JP3400292B2 - Waste treatment method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste treatment method for treating liquid organic wastewater and solid organic waste that can utilize the energy generated during methane fermentation treatment.

[0002]

Conventionally, human waste sewage such as human sewage and septic tank sludge, liquid organic sewage such as livestock excrement, agricultural and marine products and food processing wastewater are subjected to biological nitrification denitrification treatment, and sludge is separated into solid and liquid. Methane gas generated by methane fermentation treatment by anaerobic methane fermentation treatment with solid waste containing organic waste such as kitchen garbage and kitchen waste and biological nitrification denitrification treatment of liquid content with organic wastewater There is known a waste treatment method in which liquefied organic sewage and wastes are comprehensively treated by using waste water for processing energy by using it for power generation and by utilizing waste heat to progress methane fermentation.

By the way, solid waste such as raw garbage is mainly composed of carbohydrates that are easily decomposed by methane fermentation, but the carbon / nitrogen ratio is 30 and the optimum ratio for methane fermentation treatment is 20. Compared with nitrogen content. On the other hand, the sludge after biological nitrification and denitrification treatment of liquid organic wastewater such as human waste water has a high carbon / nitrogen ratio of 5 and nitrogen, and also contains a large amount of protein and fat, so it is a solid waste. As a result, methane fermentation treatment cannot be performed well. Therefore, the conventional waste treatment method described above combines the sludge after the biological nitrification denitrification treatment and the solid waste in advance before the methane fermentation treatment to obtain a good carbon / nitrogen ratio of carbohydrates, proteins and fats. The efficiency of the methane fermentation process is being improved with a good ratio of minutes.

[0004]

However, liquid organic sewage such as human waste sewage generally contains a large amount of nitrogen compounds and phosphorus compounds, and also contains a large amount of organic substances due to COD and BOD. In the waste treatment method of No. 2, the separated water obtained by separating the sludge after the biological nitrification denitrification treatment cannot be treated by the biological nitrification denitrification treatment, and COD
Since pollutants such as hardly decomposable soluble organic substances and phosphorus compounds remain due to nitrogen, it is possible to perform nitrogen treatment by advanced treatment such as coagulation treatment with a coagulant, membrane separation, or adsorption treatment with activated carbon. It is necessary to remove the compound, the phosphorus compound, and the organic substances caused by COD and BOD.

In the case of membrane separation or adsorption treatment with activated carbon, many pollutants remain, so that the processing load becomes large and maintenance of activated carbon and membrane becomes complicated.

On the other hand, for example, JP-A-59-49896, JP-A-56-129084, and JP-A-57-1.
As described in Japanese Patent No. 0393, a biological nitrification denitrification treatment is performed after generating and separating magnesium ammonium phosphate (Mg (NH ₄ ) PO ₄ ) as a fertilizing component that becomes a fertilizer by using a magnesium compound as a coagulant. It is known that the sludge is coagulated and separated by a coagulant, adsorbed by activated carbon, or separated by a membrane. Furthermore, Japanese Patent Laid-Open No. 2-1
As described in Japanese Patent No. 27000, magnesium compound is added to magnesium ammonium phosphate (Mg (NH
₄ ) A structure is known in which ferric chloride is added and coagulation is performed after PO ₄ ) is produced and separated.

However, these JP-A-59-498
96, JP-A-56-129084, JP-A-57-10393 and JP-A-2-127000.
In the conventional structure described in Japanese Patent Publication No. 2003-242242, the reduction of phosphorus compounds can be achieved, but hardly decomposed and soluble organic substances that cannot be completely treated by biological nitrification / denitrification treatment cannot be sufficiently aggregated and separated by a magnesium-based flocculant, The load of activated carbon treatment and membrane separation treatment in the latter stage becomes large, and maintenance of activated carbon and membrane becomes complicated. In addition, since nitrogen compounds can be reduced to an extremely low value by biological nitrification denitrification treatment, magnesium ammonium phosphate (Mg (N
The amount of H ₄ ) PO ₄ ) produced is low, and the phosphorus compound cannot be removed sufficiently. For this reason, in practice, Japanese Patent Laid-Open No. 2-1270
As described in JP-A-00-00, phosphorus compounds and hardly decomposed and soluble organic substances are removed by agglomeration by addition of ferric chloride in the latter stage, or activated carbon or a membrane is used for treatment, which is efficient and inexpensive at a high treatment cost. Difficult to process. Furthermore, C
Part of the coagulated sludge in which phosphorus is coagulated with ferric chloride, which is generally used for coagulation treatment of phosphorus compounds together with hardly decomposable soluble organic substances caused by OD, is returned to the biological nitrification denitrification reaction tank. In this case, the iron phosphate aggregated by the anaerobic atmosphere during the denitrification treatment is reduced and phosphorus is eluted again, so that phosphorus may be concentrated in the treatment system.

