JPS63158194A - Biological treatment of organic sewage - Google Patents

Abstract

PURPOSE:To efficiently perform purifying treatment, by packing a reaction tank with particles wherein a biofilm is grown and immobilized on the surfaces of fine particles. CONSTITUTION:An immobilized bacteria bed 5 packed with immobilized bacteria is formed on the perforated plate 3 in a reaction tank 2. Organic sewage W1 is supplied to the lower part of the reaction tank 2 through an introducing pipe 6 and allowed to rise and pass through the immobilized bacteria bed 5 to be treated while an upward stream is formed through the perforated plate 3. The immobilized bacteria allowed to pack the immobilized bacteria bed are prepared by forming a biofilm to solid carrier particles composed of sand or activated carbon using an immobilizing material such as polyacrylamide, K-carageenan or calcium alginate and immobilizing biofilm particles. By this method, the reaction tank is easily made compact.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a biological treatment method for Jt organic sewage, in particular, it is a method for efficiently treating organic sewage containing ammonia nitrogen, etc. using immobilized microorganisms. It concerns how it can be done.

[Prior Art] In recent years, in the field of microbial utilization industry, various techniques for efficient operation by immobilizing enzymes have been studied, and some have already entered the stage of practical application. In this way, immobilization technology has mainly been researched on enzymes, but recently research has been gradually conducted on directly immobilizing microorganisms for the purpose of using the microorganisms themselves as solid catalysts. Some results have been obtained using microorganisms to produce fructose, amino acids, organic acids, etc.

On the other hand, biological treatment methods using microorganisms are widely used as a method for treating organic wastewater, but no technology using immobilized microorganisms has been attempted to date. In addition to the activated sludge method that has been used since then, research and development has been progressing on a method called the biofilm method. The above-mentioned biological removal methods are exemplified by the single-rotation disk method, contact aeration method, fluidized flow method, bed method, etc., and improvements in efficiency by increasing the concentration of microorganisms in the reaction tank are being discussed. Among the biofilm methods listed above, the fluidized bed method is one that has achieved a particularly high concentration of microorganisms, and the size of processing bags is being reduced by this method.

[Problems to be Solved by the Invention] However, some problems remain even in the above fluidized bed method. In other words, as a biological treatment method for organic wastewater applying the fluidized bed method, for example, a solid-liquid two-phase fluidized bed involving a denitrification reaction is exemplified to clarify the problem. When biofilm grows excessively, the particles (
The apparent specific gravity of the biofilm particles (hereinafter sometimes referred to as biofilm particles) decreases, and as a result, the biofilm particles float above the fluidized bed and flow out of the tank together with the treated water, impeding stable operation. A situation arises. As a countermeasure, attempts have been made to install a mechanical agitation mechanism in the fluidized bed tank and use agitation to detach the enlarged biofilm, and although this has been somewhat effective, new problems have arisen, such as an increase in power costs.

On the other hand, in a gas-solid-liquid three-phase fluidized bed for aerobic treatment such as BOD removal or nitrification, the tank of biofilm particles as described above in a two-phase fluidized bed is Outflow can be prevented.

On the other hand, the biofilm separated from the biofilm particles becomes finer, but the biofilm corresponds to surplus sludge in the activated sludge method. Therefore, in order to obtain a treatment effect, it is necessary to remove this, but it has the disadvantage that it is difficult to sediment and separate it as it is because it is extremely fine. Furthermore, when the inflow volume of wastewater to be treated increases due to rainfall, etc., it is inevitable that 1 g of biofilm particles will flow out of the tank, and this is the same in a two-phase fluidized bed.

In the fluidized bed system, from the viewpoint of retaining microorganisms at a high concentration, it is advantageous to make the particle size of the solid carrier particles as small as possible and to increase the surface area of the biofilm particles in the tank as much as possible. However, in the two-phase fluidized bed, the outflow of biofilm particles to the outside of the tank is further facilitated, while in the three-phase fluidized bed, the biofilm particles and the treated water are rapidly separated into solid and liquid. In this case, some means must be taken to increase sedimentation separation, and as in the case of a two-phase fluidized bed, biofilm particles tend to flow out of the tank. From this point of view, it is said that the particle size of sand, which is generally used as solid carrier particles in a fluidized bed system, is limited to a size of about 1 mm or 2 mm.

Therefore, in view of the above-mentioned current situation, the present inventors immobilized microorganisms to make them difficult to leak out.

The present invention was completed based on the idea that the problems of conventional fluidized bed systems could be solved all at once, and that organic sewage could be treated more efficiently.

[Means for solving the problem] The present invention involves growing a biofilm on the surface of fine particles, then immobilizing the particles by applying an entrapment method, and then filling the immobilized particles into a reaction tank. The main point is that the system is operated by

[Function] The inventor has been conducting research on various sewage treatment technologies such as activated sludge method and fluidized bed method for many years, and as a result of the research, the following findings were obtained. In other words, biofilm particles with excessive biofilm growth on their surfaces have not received much attention because their apparent specific gravity decreases and the aforementioned problems have been pointed out. As a result of the measurement, remarkable results shown in FIGS. 2 and 3 were obtained. Figure 2 shows the relationship between denitrification rate per activated sludge concentration (MLVSS) and water temperature, and Figure 3 shows the relationship between nitrification rate per MLVSS and water temperature. For comparison, FIGS. 2 and 3 respectively show the denitrification rate and nitrification rate when long-term and intermittent aeration is used in the aeration tank in a nitrogen removal apparatus using the activated sludge method.

