JPH0630781B2 - Short-term startup method for anaerobic fermenter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a short-term start-up method of an anaerobic fermentation tank, and in particular, various industrial wastewater containing organic substances, wastewater such as domestic wastewater typified by urban sewage. When performing anaerobic treatment,
The present invention relates to an anaerobic bioreactor start-up (state until the bioreactor shows normal functions) method.

[Conventional technology]

At the start of anaerobic fermentation, the most important thing is how to accumulate a high concentration of cells involved in methanogenesis.

Conventionally, the anaerobic fermentation method is an anaerobic fluidized bed method, a UASB method,
There is a hybrid UASB method. The UASB method is a method in which bacterial cells are introduced into a fermenter without using a carrier, and after the organic wastewater starts to flow, the bacterial cells spontaneously self-granulate to increase the bacterial cell concentration. Anaerobic fluidized bed method, hybrid UA
In all of the SB methods, an organic or inorganic carrier is introduced into the reaction tank and microorganisms are allowed to adhere to the carrier to increase the cell concentration.

In the UASB method, the high-concentration accumulation and granulation of bacterial cells that can withstand the target treatment amount are derived from anaerobic bacteria with a slow growth rate (eg, Methanothrix bacterium), and among the anaerobic bacteria. However, since it is mainly composed of bacteria suitable for granulation, a start-up period of 3 to 5 months is required.

On the other hand, by adding a polymer flocculant into the anaerobic fermentation tank to artificially granulate the bacterial cells in the fermentation tank or by providing a gravity sedimentation concentration tank at the latter stage of the fermentation tank. Then, a method is known in which the microbial cells flowing out are collected and returned to the fermenter to increase the concentration of the microbial cells. However, these methods also use anaerobic bacteria, which have a slow growth rate, as the dominant species, and cannot significantly shorten the start-up period.

In the anaerobic fluidized bed method and the hybrid UASB method,
Although the outflow of the bacterial cells can be suppressed to a low level because the carrier is put into the tank, there is a disadvantage that the capacity of the fermenter increases by the capacity of the carrier and the efficiency deteriorates.

[Problems to be Solved by the Invention]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems in the prior art and to provide a start-up method for an anaerobic fermenter that can be granulated and concentrated in a short period of time without using a carrier.

[Means for Solving the Problems]

In order to achieve the above object, in the present invention, in the start-up by granulation and high concentration accumulation of cells in an anaerobic fermenter, the genus Methanosarcina in the inoculum containing genus Methanothrix in the fermenter is used. And a short-term start-up method for an anaerobic fermenter, characterized in that the bacterial cells of the bacterium are proliferated and the bacterial cell group containing the genus Methanothrix is granulated in a short period of time with the bacterial cells as a nucleus, and high concentration is accumulated. It was done.

The present invention, in the start-up of the anaerobic fermenter, the genus Methanosarcina genus with granulation is alive, or using a predominant seed cell group, the Methanosarcina genus in the seed cell group is rapidly grown, The method is characterized by forming grain nuclei or adding methanol for that purpose.

[Action]

The cells of the genus Methanosarcina used in the present invention have a higher growth rate than those of the genus Methanothrix, and show a growth rate that is two times or more even when acetic acid is used as a carbon source, and an order of magnitude higher when methanol is used as the carbon source. Also, the diameter is 0.8-1.2 μm,
It is a fungus that aggregates into a tuft of grapes and has the property of aggregating to a maximum of 1-2 mm. In the present invention, the property of the bacterial cell is utilized, the bacterial cell is grown at a high speed at the stage of start-up, and is used as a microbial carrier that replaces an organic or inorganic carrier.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

Example 1 When starting a methane fermentation treatment experiment of a beer manufacturing plant wastewater using a UASB type reactor with a superficial volume of 7.5, two reactors having the same specifications were prepared, and each of them was used as an inoculum and sewage at 35 ° C. fermentation. The digested sludge was enclosed. The concentration of the inoculum was MLVSS 13,400 mg /, and neither the granulated state nor the precursor state thereof was exhibited. Each of these reactors was packed in 4 in each reactor, and 53.6 g was enclosed as MLVSS.
While maintaining the temperature of the reactor at 35 ° C., the supply of beer manufacturing plant integrated wastewater (BOD 450 mg /) as a sample was started. One reactor (hereinafter referred to as reactor A)
In the above, 10 mM (mmol /) of methanol was added to the sample, and the other reactor (hereinafter referred to as Reactor B) was started to be supplied at 20 m / min as the sample alone. The BOD volume load of Reactor A is 3.6 g / .day and Reactor B is 1.7 g / .day.

