JP3276139B2 - Organic 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 method for treating organic waste, and more particularly to an anaerobic treatment of garbage, waste liquid containing high-concentration organic suspended solids (SS), etc. The present invention relates to a method for biological denitrification.

[0002]

2. Description of the Related Art Conventionally, most organic substances such as garbage are incinerated and landfilled together with other general garbage. But,
In recent years, efforts have been made to reduce the amount of garbage and recycle resources, in part by promoting the spread of household posters, sorting and collecting kitchen waste, and composting. Also, the nitrogen in the wastewater is
Some wastewater is treated by biological denitrification because it is a cause of eutrophication in closed water bodies. In the incineration of general garbage, garbage causes a change in calorific value, and there is a concern that dioxin may be generated due to chlorine in the garbage. Furthermore, one of the techniques for treating garbage is anaerobic digestion. Research and development of anaerobic digestion of garbage has been conducted in Japan for a long time, but it has not been put into practical use due to problems in the treatment of anaerobic digestion and desorbed liquid, which is a relatively high concentration wastewater.

[0003] Nitrogen in wastewater is strongly required to be removed as a causative substance of eutrophication in the water system to which it is discharged.
Anaerobic digestion has no nitrogen removal function. Currently, almost all of the nitrogen removal of wastewater is performed by biological denitrification. The most widespread method in this treatment is a nitrification liquid circulation system. This method converts nitric acid produced by nitrification of ammonia into BOD component (organic pollutant) in wastewater.
Can be used to denitrify, so that the amount of injection of a valuable reducing agent for denitrification, such as methanol, is extremely small, and the BOD component can be treated simultaneously with denitrification. However, in the anaerobic digestion treatment, since the BOD component is gas-treated, the amount of BOD remaining in the digestion and desorbed liquid of garbage becomes insufficient for denitrification, so that economical denitrification cannot be performed. was there.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and provides an anaerobic digestive solution for organic waste.
An object of the present invention is to provide a method for treating organic waste that can be efficiently and inexpensively denitrified.

[0005]

According to the present invention, an organic waste is separated into solids and separated water in a solid-liquid separation step, and the solids are solubilized in an acid fermentation step. After that, in the method for treating organic waste in which anaerobic digestion is performed in the anaerobic digestion step together with the separated water and the digested liquid is treated in the biological denitrification step, one of the solubilized liquid in the acid fermentation step is used. The organic waste in the biological denitrification step and denitrification treatment. In the method for treating an organic waste, it is preferable that the digested liquid in the anaerobic digestion step is subjected to solid-liquid separation in a dehydration step and the separated liquid is subjected to a denitrification treatment in a biological denitrification step. The solubilized liquid in the step is preferably subjected to solid-liquid separation and the separated liquid is injected into a biological denitrification step. At this time, the solid-liquid separation is performed in the solid-liquid separation step of the organic waste or the anaerobic treatment. It can be performed in the digestive juice dehydration step of the sexual digestion step. The organic waste of the present invention can be applied to garbage and / or waste liquid containing high-concentration organic suspended solids (SS).

[0006]

Next, the present invention will be described in detail with reference to the drawings. FIG. 1 is an example of an overall process diagram for implementing the processing method of the present invention. In FIG. 1, garbage 1 as organic waste is crushed and sorted in a pretreatment step 2, and sorted garbage 3 is separated into a squeezed liquid 5 and a dehydrated solid 6 by a screw press type juicer 4, and is squeezed. The juice 5 is introduced into the anaerobic digestion tank 7, and the organic matter in the influent is decomposed into biogas 8 under anaerobic conditions. The biogas 8 is stored in the gas tank 11 via the desulfurization device 11 ', and is used according to the application. Although not shown, the digestion tank 7 is subjected to mechanical stirring or gas stirring. The digestion / elimination liquid (digestion tank effluent) 9 is introduced into a sludge dewatering step 10 and separated into dewatered sludge 18 and dewatered separation water 12, and the separation water 12 flows into a denitrification step 13 which is a biological treatment apparatus. , Denitrification.

