JPH06246288A - Operation method for high temperature upward stream type anaerobic sludge bed device - Google Patents

Abstract

PURPOSE:To provide a reliable operation method in which the steady operation can be performed within a short period of time and the high temperature granular sludge can be formed securely by means of an easy operation control and other features can be performed in a high UASB device operating more efficiently than a medium temperature UASB device. CONSTITUTION:Medium temperature granular sludge prepared as seeding sludge by a medium temperature anaerobic treatment device is used, and the process is started from a temperature zone in the high temperature methane fermentation treatment, and the operation is carried out while salts such as Fe, Ni and Co as nutrient salt is controlled to the given quantities in the operation method for a high temperature upward stream type anaerobic sludge floor device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating an upflow type anaerobic sludge bed apparatus (hereinafter referred to as UASB apparatus) for biologically performing methane fermentation treatment of organic wastewater such as food wastewater in a high temperature range. .

[0002]

2. Description of the Related Art As a conventional UASB apparatus, a medium temperature UASB apparatus having a processing temperature of 30 to 40 ° C. is generally used, and a high temperature UASB apparatus having a processing temperature of 45 to 60 ° C. is rarely used.

It is known that the high-temperature UASB apparatus treats with high-temperature granule sludge having a high methanogenic activity, so that it has an excellent ability to decompose organic substances and can efficiently perform methane fermentation treatment with a high volume load. in spite of,
The reason why it is not widely practiced is that methane bacteria of high temperature digested sludge used as seed sludge for granule formation are very difficult to form granules, and even if granules are formed, it takes a long time, or This is because a reliable operation method for granule formation has not been established.

However, the conventional high temperature UASB apparatus has been partially implemented, and various methods have been earnestly studied even in the start-up method which is the most important for its operation. The conventionally known start-up method will be described below.

Since most digester tanks of sewage treatment plants use medium-temperature methane fermentation treatment, they are most easily available as planted sludge,
Also, by using a medium temperature digested sludge composed of a group of methane bacteria with a shape suitable for granule formation, start up from the temperature range of medium temperature methane fermentation and gradually increase to the temperature range of high temperature methane fermentation while acclimatizing. , A method of forming high temperature granulated sludge. This method has drawbacks that it takes a long time to form granules, and operation management such as temperature increase and load increase is very difficult.

Although it is more difficult to obtain than medium-temperature digested sludge, the high-temperature digested sludge obtained from the digestion tank of the high-temperature methane fermentation treatment is used as the seed sludge, and the temperature range of the high-temperature methane fermentation is used for starting.
How to upgrade. In this method, as described above, high temperature digested sludge hardly forms granules and it takes a long time to granulate, and a reliable operation method for granule formation has not been established.

A method of starting up from the temperature range of medium temperature methane fermentation by using medium temperature granule sludge obtained from the medium temperature UASB apparatus which is being used as a seed sludge. This method can shorten the period of granule formation, but like the method using medium-temperature digested sludge, it has the drawback that operation management such as temperature rise and load increase is difficult and the treatment performance is not stable for a long time.

Further, from the beginning, high temperature granulated sludge was used as a seed sludge, and the temperature range of high temperature methane fermentation was changed to start.
How to upgrade. Although this method has the shortest start-up period and easy operation management, it has a drawback in that the number of high temperature UASB devices currently in operation is extremely small and it is difficult to obtain high temperature granulated sludge.

[0009]

As described above, each of the start-up methods in the high temperature UASB device which has been studied or implemented conventionally has a difficult problem, and the high temperature UASB device has been popularized. The current situation is that there are none.

Therefore, according to the present invention, since a high temperature UASB apparatus capable of more efficient treatment than a medium temperature UASB apparatus is spread, steady operation can be performed in a short period of time, and high temperature granules can be surely secured by easy management. It is formed for the purpose of providing a reliable operation method such as being formed.

[0011]

Means for Solving the Problems The gist of the present invention for achieving the above-mentioned object is to provide a method for methane fermentation treatment of organic wastewater with a high temperature UASB apparatus, in which a medium temperature anaerobic treatment apparatus is used as seed sludge. Operation of a high-temperature UASB device characterized by starting up from a temperature range in high-temperature methane fermentation treatment using granule sludge and operating while controlling salts of Fe, Ni, and Co as nutrient salts to predetermined amounts Is the way.

[0012]

[Operation] The method of treating organic wastewater with the UASB device is as follows:
The wastewater is circulated upward from the lower part of the reaction tank of the UASB device filled with the granule sludge formed by methane bacteria to form a fluidized sludge bed of the granule sludge, and organic matter in the wastewater is sludge bed methane. A fermentation process is carried out in which the biological action of the fungus decomposes and decomposes into methanation.

