JP3351930B2 - Wastewater biological denitrification - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for biologically removing nitrogen from wastewater, and more particularly, to a method for removing wastewater containing organic matter, nitrate nitrogen and Ca ²⁺ in a fluidized-bed anaerobic water treatment apparatus. The present invention relates to a biological denitrification method for wastewater in which a high-density denitrification sludge granulated with CaCO ₃ as a nucleus is formed by contact with nitrogen sludge under stirring, and denitrification is performed using the sludge granulation.

[0002]

2. Description of the Related Art In order to treat wastewater containing nitrate nitrogen with denitrification sludge for denitrification, a floating activated sludge method has been conventionally used. The floating activated sludge method has the advantage of being able to treat a large amount of wastewater, but it requires a large installation area and is difficult to install in places where there is not enough room on the site. Further, there is a problem that denitrification sludge floats due to nitrogen gas or the like generated by the denitrification treatment, flows out along with the treated water, and reduces the treatment load.

[0003] As another method, wastewater treatment containing nitrate nitrogen using a fluidized-bed type water treatment apparatus has been studied because of the advantages that the installation area is small and the apparatus can be made compact. Floating and outflow are the same as those in the floating activated sludge method, and satisfactory treatment results have not been obtained.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in treating wastewater containing nitrate nitrogen with a fluidized bed type anaerobic water treatment apparatus. It is to provide a possible method of biological denitrification of wastewater.

[0005]

The above objects are achieved by the present invention described below. That is, the present invention, organic matter, when the waste water containing nitrate nitrogen and Ca ²⁺ treating in a fluidized bed anaerobic water treatment system, the exhaust water and the upflow supplied from the lower portion of the apparatus, the apparatus the the denitrification sludge of internal drainage and, of stirring blades
The solution was brought into contact under stirring with a tip peripheral speed of 3 to 30 cm / sec, and the dissolved CO 2 gas and Ca ²⁺ in the wastewater were mixed with CaCO _3.
And forming a high-density granule from CaCO ₃ and denitrified sludge using the generated CaCO ₃ as a nucleus, and treating the nitrate nitrogen with the granule. This is a typical denitrification method.

[0006]

The Ca ²⁺ in the waste water to be treated reacts with the dissolved carbon dioxide gas to generate CaCO ₃ , and the CaCO ₃ is used as a nucleus and a denitrifying sludge (in the present invention, seed sludge containing denitrifying bacteria and And high-density denitrification sludge granules are formed from the denitrification activated sludge grown using the organic matter and the like in the treated wastewater as a nutrient source. By denitrifying nitrogen, floating and outflow of denitrified sludge is prevented, and high-load treatment of nitrate nitrogen can be performed.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to preferred embodiments. FIG. 1 shows an example of an apparatus used in the present invention. 1 is a denitrification tank. The wastewater to be treated is
The raw water is sent from the raw water inflow pipe 2 to the raw water receiving section 3, and is supplied into the denitrification tank via the stirrer shaft and the raw water falling pipe 4. Stirrer shaft 4
A turbine blade 5 for raising the inside of the denitrification tank by using the wastewater to be treated and the sludge settled in the denitrification tank as an upward flow, and a paddle blade 6 for stirring the sludge is mounted on the upper part thereof. I have. This stirrer shaft 4 is rotated by a variable stirrer 7. The treated waste water rises to the treated water collecting section 8 and is discharged from the treated water outlet 9. Reference numeral 10 denotes a sampling pipe, 11 denotes a sludge discharge port, 12 denotes a drain outlet, and 13 denotes a stand for fixing the denitrification tank 1.

