JP6367085B2 - Method and apparatus for phosphorus recovery and scale generation prevention in organic wastewater treatment - Google Patents

Description

  The present invention relates to a method and apparatus for preventing phosphorus recovery and scale generation in organic wastewater treatment, and more particularly, to a method and apparatus for preventing scale generation in an effluent pipe from a phosphorus recovery apparatus in organic wastewater treatment.

  In the process of organic wastewater treatment such as manure, sewage, industrial wastewater, etc., as a useful phosphorus recovery method, particulate hardly soluble salts that become seed crystals such as calcium phosphate and hydroxyapatite are added, and this hardly soluble salt is added. A crystallization technique for removing phosphate as hydroxyapatite (hereinafter referred to as “HAP”) by adhering a phosphate compound to the surface, and magnesium ammonium phosphate (hereinafter referred to as “MAP”) by adding magnesium phosphate and alkali. For example, a crystallization technique for removing soluble phosphorus from water is used. The MAP recovery device or HAP recovery device recovers MAP or HAP from the bottom of the MAP reaction tank or HAP reaction tank that forms a MAP or HAP by adding a hardly soluble salt to the water to be treated, and phosphorus as a hardly soluble salt. The supernatant water from which the water has been removed is configured to flow out from the upper part of the MAP reaction tank or the HAP reaction tank. However, since unreacted calcium phosphate and magnesium phosphate remain in the supernatant water and are discharged, they combine with carbonate ions, sulfate ions, phosphate ions, etc. in the water to be treated in the outflow pipe to form a scale, Alternatively, there is a problem that MAP or HAP flows out along with the supernatant water and blocks the outflow pipe.

  On the other hand, in order to prevent the generation of scale in water treatment facilities, a method of adding a scale inhibitor or a scale cleaner is used. The scale inhibitor is an agent that prevents the formation of a hardly soluble salt, and the scale detergent is an agent that dissolves the hardly soluble salt. In any case, since the formation of the hardly soluble salt is inhibited, it is difficult to effectively use it, contrary to the purpose of forming the hardly soluble salt in the MAP recovery device or the HAP recovery device.

The scale prevention methods in organic wastewater treatment that have been proposed so far include MAP formation for phosphorus recovery, such as a method of inhibiting the formation of MAP by adjusting the pH of the water to be treated to be acidic (Patent Document 1). Is a conflicting method. In the denitrification process in the subdigestion tank after phosphorus recovery, a method of suppressing MAP formation by setting the concentration product of phosphoric acid, ammoniacal nitrogen, and magnesium in the water to be treated to 8 × 10 ⁻⁸ or less (Patent Document 2) is also proposed. However, it is necessary to remove the phosphate component as iron phosphate by adding a flocculant in the rapid agglomeration and mixing tank before the effluent after phosphorus recovery flows into the subdigestion tank. Further, MAP formation in the denitrification tank is prevented by removing the phosphoric acid component, but no consideration is given to scales such as calcium carbonate and magnesium carbonate on the inner wall of the pipe.

Japanese Unexamined Patent Publication No. 2006-087986 JP 2010-000479 A

  An object of the present invention is to provide a method and apparatus for collecting phosphorus in an organic wastewater treatment process such as manure, sewage, industrial wastewater and the like, and preventing scale generation on the inner wall of a pipe for sending supernatant water from the phosphorus collection device. It is to provide.

  More specifically, in the organic wastewater treatment process, MAP or HAP is actively formed to recover phosphorus as a hardly soluble salt, and the difficulty in the inner wall of the pipe that feeds the water to be treated after the recovery of phosphorus. It is an object of the present invention to provide a method and apparatus for preventing precipitation of soluble salts.

  Another object of the present invention is to provide the above-described method and apparatus that are effective even when the water to be treated after phosphorus recovery is recycled to a phosphorus recovery apparatus or a magnesium chloride dissolution tank (in the case of MAP).

