JP2001149974A - Wastewater treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wastewater treatment method capable of reducing the amount of nitrogen and / or phosphorus added for treating BOD and reducing the amount of excess sludge generated. To provide. SOLUTION: The amount of nitrogen and phosphorus with respect to BOD is
A carrier is charged into an aeration tank of organic wastewater having a BOD: nitrogen: phosphorus weight ratio of less than 100: 5: 1, and the amounts of nitrogen and phosphorus in raw water introduced into the aeration tank are determined by weight ratio. B
So that OD: nitrogen: phosphorus is 100: 5: 1 or more,
Insufficient nitrogen and / or phosphorus are added to the raw water, and the number of cells with respect to the volume load of the carrier is measured, and the number of cells in the carrier is substantially constant, and then added to the raw water. The amount of nitrogen and / or phosphorus is reduced to a BOD: nitrogen: phosphorus weight ratio of 100: 2.5: 0.5 or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for treating wastewater.

[0002]

2. Description of the Related Art As a conventional organic wastewater treatment method, an activated sludge method is mainly used. In the conventional activated sludge method, a biological oxygen demand (B
Nutrient sources (Nitrogen (N) and Phosphorus (P)) for OD)
Are added so that the weight ratio becomes BOD: N: P = 100: 5: 1 or more.

[0003]

In the case where the amount of nitrogen or phosphorus in the wastewater is largely insufficient, the conventional activated sludge method requires the above-mentioned amount (BOD: N: P by weight ratio) to treat BOD. = 100: 5: 1 or more), so that a large amount of nitrogen and phosphorus must be added, and there is a problem that the running cost is high. Also,
In the conventional activated sludge method, the amount of surplus sludge generated is as large as 50 to 80% (weight ratio) of the removed BOD, and therefore, there is a problem that the processing cost of the surplus sludge is increased.

[0004] The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide nitrogen and / or nitrogen added for treating BOD.
Alternatively, it is an object of the present invention to provide a method for treating wastewater in which the amount of added phosphorus can be reduced and the amount of excess sludge can be reduced.

[0005]

According to the present invention, there is provided a method for treating wastewater, wherein the amount of nitrogen and phosphorus relative to BOD is 100: 5: BOD: nitrogen: phosphorus weight ratio.
Put the carrier into the aeration tank of less than one organic wastewater,
The amounts of nitrogen and phosphorus in the raw water introduced into the aeration tank are:
Insufficient nitrogen and / or phosphorus is added to the raw water so that the weight ratio of BOD: nitrogen: phosphorus is 100: 5: 1 or more, and the number of cells per volume load of the carrier is measured. After the number of cells in the carrier has become substantially constant, the amount of nitrogen and / or phosphorus added to the raw water is determined by the BOD:
The weight ratio of nitrogen: phosphorus is reduced to 100: 2.5: 0.5 or less. Here, the measurement of the number of bacterial cells with respect to the volume load of the carrier was performed by using Kikkoman AT
Using the reagent kit for P measurement “Lucifer 250 Plus”, the number of microorganisms and the luminescence (ATP
(Proportional to the amount of (adenosine triphosphate)) is plotted on a log-log graph, and this is used as a calibration curve to obtain the AT.
A method of calculating the number of microorganisms from the amount of P emission was employed. The phrase "the number of bacterial cells on the carrier becomes substantially constant" means a state in which the number of bacteria inhabiting per unit volume of the carrier obtained by the above-described method for measuring the number of bacterial cells does not change with time.

[0006] Microorganisms repeatedly grow and die inside the carrier. In the present invention, after the microorganisms have sufficiently grown on the carrier, BOD is removed using nitrogen and phosphorus of the dead microorganisms. As a result, the amount of nitrogen and / or phosphorus added to the BOD can be reduced to a predetermined amount (by weight, 10
0: 5: 1). Then, in order to decrease the amount of nitrogen and / or phosphorus added to the BOD, nitrogen and / or
Alternatively, phosphorus is deficient, suspended sludge is not propagated, and the amount of surplus sludge can be reduced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a wastewater treatment apparatus used in a wastewater treatment method according to the present invention. The wastewater treatment apparatus shown in FIG. 1 is an example in which microorganisms are immobilized in an acetalized PVA-based hydrogel in a wastewater treatment tank as a carrier, and organic substances in wastewater are decomposed and removed under aerobic conditions. It is a flowchart in the case of doing. 2 is a wastewater treatment tank and 6 is a final sedimentation tank. First, waste water 1 is supplied to a waste water treatment tank 2 from a first sedimentation tank (not shown). In the wastewater treatment tank 2, acetalized PVA hydrogel 3 is previously charged into wastewater at the lower limit of operation, and is fluidized by the air diffuser 4 provided at the bottom of the wastewater treatment tank 2. Reference numeral 5 denotes a blower connected to the diffuser 4, which is a driving unit for the diffuser 4. The wastewater is biologically treated in a wastewater treatment tank 2.

When air is blown out from the air diffuser 4 while introducing the wastewater 1 into the wastewater treatment tank 2, oxygen is supplied to the mixed solution in the wastewater treatment tank 2 and the rising bubble flow at this time causes the oxygen to be supplied. A circulating flow is generated in the processing tank. With this circulating flow,
In the process of the acetalized PVA hydrogel 3 flowing in the wastewater treatment tank 2, microorganisms that decompose and remove organic substances are attached to and bound to the hydrogel 3. Therefore, as a result of sufficient contact between the microorganisms and the organic matter, the organic matter in the mixed solution is decomposed and removed extremely efficiently and at a high speed. In addition, the microorganisms immobilized inside the carrier hardly peel off when the acetalized PVA hydrogel 3 flows in the mixed solution. Various screens or the like may be appropriately provided in the treatment tank in order to prevent the acetalized PVA-based hydrogel from overflowing.

