JPS60222196A - Treatment of organic waste water - Google Patents

Abstract

PURPOSE:To treat efficiently waste water contg. org. material by fermenting the waste water contg. org. material by microorganisms in an anaerobic atmosphere, separating and thickening the lower org. material formed by such fermentation by means of a hydrophobic porous membrane under high-frequency oscillation and removing the same to the outside of the system. CONSTITUTION:The waste water contg. org. material is acid-fermented by the microorganisms in the anaerobic atmosphere having about 0.1-0.0001mg/l concn. of dissolved oxygen to form the lower org. material such as volatile fatty acid. The lower org. material is separated and thickened by the hydrophobic porous membrane under high-frequency oscillation and is removed to the outside of the system. The hydrophobic porous membrane is formed by cladding, for example, polyvinylidene fluoride films 3, 3 having a ferrodielectric property and distributed adequately with double bonds according to need to a polytetrafluoroethylene film 1, etc. via films 2, 2 formed by a radical treatment of a polytetrafluoroethylene film, etc. to form the hydrophobic porous membrane X. Higher microwaves are generated in the surface of the film 3 by impressing the high-frequency drive to the film 2 of the membrane X.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for treating organic wastewater that decomposes and separates and removes organic substances contained in organic wastewater.

In general, as a method for treating domestic wastewater such as sewage, barbershops, sewage, etc. or their decomposed products, and wastewater containing organic substances such as agricultural, livestock, and fishery waste such as orange peel, It is known that organic substances are separated from wastewater using separation membranes such as filtration membranes and reverse osmosis membranes, but this treatment method has a slow separation speed and concentration polarization occurs during treatment. This method has disadvantages such as a decrease in the permeability of the separation membrane and an increase in energy consumption to prevent the decrease.

Also known is an anaerobic digestion method that uses anaerobic microorganisms to decompose and remove M-organic components in wastewater. This anaerobic digestion method ferments wastewater containing, for example, fats, proteins, polysaccharides, or their decomposition products, converting them into lower organic substances such as volatile fatty acids, and then fermenting them to produce methane gas, carbon dioxide, etc. This process consists of two steps: a reaction in which acid is mainly produced by obligately anaerobic microorganisms (acid fermentation), and a reaction in which methane is produced by obligately anaerobic microorganisms (methane gasification fermentation). This method does not require any particular external energy except when it is necessary to maintain the digestion temperature, and the amount of sludge produced is small, so it is excellent from an energy-saving perspective, but the reaction rate is low. It is slow and the biochemical process is long, so the processing time is long and the processing equipment is large.In addition, it is sensitive to large changes in external environmental conditions such as organic load, and there are inconveniences such as the reaction stopping. there were.

Therefore, the present inventor discovered that the rate of acid fermentation is about 10 times faster than the rate of subsequent methane gasification and fermentation, and that the organic substances in wastewater are complex, such as fats, proteins, polysaccharides, and other decomposed products of these. Even if it is a mixture, it can be converted into a small number of low-molecular organic substances that are liquid or gaseous at room temperature through acid fermentation, such as volatile fatty acids such as acetic acid, alcohols, aldehydes, ketones, ammonia, carbon dioxide, hydrogen, and water. Focusing on the fact that it is capable of intensively decomposing and also removing surface-active substances such as alkyl sulfuric acid, we are conducting research to develop a separation membrane that can separate lower organic substances produced by this acid fermentation from the treated liquid. As a result, we found that by using a hydrophobic porous membrane that vibrates at high frequencies, it is possible to efficiently separate and concentrate the low-molecular organic substances mentioned above, without relying on the slow methane gasification fermentation mentioned above. It was discovered that organic wastewater can be treated extremely efficiently, and the present invention was constructed based on this finding.

Furthermore, normally, in anaerobic digestion, when the pH of the reaction solution is around 6.8, or when the co-oil inside the system of proliferating bacteria becomes long and its concentration becomes high, methane gasification fermentation occurs, and acid fermentation occurs. We learned that the concentration of lower organic substances, that is, low-molecular-weight organic substances produced by organic waste water, becomes diluted and the separation efficiency by hydrophobic porous membranes decreases.As a result of our study, we found that the concentration of dissolved oxygen in organic wastewater was reduced to 0. 1~0.000
It was found that if anaerobic fermentation is performed with the 1 m971 position, only acid fermentation is performed and methane gasification and fermentation can be suppressed.

