JP2001017992A - Biological nitrification and denitrification method for night soil, or the like - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to adequately control both of a nitrification stroke and denitrification stroke in accordance with a standard by making the time ratio of one batch of both strokes constant with a single tank, admitting sewage during the denitrification stroke and increasing or decreasing an aeration air quantity in such a manner that an oxidation reduction potential inflection point appears before the start of the next nitrification stroke. SOLUTION: The sewage is admitted into the single nitrification and denitrification tank 1 and is subjected alternately to the nitrification stroke by aeration and the denitrification stroke by agitation. Previously, the nitrification and denitrification strokes of one batch and one cycle are set at about one hour to execute the nitrification stroke for about 15 minutes and the denitrification stroke for about 45. When the sewage is admitted for about 5 minutes from the start, the oxidation reduction potential(ORP) value falls rapidly from about 130 mV to around 0 mV and the ORP inflection point appears before around 5 minutes upon the end of the denitrification after the slowness of the value, then falls to about -200 mV. The ORP value rapidly ascends to near about 130 mV again when the next nitrification stroke starts. The aeration air quantity is increased and decreased in such a manner that the ORP inflection point appears during the time before 5 minutes to just before the start of the nitrification stroke.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for the biological nitrification and denitrification of wastewater such as night soil, sewage, garbage and industrial wastewater.
More specifically, in a single tank, nitrogen and phosphorus are removed from the wastewater by alternately repeating a nitrification step under aerobic conditions and a denitrification step under anaerobic conditions. is there.

[0002]

2. Description of the Related Art Conventionally, when a nitrification step and a denitrification step are alternately performed in a single tank, both steps are performed by an ORP (redox potential) meter and a DO (dissolved oxygen concentration) meter attached to the single tank. And by using a pH meter or the like to comprehensively judge each measured value.

[0003]

However, the above O
When comprehensively judging RP, DO, pH, etc., each of the above measurement values changes in the nitrification and denitrification processes with the change in the properties of the inflow sewage. It is practically difficult to make a proper judgment and to always advance both processes appropriately, so that the nitrification and denitrification treatment has not been performed efficiently.

An object of the present invention is to alternately perform a nitrification step and a denitrification step in a single tank, and always appropriately advance both the steps based on one specific criterion, that is, an ORP inflection point. An object of the present invention is to provide a biological nitrification and denitrification method capable of easily following the change in the properties of incoming sewage.

[0005]

SUMMARY OF THE INVENTION The present invention is a biological nitrification and denitrification method in which sewage such as urine flows into a single tank, and alternately performs a nitrification step by aeration and a denitrification step by stirring. 1. The time ratio between the nitrification step and the denitrification step in one batch is kept constant, sewage flows into the denitrification step, and the aeration air volume is increased or decreased so that an ORP inflection point appears before the next nitrification step starts. It is characterized by the following.

That is, according to the present invention, the time of the nitrification step and the time of the denitrification step are set to a fixed time in advance, and the ORP value increases in the nitrification step within the determined one cycle time, thereby denitrification. Paying attention to the fact that the ORP value decreases in the process, in the denitrification process, O is increased before the next nitrification process starts.
By increasing or decreasing the amount of aeration air so that the RP inflection point appears, efficient nitrification denitrification is enabled.

[0007] In terms of treatment efficiency, the increase or decrease in the amount of aeration air depends on the ORP from 5 minutes before the start of the nitrification process to immediately before.
It is preferable to perform it so that an inflection point appears.

Further, in the present invention, the inflow timing and inflow time of the sewage in the denitrification process are not particularly limited, and the sewage may be continuously introduced during the denitrification process, or only during a certain time in the denitrification process. Although it may be allowed to flow in as much as possible, in terms of processing efficiency, it is preferable to flow in a short time of about 5 minutes from the start of the denitrification step.

In the present specification, one batch refers to one treatment of a fixed amount of sewage, and one cycle refers to a combination of a nitrification step and a denitrification step. And
Usually, one batch process is performed in one cycle, but one batch process may be performed in a plurality of cycles.

[0010] The time of one batch is preferably in the range of 20 minutes to 6 hours. If it is shorter than 20 minutes, sufficient nitrification and denitrification cannot be performed in time, and if it exceeds 6 hours, it takes a long time to complete nitrification and denitrification, and the treatment efficiency is extremely low. Because it becomes. In addition, in order to perform sufficient nitrification and denitrification and maintain the processing efficiency to some extent, it is preferable to set the time of one batch to a range of 0.5 to 2 hours. Further, since the denitrification step usually takes longer than the nitrification step, the time of the denitrification step in one cycle is set to be equal to or longer than the time of the nitrification step.