Next, the wastewater treated in the sludge bed flows upward together with the produced gas, and gas-treated water-in the upper part of the reaction tank.
It is separated into three phases of sludge. Gas and treated water are discharged from the upper part of the reaction tank to the outside of the system, and sludge is settled and circulated in the lower sludge bed, whereby the sludge bed is always maintained in a stable state.

As the granule sludge to be filled,
Using medium-temperature granule sludge that has already been formed by the medium-temperature UASB device, raising the temperature to 45-60 ° C, which is the temperature range for high-temperature methane fermentation, to start-up and maintaining it continuously, thereby increasing the temperature. Is unnecessary.

In the past, from experience with the treatment of medium-temperature digested sludge, when the temperature was set to a high temperature range from the time of start-up, the medium-temperature methane bacteria forming the granules were killed, and the granules were destroyed and flowed out together with the treated water. However, it was thought that the treatment efficiency would decrease, but the granules of mesophilic methane bacteria are not easily affected by temperature changes, and they are entwined with each other to form a strong bond, and the bond is not easily broken. There was found.

The medium-temperature granulated sludge has a high methanogenic activity even in a high temperature range, and the inside of the granule is suitable for growth of high-temperature methane bacteria (acetic acid concentration near the cells is 200 m).
It was also found that by keeping it at a level of g / l or less), high-temperature methane bacteria efficiently grow and adhere and immobilize inside and on the surface of the granules, so that the bacterial cells do not easily flow out.

In the above-mentioned start-up and continuous operation in the high temperature range, by controlling the concentration of nutrient salts such as Fe, Ni and Co to a certain amount or more, the growth of high temperature methane bacteria and the improvement of methanogenic activity are improved. Thus, high load operation becomes possible.

The concentrations of the nutrient salts such as Fe, Ni and Co are Fe: 1 × 10 ^-5 Fe / COD _Cr , N
i: 1 × 10 ⁻⁶ Ni / COD _Cr , and Co: 1 × 10 ⁻⁶
It is necessary to control the concentration to at least Co / COD _Cr .

The concentrations of Fe, Ni, Co, etc. with respect to COD _Cr differ depending on the properties of the wastewater. The acid-fermented wastewater may be less than the untreated wastewater, and N and P as other nutrient salts. The concentration of etc. is appropriately adjusted depending on the properties of the wastewater.

[0020]

EXAMPLE An organic wastewater, which uses starch as a single carbon source, and synthetic wastewater (hereinafter referred to as raw water) having a total COD _Cr concentration of 25,000 mg / l, is used as an example of the method of the present invention and a conventional method. About the test comparing the method.

(Example 1) An acid fermentation unit in which high temperature digested sludge was planted was provided as a pretreatment unit, and raw water after the acid fermentation treatment was introduced into a high temperature UASB apparatus in which the planted sludge was different from that of the planted sludge. Was examined.

Nutrient salts were added to raw water to control the components to the following concentrations. _{N: COD Cr × 1.1 × 10} -2 mg / l ( urea _{addition) P: COD Cr × 2.6 ×} 10 -3 mg / l ( added _{phosphate) Fe: COD Cr × 3.1 ×} 10 - ⁴ mg / l (addition of ferrous chloride) Ni: COD _Cr x 1.7 x 10 ^-5 mg / l (addition of nickel chloride) Co: COD _Cr x 1.3 x 10 ^-5 mg / l (addition of cobalt chloride) )

The test conditions are as follows:
6.0, residence time 24HR, temperature 52 ° C, high temperature UAS
The temperature of the apparatus B was set to 52 ° C., and when the concentration of the volatile organic acid in the treatment liquid was 1,000 mg / l or less and the COD _Cr removal rate was 80% or more, the volumetric load was increased by 30%.

As the seed sludge filled in the high temperature UASB apparatus, No. 1: 10 kgvss / m ^{3 was} charged as the sludge concentration at the start-up of medium-temperature granulated sludge, and the sludge had a methanogenic activity of 0.4 kgCH ₄ -COD _Cr / kgvs
s. It was d. No. 2: Medium temperature digested sludge was packed at 5 kgvss / m ³ as the sludge concentration at start-up, and the methanogenic activity of this sludge was 0.01 kg CH ₄ -COD _Cr / kgvss. It was d. No. 3: High-temperature digested sludge was packed at 5 kgvss / m ³ as the sludge concentration during start-up, and the methanogenic activity of this sludge was 0.4 kgCH ₄ -COD _Cr / kgvss. It was d.

The results of the above test are shown in FIG. From the figure, the No. In the method of planting the medium-temperature granulated sludge of No. 1 as described above, a high volume load can be obtained at the time of start-up, and a normal volume load of about 30 kg COD _Cr / m ³ . It was confirmed that it was d or more and that a higher load operation was possible.

In addition, No. In the method of planting medium temperature digested sludge of No. 2, if the volume load is increased, the COD _Cr removal rate decreases and the load increase condition is no longer satisfied, so the load hardly increases and the granules are also confirmed. could not.

