JP2936938B2 - Treatment method of human waste and septic tank sludge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of treating human waste and septic tank sludge, and more particularly to a method of mixing human waste and septic tank sludge to remove BOD, COD, nitrogen, phosphorus, chromaticity and the like to a high degree. The present invention relates to a method for efficiently obtaining treated water.

[0002]

2. Description of the Related Art Conventionally, when mixing human waste and the like with septic tank sludge, the mixing ratio of human waste is usually higher, so that
Processing is performed in a mixed processing system that mainly treats night soil.

FIG. 2 shows a flow of a conventional general mixing system. Many facilities based on this processing flow are operating under the name of membrane separation and denitrification processing facility.

In this prior art, even when the septic tank sludge is the main object of treatment, the septic tank sludge and human waste excluding contaminants in the pretreatment are treated by the biological denitrification method, and the membrane is permeated. Since water contains a high concentration of phosphorus, an aggregating / separating apparatus for removing phosphorus, removing COD and removing chromaticity is required.

For this reason, after the SS is generated again by adding an inorganic coagulant to the liquid from which SS has been eliminated by permeating the membrane,
Further, it is necessary to perform solid-liquid separation, and the coagulated sludge generated here also needs to be dehydrated together with excess sludge.

Further, in the step of dehydrating excess sludge, it is necessary to remove high-molecular organic substances accumulated in the biological treatment system by membrane separation to the outside of the system. Therefore, an inorganic coagulant is often used in combination with a polymer. There is also a waste of using the agent in two places for different purposes.

In addition to this example, there is also a method of omitting the coagulation separation and treating the activated carbon as it is (Japanese Patent Publication No. 4-42076)
Publication), COD and chromaticity are removed, but phosphorus is not removed, so that there is no difference in that some dephosphorization equipment is required.

As another example, there is a method of adding a flocculant such as a cationic polymer to human wastewater to dehydrate it, subjecting the separated liquid to biological nitrification and denitrification treatment, and then performing membrane separation. No consideration is given to the removal of phosphorus in the dehydration step of human wastewater, and a nitrification / denitrification treatment and a membrane separation treatment also require a phosphorus removal step.

A dehydration method for removing 90% or more of phosphorus so that a phosphorus removal step is unnecessary after biological treatment in a conventional dehydration step of sewage mainly containing urine has been put to practical use. The reason is that the amount of inorganic coagulant required for phosphorus removal is enormous when human waste is mainly used, and the alkalinity of urine is high.
This is because there are many problems such as a trouble caused by a sudden decrease in the temperature. That is, since night soil contains carbonate ions, if an inorganic coagulant (ferric chloride or sulfate band) is added to insolubilize phosphorus, the consumption of the inorganic coagulant is large, and carbon dioxide gas is generated. It foams and becomes difficult to process.

[0010] The septic tank sludge is separated into separated water and concentrated sludge in an enrichment step by adding an iron-based flocculant.
A method has been proposed in which separated water is subjected to biological treatment, and excess sludge generated in the biological treatment is mixed with the above-mentioned septic tank sludge for treatment (Japanese Patent Laid-Open No. 57-105297).

[0011]

In recent years, it is not uncommon for the ratio of septic tank sludge to be supplied to the mixing process of human waste and the like and septic tank sludge to increase, and the ratio to the night soil to be reversed.
Therefore, there is a demand for the development of a rational mixing system suitable for treating a mixed solution containing a large amount of septic tank sludge as a main treatment target of the septic tank sludge. In the human waste treatment, which is the main treatment target, the phosphorus in the treated water is reduced by 1 m without providing a phosphorus removal step after the biological treatment.
It cannot be removed to a low level of around g / l, and the actual mixing system with human waste considering the characteristics of the properties of septic tank sludge has not yet been developed.

The present invention has been made in view of the above-mentioned conventional circumstances, and BOD, COD, nitrogen, phosphorus, chromaticity and the like are highly removed by a mixing treatment with septic tank sludge and human waste. The purpose is to provide a rational treatment system for obtaining treated water.

[0013]

The method of treating human waste and septic tank sludge according to the present invention is characterized in that, after mixing septic tank sludge with human waste, an inorganic coagulant and a high-molecular coagulant are added and dewatered. A method of biologically nitrifying and denitrifying water, wherein the amount of septic tank sludge mixed with night soil is twice or more that of the night soil.