As a result of diligent research to satisfy the above conflicting requirements, the present inventors added a scale dispersant to the effluent from the phosphorus recovery facility to the inner wall of the piping from the phosphorus recovery facility to the piping. It has been found that scale adhesion can be prevented, and the present invention has been completed. According to the present invention, the following aspects are provided.
[1] A method for preventing phosphorus recovery and scale generation in organic wastewater treatment, comprising adding a scale dispersant to a supernatant water discharge part of a hardly soluble phosphate forming reaction tank in an organic wastewater treatment facility.
[2] The phosphorus recovery and scale generation prevention method according to [1], wherein the addition amount of the scale dispersant is less than 20 mg / L.
[3] An organic wastewater treatment facility characterized in that means for adding a scale dispersant is provided in the supernatant water discharge part of a hardly soluble phosphate forming reaction tank in an organic wastewater treatment facility.
[4] A treated water tank that receives the supernatant water from the hardly soluble phosphate forming reaction tank, a separation liquid tank that mixes the supernatant water and the dehydrated separation liquid, and at least a part of the supernatant water, It further comprises one or more tanks selected from a magnesium source dissolution tank that supplies a magnesium source to a poorly soluble phosphate formation reaction tank or a calcium source dissolution tank that supplies a calcium source, and is added to the selected one or more tanks The organic waste water treatment facility according to [3], wherein means for adding the scale dispersant is provided.

  ADVANTAGE OF THE INVENTION According to this invention, in organic wastewater treatment processes, such as manure, sewage, and industrial wastewater, while collecting phosphorus, the scale generation | occurrence | production in the pipe inner wall which sends supernatant water from a phosphorus collection | recovery apparatus can be prevented.

  More specifically, in the organic wastewater treatment process, MAP or HAP is actively formed to recover phosphorus as a hardly soluble salt, and the difficulty in the inner wall of the pipe that feeds the water to be treated after the recovery of phosphorus. Precipitation of soluble salts can be prevented. In particular, when MAP or HAP flows along with the supernatant water after phosphorus recovery, adhesion of MAP or HAP to the inner wall of the pipe can be prevented.

  Further, the method and apparatus of the present invention can recover phosphorus by forming a hardly soluble salt in the phosphorus recovery apparatus even when the water to be treated after phosphorus recovery is recycled to the phosphorus recovery apparatus and reused. And precipitation of the hardly soluble salt to the inner wall of the outflow piping from a phosphorus collection | recovery apparatus can be prevented.

It is a schematic explanatory drawing of the processing flow of the manure and septic tank sludge which is a typical example which can apply the method and apparatus of this invention. It is a schematic explanatory drawing of phosphorus collection | recovery equipment. It is a schematic explanatory drawing which shows another embodiment of this invention. It is a schematic explanatory drawing which shows another embodiment of this invention. It is a schematic explanatory drawing which shows another embodiment of this invention. It is a schematic explanatory drawing which shows another embodiment of this invention. It is a graph which shows the relationship between the amount of scale dispersant addition by an Example, and the liquid level rise in a reaction tank.

Preferred embodiment

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited thereto.

  FIG. 1 is a schematic diagram of a treatment flow of manure / septic tank sludge which is a typical example to which the method and apparatus of the present invention can be applied.

  In FIG. 1, the urine / septic tank sludge is separated into dehydrated sludge and water to be treated by the dehydration equipment 2. At least a part of the water to be treated is sent to the phosphorus recovery facility 3, and after phosphorus is recovered as MAP, it is sent to the biological treatment facility 4. The treated water biologically treated in the biological treatment facility 4 is filtered through the coagulation sedimentation-sand filtration or membrane separation-activated carbon facility 5 and then discharged through the disinfection facility 6.