As is clear from Figures 2 and 3, the denitrification and nitrification rates in the fluidized bed method are much higher than those in the activated sludge method at any water temperature;
o times and the nitrification rate is 4 to 7 times higher. Therefore, compared to the activated sludge method, there are more denitrifying bacteria on the surface of the biofilm particles.
It is understood that nitrifying bacteria and the like are growing at higher concentrations. As a result, we obtained confirmation that biofilm particles can be effectively used in wastewater treatment technology as long as the aforementioned problems are resolved.

In addition, in the activated sludge method whose results are shown in Figures 2 and 3, approximately 0.05 Kg 1I800 /kg NLVSSll
dat (7) It was operated at a low load, and the sludge retention time (SRT) was 40 to 50 days, but no nitrifying bacteria or denitrifying bacteria were observed to flow out during that time. In addition, the activated sludge concentration (MLVSS) in the above activated sludge method is 2100 to 2.
700 mg/l, whereas the MLVSS of biofilm particles in the denitrification tank and nitrification tank in the fluidized bed method was 4, respectively.
800-7800g/kou and 5000-7500g
/, and if you compare their average values, it is about 2.6 times as large.

Furthermore, when comparing the denitrification and nitrification power of the two methods, the fluidized bed method has a 21 to 2
6 times and 10-18 times.

Next, the present inventor attempted to immobilize biofilm particles based on the above findings. Although the means for fixing the biofilm particles is not similarly limited, the following configuration can be adopted as an example thereof. That is.

Using fine particles (solid carrier particles) with a particle size of less than 0.15 m, biofilm particles are formed by batch culture with one intermittent aeration, and the biofilm particles are concentrated in a centrifuge for minutes. Thereafter, the entrapment method is applied to immobilize the biofilm particles to form pellets or beads each having a particle size of about 2 to 3 layers of intestines. The entrapment method here is a conventionally known enzyme immobilization technique in which microorganisms are encapsulated in a gel lattice of a polymer (immobilization material) and immobilized in a state where they cannot be detached.

As for the solid carrier particles, they may be selected as appropriate from those on which nitrifying bacteria, denitrifying bacteria, organic matter oxidizing bacteria, etc. can adhere and grow in high concentrations, such as sand, activated carbon, coke, zeolite, chamotte, lightweight particles, etc. Examples include aggregate and vinyl chloride resin. The finer the particle size of the solid carrier particles, the better, and in the present invention, the particle size is 0.1.
It is desirable to use solid carrier particles of ~0.15 mm or less. When performing batch culture with intermittent aeration, if the sedimentation rate of biofilm particles is slow, add a biopolymer extracted from microorganisms or a reprinted polymer flocculant. do it.

On the other hand, various types of immobilization materials used in the comprehensive method are known and are not limited in any way, but examples include polyacrylamide, k-carrageenan, calcium alginate,
Examples include photocurable urethane resin and polyvinyl alcohol. Especially relatively cheap polyvinyl alcohol,
The gel obtained by freezing-thawing has high mechanical strength and is not toxic to microorganisms, making it an excellent immobilizing material. The particle size of the immobilized microorganisms to be produced is desirably about 2 to 30 layers or less, taking into account the diffusion of the substrate and product within the gel.

In the present invention, when sand, lightweight aggregate, etc. are used as solid carrier particles, the specific gravity of the resulting immobilized microorganisms is higher than that of known immobilized microorganisms that concentrate and immobilize microorganisms. Get bigger.

Since the particle size is about 10 times that of biofilm particles in a fluidized bed, the sedimentation rate is also high. Therefore, in the reaction tank using immobilized microorganisms according to the present invention, the conventional two-phase Fi,
A creature that looks like it's headed for a moving bed! There is no outflow of particles out of the tank, and the sedimentation and separation section for biofilm particles, such as in a three-phase fluidized bed, can be made as small as possible.

Furthermore, the immobilized microorganism according to the present invention can be used not only in a fluidized bed type reaction tank but also as a packed bed (fixed bed). In that case, the concentration of microorganisms can be further increased than that in the fluidized bed, which not only makes it possible to further improve the force efficiency, but also eliminates the need for strong stirring, which is an essential condition for three-phase fluidized beds. The excess sludge has good sedimentation properties, and clear treated water can be easily obtained. However, by adopting the structure of the industrial water invention, not only can the problems in the conventional technology be solved at once, but also one
It is possible to maintain a higher concentration of microorganisms in the reaction tank, and one reaction tank can be simplified and made more compact.

[Example] First, the present inventor produced an immobilized microorganism according to the procedure shown below.

