JP5063975B2 - Organic wastewater treatment method and treatment apparatus - Google Patents

Description

  TECHNICAL FIELD The present invention relates to an organic wastewater treatment technique, and more particularly to an effective treatment method and treatment apparatus for organic wastewater containing organic refractory organic matter such as dewatered separation liquid of sewage digested sludge and containing ammonia nitrogen. .

  In general, raw water such as sewage containing organic substances is treated by a wastewater treatment facility consisting of a first sedimentation tank (first sedimentation tank), a biological treatment tank (for example, activated sludge treatment tank) and a final sedimentation tank (final sedimentation tank). An anaerobic digestion process of the excess sludge generated in the settling basin and the raw sludge generated in the first settling basin, and then returning the dewatered separation liquid separated by dehydrating the digested sludge to the entry side of the wastewater treatment facility The method is adopted.

  However, since the dehydrated separation liquid contains a hardly decomposable organic substance, when the dehydrated separation liquid is returned to the entry side (raw water inflow side) of the wastewater treatment facility, it is discharged from the final sedimentation basin of the wastewater treatment facility. There is a possibility that the quality of treated water cannot be maintained well. In particular, when a solubilization treatment such as a heat treatment is performed before the anaerobic digestion treatment, the amount of the hardly decomposable organic matter increases, so that it is difficult to secure good treated water.

In order to solve this problem, it has been studied to apply some treatment to the dehydrated separation liquid and then return it to the wastewater treatment facility (see Patent Document 1). However, the biological treatment such as the activated sludge method cannot sufficiently remove the hardly decomposable organic matter. Also, physicochemical treatments such as ozone oxidation, activated carbon adsorption, and electrolysis are effective for removing persistent organic substances, but they require a lot of utilities such as electric power and chemicals, and are very expensive. is there.
Japanese Patent Laid-Open No. 2004-97903

  The present invention solves such conventional problems and is intended for the treatment of organic wastewater containing persistent organic substances and ammonia nitrogen, and in particular in the dewatered separation liquid of organic sludge generated from wastewater treatment equipment. It is an object of the present invention to provide a method for treating organic wastewater that can efficiently reduce COD components containing persistent organic substances at low cost.

  And the structure made into the summary of this invention completed in order to achieve the said subject is as follows.

The structure which makes the summary of the dehydration processing method of the sludge of this invention completed for achieving the said subject is as follows.
(1) In the method for treating wastewater containing biologically indegradable organic matter and ammoniacal nitrogen, organic sludge is subjected to anaerobic digestion, and the digested sludge after the digestion is dehydrated and separated from the wastewater. The solution is subjected to biological nitrification to lower its pH, and then the nitrification solution after nitrification is subjected to solid-liquid separation to separate solids in the treatment solution, and then the solids are separated. A pH adjusting agent is added to the nitrification treatment liquid to lower the pH of the nitrification treatment liquid, and an iron-based flocculant is added to the nitrification treatment liquid whose pH has been lowered to agglomerate the organic matter in the treatment liquid. A method for treating organic waste water, comprising subjecting the agglomeration treatment liquid to solid-liquid separation to separate agglomerated organic matter in the agglomeration treatment liquid. (Claim 1).
(2) The method for treating organic waste water according to (1) above, wherein the biological nitrification treatment is performed to lower the pH to 7 or less (claim 2).
(3) The method for treating organic waste water according to claim 1, wherein the biological nitrification treatment is performed to lower the pH to 6.5 or lower (claim 3).
(4) The organic wastewater treatment method as described in (1) above, wherein the nitrification solution is subjected to solid-liquid separation using a membrane.
(5) The method for treating organic wastewater according to any one of (1) to (4) above, wherein when the flocculant is added to the nitrification treatment liquid, the nitrification treatment liquid is mixed. .
(6) In a wastewater treatment device containing biologically indegradable organic matter and ammonia nitrogen, a digester for anaerobically digesting organic sludge, a dehydrator for dewatering the digested sludge after the digestion, and a dehydration treatment the nitrification treatment tank to reduce the pH of the waste water in a dehydration separated liquid was treated biological nitrification, and solid-liquid separator for nitrifying liquid to solid-liquid separation which is nitrified after, after the solid-liquid separation And a flocculation treatment tank for aggregating the nitrification liquid whose pH has been lowered by the pH adjuster with an iron-based aggregating agent, and an agglomerate separation apparatus for separating the agglomerated flocculated separation liquid into an agglomerate and a treatment liquid. An organic wastewater treatment apparatus (claim 6).
(7) The organic waste water treatment apparatus as described in (6) above, wherein the solid-liquid separation apparatus is a membrane separation apparatus (Claim 7).

