JPH10137779A - Treating device for leached water from reclamation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve treated water quality and also to enable a highly loaded operation by arranging a flocculating and separating device at the upstream side of an aeration tank. SOLUTION: The flocculating and separating device C consisting of a mixing tank C1 having an agitating means 1i and a liq. chemical feed means 1j, a similar flocculating tank C2 and a flocculating and settling tank C3 is disposed at the upstream side of a membrane separation type activated sludge treating device A having the aeration tank A1 . A settled sludge at the flocculating and settling tank C3 is returned to the mixing tank C1 with a piping P2 . An SS component in a raw water W1 is flocculated and removed, and an SS concn. is reduced till an order of about 20mg/L. An accumulation of the SS component at the post stage aeration tank A1 is prevented by attaining this residual SS concn. A floculant such as aluminum sulfate and a pH adjusting agent such as sodium hydroxide are used at the mixing tank C1 of the flocculating and separating device C. A high-molecular floculant such as nonionic floculant is used at the flocculating tank C2 . In this way, the SS concn. is reduced and BOD components are removed sufficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for treating landfill leachate, and more particularly, to an apparatus for treating landfill leachate that can perform activated sludge treatment at a high load.

[0002]

2. Description of the Related Art Conventionally, a method of treating landfill leachate by using an activated sludge treatment apparatus including an aeration tank and a membrane separation apparatus (hereinafter, referred to as a membrane separation type activated sludge treatment apparatus) has been proposed.

[0003]

However, it has been found that when the landfill leachate is treated by the above-mentioned membrane separation type activated sludge treatment apparatus, low load operation becomes inevitable and causes deterioration of the treatment capacity. did. Specifically, as the operation of the apparatus progresses, the ratio of the volatile component concentration (MLVSS) in the activated sludge to the total activated sludge concentration (MLSS) in the aeration tank (MLVSS / MLSS)
Ratio) was reduced to about 30%, and as a result, the quality of treated water and the treatment capacity of the apparatus were deteriorated.

In order to prevent such a situation from occurring, the MLV
When the apparatus is operated with the SS concentration increased, the MLSS concentration is further increased, the membrane separation performance is deteriorated, and a long-term practical apparatus operation cannot be performed. This situation is due to the fact that the SS concentration of the landfill leachate is much higher than the concentrations of the BOD component and the nitrogen component, and most of the SS components are inorganic SS components.

[0005] Therefore, in this case, the leakage of the SS component to the treated water is completely prevented, and the SS component accumulates in the aeration tank over time and increases. It is an object of the present invention to provide a landfill leachate treatment apparatus that can treat landfill treated water to obtain a high quality of treated water and that can be operated at a higher load.

[0006]

According to the present invention, there is provided an apparatus for treating landfill leachate in an activated sludge treatment apparatus comprising an aeration tank and a membrane separation apparatus. An apparatus for treating landfill leachate, wherein an apparatus for coagulation and separation is disposed upstream of an aeration tank.

In the treatment apparatus of the present invention, since the SS component of the landfill leachate is coagulated and removed in advance by the coagulation / separation treatment apparatus disposed in the preceding stage of the aeration tank, the SS in the treated water after passing through the coagulation / separation treatment apparatus is removed. Since the concentration is decreasing, the problem of the accumulation of the SS component described above is solved during the operation of the aeration tank.
That is, the MLVS in the aeration tank during the operation of the aeration tank
The problem of a decrease in the S / MLSS ratio does not occur, and as a result, high treated water quality and high-load operation of the device can be realized.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a processing apparatus according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a conceptual diagram showing a conventional example of a membrane separation type activated sludge treatment apparatus. Landfill leachate w _1, first, if necessary, sent to the neutralization tank B which stirring means 1a is attached, where, acid and alkali from the chemical supply unit 1b of pH adjusting agent is neutralized is added You. The pH value at this time is preferably set to 6 to 8.

The effluent from the neutralization tank B is then aerated.
Aeration provided with stage 1c, stirring means 1d, and chemical supply means 1e
Tank A₁And the aeration tank A₁Of the membrane located downstream of
Release device A_TwoSeparation activated activated sludge treatment equipment that requires
Sent to the location A. In addition, in the conventional example of FIG.₁
Nitrification tank A provided with aeration means 1f on the downstream side of
_ThreeFinishing with stirring means 1g and chemical liquid supply means 1h
Denitrification tank A_FourAre sequentially arranged, and the finishing denitrification tank A_FourEffluent of
Is a membrane separation device A_TwoTo be sent to Soshi
And membrane separation device A_TwoThe separated sludge generated in₁Through
Aeration tank A ₁It can be returned to.

