JPS621498A - Utilization of anaerobic bacteria - Google Patents

Abstract

PURPOSE:To stably hold bacterial cells in a column, by mixing an anaerobic bacterial cell slurry and effective polymer resins having gel forming capacity in the presence of air bubbles before gelling said resins. CONSTITUTION:An urethane polymer is added to digested sludge and both of them are mixed under stirring in the presence of CO2 gas bubbles generated by the reaction of the polymer with water to obtain a gel wherein CO2 gas bubbles and anaerobic digestion bacteria were included and immobilized. This gel is granulated into a pellet form and a column is packed with pellets to form a float packed bed. Excretion from which a residue was removed is introduced into an anaerobic digestion column 3 from an introducing pipe 1 through an upper raw water distributor 2 to be passed therethrough in a downward stream. Whereupon, raw water receives methane fermentation by high concn. anaerobic digestion bacteria in gel particles to generate CH4-gas and CO2. The gas is guided to a digestion gas storage tank from a gas vent pipe 5.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to anaerobic digestion of organic waste liquid, nitrate nitrogen (NO
The main application field is anaerobic microbial treatment in the wastewater treatment field, such as biological denitrification of water containing x-N) and generation of 4S by sulfate-reducing bacteria in water containing 5o42- ions. This invention relates to a method of using immobilized anaerobic microorganisms in the field of using anaerobic microorganisms in the fermentation industry for the purpose of producing valuable products such as fermentation.

[Conventional technology and its problems]

Anaerobic reaction devices having means for retaining anaerobic bacteria have recently attracted much attention, and the following systems have been actively studied, and some have even been put into practical use.

■ Anaerobic Ifilte
r)■ Anaerobic Upflow Planchella) (UASB)■
The anaerobic granular media upflow fluidized bed anaerobic housing floor method uses stone, glass (polyester,
Fill the column with granular solids such as vinyl chloride, etc.
A biofilm of anaerobic bacteria such as 1methane bacteria is grown on the surface of the granular solid, and the water to be treated is passed over the biofilm, but when water containing a large amount of 8B is treated, the hearth becomes clogged. The disadvantage is that it is easy to Furthermore, if the particle size of the granular solid is increased in order to prevent clogging of the hearth, the surface area of the door material will be reduced and the amount of anaerobic bacteria will be reduced, resulting in a contradiction in that the reaction rate will be reduced.

Next, the 1-air upflow blanket method was developed in 1979 by Mr. Lettinga of the Netherlands, in which the light part of anaerobic bacteria (70 kg) is drained out to form agglomerated bacteria with a heavy ratio. The raw water is circulated in an upward flow using only the body as a fluidized bed.

To briefly explain this method based on FIG. 2, the water to be treated is distributed from the water introduction pipe 12 into the agglomerated sludge bed 14 at the bottom of the treatment tank 11 by the inflow water distribution plate 13,
The liquid to be treated is transferred from the agglomerated sludge bed 14 to the sludge blanket 1.
5 is too small, the water is introduced into the settling tank 17 through the gap between the baffle 16 and the settling tank 17 through the bottom opening of the settling tank 17, the accompanying sludge is separated in the settling tank, and the treated water is discharged into the treated water discharge pipe 1.
8, and the separated sludge is returned to the sludge blanket section from the lower opening of the settling tank 17, passing between the baffles 16 and 16'. Further, the gas generated in the processing tank 11 is collected in the upper part of the processing tank and is discharged from the tank through the gas discharge pipe 19. This method is also called a self-carrier solidification method because it does not use a granular medium such as sand for adhesion of bacterial cells. Although this TTASB method is an extremely interesting method, the following problems have been found according to the inventor's additional tests.

■ It takes a long time to form heavy aggregated bacteria at the start of operation, and in some cases, the process ends without any aggregated bacteria being formed.

@ It is difficult to introduce and distribute raw water evenly from the bottom of the tank, which tends to cause uneven upward flow. Especially when the tank diameter is large, it is extremely difficult to distribute the raw water evenly.

Next, in the granular media upflow fluidized bed method, a biofilm of anaerobic bacteria is formed on the surface of small-sized granular solids such as sand grains and granular activated carbon in a column, and raw water is introduced from the bottom of the column as an upward flow. This method treats raw water while forming a fluidized bed of granular solids.