  (2) In the method for treating waste water containing persistent organic matter and ammonia nitrogen, the waste water is subjected to biological nitrification treatment to lower its pH, and then solidified into the nitrification treatment solution after the nitrification treatment. Separation is performed to separate solids in the treatment liquid, and then a flocculant is added to the nitrification treatment liquid from which the solids have been separated to agglomerate the organic matter in the treatment liquid. A method for treating an organic wastewater, characterized in that solid-liquid separation is performed to separate agglomerated organic matter in the agglomeration treatment liquid (Claim 2).

  (3) The method for treating organic wastewater as described in 1 or 2 above, wherein the biological nitrification treatment is carried out to lower the pH to 7 or less (claim 3).

  (4) The method for treating organic waste water according to claim 1 or 2, wherein the biological nitrification treatment is performed to lower the pH to 6.5 or less (claim 4).

  (5) The method for treating organic waste water according to (2) above, wherein the nitrification solution is subjected to solid-liquid separation using a membrane.

  (6) The organic wastewater treatment method according to any one of (1) to (5) above, wherein the flocculant is an iron-based flocculant.

  (7) The method for treating organic waste water according to any one of (1) to (6) above, wherein the nitrification solution is subjected to a mixing treatment when a flocculant is added to the nitrification solution (Claim 7). .

  (8) In a wastewater treatment apparatus containing a hardly decomposable organic substance and ammonia nitrogen, a nitrification tank for biologically nitrifying the wastewater to lower its pH, and a biological nitrification-treated nitrification solution An organic wastewater treatment apparatus comprising: an aggregating treatment tank for aggregating with an aggregating agent; and an agglomerate separating apparatus for separating the agglomerated and separated agglomerated separation liquid into an agglomerate and a treatment liquid (claim 8). .

 (9) In a wastewater treatment apparatus containing a hardly decomposable organic substance and ammonia nitrogen, the wastewater biological nitrification treatment reduces the pH of the wastewater treatment tank, and the nitrification treatment nitrification solution is solid-liquid separated. It comprises a solid-liquid separation device, an agglomeration treatment tank for aggregating the nitrified liquid that has been solid-liquid separated with an aggregating agent, and an agglomerate separation device for separating the agglomerated agglomerated separation liquid into an agglomerate and a treatment liquid. An organic wastewater treatment apparatus characterized by the above (claim 9).

 (10) The organic waste water treatment apparatus as described in (9) above, wherein the solid-liquid separation device is a membrane separation device (claim 10).

  According to the present invention, for the treatment of organic wastewater containing persistent organic matter and ammonia nitrogen, the biologically degradable substance in the dehydrated separation liquid of organic sludge generated from wastewater treatment equipment is used. Organic substances (COD components) contained can be effectively removed and reduced by agglomeration treatment. In addition, the aggregating agent and pH adjusting agent necessary for the aggregating treatment can be used in a very small amount, and the running cost can be reduced. Furthermore, the apparatus and equipment can be handled with a compact configuration, and the initial cost can be reduced.

  Hereinafter, the present invention will be described with reference to the drawings focusing on typical embodiments thereof.

  FIG. 1 is a process flow diagram showing an embodiment of the present invention. In FIG. 1, the dehydrated separation liquid A is a wastewater treatment facility shown in FIG. 3 (generally, a first sedimentation tank 11, a biological treatment tank 12, and a final sedimentation tank). And a sludge treatment facility (for example, comprising a high concentration concentrator 14, a hydrolysis device 15, a digester 16 and a dehydrator 17) for reducing the volume of organic sludge generated from the wastewater treatment facility. The separation liquid after dewatering of organic sludge is shown. The dehydrated separation liquid A is processed by a separation liquid processing apparatus 18 described later.

