JPH09141274A - High-degree treatment for waste water containing phosphorus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the total phosphorus concn. in waste water to a low level when a waste water containing reducing type phosphorus compds. such as phosphites and hypophosphites is to be treated by flocculation, by oxidizing the waste water and then treating the oxdized water by flocculation. SOLUTION: A waste water containing reducing type phosphorus compds. such as phosphites and hypophosphites is first oxidized with an oxidizing agent such as hydrogen peroxide, sodium hypochlorite, calcium peroxide, ammonium peroxide, alkylhydroperoxide, ester of peracid, dialkyl or diacyl peroxide, etc., and metal ion such as iron, titanium and cerium. Then, a flocculant such as a cationic inorg. flocculant is added to the treated waste water containing phosphorus to flocculate and precipitate the oxidized phosphorus compds. and to remove the compds. as a solid material. Thereby, the total concn. of phosphorus in a waste water containing a large amt. of reducing type phosphorus compds. such as phosphites and hypophosphites can be decreased to a low level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for advanced treatment of phosphorus-containing wastewater, and more particularly to a method for advanced treatment of phosphorus-containing wastewater in which wastewater containing a reduced phosphorus compound is subjected to oxidation treatment and coagulation treatment.

[0002]

2. Description of the Related Art Phosphorus compounds are accumulated in lakes, rivers, or in bays into which rivers flow, and eutrophication is a problem. Although the activated sludge method is used for sewage treatment, it is difficult to say that the removal of phosphorus by the activated sludge method is a preferable treatment method because the removal rate varies greatly depending on the conditions. When phosphorus is present in the form of orthophosphoric acid (orthophosphoric acid), it can be removed by precipitation by adding a cationic flocculant that forms a sparingly soluble phosphate. However, when phosphorus is present in the form of a reduced phosphorus compound such as phosphorous acid or hypophosphorous acid, it is extremely difficult to remove it by the so-called aggregation treatment.

[0003]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an efficient method for treating wastewater containing a reduced phosphorus compound and its salt which does not depend on the activated sludge method. As a result of intensive studies, the present inventors have found that phosphorus can be efficiently removed by subjecting the wastewater to an oxidation treatment and then a coagulation treatment.

[0004]

SUMMARY OF THE INVENTION The above objects of the present invention are as follows.
It is achieved by the following inventions. That is, the present invention, phosphorous acid, when performing a coagulation treatment of wastewater containing a reduced phosphorus compound such as hypophosphorous acid, the wastewater is subjected to an oxidation treatment, then the coagulation treatment of the phosphorus-containing wastewater characterized by It is an advanced processing method.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to embodiments of the present invention. The wastewater targeted by the present invention is wastewater containing phosphorous acid, hypophosphorous acid, or the like and a reduced phosphorus compound which is a salt thereof. Further, a salt of orthophosphoric acid may be contained as the phosphorus compound. The source of this wastewater is not particularly limited. FIG. 1 shows a flow of wastewater treatment, which is an example of the present invention. Wastewater containing reduced phosphorus compounds (hereinafter referred to as phosphorus-containing wastewater) is first subjected to oxidation treatment and then to coagulation treatment. In the present invention, the reduced phosphorus compound in the wastewater is removed by the coagulation-sedimentation treatment after the oxidation treatment, so that the reduced phosphorus (H ₂ PO ₂
²⁻ , HPO ₃ ²⁻ ) is considered to be oxidized to ortho type phosphorus (PO ₄ ³⁻ ).

The oxidation treatment in the present invention includes a treatment of the reduced phosphorus compound in the phosphorus-containing wastewater with an oxidizing agent and a treatment without an oxidizing agent such as photo-oxidation or ozone oxidation. Any oxidation treatment that can oxidize to ortho-type phosphorus can be applied. A particularly preferable oxidation treatment is an oxidation treatment by a conventionally known chemical oxidation method (Fenton method) using an oxidizing agent such as hydrogen peroxide and a metal ion such as iron ion.

The oxidation treatment using the conventionally known chemical oxidation method will be described below. As the oxidizing agent, for example, hydrogen peroxide, sodium hypochlorite, calcium peroxide, ammonium persulfate, alkyl hydroperoxide, perester ester, dialkyl peroxide or diacyl, etc. are used, but cost and by-products are used. From the viewpoint of, hydrogen peroxide is most preferable. Hereinafter, hydrogen peroxide will be described as a typical example. As metal ions, iron, titanium, cerium, copper,
Manganese, cobalt, vanadium, chromium, lead ions and the like are used, and any of these metals, metal oxides, metal salts, complexes and the like may be used. Particularly preferred are the first
Iron ion (usually FeSO ₄ .7H ₂ O is used), and ferrous ion will be described below as a typical example.

