JP3989059B2 - Waste water treatment equipment containing phosphate ions - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a treatment apparatus for domestic wastewater containing phosphate ions, such as wastewater, particularly domestic wastewater or collective housing wastewater.
[0002]
[Prior art]
It is well known that the presence of phosphorus compounds is one of the causes of eutrophication of rivers and lakes. Moreover, although this phosphorus compound exists abundantly in the domestic household wastewater, the present condition is that the purification process is difficult and an effective measure cannot be taken.
[0003]
Various treatment apparatuses for phosphorus compounds have been proposed, but an iron electrolysis method is known for domestic wastewater (Japanese Patent Laid-Open No. 3-89998). This technique is a technique in which phosphate ions in waste water are reacted with iron ions to coagulate and remove them as water-insoluble salts such as FePO ₄ and Fe (OH) _x (PO ₄ ) _y. An iron electrode installed inside is energized to elute iron ions into the waste water. And as a sewage treatment apparatus using such an electric field elution method, for example, an anaerobic tank, an aerobic tank, and a treated water tank, the sewage in the treated water tank is passed through a treatment apparatus that elutes iron ions that react with phosphoric acid, Some are configured to be returned to an anaerobic tank.
[0004]
[Problems to be solved by the invention]
Among the electrodes installed in the electrolytic cell, the anode-side electrode elutes iron ions when energized, so that the thickness and width of the electrode gradually decrease. As shown in FIGS. 6A to 6C, the degree of decrease (elution amount) of the electrode is such that the lower portion 51 and the edge portion 52 of the electrode 50 are easily melted with time, and the thickness of the electrode is uniform. Does not decrease. As a result, the electrode is cracked in the middle of the electrode during long-term use, and the lower electrode part peels off from the upper electrode part due to its own weight and falls off to the bottom of the electrolytic cell. Therefore, it is uneconomical because the electrodes cannot be effectively used to the end. Further, if the electrode falls off, the phosphorus removal efficiency is lowered, so that the electrode is replaced with a new one. In this case, since the anode side electrode and the cathode side electrode are in contact with the deposited electrode drop piece during replacement, an electric current flows directly between the electrodes if the electrode drop piece is not removed. There may be a problem that electrolysis does not occur in the meantime.
[0005]
In view of the above circumstances, the present invention provides a phosphate ion-containing wastewater treatment apparatus that prevents the electrode from falling off, thereby preventing a reduction in treatment efficiency and reducing the number of maintenance operations. Objective.
[0006]
[Means for Solving the Problems]
The apparatus for treating wastewater containing phosphate ions according to the present invention is a wastewater treatment apparatus containing phosphate ions, and includes a wastewater treatment chamber having a wastewater inlet and outlet, and at least a portion of the wastewater in the treatment chamber. And at least one electrode including an iron ion and / or aluminum ion source and a power source for energizing the electrode, and at least the immersion portion of the electrode is tapered. It is characterized by becoming.
[0007]
The phosphate ion-containing wastewater treatment apparatus of the present invention is a wastewater treatment apparatus containing phosphate ions, and includes at least one wastewater treatment chamber having a wastewater inlet and outlet, and the wastewater in the treatment chamber. The electrode is arranged so as to be immersed, at least one of which includes an iron ion and / or aluminum ion source and a power source for energizing the electrode. A taper is formed and the immersion part is tapered .
[0008]
The phosphate ion-containing wastewater treatment apparatus of the present invention is a wastewater treatment apparatus containing phosphate ions, and includes at least one wastewater treatment chamber having a wastewater inlet and outlet, and the wastewater in the treatment chamber. And an electrode containing at least one iron ion and / or aluminum ion source and a power source for energizing the electrode, and an electrolytic surface of at least the immersion part of the electrode; Is characterized in that a taper is formed on the back surface on the opposite side and the immersion part is tapered .
[0009]
The phosphate ion-containing wastewater treatment apparatus of the present invention is a wastewater treatment apparatus containing phosphate ions, and includes at least one wastewater treatment chamber having a wastewater inlet and outlet, and the wastewater in the treatment chamber. And an electrode including at least one source of iron ions and / or aluminum ions, and a power source for energizing the electrode, and an electrolytic surface of at least the immersed portion of the electrode, and A taper is formed on the back surface opposite to the electrolytic surface, and the immersion portion is tapered .
