JP3347673B2 - Waste treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for treating waste. More specifically, the present invention relates to a treatment method for purifying and landfilling waste discharged from, for example, an incineration plant or a factory.

[0002]

2. Description of the Related Art Conventionally, various types of wastes have been incinerated or crushed and then transported to a landfill (final disposal site). It is naturally removed and purified mainly by rainwater. Then, the quality of the rainwater leached through the waste is inspected, and when the predetermined water quality condition is satisfied, the treatment is determined to be completed.

[0003] However, since the purification depends on rainwater, it takes a long time to complete the treatment. In other words, rainwater descends in the landfill waste layer due to gravity, so a defined precipitation path (also called water path) is formed, and newly rainwater also descends the above water path. Waste is not distributed uniformly. As a result, it is difficult to sufficiently remove contaminants in the waste layer, and it takes a long time to complete the treatment. Therefore, it is necessary to carry out the purification treatment of the leachate leached from the waste layer over a long period of time.

The following method is known as a treatment for purifying leachate.

[0005] As shown in FIG. 4, the leachate from the landfill 51 is adjusted in its flow rate by a flow rate adjusting device 52 and then sent to a calcium removing device 53 to be subjected to a calcium removing process. Next, this treated water is supplied to biological treatment equipment
In 4, the contained organic matter is decomposed by microorganisms, and the contained matter is subjected to coagulation and sedimentation treatment in the coagulation and sedimentation equipment 55, and then the pH of the treated water is adjusted. Next, after being filtered in the sand filtration equipment 56, the organic matter is adsorbed and removed in the activated carbon adsorption equipment 57. Then, the water is separated into treated water 60 and concentrated water 61 by a concentration treatment facility 59 via a chelate adsorption treatment facility 58, and the treated water 60 is discharged into a river or the like.

[0006] However, when the salt concentration of the leachate is high or when it contains organic substances which are hardly decomposable, it is difficult to decompose it with microorganisms, and some organic substances cannot be adsorbed by activated carbon. Have.

On the other hand, the concentrated water 61 often contains a large amount of salt, but is dried and buried without being reused or incinerated in an incinerator.

As described above, the treatment of leachate requires a large-scale facility, which may not be able to sufficiently treat the leachate, and also wastefully discards the salt in the concentrated water. ing.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object to provide a waste disposal method that can efficiently treat washing water accompanying waste treatment and can be disposed of finally. I have.

[0010]

Processing method of the present invention, in order to solve the problems] includes a cleaning step of cleaning the waste with cleaning water, a water treatment step of treating the waste wash liquid by the water treatment apparatus comprising a membrane separation device, the water treatment Generated in the membrane separation equipment in the process
Salt production step of heating and drying the concentrated liquid to produce by-product salt
If, includes a landfill step of landfill waste that has been cleaned in the cleaning step, you in the salt formation step
And drying the above concentrated liquid under a nitrogen gas atmosphere.
Ru der made by heating to 00-550 ° C. In the present invention
Such another processing method is a method of treating under a nitrogen gas atmosphere.
Instead of heating at 0-550 ° C, 800
Heated to ゜ C.

[0011] Therefore, since the waste before the landfill treatment is actively washed without being subjected to natural rainfall, the purification treatment of the waste is completed in a short period of time. As a result, it is not necessary to leave the final disposal site (reclaimed land) for waste for a long period of time, and early use is possible. Further, in order to treat the washing waste water with a water treatment device including a membrane separation device,
The drainage system is simplified, and the treated water can be effectively used. In addition, more effective treatment of cleaning waste liquid
Or harmful organic substances such as dioxins are decomposed
Since the salt in the concentrated water can be recovered and used effectively,
It is an inexpensive processing method. Also, under the nitrogen atmosphere described above,
In the salt formation step of heating, after the concentrated solution is dried,
Before heating to 300-550 ° C under a raw gas atmosphere,
Baking by heating to 500-700 ° C
preferable.

[0012]

[0013]

Further, in the above-mentioned treatment method, the amount of water used can be reduced by circulating the treated water generated in the water treatment step as washing water for waste.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a processing method according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a flowchart showing one embodiment of the processing method of the present invention.