That is, the present inventors have paid attention to the current situation where the amount of septic tank sludge to be carried in is increasing and the ratio with the night soil is reversed. The present inventors have found a new system that can be realized by eliminating the dephosphorization step after the treatment by using a human waste treatment mainly composed of a septic tank sludge, and have completed the present invention.

In the present invention, the mixing ratio of septic tank sludge to urine or the like indicates a weight ratio.

[0016]

As described above, since night soil contains carbonate ions, in order to insolubilize phosphorus by adding an inorganic coagulant, a large amount of the inorganic coagulant is used, and carbon dioxide gas is generated and foams.
Although dehydration treatment becomes difficult, according to the present invention, mixing of septic tank sludge more than twice as much as human waste into the night soil makes it possible to insolubilize phosphorus with an inorganic coagulant, and 90% of the phosphorus contained in the dehydration process The above can be insolubilized and removed.

[0017] Therefore, it is possible to obtain treated water from which phosphorus is highly removed by a rational treatment without providing a coagulation separation step after the biological treatment.

In addition, the effect of improving the dewatering efficiency and reducing the load on the biological treatment or subsequent post-processes is also exerted, and it is possible to efficiently obtain a dehydrated cake having a low water content and high-quality treated water.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a system diagram showing one embodiment of a method for treating human waste and septic tank sludge according to the present invention. In FIG. 1, 1 and 2 are receiving tanks, 3 is a pretreatment step, 4, 5, and 10 are storage tanks, 6 is a reaction tank, 7 is a granulation and concentration tank, 8 is an incineration step,
9 is a dehydrator, 11 is a biological reaction tank (biological nitrification / denitrification treatment step), 12 is a membrane separation device, 13 is an activated carbon treatment device,
Reference numerals 21 to 25, 27 to 34, and 36 to 41 indicate piping. 26 and 35 are conveyors.

In the illustrated method, an inorganic coagulant and an amphoteric polymer are added to a mixed solution having a ratio of human waste septic tank sludge to urine of 2: 1 or more and a large amount of urine septic tank sludge, followed by dehydration treatment. The filtrate is subjected to a biological nitrification and denitrification treatment in a biological reaction tank, and the treated liquid is separated into a permeate and a concentrate by a membrane separation device. Is activated carbon treatment.

Manure passes through the pipe 21, the receiving tank 1 and the pipe 23, and after impurities are removed in the pretreatment step 3, is stored in the storage tank 4 through the pipe 25. The human waste septic tank sludge passes through the pipe 22, the receiving tank 2, and the pipe 24, and is subjected to a pretreatment step 3.
After the contaminants are removed in the above, the contaminants are stored in the storage tank 5 via the pipe 27. Manure in the storage tank 4 is introduced into the storage tank 5 from the pipe 28 at a predetermined ratio and mixed. The contaminants (waste) removed in the pretreatment step 3 are sent from the conveyor 26 to the incineration step 8.

In the storage tank 5, a mixed liquid in which human waste and urine septic tank sludge are mixed at a predetermined ratio (in this embodiment, furthermore,
Excess sludge in the biological reaction tank 11 described below is mixed. )
It is introduced into the reaction tank 6 from a pipe 29 and reformed by the addition of an inorganic coagulant from a pipe 30 to insolubilize phosphorus and high-molecular organic substances contained in septic tank sludge and night soil. Here, the inorganic coagulant is preferably added so that 90% or more of the phosphorus in the mixed solution is insolubilized. The insolubilized solution in the reaction tank 6 is introduced into the granulation and concentration tank 7 through the pipe 31, and is subjected to granulation and concentration by addition of the amphoteric polymer from the pipe 32 to form a strong floc. The flocked or granulated liquid is led to the dehydrator 9 through the pipe 33 to be subjected to dehydration treatment.
In this dehydration treatment, a strong floc is formed in the liquid to be dehydrated, and a large amount of fiber is contained in septic tank sludge and human waste, so that a dehydrated cake having a low water content can be obtained. Can be.