[0010] The aeration tank A _1, may be a conventional floating activated sludge tank, also, aerobic treatment - may be intermittent aeration tank for performing anaerobic treatment. On the other hand, the membrane separation unit A _2, as shown in FIG. 1, may be one arranged separately outside the aeration tank A _1, also by immersing the membrane separation device in the aeration tank directly provided Immersion type membrane separation device to be used. The type of membrane used is microfiltration (MF)
Membranes, ultrafiltration (UF) membranes and the like.

In the finishing nitrification tank A ₃ shown in FIG. 1, aeration is performed so that the dissolved oxygen becomes a desired amount. In the finishing denitrification tank A ₄ , for example, the ORP potential shows a predetermined value. Methanol is added from the chemical solution supply means 1h. Thus, the continued operation of the processing apparatus shown in FIG. 1, as described above, MLVSS in the aeration tank A ₁ /
The MLSS ratio is lowered, so that low load operation is forced.

In order to address such a problem, the present invention provides the processing apparatus shown in FIG. The processing apparatus shown in FIG. 2 has a coagulation / separation processing apparatus C arranged upstream of the processing apparatus shown in FIG. The coagulation / separation apparatus C comprises a mixing tank C ₁ provided with a stirring means 1 i and a chemical liquid supply means 1 j, a coagulation tank C ₂ provided with a stirring means 1 k and a chemical liquid supply means 11, and a coagulation sedimentation tank C _3. and the C ₁ on the upstream side is constituted by a series arrangement. The precipitated sludge flocculation tank C ₃ is adapted to be returned to the mixing tank C ₁ in the pipe p _2. Although not shown, the coagulating sedimentation tank C
₃ is provided with a means for extracting the settled sludge.

[0013] Examples of the aggregating means for removing SS component in the raw water w _1, may be any means as long as the SS concentration of about 20 mg / L, for example, coagulating sedimentation apparatus and aggregation floatation on Preferably it is a device. As a means for coagulation sedimentation or coagulation pressure flotation, a conventionally known method can be applied. For example, an acid coagulation method (pH 5), a neutral coagulation method (pH 6 to 7), and an alkaline coagulation method (pH 10 to 10)
Any of 11) and the like may be adopted. Moreover, you may change suitably according to the property of raw water.

[0014] In the coagulation and separation apparatus C, SS concentration in the raw water w ₁ is the SS component aggregate removed to reduce to about 20 mg / L. With such a residual SS concentration, the problem of accumulation of the SS component in the subsequent aeration tank does not occur. Specifically, the raw water w ₁ is introduced into the mixing tank C ₁ , where the chemical solution supply means 1 j receives, for example, a sulfuric acid band,
An aggregating agent such as ferric chloride, polyiron and PAC, and a pH adjusting agent such as sodium hydroxide, sodium carbonate and sulfuric acid are added and mixed by the stirring means 1i. Then transferred to a flocculation tank C _2,
Here, after stirring at the stirring means 1k from chemical supply means 1l was added a nonionic or anionic polymeric flocculant, to stand by transferring the flocculation tank C _3. In the coagulating sedimentation tank C _3, SS component in the raw water becomes settled settled sludge, the supernatant is treated water w _2.

In this process, the coagulating sedimentation tank C ₃
As SS concentration in the treated water w ₂ from it becomes less 20 mg / L, the type of flocculant, its amount, pH value employed, such as processing time is selected appropriately. In addition, although it changes depending on the properties of raw water, etc., usually, the mixing tank C ₁ and the coagulation tank C ₂
10-30 minutes residence time in, it is preferable to set the water area load of coagulating sedimentation tank C ₃ to 0.5~1m ³ / m ² / hr.

In the case where an alkaline coagulation method with sodium carbonate added mainly for the purpose of preventing the formation of calcium scale is adopted as the coagulation method, a predetermined amount of the settled sludge in the coagulation settling tank C ₃ is supplied via the pipe p _2. it is preferable to return to the mixing tank C ₁ Te. Thus, the activated sludge mixture after a predetermined time of biochemical processes in the aeration tank A ₁ is performed, then, sent to a membrane separation unit A _2, where it is solid-liquid separation and the treated water w ₃ sludge You.

[0017] Incidentally, as the device operation progresses, the membrane separation in the apparatus A ₂ since separation sludge is gradually increased, the separating sludge at appropriate time intervals is returned to the aeration tank A ₁ by a pipe p _1. Further, if the processing apparatus of the present invention, in the process of the activated sludge mixture produced in the aeration tank A ₁ until membrane separation in the membrane separation device A _2, by supplying a predetermined coagulant and a pH adjusting agent, Further, the COD component can be removed. Chemical supply means 1m therefor may be provided in the aeration tank A _1, may be provided in the membrane separation unit A _2, FIG. 1, as shown in FIG. 2, the person who provided the membrane separation device A ₂ It is suitable.