The biologically treated water is sent to a final sedimentation tank 6 where the sediment is removed from a sludge discharge pipe 7,
The supernatant water 8 is discharged. The wastewater treatment tank used in the wastewater treatment apparatus of the present invention can increase the efficiency of wastewater treatment by using an acetalized PVA-based hydrogel. The use of gel can dramatically increase the wastewater treatment effect.

The carrier in the method for treating wastewater of the present invention comprises:
It is necessary that microorganisms can be present inside. As such a carrier, polyvinyl alcohol,
A hydrogel carrier such as polyethylene glycol and polyacrylamide may be mentioned, and a polyvinyl alcohol crosslinked gel carrier is particularly preferred. The type of microorganism is not particularly limited, and may be any of bacteria, actinomycetes, molds, yeasts, and the like, and includes pure culture, mixed culture, and activated sludge. Specific examples of microorganisms include the genus Mucor and Fusarium.
arium spp., Cladothr
ix) genus, sphaerotilus (Sphaerotilu)
s) genus, Zooglea genus, Leptomitus genus, Aspergillus (As)
pergillus, Rhizopu
s) Genus, shoot monas (Pseudomonas)
Microorganisms belonging to the genus, genus Acetobacter, genus Streptomyces, genus Escherichia, genus Saccharomyces, genus Candida, and the like can be mentioned. In addition, sulfur bacteria, methane bacteria, butyric bacteria, lactic acid bacteria, Bacillus subtilis, deformed bacteria, incomplete bacteria, nitrate bacteria, nitrite bacteria,
Denitrifying bacteria are also included.

[0011]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

Example 1 BOD: 1000 mg using methanol as a carbon source, ammonium chloride as a nitrogen source and dipotassium hydrogen phosphate as a phosphorus source.
/ L, nitrogen; 60 mg / L, phosphorus; 15 mg / L, to prepare a test solution. 100 ml of PVA gel preliminarily acclimated with activated sludge in the above medium was added to an aeration tank having an internal volume of 1 L, and 1.2 L of the test solution was added under aeration and stirring.
/ D, and treated water was drawn out by an overflow method while preventing the gel carrier from flowing out by a mesh partition, and BOD removal treatment from the test solution was performed. The processing performance was stabilized in one week, and the BOD removal rate was 90%. The rate of generation of excess sludge was 35% of the removed BOD.

[0013] Using the same carrier, the test solution is nitrogen;
The test was continued after changing to 0 mg / L, phosphorus; 5 mg / L. After 3 days, a stable removal behavior was exhibited, the BOD removal rate was 89%, and the generation rate of excess sludge was 25%.

Example 2 The composition of the test solution was nitrogen: 10 mg / L, phosphorus: 2 mg / L
The test was performed by the same operation as in Example 1 except that the test was changed to. BOD removal rate is 88%, excess sludge generation rate is 2
It was 0%.

Example 3 A BOD removal test was performed in the same manner as in Example 1 except that 100 mL of a polyethylene glycol gel was used instead of the PVA gel carrier. BOD; 1000 mg /
L, nitrogen; BO at 60 mg / L, phosphorus; 15 mg / L
The D removal rate was 85%, and the excess sludge generation rate was 37%. The concentration of the test solution was nitrogen: 20 mg / L, phosphorus: 5 mg
/ L, the BOD removal rate was 84%, and the excess sludge generation rate was 30%.

[0016]

According to the wastewater treatment method of the present invention, even when nitrogen or phosphorus in the wastewater is insufficient, it is not necessary to add a large amount of nitrogen and phosphorus, and the amount of generated excess sludge is reduced. Few.

[Brief description of the drawings]

FIG. 1 is a schematic view of an example of a wastewater treatment device used in a wastewater treatment method of the present invention.

[Explanation of symbols]

 1: drainage 2: wastewater treatment tank 3: PVA hydrogel 4: diffuser 5: blower 6: final sedimentation tank 7: sludge discharge pipe 8: supernatant water

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D003 AA14 AB02 BA02 CA03 EA14 EA30 FA02 4D040 DD31

Claims (3)

[Claims] 1. The amount of nitrogen and phosphorus relative to BOD is
A carrier is charged into an aeration tank of organic wastewater having a BOD: nitrogen: phosphorus weight ratio of less than 100: 5: 1, and the amounts of nitrogen and phosphorus in raw water introduced into the aeration tank are determined by weight ratio. B
So that OD: nitrogen: phosphorus is 100: 5: 1 or more,
Insufficient nitrogen and / or phosphorus are added to the raw water, and the number of cells with respect to the volume load of the carrier is measured, and the number of cells in the carrier is substantially constant, and then added to the raw water. A method for treating wastewater in which the amount of nitrogen and / or phosphorus is reduced to a BOD: nitrogen: phosphorus weight ratio of 100: 2.5: 0.5 or less. 2. The method according to claim 1, wherein the carrier is a hydrogel. 3. The method for treating wastewater according to claim 2, wherein the carrier is a polyvinyl alcohol crosslinked gel carrier.