By this dehydration treatment, usually, more than 95% of SS and more than 90% of phosphorus in urine as septic tank sludge,
60 to 70% or more of BOD, COD and organic nitrogen are discharged out of the system as a dehydrated cake. On the other hand, BOD and COD in the separated liquid or the filtrate are mainly composed of low molecular substances that are easily biotreated, and contain only a small amount of phosphorus.

The dewatered cake obtained by the dehydration treatment is sent from the conveyor 35 to the incineration step 8, while the separated liquid or filtrate is sent to the biological reaction tank 11 via the pipe 34, the storage tank 10 and the pipe 36. Is done.

In the biological reaction tank 11, not only BOD but also nitrogen in the separated solution or the filtrate are removed by biological nitrification and denitrification.

In this biological nitrification and denitrification treatment, most of organic matter in urine as septic tank sludge is removed in the preceding dehydration step, and the properties of the liquid introduced into the biological reaction tank are as follows. Since the properties are the same as those obtained by diluting, the load of biological treatment is reduced, and the capacity of the reaction tank and the required amount of oxygen can be reduced. In particular, the capacity of the nitrification tank is determined as a capacity that can secure not only the load of nitrogen but also the required amount of sludge.
When the inflow of the SS-based substance is small, the amount of excess sludge pulled out can be small, so that the amount of sludge can be easily secured and stable nitrification is performed.

Excess sludge generated in the biological reaction tank 11 can be returned to the storage tank 5 through the pipe 37 and processed together with night soil and human waste purification tank sludge.

The biologically treated water containing microorganisms obtained in the biological reaction tank 11 is then sent from a pipe 38 to a membrane separation device 12 to be subjected to a membrane separation treatment and separated into a permeate and a concentrate. The concentrated liquid is used for maintaining the sludge concentration in the biological reaction tank 11.
A part of the sludge is returned as sludge from the pipe 40 to the biological
Return to. By adopting this membrane separation treatment, a high concentration of activated sludge is maintained in the biological reaction tank 11, so that a stable nitrification and denitrification treatment is performed.

The membrane permeate obtained by the membrane separation treatment contains S
S is not contained at all, and nitrogen and phosphorus are also highly removed. Septic tank sludge and night soil are dewatered to remove SS and colloidal organic matter, and the biologically treated separation liquid or filtrate is subjected to membrane separation. COD and chromaticity of the membrane permeate are lower than in the case of processing,
The load on the subsequent activated carbon treatment tank is greatly reduced.

Since the membrane permeate obtained by this membrane separation treatment is still colored and the COD is often not at a satisfactory level, the activated carbon treatment apparatus 13 is connected through the pipe 39.
To remove residual chromaticity and COD, to obtain a colorless and transparent final treated water, which is discharged from a pipe 41. In this activated carbon treatment, since the membrane permeate does not contain SS, there is no need to worry about clogging of the activated carbon adsorption tower, and backwashing is almost unnecessary.

In the present invention, the mixing ratio of human waste and septic tank sludge is set to be twice or more that of the human septic tank sludge, but there is no particular upper limit to the ratio of the septic tank sludge.

In the present invention, if necessary, surplus sludge discharged from the biological nitrification / denitrification treatment step may be mixed into the septic tank sludge and urine. In this case, the properties of the surplus sludge Is a property close to the septic tank sludge, so that if the combined amount of the septic tank sludge and the excess sludge is at least twice the amount of the human waste, a reasonable mixing process with the human waste can be performed.

When the excess sludge is mixed, the high molecular organic matter in the excess sludge can be simultaneously flocculated in the dehydration step, so that the high molecular organic matter accumulated in the biological treatment system by the membrane separation treatment can be taken out of the system. Yes, it is very advantageous.

In the present invention, first, an inorganic coagulant is added to a mixed liquid obtained by mixing septic tank sludge, night soil, etc. and, if necessary, the above-mentioned excess sludge. Iron polysulfate or the like can be used, and the amount of such an inorganic coagulant added is 90% of the phosphorus in the mixed solution.
% Or more is preferably an amount that can be insolubilized.

The amount of the inorganic coagulant added must be sufficient to allow the metal such as iron to react with phosphorus in the septic tank sludge or human waste to produce iron phosphate and the like. It is necessary to use iron in a molar ratio of 1.0 to 1.5 or more with respect to phosphorus therein.