Then, the dissolved oxygen concentration in this organic wastewater was set to 0.1 to 0.
As a means for adjusting oooimp/l, when methane gasification and fermentation occurs, oxygen is supplied to adjust the dissolved oxygen concentration in the organic wastewater.

That is, in the method for treating organic wastewater according to the present invention, lower organic substances are produced by fermenting wastewater containing organic substances with microorganisms in an anaerobic atmosphere.
The organic material is stably separated, concentrated, and removed from the system using a hydrophobic porous membrane vibrated at high frequency. Facultative anaerobes such as denitrifying bacteria,
There are thermophilic anaerobic bacteria that ferment alcohol, acetic acid, and cellulose. .

In addition, as a hydrophobic porous membrane, for example, as shown in the schematic diagram shown in Fig. 3, a polytetrafluoroethylene membrane 1 or the like has ferroelectricity, and double bonds can be appropriately distributed as necessary. The polyvinylidene fluoride films 3 and 3 are made of a polytetrafluoroethylene film or the like which is subjected to radical treatment.
2 to form a hydrophobic porous membrane X, a conductor such as carbon fiber was used as an electrode material on this porous membrane X, and this electrode 5 was connected to a high frequency power source to undergo the radicalization treatment. A device is used in which harmonic microwaves are generated on the surface of the membrane 3.3 by applying a high frequency drive to the membrane 2.2. These detailed configurations can be found in the patent application filed earlier by the applicant of this patent in 1982-221.
This is similar to the "flat plate membrane separation device" disclosed in No. 443.

Here, the electromagnetic field characteristics of the surface of the hydrophobic porous membrane Depending on the characteristics, it can be adjusted by changing the radicalization conditions of the polytetrafluoroethylene membrane, ie, the thickness and combination of the radicalized membranes 2, 2. Note that the radicalization treatment of the polytetrafluoroethylene membrane can be carried out by performing forced electrolytic treatment in a vapor phase active oxygen or M solution.

Generally, a flowing potential is generated when a liquid moves with respect to the surface of a solid, but in the present invention, the polytetrafluoroethylene membrane 1 and the like are appropriately combined with the membranes 2 and 2 which have been subjected to radicalization treatment, etc. Well, by adjusting the electromagnetic field characteristics and reversing the flowing potential, the lower organic substances and water separated by the above-mentioned high-frequency vibration can be separated by combining the potential change during movement within the hydrophobic porous membrane X. It can also be promoted. For this purpose, electrodes 6.6 may be provided to sandwich the porous membrane X in FIG. 3 and provide a potential difference on both sides.

Fermentation by microorganisms in an anaerobic atmosphere is
As shown in Figures 1 and 2, the anaerobic fermenter A1
．． Organic wastewater was introduced into A2, and the aforementioned facultative anaerobic microorganisms were inoculated in the form of digested sludge.
Acid fermentation is carried out in the presence of a small amount of dissolved oxygen of 1/1.

In this state, lower organic substances such as acetic acid, alcohol, and ketone in the acid fermentation solution are in a state of hydrogen bonding with water polymers in the solution.

Therefore, when this treated liquid is supplied to the membrane separation/concentration tank sections B, , and B2 equipped with a hydrophobic porous membrane The substances are then separated and adenized and passed through the porous membrane X1 to be removed from the waste water.

Anaerobic fermenter A1 at this time. As shown in FIG. 1, the connection relationship between A2 and the membrane separation concentration tank section Bt, B2 is configured such that after completion of fermentation, the fermented product is supplied to the membrane separation concentration tank section B1. Also, as shown in the second factor, during the fermentation, it is supplied to the membrane separation concentration tank part B2, and only the lower organic substances are separated in the membrane separation concentration tank part B2, and the rest are sent to the fermentation tank A2 again. You may also adopt a circulation method that returns the water to . In either type, lower organic substances are separated and concentrated in membrane separation/concentration tank sections B, , and B2, and the separated and concentrated lower organic substances are removed from the system to process organic wastewater. be exposed.

