JP3389832B2 - How to treat human waste - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for treating organic sludge and the like such as human waste and septic tank sludge, and in particular, by anaerobic digestion treatment of coagulated concentrated sludge to which an inorganic coagulant and an amphoteric polymer coagulant are added. The present invention relates to a method for enhancing the anaerobic digestion efficiency and improving the water quality of concentrated separated water and digested / desorbed liquid.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional method for mixing human waste and septic tank sludge to perform anaerobic digestion treatment. As shown in the figure, human waste is directly supplied to the anaerobic digestion step. When the solid content of the septic tank is low, the sludge is gravity-concentrated to about 1 to 2% in the concentrating tank 1 or concentrated to about 2 to 4% by adding a coagulant, and then supplied to the anaerobic digestion step 2. Then, anaerobic digestion treatment is performed together with the above-mentioned human waste. The digested desorbed liquid in the anaerobic digestion step 2 and the concentrated separated water in the concentration tank 1 are further nitrified and denitrified in the activated sludge treatment step 3, and the treated water is discharged out of the system. Further, the methane produced in the digestion treatment of the digestion tank in the anaerobic digestion step 2 is generally used as a heating heat source for the digestion tank.

[0003]

The above-mentioned conventional processing method has the following problems.

Since the solid matter concentration of human waste or concentrated septic tank sludge introduced into the anaerobic digestion step 2 is as low as 1 to 4% at most, a large amount of heat is required to heat the anaerobic digestion tank. Moreover, the decomposition efficiency of organic substances by digestion is also low. Since the concentration of COD, chromaticity, phosphorus, etc. in the digested and desorbed liquid is high, the load when performing activated sludge treatment in the latter stage is large.
In addition, chromaticity and phosphorus are hardly removed even when the activated sludge treatment is performed. Since the quality of the concentrated separated water is also poor, the load of activated sludge treatment is large from this point as well.

The present invention solves the above-mentioned conventional problems and enhances the heat efficiency and decomposition efficiency of anaerobic digestion in a method for concentrating organic sludge such as human waste and septic tank sludge to perform anaerobic digestion treatment, as well as concentrated and separated water. It is also an object of the present invention to provide a method for treating human urine and the like that can improve the water quality of the digested and desorbed liquid.

[0006]

Means for Solving the Problems The method for treating night soil, etc. according to the present invention comprises adding an inorganic flocculant to human waste and / or organic sludge, then adding an amphoteric polymer flocculant, and stirring the mixture to 5% by weight or more.
It is characterized in that it is granulated and concentrated to a solid concentration of, and the concentrate is subjected to anaerobic digestion.

In the present invention, an inorganic coagulant is added to organic sludge such as night soil, septic tank sludge, and surplus sludge (hereinafter, these night soil and sludge may be collectively referred to as "raw mud") and reacted. This neutralizes the charge of the negatively charged particles. The inorganic coagulant also has an action of insolubilizing organic matter, phosphorus, etc. suspended or dissolved in the raw mud and incorporating it into the coagulated sludge.

By adding an amphoteric polymer flocculant (hereinafter referred to as "amphoteric polymer") to the charge-neutralized sludge, and granulating and concentrating the sludge, a concentrated sludge having a high solid content can be obtained. The quality of the concentrated separated water is also good.

Further, by anaerobically digesting the concentrated sludge having such a high solid content, the heat efficiency and decomposition efficiency of the anaerobic digestion are improved, and the water quality of the digestion / desorption liquid is also improved.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

1 and 2 are system diagrams showing an embodiment of the method for treating human waste and the like according to the present invention.

In the method shown in FIG. 1, raw mud, that is, human waste, septic tank sludge, surplus sludge and the like are introduced into the flocculation reaction tank 1, and an inorganic flocculant is added and stirred, and then an amphoteric polymer is added. Stir to aggregate and then slowly agitate to granulate.

In the present invention, as the inorganic coagulant, an iron salt such as ferric chloride or polyiron sulfate or an aluminum salt such as aluminum sulfate can be used. By using the iron salt, the sulfide in the raw mud can be used. Is preferably used as an iron salt because it can be insolubilized as iron sulfide and the generation of hydrogen sulfide that is an inhibitor of anaerobic digestion can be suppressed.

The amount of the inorganic coagulant added varies depending on the properties of the raw mud and the like, but when treating human waste and septic tank sludge mixture, the pH after the addition of the inorganic coagulant is 5.2 to 6.2. It is preferable to add an inorganic coagulant so as to be in the range.