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

Examples of the (A) cationic monomer forming the cationic structural 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-hydroxyacrylate or methacrylate, dimethylaminomethylacrylamide or methacrylamide, dimethylaminoethylacrylamide or methacrylamide, dimethylaminopropyl alcohol 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 quaternary compounds. Acids used for the tertiary salt include, for example, hydrochloric acid, sulfuric acid, nitric acid, formic acid, acetic acid and the like, while quaternizing agents include, for example, methyl chloride, methyl iodide, benzyl chloride, dimethyl sulfate, diethyl sulfate Sulfuric acid, ethyl chloride, ethyl iodide and the like. The cationic monomer may be used alone, or two or more kinds may be used in combination.

Examples of (B) the anionic polymer forming the anionic constitutional unit include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and ethacrylic acid, and their sodium, potassium, and ammonium salts, and further include vinyl. Sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid and its sodium salt, potassium salt, ammonium salt and the like can be mentioned. One of these anionic polymers may be used, or two or more may be used in combination.

Further, the monomer which forms the nonionic structural unit (C) optionally introduced includes, for example, vinyl group-containing amides such as acrylamide, methacrylamide, dimethylacrylamide and dimethylmethacrylamide, acrylonitrile and methacrylonitrile. Vinyl cyanide compounds, alkyl (meth) acrylates such as methyl acrylate, ethyl acrylate, methyl methacrylate and ethyl methacrylate, vinyl carboxylate such as vinyl acetate, styrene, α
And aromatic vinyl compounds such as -methylstyrene and p-methylstyrene. One of these monomers may be used, or two or more thereof may be used in combination.

The amount of the amphoteric polymer to be added is appropriately determined according to the properties of the mixed solution, but is usually about 0.5 to 2.0% by weight based on the solid.

In the present invention, the above-mentioned amphoteric polymer is most preferably used as the polymer flocculant. By using the amphoteric polymer, efficient granulation and concentration can be carried out in a granulation and concentration tank. In addition, the advantage that the dehydration capacity of the dehydrator can be brought out greatly is obtained,
The polymer flocculant is not limited to an amphoteric polymer, and other types of polymers such as a cationic polymer may be used.

As a membrane for the membrane separation treatment after the biological nitrification / denitrification treatment, an ultrafiltration membrane is generally used, but other types of membranes such as a microfiltration membrane can also be used.

Hereinafter, the present invention will be described in more detail with reference to specific examples and comparative examples.

Example 1 Processing was performed according to the method of the present invention shown in FIG. Septic tank sludge, night soil and surplus sludge from nitrification and denitrification treatment in the post-process are mixed at a ratio of 2: 1: 1, and SS: 10500 mg
/ L, BOD: 3700 mg / l, COD: 3700 m
g / l, TN: 810 mg / l, PO ₄ -P: 140
A mixed solution of mg / l was obtained.

To this mixture was added ferric chloride (38% aqueous solution)
Was added and the amphoteric polymer was added in an amount of 130 mg / l, the mixture was refined, granulated, and dehydrated with a belt press dehydrator. As a result, a dehydrated cake having a low water content of 73.2% was obtained. As the amphoteric polymer, a copolymer composed of dimethylaminoethyl acrylate, acrylamide, and acrylic acid was used.

Here, iron in 3000 mg / l of ferric chloride is added in a molar ratio of 1.55 to PO ₄ -P in the mixed solution.
Times the amount of PO ₄ -P in the dehydrated filtrate (excluding washing water).
Was as low as 3.3 mg / l. SS is 13
0 mg / l, BOD is 1480 mg / l, COD is 10
20 mg / l and TN were 615 mg / l.

The dehydrated filtrate is used as raw water for biological nitrification.
A denitrification treatment was performed, and the treated liquid was subjected to solid-liquid separation using an ultrafiltration membrane. The properties of the obtained permeated water were not detected: SS: not detected, BOD: 3 mg / l, COD: 60 mg / l,
TN: 12 mg / l, PO ₄ -P: 0.5 mg / l,
Chromaticity: 200 degrees.

