calcium concentration will increase. Moreover, some inorganic flocculants contain sulfate ions such as iron (I), (II), polyferric sulfate, and aluminum sulfate, and the reaction between these sulfate ions and soluble calcium causes sulfate. Calcium (hereinafter referred to as gypsum scale) is precipitated.

Therefore, when an inorganic coagulant is added, it is necessary to suppress the amount of the inorganic coagulant added. For example, the amount of the inorganic coagulant used is 1/10 or less, preferably less than 1/100 of the organic coagulant in terms of mass ratio, which is most preferable. Does not use inorganic flocculants.

After adding the organic coagulant, the sludge is sent to the dewatering means 14 and subjected to the following mechanical dewatering step. Further, in the present invention, the pH of at least one of the sludge to which the organic coagulant is added and the dehydration filtrate thereof is 6 or more, preferably 6 to 9. If the pH is less than 6, calcium is eluted from the sludge and causes gypsum scale. Therefore, it is possible to prevent gypsum scale formation by setting the pH to 6 or more.

<Mechanical dehydration process>
The dewatering means 14 is not particularly limited, and a device that can be mechanically dewatered, which is usually used for sludge dewatering, can be widely used. Is particularly suitable for a device provided with a pipe for discharging the dehydrated filtrate and a filtration mechanism (punching metal, wedge wire screen, multiple disks, etc.).

For example, one or more types from screw press dehydrator, centrifugal dehydrator, multiple disk type dehydrator, multiple plate type screw press dehydrator, rotary pressure dehydrator, elliptical plate type dehydrator, vacuum dehydrator, belt press dehydrator, etc. Can be selected and used as the dehydration means 14.

When any of the dewatering means 14 is used, the pressurized concentrated sludge to which the organic coagulant is added can be mechanically dewatered and solid-liquid separated into a filtrate and a dewatered cake. According to such a dehydration method, the water content of the dehydrated cake can be reduced to 80% by mass or less, preferably 75% by mass or less.

As described above, the organic coagulant has an extremely low content of sulfate ions and metals, and the pH fluctuation of the dehydration filtrate is smaller than that when the inorganic flocculant is used, so that calcium in sludge is difficult to elute. .. In addition, the use of the organic coagulant causes almost no increase in sulfate ions in the dehydrated filtrate.

Specifically, the amount of increase in the soluble calcium concentration in the dehydrated filtrate when the organic coagulant is added is 40 mg / L or less, preferably 30 mg / L or less, as compared with the case where the organic coagulant is not added. More preferably 20 mg / L or less, the amount of increase in sulfate ion concentration is 3 mg / L or less, preferably 1.5 mg / L or less, more preferably 0.5 mg / L or less, and when an organic coagulant is added. The pH of the dehydrated filtrate can be 6 or more, preferably 6-9. As a result, since the ion product of the calcium ion ^{[Ca 2+]} and sulfate ions in the filtrate _[SO ^{4 2-]} is reduced, it is possible to suppress the formation of gypsum scale (CaSO _4), attached to the dehydration means 14 The gypsum scale can be reduced.

In this way, while reducing the sludge moisture content and the amount of waste, by adding an organic coagulant that does not contain metals or sulfate ions afterwards, the effect of preventing the formation of gypsum scale and the effect of preventing the formation of iron clinker during sludge incineration. , Effective for composting dehydrated cake, etc. can be obtained.

[Second Example of Dehydration Method of the Present Invention and Processing Device Used for It]
FIG. 4 is a diagram showing a second example of the dehydration method of the present invention and a processing apparatus used for the second example. The same configuration as that of the first example of the dehydration method of the present invention shown in FIG. 2 is indicated by the same reference numerals, and the description thereof will be omitted. In the second example, the difference from the first example is that the concentration / pressure dehydration means 12 is followed by the division means 28 for dividing the pressure-concentrated sludge. The dividing means 28 includes a dividing machine 28a, and the dividing machine 28a divides the pressurized concentrated sludge generated by the concentrating / pressurizing / dehydrating means 12 (dividing step). By dividing the pressurized concentrated sludge, the dispersibility and permeability of the organic coagulant are improved in the subsequent addition of the organic coagulant.

