JP2010082541A - Method for inhibiting odor of wastewater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently inhibit odor generation by sulfate-reducing bacteria in wastewater treatment equipment. <P>SOLUTION: The generation of hydrogen sulfide by the sulfate-reducing bacteria in the wastewater treatment equipment is efficiently inhibited by adding micronanobubble-containing water to wastewater. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wastewater odor control method. In particular, the present invention relates to a method for suppressing odor by suppressing the growth of sulfate-reducing bacteria in wastewater treatment facilities using micro-nano bubble water comprising micro-nano bubbles.

In recent years, environmental regulations are becoming stricter, and accordingly, demands for wastewater treatment technology and facilities are also increasing.
As a method of removing insoluble solid (Suspended Solid: SS) in waste water by sedimentation separation, a coagulation precipitation process using a flocculant, a simple precipitation process using natural sedimentation, and the like are known. At present, a coagulation sedimentation process using a clarifier or the like is common, but a simple sedimentation tank may be used due to cost problems.

  In general, a simple sedimentation tank does not have a device for extracting sludge from the bottom of the tank, so it is necessary to pull up the sludge with a pump or the like. However, since the sludge pull-up frequency is limited, sludge accumulates at the bottom of the tank, and an anaerobic state (a state without oxygen) is likely to occur. Therefore, when sulfate ions or sulfite ions are present in the waste water, sulfate-reducing bacteria grow and hydrogen sulfide is generated, and odor is generated. As measures against hydrogen sulfide gas in wastewater treatment facilities that are prone to anaerobic conditions due to sludge accumulation, etc., it is conceivable to avoid anaerobic conditions by periodically cleaning and stirring the tank or sending in air. Development of a method that is low in cost effectiveness and that effectively suppresses the generation of hydrogen sulfide by sulfate-reducing bacteria is desired.

  By the way, in recent years, a technique using very fine bubbles (ultrafine bubbles) such as microbubbles and nanobubbles has attracted attention. Microbubbles and nanobubbles are considered to have unique physicochemical properties that are not found in millibubbles (bubbles with a diameter of 1 mm or more), and application to soil improvement, food processing, and the like is being studied. A nanobubble is a bubble having a nano-level (1 to 1000 nm) diameter and basically has a negative charge, and therefore adsorbs to a positive charge. A microbubble is a bubble having a micro-level (1-1000 μm) diameter.

Patent Document 1 (Japanese Patent Laid-Open No. 2007-31830) discloses that odorous components (volatile organic compounds) in exhaust gas can be decomposed and removed by activating aerobic microorganisms in washing water using micro-nano bubbles. Are listed. However, this method is only a technique for aerobic microorganisms.
JP 2007-31830 A

  An object of the present invention is to efficiently suppress the generation of odor due to sulfate-reducing bacteria in wastewater treatment facilities.

  As a result of intensive research to solve the above-mentioned problems, the present inventors efficiently suppress the generation of hydrogen sulfide by sulfate-reducing bacteria in wastewater treatment facilities by adding water containing micro-nano bubbles to wastewater. We found what we could do and completed the present invention.

The present invention includes, but is not limited to, the following inventions.
(1) A method for controlling odor of wastewater in wastewater treatment equipment, comprising adding water containing micro / nano bubbles to wastewater to suppress the growth of sulfate-reducing bacteria.
(2) The odor control method according to (1), wherein water containing micro / nano bubbles is produced from waste water.
(3) The odor suppression method according to (1) or (2), wherein the micro / nano bubbles are micro / nano bubbles of oxygen gas or ozone gas.
(4) The odor suppression method according to any one of (1) to (3), wherein the wastewater treatment facility is a simple sedimentation tank.

  According to the present invention, the growth of sulfate-reducing bacteria in the drainage facility can be suppressed, and the generation of odor components such as hydrogen sulfide can be prevented. Odor generation by sulfate-reducing bacteria occurs when sulfate ions or sulfite ions are converted to hydrogen sulfide in an anaerobic state. However, according to the present invention, an aerobic state (a state where oxygen is present) is more efficiently maintained. Since an anaerobic state can be avoided, it is thought that the odor resulting from sulfate-reducing bacteria can be suppressed.

  In one aspect, the present invention is a method for controlling odor of wastewater in a wastewater treatment facility, comprising suppressing the growth of sulfate-reducing bacteria by adding water containing micro / nano bubbles to wastewater. ADVANTAGE OF THE INVENTION According to this invention, the odor which contains the hydrogen sulfide which generate | occur | produces on anaerobic conditions by a sulfate reduction bacterium can be suppressed in waste water treatment equipment.