The amphoteric polymer is usually composed of a copolymer containing (A) a cationic constitutional unit, (B) an anionic constitutional unit and optionally (C) a nonionic constitutional unit in one molecule. Things are used.

Examples of the cationic monomer forming the (A) cationic constitutional unit include dimethylaminomethyl acrylate or methacrylate, dimethylaminoethyl acrylate or methacrylate, dimethylaminopropyl acrylate or methacrylate, dimethylamino-2-hydroxypropyl acrylate. Or methacrylate, diethylaminomethyl acrylate or methacrylate, diethylaminoethyl acrylate or methacrylate, diethylaminopropyl acrylate or methacrylate, diethylamino-2-hydroxy acrylate or methacrylate, dimethylaminomethyl acrylamide or methacrylamide, dimethylaminoethyl acrylamide or methacrylamide, dimethylaminopropyl acrylate Riruamido or methacrylamide,
Tertiary salts such as dimethylamino-2-hydroxypropylacrylamide or methacrylamide, diethylaminomethylacrylamide or methacrylamide, diethylaminoethylacrylamide or methacrylamide, diethylaminopropylacrylamide or methacrylamide, diethylamino-2-hydroxypropylacrylamide or methacrylamide, and Examples include quaternary compounds. Examples of the acid used for the tertiary salt include hydrochloric acid, sulfuric acid, nitric acid, formic acid, acetic acid and the like, while examples of the quaternizing agent include methyl chloride, methyl iodide, benzyl chloride, dimethylsulfate and diethyl. Examples thereof include sulfuric acid, ethyl chloride and ethyl iodide. The cationic monomer may be used alone or in combination of two or more.

Examples of the anionic polymer (B) forming the anionic constitutional unit include unsaturated carboxylic acids such as acrylic acid, methacrylic acid and ethacrylic acid, and their sodium salts, potassium salts, ammonium salts, and vinyl. Examples thereof include sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid and sodium salts, potassium salts and ammonium salts thereof. These anionic polymers may be used alone or in combination of two or more.

Further, as the monomer for forming the nonionic constitutional unit (C), which is optionally introduced, vinyl group-containing amides such as acrylamide, methacrylamide, dimethylacrylamide and dimethylmethacrylamide, acrylonitrile and methacrylonitrile, etc. Vinyl cyanide compounds, alkyl acrylates of (meth) acrylic acid such as methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate, vinyl esters of carboxylic acids such as vinyl acetate, styrene, α
-Aromatic vinyl compounds such as methyl styrene and p-methyl styrene are included. These monomers may be used alone or in combination of two or more.

The amount of such an amphoteric polymer added is appropriately determined according to the properties of the raw mud and the like, but is usually about 0.5 to 2.0% by weight based on the solid matter.

Granulation of the sludge after the addition of the inorganic coagulant and the amphoteric polymer is carried out by slowly stirring in the coagulation reaction tank 1 equipped with a stirring blade. The granulated sludge is then concentrated by dehydrating it with the screen 5.

The granulated sludge obtained by adding an inorganic coagulant and an amphoteric polymer according to the present invention and granulating the granulated sludge can be easily separated by a screen 5 having a simple structure without using a sludge dehydrator or the like. It can be concentrated, whereby a granulated concentrated sludge having a solid matter concentration of 5 to 10% by weight or more can be obtained.

Here, the opening of the screen may be of a size that allows the coarse granulated sludge to be separated,
About 0.5 to 3.0 mm is suitable.

The granulated concentrated sludge is then subjected to an anaerobic digestion process in an anaerobic digestion step 2.

In this anaerobic digestion process, the temperature in the digestion tank must be maintained at around 37 ° C. for medium temperature digestion and around 55 ° C. for high temperature digestion. It is necessary to heat by blowing.

When the solid content is the same, the heat energy required for this heating is smaller as the solid content is higher. Therefore, the conventional method in which a material having a solid content of about 1 to 4% by weight is charged is required. In comparison, according to the method of the present invention in which the sludge having a granulation concentration of 5 to 10% by weight or more is added, efficient digestion treatment can be performed with a small amount of heat energy.

Further, the reaction time of anaerobic digestion becomes longer as the solid concentration becomes higher, so that according to the present invention, decomposition of organic substances can be promoted and digestion efficiency can be enhanced.