  This dehydration separation liquid A usually has a pH of 7.5 to 8.8 when the hydrolysis apparatus is subjected to high-temperature and high-pressure treatment (input sludge concentration of 10 to 15%, temperature of 120 to 200 ° C., pressure of 0.1 to 1.5 MPa). It is about 5, and the supernatant COD Mn containing a hardly decomposable organic substance is contained in an amount of about 1000 to 1500 mg / L, and ammoniacal nitrogen is contained in an amount of about 1500 to 2500 mg / L.

  In the present invention, this dehydrated separation liquid A is treated as an organic wastewater in a separation liquid processing apparatus 18 comprising a nitrification tank 1, a solid-liquid separation means (solid-liquid separation apparatus) 4, a mixing tank 5 and an agglomerate separation apparatus 7. . First, the dehydrated separation liquid A is guided to the nitrification tank 1, where biological nitrification treatment (hereinafter simply referred to as nitrification or nitrification treatment) is performed. Hereinafter, it is preferably converted to a liquid (nitrification liquid) of 6.5 or less. In order to promote this nitrification treatment in the nitrification tank 1, an aeration device 2 is installed at the bottom of the nitrification tank so that air 3 is supplied to the apparatus from the outside so that the liquid in the nitrification tank can be stirred by bubbling. It is configured. In the same nitrification tank 1, an immersion membrane (hollow fiber membrane, flat membrane, etc.) is disposed as a solid-liquid separation means (solid-liquid separation device) 4 at a position opposite to the supply side of the dehydrated separation liquid A. It is installed.

  This nitrification treatment is performed using well-known nitrifying bacteria (nitrite bacteria and nitrate bacteria). The dehydrated separation liquid A guided to the nitrification tank 1 is stirred by the air diffuser 2 and the ammonia nitrogen in the liquid is aerobically oxidized by the nitrifying bacteria, and the following equations (1) and (2) The nitrification reaction proceeds. Further, when the formula (1) and the formula (2) are combined, the formula (3) is obtained.

NH ₄ ⁺ 3/2 O ₂ → NO ₂ ⁻ + H ₂ O + 2H ⁺ (1)
NO ₂ ⁻ +1/2 O ₂ → NO ₃ ⁻ (2)
NH ₄ ⁺ + 2O ₂ → NO ₃ ⁻ + H ₂ O + 2H ⁺ (3)
As described above, as a result of nitrification by the nitrification treatment, the dehydrated separation liquid produces H ⁺ and its pH is lowered to the above value.

  Moreover, some organic substances that are easily decomposed are also decomposed by the nitrification treatment.

  Next, the dehydrated separation liquid (nitrification liquid) that has been nitrified is passed through the immersion membrane 4 to remove solids that could not be separated during the dehydration separation in the previous step and organic substances (for example, nitrifying bacteria) decomposed and produced by nitrification. Solid-liquid separation. Thereby, the usage-amount of the coagulant | flocculant in the next coagulation process process can be reduced.

  Then, the solidified liquid-separated nitrification liquid (B) is supplied to the mixing tank 5 (flocculation treatment tank), and in this mixing tank 5, an iron-based flocculant such as ferric chloride and ferric sulfate ( The acidic flocculant 6) is added to the nitrification solution, and the nitrification solution is agglomerated while rotating the impeller provided in the tank.

  Since the pH of the nitrification solution has already been lowered by the nitrification treatment in the previous step due to the flocculation treatment in this mixing tank 5, the flocculation action of the iron-based flocculant 6 is effectively exhibited, and the hard decomposition contained in the liquid is reduced. The agglomerated organic material is effectively a flocified organic material. Here, even when the pH of the dehydrated separation liquid A is originally high, even if the pH is lowered by nitrification treatment, for example, the pH value does not reach 7 or less, and the action of iron-based flocculant, that is, acidic aggregation is exerted. When it is assumed that the pH is insufficient, a necessary amount of a pH adjusting agent such as sulfuric acid is added as appropriate, and the pH value of the nitrification solution is further lowered and adjusted so as to be within an appropriate range. Even when such a pH adjuster is added, the pH of the nitrification solution is relatively lower than that of the nitrification treatment. Therefore, the necessary amount of the pH adjuster is the same as when the coagulation treatment is performed without nitrification treatment. It is less and it is economically advantageous.

  Finally, the flocculated separation liquid C that has been subjected to the flocculation process in the mixing tank 5 is sent to a belt concentrator 7 that is a flocculate separator, and solid-liquid separation is performed to obtain a treatment liquid D and flocculated sludge E. By this solid-liquid separation, the biologically difficult-to-decompose organic matter in the flocculated separation liquid C is separated as the aggregated organic matter, so that the obtained treatment liquid becomes a clean liquid with a significantly reduced concentration of the biologically-degradable organic matter. The agglomerated sludge E is returned to the front of the dehydrator from which the dehydrated separation liquid A is generated, and is further dehydrated and concentrated together with the digested sludge.

  The treatment liquid D thus obtained is returned to the water treatment system (waste water treatment facility). Although the nitrogen component remains in the treatment liquid C, there is no particular problem because it can be sufficiently handled by the water treatment system.

  According to the embodiment of the present invention, organic wastewater such as a dehydrated separation liquid containing a hardly decomposable organic substance and having a high pH by combining nitrification treatment, aggregation treatment and solid-liquid separation as described above. However, the COD component containing the hardly decomposable organic substance can be effectively separated and removed with a small amount of the flocculant used. Further, even when a pH adjusting agent is required, the amount of use can be minimized. The apparatus and equipment for separation and removal can be handled with a very compact structure. Therefore, the initial cost and the running cost are both kept low, and it has an excellent advantage that the hardly decomposable organic substance can be separated and removed.

  In the above embodiment of the present invention, solids (organic matter) in the nitrification liquid nitrified in the nitrification tank 1 are solid-liquid separated by the immersion film 4 provided in the tank, but the immersion film 4 is not used and nitrification is performed. The nitrification liquid B that has undergone the treatment may be supplied to a solid-liquid separation device such as a precipitation tank or a centrifugal concentrator to perform solid-liquid separation.

  Further, in the embodiment of the present invention, the iron-based flocculant 6 is added in the mixing tank 5 when the nitrification liquid B is agglomerated, but it is added in advance to the supply line of the nitrification liquid B to the mixing tank 5. Anyway.

  Furthermore, in the embodiment of the present invention, the aggregated liquid C was separated from the aggregated liquid (aggregated sludge E) using the belt concentrator 7 to finally obtain the treatment liquid D. Solids and liquids may be separated into an agglomerate and a treatment liquid using another agglomerate separator such as a screw press or a rotary pressure dehydrator.

  Hereinafter, an example is given and the outstanding effect of the present invention is clarified.

(Example)
As shown in the processing flow shown in FIG. 2, sewage digested sludge dehydrated separation liquid (pH: 8.1) is the target, and after nitrification in a nitrification tank (effective volume: 4 L), a precipitation tank (effective volume: 4) L), solid-liquid separation is performed, sulfuric acid is added to the supernatant nitrification liquid (pH: 6.5) taken out from the precipitation tank, and the pH is lowered to 6 and adjusted, and then the coagulation treatment tank (effective volume:
0.2 L), 2.5 g of ferric chloride solution (flocculating agent) having the following concentration was added and 1 L of nitrification solution was added for aggregation treatment, and then the supernatant was taken out as a treatment solution. The sedimentation sludge in the sedimentation tank was returned to the nitrification tank at any time and circulated.

  The treatment conditions are as follows: the residence time of the dehydrated separation liquid in the nitrification tank is 5 days, the sludge concentration in the nitrification tank is 5,000 mg / L, and the ferric chloride concentration is 38% (W / V). Using.

  For comparison, a method (comparative example) was also performed in which the same dehydrated separation solution stock was subjected to direct agglomeration treatment without nitrification treatment with the same volume and treatment conditions. The addition amount of the ferric chloride solution (flocculating agent) having the above-mentioned concentration was 2.5 g / l of the treated separation liquid in the same amount as in the example.