As mentioned above, the present invention skillfully combines and combines the anaerobic fermentation method and the membrane separation method to convert wastewater containing organic substances into wastewater containing lower organic substances, and to convert this into wastewater containing lower organic substances with high efficiency and speed. As a result, the biochemical process can be shortened, and as a result, the processing equipment can also be made smaller. When separating and concentrating lower organic substances from acid fermentation liquid, the energy consumption is approximately 1/600th compared to distillation, which contributes to so-called energy saving, and it also exceeds the normal limit. Unlike separation using external filtration or reverse permeation membranes, the concentration of separated substances is extremely high, it is compact and easy to store and handle, and it also removes propionic acid, ethanol, etc. that cannot normally be removed by methane gasification and fermentation. , which is far superior to methane gasification and fermentation.

Next, an actual example of the present invention will be explained.〇Example 1 A wastewater treatment device is configured as shown in Fig. 1, and excess sludge is removed using a centrifuge at a sewage treatment plant to remove solids. Organic wastewater concentrated to a concentration of 5% was collected and analyzed, and the acetic acid concentration was found to be 300 μ/l. This organic wastewater 1
1. Digested sludge containing Pseudomonas bacteria collected as microorganisms from the digestion tank of a sewage treatment plant is inoculated as a seed, kept at 38℃, and anaerobically grown while stirring by blowing air diluted 2000 times with nitrogen gas. By fermenting for 2 days in a neutral atmosphere, an acid fermentation solution containing 3000 Tn9/l of acetic acid was obtained. During this time, no generation of methane gas was observed. This acid fermentation treated liquid is introduced into the membrane separation concentration tank sections B, , B2, and the membrane separation concentration tank sections B+, B
The hydrophobic porous membrane X (
45 to this porous membrane
Apply a high frequency drive of about 5KHz, 250V,
Low-molecular organic substances were separated by generating harmonic microwaves of around GHz on the membrane surface.

As a result, it was possible to separate low-molecular organic substances containing about 10% water and mainly consisting of acetic acid at a speed of 12 to 13 ml/min with a small energy consumption of about 1.2 W/min.

Example 2 The treatment equipment was connected to form a circulating flow between the anaerobic fermentation tank A2 and the membrane separation concentration tank section B2 as shown in FIG. The collected wastewater is filled into fermentation tank A2, and immediately after seeding, it is transferred to membrane separation concentration tank section B.
2 and started membrane separation, and after half a day it was possible to separate low-molecular organic substances at an average rate of about 0.1 ml at 7:00. During this period, no methane gas was observed. When fermentation and membrane separation were completed in 10 days and the concentration of organic substances in the treated liquid was examined, it was found that about 50% of the organic substances initially present had been digested and removed.

The conventional method of methanation, in which acid fermentation and methanogenic bacteria coexist and ferment in one phase, requires 20 days to perform the same amount of treatment, but the time is significantly reduced. Obtained.

Here, if the treatment liquid is configured to form a circulation flow between the fermentation tank A2 and the membrane separation concentration tank part B2 as in this embodiment, fermentation by lower organic substances as fermentation products during the fermentation process is possible. Inhibition and methane fermentation are prevented, and the ability to accelerate the reaction and shorten the reaction time is obtained.

[Brief explanation of drawings]

1 and 2 of the drawings are flow sheets of different embodiments for carrying out the method for treating organic wastewater according to the present invention,
FIG. 3 is a schematic diagram for explaining the internal configuration of the membrane separation concentration tank section. A+, A2; Anaerobic fermentation tank B+, B2 two-membrane separation/condensation tank part Membrane 5.6; Electrode patent applicant Sanki Kogyo Co., Ltd. Figure 1 ΔSong No. 3B

Claims (1)

[Claims] (11) Lower organic substances are produced by fermenting wastewater containing organic substances with microorganisms in an anaerobic atmosphere, and these lower organic substances are separated and separated by a hydrophobic porous membrane subjected to high frequency vibration. A method for treating organic wastewater characterized by concentrating it and removing it from the system. (2) Fermentation of wastewater containing the above organic substances by microorganisms:
2. The method for treating organic wastewater according to claim 1, wherein the treatment is carried out in an anaerobic atmosphere with a dissolved oxygen concentration of 0.1 to 0.0001 cm/1. (3) The method for treating organic wastewater according to claim 1, wherein the fermentation is acid fermentation.