In FIG. 1, reference numeral 1 denotes a washing device for washing waste W, to which a washing water supply pipe 2 and a drain pipe 3 are connected. Normally, tap water or industrial water is supplied to the washing water supply pipe 2 as makeup water. A drainage pipe 3 is connected to a membrane separation device 4 as a water treatment device for wastewater treatment. The membrane separation device 4 is provided with a drainage port 5 and a return pipe 6. Return piping 6
Is connected to the washing water supply pipe 2. As a result, the waste W is put into the washing device 1 and washed, and the waste water after washing is filtered by the membrane separation device 4 and is returned to the washing water supply pipe 2 as needed for circulation. The concentrated water from the drain port 5 of the membrane separation device 4 is dried and purified to obtain salt S.
To manufacture. FIG. 1 shows a reference example including concentrated water.
To meet conditions such as ingredients, economics of processing, and user requirements.
The process used as kneading water during solidification of cement was also shown.
ing.

On the other hand, the waste W charged into the cleaning device 1 and subjected to the purification treatment is conveyed to the final disposal site (landfill) L and is landfilled as it is. Since the purification of the waste W is performed by the cleaning device 1, it is completed in a very short time.

As described above, both the waste and the cleaning waste liquid are rendered harmless and treated in a short period of time.

As the washing device 1, for example, a rotating drum type washing device, a screw type washing device, a stirring tank, a shaking device, an upward flowing water tank, and the like are employed.

As an example of a rotary drum type washing machine, there is a type in which waste is put into an inclined drum rotating around its own axis, and washing water is supplied from near the upper end of the drum.
By rotating the drum, the waste is agitated and the washing water is uniformly distributed to the waste to remove the contaminants.

As an example of a screw-type washing apparatus, there is an apparatus in which a screw is extended in an axial direction in an inclined cylindrical housing and washing water is supplied from near the upper end of the housing. The screw is rotated to knead while sending the waste inside, and the washing water is uniformly distributed to the waste to remove the contaminants.

As an example of the stirring tank, there is a stirring tank provided with stirring blades inside a tank into which waste is charged, and washing is performed by supplying cleaning water while stirring the waste.

The shaking device is for shaking the container into which the waste has been charged to agitate the waste therein, and at the same time, supplying washing water for washing. This apparatus can also stir the waste, uniformly distribute the washing water to the waste, and remove contaminants.

In any of the cleaning apparatuses, washing water can be evenly distributed by sufficiently stirring the waste, and pollutant removal can be promoted even by collision between the wastes.

On the other hand, in the upward flow water tank, a large tank for charging waste is constructed, a water supply pipe is provided at the bottom of the tank, and a drain pipe for collecting and draining washing water is provided above the tank. Is provided. By supplying the washing water from the water supply pipe into the tank, the waste in the tank is immersed in the washing water, so that the washing water is uniformly distributed throughout the waste. Then, the contaminants are washed out upward. Even in the cleaning apparatus using the upward flowing water tank, the cleaning period is significantly reduced as compared with the conventional waste cleaning by natural rainfall.

Next, as the above-mentioned membrane separation device 4, for example, one using an electrodialysis method, one using a reverse osmosis membrane method, or the like is used. What used electrodialysis method,
A cation membrane that allows only cations to permeate and an anion membrane that allows only anions to permeate are alternately arranged, and a direct current is used to separate ions in the waste liquid. On the other hand, the method using the reverse osmosis membrane method applies an operating pressure equal to or higher than the osmotic pressure to the waste liquid, allows only water to permeate through the reverse osmosis membrane, and separates ions and organic substances. As the form of the reverse osmosis membrane element, a flat plate type, a tube type, a spiral type, a hollow fiber type and the like are adopted. Which device to use may be determined according to the degree of contamination of the waste, for example, the concentration and type of the contained pollutants. Further, some of the reverse osmosis membrane methods use a reverse osmosis membrane having a coarse mesh at a low operating pressure (so-called low pressure reverse osmosis method or loose reverse osmosis method). May be adopted according to the degree of contamination. Further, depending on the substance contained in the waste, for example, a calcium removal facility may be provided in addition to the membrane separation device 4 as a water treatment device.

When the waste liquid treatment is performed by such a membrane separation device 4, the filtered water (treated water) is purified to such an extent that it can be sufficiently reused as a washing liquid, as described later.

On the other hand, the concentrated water produced during the purification treatment of waste wash liquid by the membrane separation device 4, Drying as shown in FIG. 1, it is harmless purified. FIG. 1 shows a cell as a reference example.
The cement solidification process is also shown.