FIG. 5 shows an example of the state of dispersion and permeation of the organic coagulant when the pressurized concentrated sludge is divided and when it is not divided. Since the pressure-concentrated sludge formed in the concentration / pressure-dewatering process is pressure-concentrated, its fluidity is lower than that of the concentrated sludge dehydrated by gravity. Poor permeability and dispersibility. However, when the pressurized concentrated sludge is agitated or kneaded in order to disperse the organic coagulant, the agglomerated flocs formed by the agglomeration by the polymer flocculant are broken, and the water content is effectively reduced. May not be possible. On the other hand, by dividing the pressurized concentrated sludge, the organic coagulant can be permeated and dispersed from the cross section, so that the effect of the organic coagulant can be enhanced and the amount of the organic coagulant used can be reduced. can do.

If not split, the organic coagulant penetrates and disperses only on the top surface. However, since the pressure-concentrated sludge is at least blocked by division, the organic coagulant permeates and disperses from the upper surface and end face and penetrates into the dehydrated cake as compared with the case of simply pressure-concentrating. Can be dispersed.

The direction of division may be vertical or horizontal. If it is formed in the vertical direction, by adding an organic coagulant from above, the vertical plane, which is a partial cross section, can be naturally transmitted and dispersed.

Further, the division may be performed at appropriate intervals in the vertical direction or the horizontal direction when the pressurized concentrated sludge is viewed from above, or may be divided in a grid pattern.

Regarding the division interval, in order to divide the aggregated flocs formed by the polymer flocculant without breaking them, it can be considered that the division interval should be 1 cm or more. On the other hand, if the interval between divisions is larger than 10 cm, the effect of division may be impaired. From such a viewpoint, the interval of division is preferably 1 cm to 10 cm, and more preferably 2 cm or more or 5 cm or less.

<Dividing machine>
FIG. 6 shows an example of the dividing machine 28a. This figure is an enlarged view of a part of the sludge discharge port 29 of the sludge squeezing machine 12a shown in FIG. As shown in FIG. 6, the comb-shaped cutting blades 31 are installed at the sludge discharge port 29 of the sludge squeezing machine 12a at appropriate intervals in the horizontal direction so that the blades are installed in the vertical direction. Can be configured.

However, the dividing machine 28a is not limited to the above configuration. For example, a cutting blade assembled in a grid pattern on the upper surface, or a cutting blade assembled at appropriate intervals in the length direction or the width direction of the pressurized concentrated sludge when viewed on the upper surface, is applied to the pressurized concentrated sludge. It is also possible to use a device that can be raised and lowered from above.

As described above, in the present invention, it is possible to reduce the sludge water content, reduce the amount of waste, and suppress the formation of gypsum scale, and further, when the above-mentioned dividing step is performed, the permeability of the organic coagulant and the permeability and It is possible to improve the dispersibility.

Hereinafter, the present invention will be further described based on the following Examples and Comparative Examples. In this test, coagulated sludge is concentrated and dehydrated under pressure to obtain concentrated sludge under pressure, and then an organic coagulant is added to the concentrated sludge under pressure to dehydrate it, thereby suppressing the formation of gypsum scale and reducing the water content. We examined whether the effect could be obtained.

<Test method>
In the test, mixed sludge derived from one type of human waste treatment plant (surplus sludge + coagulated sludge) (sludge A), mixed sludge derived from two types of human waste treatment plant (raw urine + septic tank sludge) (sludge B, C) A total of 3 types were used.

The TS of sludge A, sludge B, and sludge C are 11.4 g / L, 7.98 g / L, and 6.56 g / L, respectively, and the pH is 6.9, 7.3, 6.8, and the calcium concentration is 305 mg / L, 126 mg / L, 173 mg / L, respectively, soluble calcium concentration was 71.7 mg / L, 27.7 mg / L, 53.3 mg / L, respectively, and sulfate ion concentration was 101 mg / L, 0.6 mg / L, respectively. It was L, 2.0 mg / L.