On the other hand, as a conventional waste treatment apparatus for treating solid organic wastes such as raw garbage, agricultural and marine wastes, sludge, etc., as disclosed in Japanese Patent Application Laid-Open No. 6-71297, for example, Since it contains contaminants such as resin films, plastics, and Styrofoam that are extremely difficult to decompose in organisms, the contaminants are removed in advance after crushing such as bag breaking and debagging, and methane fermentation treatment is performed to remove magnesium compounds, ammonium compounds and Magnesium ammonium phosphate (Mg (NH ₄ ) P
It is known that O ₄ ) is generated and separated to reduce the amount of phosphoric acid compounds and nitrogen compounds.

However, magnesium compounds, ammonium compounds, phosphoric acid compounds, etc. are originally components to be removed, and when the composition of the organic waste fluctuates, the addition amounts thereof fluctuate, and conversely, the magnesium content and ammonium content are changed. However, since the phosphorus content may increase, the control of the addition amount becomes complicated. In addition, contaminants that are removed by disintegration have organic substances that can be decomposed by microorganisms attached to them, which causes a bad odor when treating contaminants and is unsanitary. To do.

As described above, in the conventional treatment of liquid human waste-based sewage, the load such as coagulation treatment, activated carbon treatment, and membrane treatment for highly treating organic substances and phosphorus compounds that cannot be completely treated by biological treatment. Is difficult to reduce, and it is difficult to efficiently, inexpensively and easily perform advanced purification treatment. Further, in the conventional treatment of solid organic waste, it is difficult to highly remove both nitrogen compounds and phosphorus compounds, and it is difficult to efficiently and inexpensively and easily perform advanced purification treatment.

In view of the above problems, it is an object of the present invention to provide a waste treatment method capable of treating organic wastewater and organic waste efficiently and easily.

[0012]

The method for treating waste according to claim 1 is characterized in that, after biologically nitrifying and denitrifying a liquid organic wastewater, it is subjected to solid-liquid separation into sludge and treated water and biodegradation. Waste treatment method of solid-liquid separation of a fermented product obtained by methane fermentation treatment of possible solid organic waste and the sludge, and biological nitrification denitrification treatment of separated water together with organic wastewater In, a magnesium compound is added to the fermented product at a molar ratio of magnesium of 1 or less with respect to a total phosphorus content in the fermented product, and the fermented product to which the magnesium compound is added is solidified. Liquid separation. Then, after the biological organic nitrification denitrification treatment of the liquid organic wastewater, while performing solid-liquid separation into sludge and treated water, biodegradable solid organic waste and sludge are subjected to methane fermentation treatment. A magnesium compound was added to the obtained fermented product such that the molar ratio of magnesium was 1 or less with respect to the total phosphorus content in the fermented product, and the fermented product to which the magnesium compound was added was added. Solid-liquid separation is performed, and the resulting separated water is subjected to biological nitrification denitrification treatment together with organic sewage, so the addition of a magnesium compound produces a sparingly soluble magnesium ammonium phosphate and solid-liquid separation removal is performed. Remains in the fermented product, prevents scale formation due to precipitation of magnesium compounds in the subsequent step, and enables stable treatment for a long period of time.
If the molar ratio of magnesium exceeds 1, magnesium ions will remain in the fermented product and scale will be generated by the precipitation of magnesium compound in a later step, resulting in clogging at each site in the treatment system and maintenance. Since the management becomes complicated, the magnesium compound is added so that the molar ratio of magnesium is 1 or less with respect to the total phosphorus content in the fermented product.

According to the waste treatment method of the second aspect, in the waste treatment method of the first aspect, when the magnesium compound is added, the pH is controlled to an alkaline side of 7.5 or more. And, when the magnesium compound is added, in order to control the pH to the alkaline side of 7.5 or more,
By adding the magnesium compound, the sparingly soluble magnesium ammonium phosphate is efficiently deposited and formed, and the phosphorus compound is efficiently removed. It should be noted that in an atmosphere where the pH is more acidic than 7.5, the solubility product of magnesium ammonium phosphate increases, and magnesium ammonium phosphate is not efficiently precipitated and formed. Therefore, the pH is controlled to an alkaline side of 7.5 or higher.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The configuration of an embodiment of the waste treatment method of the present invention will be described below with reference to FIG.

In FIG. 1, reference numeral 1 is a first residue removing means, and this first residue removing means 1 is constructed by combining screens and screw presses having a mesh size of about 1 mm in multiple stages. , To remove impurities mixed in human waste, which is organic wastewater. Further, 2 is a second residue removal means, and this second residue removal means 2 is configured similarly to the first residue removal means 1 and is mixed in the septic tank sludge which is organic wastewater. Remove residue and contaminants. The removed residue and foreign substances are molded into pellets and processed into solid fuel, building materials, etc., or incinerated.

The second residue residue removing means 2 is connected to the residue residue separating means 3. The residue separation means 3 is
The septic tank sewage, from which the scum residue and impurities have been removed from the septic tank sludge by the second scum residue removing means 2, can flow in.

Further, the first waste residue removing means 1 is connected to a biological treatment means 4 for performing a biological purification treatment of the waste sewage obtained by removing impurities from the waste sewage by a biological nitrification denitrification reaction. The biological treatment means 4 is aerobic because it has a structure for producing a nitrification / denitrification reaction in one tank, a tank for denitrification treatment and a tank for nitrification treatment, and an aeration means. A configuration in which a tank for treating aerobic microorganisms with microorganisms is added may be used.

The biological treatment means 4 is connected to a first solid-liquid separation means 5 for solid-liquid separating the biological treatment liquid after the biological nitrification / denitrification treatment. The first solid-liquid separation means 5 is a first sludge separation means 6 for separating surplus sludge from the biological treatment liquid by filtration separation using a screen or a membrane or sedimentation separation treatment, and the first sludge separation means. First aggregation means 7 for adding an inorganic flocculant such as ferric chloride to the separated water separated in 6 to perform the aggregation treatment, and an aggregation treatment liquid obtained by the aggregation treatment in the first aggregation means 7. Is connected in series with the second sludge separation means 8 for separating the coagulated sludge by filtration separation using a screen or a membrane, sedimentation separation processing, or the like.

A sludge returning means 9 for returning the separated sludge to the residue separation means 3 is connected to the first solid-liquid separation means 5, and the sludge return means 3 is connected to the sludge residue separation means 3 through the sludge return means 9. The returned sludge, that is, the excess sludge separated by the first sludge separating means 6 and the coagulated sludge separated by the second sludge separating means 8 are combined with the septic tank wastewater by the scum residue separating means 3.
Then, in the residue residue separating means 3, the second residue residue removing means 2 separates the residue and impurities remaining without being separated and removed into sludge and stock solution, and the stock solution is passed to the biological treatment means 4. The undiluted solution is biologically nitrified and denitrified along with the human waste sewage from which contaminants have been removed by the biological treatment means 4.

On the other hand, 11 is a waste pretreatment means, and this waste pretreatment means 11 is a crushing bag for disintegrating waste including biodegradable organic waste such as raw waste and agricultural and marine waste. It is composed of a crushing device for crushing, and a metal removing device for magnetically sorting while washing the crushed material in which waste is crushed by this crushing device.

Further, the dust pretreatment means 11 includes a mixing means 12
Are connected. The mixing means 12 is connected to a residue transfer means 13 for transferring the residue, the contaminants and the sludge separated by the residue separation means 3 and feeding them into the mixing means 12. Then, the mixing means 12 appropriately adds, for example, about 55 while adding water to the residue and the contaminants transported by the residue transporting means 13 and the crushed waste from the pretreatment means.
A mixture is prepared by warming to ℃ and mixing with stirring. Note that steam may be used for adding water and heating.
By using steam, it is not necessary to add water and separately heat it by a heating means, and heating and stirring and mixing can be efficiently performed.

The mixing means 12 is connected to a methane fermentation means 14 for methane fermenting the prepared mixture. The methane fermentation means 14 appropriately stirs at a temperature of, for example, 55 ° C. to methane-ferment an organic substance with methane bacteria or the like. The methane fermentation means 14 is provided with a methane gas recovery means (not shown) for recovering the generated methane gas. The recovered methane gas is used for power generation and the like, and is used as operating energy when treating organic wastewater for human waste and organic waste.

A reaction processing means 15 is connected to the methane fermentation means 14. The reaction treatment means 15 is a reaction tank 16 into which a fermentation treatment product obtained by subjecting the mixture to a methane fermentation treatment flows, a pH measurement means 17 for measuring the pH of the fermentation treatment product, and a measurement result of the pH measurement means 17. PH adjusting means 19 equipped with a pH control device 18 for appropriately adjusting the pH to a predetermined pH by appropriately adding a pH adjusting agent such as alkali, and Mg for appropriately adding a reaction agent of a magnesium compound such as magnesium chloride to the fermented product. And adding means 20. Then, the pH adjusting means 19 adjusts the pH of the fermented product to an atmosphere on the alkaline side of 7.5 or more, preferably on the alkaline side of 8.0 or more. Also, means for adding Mg
For No. 20, a magnesium compound is added so that the molar ratio of magnesium is 1 or less with respect to the total phosphorus content in the fermented product.

Further, in the reaction treatment means 15, the fermented product to which the magnesium compound is added is subjected to solid-liquid separation by various solid-liquid separation methods such as filtration separation using a screen or a membrane, sedimentation separation treatment and centrifugal separation treatment. Second solid-liquid separation means
21 is connected. And this second solid-liquid separation means
The filtrate separated in 21 is returned to the residue separating means 3 in the filtrate returning means 22, and the solid content is formed into pellets and processed into solid fuel, building material, or the like, or incinerated.

Next, the operation of the above embodiment will be described.

First, the human waste is made to flow into the first raw material removing means 1 to be separated into a solid waste material and a liquid raw wastewater, and the raw wastewater is made to flow into the biological treatment means 4.

On the other hand, the septic tank sludge is removed by the second scum residue removing means 2
To separate into a solid residue and a liquid septic tank wastewater, and the septic tank wastewater is allowed to flow into the residue separation means 3. Then, the undiluted solution that has been subjected to solid-liquid separation by the waste residue separating means 3 is allowed to flow into the biological treatment means 4, and the undiluted solution is subjected to biological nitrification denitrification treatment together with the excrement sewage in the biological sewage wastewater and the undiluted solution. A part of the organic substances, nitrogen compounds, and phosphorus compounds that contribute to the mixed BOD are treated.

Thereafter, the biological treatment liquid after the biological nitrification and denitrification treatment is made to flow into the first sludge separation means 6 which constitutes the first solid-liquid separation means 5, and is filtered and separated by a screen or a membrane. Separating into excess sludge and separated water by sedimentation separation treatment. Then, the excess sludge is returned to the scum residue separating means 3,
The separated water flows into the first flocculating means 7 of the first solid-liquid separating means 5.

Next, the separated water that has flowed into the first flocculating means 7 is added with an inorganic flocculant such as ferric chloride, and other organic substances and nitrogen compounds that contribute to the remaining BOD in the separated water are added. The organic substances and phosphorus compounds that contribute to COD are coagulated. After this, the coagulation treatment liquid subjected to the coagulation treatment is the first
Flow into the second sludge separation means 8 of the solid-liquid separation means 5 of
Solid-liquid separation is performed into coagulated sludge and treated water by various solid-liquid separation methods such as filtration separation using a screen or a membrane and sedimentation separation treatment. Then, the coagulated sludge is returned to the scum residue separating means 3, and the treated water is discharged out of the system. By returning the coagulated sludge to the residue separation means 3, further coagulation occurs due to the coagulation action of the remaining inorganic coagulant.

On the other hand, solid waste containing biodegradable organic waste such as raw garbage, agricultural and marine waste, sludge, etc. is thrown into the shredder of the waste pretreatment means 11 to disintegrate and disintegrate The crushed crushed material is cleaned by a metal removing device and magnetically separated to remove the metal.

Then, the crushed material of the crushed waste after the magnetic selection is put into the mixing means 12, and the residue transfer means is also used.
The residue, contaminants and sludge separated by the residue separation means 3 are introduced via 13. Then, for example, the mixture is prepared by stirring and mixing the crushed material of the waste, the residue, the impurities and the sludge while heating to about 55 ° C. using steam. By stirring and mixing the crushed material of this waste with the residue, contaminants and sludge, the viscosity of organic residues adhering to the residue, contaminants and sludge decreases, and it is solubilized in the warm water generated by condensation of steam. . After that, the mixture prepared by stirring and mixing for a predetermined time is allowed to flow into the methane fermentation means 14, and is appropriately stirred, for example, at 55 ° C. to subject the organic substance to methane fermentation treatment with methane bacteria or the like. The methane gas generated by the methane fermentation process is recovered by the methane gas recovery means, used for power generation, etc., and used as the operating energy for the treatment of human waste sewage and organic waste.

Next, the fermentation treatment product obtained by subjecting the mixture to methane fermentation treatment by the methane fermentation means 14 is used as the reaction tank 16 of the reaction treatment means 15.
Flow into. Then, the Mg addition means 20 appropriately adds a reactive agent of a magnesium compound such as magnesium chloride to the fermented product, for example, so that magnesium is 1 mol or less with respect to the total amount of phosphorus in the fermented product. further,
The pH of the fermented product is measured by the pH measuring means 17 of the pH adjusting means 19.
PH control device 18 of pH adjusting means 19
At this time, a pH adjuster such as sodium hydroxide is appropriately added to obtain a predetermined pH, for example, 7.5 or more, preferably 8.0.
Adjust to the above alkaline atmosphere. By adding this magnesium compound, it reacts with ammonium ions, which are nitrogen compounds, and phosphate ions, which are phosphorus compounds, in the fermented product, so that magnesium ammonium phosphate (Mg (NH
₄ ) Generate PO ₄ ).

Thereafter, the second solid-liquid separation means 21 is used to apply the fermentation treatment product to which the magnesium compound has been added to various solid-liquid separation methods such as filtration separation using a screen or a membrane, sedimentation separation treatment, and centrifugal separation treatment. Solid-liquid separation into a filtrate and a solid content. Then, the filtrate is returned to the scum residue separating means 3 by the filtrate returning means 22 and merged with the septic tank wastewater and the excess sludge and coagulated sludge separated by the first sludge separating means 6 and the second sludge separating means 8. , Solid content is molded into pellets and made into solid fuel or RDF treatment for building materials,
Incinerate. In addition, as described above, the coagulated sludge separated by the second sludge separating means 8 has the coagulating action of the inorganic coagulant added by the first coagulating means, and therefore the coagulating treatment is performed again to perform solid-liquid separation. The treated, undiluted solution flows into the biological treatment means 4 and is subjected to biological nitrification and denitrification treatment, and the solid matters of the residue, the contaminants and the sludge are returned to the mixing means 12.

By the way, when treating human waste sewage, which is liquid organic sewage, and solid waste such as organic waste and sludge separately, magnesium compounds are added and phosphorus is added in each treatment step. Since it becomes impossible to remove the hardly-decomposable soluble organic matter caused by COD, which is often found in human waste sewage, it is difficult to decompose it by adding an inorganic coagulant such as ferric chloride during the treatment of human sewage. It is necessary to remove phosphorus along with soluble organics. However, the sludge obtained by flocculating with ferric chloride does not contain ammonium or magnesium as a fertilizing component that is a component that serves as a fertilizer for plants. Therefore, as in the above-described embodiment, phosphorus, which is particularly often found in the waste mixed with ammonium together with the once separated residue and contaminants, is added as a magnesium compound to obtain a fertilizing effect as magnesium ammonium phosphate. It can be collected as sludge containing components and can be processed efficiently.

Further, in the above-mentioned embodiment, in order to comprehensively treat the liquid human waste sewage and the solid waste, the filtrate obtained by the solid-liquid separation is circulated after the methane fermentation treatment. And, although magnesium ammonium phosphate is hardly soluble, it shows a solubility of about 520 ml / liter, and the concentration of each ion is Mg = 51.5 mg / liter, PO ₄ −
P = 65.7 mg / liter, NH ₄ —N = 29.7 mg /
Since it becomes 1 liter, magnesium ammonium phosphate dissolved in the circulating filtrate becomes supersaturated. In addition, since the salt of each ion tends to increase in solubility as the ionic strength of the coexisting salt increases, the salt concentration is high and the waste is treated during the treatment of liquid human waste-based wastewater and the treatment of solid waste. Since the total solids (TS) concentration is about 10%, Mg,
The solubilities of the salts of PO ₄ and NH ₄ ions also appear to be considerably higher.

Therefore, in order to reduce the solubility of magnesium ammonium phosphate, the other ion concentration is increased to M
It is necessary to reduce the ion concentration of the salts of g, PO ₄ and NH ₄ ions. Since the concentration of phosphate ions is not constant in human wastewater and wastes, in order to stabilize the phosphate ion concentration at a low concentration, it is necessary to add more than the molar equivalent amount to the maximum phosphate concentration in the fermented product to which the magnesium compound is added. The magnesium compound is added so that the amount of magnesium becomes, and magnesium ions will remain in the filtrate that has been solid-liquid separated by the second solid-liquid separation means 21.

However, in the above-described embodiment in which the filtrate is returned and merged with the human waste sewage to perform the biological nitrification / denitrification treatment, when magnesium ions remain in the filtrate, phosphate ions and ammonium ions in the human waste sewage are generated. ,
There is a problem in that it reacts with magnesium ammonium phosphate and is immediately supersaturated, and is produced as scale in biological treatment means and piping in the subsequent stage.

Therefore, in the above embodiment, when the magnesium compound is added, the molar ratio of magnesium to the total amount of phosphorus is set to 1 mol or less, so that magnesium ions do not remain in the filtrate, and Prevents the generation of scale after the treatment and enables stable treatment. Phosphorus in the waste can be recovered as magnesium ammonium phosphate, a fertilizing component that is almost valuable, and phosphate ions that cannot be removed are removed after biological treatment. Since it is removed with the inorganic coagulant together with the hardly decomposable soluble organic matter, the treatment can be performed efficiently.

[0039] Waste such as food waste is mainly composed of carbohydrates that are easily decomposed by methane fermentation, but carbon /
Compared to the nitrogen ratio of 30 and the optimum ratio of methane fermentation treatment of 20, the nitrogen content is low. On the other hand, sludge after biological treatment of human waste water has a high carbon / nitrogen ratio of 5 and nitrogen, and also contains a lot of proteins and fats. Therefore, methane fermentation treatment as solid waste results in good digestion. Can not. However,
In the above embodiment, waste such as raw garbage is mixed with sludge to obtain a good carbon / nitrogen ratio, and the ratios of carbohydrates, proteins and fats are also improved, and the methane fermentation process proceeds efficiently. it can.

As described above, according to the above-mentioned embodiment, the first residue residue removing means 1 and the second residue residue removing means 2 are used.
The human wastewater and the septic tank wastewater from which the wastes and contaminants have been separated by the biological treatment means 4 are biologically nitrified and denitrified by the biological treatment means 4.
Solid-liquid separation by means of solid-liquid separation means 5 and waste containing the separated residue, contaminants and sludge and biodegradable organic waste, and methane fermentation processing by methane fermentation means 14, A magnesium compound is added to the fermented product thus obtained by the reaction treatment means 15 to generate magnesium ammonium phosphate having a low solubility, and the solid-liquid separation is performed by the second solid-liquid separation means 21 so that it is separated from human waste water. Organic substances adhering to the residue and contaminants are digested by methane fermentation treatment with organic waste, and the residue is not discharged outside the system with the organic substances adhering. Since magnesium ammonium phosphate of is produced and solid-liquid separated and removed, phosphorus compounds and organic substances can be easily and efficiently treated without deteriorating the surrounding environment.
By effectively utilizing the methane gas produced by methane fermentation,
The processing cost can be reduced.

Further, since the filtrate solid-liquid separated by the second solid-liquid separation means 21 is returned to the biological treatment means by the filtrate returning means 22, organic matter and phosphate ions in the untreated filtrate by methane fermentation are Contaminants such as ammonium ions can be biologically processed by utilizing the energy obtained by methane fermentation and highly purified by the first solid-liquid separation means 5 in the subsequent stage,
It can treat human waste sewage and waste efficiently and highly.

Further, since the magnesium compound is added in the reaction treatment means 15 so that the molar ratio of magnesium is 1 or less with respect to the total phosphorus content in the fermented product, magnesium ions are added to the fermented product. Remains inside,
In a subsequent step, scale formation due to precipitation of magnesium compounds such as magnesium ammonium phosphate can be prevented, and stable and efficient treatment can be achieved for a long period of time.

When the waste is treated, the methane fermentation treatment is not performed directly, but the waste pretreatment means 11 is first crushed and crushed and then mixed by the mixing means 12 to perform the methane fermentation treatment. Even if contaminants that are difficult to biodegrade are mixed in, by crushing the contaminants together with the organic waste to obtain a substantially uniform composition, solubilization of contaminants such as organic substances and methane in the subsequent mixing can be achieved. Fermentation processing can proceed efficiently.

Then, since the coagulated sludge from the second sludge separation means 8 is also merged in the residue residue separation means 3 for solid-liquid separation, the action of the added inorganic coagulant can be fully utilized and treated efficiently. it can.

In the above embodiment, the mixing means
Before subjecting the mixture prepared in 12 to methane fermentation treatment in the methane fermentation means 14, contaminants such as synthetic resin film, plastic, styrofoam, and glass, which are extremely difficult to biodegrade, may be separated and removed while washing. Then, the removed contaminants are separately molded into pellets and processed into solid fuel, a building material, or the like, or incinerated. According to this configuration, a substance that cannot be digested by the organism is not mixed during the methane fermentation treatment, and the methane fermentation treatment can be efficiently performed.

Separately, human waste and septic tank sludge are separated into the first
Although the explanation has been made by removing the scum residue and the contaminants by the scum residue removing means 1 and the second scum residue removing means 2, respectively, it is possible to confirm the state of the human waste system wastewater in which the human waste, the septic tank sludge and the liquid waste are mixed in advance. In some cases, after the residue is separated, the residue is separated by various solid-liquid separation methods such as filtration separation by a membrane, sedimentation separation, centrifugal separation, coagulation separation, etc. The biological treatment may be performed, and the solid content may be added to the mixing means 12 to be treated. Further, the sewage system wastewater may be directly subjected to solid-liquid separation by the sewage residue separation means 3 without separating the sewage residue. According to these configurations, the configuration is simplified and the device can be downsized.

The explanation has been made by returning the filtrate separated by the second solid-liquid separating means 21 to the waste residue separating means 3 by the filtrate returning means 22. The separated filtrate is treated separately from the human waste system wastewater. May be. In this case, the magnesium compound may be added in an amount of more than 1 mol of magnesium with respect to the total amount of phosphorus.

Although the mixing means 12 is provided and premixed before the methane fermentation treatment, the methane fermentation treatment means 14 directly feeds the sewage residue and contaminants from the waste residue separation means 3 and the waste pretreatment means 11. You may throw in waste and process it.

Further, the explanation has been made by mixing the residue and the contaminants with the waste while heating by the mixing means 12, but it is also possible to simply mix without heating.

[0050]

[Example] 0.3 kg of excess sludge having a water content of 82% generated by the nitrification denitrification treatment at the human waste treatment plant and the separated water from which the excess sludge was separated after the nitrification denitrification treatment were coagulated with ferric chloride 0.08 kg of coagulated sludge with a water content of 78% was mixed and crushed with vegetables, fruits, meat, fish, cooked rice, etc. to give a water content of 8
1.2 kg of 1% raw garbage slurry was mixed and diluted with 1.32 kg of water to prepare a mixture having a TS concentration of about 10%. The excess sludge and coagulated sludge had a dry matter weight ratio of 8:
It was set to be 2.

Then, the mixture was placed in an acrylic methane fermenter having a digestion period of 50 days and an actual volume of 5 liters, and the mixture was mixed with 55
The mixture was allowed to stay at 10 ° C. for 10 days, and methane fermentation was continuously processed by a gas stirring method. The water quality of the fermented product after 30 days is shown in Table 1.

[0052]

[Table 1] In addition, Table 2 shows the results obtained by subjecting the fermented product to dehydration treatment and measuring the fertilizing effect component. In addition, each ratio is a dry matter weight ratio.

[0053]

[Table 2] Further, 1000 ppm of magnesium hydroxide was added as a magnesium compound to the fermented product having the properties shown in Table 1, the reaction was carried out in a batch reaction for 24 hours, and the water quality of the supernatant after centrifugation was measured. The results are shown in Table 3.

[0054]

[Table 3] Table 4 shows the results of measuring the fertilizing components by further dehydrating the concentrated sludge after centrifugation. In addition, each ratio is a dry matter weight ratio.

[0055]

[Table 4] From the results shown in Tables 1 to 4, it is understood that the addition of the magnesium compound can remove phosphorus and ammonium as well as the organic substances caused by COD.

On the other hand, 3500 ppm of magnesium chloride hexahydrate was added to the fermented product shown in Table 1, the pH was appropriately changed by acid and alkali, and the reaction was carried out for 24 hours, and the supernatant was collected by centrifugation to obtain magnesium. The concentration of ions was measured. The results are shown in Table 5 and FIG.

[0057]

[Table 5] From the results shown in Table 5 and FIG. 2, by controlling the pH from 7.5 to alkaline, the concentration of residual magnesium ions is reduced, that is, the amount of magnesium ammonium phosphate as a fertilizing ingredient is produced by the reaction of magnesium. Can be seen to increase. It can be seen that when the pH is 8.0 or higher, the change in the amount of reduction of magnesium ions is small. Therefore, it is understood that phosphorus can be efficiently recovered as a fertilizing component by controlling the pH from 7.5, preferably 8.0 to the alkaline side.

[0058]

According to the waste treatment method of claim 1, after the liquid organic wastewater is biologically nitrified and denitrified,
In addition to solid-liquid separation into sludge and treated water, biodegradable solid organic waste and sludge are subjected to methane fermentation treatment so that the magnesium compound has a magnesium molar ratio of 1 or less with respect to the total phosphorus molar ratio. Is added so as to perform solid-liquid separation, and the resulting separated water is subjected to biological nitrification denitrification treatment together with organic sewage. Since the magnesium compound is separated and removed, the magnesium compound remains in the fermented product, and it is possible to prevent scale formation due to precipitation of the magnesium compound in a later step, and it is possible to stably treat the organic wastewater and the organic waste for a long period of time.

According to the waste treatment method of claim 2,
In addition to the effect of the waste treatment method according to claim 1, when the magnesium compound is added, the pH is controlled to an alkaline side of 7.5 or more, so that the addition of the magnesium compound efficiently improves the refractory magnesium ammonium phosphate. Precipitation can be generated and phosphorus compounds can be removed efficiently.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a waste treatment method of the present invention.

FIG. 2 is a graph showing the magnesium ion concentration by the addition of a magnesium compound at the same pH as above.

[Explanation of symbols]

4 Biological treatment means 5 First solid-liquid separation means 9 Sludge return means 14 Methane fermentation means 15 Reaction processing means 21 Second solid-liquid separation means 22 means for returning filtrate

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Sasaki 2-9-9 Surihori, Nishi-ku, Osaka-shi, Osaka Ataka Industry Co., Ltd. (56) Reference JP-A-2-63600 (JP, A) JP-A 10-216785 (JP, A) Japanese Patent Publication 1-25640 (JP, B2) Japanese Patent Publication 56-42272 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) C02F 3/28 -3/34 C02F 11/00-11/20 B09B 1/00-5/00

Claims (2)

(57) [Claims] 1. A liquid organic wastewater is subjected to biological nitrification / denitrification treatment, and then solid-liquid separation is performed into sludge and treated water, and biodegradable solid organic waste and the sludge are treated with methane. In a waste treatment method in which a fermented product obtained by fermentation is subjected to solid-liquid separation to separate the separated water into a biological nitrification denitrification process together with organic wastewater, a magnesium compound is added to the fermented product in the fermented product. The method for treating wastes is characterized in that the fermented product to which the magnesium compound is added is solid-liquid separated by adding the magnesium compound in a molar ratio of 1 or less with respect to the total phosphorus contained in. 2. The waste treatment method according to claim 1, wherein the pH of the magnesium compound is controlled to an alkaline side of 7.5 or more when the magnesium compound is added.