The amount of hydrogen peroxide used is not particularly limited,
Although the amount varies depending on the concentration of the reduced phosphorus compound in the applied wastewater, the preferable amount used is as oxygen (as O) 10-70.
The range is 0 mg / l. The preferable amount of ferrous iron used is (as Fe) in the range of 30 to 1200 mg / l as iron. Although the treatment temperature and the treatment time are not particularly limited, the oxidation treatment of the phosphorus-containing wastewater by the chemical oxidation method in the present invention is usually performed at 5 to 70 ° C. for about 5 to 60 minutes. In the ordinary chemical oxidation method, the pH of the waste water is generally adjusted to about 2 to 4, but in the present invention, the pH is adjusted.
Even if is not prepared as described above, the treatment effect in the aggregating treatment step does not change.

In the present invention, the treatment efficiency can be improved by treating the phosphorus-containing wastewater with hypochlorite before the oxidation treatment by the above chemical oxidation method. As the hypochlorite, for example, sodium hypochlorite,
Although alkali metal salts such as potassium and calcium, alkaline earth metal salts and the like are used, sodium hypochlorite is the most typical. The treatment of phosphorus-containing wastewater with hypochlorite is performed at 5 to 70 ° C. for about 5 to 60 minutes by adjusting the pH of the wastewater to about 7 to 9 by adding an alkali such as caustic soda. The amount of hypochlorite used is T-P in the wastewater.
Although it depends on the amount of (total phosphorus), it is about 20 to 500 mg / l as available chlorine. After the treatment, the oxidation treatment is subsequently performed by the chemical oxidation method, and the treatment conditions in this case are the same as those described above.

The phosphorus-containing wastewater subjected to the oxidation treatment is then subjected to a coagulation treatment. The coagulation treatment is a step of adding a coagulant to the waste water to coagulate and precipitate the oxidized phosphorus compound and remove it as a solid. As the aggregating agent, conventionally known cationic inorganic or polymer aggregating agents can be used, and by using them in combination, more effective treatment can be performed. As the inorganic coagulant, van sulphate, basic aluminum chloride (for example, polyaluminum chloride PAC, etc.) and the like, as the polymer coagulant, an acrylamide polymer,
Examples thereof include polyethyleneimine, polyamine / epichlorhydrin condensate, and alkylaminoethyl methacrylate copolymer.

Since these aggregating agents have an optimum pH range in which the aggregating effect is maximized, the optimum pH value for the aggregating agent used
It is necessary to control to H. The amount of the flocculant used is not particularly limited, but it depends on the concentration of phosphorus (TP) in the treated effluent, but the concentration of phosphorus in the treated effluent should be below a predetermined amount (reference value). It is necessary to use a large amount. The precipitate can be recovered by a conventionally known method. The recovered precipitate is treated as solid waste or the like.

[0012]

Next, the present invention will be described more specifically with reference to examples and comparative examples. Example 1 Two types of phosphorus-containing wastewater shown in Table 1 were used for oxidation treatment by a chemical oxidation method, and then coagulation treatment. For the treatment by the chemical oxidation method, a hydrogen peroxide-based oxidizer (Hypox manufactured by Environmental Engineering Co., Ltd.) and a ferrous salt-based catalyst (Ferrocat FI manufactured by Environmental Engineering Co., Ltd.) as an Fe catalyst were used. The chemical oxidation treatment was performed at pH 3 and 20 ° C. for 15 minutes. The ratio of hypox and ferrocut FI was 1: 6 (weight ratio), and the total amount used was changed as shown in FIGS. After the chemical oxidation treatment, the pH of the system was adjusted to 7, and an aqueous solution of KEA-621 (manufactured by Environmental Engineering: modified polyacrylamide) as a polymer flocculant (concentration: 0.
1% by weight) was used for the aggregation treatment. The above processing results are shown in Fig. 2 (drainage No. 1) and Fig. 3 (drainage No. 2).

[0013]

[Table 1] (The unit showing the ratio of each component other than pH in the table is mg / l
It is. )

Example 2 Wastewater No. 1 in Table 1 Use 2 to adjust the pH of the wastewater to 3,
After the oxidation treatment at 20 ° C. for 15 minutes and the same oxidation treatment as above without adjusting the pH of the waste water, the pH of each system was set to 7 and the aggregation treatment was performed in the same manner as in Example 1. FIG. 4 shows the relationship between the oxidation treatment conditions and the phosphorus content (TP) in the wastewater after the coagulation treatment. The results shown in FIG. 4 indicate that the pH of the system during the oxidation treatment does not affect the aggregation treatment effect.

Comparative Example 1 The effluents shown in Table 1 were used, PAC (polyaluminum chloride) was used as the coagulant (as Al) 100 mg / l as aluminum, and the pH of the effluent was changed variously to change the phosphorus content The state of removal was investigated. The results are shown in Fig. 5 (drainage No. 1) and Fig. 6 (drainage No. 2).

Comparative Example 2 The drainage No. of Table 1 2 and adjust the pH to 6.5
The relationship between the added amount of AC (mg / l as Al) and the removal of phosphorus (TP) was investigated. FIG. 7 shows the results. Even if the phosphorus cannot be completely removed, it is necessary to add a very large amount of PAC to bring the phosphorus content to a considerably low level.

Example 3 Waste water having the composition shown in Table 2 was diluted (TP after dilution was 122
mg / l) and subjected to an oxidation treatment by a chemical oxidation method, and then an aggregation treatment. The oxidation treatment conditions were the same as in Example 1, and the amounts of the oxidizing agent and the Fe catalyst used were changed as shown in FIG. The aggregation treatment was also performed under the same conditions as in Example 1.
The results are shown in Fig. 8.

[0018]

[Table 2] (The unit showing the ratio of each component other than pH is mg / l)

Example 4 Waste water having the composition shown in Table 2 was diluted (TP after dilution was 11
2.8 mg / l), and subjected to oxidation treatment using sodium hypochlorite, followed by oxidation treatment by a chemical oxidation method, and finally aggregation treatment. The treatment with sodium hypochlorite adjusts the pH of waste water to 8 and the effective chlorine is 1200 mg.
Per liter of sodium hypochlorite at 37 ° C and 7.5
The reaction was carried out for minutes. Then, excess sodium sulfite (Na ₂ SO ₃ ) was added to eliminate residual chlorine, and then residual sodium sulfite was also eliminated by aeration. The treated TP was 105.6 mg / l. Subsequently, Example 1 was repeated except that the oxidizing agent: Fe catalyst was changed to 1: 3 (weight ratio).
In the same manner as above, the oxidation treatment and the aggregation treatment by the chemical oxidation method were performed. FIG. 9 shows the treatment results together with the amounts of the oxidizing agent and the Fe catalyst used.

Comparative Example 3 Waste water having the composition shown in Table 2 was diluted (T-P after dilution is 122
mg / l), and the oxidation treatment was performed by changing the addition amount of sodium hypochlorite. The treatment was carried out at 35 ° C. for 15 minutes after adjusting the pH of the waste water to 8. After the treatment, excess sodium sulfite was added to eliminate residual chlorine, and then residual sodium sulfite was also eliminated by aeration. The processing result is shown in FIG.

[0021]

According to the present invention described above, hypophosphorous acid (P
There is provided a wastewater treatment method capable of reducing the T-P (total phosphorus) concentration of wastewater containing a large amount of reduced phosphorus compounds such as O ₂ ³⁻ ) and phosphorous acid (PO ₃ ³⁻ ) to a low level. It

[Brief description of the drawings]

FIG. 1 is a diagram showing a flow of an example of a processing method of the present invention.

FIG. 2 shows the drainage No. of Example 1. It is a figure which shows the process result of 1.

FIG. 3 shows the drainage No. of Example 1. It is a figure which shows the process result of 2.

FIG. 4 shows the drainage No. of Example 2. PH at the time of 2 oxidation treatment
It is a figure which shows the relationship between the aggregation processing effect.

5 is a drainage No. of Comparative Example 1. FIG. It is a figure which shows the process result of 1.

6 is a drainage No. of Comparative Example 1. FIG. It is a figure which shows the process result of 2.

7 is a drainage No. of Comparative Example 2. FIG. It is a figure which shows the relationship between the additive of the coagulant | flocculant of 2 and a coagulation processing effect.

FIG. 8 is a diagram showing a processing result of the third embodiment.

FIG. 9 is a diagram showing a processing result of the fourth embodiment.

10 is a diagram showing a processing result of Comparative Example 3. FIG.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical location C02F 9/00 503 C02F 9/00 503G 504 504B 504E (72) Inventor Shinya Kurata Higashi, Chiyoda-ku, Tokyo 2-5-12 Kanda Environmental Engineering Co., Ltd.

Claims (3)

[Claims] 1. When a wastewater containing a reduced phosphorus compound such as phosphorous acid and hypophosphorous acid is coagulated, the wastewater is subjected to an oxidation treatment and then a coagulation treatment. Processing method. 2. The advanced treatment method for phosphorus-containing wastewater according to claim 1, wherein the oxidation treatment is a treatment by a chemical oxidation method using an oxidizing agent and metal ions. 3. The advanced treatment method for phosphorus-containing wastewater according to claim 1, wherein the wastewater is treated with hypochlorite and then oxidized by a chemical oxidation method.