JPH1015585A - Biological dephosphorization of organic sewage and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the generation amt. of excessive sludge of an anaerobic/ aerobic biological dephosphorization method zero, to prevent the deterioration of a phosphorus removing ratio and to recover a phosphorus component in sewage as resources such as compost or the like. SOLUTION: In an apparatus biologically purifying org. sewage by an anaerobic/aerobic biological dephosphorization means 1 and a method therefor, a part of activated sludge is extracted from the dephosphorization means 1 and a phosphorus component is emitted to a liquid side in a second anaerobic tank 5 independent of the dephosphorization means 1 to be subjected to solid- liquid separation and the phosphorus component emitted to the liquid side is removed by a chemical phosphorus removing means 6 and, separately from this, the other part of the activated sludge extracted from the dephosphorization means 1 is treated in an ozone oxidation tank 7 and the solid-liquid separation sludge and ozone treated sludge from the second anaerobic tank 5 are supplied to the dephosphorization means 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology for highly purifying phosphorus-containing wastewater such as sewage, and more particularly to a novel technology capable of reducing the amount of excess sludge generated, removing phosphorus to a high degree, and recovering phosphorus as a resource. About.

[0002]

2. Description of the Related Art The most typical technique for removing phosphorus from organic wastewater such as sewage is an anaerobic / aerobic biological phosphorus removal method. This technology supplies organic sewage to an anaerobic tank together with returned sludge from the subsequent solid-liquid separation step, and converts activated sludge (in which dephosphorylated bacteria coexist) in the returned sludge into phosphorus components (mainly phosphoric acid). Ion). Thereafter, a mixture of the organic sludge and the activated sludge from which the phosphorus component has been discharged is allowed to flow into an aerobic tank (aeration tank), and after the phosphorus component dissolved in the mixture is taken in by the dephosphorus bacteria and the BOD is removed. The activated sludge is subjected to solid-liquid separation, and the solid-liquid separated sludge is recycled to the anaerobic tank again.

[0003] However, the conventional biological dephosphorization method has the following disadvantages. In other words, phosphorus is not removed except in the form of being taken up by activated sludge, and unless the sludge that has taken up phosphorus is actively discharged out of the system as excess sludge, the material balance of phosphorus is not established and a high phosphorus removal rate is achieved. I can't get it. Therefore, if any measure is taken to reduce the amount of excess sludge generated, the phosphorus concentration of the treated water will inevitably increase. For this reason, it has been recognized that the conventional biological dephosphorization method cannot reduce the amount of excess sludge generated in principle,
It was considered unavoidable even if the sludge treatment became a heavy burden.

[0004]

SUMMARY OF THE INVENTION The present invention cannot be achieved by the prior art in which the amount of excess sludge generated in the anaerobic / aerobic biological phosphorus removal method can be reduced to zero and the phosphorus removal rate does not deteriorate. It is an object of the present invention to provide a new system capable of satisfying the requirements and recovering a phosphorus component in wastewater as a resource such as fertilizer.

[0005]

SUMMARY OF THE INVENTION The present inventor has changed the process configuration of the biological dephosphorization method so that biological phosphorus uptake, chemical phosphorus removal, and oxidation of sludge by ozone are performed in a novel mode. It has been found that the above-mentioned problems can be achieved by combining the above. That is, the present invention provides (1) a method for biologically purifying organic wastewater by an anaerobic / aerobic biological dephosphorization method, wherein a part of the activated sludge is withdrawn from the biological dephosphorization step. The phosphorus component is retained under an anaerobic condition independent of the biological dephosphorization step, and while discharging the phosphorus component from the activated sludge to the liquid side or after being discharged, solid-liquid separation is performed, and the phosphorus component discharged to the liquid side is chemically separated. In addition to this, another part of the activated sludge extracted from the biological dephosphorization step was subjected to ozone treatment, and the phosphorus component was discharged under anaerobic conditions independent of the biological dephosphorization step. A biological phosphorus removal method for organic wastewater, comprising supplying the solid-liquid separated sludge and the ozone-treated sludge to the biological phosphorus removal step.