Although this method has the advantage of eliminating the possibility of clogging because the entire particle is in a fluid state, it does have the following drawbacks. In other words, it is necessary to provide a separate sedimentation tank for raw water with a high SEI content, and because the flow velocity around the particles is set to be close to the floating velocity of the particles, there is a possibility of particle carryover. There will be more. Furthermore, it is necessary to increase the upward flow velocity to fluidize one medium, so if the amount of raw water to be treated is small, a circulation pump is required to circulate the treated water, and the power cost of this pump is a cost that cannot be ignored. It may become.

[Problem that the invention seeks to solve]

The present invention solves all of the problems of the prior art described above by a method not seen in the prior art.

[Means to solve the problem]

The present invention uses an anaerobic digestion tank, a slurry of anaerobic microorganisms such as denitrifying bacteria, and organic polymer resins having gel-forming ability, or monomers or prepolymers thereof, which are mixed in the presence of air bubbles and then gelled. By this, the anaerobic microorganism cells and air bubbles are immobilized, the granular material of the gel is filled into an anaerobic biological treatment tank to form a floating layer, and the liquid to be treated is directed downward to the floating layer. This is a method of utilizing anaerobic microorganisms characterized by distributing them in a stream.

Highly concentrated oxygen gas is contained in the gel as air bubbles.
This is not preferable because it deactivates anaerobic bacteria, and 0Otsk gas, which does not deactivate anaerobic bacteria, is suitable.

[Embodiments of the invention]

One embodiment of the present invention will be explained using anaerobic digestion of human waste as an example.

Digested sludge (solids concentration 3) from the existing human waste anaerobic digestion tank
%) is collected, 10% by volume of urethane prepolymer is added thereto, and the CO generated by the reaction of the polymer with water is collected.
When mixed and stirred in the presence of gas bubbles, a gel in which O pseudobubbles and anaerobic digesters were entrapping and immobilized was obtained. This gel had a specific gravity of cL95 to α98 and floated on water.

The above gel was extruded using a screw extrusion granulator to a diameter of 5vm and a length of 5mm.
- After granulation into cylindrical pellets, they were put into the experimental apparatus shown in Fig. 1 (packed column diameter: 200-φ) and the layer thickness was 5.
A floating filling layer of 00- was formed. The liquid to be treated (removed human waste) was introduced into the anaerobic digestion column 3 from the introduction pipe 1 through the upper raw water distributor 2 (inverted umbrella shape) and allowed to flow downward. The column 3 is filled with floating gel particles 4 in which the aforementioned anaerobic digester is encased and immobilized, and as the raw water (removed human waste) flows through the layer, the particles in the gel particles are CH4 is subjected to methane fermentation by high-concentration anaerobic digestion teeth.
,C generates false gas. The generated digestion gas bubbles containing 〇H, as a main component float up through the gaps in the layer and are led to the digestion gas storage tank (not shown) from the gas vent v5 at the top of the tank. In addition, if the generated digestion gas bubbles are stuck to the surface of the gel particles and do not rise toward the gas accumulation part 5' at the top of the tank, a part of the gas is branched off from the generated gas vent pipe 5. When air is diffused from the bottom of the buoyant gel particle layer, a shock is given to the inside of the buoyant layer, which is effective because the air bubbles trapped on the surface of the gel particles separate and rise. Another effective method is to mechanically stir the inside of the floating layer using stirring blades.

In the present invention, since the anaerobic digestion teeth form the floating layer, there is no need for a special gas separation mechanism that is indispensable in the conventional anaerobic upflow blanket method KTh. , there is no risk of anaerobic bacteria leaking out of the system; rather, the gel particles tend to float due to the rising action of the generated gas, which is an important feature in that the bacterial cells are more stably retained within the column. .

Then, aS (suspended particles) in the liquid flowing out from the floating layer 4 after undergoing sufficient anaerobic digestion - non-biodegradable BE-1 in the raw water? and the newly generated microbial cells 88 settle in the sedimentation section 6, and the treated water is discharged from the system from the treated water outflow pipe 8 via the treated water upflow and outflow section 7.

Incidentally, during the course of the treated water passing through the rising and outflowing section 7, the treated water is also subject to sedimentation.

In this way, in the present invention, since it is possible to provide the SS sedimentation separation section at the bottom of the methane fermentation tank, there is an important practical effect that there is no need to provide the 88 sedimentation separation tank separately from the methane fermentation tank. be.

In addition to the above-mentioned urethane, microorganism immobilization resins such as polyacrylamide, calcium alginate, and photocrosslinkable resin can be used as the gel material for entrapping and immobilizing air bubbles and anaerobic microbial cells. However, when urethane is used, the bubbles generated when the prepolymer reacts with the molecule can be used to impart floating properties to the gel, so it is most suitable for the present invention.

