JPH09150193A - Treatment of organic sewage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment method for org. sewage which removes phosphorus and nitrogen at a high speed, obviates the generation of excess sludge, eliminates the need for the incineration equipment to be exclusively used for sludge and obviates the elution of heavy metals from incineration ashes. SOLUTION: A flocculating agent 10 is added to the org. sewage 8 of sewer, etc., to execute flocculation and sepn. 2. A separated liquid 12 is nitrified and denitrified by a biological treating stage 3 using packed beds of aerobic immobilizing microorganisms. Ozone 4 is added to the excess sludge 15 of this biological treating stage 3 and the sludge is returned 16 to the pre-stage of the denitrifying stage. The dehydrated cake 11 of the flocculated and separated sludge is mixed with org. waste 18, such as municipal refuse, and after the mixture is thermally cracked and gasified by a fluidized bed gasifying furnace 6, the flying ashes from this fluidized bed furnace 6 are melted and separated 19. The fluidized bed gasifying furnace 6 allows the utilization of the grit 9 discharged from a sewage settling basin as a fluid medium by supplying this grit together with the dehydrated sludge and the waste, such as municipal refuse, to the fluidized bed gasifying furnace.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for treating organic sewage, and more particularly to a method for rationally treating organic sewage such as sewage or human waste and waste such as municipal waste and various industrial wastes. Belong to

[0002]

2. Description of the Related Art Conventionally, sewage is biologically purified by an activated sludge method that requires a large installation area in a sewage treatment facility, and sewage sludge that is difficult to dehydrate is exclusively used in the sewage treatment facility. It is treated in the sludge dewatering equipment and incineration equipment. Therefore, a large amount of equipment cost and maintenance cost are required for the water treatment process and the sludge treatment process. In the case of human waste treatment, the exact same problem occurs. Furthermore, since sewage sludge incineration ash contains harmful heavy metals such as lead and mercury in a considerably high concentration, it is difficult to dispose of the ash. Further, since the sand discharged from the sewage settling basin is contaminated with organic substances such as human waste, conventionally, the sewage treatment water has been used to thoroughly wash the sand before it is landfilled. But,
Cleaning the sand is troublesome, and there is not enough land to dispose of the sand after cleaning.

Further, in recent years, it has been strongly demanded to improve the quality of treated sewage, so that removal of phosphorus and nitrogen is important. However, since biological removal rate of nitrogen is low, it has been a vast biological treatment in the past. Facilities were needed. It is also known to biologically nitrify and denitrify sewage by using a packed bed of granular filter media such as nitrifying bacteria and denitrifying bacteria-immobilized anthracite, but sewage contains a large amount of SS. Therefore, there is a big problem that the filling layer is significantly clogged,
It wasn't practical.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, removes phosphorus and nitrogen at high speed, and can significantly reduce the required area of the biological treatment tank for sewage. Eliminates the generation of excess dewatering sludge that makes it difficult,
A method for treating organic sewage that eliminates the need for a dedicated incinerator for sludge in sewage treatment facilities and human waste treatment facilities, eliminates the elution of heavy metals from incinerated ash, and eliminates the need to wash sediments and dispose of washed sand. The challenge is to provide.

[0005]

In order to solve the above problems, in the present invention, a coagulant is added to an organic wastewater such as sewage for coagulation separation, and the separated liquid is applied to a packed bed of immobilized microorganisms. In addition to nitrifying and denitrifying by the biological treatment process used, the dehydrated cake of the coagulated separation sludge is mixed with organic waste such as municipal waste, and pyrolyzed by a fluidized bed gasification furnace.
This is a method for treating organic sewage characterized by melting and separating fly ash from a fluidized bed furnace after gasification.

In the present invention, a coagulant is added to organic wastewater such as sewage to coagulate and separate, and then the separated liquid is nitrified and denitrified by a biological treatment process using a packed bed of immobilized microorganisms, Excess sludge in the biological treatment process is added ozone and returned to the previous stage of the coagulation separation process, and the dehydrated cake of the coagulation separation sludge is mixed with organic waste such as municipal waste and pyrolyzed by a fluidized bed gasification furnace. -It is a method for treating organic sewage characterized by melting and separating fly ash from a fluidized bed furnace after gasification. In the above method, the fluidized bed gasification furnace can be used by supplying the sand discharged from the sand basin of the wastewater as a fluid medium to the fluidized bed gasification furnace together with the waste such as the dehydrated sludge and municipal waste. .