In a batch culture tank with an internal volume of 1O1 and a stirrer,
．． Lightweight aggregate that passes through a sieve of 082 as, with an apparent volume of JA1
1 was added, and secondary treated water from the sewage treatment plant was added to make 7 samples. Hiiragi, peptone and meat extract are used as organic sources. BOD
820 g/l, Kjeldahl nitrogen 130 mgl,
After injecting synthetic sewage 31 containing 25 grams/liter of total phosphorus into the batch culture tank for 10 minutes, intermittent aeration of 5 minutes of aeration and 1:5 minutes of aeration stop was repeated 6 times. After a further 45 minutes of standing, 5
The supernatant water 31 was discharged in 1 minute, and 3 parts of synthetic sewage water was again injected in 10 minutes.

The cycle of intermittent aeration → standing → supernatant water discharge was automatically performed according to the operating procedure shown in FIG. 4 (timing chart). The water temperature was kept at 25° C. for rAT1, and batch culture was carried out for 50 days.

The biofilm particles thus obtained were separated and concentrated using a centrifuge, and mixed with 2.5 times the volume of a 17% polyvinyl alcohol solution to form a mixture.

The polyvinyl alcohol used had a polymerization degree of 1700. It has a saponification value of 119.85% or more. The above mixture was extruded into a Teflon tube with an inner diameter of 3 and 1, and the extrudate was heated at -20°C.
After putting it in the freezer for 24 hours, thaw it at room temperature and return it to -20℃.
The repeated operation of placing the sample in a freezer for 12 hours was performed 5 times. Thereafter, the pellet was stored in a refrigerator at 5° C. for 24 hours, and a pellet of immobilized microorganisms with a diameter of 3 mm and a length of 3 mm was prepared.

Next, the present inventor conducted an experiment regarding the nitrogen removal ability of the obtained immobilized microorganism. Processing bag fa used in the experiment
A schematic diagram of t is shown in FIG.

The reaction tank 2 of the processing bag 21t is made of acrylic resin and has an inner diameter of 5c and a height of 25c. An immobilized microorganism layer 5 filled with immobilized microorganisms is formed above the perforated plate 3 in the reaction tank 2 in which the trachea 4 is disposed.Synthetic sewage W! is supplied to the lower part of the reaction tank 2 via the introduction pipe 6.

The immobilized microorganism layer 5 forms an upward flow through the perforated plate 3.
rise and pass through. At this time, the oxygen-containing gas G is supplied to the gas introduction pipe 7. and is intermittently fed into the lower part of the reaction tank 2 via the aeration pipe 4. As the oxygen-containing gas G, one containing 85% oxygen was used, and the intermittent feeding was performed by controlling the opening and closing of a solenoid valve lo provided in the gas introduction pipe 7 using a timer T.

The synthetic sewage W1 supplied to the reaction tank 2 has an immobilized microorganism layer 5.
Organic matter, nitrogen, etc. are removed as the water rises through the reactor tank 2, and the treated water W2 is discharged through the overflow weir 8 and discharge pipe 9 at the upper part of the reactor tank 2. The temperature is adjusted to 25° C. by immersing the tank 2 in a constant temperature water bath.

The synthetic sewage Wl is the same as that used when producing the immobilized microorganisms. The amount of immobilized microorganisms in the immobilized microorganism layer 5 is 5001 in apparent capacity, and the synthetic sewage W
! The amount of water injected is 260 m1/hr, and the BOD load is l O
Kg*BOD/m3*day. The aeration conditions were intermittent aeration with an aeration time of 5 minutes and an aeration stop time of 5 minutes. The flow rate of the oxygen-containing gas G was adjusted so that the dissolved oxygen concentration in one reaction tank z was 4 to 5 sg/i 5 minutes after the start of aeration.

The treated water W2 thus obtained was filtered through a filter paper and then analyzed. The average analysis value is BOD: 4mg/sentence, N
Ha-N: 0.3 g/l T-N: 1. ?
■g/I saw it. Furthermore, the amount of surplus sludge produced was on average 12% of the removed BOD.

The above experiment was conducted for three consecutive months, during which time the immobilized microorganisms were extremely strong, and the MLvS in the filling volume A5001 was
S content was maintained at about 15,000 mg/l, and organic matter and nitrogen were removed smoothly.

[Effects of the Invention] As described above, according to the present invention, various problems described in the prior art can be solved by applying the immobilized microorganism according to the present invention to biological treatment such as organic sewage treatment. Not only can the problems be solved all at once, but the device can also be made even simpler and more compact.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the treatment equipment l, Figure 2 is a graph showing the relationship between denitrification rate per MLVSSm and water temperature, and Figure 3 is a graph showing the relationship between denitrification rate per MLVSSm and water temperature.
A graph showing the relationship between the nitrification rate per LvSS and water temperature, and FIG. 4 is a timing chart showing the operating conditions when producing biofilm particles by batch culture.

Claims (1)

[Claims] Biology of organic sewage characterized by growing a biofilm on the surface of fine particles, then immobilizing the particles by applying an entrapment method, and then filling a reaction tank with the immobilized particles for operation. processing method.