[0010]
Furthermore, the phosphate ion-containing wastewater treatment apparatus of the present invention is a wastewater treatment apparatus containing phosphate ions, and includes at least one wastewater treatment chamber having a wastewater inlet and outlet, and the wastewater in the treatment chamber. An electrode including at least one iron ion and / or aluminum ion source and a power source for energizing the electrode, and at least an electrolytic surface of the electrode at the immersion part, A taper is formed on the back surface and the side surface opposite to the electrolytic surface, and the immersion portion is tapered .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the processing apparatus of the phosphate ion containing waste_water | drain of this invention is demonstrated based on an accompanying drawing.
[0012]
FIG. 1 is an explanatory view showing an embodiment of a treatment apparatus for phosphate ion-containing waste water of the present invention, FIG. 2 is an enlarged view of the treatment apparatus in FIG. 1, and FIG. 3 is a front view showing an embodiment of an electrode, 4 is a side view of the electrode in FIG. 3, and FIG. 5 is a front view showing another embodiment of the electrode.
[0013]
The processing apparatus of this invention is used for a merged septic tank, for example. As shown in FIG. 1, the combined septic tank comprises a first anaerobic filter bed tank A, a second anaerobic filter bed tank B, a biological filter tank C, a treated water tank D, and a disinfection tank E. 1 Anaerobic filter The waste water flowing into the floor tank A is treated in each tank and then discharged from the disinfection tank E. And the processing apparatus 1 is installed in the circulation path which returns the treated water pumped up by the air pump F from the said treated water tank D to the 1st anaerobic filter bed tank A.
[0014]
As shown in FIGS. 1 and 2, the treatment apparatus 1 is disposed such that a wastewater treatment chamber 4 having a drainage inlet 2 and a drainage outlet 3 and at least a part of the wastewater in the treatment chamber 4 is immersed in the wastewater. Electrodes 5 and 6, a power source 7 for energizing the electrodes 5 and 6, and an air aeration device 8 for supplying air into the waste water in the waste water treatment chamber 4.
[0015]
The electrodes 5, 6 can be fabricated from iron ions and / or aluminum ion sources such as iron, iron alloy, aluminum, aluminum alloy or iron-aluminum alloy.
[0016]
Among the electrodes 5 and 6, the anode (anode) side electrode, for example, the surface of the electrode 5 generates an organic and inorganic oxide film, while the cathode (cathode) side electrode 6 generates hydrogen gas from the surface. Yes. With the hydrogen gas, the surface of the electrode 6 is cleaned and no oxide film is formed. For this reason, when an oxide film is generated on the surface of the electrode 5 on the anode side and the elution amount of iron ions or aluminum ions decreases, the polarity is reversed at predetermined time intervals. Thereby, since elution of iron ions (aluminum ions) can be maintained substantially constant, the dephosphorization performance can be maintained constant. As the inversion time, for example, when it is less than 1 hour, the elution amount of iron ions (aluminum ions) is lowered, and therefore it is preferable to set it to 1 hour or more.
[0017]
As for the said electrodes 5 and 6, as shown to FIGS. 2-4, the immersion part R is tapered at least. Such taper can be obtained, for example, by forming a taper on the electrolytic surface 9 between the electrodes 5 and 6 and the back surface 10 opposite to the electrolytic surface 9. The taper angle α can be appropriately selected according to the width and thickness dimensions of the electrodes 5 and 6, the dimension of the immersion portion R, the electrolytic current, and the like. For example, the width × thickness dimension is 180 × 5 mm. Yes, when the dimension of the immersion part R is 200 mm and the electrolytic current is 0.5 to 1.3 A, it is usually 0.5 to 10 °, preferably 2 to 8 °, particularly preferably. Is 3-5 °. In the present embodiment, the taper angle α of the electrolytic surface 9 and the back surface 10 is the same. However, in the present invention, the taper angle α of the electrolytic surface 9 is not limited to this. The taper angle α of the back surface 10 can be made different.
[0018]
In the present embodiment, since the electrodes 5 and 6 are tapered on the electrolysis surface 9 and the back surface 10 and are tapered, the electrodes 5 and 6 are uniformly dissolved from the lower portion of the electrodes 5 and 6, that is, gradually become thinner from the lower portion. Therefore, it is possible to prevent the electrode from being thinned and dropped out during use. As a result, when an electrode having the same volume as the conventional one is used, the electrode of the present embodiment can be eluted for a longer time than the conventional electrode, which is economical and maintains the processing efficiency. it can. In addition, since the electrode replacement time becomes longer, the number of maintenance can be reduced.
