JPH0985279A - Oxygen aeration type denitrification treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce installation cost or power cost, in an apparatus equipped with a nitration tank and a denitrification tank and circulating the nitration soln. of the nitration tank to the nitrification tank, by providing a denitrification soln. circulating passage containing a circulating pump and allowing nitration soln. to flow in the denitrification tank from the nitration tank by head difference. SOLUTION: The nitration soln. is allowed to flow in a denitrification tank 1 from a nitration tank 2 through a nitration soln. circulating inflow port 10 by head difference and org. matter in org. waste water is biologically oxidized and decomposed in an anaerobic atmosphere and nitrogen oxide in the nitration soln. is reduced to nitrogen gas to be discharged. A denitrification soln. is drawn out of the denitrification tank 1 by a circulation pump 3 through a denitrification soln. circulating passage 11 and mixed with oxygen-rich gas in an oxygen mixing device 4 and supplied to the nitration tank 2 from a liquid jet device 5 and the residual org. matter and a nitrogen compd. in raw water are oxidized and decomposed by aerobic bacteria in an aerobic atmosphere and a nitrogen compd. is oxidized to nitrogen oxide. The nitration soln. from which nitrogen is removed is separated into sedimented sludge and supernatant water in a sedimentation tank 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a denitrification treatment device for denitrifying organic wastewater containing nitrogen compounds such as human waste, sewage, food wastewater and various industrial wastewater.

[0002]

2. Description of the Related Art Conventionally, an organic wastewater containing a nitrogen compound such as ammonia is biologically decomposed with an organic substance such as BOD and COD components by using an aerobic and anaerobic biological treatment apparatus. Denitrification treatment of nitrogen compounds is also performed at the same time.

As the above-mentioned biological treatment apparatus, a nitrification tank which biologically oxidizes nitrogen compounds in waste water in an aerobic state to produce nitrogen oxides, and the produced nitrogen oxides in an anaerobic state are biologically treated. A device provided with a denitrification tank for reducing and removing as nitrogen gas is generally implemented, and as one of the devices, while circulating the nitrification liquid of the nitrification tank in the denitrification tank,
There is a circulation denitrification treatment device that supplies raw water of organic wastewater to perform denitrification treatment.

As shown in FIG. 2, the above-mentioned circulation denitrification treatment apparatus uses a carbon source and a hydrogen donor for maintaining the biological activity of anaerobic bacteria such as denitrifying bacteria in the denitrification tank 1 in the organic wastewater. The raw water is supplied from the raw water supply passage 9 to the denitrification tank 1 and the nitrification solution 3 to 6 times as much as the raw water is extracted by the nitrification solution circulation pump 6, and the denitrification tank is passed through the nitrification solution circulation path 14. 1 to remove nitrogen oxides such as nitric acid and nitrite in the nitrification solution as nitrogen gas by biological reduction, and then remove the denitrification solution from the overhead such as overflow. Is a device for introducing a nitrogen compound such as ammonia in raw water from the denitrification liquid circulation inlet 12 into the nitrification tank 2 for nitrification treatment.

Further, the nitrification tank 2 is placed in an aerobic atmosphere in order to maintain the biological activity of aerobic bacteria such as nitrifying bacteria, and oxygen for maintaining aerobic conditions is obtained by using a suitable air diffuser for a large amount of air. Although it is generally supplied, an oxygen-rich gas supplying device is often used from the viewpoints of reducing power consumption, tank installation area, and improving processing efficiency by high-load processing.

Further, in the method of supplying the oxygen-rich gas, as shown in FIG. 2, the circulation pump 3 draws 3 to 6 times as much nitrification liquid from the nitrification tank 2, and the oxygen is mixed in the oxygen mixing device 4 such as a venturi or an ejector. A method is used in which a rich gas is mixed and dissolved in a nitrification solution and is circulated to the nitrification tank 2 through a nitrification solution circulation channel 13.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the conventional denitrification treatment apparatus using the above oxygen-rich gas for supplying oxygen to the nitrification tank,
While circulating 3 to 6 times the nitrification solution of raw water from the nitrification tank to the denitrification tank, circulating 3 to 6 times the nitrification solution in the nitrification tank 2 to mix and dissolve oxygen-rich gas and stir the nitrification tank. Therefore, the equipment cost and the power cost have not been sufficiently reduced, and further reduction thereof has been desired.