In Reactor A, the proliferation of Methanosarcina and the formation of a precursor state of granulation with this as a nucleus were confirmed about 20 days after the start of the sample supply, and the number of granules having a diameter of 0.5 mm or more was 210 / m. It also showed a BOD removal rate of 50%. On the other hand, in Reactor B, the state of the inoculum was not changed,
The BOD removal rate was 0.37%. Continue to supply samples 1.
After 5 months, a large amount of granules having a diameter of 1.5 to 2 mm was formed in Reactor A, and most of the remaining granules were in the granule precursor state.
It was possible to confirm 2500 granules / m for granules with a diameter of 0.5 mm or more. Then, in the portion corresponding to the lower two volumes of the reactor, the bacterial cells were accumulated at a high concentration of MLVSS 30,800 mg /, and the BOD removal rate reached 82%. On the other hand, in the reactor B, the granulation precursor state is scattered and the part corresponding to the lower 2 volumes of the reactor is MLVSS 9,700 mg /
And the BOD removal rate was only 55%.

FIG. 1 shows changes in the MLVSS of reactor A and reactor B and the number of granulated products.

Example 2 When starting a methane fermentation treatment experiment of domestic wastewater using a UASB type reactor with a superficial volume of 7.5, two same reactors were prepared and the time required for reactor startup was compared. On the other hand (hereinafter referred to as reactor A),
Sludge obtained by methane fermentation treatment of the wastewater from wooden kettle distillation, which is one step of paper pulp production, at 35 ° C, and on the other hand ((hereinafter referred to as reactor B), sewage digested sludge of 35 ° C fermentation is inoculated. The concentration of inoculum was 10,700 mg / both in both cases.
To each reactor, 5 for each reactor, MLVS
The reactor temperature was maintained at 35 ° C. by enclosing 53.5 g of S. In the inoculum of Reactor A, the genus Methanosarcina was the priority species. The inoculum of Reactor B did not exhibit not only the granulated state but also its precursor state. A sample of domestic wastewater (BOD 220 mg /) was supplied to both reactors at 45 m / min. BO of reactors A and B
D volume load is 1.9 g / day.

In Reactor A, one month after the start of the sample supply, the formation of granules with the genus Methanosarcina existing in the inoculum was confirmed, and the number of granules with a diameter of 0.5 mm or more was 790 pieces / m. . On the other hand, in Reactor B, no change was observed in the state of the inoculum, and the suspension substances contained in the sample became conspicuous. After 2.5 months of continuous sample supply,
In the reactor A, a large amount of granules having a diameter of 1.5 to 2 mm were formed, and most of the remaining granules were in the granule precursor state. The number of granules having a diameter of 0.5 mm or more was 1540 / m. And
The part corresponding to the lower two volumes of the reactor is MLVSS
The amount of removal of BOD was 21,600 mg / 69%.

On the other hand, in the reactor B, the granulation precursor state is scattered, and the part corresponding to the lower two volumes of the reactor is MLVS.
S 13,700 mg /, and the BOD removal rate was 41%.

FIG. 2 shows changes in the MLVSS of reactor A and reactor B and the number of granulated products.

〔The invention's effect〕

 The present invention has the following effects.

i) The time required for start-up is shortened by using a microbial carrier having a very high growth rate.

ii) The carrier itself is a microorganism and acts as a microorganism capable of treating wastewater even after the formation of a nucleus, and the efficiency of the reactor does not deteriorate as in the case of using an organic or inorganic carrier.

[Brief description of drawings]

FIG. 1 shows MLVSS according to the elapsed time of the sample of Example 1.
2 is a graph showing changes in the number of granulated products, and FIG. 2 is a graph showing changes in the number of MLVSS and the number of granulated products according to the elapsed time of the sample of Example 2.

Claims (2)

[Claims] 1. In a start-up by granulation and high concentration accumulation of cells in an anaerobic fermentation tank, cells of the genus Methanosarcina are grown in a group of seed cells containing the genus Methanothrix in the fermentation tank, A short-term start-up method for an anaerobic fermenter, which comprises granulating a high concentration of high-concentration seed cells containing the genus Methanothrix with the cells as the nucleus. 2. The short-term start-up method for an anaerobic fermentation tank according to claim 1, wherein methanol is added to the inside of the fermentation tank.