[0007]

Next, the present invention will be described in detail.
FIG. 1 is an overall process diagram showing the flow of the treatment method of the present invention, and the treatment method of the present invention when targeting sewage will be described with reference to FIG. After the sewage 8 passes through the sand basin 1, coagulant (inorganic and organic coagulant) 10 is added,
Aggregation flocs are separated at high speed by the aggregation separation device 2. As the coagulation / separation device 2, an upflow filtration tank filled with a buoyant hollow cylindrical filter medium, or a blanket type high speed granulation / sedimentation device is suitable. Suitable inorganic coagulants are aluminum sulphate, ferric chloride and polyiron sulphate. It is sufficient that the injection rate of the inorganic coagulant is about 200 to 400 mg / l.

As the polymer flocculant, a polyacrylamide type anionic polymer flocculant is suitable. In this coagulation separation process, the sewage's SS BOD, SS, and phosphorus are highly (90%
Above) is removed. When a filter using a hollow cylindrical filter medium is applied to the coagulation / separation device 2, the particle size of the filter medium is 10
-40 mm, packed bed thickness 2-3 m, filtration rate 10
It is better to set it to 0 to 300 m / d. When a high-speed granulation / precipitation device (trade name: PBS-EBARA CORPORATION) is applied, the separation speed can be set to 500 to 1000 m / d.

Flocculant-separated water (SS
10 mg / l, BOD 30 mg / l, phosphorus 0.5 mg /
1, average water quality of 25 mg / l nitrogen) 12 is anthracite, plastic particles, granular activated carbon, zeolite,
90% or more of each of SS, BOD, phosphorus and nitrogen is introduced into the biological filter bed 3 consisting of a packed bed in which denitrifying bacteria and nitrifying bacteria are immobilized on the surface of granular filter material such as granular zeolite, and nitrifying and denitrifying at high speed. The removed clear treated water 14 is obtained. It is suitable that the particle size of the filter medium is 3 to 6 mm and the packed bed thickness is 1.5 to 2 m. Since the water flow rate to the packed bed can be set to a high value of 100 to 120 m / d, nitrogen can be removed in a remarkably short time of about 30 minutes as the residence time. When biologically removing nitrogen by the conventional activated sludge method, a residence time of 7 to 8 hours is required.

Since SS is removed by coagulation separation, the packing of the packed bed is extremely slow, but if it is operated for a long time, the filtration resistance of the packed bed gradually increases due to the growth of microorganisms. The packed bed is washed once a day (sufficiently once a day), and the washing drainage 15 is discharged. The cleaning wastewater 15 contains microbial sludge. To the microbial sludge, ozone is added to solubilize the microbial sludge in the ozone oxidation tank 4,
The solubilized sludge 16 containing OD is circulated in the coagulation separation step 2. The amount of ozone added is 20-based on the weight of microbial sludge SS.
30% is a suitable value. Since the SS BOD of sewage is coagulated and removed, the coagulated and separated water has a low BOD and lacks an organic carbon source for denitrification.
In the present invention, excess biological sludge is solubilized by ozone, and BO
Since D is generated and used as an organic carbon source,
This problem can be solved. In addition, since the hardly dehydratable surplus biological sludge is solubilized by ozone, there is a great effect that the surplus biological sludge hardly occurs.

Therefore, the sludge supplied to the dehydration step 5 is
Only the coagulation / separation sludge 11 (which has significantly better dehydration property than the surplus biological sludge) can be dehydrated extremely effectively, and even a low pressure dehydrator such as a belt press type dehydrator can easily remove low moisture. Since the dehydrated cake 17 (water content in the order of 70%) is obtained and the calorific value is improved, this leads to a reduction in fuel cost in the subsequent gasification / melting process. Further, by supplying the sludge 9 to the gasification step 6 together with the dehydrated sludge, municipal waste, etc. without washing, the sludge adhered to the sand can be thermally decomposed, and thus the conventional settling sand cleaning equipment is not required. . Further, in the gasification step 6, since a fluidized bed gasification furnace using sand as a fluid medium is used, the settled sand from the sewage can be used as supplementary sand for the settling fluidized bed furnace.

Next, the gasification / melting process will be described in detail with reference to FIG. The sewage sludge dewatering cake 17 and the settling sand 9 are supplied to the fluidized bed gasification furnace 6 together with wastes such as municipal waste 18 (biomass waste, plastic waste, automobile dismantling waste-for example, shredder dust) for pyrolysis gasification. receive. The reaction temperature for gasification is 450-80
Set to a relatively low temperature range of 0 degrees. The raw material that has fallen to the fluidized bed of the gasification furnace comes into contact with the fluidizing gas 23 (selected from air, oxygen-enriched air, and oxygen-steam mixture), and is rapidly pyrolyzed and gasified. As a result, gas, tar, carbide, and steam are produced, but the carbide is crushed by the disturbing motion of the fluidized bed to form char. These 24 are collectively
It is supplied to the primary combustion chamber of the swirling melting furnace 7 in the latter stage, and is rapidly oxidized at a high temperature of 1300 ° C. or higher while being mixed with oxygen in a swirling flow. Therefore, the ash contained in the char becomes slag mist, is captured on the furnace wall by the centrifugal force of the swirling flow, flows down the furnace wall and enters the secondary combustion chamber, and becomes slag 19 from the furnace bottom of the slag separation section. Is discharged.