In the present invention, the nitrification and denitrification treatment in a single tank is in principle. However, the secondary nitrification and denitrification is performed by flowing the processing liquid from the single tank into the secondary tank as required. Sometimes.

As described above, the ORP value increases during the nitrification process and decreases during the denitrification process. However, the present invention uses the ORP inflection point at the end of the denitrification process as the sole reference to determine the aeration air volume. Since it is to be increased or decreased, within one batch time set in advance, after a sufficient denitrification step is performed, a nitrification step is started, and efficient nitrification denitrification becomes possible, and The increase or decrease of the aeration air volume is determined by the ORP from 5 minutes before the nitrification process to immediately before.
In the case where the inflection point appears, the nitrification step is started immediately after the sufficient denitrification step is performed, so that the nitrification denitrification can be performed more efficiently.

The above-mentioned ORP inflection point is usually recognized when the ORP value starts to drop sharply at the end of the denitrification process.

[0014]

Next, embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1] FIG. 1 is a flow sheet of the present embodiment, wherein (1) is a single nitrification denitrification tank, and (2) is a solid-liquid treated water discharged from a nitrification denitrification tank (1). A separating device, (3) a coagulating sedimentation tank for injecting a flocculant into the separated liquid from the solid-liquid separating device (2) to obtain clear treated water by sedimentation or flotation,
(4) is a sludge treatment facility for treating coagulated sludge discharged from the bottom of the coagulation sedimentation tank (3) and excess sludge discharged from the solid-liquid separator (2). A part of the sludge from the solid-liquid separation device (2) is supplied to the nitrification and denitrification tank (1) as returned sludge.

FIG. 2 is an enlarged view of the nitrification denitrification tank (1). The nitrification denitrification tank (1) has an ORP meter (5) and a DO meter (6).
And a pH meter (7), and a nitrification denitrification tank (1)
Ejector (8) that supplies air or oxygen to the side of
Is provided. Then, air or the like is supplied at the time of aeration, and supply of air or the like is stopped at the time of stirring. However, a small amount of air may be supplied even at the time of stirring in order to increase stirring efficiency.

In addition, the nitrification denitrification tank (1) is provided with a return sludge or concentrated sludge input line (9) and a wastewater inflow line (1) for night soil and the like.
1) and a discharge line (12) are provided.

FIG. 3 shows an example in which the above ejector (8) is used.
An underwater stirrer (13) is arranged at the bottom of the nitrification and denitrification tank (1), and the inside of the tank is stirred by the stirrer (13), and aeration is performed by air supply by a blower (not shown). It has been made like that.

Next, a method for treating sewage containing human waste and septic tank sludge at a ratio of 8: 2 using the above-described apparatuses will be described. First, in the above-mentioned nitrification denitrification tank (1),
When the sewage is introduced and the nitrification step by aeration and the denitrification step by agitation are alternately performed, the time of the nitrification denitrification step of one batch and one cycle is set in advance to one hour, and
Five minutes is a nitrification process, and the remaining 45 minutes is a denitrification process.
In addition, sewage is allowed to flow in 5 minutes from the start of the denitrification process.

As shown in FIG. 4 and Table 1, the nitrification denitrification tank
When sewage is allowed to flow for 5 minutes from the start of the denitrification process in (1), the ORP value drops rapidly from about 130 mV to around 0 mV, then drops slowly, and then ends 5 minutes after the denitrification process The ORP inflection point (C) appears before and the ORP value is 0 mV
It descends rapidly from the vicinity, and about -260 m at the end of the denitrification process
It falls to V. During this time, nitrite nitrogen and nitrate nitrogen are converted and removed into nitrogen gas, and DO at this time is zero.
mg / l.

Next, when the nitrification process is started, the ORP value rapidly rises again to about 130 mV, and gradually rises before the end of the nitrification process. In this case, DO is 1 mg /
1 or more, ammonia nitrogen is removed, and nitrite nitrogen and nitrate nitrogen increase.

[0022]

[Table 1] In the present embodiment, the aeration air flow is increased or decreased so that the ORP inflection point (C) appears between 5 minutes before and immediately before the nitrification process starts. Specifically, as shown in FIG. 5, when the ORP inflection point (C) appears before 5 minutes before the start of the nitrification process, the aeration air volume is increased, and as shown in FIG. If the nitrification process has started without the appearance of the inflection point (C), the aeration air volume is reduced. Also, as shown in FIG. 4, when the ORP inflection point (C) appears between 5 minutes before and immediately before the start of the nitrification process, the aeration air volume is not changed.