FIG. 2 shows an outline of a cement solidification treatment process as a reference example . In the figure, reference numeral 7 denotes a kneading / molding machine, and a cement bunker 8 for putting cement into the kneading / molding machine 7 is disposed above. A predetermined amount of cement is put into the kneading molding machine 7 by the measuring device 8a. On the other hand, the concentrated water generated in the membrane separation device 4 is stored in the concentrated water storage tank 9, and
As a result, a predetermined amount of water is supplied to the kneading molding machine 7. In the kneading molding machine 7, a predetermined amount of cement and a predetermined amount of concentrated water are kneaded for a predetermined time, and the kneaded material is discharged by the conveyor 11. The kneaded material is cured on the conveyor 11 for a predetermined time. After that, they are transported to the landfill by transportation means such as the truck 12. As a method of kneading the cement, a known type such as a band type with a paddle, a vibration type, and a pan type is adopted.

Actually, the waste is washed with washing water, the washing waste liquid is concentrated, the concentrated water and cement are mixed and solidified, and then crushed to form a heavy metal specified in Notification No. 13 of the Environment Agency. A dissolution test was performed. As a result, all heavy metals such as lead were below the standard values specified in the “Prime Minister Ordinance that Determines Judgment Standards for Industrial Waste Containing Metals and the Like” (No. 61 of the Prime Minister's Ordinance No. 61 in 1994). Therefore, even if the content is recovered as a purified salt, it is effective for treating concentrated water such that the salt cannot be used for industrial use or the like.

If permitted, waste such as fly ash may be charged into the kneading and molding machine 7 and mixed and kneaded. In that case, a fly ash bunker (not shown) provided with a measuring device is provided above the kneading and molding machine 7.

Next, referring to FIG. 3, one example of a method for producing a salt by drying and purifying the concentrated water instead of solidifying the cement.
An embodiment will be described. The concentrated water generated in the membrane separation device 4 is stored in the concentrated water storage tank 13 in FIG. This concentrated water is sent to a scrubber 15 by a feedwater pump 14. In the scrubber 15, the concentrated water is preheated by exhaust gas from a drying / firing furnace 16 described later, and thereafter, the exhaust gas is purified and discharged in the activated carbon packed tower 17.

On the other hand, the preheated concentrated water is sent to a feeder 19 by a pump 18 and sent to the drying / firing furnace 16 while being measured therefrom. In the drying / sintering furnace 16, the concentrated water is heated to 100 to 150 ° C., and the moisture is evaporated and dried. Next, air is sent to the drying / sintering furnace 16 by the compressor 20, and the inside of the furnace is
By heating to 00 ° C. and agitating the stirring blades 21 in the furnace, the dried material is baked, and the contained organic matter is burned and removed.

After the drying and firing, the atmosphere in the furnace is replaced by nitrogen gas from a nitrogen cylinder 22. In this state, the inside of the furnace is heated to 300 to 550 ° C., and harmful organic substances such as dioxins remaining in the furnace are decomposed by the stirring of the stirring blades 21 in the furnace.

In the above furnace heating step, the high-temperature air and high-temperature nitrogen gas in the furnace are appropriately used for preheating the concentrated water in the concentrated water storage tank 13 and the concentrated water in the scrubber 15.

Finally, salts (NaCl, etc.) remain in the furnace. This salt S is sent to the cooling vessel 23 and
Rapidly cooled to ゜ C. Through the above steps, high-grade by-product salt S is recovered. Such by-product salt S is industrially useful.

In the above method for producing a salt, the above 5
The heating step at 00 to 700 ° C. may be omitted.

Alternatively, instead of the above heating step at 500 to 700 ° C. and the heating step at 300 to 550 ° C. in a nitrogen gas atmosphere, heating at 800 ° C. or more may be performed in an oxidizing atmosphere. In any case, the by-product salt can be recovered.

After actually washing the waste with washing water and concentrating the washing waste liquid, calcium and manganese were removed, and the concentrated water was calcined in an air atmosphere at 600 ° C. for 3 hours, and then at 450 ° C. By heating for 1 hour in a nitrogen atmosphere, Ca is 0.05% or less and TOC is 80 m
g / kg or less, dioxin concentration is 1.0pg-TEQ
/ G or less. This by-product salt can be used in the chemical industry, metal refining industry, and the like.

(Test Example) Next, a test for confirming the quality of the treated water filtered by the membrane separation device 4 was performed, which will be described (Table 1). Further, as described above, it has been confirmed by a cleaning test that the treated water is purified to such an extent that it can be sufficiently reused as a cleaning liquid (Table 2), and this will also be described.

(1) First, 100 g of incinerated main ash and 20 g of incinerated fly ash were mixed well and charged into a 2-liter polypropylene container. To this container, 1.2 liters of pure water was added as a washing liquid.

(2) Then, the above-mentioned container is discharged at a rate of 2 per minute.
After shaking for 1 hour at 00 cycles, the whole liquid in the container was filtered with a glass fiber filter paper having a pore size of 1 micrometer.