The wastewater treated in the present invention can be applied to the present method as long as the wastewater contains organic matter, nitrate nitrogen and Ca ²⁺ , but a particularly preferred range is at least 100 mg / l of nitrate nitrogen. At least 500 mg of Ca ²⁺
/ L containing wastewater is preferred. If Ca ²⁺ is not contained in the waste water to be treated, or if the concentration in the waste water to be treated is lower than the above concentration, a substance serving as a Ca ²⁺ source should be added to the waste water to be treated. is necessary. Examples of the wastewater to be treated in the present invention include wastewater such as stainless steel nitrate pickling process wastewater in the steelmaking and steel products manufacturing industry and waste acid / waste alkali neutralized water in the industrial waste disposal business.

The wastewater to be treated is supplied to the lower part of the denitrification tank 1 through a raw water downflow pipe 4 and rises upward in the denitrification tank 1 by the rotation of the turbine blades 5, and the denitrification in the tank is stopped. Contact with nitrogen sludge. The dissolved carbon dioxide gas in the treated wastewater is Ca
Reacts with ²⁺ to produce CaCO ₃ . The denitrified sludge is granulated with the generated CaCO ₃ as a core, and the nitrified nitrogen is denitrified by the granulated denitrified sludge to generate nitrogen gas.

A feature of the present invention is that CaCO ₃ is generated by dissolved carbon dioxide and Ca ²⁺ in the wastewater to be treated,
Denitrification sludge is formed into high-density granules using CO ₃ as a core, and nitrate nitrogen is treated with the granulated sludge.
Since the granulated sludge has a high density, the sludge is prevented from rising to the upper part of the denitrification tank due to the nitrogen gas generated by the denitrification of nitrate nitrogen, and the sludge remains in the denitrification tank, The nitrogen is denitrified.

The denitrification sludge in the denitrification tank comes in contact with the wastewater to be treated under stirring. The stirring is performed by a stirring paddle blade 6 attached to a stirrer shaft 4. The preferable stirring for promoting the granulation of the denitrification sludge is that the peripheral speed at the tip of the stirring blade is 3 to
The stirring is in the range of 30 cm / sec.

The apparatus shown in FIG. 1 is an example of the apparatus used in the present invention, and the waste water to be treated may be directly supplied to the lower part of the apparatus. A method other than the above, for example, a means for supplying the wastewater to be treated by a pump may be used. Drainage is 0.4-3.0m
/ Hr, it is preferable that the inflow rate is adjusted so as to be an upward flow and supplied so as to be brought into contact with the denitrification sludge. In addition, the shape, type, number and the like of the stirring blades are not particularly limited in the stirring of the denitrification sludge as well, except that the peripheral speed of the tip of the stirring blade is within the above-mentioned range.

The initial denitrification seed sludge concentration (ML) in the denitrification tank
SS) is usually 5,000 to 15,000 mg / l. The sludge partially settles at the bottom of the tank, but rises with the upward flow of the wastewater to be treated. The sludge under treatment and the wastewater to be treated are subjected to treatment such as denitrification due to contact between the two, and the treated wastewater rises to the treated water collecting portion at the upper part of the tank, and the treated water outlet. Is discharged as treated water from which nitrate nitrogen and the like have been removed.

[0014]

Next, the present invention will be described more specifically with reference to examples. Example 1 Waste water was treated using the apparatus shown in FIG. 2 (upflow sludge blanket reactor). The glass cylindrical reactor has a diameter of 8 cm, a straight body length of 77 cm (volume of about 4 liters), and a precipitation part length of 26 cm (volume of about 2.
5 liters). On the rotating shaft in the reactor, two mesh-shaped stirring blades were installed in four stages, and the peripheral speed was 10 cm / sec.
It is rotated by a motor (M) so that it becomes c. The wastewater to be treated in the raw water tank is supplied to the lower part of the reactor by a pump (P ₁ ) at a flow rate of 36 liter / d so as to flow upward at 0.6 m / hr.
ay. The treated water that has been treated and rises to the settling section overflows and is sent to the treated water tank, and a portion of the treated water in the treated water tank flows upward at the lower part of the reactor using the pump (P ₂ ) as described above. As supplied.

An artificial raw water (pH 7.5) having the following composition was used as the water to be treated.