TS is an evaporation residue, and is a concentration of a substance remaining when sludge is evaporated to dryness at 105 ° C to 110 ° C. The measurement method was based on the sewage test method (published by the Japan Sewerage Association, sewage test method).

The soluble calcium concentration and the sulfate ion concentration were first pretreated according to the glass fiber filter paper method (JIS K 0102 14.1) of the sewage test method. Specifically, a filtrate obtained by suction-filtering a stock solution sample with a glass fiber filter paper having a pore size of 1 μm was used as a measurement sample.

For the measurement of soluble calcium, the measurement sample prepared in the pretreatment was measured according to the ICP emission spectroscopic analysis method of the sewage test method. Specifically, a sample to which (1 + 1) nitric acid (35% nitric acid) was added was heated to 97 ° C. or higher for 5 to 10 minutes, and the cooled sample was measured by an ICP emission spectrophotometer. Measurement of Sulfate ion (SO 4 ^_2-) is a measurement sample prepared in the previous process, according to ion chromatography sewage test method was measured.

The calcium concentration is the total calcium concentration including the form of the insoluble salt. For this calcium concentration, first, an appropriate amount of sludge was dissolved in pure water to prepare an aqueous sludge solution. This sludge aqueous solution was measured according to the ICP emission spectroscopic analysis method of the sewage test method in the same manner as the measurement of the soluble calcium concentration.

As the polymer flocculant, sludge A contains an amphoteric polymer flocculant A (a mixture of a polymethacrylic acid ester / acrylic acid copolymer and a polyacrylic acid ester / acrylic acid copolymer, a molecular weight of 3 million, and a cation at pH 4. Degree about 1.5 meq / g), cationic polymer flocculant B (polyacrylic acid ester type, molecular weight 8 million, cationic degree at pH 4 about 3.3 meq / g) for sludge B, high cationic for sludge C A molecular flocculant C (polyacrylic acid ester type, molecular weight 7 million, cation degree at pH 4 of about 4.0 meq / g) was used. When the polymer flocculant was used, the powder was dissolved in pure water and used as an aqueous solution of the polymer flocculant having a dissolution concentration of 2 g / L.

Examples of the organic coagulant include organic coagulant a (polyamine type, molecular weight 250,000, cation degree as a component in the stock solution of the organic coagulant at pH 4 of about 6 meq / g), organic coagulant b (polyamine type, molecular weight 30,000,). 2. Cationicity as a component in the stock solution of the organic coagulant at pH 4 (polyDADMAC system, molecular weight 30,000, cationic degree as a component in the stock solution of the organic coagulant at pH 4). 4 meq / g) and organic coagulant d (polydisyandiamide type, molecular weight 15,000, cation degree as a component in the stock solution of the organic coagulant at pH 4 of about 5.9 meq / g), a total of four types were used. When the organic coagulant was used, the liquid (stock solution) was diluted with pure water and used as the organic coagulant diluent having a dissolution concentration of 20 g / L in the stock solution.

The inorganic flocculant used in the comparative example described later was a ferric polysulfate (hereinafter, inorganic flocculant) solution (stock solution) having a concentration of 160 g-Fe / L, and this stock solution was used as the inorganic flocculant.

<Test procedure>
The test procedure is as follows.
(Agglutination of sludge, concentration of sludge and pressure dehydration)

In the sludge A test, an aqueous solution of the polymer flocculant A was added to 500 mL of the organic sludge placed in the beaker so that the TS concentration of the polymer flocculant was 2.8% by mass, and the sludge aggregated with a spatula. The mixture was stirred until the mixture was formed to form agglomerated sludge A. The coagulated sludge A was solid-liquid separated on a sieve, and the sludge was concentrated and dehydrated under pressure using a pressure plate to obtain a pressure-concentrated sludge A. The TS of the pressurized concentrated sludge A was 63.3 g / L.