The digested desorbed liquid of the anaerobic digestion step 2 is then introduced into the activated sludge treatment step 3 together with the concentrated separated water of the screen 5 and is subjected to the activated sludge treatment (nitrification / denitrification treatment).

The concentrated separated water and the digestive desorption liquid introduced into the activated sludge treatment step 3 are obtained by treating the raw mud with the inorganic coagulant and the amphoteric polymer, and therefore, the concentrated separated water and the separated water obtained by the conventional method are used. The water quality is better than that of digestive desorption fluid,
In particular, since COD and the concentration of chromaticity and phosphorus that are difficult to remove by activated sludge treatment are low, treated water of good water quality can be obtained by activated sludge treatment.

The method shown in FIG. 1 is a case where the raw mud is treated in a batch system. When the raw mud is continuously treated, a mixing tank of an inorganic flocculant and a flocculation reaction by an amphoteric polymer are carried out. It is preferable to arrange the tanks and, if necessary, the granulation tanks in series.

Further, in the method shown in FIG. 1, granulation is carried out by using a flocculation reaction tank without a filtering section. Therefore, although a screen 5 is separately provided for dehydration concentration, granulation having a filtering section is carried out. Granulation and concentration may be performed in a concentration tank.

FIG. 2 shows a method of carrying out the granulation concentration using the granulation concentration tank 7 having the filtration section as described above. Raw mud is first mixed in the mixing tank 6 by adding an inorganic coagulant. The type of the inorganic coagulant and the addition amount thereof are as described above.

The raw mud mixed with the inorganic coagulant is then introduced into the granulation concentrating tank 7, and the amphoteric polymer is added thereto. With stirring, as in the case of FIG. 1, the solid concentration is 5 to 10% by weight or more. Aggregate and granulate to concentrate. The kind of the amphoteric polymer and the addition amount thereof are also as described above. The granulated thickened sludge and the concentrated separated water in the granulated thickening tank 7 are treated in the same manner as in the case of FIG.

Next, with reference to FIGS. 4 and 5, the structure of the granulation concentrating tank and the granulation concentrating mechanism suitable for the present invention will be described.

FIG. 4 is a partially sectional perspective view showing this granulation concentrating tank, and FIG. 5 is a plan view of the same.

Reference numeral 11 is a cylindrical tank, and an agitator M is provided at the center of the cylindrical tank 11. The stirrer M includes a motor, a rotary shaft 12 that is rotationally driven by a transmission, and stirrer blades 13 and 14 that are radially provided in two stages above and below the rotary shaft 12 at a phase of 180 °. . Filtering unit 1
0 is a bottomed filter cylinder 17 that is a little smaller than a semicircle installed along the arcuate portion of the same curvature on the inner circumference of the cylindrical tank 11,
The bottom 17 'of the filter cylinder 17 is provided with a large number of arc-shaped slits 18 concentrically provided with the cylindrical tank 11.

The filter cylinder 17 is provided with a hook 15. The filter cylinder 17 is fixed by engaging the hook 15 with the upper edge of the cylindrical tank 11.

The upper end of the filter cylinder 17 and the upper end of the cylindrical tank 11 are at the same level. The bottom 17 'of the filter cylinder 17 is separated from the upper edge of the upper stirring blade 13 by only about 1 to 10 mm and is close to it. If necessary, a rubber plate may be attached to the upper edge of the stirring blade 13, and the bottom 17 ′ of the filtration cylinder 17 may be rubbed with this rubber plate during rotation. The width of the slit 18 is 5 mm or less, preferably about 1 to 2 mm, the interval between the circumferentially adjacent slits is about 2 mm, and the interval between the radially adjacent slits is about 5 mm.

It is preferable that the upper stirring blade 13 is a flat plate having a constant vertical width over the entire length from the base fixed to the rotary shaft 12 to the tip as shown in the figure.

The cylindrical tank 11 is also provided with a drain pipe 10A for discharging filtered water (separated water) from the inside of the filter cylinder 17 through the tank wall.

