JPH1076295A - Wastewater treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wastewater treatment method capable of removing dioxins to a drinkable level and simplifying a process and an apparatus configuration. SOLUTION: Heavy metals such as calcium and manganese in sewage water 38 are coagulated, sedimented and separated in a calcium removal facility 32, and organic pollutants such as nitrogen and BOD substances are biologically removed in a biological treatment facility 33. And the like are separated by the membrane separation device 53. The dioxin in the biologically treated water 55 and the remaining soluble organic pollutants are decomposed by ultraviolet light and high-concentration ozone in the dioxin removal facility 34, and the remaining dioxin and heavy metals are removed in the activated carbon adsorption tower 63.

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 sewage containing harmful substances such as leachate at a general waste landfill site or an industrial waste landfill site.

[0002]

2. Description of the Related Art Sewage containing harmful substances, such as leachate from general waste landfills and industrial waste landfills, is treated by the flow shown in FIG.

[0003] Water 1 to be treated such as leachate is introduced into a pretreatment facility 2 and subjected to pretreatment in a regulating tank 3 and a raw water tank 4 to reduce fluctuations in water quality and water amount. Then, the pretreated water 1 ′ is introduced into the calcium removal equipment 5, and an inorganic coagulant 7 such as sodium carbonate 6 or ferric chloride or a polymer coagulant 8 is added, whereby the water 1 The calcium in the 'is coagulated and precipitated as calcium carbonate, and heavy metals such as manganese are coagulated and precipitated, and the precipitate is separated in the sedimentation tank 9. At this time, caustic soda 1 as a pH adjuster
0 and sulfuric acid 11 are added.

Next, the water to be treated 12 from which the sediment has been separated is introduced into the biological treatment equipment 13 and circulated from the aerobic tank 15 to the anaerobic tank 14 while flowing into the anaerobic tank 14 and the aerobic tank 15 sequentially. By adding methanol 16 as necessary, BOD substances and TN in the water to be treated 12 are decomposed and removed by the action of microorganisms.

[0005] Next, the biologically treated water 17 is introduced into a coagulation and sedimentation treatment equipment 18, and an inorganic coagulant 19 and a polymer coagulant 20 are added thereto, whereby CO 2 in the water 17 is removed.
The D substance, suspended substance, TP and the like are coagulated and precipitated, and the precipitate is separated in the precipitation tank 21. At this time, caustic soda 22 and sulfuric acid 23 as a pH adjuster are added.

Next, the water to be treated 24 from which the precipitate has been separated is introduced into a sand filtration / activated carbon adsorption equipment 25, and fine suspended substances in the water to be treated 24 are captured by a sand filter 26. At 27, the remaining COD substance, chromaticity component and the like are adsorbed and removed to obtain treated water.

[0007]

However, in the conventional processing flow as described above, dioxins can be reduced in biological treatment facilities, but their removal rate is low,
Although the biodegradable COD substance can be removed by coagulation sedimentation or activated carbon adsorption, COD 10 mg /
L was the limit.

[0008] Further, since the process and the equipment configuration are complicated, the construction cost and the maintenance cost are both high, and a high technology is required for the maintenance. An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a method for treating sewage, which can remove dioxins to a level at which beverages can be consumed and can simplify the process and the apparatus configuration.

[0009]

Means for Solving the Problems To solve the above problems, a method for treating sewage according to claim 1 of the present invention is a method for treating leachate in a general waste landfill site or an industrial waste landfill site.
When treating sewage containing harmful substances, the sewage is introduced into a calcium removal facility, and heavy metals such as calcium and manganese in the sewage are separated by coagulation and sedimentation by the addition of a coagulant. The treated water is introduced into a biological treatment facility equipped with a membrane separation device, and organic pollutants such as nitrogen and BOD substances in the coagulation treatment water are biologically removed by microorganisms. The biologically treated water from which the organic pollutants and the suspended matter have been separated and removed is introduced into a combined dioxin removal equipment using ultraviolet rays and ozone, and the dioxin and the remaining dissolved substances are removed from the biologically treated water. Organic pollutants are decomposed by ultraviolet rays and high-concentration ozone, and ultraviolet / ozone-treated water flowing out of the dioxin removal equipment is introduced into an activated carbon adsorption tower. , Dioxin and heavy metals remaining in the ultraviolet-ozone treated water removed by adsorption by activated carbon, is obtained so as to take out the activated carbon treated water flowing out from the activated carbon adsorption tower as a final treated water in the system.