In the sludge B test, an aqueous solution of the polymer flocculant B was added to 500 mL of the organic sludge placed in the beaker so that the TS concentration of the polymer flocculant was 1.3% by mass, and the sludge aggregated with a spatula. The mixture was stirred to form aggregated sludge B. The coagulated sludge B was solid-liquid separated on a sieve, and the sludge was concentrated and dehydrated under pressure using a pressure plate to obtain a pressure-concentrated sludge B. The TS of the pressurized concentrated sludge B was 88.7 to 114 g / L.

In the sludge C test, an aqueous solution of the polymer flocculant C was added to 500 mL of the organic sludge placed in the beaker so that the concentration of the polymer flocculant with respect to TS was 1.5% by mass, and the sludge aggregated with a spatula. The mixture was stirred until agglomerated sludge was formed. The coagulated sludge was solid-liquid separated on a sieve, and the sludge was concentrated and dehydrated under pressure using a pressure plate to obtain a pressure-concentrated sludge C. The TS of the pressurized concentrated sludge C was 109 g / L.

The specific method of concentration and pressure dehydration is to place the coagulated sludge on a sieve (opening 1 mm) and use a pressure plate (pressure 20 kPa to 25 kPa) to pressurize the water to be treated containing the coagulated sludge. Solid-liquid separation was performed into a melt (= treated water).

(Dehydration test)
[Pressurized concentrated sludge A]
In Examples 1-1, 1-2, 1-3, and 1-4, the injection amount of 0.64% by mass (to TS) (based on the stock solution equivalent of the organic coagulant) was added to the pressurized concentrated sludge A, respectively. The organic coagulants a, b, c, and d were added, respectively, and dehydrated using a test belt press dehydrator, and the water content of the dehydrated cakes A1-1, A1-2, A1-3, and A1-4 was measured. ..

Further, in Examples 1-5 and 1-6, the amount of the organic coagulant b added to the pressurized concentrated sludge A was 1.28% by mass and 1.92% by mass (vs. TS) (converted to the stock solution of the organic coagulant). The water content of the dehydrated cakes A1-5 and A1-6 was measured by dehydration in the same manner as in Example 1-2 above, except that the content was changed to (according to). Moreover, the water quality analysis of the dehydration filtrate A1-5 in Example 1-5 was carried out.

As a comparative test, a test in which an inorganic flocculant was added to each pressurized concentrated sludge was carried out according to the following test procedure. In Comparative Example 1, neither the inorganic flocculant nor the organic coagulant was added to the pressurized concentrated sludge A, and the sludge was dehydrated using a test belt press dehydrator, the water content of the dehydrated cake a1 was measured, and the dehydration filter was performed. A water quality analysis of the liquid a1 was carried out.

In Comparative Examples 2-1, 2-2, and 2-3, 1.0% by mass, 2.0% by mass, and 3.0% by mass (vs. TS) (stock solution of inorganic flocculant) were added to the pressurized concentrated sludge A, respectively. Add an inorganic flocculant (according to Fe conversion in), dehydrate using a test belt press dehydrator, measure the water content of the dehydrated cakes a2-1, a2-2, a2-3, and dehydrate filtrate a2. -2 water quality analysis was carried out.

[Pressurized concentrated sludge B]
In Examples 2-1 and 2-2, 2-3, and 2-4, the injection amount of 0.64% by mass (to TS) (based on the stock solution equivalent of the organic coagulant) was added to the pressurized concentrated sludge B, respectively. The organic coagulants a, b, c, and d were added, respectively, and dehydrated using a test belt press dehydrator, and the water content of the dehydrated cakes B2-1, B2-2, B2-3, and B2-4 was measured. ..

Further, in Examples 2-5 and 2-6, 1.28% by mass and 1.92% by mass (vs. TS) of the organic coagulant b (based on the stock solution equivalent of the organic coagulant) were added to the pressurized concentrated sludge B, respectively. Each was added and dehydrated using a test belt press dehydrator, and the water content of the dehydrated cakes B2-5 and B2-6 was measured. Moreover, the water quality analysis of the dehydration filtrate B2-5 in Example 2-5 was carried out.

In Comparative Example 3, the pressurized concentrated sludge B to which neither the inorganic flocculant nor the organic coagulant was added was dehydrated using a test belt press dehydrator, the water content of the dehydrated cake b1 was measured, and the dehydrated filtrate was measured. A water quality analysis of b1 was carried out.

In Comparative Examples 4-1, 4-2, and 4-3, 1.0% by mass, 2.0% by mass, and 3.0% by mass (vs. TS) (stock solution of inorganic flocculant) were added to the pressurized concentrated sludge B, respectively. Add an inorganic flocculant (according to Fe conversion in), dehydrate using a test belt press dehydrator, measure the water content of the dehydrated cakes b4-1, b4-2, b4-3, and dehydrate filtrate b4. -2 water quality analysis was carried out.

[Pressurized concentrated sludge C]
In Examples 3-1, 3-2, and 3-3, the organic coagulant a was injected into the pressurized concentrated sludge C in an amount of 0.64% by mass (vs. TS) (based on the stock solution equivalent of the organic coagulant). , B, and d were added, respectively, and dehydrated using a test belt press dehydrator, and the water content of the dehydrated cakes C3-1, C3-2, and C3-3 was measured.

Further, in Examples 3-5 and 3-6, 1.28% by mass and 1.92% by mass (vs. TS) of the organic coagulant b (based on the stock solution equivalent of the organic coagulant) were added to the pressurized concentrated sludge C, respectively. Each was added and dehydrated using a test belt press dehydrator, and the water content of the dehydrated cakes C3-5 and C3-6 was measured. Moreover, the water quality analysis of the dehydration filtrate C3-5 in Example 3-5 was carried out.

In Comparative Example 5, the pressurized concentrated sludge C to which neither the inorganic flocculant nor the organic coagulant was added was dehydrated using a test belt press dehydrator, the water content of the dehydrated cake c1 was measured, and the dehydrated filtrate was measured. A water quality analysis of c1 was carried out.

In Comparative Examples 6-1, 6-2, and 6-3, 1.0% by mass, 2.0% by mass, and 3.0% by mass (vs. TS) (stock solution of inorganic flocculant) were added to the pressurized concentrated sludge C, respectively. Add an inorganic flocculant (according to Fe conversion in), dehydrate using a test belt press dehydrator, measure the water content of the dehydrated cakes c6-1, c6-2, c6-3, and dehydrate filtrate c6. -2 water quality analysis was carried out.

<Test results>
[Examination of water content reduction effect of dehydrated cake]
(Examples 1 to 3)
The test results of Examples 1 to 3 are shown in Tables 1-1 to 1-3.

When the organic coagulants a to d were compared under the condition of an injection rate of 0.64% by mass, the organic coagulant b had the highest dehydration effect on sludges A and B, and also had the highest water content on sludge C. The difference from the low Example 3-1 was as small as 0.4% by mass. Therefore, it was confirmed that a high dehydration effect can be obtained by using a polyamine-based organic coagulant having a high degree of cation.

(Comparative Examples 1 and 2 and Examples 1-2, 1-5, 1-6)
Tests of Comparative Examples 1-6, Examples 1-2, 1-5, 1-6, Examples 2-2, 2-5, 2-6, Examples 3-2, 3-5, 3-6 The results are shown in Tables 2-1 to 2-3. For comparison with Examples, the results of Examples 1-2, 1-5, and 1-6 are also shown in the table below.

As is clear from the above table, Comparative Examples 1, 3 and 5 in which neither the organic coagulant nor the inorganic coagulant was added were compared with the case where the organic coagulant or the inorganic coagulant was added to the same sludges A, B and C. It was confirmed that the dehydrated cake had the highest water content and the lowest dehydration effect.

Compared with Comparative Examples 1, 3 and 5, when the organic coagulant or the inorganic coagulant was used, the water content was reduced by about 2.8 to 3.2% by mass, and the organic coagulant and the inorganic coagulant were used. The water content reducing effect of the organic coagulant was equal to or slightly inferior to that of the inorganic coagulant (0.3 to 0.8% by mass) with respect to the pressurized concentrated sludges A and B.

Based on the results of the examples of the present invention, the water content of the dehydrated cake is increased by adding an organic coagulant after the polymer flocculant (post-addition method) to the pressurized concentrated sludge obtained by concentrating and pressure dehydrating the coagulated sludge. It was confirmed that the effect of reduction can be obtained.

<Examination of gypsum scale generation inhibitory effect>
The water quality analysis results of the dehydrated filtrate were performed for the analysis items in Table 3 below.

Among analysis items, pH, M- alkalinity, SS, method of measuring _PO 4 -P is compliant with the sewage test method. The method for measuring the electrical conductivity was based on JIS K 0102.

Specifically, the pH was measured for the dehydrated filtrate collected by the glass electrode method. The M-alkalinity was measured by a method for measuring alkalinity [pH 4.8] (total alkalinity or M-alkalinity). SS was calculated from the results of weight weighing after suction-filtering the dehydrated filtrate with a glass fiber filter paper having a pore size of 1 μm, heating the filtered filter paper at 105 ° C. for 2 hours, and allowing it to cool. PO _4- P was measured by the molybdenum blue (ascorbic acid reduction) absorptiometry with respect to the dehydrated filtrate after suction filtration. The electrical conductivity was measured by an analyzer METTTLER TOREDO MC226 (METTTLER TOREDO, Switzerland).

S-Ca (soluble calcium concentration) and SO 4 ^_2-(sulfate ion concentration), except that the measurement sample using a dehydration filtrate were measured under the same conditions as the measurement method of sludge A through C. The measurement temperature of each analysis item is 18 ° C.

The measurement results of each analysis item are shown in Table 3-1.

The equilibrium and solubility product of gypsum in solution is expressed by the following formula.
CaSO ₄ ⇔ Ca ²⁺ + SO ₄ ^2-
K _sp = [Ca ²⁺ ] [SO ₄ ^2- ]

Therefore, if the ion product of ^{Ca 2+} and SO ₄ ^2- _{is higher than the saturated solubility product K sp} , the gypsum scale is likely to precipitate as a solid substance.

Comparing Comparative Examples 1, 3 and 5 (when using only the polymer flocculant) and Examples 1-5, 2-5 and 3-5 (when using the organic coagulant), there is a difference in the water content reduction effect. However, no significant difference was confirmed in the analysis item results of the dehydrated filtrate in Table 3. Specifically, the amount of increase in the soluble calcium concentration was 5.1 to 17.8 mg / L, and the amount of increase in the sulfate ion concentration was 0 to 2.1 mg / L.

However, the dehydration filtrate of Comparative Example 2-2,4-2,6-2 using inorganic coagulant, lowering of pH, decrease of M- alkalinity is observed, in particular S-Ca and _SO ^{4 2 -} a substantial increase in (S-Ca: 5~10 _times, ^SO 4 2-: _26~857-fold) was observed.

In addition, the pH of the examples in which the organic coagulant was used was 7.5 to 7.9, and the amount of pH change was 0.1 to 0.4 as compared with the case where only the polymer flocculant was used. On the other hand, the pH of the comparative example using the inorganic flocculant was 4.1 to 5.1, and the amount of pH change was 2.3 to 3 as compared with the case where only the polymer flocculant was used. There was also .2.

In the embodiment using the organic coagulating agent, ion product b calculated the measured value S-Ca, the SO ₄ ^2-is lower than the saturation solubility product a in any of the filtrate, theoretically gypsum scale Is not considered to precipitate. In addition, the amount of increase in the soluble calcium concentration when the organic coagulant was added was 5.1 to 17.8 mg / L, and the amount of increase in the sulfate ion concentration was 0 to 2.1 mg / L. The calcium concentration and sulfate ion concentration contained were assumed to be 200 mg / L or less. In the comparative example using the inorganic flocculant, it is considered that the ion product b is higher than the saturated solubility product a and the gypsum scale is precipitated.