Therefore, according to the present invention, when the nitrogen compounds in the organic wastewater are oxidized by using the oxygen-rich gas and the generated nitrogen oxides are reduced and removed as nitrogen gas, the nitrification solution is circulated in the denitrification tank to remove the nitrogen. This is intended for the purpose of reducing equipment costs and power costs in a circulating denitrification treatment apparatus for performing nitrogen treatment.

[0009]

Means for Solving the Problems The gist of the present invention for achieving the above object is to supply an oxygen-rich gas to make it aerobic, and to biologically oxidize nitrogen compounds in organic wastewater to produce nitrogen. A nitrification tank that uses an oxide and a denitrification tank that biologically reduces nitrogen oxides in an anaerobic state and removes it as nitrogen gas, and a nitrification solution circulation channel that circulates the nitrification solution in the nitrification tank to the denitrification tank. In the circulating denitrification treatment device equipped with the above, a circulation pump for extracting the denitrification liquid from the denitrification tank and an oxygen mixing device for mixing the oxygen-rich gas with the denitrification liquid are arranged to circulate the oxygen-dissolved denitrification liquid to the nitrification tank An oxygen aeration-type denitrification treatment apparatus comprising: a denitrification liquid circulation flow path and a nitrification liquid circulation inlet for flowing the nitrification liquid from the nitrification tank into the denitrification tank with a head difference.

[0010]

[Function] The nitrification solution circulated by a head difference from the nitrification tank through the nitrification solution circulation inlet into the denitrification tank is used to maintain the biological activity of facultative anaerobic bacteria such as denitrifying bacteria in organic matter in raw water in an anaerobic atmosphere. Used as a carbon source and hydrogen donor for BOD, COD
Along with the oxidative decomposition of the components, nitrogen oxides such as nitric acid and nitrite in the nitrification solution are reductively decomposed and discharged as nitrogen gas.

The denitrification liquid subjected to the denitrification treatment is supplied from the denitrification tank to the nitrification tank through the denitrification liquid circulation passage, and the remaining organic substances and nitrogen compounds are aerobic organisms such as nitrifying bacteria in an aerobic atmosphere. The nitrogen compounds such as ammonia are oxidized into nitrogen oxides such as nitric acid and nitrite in addition to being oxidatively decomposed by biological action.

Further, the denitrification liquid in the denitrification tank is extracted from the denitrification liquid circulation channel by a circulation pump, and the oxygen-rich gas is mixed and dissolved in the oxygen mixing device and then circulated to the nitrification tank, whereby The aerobic atmosphere inside is maintained and agitation is performed to enhance the biological activity of aerobic bacteria such as nitrifying bacteria.

Therefore, conventionally, oxygen is dissolved in 3 to 6 times the nitrification solution of raw water and circulates in the nitrification tank, and 3 to 6 times the nitrification solution of the raw water is removed using another channel and pump. Since it was circulated in the nitrification tank, power costs and the like were high, but in the oxygen aeration type denitrification treatment device of the present invention, the nitrification solution is circulated to the denitrification tank by a head difference to dissolve oxygen in the denitrification solution. Since it is circulated to the nitrification tank, the power cost can be reduced.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram of an oxygen aeration type denitrification treatment device according to an embodiment of the present invention, and FIG. 2 is a system diagram of a conventional oxygen aeration type denitrification treatment device. The same reference numerals are used for corresponding members in both drawings.