(2) The ozone-treated sludge is supplied to an anaerobic part in a biological dephosphorization step (1).
A biological dephosphorization method for organic sewage, and (3) an apparatus for biologically purifying organic sewage having anaerobic / aerobic biological dephosphorization means, An anaerobic part independent of the biological dephosphorization means for retaining a part of the activated sludge drawn out from the means and for solid-liquid separation while discharging or discharging the phosphorus component to the liquid side, and discharged to the liquid side. Organic wastewater organisms, comprising: a chemical phosphorus removing means for removing the phosphorus component which has been removed; and an ozonation means for ozonating another part of the activated sludge extracted from the biological dephosphorization step. Dephosphorization device.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of the configuration of the method and apparatus of the present invention. Anaerobic tank 2 of biological dephosphorization means 1 in FIG.
After the organic wastewater (also referred to as raw water) 11 and the return sludge 13 are flowed in and the phosphorus is discharged from the dephosphorylated bacteria, it is flown into the aerobic tank 3 to remove the BOD and to absorb the phosphorus to the dephosphorylated bacteria. Most of the sludge settled in the settling tank as the solid-liquid separation means 4 is recycled to the anaerobic tank 2 as returned sludge 13. A part of the settled sludge or sludge drawn directly from the aerobic tank 3 of the biological dephosphorization means 1 is retained in an anaerobic tank (second anaerobic tank) 5 independent of a biological dephosphorization step having a settling function. After that, the phosphorus component (mainly phosphate ion) is discharged from the activated sludge to the liquid side while sedimentation separation or sludge sedimentation separation.

The exhaled phosphorus component is coagulated and removed by adding a coagulant 21 such as slaked lime, iron chloride, aluminum sulfate or the like in the chemical phosphorus removing means 6 to remove the phosphorus component from a calcium phosphate compound such as hydroxyapatite, iron phosphate or the like. , Separated and recovered as aluminum phosphate (recovered phosphorus 2
2). Among them, calcium ion is most suitable because the phosphorus component can be recovered as a calcium phosphate fertilizer. As a phosphorus removing method, a crystallization dephosphorization method or an adsorption dephosphorization method may be applied. The sludge that has discharged the phosphorus component in the second anaerobic tank 5 is returned to the anaerobic tank 2 of the biological phosphorus removing means 1 and again contributes to the purification of the raw water 11.

Next, the sludge extracted from the biological dephosphorization means 1 (the activated sludge is extracted from the aerobic tank 3 of the biological dephosphorization means 1 or the sedimentation tank which is the solid-liquid separation means 4). If the other part is led to the ozone oxidation tank 7 and the sludge is oxidized and decomposed by ozone, a large amount of BOD component is generated from the sludge, and the biodegradability of the sludge is significantly improved. The ozone-oxidized sludge (also referred to as ozone-oxidized sludge) 14 is supplied to the biological dephosphorization means 1, and the ozone-oxidized sludge 14 is assimilated by microorganisms and decomposed into carbon dioxide and water. The anaerobic tank 2 of the biological dephosphorization means 1 is most suitable as the supply position of the ozone oxidized sludge 14. This is because, when the ozone oxidized sludge 14 containing a large amount of the BOD component flows into the anaerobic tank 2, the stress on the dephosphorylated bacteria constituting the returned sludge 13 is increased, and phosphorus is discharged from the dephosphorylated bacteria effectively. .

In another embodiment, a denitrification tank and a nitrification tank are provided in place of the aerobic tank 3 after the anaerobic tank 2 of the biological dephosphorization means 1 so that biological dephosphorization and biological Naturally, simultaneous denitrification is also possible. Thus, the present invention breaks down the stereotype that for the first time it is impossible to reduce the amount of surplus sludge to zero in a biological dephosphorization method in terms of the material balance of phosphorus. It also broke the conventional belief that "sludge elimination technology using ozone cannot be eliminated outside the system in the form of incorporating phosphorus into activated sludge, and is in principle incompatible with phosphorus removal."