[0018]

EXAMPLES The treatment apparatus shown in FIG. 1 as a comparative example and FIG. 2 as an example was operated under the following conditions to treat landfill leachate (raw water). The aeration tank A _1, about together and anaerobic step of performing only stirring with aerobic step and aeration agitation means 1d to stop performing aeration from aeration unit 1c 6
An intermittent aeration tank with a 0 minute cycle was used. Aeration tank A ₁ is intermittent aeration tank having an effective volume of 400 L, the effective volume of the finished nitrification tank A ₃ is 40L, the effective volume of the finished denitrification tank A ₃ is 80L. The effective volume of the membrane separation device A ₂ is 12
0 L, the membrane used is made of hydrophilic polyethylene,
It is a hollow fiber MF membrane having a nominal pore size of 0.1 μm.

[0019] The intermittent aeration tank A ₁ was adjusted to 7 and the pH value by adding sulfuric acid or caustic soda from the chemical supply unit 1e,
In the aerobic step, the amount of aeration from the aeration means 1c was controlled so that the DO value was 1.5 to 2.5 mg / L. And the ratio of the processing time of the aerobic process and the anaerobic process was changed within the range of 50 to 90% in accordance with the load change of the raw water. For example, when the total nitrogen concentration (TN concentration) in the raw water is 30 to 60 mg / L, the time ratio of the aerobic step is set to 80%, and the TN concentration is set to 6%.
When the amount is 0 to 120 mg / L, the time ratio of the aerobic step is 5
0 to 70%.

In the anaerobic step, the total nitrogen load required for denitrification in the first 5 minutes after the start of the anaerobic step is 2.5 to 2.5.
Three times the amount of methanol was added from the chemical solution supply means 1e.
After performing the biochemical treatment by operating the intermittent aeration tank under the above conditions, the obtained activated sludge mixed liquid is sequentially transferred to the finishing nitrification tank A ₃ and the finishing denitrification tank A ₄ , and further successively, the membrane separation device. It was introduced to a _2.

[0021] carried out aeration in the aeration unit 1f as DO value is 2 mg / L or more in the finish nitrification tank A ₃ in the activated sludge mixture and the finished denitrification tank A _4, the ORP potential of the activated sludge mixture 0 Methanol was added from the chemical liquid supply means 1 h so as to show a value of −? 100 mV, and the mixture was stirred with 1 g of stirring means. The amount of methanol was varied within the range of 0 to 80 mg / L corresponding to the load variation of the raw water.

The effective pressure of the membrane separation device A ₂ is ^{3 to} 40 kPa so that the flux becomes 0.3 m ³ / m ² / day.
, An intermittent operation of filtering for 8 minutes and resting for 2 minutes was performed. In addition, from the lower part of the MF membrane, the cross-sectional area of the empty space of the filtration unit is 1 m ^2.
Aeration was performed at an air flow rate of 70 to 130 Nm ³ / hr per hour to prevent the activated sludge from concentrating and adhering to the membrane surface.

[0023] Then, the membrane separation apparatus A ₂ by the addition of sulfuric acid from the chemical supply unit 1 m, pH value of the activated sludge mixture which has been transferred thereto was adjusted to 6.0 to 6.3 .
Further, from the membrane separation unit A ₂ and returning the sludge to the intermittent aeration tank A _1. The return flow rate at this time was set to 2 to 4 times the raw water flow rate. Further, the intermittent aeration tank A ₁ of the sludge residence time (S
(RT) was 25 to 35 days, and a sludge withdrawing means was provided (not shown), and sludge was withdrawn.

The activated sludge mixed solution of this membrane separation device is added with ferric chloride by 10 m from the chemical solution supply means to the raw water.
A COD component removal test in raw water was also performed by adding 0 to 250 mg / L. Furthermore, the coagulation and separation processing unit C, to the raw water w _1, acidic coagulation method, a neutral aggregation method, alkaline agglutination method, and was treated by applying the sodium carbonate added alkaline agglutination method. In either case, SS concentration in the treated water w ₂ is 20mg / L
It was possible to: Among the applied aggregation method, in the former three, mixing tank C ₁ ferric chloride using 50 to 150 mg / L to the raw water in, 1 to 5 mg to raw water flocculation tank C ₂ in polymeric flocculant / L used. The type and amount of the polymer coagulant were examined each time the coagulation conditions were changed, and the polymer coagulant was selected so that the removal of the SS component proceeded favorably.

Further, when applying sodium carbonate added alkaline aggregation method, it was added 1500 mg / L to the raw water of sodium carbonate in admixture tank C _1. Further, at this time, subjected to generation preventive treatment of calcium scale in coagulation and separation processing apparatus C to return the settled sludge to the mixing tank C ₁ from the coagulating sedimentation tank C _3. The returned sludge was 0.5 to 2 times the raw water flow rate.