(3) Next, the above filtrate was further filtered through a reverse osmosis membrane, and the conductivity of the reverse osmosis membrane filtrate was measured by an AC two-electrode method.

Table 1 shows the results. Table 1 also shows the conductivity of pure water and tap water measured by the AC two-electrode method as a comparative example. Note that EC in Table 1 is conductivity, and the unit is μS / cm (micro Siemens / centimeter).

[0046]

[Table 1]

The electrical conductivity is data substantially indicating the concentration of the dissolved substance in the liquid, and is useful for judging the degree of purification. The results show that the reverse osmosis membrane filtrate has a lower conductivity than tap water, which is usually used as wash water, if not as much as pure water. In other words, it is understood that the treatment is performed to such an extent that the washing water can be sufficiently used.

(4) Next, the pH of the final filtrate of the above (3) is adjusted to about 7.0, and this reverse osmosis membrane filtrate is used as a washing liquid instead of pure water to carry out the washing operations of the above (1) and (2). Was repeated, and the conductivity (EC) of the filtrate was measured by the AC two-electrode method.

Table 2 shows the results. Table 2 also shows, as a comparative example, the conductivity of the filtrate after the washing operation in (1) and (2) above using pure water as a washing solution by an AC two-electrode method.

[0050]

[Table 2]

According to the test results, the cleaning waste liquid with pure water and the cleaning waste liquid with the reverse osmosis membrane filtrate show almost the same conductivity. This means that even if the waste is washed with any of the washing liquids, the same amount of dissolved substances can be washed out, that is, the washing degree is equivalent. Therefore, it can be said that it is effective to circulate and use the reverse osmosis membrane filtrate, that is, the treated water filtered by the membrane separation device 4 as washing water.

[0052]

According to the present invention, the waste can be cleaned in a short period of time by actively cleaning the waste, so that the landfill can be used early. Further, since the washing waste liquid is subjected to water treatment by a water treatment device including a membrane separation device, a drainage facility is simplified, and the treated water can be effectively used. Further, it becomes possible to recover the content of the concentrated water as a by -product salt. That is, the cleaning waste liquid can be used effectively, and a clean waste disposal method can be realized.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a process of an embodiment of the processing method of the present invention.

FIG. 2 is a flowchart outlining a cement solidification process as a reference example additionally shown in FIG. 1;

FIG. 3 is a flowchart showing an outline of a process of drying and purifying concentrated water in the process of FIG. 1;

FIG. 4 is a flowchart schematically showing a conventional cleaning waste liquid treatment method.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Kenji Katsura 7-4 A-103 Takamaru, Tarumizu-ku, Kobe-shi, Hyogo (56) References JP-A-9-308371 (JP, A) JP-A-8- 309313 (JP, A) JP-A-8-3655 (JP, A) JP-A-1-284381 (JP, A) Minoru Sawachi, Isao Fukunaga, Outline of Fly Ash Water Cleaning Treatment Method, PPM, Japan, Inc. ) Nippon Kogyo Shinbunsha, April 1, 1995, vol. 26 (4), p. 17-23 (58) Field surveyed (Int. Cl. ⁷ , DB name) B09B 1/00 B09B 3/00 C02F 1/44

Claims (4)

(57) [Claims] A washing step of washing waste with washing water; a water treatment step of treating washing waste liquid by a water treatment apparatus including a membrane separation apparatus; and a condensate produced in the membrane separation apparatus in the water treatment step. A salt producing step of heating and drying to produce a by-product salt, and a landfilling step of landfilling the waste washed in the washing step, wherein in the salt producing step, after drying the concentrated solution, A method for treating wastes by heating to 300 to 550 ° C. in a nitrogen gas atmosphere. 2. A said salt-forming step, after drying the concentrated solution, before heating to 300 to 550 ° C in a nitrogen gas atmosphere, formed by sintering by heating the 500 to 700 ° C according Item 6. The method for treating waste according to Item 1 . 3. A washing step of washing waste with washing water, a water treatment step of treating the washing waste liquid with a water treatment device including a membrane separation device, and a concentrated solution generated in the membrane separation device in the water treatment process. A salt producing step of heating and drying to produce a by-product salt, and a landfilling step of landfilling the waste washed in the washing step, wherein in the salt producing step, after drying the concentrated solution, A method for treating wastes by heating to 800 ° C. in an oxidizing atmosphere. 4. The method for treating waste according to any one of claims 1 to 3 , wherein the treated water generated in the water treatment step is circulated as washing water for waste.