It goes without saying that as the anaerobic bacteria, denitrifying bacteria, sulfate reducing bacteria, and alcohol fermenting bacteria can be selected depending on the purpose of treatment.

Example 1 Anaerobic Digestion of Human Human Waste The granular gel of an anaerobic digester encased in polyurethane gel prepared by the method described in the embodiment section of the invention was heated in a sufficiently warmed experimental apparatus (floating bed column) shown in FIG. Diameter 200-
φ, column height 10100 (1 gel floating layer thickness 500 points), the removed human waste was heated to a temperature of 35° C., and fed under the conditions that the floating layer residence time was 5 days. The water quality of the filtered human urine is EOD 817 o ry)/1 ss aloo my/1 00Dcr 12000q/r T-N3200# pH 7.8.

Seven days after the start of water flow, methane fermentation started to progress smoothly, and a good result of 80% removal rate of 0ODar was obtained.

Example 2 Biological denitrification treatment Hog-N (nitrate nitrogen) 100-150m9/
This paper describes the results of applying the method of the present invention to biological denitrification treatment of factory wastewater containing 1.

Acrylamide monomer 25002 and methylenebisacrylamide 120? After adding and dissolving 5% β-dimethylaminoprobionitrile solution 1500-
When the microbubbles on the island were aerated, it polymerized in about 20 minutes.
A polyacrylamide gel was obtained in which denitrification images and island bubbles were immobilized. This gel was formed into cylindrical pellets with a diameter of 2 m and a length of 4 mm using a screw extrusion granulator, and then packed into a column with a diameter of 100 mm to form a floating layer with a layer thickness of 400 mm. The aforementioned N0I-N-containing wastewater (pa
ts.

After adding 300 to 500 da/l of CH, OH to the water temperature (25℃), the column was fed in a downward flow, and the operation was continued with the liquid residence time in the floating layer being 1.5 hours (empty column standard). As a result, from the second day after the start of water flow, N and gas due to the reduction of Hog-N began to be generated rapidly. On the 3rd day of water flow, the N0 of the water flowing out from the floating gel layer continued for 1 month.
Analysis of x-N showed an extremely good removal rate of 2 to arn9/z.

〔Effect of the invention〕

■ CH4, N, which are metabolic products of anaerobic bacteria! There is no fear that the anaerobic bacterial biomass will flow out of the system due to disturbances caused by the upward force of bubbles such as , C, etc.

■ Unlike the anaerobic upflow blanket method, there is no need to expect the methane bacteria to form aggregates themselves, so startup is very easy.

Furthermore, since there is no need to provide a gas separator in this method, the device is easy to manufacture.

■ Since the raw water falls from the top through the gas phase and is supplied to the floating layer of anaerobic bacteria, the pressure loss due to the water head is large, making it easy to distribute the raw water evenly.Problems with the tJAsB method One of the problems can be solved and scaling up is easy.

(2) The upper part of the same tank can be used as the anaerobic biological treatment part and the lower part can be used as the BB sedimentation division, so there is no need to provide a separate settling tank as in the conventional method.

■ In the tJAsB method and the granular media upflow fluidized bed method, when raw water containing a large amount of 88 is treated, a scum layer is formed at the top of the tank, which impedes the treatment function, but in the present invention, the raw water is Since the water flows through the water, no scum floats up, and the scum is destroyed by the water flow, so no scum formation is observed.

■ The raw water inlet comes into contact with a high concentration of microorganisms enclosed in gel, increasing the efficiency of the overall reaction.

[Brief explanation of drawings]

Fig. 1 shows a cross-sectional schematic diagram of an apparatus for explaining the present invention in detail, and Fig. 2 shows an anaerobic upflow blanket method CUA8.
A schematic cross-sectional view of an apparatus for explaining Method B) is shown.

Claims (1)

[Claims] 1. After mixing a slurry of anaerobic microorganisms such as anaerobic digestive bacteria and denitrifying bacteria with organic polymer resins having gel-forming ability or their monomers or prepolymers in the presence of air bubbles, By gelatinization, the anaerobic microbial cells and air bubbles are immobilized, the gel particles are filled into an anaerobic biological treatment tank to form a floating layer, and the liquid to be treated is placed in the floating layer. A method for utilizing anaerobic microorganisms, which is characterized by allowing them to circulate in a downward flow. 2. The method according to claim 1, wherein the gel-forming substance is a urethane prepolymer.