  Table 1 shows the components of each solution, the measured values of pH, and the amount of sulfuric acid (pH adjusting agent) used in these Examples and Comparative Examples.

この表から明らかなように、いずれも難分解性有機物を含むCOD成分が有効に除去されているが、比較例では硫酸の使用量が5.7 [g/L] であるのに対し、本発明の実施例の場合はその使用量がわずか0.3 [g/L] で済み、その使用量が比較例と比べ大幅に減少していることがわかる。このように、本発明によれば簡易な装置、設備構成により、非常に低い薬剤の使用コストで確実に難分解性有機物を除去、低減し、脱水分離液などの有機性排水を効率的に清浄化することができるのである。

As is clear from this table, the COD component containing the hardly-decomposable organic substance was effectively removed in all cases, but in the comparative example, the amount of sulfuric acid used was 5.7 [g / L], whereas in the present invention, In the case of the example, the amount used is only 0.3 [g / L], and it can be seen that the amount used is greatly reduced compared to the comparative example. As described above, according to the present invention, a simple apparatus and equipment configuration reliably removes and reduces difficult-to-decompose organic substances at a very low use cost of chemicals, and efficiently cleans organic wastewater such as dehydrated separation liquid. It can be made.

It is a processing flow figure of organic drainage explaining an embodiment of the present invention. It is a processing flow figure of organic drainage explaining the example of the present invention. It is a processing flow figure of waste water treatment equipment explaining an embodiment of the present invention.

Explanation of symbols

1: Nitrification tank 2: Air diffuser 3: Air 4: Immersion membrane (solid-liquid separation means)
5: Mixing tank (flocculation treatment tank) 6: Flocculant 7: Belt concentrator
A: Dehydrated separation liquid B: Nitrification liquid C: Aggregation separation liquid D: Treatment liquid E: Aggregation sludge

Claims (7)

  In the treatment method of wastewater containing biologically indegradable organic matter and ammonia nitrogen, the organic sludge is subjected to anaerobic digestion treatment, and the digested sludge after the digestion treatment is dehydrated and separated into the dewatered separation liquid which is the wastewater. The nitrification treatment liquid which reduced the pH by performing a chemical nitrification treatment, then separated the solid in the treatment liquid by subjecting the nitrification treatment liquid after the nitrification treatment to solid-liquid separation, and then separated the solid matter A pH adjuster is added to the nitrification solution to lower the pH, and an iron-based flocculant is added to the reduced nitrification solution to agglomerate the organic matter in the treatment solution, and the agglomeration treatment A method for treating organic waste water, comprising subjecting the agglomeration treatment liquid to solid-liquid separation to separate agglomerated organic matter in the agglomeration treatment liquid.   The method for treating organic waste water according to claim 1, wherein the biological nitrification treatment is performed to lower the pH to 7 or less.   The method for treating organic waste water according to claim 1, wherein the biological nitrification treatment is performed to lower the pH to 6.5 or lower.   2. The organic wastewater treatment method according to claim 1, wherein the nitrification solution is subjected to solid-liquid separation using a membrane.   The method for treating organic waste water according to any one of claims 1 to 4, wherein when the flocculant is added to the nitrification treatment liquid, the nitrification treatment liquid is mixed. In a wastewater treatment apparatus containing biologically indegradable organic matter and ammonia nitrogen, a digester that anaerobically digests organic sludge, a dehydrator that dehydrates the digested sludge after the digestion, and the dehydrated treatment A nitrification tank that lowers the pH by biologically nitrifying the dehydrated separation liquid that is wastewater, a solid-liquid separation device that separates the nitrified nitrification liquid into a solid and liquid, and adjusting the pH after the solid-liquid separation An agglomeration treatment tank for aggregating the nitrification liquid whose pH has been lowered by the agent with an iron-based aggregating agent, and an agglomerate separator for separating the agglomerated agglomerated separation liquid into an agglomerate and a treatment liquid. Organic wastewater treatment equipment.   The organic waste water treatment apparatus according to claim 6, wherein the solid-liquid separation apparatus is a membrane separation apparatus.

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