  In the present invention, water containing micro / nano bubbles (micro / nano bubble water) is used. There is no particular limitation on the water used as the raw material for the micro / nano bubble water, and industrial water or tap water from groundwater or rivers can be used, and actual drainage may be used as micro / nano bubble water. When water containing foreign matter such as wastewater is used as a raw material for micro / nano bubble water, considering the effect on the pump, etc. during the production of micro / nano bubble water, those with less foreign matter in water are preferable. You may go. This is because wastewater containing excessively insoluble solid (SS) is likely to be clogged in a pump or the like, and the generation efficiency of micro-nano bubbles may be significantly reduced.

  The micro-nano bubbles of the present invention are fine bubbles in a liquid having a diameter of 100 μm or less, and include micro-level (1 to 100 μm) micro-bubbles and nano-level (less than 1000 nm) nano-bubbles. Micro-nano bubbles are considered to have stronger surface-active action, impact pressure action, oxidation action, and the like than ordinary bubbles of the order of millimeters or more, and their application to various uses is being studied.

  Specifically, the surface-active action of micro-nano bubbles is an action caused by the large surface area and negative charges of micro-nano bubbles, and dirt and the like having positive charges can be easily adsorbed by micro-nano bubbles, and fibers and Application to cleaning applications such as precision machine parts is expected. The impact pressure action is an action based on the occurrence of a large impact when the micro / nano bubble bursts, and acts on the material around the micro / nano bubble. The oxidation action of micro-nano bubbles is an action based on free radicals generated by micro-nano bubbles.

  Although the details of the mechanism that can suppress the odor from the wastewater by the micro / nano bubble water in the present invention are not clear, the amount of dissolved oxygen is improved by the micro / nano bubble and the anaerobic environment in the drainage facility can be avoided. It is presumed that one factor is that the generation of hydrogen sulfide due to the growth of certain sulfate-reducing bacteria can be suppressed. In particular, micro-nano bubbles can enter even fine parts compared to millimeter-order bubbles, and the time until the bubbles disappear is long, thus effectively avoiding the activity of anaerobic microorganisms such as sulfate-reducing bacteria. be able to.

  The gas constituting the micro / nano bubbles of the present invention is not particularly limited, and air, oxygen gas, ozone gas, or the like can be used. Various gas micro-nano bubbles can be obtained by changing the gas sucked when the micro-nano bubbles are generated. Air is preferable from the viewpoint of availability, but micronano bubbles of oxygen gas or ozone gas are more preferable as will be described later.

  In the present invention, in order to suppress the anaerobic microorganisms in the wastewater treatment facility and suppress the odor of the wastewater, when using the micro-nano bubbles of oxygen gas or ozone gas, the anaerobic state (state without oxygen) is efficiently avoided, An aerobic state (a state where oxygen is present) can be maintained, which is preferable. In a more preferred embodiment, when ozone gas micro-nano bubbles are used, not only oxygen can be dissolved efficiently in the waste water, but also sulfate-reducing bacteria can be directly killed by ozone, so a great odor suppression effect is expected. it can.

  In the present invention, a known method can be used as a method for generating micro-nano bubbles. For example, in a preferred embodiment, a liquid and a gas can be sucked with a mixing pump to generate microbubbles, and further, microbubbles can be generated by shearing the microbubbles with a high-speed swirler incorporated in the apparatus. As a device based on this method, Kyowa Kikai's BUVITAS is commercially available, and micro-nano bubbles can be manufactured with a relatively simple device. In addition, nanobubbles can be generated by crushing microbubbles in water containing electrolyte ions by the flow of water (compression, expansion, overflow). This generation method is jointly researched by the National Institute of Advanced Industrial Science and Technology and the REO Research Institute.

  The method for adding the micro / nano bubble water of the present invention to the wastewater to be treated is not particularly limited, and in one embodiment, it can be joined to a drainage line or the like using a normal pump or the like. Although there is no restriction | limiting in particular as waste water of a process target, For example, this invention can be applied suitably with respect to the waste_water | drain etc. of a food factory or a paper mill.

  The wastewater treatment facility to which the present invention is applied is not particularly limited, but when the present invention is applied to a wastewater treatment facility having a portion that is prone to anaerobic conditions such as a simple sedimentation tank or a biological stabilization pond, the odor suppression effect is particularly exerted. preferable. A sulfate-reducing bacterium is a kind of anaerobic bacterium, which converts sulfate ions and sulfite ions present in wastewater into hydrogen sulfide in an anaerobic state (in the absence of oxygen). Therefore, odors caused by sulfate-reducing bacteria often occur in places where sludge and the like of wastewater treatment facilities tend to stay, and the generated hydrogen sulfide becomes an odor problem. Therefore, when the present invention is applied to a wastewater treatment facility such as a simple sedimentation tank, the effect is sufficiently exhibited.

  Moreover, in this invention, unless the characteristic of this invention is impaired, it is possible to add an additional process. For example, you may add the foreign material removal process by screen processing etc., and the stirring process by various stirring apparatuses to the method of this invention. The wastewater treated according to the present invention may be discharged into the environment such as the ocean or river, and may be reused as factory water. Furthermore, in order to perform the method according to the present invention under optimum conditions, the present invention can include a control step of adjusting the balance with other steps.

  From another point of view, the present invention provides a micro / nano bubble generator for producing micro / nano bubble water from gas and water, an introduction device for introducing the micro / nano bubble water into a waste water treatment facility, micro / nano bubble water and waste water to be treated. Is a wastewater treatment device comprising a treatment device in contact with the waste water.

  Thus, according to the present invention, it is possible to efficiently maintain an aerobic state (a state where oxygen is present) and not to create an anaerobic state, thereby suppressing the action and proliferation of sulfate-reducing bacteria, Odor generation can be suppressed.

  In order to explain the content of the present invention in more detail, the following examples are given. However, the following examples do not limit the scope of the present invention. Unless otherwise specified, in this specification, “part” and “%” are described as indicating “part by weight” and “% by weight”, respectively.

[Example 1]
Using a micro / nano bubble generation apparatus “BUVITAS” (Bavitas, manufactured by Kyowa Kikai Co., Ltd.), micro nano bubble water was produced under the following conditions. The generation of micro-nano bubbles by the above-mentioned apparatus has been confirmed by precise particle size distribution measurement utilizing the electric resistance method, and the result of measuring the bubble particle size for micro-nano bubble water 30 hours after production is Kyowa machine. (Http://kyowakisetsu.dreamblog.jp/blog/13.html).
<Production conditions for micro / nano bubble water>
・ Uses tap water ・ Processing time: 20 minutes ・ Processing temperature: Room temperature ・ Used gas: Air ・ Gas flow rate: 0.65 L / min Sludge collected from the bottom of the sedimentation basin (including sulfate-reducing bacteria, solid) 6 mL of a partial concentration: 5% by weight), 20 mL of dilute sulfuric acid aqueous solution (concentration: 5%), and 6 mL of micro / nano bubble water were added and left at 37 ° C. for 2 weeks.

After standing, the amount of gas generated in the Einhorn tube was measured on a scale. Based on the measured gas generation, the following formula:
Gas generation rate (%) = gas generation amount (mL) / theoretical gas generation amount (mL) × 100
Thus, the gas generation rate was obtained. Here, the theoretical gas generation amount in this experiment is calculated as 0.26 mL from the sulfuric acid and sludge used.

[Example 2]
The amount of gas generated from sludge was evaluated in the same manner as in Example 1 except that micro / nano bubble water produced from wastewater (collected from a paper mill) was used.

[Example 3]
The amount of gas generated from sludge was evaluated in the same manner as in Example 1 except that oxygen gas was sucked together with water when generating micro-nano bubbles.

[Example 4]
The amount of gas generated from sludge was evaluated in the same manner as in Example 1 except that ozone gas was sucked together with water when generating micro-nano bubbles.

[Comparative Example 1]
The amount of gas generated from the sludge was evaluated in the same manner as in Example 1 except that air-containing water was used instead of micro / nano bubble water. Air-containing water was produced under the following conditions using an air inflow device (Air Pump APN, manufactured by Lacey Co., Ltd.) and an air diffuser (Airstone NB, manufactured by Lacey Co., Ltd.). The size of the air in the air-containing water is about 150 μm in diameter.
<Production conditions for air-containing water>
・ Uses tap water ・ Processing time: 20 minutes ・ Processing temperature: Room temperature ・ Gas used: Air ・ Gas flow rate: 0.65 L / min

  Table 1 shows the gas generation rates (measured values / theoretical values) in Examples 1 to 4 and Comparative Example 1. From the result of Table 1, it became clear that generation | occurrence | production of the odor from the waste_water | drain by the sulfate reducing bacteria in waste_water | drain can be suppressed by adding the water containing a micro nano bubble.

Claims (4)

  A method for controlling the odor of wastewater in a wastewater treatment facility, comprising adding water containing micro / nano bubbles to wastewater to suppress the growth of sulfate-reducing bacteria.   The odor control method according to claim 1, wherein the water containing micro-nano bubbles is produced from waste water.   The odor suppression method according to claim 1 or 2, wherein the micro / nano bubbles are micro / nano bubbles of oxygen gas or ozone gas.   The odor suppression method according to any one of claims 1 to 3, wherein the wastewater treatment facility is a simple sedimentation tank.