Still another comparative example No. 3 In the method of planting high temperature digested sludge, some granules are started from around 30 days.
However, the volumetric load did not reach the above normal load operating condition even after 50 days.

(Example 2) An acid fermentation section in which high temperature digested sludge was inoculated was provided as a pretreatment section, and raw water after the acid fermentation treatment was introduced into a high temperature UASB apparatus in which medium temperature granulated sludge was inoculated, and Fe , The method of adding the nutrient salts of Ni and Co (No. 1 of Example 1) and the method of not adding the nutrient salts (No. 4) were examined, and the influence of the nutrient salts was examined.
The raw water condition and the test conditions were the same as in Example 1.

The results of the above test are shown in FIGS. 2, 3 and 4.
It was shown to. As described above, the method of the present invention in which the nutrient salt is added from the figure shows that the normal volume load is about 30 kg COD _Cr / m ³ .3 in a short period of about 30 days. It was confirmed that higher load operation was possible, and the methanogenic activity was 50% after 2 days of the medium temperature UASB device (temperature 35 ° C).
It was more than doubled.

No. 3 which is a comparative example. In the method in which the nutrient salt of 4 was not added, the sludge concentration in the high temperature UASB device was hardly increased, and the methanogenic activity of the sludge was not increased. Therefore, when the volume load is increased, the COD _Cr removal rate decreases, so that even after 50 days, the COD _Cr removal rate could only be increased to about 1/3 of that of the method in which the nutrient salt was added.

(Example 3) Using acetic acid as a single carbon source, the total C
Using synthetic wastewater with an OD _Cr concentration of 3,000 mg / l as raw water, introducing into a high temperature UASB apparatus in which medium-temperature granulated sludge was planted, and a method of adding nutrient salts of Fe, Ni and Co, and a method of not adding Were tested and the effects of nutrients were examined.

The nutrient concentration of raw water was controlled to the following concentrations. _{N: COD Cr × 1.4 × 10} -2 mg / l ( urea _{addition) P: COD Cr × 2.9 ×} 10 -3 mg / l ( added _{phosphate) Fe: COD Cr × 1.0 ×} 10 - ⁵ mg / l (addition of ferrous chloride) Ni: COD _Cr x 2.0 x 10 ^-6 mg / l (addition of nickel chloride) Co: COD _Cr x 2.0 x 10 ^-6 mg / l (addition of cobalt chloride) )

The test conditions are high temperature UA without acid fermentation tank.
The temperature of the SB device was 52 ° C., and the other conditions were the same as in Example 1.

In the method of the present invention in which nutrient salts are added, about 3 is added.
About 50 kg COD _Cr / m ^{3 in} 0 days. Although stable treatment was possible with a high volume load of not less than d, the method of the comparative example in which no nutrient salt was added was about 20 kg COD _Cr / m ³ . d
It became possible to process the above.

Also, as in Example 2, the sludge concentration and the methanogenic activity were remarkably increased in the method of the present invention in which the nutrient salt was added, but in the method of the comparative example in which the nutrient salt was not added, the sludge was increased. Almost no increase was observed in the methane production activity or the methanogenic activity.

From the above examples, the method of the present invention in which a medium temperature granulated sludge is used as a seed sludge and a predetermined amount of salts of Fe, Ni and Co are added and controlled as a nutrient salt in a high temperature UASB apparatus is extremely effective. It turns out to increase.

[0037]

EFFECT OF THE INVENTION The operation method of the high temperature upward flow type anaerobic sludge bed apparatus of the present invention has the following effects. According to the method of the present invention, a granular sludge having a higher methanogenic activity than that of a medium-temperature UASB apparatus can be obtained, which has an excellent ability to decompose organic substances and enables efficient treatment with a high volume load.
The SB device can be operated in a steady state for a short period of time by using an easily available medium-temperature granulated sludge, and can be surely converted to high-temperature granular sludge with easy management, which is a highly reliable operating method. .

[Brief description of drawings]

FIG. 1 is a graph of volume load and COD _Cr removal rate in Example 1.

FIG. 2 is a graph of volume load and COD _Cr removal rate in Example 2.

FIG. 3 is a transition graph of sludge concentration in Example 2.

FIG. 4 is a transition graph of methanogenic activity in Example 2.

Claims (1)

[Claims] 1. A method for methane fermentation treatment of organic wastewater by a high temperature upflow type anaerobic sludge bed apparatus, wherein high temperature methane fermentation is performed by using medium temperature granule sludge obtained from a medium temperature anaerobic treatment apparatus as seed sludge. A method for operating a high-temperature upward-flow anaerobic sludge bed apparatus, which is started up from a temperature range during treatment and is operated while controlling salts of Fe, Ni, and Co as nutrient salts to predetermined amounts.