[0011]

EXAMPLES The effects of the present invention can be further clarified by the examples of the present invention. EXAMPLE A verification test of the present invention was performed on sewage (average water quality is shown in Table 1) according to the process shown in FIG. Table 2
Shows the test conditions.

[0012]

[Table 1]

[0013]

[Table 2]

As a result of the experiment, the average of the quality of the treated water from the sedimentation tank after the treatment state became stable two months after the start of the treatment was as shown in Table 3, and phosphorus and BOD were highly removed. Although the excess sludge was not extracted during the one-year test, the sludge in the biological dephosphorization step and the M in the aerobic tank were not removed.
Since the LSS was maintained at 3500 to 4000 mg / l, it was confirmed that there was no generation of excess sludge to be disposed of outside the system of the present invention.

[0015]

[Table 3]

Comparative Example 1 A test was performed under the same conditions as in the example except that the second anaerobic tank 5 was omitted in the process of FIG. In this case, since the phosphorus component is not discharged from the sludge, the phosphorus component does not flow into the chemical phosphorus removing means,
Since the phosphorus component could not be recovered, the phosphorus concentration of the treated water 12 was reduced to 5.5 mg / liter, and the phosphorus removal rate was almost zero. Comparative Example 2 A test was performed under the same conditions as in the example except that the ozone oxidation tank 7 was omitted in the process of FIG. In this case, the amount of excess sludge generated was greatly increased to about 60 g per m ^{3 of} sewage.

[0017]

According to the present invention, as a result of combining a sludge oxidation method with ozone, a biological phosphorus removal method and a chemical phosphorus removal method with a new concept, the amount of excess sludge generated can be reduced to zero, Phosphorus removal can be performed stably. Further, according to the present invention, phosphorus ingested by the dephosphorus bacteria can be recovered as a fertilizer resource such as hydroxyapatite.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a processing apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Biological phosphorus removal means 2 Anaerobic tank 3 Aerobic tank 4 Solid-liquid separation means 5 Second anaerobic tank 6 Chemical phosphorus removal means 7 Ozone oxidation tank 11 Organic wastewater 12 Treated water 13 Returned sludge 14 Ozone oxidized sludge 21 Coagulation Agent 22 Recovered phosphorus

Claims (3)

[Claims] 1. A method for biologically purifying organic wastewater by an anaerobic / aerobic biological dephosphorization method, wherein a part of the activated sludge is extracted from the biological dephosphorization step to remove the biological sludge. The phosphorus component is retained under anaerobic conditions independent of the dephosphorization step, and while the phosphorus component is discharged from the activated sludge to the liquid side or discharged, solid-liquid separation is performed, and the phosphorus component discharged to the liquid side is chemically removed. In addition, separately from this, the other part of the activated sludge extracted from the biological dephosphorization step is subjected to ozone treatment, and the phosphorus component is discharged under anaerobic conditions independent of the biological dephosphorization step. A biological phosphorus removal method for organic wastewater, comprising supplying solid-liquid separated sludge and ozone-treated sludge to the biological phosphorus removal step. 2. The method according to claim 1, wherein the ozone-treated sludge is supplied to an anaerobic part in a biological dephosphorization step. 3. An apparatus for biologically purifying organic wastewater having anaerobic / aerobic biological dephosphorization means, wherein a part of the activated sludge extracted from said biological dephosphorization means is retained. An anaerobic section independent of the biological dephosphorization means for solid-liquid separation while discharging the phosphorus component to the liquid side or after discharging, and a chemical phosphorus removing means for removing the phosphorus component discharged to the liquid side And an ozonation means for ozone-treating another part of the activated sludge extracted from the biological dephosphorization step.