Further, by treating the permeated water with activated carbon, BOD: 2.5 mg / l, COD: 20 mg / l
1, TN: 8.5 mg / l, PO ₄ -P: 0.4 mg
/ L, chromaticity: 30 ° C., high-quality final treated water could be obtained.

From these results, according to the method of the present invention, BOD, COD, BOD, COD,
Obviously, it is possible to obtain treated water from which nitrogen, phosphorus and chromaticity are highly removed.

Comparative Example 1 The mixing ratio of septic tank sludge, night soil and surplus sludge from the nitrification and denitrification treatment was set to 1: 2: 1, and the ratio of urine was increased, and SS: 11
800 mg / l, BOD: 7900 mg / l, COD:
4800 mg / l, T-N: 2150 mg / l, PO ₄
-P: A mixed liquid of 270 mg / l was obtained, and the mixed liquid was treated in the same manner as in Example 1.

As a result, the refining of the mixed solution requires 6000 mg / l of ferric chloride (38% aqueous solution) and 280 mg / l of the amphoteric polymer, which is about twice as large as that of Example 1. In the process of injecting and mixing ferric chloride, foaming was severe, and air bubbles adhered to the sludge, deteriorating dehydration.

From these results, it can be seen that it is difficult to remove nearly 90% of phosphorus by dehydration with an inorganic coagulant and a polymer in the case of mainly human waste.

Comparative Example 2 In Example 1, the septic tank sludge, human waste and excess sludge were used in a ratio of 2: 1 without addition of the inorganic flocculant and the amphoteric polymer.
When the mixture obtained by mixing at a ratio of 1 was subjected to nitrification and denitrification treatment by the conventional method shown in FIG. 2 and then subjected to ultrafiltration membrane separation, the quality of the permeated water obtained was BOD: 4 mg / l, TN:
Although there was no difference between 15 mg / l and the permeated water in Example 1, PO ₄ -P was as high as 85 mg / l, and a dephosphorization facility was required. COD is 105 mg /
l, the chromaticity is 440 degrees, which is about twice the concentration of Example 1, and the burden on the activated carbon treatment is large. Therefore, if economical efficiency is taken into consideration, a coagulation / separation facility that also serves the purpose of dephosphorization is indispensable. It was confirmed that there was.

[0055]

As described in detail above, according to the method for treating night soil and septic tank sludge of the present invention, an inorganic coagulant and a high-molecular coagulant are added to a mixed solution of night soil and septic tank sludge for dehydration. By using a large amount of coagulant,
It is possible to highly remove phosphorus without causing dehydration inhibition such as foaming. Therefore, treated water from which phosphorus has been highly removed can be obtained without providing a coagulation separation step after biological treatment. Even if the coagulation separation step is not performed after the biological treatment, the load of the subsequent activated carbon treatment is not excessive, and the final treated water from which the COD and the chromaticity are highly removed can be obtained. Since the coagulated liquid used for dehydration has excellent dehydration characteristics, the dehydrator can exhibit a high sludge treatment capacity, and a dewatered cake having a low water content can be obtained. Since the load of the biological denitrification treatment is reduced, treated water from which nitrogen is highly removed can be obtained even if the capacity of the reaction tank or the required amount of oxygen is reduced. Such as BOD, COD, nitrogen, phosphorus,
It is possible to efficiently obtain high-quality treated water from which chromaticity and the like are highly removed.

[Brief description of the drawings]

FIG. 1 is a system diagram showing one embodiment of a method for treating human waste and septic tank sludge according to the present invention.

FIG. 2 is a system diagram showing a conventional processing method.

[Explanation of symbols]

 1, 2 receiving tank 3 pretreatment step 4, 5, 10 storage tank 6 reaction tank 7 granulation concentration tank 8 incineration step 9 dehydrator 11 biological reaction tank 12 membrane separation device 13 activated carbon treatment device

Claims (1)

(57) [Claims] 1. A method of mixing a septic tank sludge with human waste, dehydrating by adding an inorganic coagulant and a polymer coagulant, and subjecting the obtained dewatered separated water to a biological nitrification / denitrification treatment, A method for treating night soil and septic tank sludge, wherein the amount of septic tank sludge mixed with night soil is at least twice the amount of the night soil.