JPH06226290A - Treatment of night soil and septic tank sludge - Google Patents

Abstract

PURPOSE:To provide a rational treating system for obtaining treated water from which BOD, COD, nitrogen, phosphorus, chromaticity, etc., are removed at a high degree by a mixing treatment with night soil, etc., consisting mainly of septic tank sludge. CONSTITUTION:The septic tank sludge of >=2-times the night soil is mixed with the night soil and thereafter, an inorg. flocculating agent and a high-polymer flocculating agent are added to the mixture and the mixture is dehydrated. The dehydration separated water obtd. in such a manner is subjected to biological nitrification and denitrification treatments. The insolubilization of the phosphorus by the inorg. flocculating agent is enabled by mixing the septic tank sludge of iota2 times the night soil with the night soil. The insolubilization and removal of >=90% of the phosphorous contained in the night soil are enabled by the dehydration treatment. Then, the provision of the flocculation sepn. stage after the biological treatment is not necessitated and the treated water from which the phosphorus is removed at the high level is obtd. by the rational treatment. The improvement of the dehydration efficiency, the decrease in the load on the biological treatment or the subsequent post stages are obtd. The dehydrated cake of a low moisture content and the treated water having the high water quality are efficiently obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating human waste and septic tank sludge, and in particular, it has a high removal rate of BOD, COD, nitrogen, phosphorus, chromaticity and the like by mixing human waste and septic tank sludge. The present invention relates to a method for efficiently obtaining treated water.

[0002]

2. Description of the Related Art Conventionally, when human waste and the like and septic tank sludge are mixed and processed, since the human waste usually has a larger mixing ratio,
The treatment is performed in a mixed treatment system that mainly treats human waste.

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

In this prior art, even when the main treatment object is the septic tank sludge, the septic tank sludge and human urine from which the contaminants have been removed by the pretreatment are treated by the biological denitrification method, and the membrane is permeated. Since phosphorus is contained in water at a high concentration, an aggregating / separating device for dephosphorization, COD, and chromaticity removal is required.

Therefore, after the inorganic coagulant is added to the liquid which has passed through the membrane to eliminate SS, the SS is generated again,
Further, it is necessary to perform solid-liquid separation, and the coagulated sludge generated here also needs to be dehydrated together with the excess sludge.

In the process of dehydrating excess sludge, since it is necessary to take out the high molecular weight organic matter accumulated in the biological treatment system by membrane separation to the outside of the system, an inorganic coagulant is often used in combination with the polymer, and the inorganic coagulant is often used. There is also a waste of using the agent in two places for different purposes.

In addition to this example, there is a method in which coagulation separation is omitted and the activated carbon is directly treated (Japanese Patent Publication No. 4-42076).
However, since phosphorus is not removed although COD and chromaticity are removed, there is no difference in that some kind of phosphorus removal equipment is required.

As another example, there is a method in which a coagulant such as a cationic polymer is added to human waste sewage for dehydration, the separated liquid is subjected to biological nitrification / denitrification, and then membrane separation is performed (special feature. (Kaisho No. 61-185400), removal of phosphorus in the dehydration step of night soil wastewater is not considered, and a dephosphorization step is still required after nitrification / denitrification treatment and membrane separation treatment.

In the conventional dehydration process of sewage mainly containing urine, a dehydration method of removing 90% or more of phosphorus has been put to practical use so that the dephosphorization process is not required after biological treatment. What has not been done is that when human waste is the main, the amount of inorganic coagulant required for phosphorus removal is enormous, and because the urine alkalinity is high, the pH due to the addition of inorganic coagulant is high.
This is because there are many problems such as a trouble caused by a sharp decrease in That is, since human waste contains carbonate ions, when an inorganic coagulant (ferric chloride or sulfuric acid band) is added to insolubilize phosphorus, the amount of the inorganic coagulant consumed is large and carbon dioxide gas is generated. Foams become difficult to process.

Regarding the septic tank sludge, an iron-based coagulant is added to separate it into separated water and concentrated sludge in the concentration step,
A method has been proposed in which separated water is biologically treated, and excess sludge generated by biological treatment is mixed with the septic tank sludge to be treated (JP-A-57-105297).

