JPH05277487A - Deodorizing method for odorous gas in anaerobic treatment - Google Patents

Abstract

PURPOSE:To make it possible to deodorize an odorous gas generated in anaerobic treatment stably and with high efficiency by providing a simple device and operating it. CONSTITUTION:Untreated water, water in the process of anaerobic treatment or anaerobic treated water 11 is conducted to a deodorizing tank 5, so that the water is mixed with microbes in the tank, then an odorous gas 14 generated in the anaerobic treatment is bleeded into the deodorizing tank 5 with air for aerobic treatment, in a method for anaerobic treatment of organic drained water. The water conducted into the deodorizing tank 5 is allowed to run in a single pass so that its held time in the deodorizing tank 5 lasts for more than one day.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for deodorizing odorous gas generated in anaerobic treatment of organic waste water.

[0002]

BACKGROUND ART Anaerobic treatment has been attracting attention as an energy-saving treatment method for organic waste water. This method is a method of decomposing organic matter by anaerobic treatment consisting of an acid-producing phase by an acid-producing bacterium and a methanogenic phase by a methanogenic bacterium. Especially the UASB (Upstream Sludge Blanket) method,
The fluidized bed method and the like can maintain a high concentration of microbial groups centering on methanogens in the reaction tank, so that the treatment efficiency is high,
It can be operated with a volume load of 5 to 10 times that of aerobic treatment of activated sludge and is widely used mainly for food wastewater.

However, the anaerobic treatment does not supply air,
Since it is performed in an anaerobic atmosphere, an odor is generated. The main components of the odor are an organic acid odor generated in the acid generation phase and a hydrogen sulfide odor generated in the methanation phase, and if this leaks to the outside, it causes odor pollution. Therefore, the treatment tank is covered with a cover to suck the odorous gas so that the odorous gas does not leak to the outside, and the odorous gas sucked is deodorized by chemical cleaning or activated carbon treatment.

On the other hand, Japanese Examined Patent Publication No. 62-38015 discloses a method of contacting the produced methane gas with activated sludge in aerobic treatment in order to remove hydrogen sulfide contained in the methane gas produced in the methane production phase. There is. This method is a method in which hydrogen sulfide is absorbed in activated sludge to grow hydrogen sulfide-utilizing bacteria in the activated sludge and desulfurize.

Such a method can be applied to the deodorization of the odorous gas sucked from the apparatus in addition to the produced methane gas. The aerobic method is installed separately from the anaerobic treatment or as a post-treatment of the anaerobic treatment. It is also possible to introduce odorous gas into the treatment device and bring it into contact with activated sludge to deodorize it.

When there is an aerobic treatment device near the anaerobic treatment device as described above, the odorous gas can be deodorized just by introducing it into the aerobic treatment device and blowing it in, but the anaerobic treated water is discharged to the sewage. As in the case, when there is no aerobic treatment device nearby, a separate odor gas treatment facility is required. However, it is uneconomical to install an activated sludge treatment device dedicated to odor treatment as an aerobic treatment device because an aeration tank, a sedimentation tank, a sludge return pump and the like are required.

If the anaerobic treated water is simply passed through the aeration tank without returning the activated sludge, the activated sludge will flow out, so that the cells necessary for the aerobic treatment cannot be retained. It cannot be deodorized by blowing in odorous gas. In addition, even if the activated sludge of the aerobic treatment device is placed in a deodorizing tank and odorous gas is blown into the deodorizing tank, the deodorizing can be performed at first, but the pH gradually lowers and the deodorizing ability decreases, and the deodorizing cannot be performed.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to solve such problems and to deodorize odorous gas generated in anaerobic treatment stably and efficiently by a simple device and operation. It is to propose a method of deodorizing odorous gas that can achieve the above.

[0009]

The present invention relates to a method for anaerobically treating organic waste water, in which at least a part of raw water, anaerobic treated water or anaerobic treated water is introduced into a deodorizing tank, Aerobic treatment is performed by aerating the odorous gas generated in the anaerobic treatment together with air into the deodorizing tank, and the water introduced into the deodorizing tank has a residence time of 1 day or more in the deodorizing tank. It is a method for deodorizing odorous gas in anaerobic treatment, which is characterized in that water is temporarily passed.

In the present invention, the organic waste water to be subjected to the anaerobic treatment is not limited as long as it contains organic substances and can be treated anaerobically. Such wastewater includes beer wastewater, sugar wastewater, starch wastewater and other food wastewater, paper pulp wastewater and other industrial wastewater, as well as sewage, night soil, sludge, or wastewater obtained by treating these.

The anaerobic treatment system may be either a two-phase system in which the acid-producing phase and the methane-producing phase are separated, or a one-phase system in which these two phases are carried out in one tank. As the method of anaerobic treatment, a UASB method, a fluidized bed method, or any other method can be adopted.