On the other hand, the dehydrated solids 6 from the juice extractor 4 are introduced into an acid fermentation step 14 under anaerobic conditions, and after the acid fermentation proceeds, a part of the lysate 15 And the remaining 15 is introduced into the anaerobic digestion tank 7. In the acid fermentation step 14, when the dewatered separated water 12 or the denitrified water 16 is injected as dilution water and the SS (suspended solids) concentration is adjusted to 10 to 15%, stirring and mixing become easy. In the acid fermentation step 14, the biodegradable organic matter is anaerobically decomposed, the organic acid is accumulated, and the pH is lowered. The BOD source containing the organic acid as the main component of the solubilizing solution 15 is a very excellent reducing agent for denitrification. Excess solubilizing solution 15 ′ as a reducing agent for denitrification is introduced into anaerobic digestion tank 7.

The excess sludge 17 in the denitrification step 13 may be introduced into the anaerobic digestion tank 7 or an acid fermentation step 14 (not shown) to reduce the volume. The denitrification step 13 can use a known biological denitrification method such as an economic digestive juice circulation system that can use the BOD component in the organic wastewater as a denitrification reducing agent, or a batch system. Garbage used in the present invention 1
Are those emitted from households, catering centers, restaurants, food processing factories, etc. For households, sorted garbage is desirable. The pretreatment step 2 is a step of removing non-biodegradable plastics, metals, and the like, and is a step of automatically separating foreign substances by a machine such as a garbage bag breaker, a soft or hard plastic separator, or a magnetic separator of irons. In addition, hand sorting is performed as needed. The garbage is desirably crushed and pulverized so as to be easily decomposed before or after sorting.

In the acid fermentation step 14, steam and the like are injected to operate at a water temperature of 50 to 55 ° C.
Is preferably 1 to 5 days. Thereby, the acid fermentation proceeds and the SS is solubilized, so that the fermentation of the anaerobic digestion can smoothly proceed. In the anaerobic digestion tank 7, organic matter is gasified at a water temperature of about 55 ° C. and a staying number of 10 to 15 days. In the dewatering step 10, in order to obtain the dewatered sludge 18 having a low water content, a sludge dewatering polymer is injected at about 1.0% of SS, and a conventional dewatering apparatus such as a centrifugal dewatering machine, a pelt press, a screw press, and a filter With a dehydrator such as a press, the water content is desirably 80% or less, preferably around 70%. If the properties of the digested sludge are good, the injection amount of the polymer can be reduced or not added.

Next, FIG. 2 shows another example of a process chart for carrying out the processing method of the present invention. In FIG. 1, when a relatively large amount of non-biodegradable SS is turbid together with an organic acid in the solubilizing solution 15, when the solubilizing solution is directly injected into the denitrification process 13, the excess sludge 17 of the The amount will be increased. In order to prevent this, in FIG. 2, the solubilized solution 15 is introduced into the juice extractor 4 to separate SS and the separated solution 19
The required amount 19 ′ from the above is distributed and injected into the denitrification step 13,
The remainder is injected into the anaerobic digestion tank 7. When the present invention is applied, a single juice extractor 4 may be used at different times or a plurality of juice extractors 4 may be installed. In the present invention, since the ratio of the biodegradable solid in the dehydrated solid 6 from the squeezing machine 4 gradually increases, it may be appropriately discharged as the surplus dehydrated solid 20. As described above, the juice extractor 4 may be used also for the separation of the SS of the solubilized solution 15, but as shown in FIG. 1
The solubilized liquid 15 may be transferred to the second side so that the SS of the solubilized liquid 15 is discharged together with the dewatered sludge 18.

Next, FIG. 4 shows an example of a process chart in which the treatment method of the present invention is applied to wastewater treatment containing a high concentration of organic SS. Wastewater applied to this method includes food processing wastewater, night soil, septic tank sludge, animal manure, and the like. In FIG. 4, SS is separated from wastewater 21 in a solid-liquid separation step 22. In the step 22, a screen, a centrifuge, a sedimentation tank, and the like are used. The separated water 23 is introduced into the anaerobic digestion tank 7, and is treated in the same manner as in FIG. The solids 24 are solubilized in the acid fermentation step 14, and the solubilized liquid 15 is introduced into a solid-liquid separation device 25 such as a screw press dehydrator, and separated into dehydrated sludge 26 and solubilized separated water 27. Part of the solubilized separated water 27 is introduced into the denitrification step 13 and is used for denitrification together with the dewatered separated water 12 of the anaerobic digestive juice. As a denitrifying reducing agent,
Excess solubilized separated water 28 is introduced into the anaerobic digestion tank 7.
The excess sludge 17 can be reduced in volume and gasified by being introduced into the anaerobic digestion tank 7.