As shown in FIG. 7, the adjustment of the aeration air flow is performed by A / D converting the current output (analog value of voltage, current, etc.) of the ORP meter by an A / D converter, and converting the digital value into the digital value. The change (ΔP) of (P) is obtained, and the change (ΔP) and the elapsed time (t) after the start of the denitrification process are input. value
(ΔQ) is added to the reference aeration air volume (Q0) to obtain the current optimal aeration air volume (Q), which is output as an aeration air volume command value (analog value) via a D / A converter, and To automatically control the air volume of the ejector (8) and the blower.

[Embodiment 2] As shown in FIG. 8, in this embodiment, after the nitrification and denitrification treatment in the same nitrification and denitrification tank (1) as in the first embodiment, a secondary nitrification and denitrification tank is further provided. (2
According to 1), secondary nitrification and denitrification treatment is performed.
In the secondary nitrification denitrification tank (21), first, aeration (nitrification) is performed by injecting air, then denitrification is performed by stirring while injecting alcohol, and finally, the alcohol is blown out by injecting air. Things.

The present embodiment is the same as the first embodiment except for the treatment in the secondary nitrification denitrification tank (21). Therefore, in FIG. 8, the same reference numerals as those in the first embodiment denote the same parts. Omitted.

[0026]

The present invention relates to a biological nitrification and denitrification method in which sewage such as urine flows into a single tank and alternately performs a nitrification step by aeration and a denitrification step by stirring. With the ORP inflection point at the end of as the only reference, the inflection point is to increase or decrease the amount of aeration air so that the inflection point appears before the next nitrification process starts. After the denitrification process is performed, the nitrification process is started, enabling efficient nitrification denitrification, and increasing or decreasing the amount of aeration air from 5 minutes before the nitrification process to just before When the ORP inflection point is made to appear, the nitrification step is started immediately after the sufficient denitrification step is performed, so that the nitrification denitrification can be performed more efficiently. Also, as in the conventional case, the ORP value, DO value and pH
Since there is no ambiguity as in the case of comprehensively judging wastewater, the nitrification process and the denitrification process in a single tank can be performed appropriately and easily following the change in the properties of inflow sewage, based on accurate judgment. You.

In addition, the above-described nitrification process under aerobic conditions and the denitrification process under anaerobic conditions are performed alternately and efficiently to remove phosphorus contained in wastewater such as night soil. Will also be done quickly.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing a first embodiment.

FIG. 2 is an enlarged front view of a nitrification denitrification tank.

FIG. 3 is an enlarged front view showing another embodiment of the nitrification denitrification tank.

FIG. 4 is a graph showing an ORP change when an aeration air volume in a nitrification denitrification tank is appropriate.

FIG. 5 is a graph showing an ORP change when the aeration air volume is insufficient.

FIG. 6 is a graph showing an ORP change when an aeration air amount is excessive.

FIG. 7 is a flow sheet showing an embodiment of an aeration air volume calculation process.

FIG. 8 is a flow sheet showing the second embodiment.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kenichi Kamata 4-5-2, Doshumachi, Chuo-ku, Osaka-shi Inside Yamada Kogyo Co., Ltd. (72) Tadahiko Hiramatsu 4-5-22-2, Doshomachi, Chuo-ku, Osaka-shi Yamada Kogyo Co., Ltd. (72) Inventor Koji Hasui 4-5-2, Doshumachi, Chuo-ku, Osaka-shi F-term in Yamada Kogyo Co., Ltd. 4D040 BB08 BB22 BB25 BB92

Claims (5)

[Claims] 1. A biological nitrification and denitrification method in which sewage such as urine flows into a single tank and alternately performs a nitrification step by aeration and a denitrification step by agitation. The method is characterized in that sewage flows into the denitrification process at a constant time ratio with the nitrification process, and the amount of aeration air is increased or decreased so that an ORP inflection point appears before the next nitrification process starts. Biological nitrification denitrification method. 2. An increase or decrease in the amount of aeration air is determined by starting the nitrification process.
The biological nitrification denitrification method according to claim 1, wherein the method is performed so that the ORP inflection point appears between minutes and immediately before. 3. The biological nitrification denitrification method according to claim 1, wherein the time of the denitrification step is longer than the time of the nitrification step. 4. The biological nitrification denitrification method according to claim 1, wherein the nitrification denitrification time of one batch is 20 minutes to 6 hours. 5. The biological nitrification denitrification according to claim 1, wherein the treatment liquid discharged from the single tank is flowed into the secondary tank to perform secondary nitrification denitrification. Nitrogen method.