[0019]
In this embodiment, taper is formed on the electrolytic surface and the back surface of the electrode. However, the present invention is not limited to this, and the taper on the back surface is omitted and only the taper of the electrolytic surface is provided. Or, conversely, the taper of the electrolytic surface can be omitted and only the taper of the back surface can be obtained. Alternatively, as shown in FIG. 5, a taper can be formed on the electrolytic surface 9, the back surface 10 and the side surface 11 of the electrode. The taper angle β of the side surface 11 can be the same as the taper angle α. Further, although the taper in this embodiment is formed as a single taper (straight taper), it can be formed into a two-step taper or a multi-step taper.
[0020]
The air aeration apparatus 8 is composed of a porous diffuser pipe 12 or a diffuser plate installed at the bottom center of the waste water treatment chamber 4 and an air pump 13 for sucking compressed air into the diffuser pipe 12. The air diffuser 12 and the air pump 13 are connected by a pipe 14.
[0021]
In the present embodiment, the air diffuser 12 is installed in the center of the bottom of the waste water treatment chamber 4, but in the present invention, the present invention is not particularly limited to this. A position where water-insoluble salt, which is a reaction product of phosphate ions in the waste water and iron ions (aluminum ions) eluted from the electrodes, can be easily selected and installed. For example, the air diffuser 12 is installed perpendicular to the wall 4a on the outlet 3 side of the waste water treatment chamber 4, but the air diffuser 12 is brought close to the wall 4a and parallel to the wall 4a, that is, FIG. In this case, the waste water in the processing chamber is easily convected. Further, the convection of the waste water can be easily generated by moving the diffuser pipe 12 in the vertical direction in the waste water in the processing chamber. In the present embodiment, the reactivity of iron ions and phosphate ions can be improved by stirring the waste water.
[0022]
A conventionally known method can be adopted as the electrolytic elution method for iron (aluminum), and the electrode may be energized continuously, intermittently, or pulsed. The amount of energization varies depending on the concentration of phosphate ions and other ions, the flow rate of wastewater, etc., but the ratio of the concentration of iron ions and / or aluminum ions in the wastewater / phosphate ion concentration (hereinafter abbreviated as “Fe / P”). ) May be adjusted to 0.8 to 3.0, preferably 1.0 to 2.5.
[0023]
In the present invention, the treatment by the electrolytic elution method of iron (aluminum) of the phosphate ion-containing wastewater is carried out by reacting the iron ion (aluminum ion) eluted from the electrode with the phosphate ion in the wastewater to form water-insoluble phosphoric acid and iron. Although a reaction (reaction A) that forms a salt with (aluminum) is utilized, hydroxide ions are present in the waste water, and the eluted iron ions (aluminum ions) also react with the hydroxide ions ( Reaction B). Since reaction B is faster than reaction A, in order to capture phosphate ions, it is necessary to increase the amount of current and increase the elution amount of iron ions (aluminum ions).
[0024]
However, when calcium ions or magnesium ions are present in the waste water, these ions react with hydroxide ions (Reaction D). Since this reaction D has priority over reaction B between iron ions (aluminum ions) and hydroxide ions, reaction B is suppressed, and iron ions (aluminum ions) are effectively used for reaction A with phosphate ions. Furthermore, calcium ions and magnesium ions also react with phosphate ions to form water-insoluble salts, thus contributing to the removal of phosphate ions.
[0025]
For this reason, in this invention, calcium ion or magnesium ion is added, reaction B of iron ion (aluminum ion) and hydroxide ion is suppressed, and reaction A of iron ion (aluminum ion) and phosphate ion is efficiently performed. It can also be made. Thereby, the amount of energization can be reduced, power can be saved, and the elution amount of iron and aluminum can be reduced.
[0026]
As described above, the wastewater treatment apparatus of the present invention can be used particularly advantageously for general household wastewater. Therefore, it may be used alone, but it can be combined with other purification systems such as activated sludge method, membrane separation method, anaerobic / aerobic circulation method, etc. to make a comprehensive wastewater purification system for households and collective housing. it can. It can also be used in large-scale processing systems (human waste treatment plants).
[0027]
Next, the present invention will be described based on examples, but the present invention is not limited to such examples.