[0012]

【Example】

Hereinafter, the present invention will be described specifically with reference to examples. Example 1 An example in which the present invention was performed according to the process diagram of FIG. 1 will be described. Sorted garbage (3): 5t / day, Juice machine (4): screw press, juice volume (5): 4t / day, Anaerobic digestion tank (with gas stirring equipment) (7), Effective volume: 50m ^3. Water temperature: 55 ° C, staying days: 10 days, treatment amount: 5 t / day, dehydrator (10): screw press dehydrator, cationic polymer injection amount (for sludge): SS 0.3 to
1.0%, dehydrated separated water NH ₃ —N: 1100 mg / l, separated water amount: about 11.4 m ³ / day, dry solid matter amount: 285 kg / day,

[0013] Acid fermentation tank (dilution adjustment tank: with vertical screw stirrer, attached to sediment discharge pipe) (14), effective volume: 10 m ³ , water temperature: 55 ° C., injection amount of dewatered separated water: 7 m ³ / day, solubilization Digestion tank distribution amount of liquid 15: 7.4 m ³ / day, dehydrated solids amount (6): 1 t / day, number of staying days: 2 days, denitrification step (13): nitrification liquid circulation type membrane separation method, total effective volume 30m ³ , Treatment water temperature: 35 ° C, Denitrification step dissolving solution 15 distribution amount: 0.6m ³ / day, Treatment water amount: about 5m ³ / day,

Embodiment 2 An embodiment in which the present invention is carried out according to the process chart of FIG. 2 will be described. Sorted garbage (3): 5t / day, Juice machine (4): screw press, squeezed liquid volume (5): 4t / day, surplus dehydrated solids (6): 0.2t / day, anaerobic digestion tank (With gas stirrer) (7), effective volume: 50 m ³ , water temperature: 55 ° C., staying days: 10 days, throughput: 5 t / day, dehydrator (10): screw press dehydrator, cationic polymer injection amount ( (For sludge): SS 0.3 ~
1.0%, dehydrated separated water NH ₃ -N: 1200mg / l, separating water: about 11.4 m ³ / day, dry solid amount: 290 kg / day,

[0015] Acid fermentation tank (dilution adjustment tank: with vertical screw stirrer, with sediment discharge pipe) (14), effective volume: 10 m ³ , water temperature: 55 ° C., injection amount of dewatered and separated water: 7 m ³ / day, staying days : 2 days, denitrification step (13): nitrification liquid circulation type membrane separation method, total effective volume: 30 m ³ , treatment water temperature: 35 ° C., distribution amount of separation liquid 19 in denitrification step: 0.6 m ³ / day, treatment Water volume: about 5m ³ / day,

Embodiment 3 An embodiment in which the present invention is carried out according to the process chart of FIG. 3 will be described. Sorted garbage (3): 5t / day, Juice machine (4): screw press, juice volume (5): 4t / day, Anaerobic digestion tank (with gas stirring equipment) (7), Effective volume: 50m ^3. Water temperature: 55 ° C, staying days: 10 days, treatment amount: 5 t / day, dehydrator (10): screw press dehydrator, cationic polymer injection amount (for sludge): SS 0.3 to
1.0%, dehydrated separated water NH ₃ —N: 1250 mg / l, separated water amount: about 12 m ³ / day, dry solid matter amount: 295 kg / day,

[0017] Acid fermentation tank (dilution adjustment tank: with vertical screw stirrer, attached to sediment discharge pipe) (14), effective volume: 10 m ³ , water temperature: 55 ° C., injection amount of dewatered separated water: 7 m ³ / day, solubilization Distribution amount of liquid 15 in digestion tank: 7.4 m ³ / day, number of staying days: 2 days, denitrification process (13): nitrification liquid circulation type membrane separation method, total effective volume: 30 m ³ , treatment water temperature: 35 ° C., acceptable Dehydrator distribution amount of lysate 15: 0.6 m ³ / day, treated water amount: about 5 m ³ / day,