The oxidation reaction is completed in the secondary combustion chamber and becomes a gas 25 composed of hydrogen, carbon monoxide, carbon dioxide and steam.
The gas 25 exiting the melting furnace 7 collects steam by the exhaust heat boiler 20, separates ash by the bag filter 21, and then cools and cleans it by the scrubber 22 using an aqueous sodium hydroxide solution to remove hydrogen sulfide and the like in the gas. To be removed. In this way, the purified syngas as the energy source 26 is obtained. This syngas can be supplied to a gas turbine to generate power, and the power can be used as power for an aeration blower for biological treatment in a sewage treatment facility. The heavy metal in the sewage sludge is completely fixed to the molten slag 19, so that the problem of heavy metal re-elution to the environment can be fundamentally solved. The slag 19 is a roadbed material, an aggregate,
It can be used as a material for civil engineering and construction. In addition, harmful substances such as dioxins, furans, and PCBs in waste 13
It is completely decomposed in a melting furnace with a high temperature of 00 degrees.

[0014]

According to the present invention, the following effects can be obtained. (1) Sewage can be highly purified in a short period of time with a biological treatment device that is significantly space-saving, and phosphorus, nitrogen, SS,
Since highly treated water from which BOD is highly removed can be obtained,
Can innovate sewage treatment. In addition, the sludge incineration facility of the sewage treatment facility is no longer required, which can greatly streamline the process. (2) When sewage is coagulated and separated, SS BOD is removed,
Although the organic carbon source for denitrification is insufficient, there is no problem in the present invention because the biological sludge is solubilized by the ozone to generate BOD, which is used as the organic carbon source for denitrification. (3) Surplus biological sludge, which is difficult to dehydrate and is extremely difficult to treat, is hardly generated.

(4) Since only raw sludge having good dewatering property (coagulated separation sludge) needs to be dewatered, a low-moisture dehydrated cake can be easily obtained and mixed with various wastes such as municipal waste,
Can be gasified and melted for energy saving. (5) Since the settled sand can be used as the fluidized medium of the fluidized bed gasification furnace, cleaning and disposal of the settled sand becomes unnecessary. (6) Since the harmful heavy metals contained in the sewage sludge are firmly fixed in the molten slag of ash such as municipal waste, the biggest problem (heavy metal problem) in the disposal of the sewage sludge is solved. (7) Energy can be recovered from waste such as sewage sludge, human waste sludge, and municipal waste.

[Brief description of the drawings]

FIG. 1 is an overall process diagram showing a flow of a processing method of the present invention.

FIG. 2 is a partial process diagram showing a gasification / melting portion.

[Explanation of symbols]

1: sand set basin, 2: coagulator / separator, 3: packed bed biological filter,
4: Ozone oxidation tank, 5: Dehydrator, 6: Gasification furnace, 7:
Melting furnace, 8: sewage, 9: sand set, 10: coagulant, 11: coagulated sludge, 12: separated water, 13: circulating liquid, 14: treated water,
15: Washing wastewater containing excess sludge, 16: Solubilized sludge, 1
7: Dehydrated cake, 18: Waste such as municipal waste, 19:
Molten slag, 20: waste heat boiler, 21: bag filter, 22: scrubber, 23: fluidized gas, 24: gas, tar, char, 25: gas, 26: energy source,

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C02F 11/10 C02F 11/10 Z

Claims (3)

[Claims] 1. An organic wastewater such as sewage is coagulated and separated by adding a coagulant, and then the separated liquid is nitrified and denitrified by a biological treatment process using a packed bed of immobilized microorganisms,
The dehydrated cake of the coagulated separation sludge is mixed with organic waste such as municipal waste, pyrolyzed and gasified by a fluidized bed gasification furnace, and then fly ash from the fluidized bed furnace is melted and separated. Method for treating organic wastewater. 2. A coagulant is added to organic wastewater such as sewage for coagulation and separation, and then the separated liquid is subjected to nitrification and denitrification by a biological treatment step using a packed bed of immobilized microorganisms, Excess sludge was added ozone and returned to the preceding stage of the denitrification process, and the dehydrated cake of the coagulation and separation sludge was mixed with organic waste such as municipal waste and pyrolyzed and gasified by a fluidized bed gasification furnace. A method for treating organic sewage, which comprises melting and separating fly ash from a fluidized bed furnace. 3. The fluidized bed gasification furnace, wherein the sand discharged from the sand basin of the wastewater as a fluid medium is supplied to the fluidized bed gasification furnace together with the waste such as the dehydrated sludge and municipal waste. The method for treating organic wastewater according to claim 1 or 2, characterized in that.