  FIG. 2 shows an outline of the phosphorus recovery facility 3. In the phosphorus recovery facility 3, a MAP reaction is carried out to form a hardly soluble MAP by adding a particulate hardly soluble salt as a seed crystal to the water to be treated, and recovering the hardly soluble MAP obtained from the bottom. The tank 30 and the outflow piping 31 for sending the process target water from which soluble phosphorus was removed to the biological treatment equipment 4 are provided. The MAP reaction tank 30 is provided with an overflow weir 33 for allowing the supernatant water to overflow and introducing it into the outflow pipe 31 or the outflow trough (ronder or trough) 32. An air lift separator 30 a is provided on the upper part of the MAP reaction tank 30. The air lift separator 30a is configured to air lift agitate the formed MAP particles and prevent the MAP particles from flowing out into the supernatant water. However, the MAP particles cannot be completely prevented from flowing out into the supernatant water, and the minute MAP particles flow out together with the supernatant water.

  In the case of the phosphorus recovery facility in FIG. 2, a scale dispersant is added to the overflow weir 33 or spillage 32 which is the supernatant water discharge part of the hardly soluble salt forming reaction tank. Furthermore, you may add a scale dispersing agent to the arbitrary positions of the outflow piping 31. FIG.

  FIG. 3 shows an embodiment in which a treated water tank 7 for storing the effluent water from the MAP reaction tank 30 before supplying it to the biological treatment facility 4 is provided at the subsequent stage of the MAP reaction tank 30. In the case of the embodiment shown in FIG. 3, a scale dispersant may be added to the treated water tank 7 in addition to the overflow weir 33 or the outflow basin 32 of the MAP reaction tank 30. In this case, a small amount of the hardly soluble salt remaining while being stored in the treated water tank 7 is easily dissolved, and scale generation on the inner wall of the pipe can be prevented.

  FIG. 4 shows an embodiment in which the MAP reaction tank 30 is provided with a magnesium chloride dissolution tank 8 for providing a magnesium source. Connected to the magnesium chloride dissolution tank 8 are a supply pipe for adding at least a part of the effluent water from the MAP reaction tank 30 and a magnesium supply pipe for adding magnesium to the MAP reaction tank 30 as a magnesium chloride aqueous solution. . In the case of the embodiment shown in FIG. 4, a scale dispersant may be added to the magnesium chloride dissolution tank 8 in addition to the overflow weir 33 or the outflow basin 32 of the MAP reaction tank 30. A small amount of the residual hardly soluble salt supplied to the magnesium chloride dissolution tank 8 is easily dissolved by the scale dispersant and becomes magnesium ions necessary for MAP formation. Further, a treated water tank 7 shown in FIG. 3 may be provided between the MAP reaction tank 30 and the magnesium chloride dissolution tank 8. In this case, the scale dispersant can be added to one or both of the treated water tank 7 and the magnesium chloride dissolution tank 8.

  FIG. 5 shows an embodiment in which a separation liquid tank 9 is provided in which at least a part of the effluent from the MAP reaction tank 30 is mixed with the separation liquid from the dehydration equipment 2 and then sent to the biological treatment equipment 4. In the embodiment shown in FIG. 5, a scale dispersant may be added to the separation liquid tank 9 in addition to the overflow weir 33 or the outflow basin 32 of the MAP reaction tank 30. Moreover, the magnesium chloride dissolution tank 8 may be provided similarly to FIG. 4, and at least a part of the effluent water from the MAP reaction tank 30 may be sent back to the MAP reaction tank 30 as a solution containing a magnesium source. When the magnesium chloride dissolution tank 8 is provided, a scale dispersant may be further added to the magnesium chloride dissolution tank 8. Moreover, the treated water tank 7 shown in FIG. 3 may be provided, and a scale dispersant may be further added.

  FIG. 6 shows that the effluent water from the MAP reaction tank 30 is stored in the treated water tank 7 before being supplied to the biological treatment equipment 4, partly sent to the magnesium chloride dissolution tank 8, and partly sent to the separation liquid tank 9. An embodiment is shown. The scale dispersant can be added to any one or more of the treated water tank 7, the magnesium chloride dissolution tank 8, and the separation liquid tank 9 in addition to the overflow weir 33 or the outflow basin 32 of the MAP reaction tank 30. As the magnesium source, magnesium hydroxide may be used instead of magnesium chloride.

  In the illustrated embodiment, one MAP reaction tank 30 is used, but a plurality of MAP reaction tanks 30 may be connected in series. In this case, a scale dispersant may be added to the overflow weir 33 or the outflow basin 32 of each MAP reaction tank 30, or the scale dispersant is added to the overflow dam 33 or the outflow basin 32 of the most downstream MAP reaction tank 30. It may be added.

  Moreover, the excess sludge generated in the biological treatment equipment 4 and the coagulation sedimentation-sand filtration or membrane separation-activated carbon equipment 5 is returned to the pre-dehydration equipment 2, mixed with a new treatment object, and dehydrated, and the resulting dewatering treatment is performed. Water may be recycled to the MAP reactor 30 for reuse.

  Moreover, although demonstrated using the MAP reaction tank as a hardly soluble salt formation reaction tank, a HAP reaction tank or another reaction tank may be sufficient. In the case of a HAP reaction tank, a calcium dissolution tank and a calcium supply pipe are used instead of the magnesium dissolution tank and the magnesium supply pipe in order to add calcium chloride instead of magnesium chloride, but the apparatus configuration is almost the same. The water to be treated in the HAP reaction tank is dehydrated in a pre-dehydration facility, denitrified in a denitrification tank, nitrified in a nitrification tank, and then flows into the HAP reaction tank.

  The MAP reaction tank and the HAP reaction tank are equipped with an apparatus configuration necessary for a normal MAP reaction tank and a HAP reaction tank, such as an alkali source supply unit, but are not related to the addition of a scale dispersant. The description of the apparatus configuration is omitted.

  The phosphorus recovery and scale generation prevention method of the present invention is characterized in that a scale dispersant is added to the supernatant water discharge part of the hardly soluble formation reaction tank. As the supernatant water discharge part, an overflow weir or an outflow gutter is preferable. The addition of the scale dispersant is preferably controlled in conjunction with the supply of the treated raw water to the hardly soluble formation reaction tank. The scale dispersant is added when the treated raw water is supplied, and the scale dispersant is added when the supply of the treated raw water is stopped. Neither is added. An appropriate amount of the scale dispersant can be added by linking the addition of the scale dispersant with the supply of the raw water for treatment.

  The scale dispersant that can be added in the present invention may be a known scale dispersant such as an acrylic acid scale dispersant, a maleic acid scale dispersant, a phosphoric acid scale dispersant, a sulfonic acid scale dispersant, and a phosphone. One type selected from acid-based scale dispersants or a mixture of two or more types thereof is preferable. Chemical formula (1):

It is also possible to use bis (poly-2-carboxyethyl) phosphonic acid represented by

  The polyacrylic acid-based scale dispersant has an average molecular weight of 500 to 50,000, preferably a water-soluble polymer in the range of 1,000 to 10,000, and the polymaleic acid-based scale dispersant has an average molecular weight of 200 to 20,000, preferably in the range of 500 to 5,000. Examples of the water-soluble polymer and phosphonic acid-based scale dispersant include water-soluble polymers having an average molecular weight of 100 to 10,000, preferably 100 to 1,000. Examples of water-soluble polymers include acrylic acid, sodium acrylate, methacrylic acid, 2-hydroxy-3-allyloxy-1-propanesulfonic acid (HAPS), maleic acid, and 2-acrylamido-2-methylpropanesulfonic acid (AMPS). , 2-hydroxyethyl methacrylate (HEMA), bis (poly-2-carboxyethyl) phosphonic acid, nitrilotrimethylenephosphonic acid (NTMP), hydroxyethylidene disulfonic acid (HEDP), ethylenediaminetetramethylenephosphonic acid (EDTP), etc. Or a copolymer can be mentioned.

  The amount of the scale dispersant added is preferably less than 20 mg / L, more preferably 2 mg / L or more and less than 20 mg / L, and most preferably 2 mg / L or more and 10 mg / L or less. If added excessively, excess sludge generated in the biological treatment equipment 4 in the latter stage and the coagulation sedimentation-sand filtration or membrane separation-activated carbon equipment 5 is returned to the pre-dehydration equipment 2 for dehydration, and the resulting dehydrated water is hardly soluble. When circulating and reusing in the salt formation reaction tank, the hardly soluble salt formation reaction is inhibited. Moreover, as described later, even when added in an amount of 20 mg / L or more, the scale suppression effect was not improved.

  Hereinafter, the present invention will be described specifically by way of examples.

  In the wastewater / septic tank sludge treatment facility of the treatment flow shown in FIG. 1, a scale dispersant is added to the overflow weir 33 of the MAP reaction tank 30 using the MAP reaction tank 30 as the phosphorus recovery equipment 3, and the MAP reaction tank 30 The occurrence of scale in the effluent water pipe from and the properties of treated water from the biological treatment facility 4 were examined.

  As a scale dispersant, Evas Perth 2660 (acrylic acid polymer type scale dispersant manufactured by Mizu ing Co., Ltd.) was used.

  A new outflow pipe from the MAP reaction tank 30 is treated with a sewage / septic tank sludge, and when the reference water level of the MAP reaction tank 30 rises by 50 mm, it is evaluated that a blockage has occurred due to the generation of scale in the outflow water pipe. The number of days required for the reference water level to rise by 50 mm was observed by changing the amount of dispersant added. The results are shown in Table 1 and FIG. In this experiment, the scale dispersant was continuously injected, but the injection method may be intermittent.

  From Table 1, it can be seen that the generation of scale in the outflow pipe is suppressed by adding the scale dispersant. In particular, the scale generation inhibitory effect could be confirmed by adding 2 mg / L or more of the scale dispersant. The amount of scale dispersant added was 10 mg / L, and the effect was the highest, and when it exceeded 10 mg / L, the effect was almost constant.

  Moreover, it has confirmed that the liquid level raise from the reference | standard water level in a MAP reaction tank became gentle by adding a scale dispersing agent.

  Changes in the properties of treated water with and without the addition of a scale dispersant were measured. The results are shown in Table 2.

  From Table 2, it can be seen that no change in the treatment aqueous state due to the addition of the scale dispersant was observed, and the method of the present invention did not have a negative effect on the urine / septic tank sludge treatment.

  Table 3 shows the results of determining the change in the phosphorus recovery rate from the MAP reaction tank 30 due to the addition of the scale dispersant. The phosphorus recovery rate when the scale dispersant is added is measured at the inflow line to the MAP reaction tank 30 (the phosphorus recovery tank In side), and the phosphorus recovery rate when the scale dispersant is not added is discharged from the MAP reaction tank 30. Measurement was made on the line (outside of the phosphorus recovery tank) for comparison.

  From Table 3, no decrease in the phosphorus recovery rate due to the addition of the scale dispersant was observed, and even when the scale dispersant was added in the range of 20 mg / L or less, the MAP crystals grew greatly and phosphorus recovered from the bottom of the MAP recovery tank It was confirmed that there was no effect on the recovery of

Claims (1)

In the supernatant water discharge part of the sparingly soluble phosphate forming reaction tank in the organic wastewater treatment facility, a means for adding a scale dispersant is provided,
A treated water tank that accepts the supernatant water from the hardly soluble phosphate-forming reaction tank, a separation liquid tank that mixes the supernatant water and the dehydrated separation liquid, and at least a part of the supernatant water, and the hardly soluble substance. One or more tanks selected from a magnesium source dissolving tank for supplying a magnesium source to a phosphate forming reaction tank or a calcium source dissolving tank for supplying a calcium source are further provided, and additional scale dispersion is added to the selected one or more tanks. An organic wastewater treatment facility characterized in that a means for adding an agent is provided.