In FIG. 1, reference numeral 1 denotes a gas discharge channel 2 at the upper part.
0, the raw water supply flow passage 9 of the organic waste water and the return sludge circulation flow passage 15 are connected, and the denitrifying liquid circulation passage 11 for oxygen mixing is provided at the bottom.
2 is a closed structure denitrification tank, 2 is connected to a nitrification solution discharge passage 17 for discharging the nitrification solution at the upper part, a liquid injection device 5 for oxygen mixed denitrification solution is arranged at the bottom part, and the upper surface is opened. Although this is a nitrification tank, the main tank may have a closed structure.

The denitrification tank 1 and the nitrification tank 2 may be provided separately, but it is preferable to provide them adjacently in order to reduce the installation area, and the nitrification liquid flows from the nitrification tank 2 into the denitrification tank 1 by a water head difference. In order to do so, the nitrification liquid circulation inlet 10 is provided.

The nitrification liquid circulation inlet 10 is arranged so that the liquid surface on the side of the nitrification tank 2 is kept higher than the liquid surface on the side of the denitrification tank 1 so that the nitrification liquid flows in at a head difference. Although an opening may be provided only in the partition between the nitrification tank 2 and the nitrification tank 2, it is preferable that the opening be inflowed by an overflow, and the inflow port 10 is an overflow tube in the nitrification tank 2. It may be arranged in the above or may be attached to the outside as a gutter.

Further, a flow rate adjusting device such as a metering valve is provided in the nitrification solution discharge passage 17, and the nitrification solution circulation flow rate and the nitrification solution discharge flow rate are adjusted to a predetermined amount, and the liquid level of the nitrification tank 2 is adjusted. It is preferable to adjust the circulation amount of the nitrification liquid to the denitrification tank 1 by adjusting

The denitrification liquid circulation passage 11 has a circulation pump 3 for extracting the denitrification liquid from the denitrification tank 1 and an oxygen mixing device 4 for mixing and dissolving oxygen-rich gas into the denitrification liquid, and the nitrification tank Two
It is connected to the liquid ejecting apparatus 5 arranged at the bottom of the.

The oxygen mixing device 4 may be any device capable of mixing and dissolving a gas in a liquid, but like a venturi or an ejector, the gas is sucked at a reduced pressure generated by injecting the liquid and a strong turbulent flow is generated. A device for mixing and dissolving gas in a liquid is preferable from the viewpoint of oxygen dissolution efficiency, and the liquid injection device 5 has a plurality of injection nozzles horizontally arranged so as to inject the liquid in the horizontal direction. It is not limited to

The oxygen-rich gas supplied to the oxygen mixing device 4 may be pure oxygen gasified from liquid oxygen or concentrated oxygen obtained by adsorbing and separating nitrogen from air by a PSA device to concentrate oxygen. It is preferable to use pure oxygen in terms of downsizing of equipment, reduction of power cost, oxygen dissolution efficiency and the like.

Reference numeral 7 is a settling tank for settling and separating the sludge in the nitrification solution. A treated water discharge channel 18 for discharging the supernatant liquid as treated water is connected to the upper part, and the settling sludge is drawn out by a sludge extraction pump 8 to the bottom part. The excess sludge discharge flow channel 16 for discharging a part of the excess sludge is branched, and the return sludge supply flow channel 15 for circulating the remaining sludge to the denitrification tank 1 is connected.

The operation of the oxygen aeration type denitrification treatment apparatus having the above construction will be described below. The nitrification liquid that has flowed into the denitrification tank 1 from the nitrification tank 2 through the nitrification liquid circulation inlet 10 with a head difference is
Utilizing the organic matter in the raw water of the organic wastewater supplied from the raw water supply channel 9 in an anaerobic atmosphere as a carbon source and a hydrogen donor for maintaining the biological activity of facultative anaerobic bacteria such as denitrifying bacteria,
Organic substances in the raw water are biologically oxidatively decomposed, and nitrogen oxides in the nitrification solution are reduced as nitrogen gas and discharged from the gas discharge passage 20.