The raw mud mixed with the inorganic coagulant and the amphoteric polymer, which are respectively supplied from the supply pipe 10B and the chemical injection pipe 10C to the central portion of the bottom of the tank, are mixed with the stirring blade 13 attached to the rotary shaft 12. By the stirring action of Nos. 14, 14, they are uniformly mixed and react while they are stagnant in the tank. The water (separated water) that has flowed into the filtration cylinder 17 through the slit 18 at the bottom of the filtration cylinder 17 is discharged from the drain pipe 10A to the outside of the tank by the pump P. As a result, the raw water continuously supplied is sufficiently concentrated and becomes a granulated product having high strength. This granulated product is discharged from the mud discharge pipe 10D.

Immediately below the bottom 17 'of the filter cylinder 17, the stirring blade 13 swirls to cause a horizontal swirling flow a.
Occurs. Slit 18 provided on the bottom 17 'of the filter cylinder 17
Is a concentric arc along the horizontal swirl flow a. Therefore, flocculated flocs and fibrous substances in the liquid are
It flows under 7'in the same direction as the extending direction of the slit 18.
As a result, the flocs and the like do not get caught in the slits 18, and the agglomerated flocs roll under the bottom 17 'to become a denser and stronger granule.

In the lower stirring blade 14, the vertical width of the base 20 on the side attached to the rotary shaft 12 is about half of the total length, and the vertical width of the remaining free end 21 is large. A battledore shape is preferred. In this way, under the horizontal swirl flow a generated by the upper stirring blade 13, the lower battledore stirring blade 14 pushes the liquid outward at the wide free end portion 21, and the flow swirls to the inner circumference of the tank. In the vicinity, it is divided into an upflow b and a downflow b ', and the upflow b comes into contact with the horizontal swirl flow a by the upper flat plate stirring blade 13 and descends toward the center portion, and the downflow b'is the bottom surface of the tank. Around the center of the tank, a vertical circulating flow is generated, which swirls up and down in the center and bottom of the tank, and the raw mud and amphoteric polymer supplied to the center of the bottom of the tank flow into these streams b and b '. It efficiently mixes and contacts the flocculation flocs that have already formed, and agglomerates and granulates well. Then, as shown in the drawing, when the wide free end 21 is bent at an angle (for example, 45 °) so as to recede with respect to the swirling direction of the blade, the force for pushing the liquid toward the inner circumference of the tank is further increased by the free end. As a result, the swirling circulation flows b and b'are strengthened and stronger, so that the mixing and contact efficiencies are further improved. Further, a straight line that is located at the lower end of the inner circumference of the cylindrical tank 11 and in the middle of the upper stirring blade 13 and the lower stirring blade 14 extends in the swirling direction of the stirring blade, and gradually departs from the inner circumference toward the tip. If the guide plates 22 and 23 having a curved shape as shown in the drawing are provided,
The upper circulation flow b flows downward along the horizontal swirling flow a and then downwards at the center, and the lower circulation flow b ′ along the bottom of the tank and then upwards at the center. It is possible to improve mixing and contact efficiency in the same manner.

Although the case where the filtration tank is provided inside the cylindrical tank has been described above, the filtration tank may be provided outside the cylindrical tank.

[0044]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below.

Example 1 20% and 70% of human waste, septic tank sludge and excess sludge,
The mixture mixed at a ratio of 10% (weight ratio) was used as raw mud (solid concentration 10,600 mg / L) and treated by the method shown in FIG.

First, in the flocculation reaction tank 4, ferric chloride (3,000 mg / L) was added to the raw mud to adjust the pH to 6, and
Amphoteric polymer (Kuribest P702 manufactured by Kurita Water Industries Ltd.)
Of 100 mg / L was added, and the mixture was stirred and mixed, and further slowly stirred to perform coarse granulation of the sludge.

The obtained granulated sludge was dehydrated and concentrated with a screen 5 having an opening of 0.5 mm to obtain a concentrated granulated sludge having a solid content of 8% by weight. The concentration of SS in the concentrated separated water is 250 mg / L
Met.

The granulated concentrated sludge was put into the anaerobic digestion tank of the anaerobic digestion step 2 once a day for a retention period of 2 weeks, and the temperature in the tank was maintained at 37 ° C. The generated amount of methane gas was 12 L per 1 kg of the granulated concentrated sludge charged. The digestion desorption liquid obtained by centrifuging the sludge in the digestion tank is the activated sludge treatment step 1 together with the concentrated separation water of the screen 5.
Then, nitrification and denitrification were performed to obtain treated water.

Table 1 shows the water quality and treatment amount of the raw mud, concentrated separated water, granulated concentrated sludge, digested desorption liquid, and activated sludge treated water in the above treatment.

[0050]

[Table 1]

Example 2 Raw mud similar to that treated in Example 1 was treated by the method shown in FIG.

First, ferric chloride is added to the raw mud in the mixing tank 6
After adjusting the pH to 6 by adding 000 mg / L, the mixture was supplied to the granulation concentrating tank 7, and 100 mg / L of the same amphoteric polymer as that used in Example 1 was added and slowly stirred to granulate. ,
The obtained granulated concentrated sludge was fed to the anaerobic digestion step 2 and treated in the same manner as in Example 1. Further, the concentrated and separated water in the granulating and concentrating tank 7 was also treated with the digested and desorbed liquid in the same manner as in Example 1.

In the above treatment, the amount of methane gas generated by anaerobic digestion was 9.
It was 2L. Table 2 shows the water quality and treatment amount of the raw mud, concentrated separated water, granulated concentrated sludge, digestive desorption liquid, and activated sludge treated water.

[0054]

[Table 2]

Comparative Example 1 Human waste, septic tank sludge and excess sludge similar to those treated in Example 1 were treated in the same proportions as in Example 1.

The human waste was directly introduced into the anaerobic digestion step 2, and the septic tank sludge and the excess sludge were concentrated in the concentration tank 1 and then introduced into the anaerobic digestion step 2 and subjected to the anaerobic digestion treatment in the same manner as in Example 1. Then, the concentrated and separated water in the concentrating tank 1 was treated with activated sludge in the same manner as in Example 1 together with the digestive desorption liquid.

In the above treatment, the amount of methane gas generated by anaerobic digestion was 3.1 L per 1 kg of the concentrated sludge charged.
Met. In addition, concentrated separated water, concentrated sludge, digestive desorption liquid,
The water quality and treatment amount of the activated sludge treated water were as shown in Table 3.

[0058]

[Table 3]

From the above results, according to the present invention, since the granulated concentrated sludge having a high solid content concentration can be anaerobically digested, the thermal efficiency and the decomposition efficiency of the anaerobic digestion are high, and the water quality is good by the subsequent activated sludge treatment. In particular, it can be seen that treated water having a low COD and low T-P can be obtained.

[0060]

As described in detail above, according to the method for treating human waste and the like of the present invention, in the method for concentrating and anaerobically digesting organic sludge such as human waste and septic tank sludge, the thermal efficiency and decomposition of anaerobic digestion are achieved. It is possible to improve the efficiency and improve the water quality of the concentrated separated water and the digested / desorbed liquid. Therefore, the load of the activated sludge treatment after the anaerobic digestion treatment is also reduced, and the treated water of high quality can be efficiently obtained.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of an embodiment of a method for treating human waste, etc. according to the present invention.

FIG. 2 is a system diagram showing another example of the embodiment of the method for treating human waste etc. of the present invention.

FIG. 3 is a system diagram showing a conventional method.

FIG. 4 is a partial cross-sectional perspective view showing a granulation concentrating tank suitable for the present invention.

5 is a plan view of the granulation concentration tank of FIG.

[Explanation of symbols]

1 thickener 2 Anaerobic digestion process 3 Activated sludge treatment process 4 Aggregation reaction tank 5 screen 6 mixing tanks 7 Granulation thickener 10 Filter 11 cylindrical tank 12 rotation axes 13,14 Stirring blade 17 Filter cylinder M stirrer

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-3-52700 (JP, A) JP-A-4-131199 (JP, A) JP-A-7-256298 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C02F 11/04 C02F 11/14 C02F 3/28

Claims (4)

(57) [Claims] 1. An inorganic flocculant is added to human waste and / or organic sludge, and then an amphoteric polymer flocculant is added, and the mixture is agitated to form a 5-fold mixture.
A method for treating human waste or the like, which comprises granulating and concentrating to a solid content concentration of not less than amount% and subjecting the concentrate to anaerobic digestion treatment. 2. Granulation concentration is performed after granulation in a coagulation reaction tank,
The method for treating human waste according to claim 1, which is performed by concentrating with a screen. 3. The method for treating human excrement according to claim 1, wherein the granulation and concentration are performed by granulating in a granulating and concentrating tank having a filtering section, and removing and concentrating the filtrate from the filtering section. 4. The inorganic coagulant is an iron salt.
The treatment of human waste or the like according to any one of claims 1 to 3.
Reasoning method.