Next, the treated water w ₂ is transferred to the neutralization tank B,
Therefore, we introduced the intermittent aeration tank A ₁ After the pH was adjusted to 7 values with sulfuric acid or caustic soda. As a comparative example, as shown in FIG. 1, without placing the coagulation and separation processing apparatus, the raw water w _1, directly introduced into the membrane separation type activated sludge device A in the operating conditions described above, intermittent aeration MLSS concentration in the bath a _1, MLVSS concentration was measured, respectively, it was also determined, respectively BOD volume load and TN volume load per aerobic step.

[0027] As the second embodiment, as shown in FIG. 2 performs the operation in the above conditions and placing the coagulation and separation processing apparatus C, MLSS concentration in the intermittent aeration tank A _1, MLVs
The S concentration was measured separately and the BOD per aerobic step
Volume load and TN volume load were determined respectively. Table 1 shows the above results.

[0028]

[Table 1] In each of the comparative examples and examples, good treated water quality could be obtained. However, in the case of the comparative example, the water flow rate was 3
It was necessary to keep it below 00L / day.

Therefore, in the comparative example, the MLVSS concentration in the intermittent aeration tank was set to about 100
When the device was operated to be 00 mg / L, the MLS
The S concentration increases to about 38000 mg / L, and solid-liquid separation of the activated sludge mixture becomes extremely difficult with the membrane separation device.
Practical equipment operation has become difficult. In the case of such a high load condition, it is preferable to provide an aggregating / separating apparatus in front as in the embodiment.

As is clear from Table 1, in the case of the comparative example, the MLVSS / MLSS ratio in the intermittent aeration tank was 30.
%, And the MLVSS concentration at this time shows a low value of 4000 mg / L, but in the case of the example, the MLVSS / MLSS ratio in the intermittent aeration tank shows a value of 80%, and the MLVSS concentration at this time To 11,000 mg / L. This is because, in the embodiment, the in previous stage of applying the raw water w ₁ to the membrane separation type activated sludge treatment apparatus A, was reduced so that concentration of SS components in the raw water w ₁ aggregate removed by coagulation and separation processing apparatus C It is.

Further, in the treatment apparatus of the embodiment, both the BOD volume load and the TN volume load of the intermittent aeration tank are high, and the raw water w
Treated ₁ at a high load can be treated water w ₃ of high quality level, it is possible to significantly reduce the size of the apparatus. The properties of the treated water w ₃ obtained in Example, raw water w _1, shown in Table 2 together with properties of treated water w _2.

[0032]

[Table 2]

[0033] As is apparent from Table 2, by pretreatment with coagulation and separation processing unit C, the raw water SS component of w ₁ is greatly aggregate removal, SS concentration in the resulting treated water w ₂ are 20 mg / L Reduce to below. And this treated water w ₂
Treated water w _{3 which} has been subjected to membrane separation type activated sludge treatment to SS
It has low concentration and is clean treated water from which BOD components and nitrogen components have been sufficiently removed. The COD _Mn of the treated water when ferric chloride was supplied from 1 m of the chemical supply means was 20.
-30 mg / L, which is more preferable.

[0034]

As is apparent from the above description, the treatment apparatus of the present invention can make landfill leachate a highly treated water quality. The treatment apparatus of the present invention uses a coagulation separation treatment apparatus to coagulate and remove inorganic SS components, which are main components among the SS components in landfill leachate, and then performs membrane separation type activated sludge on the landfill leachate. Since the treatment is performed using the treatment device, the MLVSS / MLSS ratio in the aeration tank is increased, and the MLVSS / MLSS ratio is increased.
High load operation with an increased SS concentration can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a conventional example of a membrane separation type activated sludge treatment apparatus.

FIG. 2 is a schematic view showing one embodiment of the processing apparatus of the present invention.

[Explanation of symbols]

A Membrane separation type activated sludge treatment equipment A ₁ Aeration tank A ₂ Membrane separation equipment A ₃ Finish nitrification tank A ₄ Finish vaginal removal tank B Neutralization tank C Coagulation separation treatment apparatus C ₁ Mixing tank C ₂ Coagulation tank C ₃ Coagulation sedimentation tank 1a, 1d, 1g, 1i, 1k Stirring means 1b, 1e, 1h, 1j, 1l, 1m Chemical liquid supply means 1c, 1f Aeration means

Claims (1)

[Claims] 1. An apparatus for treating landfill leachate by an activated sludge treatment apparatus comprising an aeration tank and a membrane separation apparatus, wherein an agglomeration separation treatment apparatus is disposed upstream of the aeration tank. Landfill leachate treatment equipment.