The denitrification liquid is passed from the denitrification tank 1 to the denitrification liquid circulation passage 11
After being extracted by the circulation pump 3 and mixed and dissolved by the oxygen mixing device 4 with the oxygen-rich gas, it is supplied from the liquid injection device 5 to the nitrification tank 2, and the remaining organic substances and nitrogen compounds in the raw water are nitrified in an aerobic atmosphere. While being oxidatively decomposed by the biological action of aerobic bacteria such as bacteria, nitrogen compounds such as ammonia are oxidized to nitrogen oxides such as nitrate and nitrite.

As the oxygen mixing device 4, a device such as a venturi or an ejector that sucks gas at a reduced pressure generated by jetting the liquid and mixes and dissolves the gas in the liquid with strong turbulence is used. Since the dissolution efficiency can reach 90 to 95%, the power cost is low and high load treatment is possible.

The nitrification liquid from which nitrogen has been removed is in the nitrification liquid discharge channel 1
7 is introduced into the settling tank 7, separated into settling sludge and supernatant water, and the supernatant water is discharged as treated water from the treated water discharge channel 18 to the outside of the system, and the settled sludge is extracted by the sludge extraction pump 8. A part of the sludge is circulated to the denitrification tank 1 through the return sludge circulation flow path 15, and the rest is discharged from the system as excess sludge through the excess sludge discharge flow path 16.

In the above denitrification treatment, the NH ₄ -N volume load in the nitrification tank 2 is usually 0.4 to 2 kgN / m.
Operated at ³ · D, also the supply amount of the circulating amount or the oxygen rich gas denitrified liquid is nature and N of an organic waste water to be processed is controlled by the BOD volume load, and the like.

[0028]

INDUSTRIAL APPLICABILITY The present invention relates to a circulating denitrification treatment apparatus which uses an oxygen-rich gas for supplying oxygen to a nitrification tank, and has 3 to 6 raw water.
Since the circulation pump and the circulation flow path for circulating the double nitrification liquid from the nitrification tank to the denitrification tank are not necessary, the equipment cost and the power cost can be further reduced.

[Brief description of drawings]

FIG. 1 is a system diagram of an oxygen aeration type denitrification treatment apparatus according to an embodiment of the present invention.

[Fig. 2] System diagram of a conventional oxygen aeration-type denitrification treatment device

[Explanation of symbols]

 1: Denitrification tank 2: Nitrification tank 3: Circulation pump 4: Oxygen mixing device 5: Liquid injection device 6: Nitrification liquid circulation pump 7: Settling tank 8: Sludge extraction pump 9: Raw water supply flow passage 10: Nitrification liquid circulation inlet 11: Denitrification liquid circulation flow passage for oxygen mixing 12: Denitrification liquid circulation inlet 13: Nitrification liquid circulation passage for oxygen mixing 14: Nitrification liquid circulation passage 15: Return sludge circulation passage 16: Excess sludge discharge Flow path 17: Nitrifying solution discharge flow path 18: Treated water discharge flow path 19: Oxygen-rich gas supply flow path 20: Gas discharge flow path

Claims (1)

[Claims] 1. An oxygen-rich gas is supplied to bring it into an aerobic state,
A nitrification tank that biologically oxidizes nitrogen compounds in organic wastewater to nitrogen oxides, and a denitrification tank that biologically reduces nitrogen oxides in an anaerobic state to remove as nitrogen gas, In a circulation denitrification treatment device equipped with a nitrification solution circulation channel that circulates the nitrification solution from the nitrification tank to the denitrification tank, a circulation pump that extracts the denitrification solution from the denitrification tank and an oxygen mixture that mixes oxygen-rich gas with the denitrification solution A denitrification liquid circulation flow path for circulating the oxygen-dissolved denitrification liquid to the nitrification tank and a nitrification liquid circulation inlet for flowing the nitrification liquid from the nitrification tank to the denitrification tank with a head difference are provided. An oxygen aeration type denitrification treatment device.