The odorous gas to be treated in the present invention is an odorous gas generated in such an anaerobic treatment, and the entire treatment apparatus or individual apparatuses constituting the treatment apparatus are covered with a cover, and the inside is blower, Obtained by sucking with a fan. Although the treatment device may be a single tank, it is usually composed of a raw water conditioning tank, an acid production tank, a methane production tank, a treated water tank and the like.

As an odor component, an odor mainly produced by an organic acid odor due to an organic acid and its ester is generated in the raw water adjusting tank and the acid producing tank. In the methane production tank and the treated water tank, the odor of organic acids is small when the treatment is successful,
Hydrogen sulfide causes a hydrogen sulfide odor and an ammonia odor, and depending on the concentration of sulfate ions in the raw water, the hydrogen sulfide concentration may reach several thousands ppm. When the treatment of the methane production tank is not successful, an organic acid odor is generated here as well.

The odorous gas to be treated in the present invention contains these, and the odorous gas generated in each part may be sucked separately and treated separately, or may be treated in a mixed state. .. These odorous gases can be obtained by covering each or the entire device with a cover and sucking it in,
At this time, it is obtained in a state where air is also mixed in by suction.

In the present invention, in order to deodorize these odorous gases, a deodorizing tank is provided to grow microorganisms, and raw water, water in the middle of anaerobic treatment or anaerobic treated water (hereinafter referred to as anaerobic (Sometimes called treated water) to introduce aerobic treatment. Microorganisms may be naturally grown by aerobically treating anaerobic treated water or the like, but it is preferable to transfer activated sludge from another aerobic treatment device and inoculate it first.

The capacity of the deodorizing tank may be the size necessary for deodorizing odorous gas, and it generally depends on the type of raw water, the conditions of anaerobic treatment, the structure of the apparatus, etc., but generally the CODcr 1TN to be treated.
On the other hand, the size is about 1 to ³⁰ m ^3, and the anaerobic treated water to be introduced has a residence time of 1 day or more, preferably 1 to 10 days.

The amount of anaerobic treated water or the like introduced into the deodorizing tank may be the amount necessary for deodorizing odorous gas, and is generally about (1/10000) to (1/10) of the entire treated water. The anaerobic treated water or the like is introduced into the deodorizing tank and mixed with the activated sludge in the tank so that the residence time is the above-mentioned retention time (1 day or more, preferably 1 to 10 days).

In this state, the odorous gas is aerated together with air in a deodorizing tank to perform a complete mixing type aerobic treatment to deodorize the odorous gas. If the anaerobic treatment device has a high degree of airtightness and the amount of air in the odorous gas is small, it is necessary to mix air separately, but generally a large amount of air is mixed by suction, so more air is mixed. It is often unnecessary to do this. Aeration amount in deodorization tank is 5 to 50 hours as SV
It is preferably about r ⁻¹ .

When anaerobic treated water or the like introduced into the deodorizing tank is passed by a transient method so that the retention time is reached and a complete mixing type aerobic treatment is carried out, sludge in the tank is Microorganisms that aerobically oxidize and decompose organic substances such as organic acids and sulfides such as hydrogen sulfide and ammonia that remain in anaerobic treated water or that are contained in odorous gas grow, resulting in odorous gas. The odor component of is removed.

In the present invention, the residence time of the anaerobic treated water or the like in the deodorizing tank is set to 1 day or more, whereby the microorganisms which decompose the components in the anaerobic treated water or the odorous gas can be grown, and the transient Even in the case of the formula, the deodorization tank can hold the amount of microorganisms necessary for decomposing components in the anaerobic treated water and the odorous gas.

As described above, the anaerobic treated water or the like is passed through for a long residence time to perform the complete mixing type aerobic treatment.
The deodorization tank functions as a kind of chemostat-type reaction tank, and the components in the anaerobic treated water and the odorous gas are efficiently taken up by the microorganisms for deodorization.

The sludge containing the microorganisms that grow here lacks the sedimentation property of general activated sludge and is retained in the liquid in a floating state. Also, the bacterial cell concentration is significantly lower than that of the activated sludge method. On the other hand, the odor component in the odor gas is a substance with a high odor concentration even if the substance concentration is low, that is, a substance with a low threshold, so the absolute amount contained in the gas is small,
If it is dissolved in a liquid, it is easily assimilated by the floating microorganisms.

When only the sludge is put in the deodorizing tank and the odorous gas is aerated without supplying the anaerobic treated water or the like, the pH is lowered as described above and the deodorizing ability is lost, but the anaerobic treated water or the like is supplied. By aeration and aeration, the microbial cells are maintained, pH is buffered, and nutrients such as nitrogen and phosphoric acid are supplemented, whereby deodorizing performance can be maintained.