[0011]

In recent years, it is not uncommon for the ratio of septic tank sludge supplied to the mixing treatment of human waste and the like to increase with the ratio of human waste.
Therefore, it is desired to develop a rational mixing treatment system that targets septic tank sludge as a main treatment object, that is, to develop a rational mixing treatment system suitable for treating a mixed liquid containing a large amount of septic tank sludge. In the human waste treatment, which is the main treatment target, the phosphorus in the treated water is 1 m without the dephosphorization step after the biological treatment.
It cannot be removed to a low level of around g / l, and the reality is that a rational mixing treatment system with human waste considering the characteristics of the characteristics 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, etc. are highly removed by a mixing treatment mainly with septic tank sludge and human waste. The purpose is to provide a rational treatment system for obtaining treated water.

[0013]

The method for treating night soil and septic tank sludge of the present invention is a method of dehydrating and separating obtained by mixing septic tank sludge with human waste and then adding an inorganic coagulant and a polymer coagulant for dehydration. A method for biologically nitrifying and denitrifying water, which is characterized in that the amount of septic tank sludge mixed with human waste is at least twice that of human waste.

That is, the present inventors paid attention to the current situation that the amount of septic tank sludge to be carried in is increased and the ratio with human waste is reversed, and living organisms that could not be realized by conventional human waste-based treatment. The present invention has been completed by discovering a new system that makes it possible to omit the dephosphorization step after treatment by treating sludge mainly of septic tanks.

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

[0016]

As described above, since human waste contains carbonate ions, a large amount of inorganic coagulant must be used to add an inorganic coagulant to insolubilize phosphorus, and carbon dioxide gas is generated to foam.
Although it becomes difficult to perform dehydration treatment, in accordance with the present invention, by mixing septic tank sludge more than twice as much as human waste, it becomes possible to insolubilize phosphorus by an inorganic coagulant, and 90% of phosphorus contained by dehydration treatment can be obtained. The above can be insolubilized and removed.

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

Further, the effects of improving the dehydration efficiency and reducing the load on the biological treatment or the subsequent steps thereafter can be obtained, and the low water content dehydrated cake and the high quality treated water can be efficiently obtained.

[0019]

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

FIG. 1 is a system diagram showing an embodiment of a method for treating night soil and septic tank sludge of the present invention. In FIG. 1, 1 and 2 are a receiving tank, 3 is a pretreatment step, 4, 5 and 10 are storage tanks, 6 is a reaction tank, 7 is a granulation concentration tank, 8 is an incineration step,
9 is a dehydrator, 11 is a biological reaction tank (biological nitrification / denitrification process), 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 pipes. Reference numerals 26 and 35 denote conveyors.

In the method shown in the figure, an inorganic coagulant and an amphoteric polymer are added to a mixed solution in which the ratio of human waste septic tank sludge to urine is 2: 1 or more, and an inorganic coagulant is added to perform dehydration treatment. The filtrate is subjected to biological nitrification / denitrification treatment in a biological reaction tank, the treated liquid is separated into a permeated liquid and a concentrated liquid by a membrane separator, and a part of the concentrated liquid is returned to the biological reaction tank and the permeated liquid is also returned. Is treated with activated carbon.

The human waste is passed through the pipe 21, the receiving tank 1 and the pipe 23 to remove impurities in the pretreatment step 3, and then stored through the pipe 25 in the storage tank 4. The human waste septic tank sludge is passed through the pipe 22, the receiving tank 2 and the pipe 24 to be subjected to the pretreatment process 3
After the contaminants are removed in (1), it is stored in the storage tank 5 via the pipe 27. The human waste in the storage tank 4 is introduced into the storage tank 5 through a pipe 28 at a predetermined ratio and mixed. Note that the contaminants (stain residues) removed in the pretreatment step 3 are sent from the conveyor 26 to the incineration step 8.

A mixed liquid in which human waste and urine septic tank sludge are mixed at a predetermined ratio in the storage tank 5 (in this embodiment, further,
Excess sludge in the biological reaction tank 11, which will be described later, is mixed. ) Is
It is introduced into the reaction tank 6 through the pipe 29 and modified by adding an inorganic coagulant from the pipe 30 to insolubilize phosphorus, high molecular weight organic matter and the like contained in the septic tank sludge and night soil. Here, the inorganic coagulant is preferably added so that 90% or more of phosphorus in the mixed solution is insolubilized. The insolubilization treatment liquid in the reaction tank 6 is introduced into the granulation concentration tank 7 through the pipe 31, and the amphoteric polymer is added through the pipe 32 to perform the granulation concentration treatment to form a strong floc. The flocculated or granulated liquid is introduced to the dehydrator 9 through the pipe 33 and dehydrated.
In this dehydration treatment, strong flocs are formed in the liquid to be dehydrated, and since a large amount of fiber is contained in septic tank sludge and human waste, it is possible to obtain a dehydrated cake with a low water content. You can

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

The dehydrated 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 through the pipe 34, the storage tank 10 and the pipe 36. To be done.

In this biological reaction tank 11, not only BOD in the separated liquid or filtrate but also nitrogen is removed by biological nitrification / denitrification treatment.

In this biological nitrification / denitrification treatment, most of the organic substances in the urine as septic tank sludge are removed in the preceding dehydration step, and the properties of the liquid introduced into the biological reaction tank are as follows. Since it has the same properties as the diluted one, the load of biological treatment is lightened, and the reaction tank capacity and the required oxygen amount can be small. In particular, the capacity of the nitrification tank is determined not only as the nitrogen load but also as the capacity that can secure the required amount of sludge.
If the inflow of the SS substance is small, the amount of excess sludge drawn out can be small, so that the amount of sludge can be easily secured and stable nitrification can be performed.

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

The biologically treated water containing microorganisms obtained in the biological reaction tank 11 is then fed from the pipe 38 to the membrane separation device 12 for membrane separation treatment to separate it into a permeate and a concentrate. The concentrated liquid is used to maintain the sludge concentration in the biological reaction tank 11.
Biological reaction tank 11 from pipe 40
Return to. By adopting this membrane separation treatment, a high concentration of activated sludge is maintained in the biological reaction tank 11, so that stable nitrification / 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 highly removed. In addition, the separation liquid or filtrate obtained by dehydrating the septic tank sludge and human urine to remove the SS or colloidal organic matter is subjected to the biological treatment, so that the biological treatment of the septic tank sludge and the human urine is directly subjected to the membrane separation. The COD and chromaticity of the membrane permeate will be lower than when treated,
The load on the activated carbon treatment tank in the latter stage is significantly reduced.

Since the membrane permeate obtained by this membrane separation treatment is still colored and the COD is not at a satisfactory level in many cases, the activated carbon treatment device 13 is then fed from the pipe 39.
The residual chromaticity and COD are removed by passing through to the water, and colorless and transparent final treated water is obtained and discharged from the pipe 41. In this activated carbon treatment, since the membrane permeate does not contain SS, there is no concern 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 at least twice as much as that of human waste, but there is no particular upper limit to the ratio of septic tank sludge.

Further, in the present invention, septic tank sludge may be mixed with urine and the like, if necessary, and excess sludge discharged from the biological nitrification / denitrification treatment step may be mixed. Has a property closer to that of septic tank sludge, so that if the combined amount of septic tank sludge and excess sludge is at least twice as much as that of human waste, a rational mixing process with human waste can be performed.

When the excess sludge is mixed, the high molecular weight organic matter in the excess sludge can be simultaneously flocculated in the dehydration step, so that the high molecular weight organic matter accumulated in the biological treatment system by the membrane separation treatment can be taken out of the system. It is possible and extremely 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. As the inorganic coagulant, ferric chloride, Polyiron sulfate or the like can be used, and the addition amount of such an inorganic coagulant is 90% of that of phosphorus in the mixed solution.
It is preferable that the amount be insolubilized to be at least%.

The amount of the inorganic coagulant added is required to be an amount sufficient for the metal such as iron to react with the phosphorus in the septic tank sludge and the urine to produce iron phosphate, etc. It is necessary to use iron in a molar ratio of 1.0 to 1.5 or more with respect to phosphorus.

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, for example, vinyl group-containing amides such as acrylamide, methacrylamide, dimethylacrylamide, dimethylmethacrylamide, acrylonitrile, 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 addition amount of such an amphoteric polymer is appropriately determined according to the properties of the mixed solution and the like, but in the usual case, it is about 0.5 to 2.0% by weight based on the solid matter.

In the present invention, it is most preferable to use the above-mentioned amphoteric polymer as the polymer flocculant, and the use of the amphoteric polymer enables efficient granulation and concentration in the granulation concentrating tank. In addition, although the advantage that the dehydrating ability of the dehydrator can be brought out greatly,
The polymer flocculant is not limited to the amphoteric polymer, and other types of polymers such as a cationic polymer can also be used.

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

The present invention will be described in more detail below with reference to specific examples and comparative examples.

Example 1 Processing was carried out according to the method of the present invention shown in FIG. SS: 10500mg by mixing septic tank sludge, night soil and excess sludge from post-process nitrification / denitrification at a ratio of 2: 1: 1
/ L, BOD: 3700 mg / l, COD: 3700 m
g / l, T-N: 810 mg / l, PO ₄ -P: 140
A mg / l mixture was obtained.

Ferric chloride (38% aqueous solution) was added to this mixed solution.
Was added at 3000 mg / l and amphoteric polymer at 130 mg / l to prepare and granulate, and dehydrated with a belt press dehydrator to obtain a dehydrated cake having a water content of 73.2% and a low water content. A copolymer of dimethylaminoethyl acrylate, acrylamide and acrylic acid was used as the amphoteric polymer.

Here, the iron in ferric chloride 3000 mg / l was 1.55 in molar ratio to PO ₄ -P in the mixed solution.
PO ₄ -P in dehydrated filtrate (excluding wash water)
Was as low as 3.3 mg / l. Also, SS is 13
0 mg / l, BOD 1480 mg / l, COD 10
20 mg / l and T-N became 615 mg / l.

Biological nitrification using this dehydrated filtrate as raw water
When denitrification was performed and the treated liquid was subjected to solid-liquid separation by an ultrafiltration membrane, the properties of the obtained permeated water were 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
l, T-N: 8.5mg / l, PO 4 -P: 0.4mg
It was possible to obtain the final treated water of high water quality of 1 / l, chromaticity: 30 degrees.

From these results, according to the method of the present invention, BOD, COD,
It is clear that it is possible to obtain treated water with a high degree of removal of nitrogen, phosphorus and chromaticity.

Comparative Example 1 The mixing ratio of septic tank sludge, human waste, and excess sludge of nitrification / denitrification treatment was set to 1: 2: 1, and the ratio of human waste was increased to SS: 11.
800 mg / l, BOD: 7900 mg / l, COD:
4800 mg / l, TN: 2150 mg / l, PO ₄
-P: A mixed solution of 270 mg / l was obtained, and this mixed solution was treated in the same manner as in Example 1.

As a result, ferric chloride (38% aqueous solution) 6000 mg / l and amphoteric polymer 280 mg / l were required for the conditioning of the mixed solution, about twice as much as in Example 1, and In the process of injecting and mixing ferric chloride, foaming was severe, and air bubbles adhered to the sludge to impair the dehydration property.

From these results, it is understood that it is difficult to remove phosphorus by about 90% by dehydration with the inorganic coagulant and the polymer when the main component is human waste.

Comparative Example 2 In Example 1, the addition of the inorganic coagulant and the amphoteric polymer was not performed, and the septic tank sludge, night soil and excess sludge were mixed at 2: 1:
The mixed solution obtained by mixing at a ratio of 1 was subjected to nitrification / 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 dephosphorization equipment was required. COD is 105 mg /
l, the chromaticity is 440 degrees, which is about twice the concentration in the case of Example 1, and the burden on activated carbon treatment is large. Therefore, if economic considerations are taken into account, a coagulation separation facility that also serves the purpose of dephosphorization is indispensable. It was confirmed that there is.

[0055]

As described in detail above, according to the method for treating human waste and septic tank sludge of the present invention, an inorganic coagulant and a polymer coagulant are added to a mixed liquid of human waste and septic tank sludge for dehydration. As a result, without using a large amount of coagulant,
It becomes possible to highly remove phosphorus without causing dehydration inhibition such as foaming. Therefore, the treated water from which phosphorus is highly removed can be obtained without providing a coagulation separation step after biological treatment. Even if there is no coagulation separation step after the biological treatment, the load of the subsequent activated carbon treatment does not become excessive, and the final treated water from which COD and chromaticity are highly removed can be obtained. Since the coagulation liquid used for dehydration has excellent dehydration properties, it is possible to make the dehydrator exhibit high sludge treatment capacity and obtain a dehydrated cake with a low water content. Since the load of biological denitrification is reduced, treated water from which nitrogen is highly removed can be obtained even if the reactor capacity and the required oxygen amount are reduced. The effects 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 drawings]

FIG. 1 is a system diagram showing an example method of a method for treating night soil and septic tank sludge of the present invention.

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

[Explanation of symbols]

 1, 2 Receiving tank 3 Pretreatment process 4, 5, 10 Storage tank 6 Reaction tank 7 Granulation concentration tank 8 Incineration process 9 Dehydrator 11 Biological reaction tank 12 Membrane separation device 13 Activated carbon treatment device

Claims (1)

[Claims] 1. A method of mixing human waste with septic tank sludge, adding an inorganic coagulant and a polymer coagulant to dehydrate, and subjecting the dehydrated separated water obtained to biological nitrification / denitrification treatment, A method for treating human waste and septic tank sludge, characterized in that the amount of the septic tank sludge to be mixed with human excrement is at least twice that of the human sewage.