From the above results, it was confirmed that when an organic coagulant was used, the gypsum scale-forming component could be reduced and the gypsum scale-forming inhibitory effect was exhibited. In addition, the inorganic flocculant contains metals such as iron and aluminum, whereas the organic coagulant has an extremely low concentration of metals, so that the formation of clinker such as ferrite and aluminate is suppressed when the dehydrated cake is incinerated. In addition, since phosphoric acid is _{not removed as poorly soluble salts (FePO 4} , AlPO ₄ ), the dehydrated cake can be suitably reused as compost.

10 Treatment device 11 Coagulation means 11a Mixing tank 11b Coagulation tank 12 Concentration / pressure dehydration means 12a Sludge squeezer 13 Organic coagulant addition means 13a Organic coagulant storage tank 14 Dehydration means 21 Coagulation sludge inlet 22 Coagulation sludge moving means 23 Belt 24 Belt drive device 25 Pressurizing means 26 Pressurizing plate 27 Separation liquid and filtrate capturing means 28 Dividing means 28a Dividing machine 29 Sludge discharge port 30 Belt cleaning pipe 31 Cutting blade

Claims (9)

A polymer flocculant having a molecular weight of 2 million or more is added to an organic sludge that satisfies at least one of a soluble calcium concentration range of 10 to 200 mg / L and a sulfate ion concentration range of 0.1 to 200 mg / L. And the process of aggregating
The step of concentrating and pressurizing and dehydrating the agglomerated sludge, and
A step of adding an organic coagulant having a molecular weight of 1.5 million or less to the sludge after the concentration or the pressure dehydration, and
The step of mechanically dehydrating the sludge to which the organic coagulant is added is included.
At least one of the sludge to which the organic coagulant is added and the dehydrated filtrate thereof has a pH of 6 or more, and the evaporation residue (TS) of the concentrated and pressure-dehydrated sludge is 40 to 150 g / L. A method for dehydrating organic sludge, which is characterized by being present. The method for dehydrating organic sludge according to claim 1, wherein the organic coagulant has a cation degree of pH 4 of 5 meq / g or more. The method for dehydrating organic sludge according to claim 1 or 2, wherein the organic coagulant is a liquid having a viscosity of a stock solution at 25 ° C. of 50 mPa · s or more. The method for dehydrating organic sludge according to any one of claims 1 to 3, wherein the organic coagulant has a molecular weight of more than 4000 and 1.5 million or less. The method for dehydrating organic sludge according to any one of claims 1 to 4, wherein the organic coagulant is added as a solution undiluted or diluted to a dilution ratio of 60 times or less. The method for dehydrating organic sludge according to any one of claims 1 to 5, wherein an inorganic flocculant is not used in the step of adding the organic coagulant. The organic property according to any one of claims 1 to 6, wherein the concentration of the organic coagulant having a molecular weight of 1.5 million or less is 200 mg / L or less for metals and 200 mg / L or less for sulfate ion. How to dehydrate sludge. A polymer flocculant having a molecular weight of 2 million or more is added to an organic sludge that satisfies at least one of a soluble calcium concentration range of 10 to 200 mg / L and a sulfate ion concentration range of 0.1 to 200 mg / L. With a coagulation means to coagulate
Concentrating means for concentrating the agglomerated sludge and
A pressure dehydrating means for pressurizing and dehydrating the concentrated sludge,
An organic coagulant adding means for adding an organic coagulant having a molecular weight of 1.5 million or less to the sludge after the concentration or the pressure dehydration.
A dewatering means for mechanically dewatering the sludge to which the organic coagulant is added is included.
At least one of the sludge to which the organic coagulant is added and the dehydrated filtrate thereof has a pH of 6 or more, and the evaporation residue (TS) of the concentrated and pressure-dehydrated sludge is 40 to 150 g / L. A treatment device used for dehydrating organic sludge, which is characterized by being present. It is characterized by having a dividing means provided between the concentration / pressure dehydration means and the organic coagulant addition means to divide the sludge after the concentration and pressure dehydration to form at least a block shape. The treatment apparatus used for dehydrating the organic sludge according to claim 8.

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