[0028]
EXAMPLE Using an iron electrolysis elution waste water treatment apparatus shown in FIG. 1, a phosphate ion concentration of 5 mg / liter (added as H ₃ PO ₄ ), Na ⁺ 200 mg / liter and Ca ²⁺ 20 mg / liter is supplied from the inlet. The test wastewater was introduced at a flow rate of 1 liter / min.
[0029]
A high-purity iron plate was used as the electrode immersed in the waste water. The amount of current applied to the electrode was 1.2 A so that Fe / P was 1.5, and the polarity was reversed every hour.
[0030]
Then, by electrolysis of the electrode, the eluted iron ions react with phosphate ions to produce water-insoluble salts. The generated salt is stirred together with the inflowing water by the air (2 liter / min) generated from the air diffuser and flows out to the outflow side. Therefore, there was almost no accumulation of water-insoluble salts.
[0031]
Next, as a result of examining the filtrate obtained by filtering the waste water collected at the outlet with a filter having a pore diameter of 0.45 μm in accordance with the total phosphorus analysis method (46.3) standardized in JIS K 0102, the removal efficiency of phosphorus was 90%. It turns out that it is above.
[0032]
【The invention's effect】
As described above, according to the present invention, since the electrode is tapered by the taper, it is possible to prevent the electrode from being uniformly dissolved from the lower part than before and becoming thinner and falling off in the middle. For this reason, since it can be used longer than before, it is economical, and the replacement time of the electrodes can be delayed, so that the number of maintenance can be reduced.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an embodiment of a treatment apparatus for phosphate ion-containing waste water of the present invention.
FIG. 2 is an enlarged view of the processing apparatus in FIG.
FIG. 3 is a front view showing an embodiment of an electrode.
4 is a side view of the electrode in FIG. 3. FIG.
FIG. 5 is a front view showing another embodiment of an electrode.
FIG. 6 is an explanatory diagram showing the degree of decrease in the dissolution amount of a conventional electrode.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Processing apparatus 2 Inlet 3 Outlet 4 Processing chamber 5, 6 Electrode 7 Power supply 8 Air aeration apparatus 9 Electrolytic surface 10 Back surface 11 Side surface R Dipping part

Claims (5)

  A wastewater treatment apparatus containing phosphate ions, a wastewater treatment chamber having a drainage inlet and an outlet, and at least a part of which is immersed in the wastewater in the treatment chamber, at least one of which is an iron ion And / or a phosphate ion-containing wastewater treatment apparatus comprising an electrode including an aluminum ion generation source and a power source for energizing the electrode, wherein at least a dipping portion of the electrode is tapered. A wastewater treatment apparatus containing phosphate ions, a wastewater treatment chamber having a drainage inlet and an outlet, and at least a part of which is immersed in the wastewater in the treatment chamber, and at least one of which is an iron ion And / or an electrode including an aluminum ion generation source and a power source for energizing the electrode, wherein at least the immersion surface of the electrode is tapered and the immersion portion is tapered. Waste water treatment equipment containing phosphate ions. A wastewater treatment apparatus containing phosphate ions, a wastewater treatment chamber having a drainage inlet and an outlet, and at least a part of which is immersed in the wastewater in the treatment chamber, and at least one of which is an iron ion And / or an electrode including an aluminum ion generation source and a power source for energizing the electrode, and at least a back surface of the electrode opposite to the electrolytic surface of the immersion portion is tapered to form the immersion portion. An apparatus for treating phosphate ion-containing waste water that is tapered . A wastewater treatment apparatus containing phosphate ions, a wastewater treatment chamber having a drainage inlet and an outlet, and at least a part of which is immersed in the wastewater in the treatment chamber, and at least one of which is an iron ion And / or an electrode including an aluminum ion generation source and a power source for energizing the electrode, and at least the electrolytic surface of the immersion portion of the electrode and the back surface opposite to the electrolytic surface are tapered. A treatment apparatus for phosphate ion-containing waste water, wherein the immersion part is tapered . A wastewater treatment apparatus containing phosphate ions, a wastewater treatment chamber having a drainage inlet and an outlet, and at least a part of which is immersed in the wastewater in the treatment chamber, and at least one of which is an iron ion And / or an electrode including an aluminum ion generation source and a power source for energizing the electrode, and at least the electrolytic surface of the immersion portion of the electrode, and the back surface and the side surface opposite to the electrolytic surface are tapered. A processing apparatus for phosphate ion-containing waste water that is formed and the immersion part is tapered .

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