In the treated liquid flowing out of the deodorizing tank, organic substances and odorous components of the liquid are removed by microorganisms, but the microorganisms themselves remain as sludge in a floating state in the liquid. Although this sludge has poor separability, it does not need to be returned, so it can be discharged as it is together with the anaerobic treated water or separately from the anaerobic treated water. If there is a post-treatment step, it can be transferred to the post-treatment step.

[0025]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is a flowchart showing the anaerobic treatment apparatus of the embodiment. In the figure, 1 is a raw water conditioning tank, 2 is an acid production tank, 3 is a methane production tank, 4 is a treated water tank, and 5 is a deodorization tank.

In the treatment by the above-mentioned anaerobic treatment apparatus, raw water 6 is introduced into the raw water adjusting tank 1, and from there, it is sequentially sent to the acid producing tank 2 and the methane producing tank 3 to perform the anaerobic treatment. In the acid production tank 2, it is decomposed into organic acid by the action of acid-producing bacteria. In the methanogenic tank 3, it is decomposed into methane and carbon dioxide by the action of methanogenic bacteria. The methane gas produced here is
The produced gas 7 is taken out, desulfurized, and then sent to a gas holder (not shown). The anaerobic treated water 8 is introduced into the treated water tank 4, and most of the treated water 9 is discharged to the sewer as the treated water 9 or sent to the post-treatment device.

In the deodorization tank 5, microorganisms are allowed to grow,
Anaerobic treated water 11 is introduced from the treated water tank 4 by the pump 10 and mixed with microorganisms. On the other hand, the raw water tank 1, the acid production tank 2, the methane production tank 3 and the treated water tank 4 have a structure covered with a cover, each of which is sucked by a blower 13 through an intake pipe 12 and is introduced into the deodorization tank 5 as an odorous gas 14 containing air. Introduce and ventilate, complete mixing aerobic treatment, and deodorize. The anaerobic treated water 11 is passed through temporarily with a residence time of one day or longer, overflows as treated water 15, and is discharged.

In the above treatment apparatus, the waste water of the beer factory was used as raw water and the methane production tank 4 was used as 1.5 m ³
The UASB tank of was adopted and anaerobic treatment was performed. As the deodorizing tank 5, a tower having a capacity of 212 liters is used, and a raw water adjusting tank 1, an acid producing tank 2, a methane producing tank 3, and a treated water tank 4 are used.
The odorous gas 14 sucked in from the space of 0.1 Nm ³ / m
It was deaerated by aeration with in.

Initially, when the activated sludge transferred from the aerobic treatment device was introduced into the deodorization tank 5 and deodorization was performed without supplying the anaerobic treated water 11, the pH in the tank was lowered and the deodorization efficiency was improved. Fell. Therefore, the activated sludge was replaced and the odor was similarly removed, but the same phenomenon occurred again.

Therefore, from the 104th day onward, the anaerobic treated water 11 is passed from the treated water tank 4 to the deodorizing tower at a supply amount of 40 to 60 liters / day, and is completely mixed with a residence time of 3.5 to 5.3 days. Was discharged by a transient method, the pH of the deodorizing tank 5 was stable, and the deodorizing effect was also stable.

2 and 3 show changes in the odor concentrations of the odorous gas and the treated gas and the pH of the deodorizing tank 5 during the above test. In FIG. 3, A and B show the time when the activated sludge was replaced, and C shows the time when the supply of the anaerobic treated water was started.

From the above results, it can be seen that by supplying anaerobic treated water to the deodorizing tank and performing aerobic treatment with a residence time of 1 day or longer, microorganisms in the deodorizing tank can be maintained and stable and efficient deodorization can be achieved.

[0033]

As described above, according to the present invention, anaerobic treated water or the like is introduced into a deodorizing tank to be mixed with microorganisms in the tank, and odorous gas is aerated to perform aerobic treatment and deodorize. Therefore, the odorous gas generated in the anaerobic treatment can be stably and efficiently treated with a simple device and operation.

[Brief description of drawings]

FIG. 1 is a flow chart showing an anaerobic treatment apparatus of an embodiment.

FIG. 2 is a graph of odor concentration showing test results of Examples.

FIG. 3 is a pH graph showing the test results of Examples.

[Explanation of symbols]

 1 Raw water tank 2 Acid production tank 3 Methane production tank 4 Treated water tank 5 Deodorization tank 10 Pump 13 Blower

Claims (1)

[Claims] 1. A method of anaerobically treating organic wastewater, wherein at least a part of raw water, water in the course of anaerobic treatment or anaerobic treated water is introduced into a deodorizing tank and mixed with microorganisms in the tank to obtain the anaerobic gas. The odorous gas generated in the deodorizing treatment is aerated with the air to the deodorizing tank for aerobic treatment, and the water introduced into the deodorizing tank is a one-time passage so that the residence time in the deodorizing tank is one day or more. A method for deodorizing odorous gas in anaerobic treatment, which comprises: