JP3636670B2 - Method and apparatus for solubilizing organic solids - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is an organic waste liquid containing organic solids, for example, raw sludge and biological sludge discharged from a sewage treatment process such as a sewage treatment plant and a manure treatment plant, a food factory, a chemical factory, etc. The present invention relates to a method for aerobically solubilizing an organic solid contained in an organic waste liquid.
[0002]
[Prior art]
Conventionally, as a general treatment method of the above organic waste liquid, first, organic components of organic sludge are biologically digested by microbial decomposition using aerobic digestion method, anaerobic methane fermentation method, etc. Decomposition into gas components such as carbon dioxide and methane gas, and then treat sewage sludge containing surplus sludge consisting of microbial biomass (mainly microbial cells) and untreated residual sludge generated by such biological digestion, etc. The treated water obtained as a supernatant after solid-liquid separation is appropriately discharged, while surplus sludge is usually widely treated by ocean dumping or land reclamation. However, dumping such surplus sludge into the ocean leads to environmental destruction, and in recent years when protection of the global environment is screamed, it is almost prohibited. In land reclamation, it is becoming more difficult to secure landfill sites each year.
[0003]
The present applicant has reported an activated sludge treatment method and an apparatus therefor as an invention capable of reducing the amount of excess sludge generated by such a method for treating organic waste liquid (Japanese Patent Laid-Open No. 9-10791). According to this method, the organic wastewater is subjected to treatment in the aeration tank, and then separated into treated water and sludge in the settling tank, and a part of the separated sludge is attached to the aeration tank via the circulation path. The surplus sludge that is the remainder of the sludge is solubilized by thermophilic bacteria in the solubilization treatment tank, and the solubilization treatment liquid is returned to the aeration treatment tank via the return path. Thus, excess sludge is volume-reduced by passing through a solubilization process.
[0004]
[Problems to be solved by the invention]
According to the treatment method disclosed in the above publication, the solubilization treatment of excess sludge is usually carried out by heating aerobically or slightly aerobically while aeration is intended to solubilize by aerobic thermophilic bacteria. Is done. However, when aeration is continued, in order to exhaust the gas, the amount of heat released outside the system due to the exhaust must be very large. Therefore, the amount of heat required for the solubilization treatment is increased, which leads to an increase in the treatment cost, which is an unavoidable factor in terms of energy saving in consideration of environmental aspects.
[0005]
For this reason, a method has been proposed in which the dissolved oxygen (DO) concentration of the solubilized treatment liquid is monitored for the purpose of appropriately controlling the amount of aeration, and the flow rate is adjusted based on this value (Japanese Patent Laid-Open No. 10-277580). Issue gazette). However, with this method, it is impossible to control the amount of aeration when DO is 0 or less. Even if DO is 0 or less, it is not preferable to perform aeration more than necessary to release a large amount of heat.
[0006]
The present invention has been made in view of the above-described problems of the prior art, and its purpose is to appropriately control the amount of aeration during the solubilization treatment to prevent energy loss, and to achieve aerobic goodness. An object of the present invention is to provide a method capable of efficiently achieving sufficient solubilization while maintaining the activity of thermophiles.
[0007]
[Means for Solving the Problems]
The present invention for achieving the above object is a method for solubilizing an organic solid ,
The sludge concentration of the solubilization reaction liquid in the solubilization tank is set to 5000 mg / L or more,
Organic solids characterized by solubilization using an aerobic thermophilic bacterium Bacillus stearothermophilus and adjusting the redox potential of the solubilized reaction solution to a range of -200 mV to 100 mV This is a solubilization method. The oxidation-reduction potential substantially reflects the oxidative degradation ability latent in the solubilized reaction solution and is considered to affect the activity of the microorganism. By maintaining the oxidation-reduction potential within a specific range where the activity of Bacillus stearothermophilus can be maintained, solubilization of sludge can be achieved without accompanying more heat loss than necessary. The ability to maintain the activity of Bacillus stearothermophilus here means that the cells grow so that they can survive normal biological activity and are capable of secreting an enzyme that can solubilize sludge. Say.
[0008]
In the present invention, the solubilizing reaction redox potential 100mV below the range of -200mV of organic solids, adjusting more preferably less than 50mV the range of -100mV Then, efficiently variable while suppressing the more heat loss Solubilization can be performed.
[0009]
The most preferred method for maintaining the oxidation-reduction potential is to control the amount of aeration to the solubilization reaction solution, and also by changing the amount of organic solids charged into the solubilization tank, It is also possible to adjust appropriately.
[0010]
Furthermore the present invention, solubilization tank for storing the solubilized reaction, oxidation-reduction potential measuring device for measuring the redox potential of the solubilization reaction, blowing means to the solubilization tank, and from said blowing means A sludge solubilization device having an air flow rate adjusting means for adjusting the air flow rate of
The solubilized reaction solution contains an organic solid having a sludge concentration of 5000 mg / L or more and an aerobic thermophilic bacterium, Bacillus stearothermophilus,
The oxidation-reduction potential is in the range of −200 mV to 100 mV, and the aeration amount adjusting means adjusts the aeration amount according to the fluctuation of the oxidation-reduction potential in the solubilization tank measured by the measuring device. An apparatus for solubilizing sludge is provided.
The present invention additionally provides solubilization tank for storing the solubilized reaction, oxidation-reduction potential measuring device for measuring the redox potential of the solubilization reaction, blowing means to the solubilization tank, to the solubilization tank A sludge solubilization device having organic solids charging means, and organic solids charging amount adjusting means,
The solubilized reaction solution contains an organic solid having a sludge concentration of 5000 mg / L or more and an aerobic thermophilic bacterium, Bacillus stearothermophilus,
The oxidation-reduction potential is in the range of −200 mV to 100 mV, and the organic solids charging means measures the organic solids according to fluctuations in the oxidation-reduction potential in the solubilization tank measured by the measuring device. Provided is a sludge solubilization device characterized by adjusting the amount of charge. The above-described solubilization method can be suitably carried out with these apparatuses.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0012]
FIG. 1 shows a solubilizer representing a preferred embodiment of the present invention. This solubilization apparatus includes a solubilization tank 1, an oxidation-reduction potential measuring device 2, an aeration amount adjusting means 3 and an air supply means 4. In the solubilization tank 1, the sludge is, for example, 50 to 80 ° C., preferably 60 to 70 ° C., and the sludge concentration is preferably 1000 mg / L or more, more preferably 5000 mg / L or more, preferably pH = 7 to 9 More preferably 7.5-8.5, operated under aerobic or microaerobic conditions. Heating may be performed by a heater, steam introduction, or the like. At this time, air or oxygen is ventilated from the air supply means 4 to the solubilization tank 1 in order to appropriately advance solubilization of the organic solid matter while maintaining the activity of the aerobic thermophile. It is controlled by the ventilation amount adjusting means 3. The aeration amount adjusting means 3 is controlled by the redox potential measuring device 2 that detects the redox potential of the solubilized reaction solution in the solubilization tank 1. That is, the amount of aeration from the air supply means 4 is adjusted according to the fluctuation of the oxidation-reduction potential in the solubilization tank 1, and the oxidation-reduction potential of the solubilization reaction solution is -200 mV to 100 mV, preferably -100 mV to 50 mV. Maintained within the range. As described above, the oxidation-reduction potential substantially reflects the potential oxidative degradation ability of the solubilized reaction solution. Therefore, in this embodiment, the oxidation-reduction potential is maintained within the above range by controlling the aeration amount. This makes it possible to achieve solubilization of sludge without causing the disadvantage of loss of heat by aeration more than necessary. If the oxidation-reduction potential exceeds the predetermined range, the loss of heat taken out by the exhaust gas due to excessive ventilation increases, resulting in an increase in cost. On the other hand, if the oxidation-reduction potential is smaller than the predetermined range, the solubilization rate decreases. End up. For solubilization, Bacillus stearothermophilus which is an aerobic thermophilic bacterium and other aerobic thermophilic cells are used, and enzymes such as protease, lipase and glycosidase are used to promote solubilization. May be blended alone or in combination.
[0013]
Examples of the redox potential measuring device 2 include a redox potential measuring device ODIC-3 manufactured by Toa Denpa Kogyo Co., Ltd., equipped with a PS-8405 redox potential sensor manufactured by Toa Denpa Kogyo. Control of the flow rate adjusting means 3 based on the measurement result is performed by a known signal transmission system. As the flow rate adjusting means 3, a flow rate adjusting valve can be most preferably used. However, a plurality of other air supply means 4 are prepared, and an appropriate on / off signal is sent to each to adjust the number of operations of the air supply means. It is also possible to adopt a means, a means for providing a plurality of ventilation paths from one air supply means 4 and sending an appropriate on / off signal to adjust the number of ventilation paths. As the air supply means 4, those conventionally used such as an air pump, a blower, a fan, a compressor, a mechanical aeration machine, an oxygen generator and an oxygen cylinder may be used.
[0014]
In order to maintain the redox potential of the solubilized reaction solution within the above range, in addition to controlling the amount of ventilation to the solubilized reaction solution, for example, it is possible to change the input amount of organic solids, or It is also possible to change the solution treatment time (residence time).
[0015]
The organic solid solubilization treatment method of the present invention using the above-described solubilization apparatus can be employed in various conventional methods for organic waste liquid treatment, including anaerobic microbial fermentation, aerobic microbial digestion and Both purification of treated water and volume reduction of sludge can be achieved by appropriately combining with each process such as solid-liquid separation.
[0016]
【Example】
Examples of the present invention will be described below, but the scope of the present invention is not limited by these examples.
Example 1
2L surplus sludge derived from a sewage treatment plant (2% by weight sludge concentration) is introduced into a 5L jar fermenter with an effective volume of 2L, and the aerobic thermophilic bacterium Bacillus stearothermophilus SPT2-1 [FERM P-15395] and using the solubilizer outlined in FIG. 1 at 65 ° C. under conditions of pH = 7.5-8.5 at various redox potentials ranging from −200 to 200 mV. Each solubilization rate when the treatment time was 24 hours was determined, and each dissolved oxygen amount (DO, mg / L) and aeration amount (vvm: aeration amount / effective volume / min) were recorded.
[0017]
The solubilization rate (%) was calculated based on the organic solids (vss) content before and after the solubilization treatment. The measurement of vss was performed according to JISK0102.
[0018]
DO was measured with a dissolved oxygen measuring device DDIC-7 manufactured by Toa Denpa Kogyo Co., Ltd. equipped with a dissolved oxygen sensor for fermentation of OE-8PT2 manufactured by Toa Denpa Kogyo.
[0019]
The results thus obtained are shown in FIG. FIG. 2 shows that the sludge can be well solubilized by maintaining the oxidation-reduction potential in the range of −200 mV to 100 mV. When the oxidation-reduction potential exceeds 100 mV, the solubilization rate is maintained in an almost equilibrium state, and it can be seen that even if the aeration rate is further increased to increase the oxidation-reduction potential, only the energy loss increases.
[0020]
It was shown that a solubilization rate of about 35 to 40% can be achieved when the oxidation-reduction potential is set to -100 mV or more, but the aeration amount for maintaining the oxidation-reduction potential at -100 mV is 0.08 vvm. Yes, DO was 0 at this time. When the air flow rate was controlled based on DO by the conventional method, the air flow rate was 0.2 vvm. Therefore, by setting the oxidation-reduction potential to -100 mV, the air flow rate can be reduced to less than half, and thus energy loss. It was thought that can be suppressed to less than half. Since DO was 0 until the oxidation-reduction potential was about 50 mV, by setting the oxidation-reduction potential in the range of −100 mV to 50 mV, particularly energy loss can be sufficiently suppressed and the solubilization rate is good. Became clear.
[0021]
【The invention's effect】
According to the present invention, in the aerobic or microaerobic solubilization treatment method of sludge used for the treatment of organic waste liquid, a method of achieving good solubilization and low energy loss is provided. This method is based on an oxidation-reduction potential that can be measured relatively easily. For example, the amount of aeration is controlled so as to maintain it within a predetermined range, so that the activity of aerobic bacteria can be easily and efficiently solubilized. However, the amount of heat required for heating can be saved.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing the configuration of a solubilizing apparatus of the present invention.
FIG. 2 is a graph showing the correlation between the solubilization rate, dissolved oxygen, and aeration rate when sludge is solubilized at various oxidation-reduction potentials.
DESCRIPTION OF SYMBOLS 1 ... Solubilization tank 2 ... Redox potential measuring device 3 ... Aeration amount adjustment means 4 ... Air supply means

Claims (7)

An organic solid solubilization method comprising :
The sludge concentration of the solubilization reaction liquid in the solubilization tank is set to 5000 mg / L or more,
Organic solids characterized by solubilization using an aerobic thermophilic bacterium Bacillus stearothermophilus and adjusting the redox potential of the solubilized reaction solution to a range of -200 mV to 100 mV Solubilization method. The method according to claim 1, wherein the organic solid is excess sludge. The redox potential The method according to claim 1 or 2 which is less than 50mV the range of -100 mV. The redox potential, the method according to any one of claims 1 to 3 is adjusted by controlling the airflow rate to the solubilizer tank. The redox potential, the method according to any one of claims 1 to 3 is adjusted by the control of the organic solid dosages into the solubilizer tank. Solubilization tank for storing the solubilization reaction, oxidation-reduction potential measuring device for measuring the redox potential of the solubilization reaction, blowing means to the solubilization tank, and air feed amount from the air supply means A sludge solubilization device having an air flow rate adjusting means for adjusting
The solubilized reaction solution contains an organic solid having a sludge concentration of 5000 mg / L or more and an aerobic thermophilic bacterium, Bacillus stearothermophilus,
The oxidation-reduction potential is in the range of −200 mV to 100 mV, and the aeration amount adjusting means adjusts the aeration amount according to the fluctuation of the oxidation-reduction potential in the solubilization tank measured by the measuring device. A sludge solubilizer characterized by Solubilization tank for storing the solubilization reaction, oxidation-reduction potential measuring device for measuring the redox potential of the solubilization reaction, blowing means to the solubilization tank, organic solids introduced into the solubilizing tank And a sludge solubilization device having an organic solid matter input amount adjustment means,
The solubilized reaction solution contains an organic solid having a sludge concentration of 5000 mg / L or more and an aerobic thermophilic bacterium, Bacillus stearothermophilus,
The oxidation-reduction potential is in the range of −200 mV to 100 mV, and the organic solid substance charging means is an organic solid substance according to the fluctuation of the oxidation-reduction potential in the solubilization tank measured by the measuring instrument. A sludge solubilizer characterized by adjusting the input amount.

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