Embodiment 4 An embodiment in which the present invention is carried out according to the process chart of FIG. 4 will be described. Food processing wastewater (21): 100 m ³ / day (SS 1%), solid-liquid separation step juicer (22): fine mesh screen (opening 0.7 mm), screen separation water (23): 85 m ³ / day , Screen sieve (concentration 6%) (24): 15 m ³ / day, Anaerobic digestion tank (with gas stirring equipment) (7), Effective volume: 1000 m ³ , Water temperature: 55 ° C, Staying days: 10 days, Dehydration Machine (10): Centrifugal dehydrator, Injection amount of cationic polymer (for sludge): 0.3 to 1.0% based on SS, Dewatered separated water NH ₃ -N: 850 mg / l, Separated water amount: about 92 m ³ / day, Dry solids: 200 kg / day,

Acid fermentation tank (dilution adjusting tank: vertical screw stirrer, attached to sediment discharge pipe) (14), effective volume: 60 m ³ , water temperature: 55 ° C., inflow liquid retention time: 4 days, solid-liquid separation device ( 25): Screw press dewatering machine, dewatered separated water (27): 14 m ³ / day, dewatered sludge (26): 1 t / day, denitrification step (13): nitrification liquid circulation type membrane separation method, total effective volume: 200 m ³ , treated water temperature: 30 ° C, solubilized separated water 27, denitrification process distribution amount: 4.5 m ³ / day, treated water amount: about 100 m ³ / day,

(Processing results) Table 1 shows the processing results of Examples 1, 2 and 3, and Table 2 shows the processing results of Example 4. As a comparative example, the lysate of the acid fermentation was not distributed to the denitrification step.
The results of the conventional processing method shown in the process chart of FIG. The amount of sorted garbage, the amount of food processing wastewater, the volume of the digestion tank, and the volume of the denitrification process of each comparative example are the same as those shown in the examples.

[Table 1]

[0021]

[Table 2] According to the present invention, high-rate nitrogen treatment can be performed without using methanol as a reducing agent for denitrification. In the comparative example, when methanol was not used, high concentrations of NH ₃ —N and NO _x —N remained in the treated water.

[0022]

According to the present invention, a high rate of biological denitrification of an anaerobic digestion / desorption solution is carried out with little or no use of an external valuable reducing agent such as methanol. be able to.

[Brief description of the drawings]

FIG. 1 is a process chart showing an example for carrying out a processing method of the present invention.

FIG. 2 is a process chart showing another example for carrying out the processing method of the present invention.

FIG. 3 is a process chart showing another example for carrying out the processing method of the present invention.

FIG. 4 is a process chart showing another example for carrying out the processing method of the present invention.

FIG. 5 is a process chart for implementing a conventional processing method used as a comparative example.

[Explanation of symbols]

1: garbage, 2: pretreatment step, 3: sorted garbage, 4: juicer, 5: juice, 6: dehydrated solid, 7: anaerobic digester, 8: biogas, 9: digestion Syneresis, 10: sludge dewatering process, 11: gas tank, 11 ': desulfurization device, 12: dewatered separated water, 13: denitrification process, 14: acid fermentation process, 15:
Solubilized solution, 16: denitrification treated water, 17: excess sludge, 18:
Dehydrated sludge, 19: separated liquid, 20: surplus dehydrated solids, 2
1: waste water, 22: solid-liquid separation step, 23: separated water, 24:
Solids, 25: solid-liquid separator, 26: dehydrated sludge, 27:
Solubilized separation water

Claims (4)

(57) [Claims] 1. An organic waste is separated into solids and separated water in a solid-liquid separation step, and the solids are solubilized in an acid fermentation step, and then anaerobically digested in the anaerobic digestion step together with the separated water. In the method for treating organic waste, wherein the digestive juice is treated in a biological denitrification step, a part of the lysate in the acid fermentation step is injected into the biological denitrification step to perform a denitrification treatment. A method for treating organic waste. 2. The organic waste according to claim 1, wherein the digested liquid in the anaerobic digestion step is subjected to solid-liquid separation in a dehydration step, and the separated liquid is subjected to a denitrification treatment in a biological denitrification step. How to handle things. 3. The organic waste treatment according to claim 1, wherein the solubilized solution in the acid fermentation step is solid-liquid separated and the separated solution is injected into a biological denitrification step. Method. 4. The organic waste according to claim 3, wherein the solid-liquid separation is performed in a solid-liquid separation step of the organic waste or a dehydration step of digestion liquid in the anaerobic digestion step. Processing method.