[Table 1]

The sludge containing denitrifying bacteria (excess sludge from the Kimitsu Futtsu terminal treatment plant) was used after being sufficiently used in the above-mentioned raw water. Initial MLSS of sludge (the amount of activated sludge in the mixture)
And VSS (the amount of microorganisms in the mixture) are 500
mg / l and 6,700 mg / l.

The treatment of the water to be treated is performed at 30 ° C.
For 60 consecutive days. Average ML in continuous processing
SS, average VSS, removal rate of the average NO ₃ -N, average removal _{g-NO 3 -N / g-} MLSS / day, mean-removed g-
NO ₃ -N / g-VSS / day, average volume load (kg
-NO ₃ -N / m ³ / day) and the pH of the treated water are shown in Table 2.
Shown in Immediately after the start of the treatment, a part of the sludge floated, but as the treatment proceeded, the sludge granulation progressed (confirmed visually), and the rise of the sludge was not recognized.

Comparative Example 1 The biological treatment apparatus shown in FIG.
The same raw water as in Example 1 was treated by the floating activated sludge method using an aeration tank (8 liter capacity). 6.0 liters of raw water
Torr / day. The treated water is sent to the settling tank together with the sludge that has floated, and the sludge that has settled is 7 ml / min. Return to the anaerobic tank. The same sludge as in Example 1 was used. The initial MLSS and VSS of sludge were 4.0 and 0 respectively.
00 mg / l and 3,000 mg / l. Both tanks are kept at 30 ° C. Table 2 shows the results of continuous treatment for 60 days.
Shown in

[0019]

[Table 2]

As is clear from Table 2 , according to the method of the present invention, the activated sludge concentration was increased by 19.3% from before the start of the treatment, and as a result, a high treatment load became possible. Further, it can be seen that the processing load of the method of the present invention is four times higher than that of the conventional floating activated sludge method of the comparative example.

[0021]

According to the present invention described above, the denitrified sludge is formed into a high-density granulated product, and the floating of the denitrified sludge due to the denitrification reaction of the wastewater containing nitrate nitrogen is prevented. In addition, the method of the present invention can perform a much higher load treatment of nitrate nitrogen, which is far superior to the conventional floating activated sludge method, requires less installation area, and can be made compact.

[0022]

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an apparatus used in the present invention.

FIG. 2 is a diagram illustrating an apparatus used in the first embodiment.

FIG. 3 is a diagram showing an apparatus used in a comparative example.

[Explanation of symbols]

1: Denitrification tank 2: Raw water inflow pipe 3: Raw water receiving section 4: Raw water falling pipe with agitator shaft 5: Turbine blade 6: Paddle blade for sludge stirring 7: Variable stirrer 8: Treated water collecting section 9: Treated water outlet 10: sampling tube 11: sludge waste sludge outlet 12: drain outlet 13: pedestal M: motor P _1: pump P _2: pump

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-55-59894 (JP, A) JP-A-4-310293 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C02F 3/34 101

Claims (2)

(57) [Claims] When treating waste water containing organic matter, nitrate nitrogen and Ca ²⁺ in a fluidized bed type anaerobic water treatment device, the waste water is supplied from a lower portion of the device to be an upward flow, and The denitrification sludge and the drainage are mixed at a peripheral speed of the stirring blade tip of 3 to 30.
cm / sec under agitation and dissolved in wastewater
In addition to generating CaCO ₃ with carbon dioxide gas and Ca ²⁺ , high-density granules are formed from CaCO ₃ and denitrified sludge using the generated CaCO ₃ as a nucleus, and nitrate nitrogen is treated with the granules. A biological denitrification method for wastewater, comprising: 2. An inflow speed of the drainage of 0.4 to 3.0 m / h.
2. The method for biologically removing nitrogen from wastewater according to claim 1, wherein the wastewater is brought into contact with denitrification sludge as an upward flow of r.