In the method for treating sewage according to the second aspect of the present invention, a part of the ultraviolet / ozone-treated water flowing out of the dioxin removal equipment is circulated to the inflow side thereof, thereby securing a residence time in the equipment of 30 to 300 minutes. It is something to do.

According to a third aspect of the present invention, there is provided a dioxin removal facility, wherein
Either irradiate both regions of 50 nm with ultraviolet light, or
While irradiating ultraviolet rays in a range of 0 ± 50 nm,
Ozone is supplied so as to be ± 10 gO ₃ / m ³ .

According to the configuration of the first aspect, since heavy metals such as calcium and manganese are separated in the calcium removing facility, the CaCO ₃ scale adheres to the membrane surface of the membrane separation device in the biological treatment facility. And to prevent membrane blockage due to biological slime
Even when back washing is performed with aClO, MnO ₂ is not generated in the permeation flow path of the membrane separation device and adheres to the membrane surface or the like, thereby preventing a reduction in permeation flux and membrane blocking.

[0013] The biological treatment equipment uses nitrogen or BOD.
As a result, organic pollutants such as substances are removed and suspended substances such as microorganisms are separated by a membrane separation device. As a result, dioxin decomposition inhibitors, that is, suspended substances and scavengers, are used in the dioxin removal equipment that combines UV and ozone. Dioxin is efficiently decomposed in the absence of an organic acid, ammoniacal nitrogen, or the like that acts as a catalyst.

According to the second aspect of the present invention, since the reaction time required for decomposing dioxin can be secured, the decomposition of dioxin can be promoted. According to the configuration of the third aspect, since the reaction conditions required for the decomposition of dioxin can be secured, the decomposition of dioxin can be promoted.

[0015]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic overall configuration of a sewage treatment facility for treating sewage containing harmful substances such as leachate at a general waste landfill site or an industrial waste landfill site. 31, a calcium removal facility 32, a biological treatment facility 33, a dioxin removal facility 34, and an activated carbon adsorption tower 35.

The pretreatment equipment 31 includes an adjustment tank 36 and a raw water tank 3.
And wastewater 38 such as leachate is supplied to the regulating tank 3.
6 and the raw water tank 37 are successively introduced to alleviate fluctuations in water quality and quantity, and sent to the calcium removal equipment 32 as pretreatment water 39.

The calcium removing equipment 32 includes a reaction tank 40, a flocculation tank 41, a floc forming tank 42, a sedimentation tank 43, and a neutralization tank 44. Pretreatment water 39 is first introduced into the reaction tank 40, Soda 45 is added, whereby the calcium in the pretreatment water 39 aggregates as calcium carbonate. Then, the mixed solution in the reaction tank 40 is sequentially introduced into the coagulation tank 41 and the floc forming tank 42, and an inorganic coagulant 46 such as ferric chloride and a polymer coagulant 47 are added thereto, whereby manganese or the like is added. Heavy metals aggregate. Then, the mixed solution in the floc forming tank 42 is introduced into the sedimentation tank 43, and sedimentation of aggregates of calcium carbonate and heavy metals is separated by sedimentation, and the supernatant water in the sedimentation tank 43 is introduced into the neutralization tank 44. After being combined, it is sent to the biological treatment equipment 33 as coagulated water 48. 49 is caustic soda as a pH adjuster, and 50 is sulfuric acid.

The biological treatment equipment 33 includes an anaerobic tank 51 and an aerobic tank 52, and a membrane separation device 53 is installed inside the aerobic tank 52. The membrane separation device 53 is not shown in the drawing. A plurality of tubular ceramic separation membranes are arranged in a casing formed with a permeated water suction chamber, and arranged inside each separation membrane, that is, a permeated water flow path communicates with the permeated water suction chamber,
Filtration is performed at each separation membrane by applying suction pressure to the permeated water flow path of each separation membrane through the permeated water suction chamber.

In such a configuration, the coagulated water 48 sent from the calcium removal equipment 32 is circulated between the anaerobic tank 51 and the aerobic tank 52 while methanol 54 is added in the anaerobic tank 51. And T-N and BOD
Organic pollutants such as substances are biologically decomposed and removed by microorganisms. At the same time, the mixture of microorganisms in the aerobic tank 52 is filtered by the membrane separation device 53, and suspended matter such as microorganisms remains in the tank 52, and the biologically treated water 5 permeating through the membrane surface.
5 is sent to the biological treatment water tank 56, where the pH is adjusted by the pH adjusting agent 56 a, and then sent to the dioxin removal equipment 34.

The dioxin removal equipment 34 is configured as a combined ultraviolet and ozone type reaction tank. An ultraviolet irradiator 57 is disposed inside, and an ozone generator 58 is disposed outside. Biological treatment water 55
Is introduced into the tank from below and rises. In the meantime, the biologically treated water 55 is 180
UV light in both the ± 50 nm and 250 ± 50 nm regions or UV light in the 300 ± 50 nm region and 80 ± 10 gO ₃ from the ozone generator 58.
/ M ³ , which is in contact with high-concentration ozone and supplied from the upper part of the tank, and part of the ultraviolet / ozone-treated water 59 is circulated to the lower part of the tank to stay in the tank for 30 to 300 minutes. And thereby dioxin and residual COD
Soluble organic pollutants such as substances are efficiently decomposed. Remaining ultraviolet and ozonated water 6 flowing out from the upper part of the tank
0 is sent to the activated carbon adsorption tower 35 via the intermediate treatment tank 61, and the discharged ozone 62 is sent to the discharged ozone decomposing tower (not shown) to be decomposed.

The activated carbon adsorption tower 35 is filled with activated carbon 63, and the ultraviolet / ozone-treated water 60 sent from the intermediate treatment tank 61 flows into the tower from the upper part and is activated carbon 63.
During that time, dioxins and heavy metals remaining in the ultraviolet / ozone-treated water 60 are adsorbed and removed by the activated carbon. The activated carbon treated water 64 flowing out of the activated carbon adsorption tower 35 is taken out as a final treated water 66 through an activated carbon treated water tank 65.

In the membrane separation device 53, the membrane surface is cleaned by a gas-liquid mixed upward flow generated by aerated air during the filtration operation, and a part of the biologically treated water in the biologically treated water tank 56 is appropriately backwashed with water 67. As a result, the water is sent to the membrane separation device 53 in the opposite direction to that during the filtration operation to be backwashed. In order to prevent membrane blockage due to biological slime, sometimes NaCl
O68 is injected.

In the activated carbon adsorption tower 35, part of the activated carbon treated water in the activated carbon treated water tank 65 is backwashed 69 in order to prevent the activated carbon 63 layer from being clogged by fine suspended solids that gradually accumulate. Is introduced from the bottom of the tower together with the air 70, and the backwash water containing suspended solids is discharged out of the tower.

According to the flow as described above,
Of calcium and manganese in the
Since heavy metals are separated, the
CaCO_Three Adhesion of scale and chemical solution using NaClO
MnO after backwashing _Two This prevents adhesion of
Thus, a decrease in permeation flux and membrane blockage due to these factors are prevented.

Further, in the biological treatment equipment 33, the organic acid and the ammonia nitrogen which inhibit the decomposition of dioxin are removed, and the suspended matter is separated by the membrane separation device 53. Is efficiently decomposed.

Table 1 below shows the quality of the raw water and the final treated water, and Table 2 shows the quality of the raw water and the treated water in each of the above-described steps. FIG. 2 is a graph showing the effect of ultraviolet light and ozone concentration on the removal of PCDDs, and FIG. 3 is a graph showing the effect of ultraviolet light and ozone concentration on the removal of PCDFs.

[0027]

[Table 1]

[0028]

[Table 2]

In Tables 1, 2 and 3, DXN represents a dioxin, which means a combination of PCDDs (dioxin) and PCDFs (dibenzofuran).

[0030]

As described above, according to the present invention, calcium and heavy metals such as manganese are separated in the calcium removing equipment, so that even if a membrane separation device is installed, CaCO ₃ can be applied to the membrane surface and the like. It is possible to prevent the adhesion of scale and MnO ₂ , and to prevent the reduction of the permeation flux and the clogging of the membrane.

This makes it possible to apply the membrane separation device to the treatment flow, so that the biological treatment facility can separate not only organic acids and ammoniacal nitrogen that hinder the decomposition of dioxins but also suspended solids. In the dioxin removal equipment, dioxins can be reduced to a drinkable level. In addition, COD substances can be reduced in the biological treatment facility, the dioxin removal facility, and the activated carbon adsorption tower as compared with the related art.

In such a processing flow, since there is no need for a facility for coagulating and solid-liquid separation of biologically treated water, the process and apparatus configuration are simplified, construction costs and maintenance costs are reduced, and maintenance is easy. Can be.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a schematic overall configuration of a sewage treatment facility in which a sewage treatment method according to an embodiment of the present invention is implemented.

FIG. 2 is a graph showing the effect of ultraviolet and ozone concentrations on the removal of PCDDs.

FIG. 3 is a graph showing the effect of ultraviolet and ozone concentrations on PCDF removal.

FIG. 4 is an explanatory diagram showing a schematic overall configuration of a sewage treatment facility in which a conventional sewage treatment method is performed.

[Explanation of symbols]

 32 Calcium removal equipment 33 Biological treatment equipment 34 Dioxin removal equipment 35 Activated carbon adsorption tower 38 Sewage water 39 Pretreatment water 48 Coagulation treatment water 53 Membrane separation equipment 55 Biological treatment water 57 Ultraviolet irradiator 58 Ozone generator 60 Ultraviolet / ozone treated water 64 Activated carbon Treated water 66 Final treated water

Claims (3)

[Claims] 1. A method for treating sewage containing harmful substances, such as leachate from a general waste landfill or an industrial waste landfill, wherein the sewage is introduced into a calcium removal facility,
Heavy metals such as calcium and manganese in sewage are coagulated and precipitated by adding a coagulant and separated, and the coagulated water from which the calcium has been separated is introduced into a biological treatment facility equipped with a membrane separation device. Organic pollutants such as nitrogen and BOD substances are biologically removed by microorganisms, and a suspension such as microorganisms is separated by a membrane separation device at the outlet side of the organic pollutants to separate the organic pollutants and suspended matter. The removed biologically treated water is introduced into an ultraviolet / ozone combined type dioxin removal facility, and dioxins and remaining soluble organic pollutants in the biologically treated water are decomposed by ultraviolet rays and high-concentration ozone, and from the dioxin removal facility. The effluent UV / ozone treated water is introduced into the activated carbon adsorption tower,
A method for treating sewage, wherein dioxin and heavy metals remaining in ozonated water are adsorbed and removed by activated carbon, and activated carbon treated water flowing out from the activated carbon adsorption tower is taken out as final treated water in the system. 2. A residence time in the facility for 30 to 300 minutes is secured by circulating a part of the ultraviolet / ozone treated water flowing out of the dioxin removal facility to the inflow side thereof. Wastewater treatment method. 3. A dioxin removal facility, comprising:
A method of irradiating ultraviolet rays in both the range of ± 50 nm and 250 ± 50 nm, or irradiating ultraviolet rays in the range of 300 ± 50 nm, and supplying ozone so as to be 80 ± 10 gO ₃ / m ^3. The method for treating sewage according to claim 1 or 2.