JP2018015692A - Method for anaerobically treating organic waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating organic waste water, wherein a starting operation period of an anaerobic reaction vessel is shortened.SOLUTION: This invention relates to an anaerobic treating method, comprising treating organic waste water by making the waste water pass through an anaerobic reaction vessel that holds a carrier capable of carrying anaerobic microorganisms, wherein granule sludge is used as a seed sludge. When starting the passage of the organic waste water through the reaction vessel, a bulk volume of the seed sludge per bulk volume of the carrier is in a ratio of 6-50 inclusive. In the CODdesign load of the anaerobic reaction vessel, by the time S-CODrejection reaches 90%, the seed sludge is additionally put at least once.SELECTED DRAWING: None

Description

  The present invention relates to an anaerobic treatment method for organic wastewater, and in particular, shortens the startup operation period until anaerobic microorganisms adhere to a non-biological carrier to form a highly active biofilm on the surface of the non-biological carrier. The present invention relates to an anaerobic treatment method for organic wastewater.

  Examples of a method for treating organic waste water using microorganisms include aerobic biological treatment and anaerobic biological treatment. Among the anaerobic biological treatments, methane fermentation treatment uses a metabolic reaction of anaerobic microorganisms that grow in an anaerobic environment without oxygen to decompose organic matter in organic wastewater into methane gas, carbon dioxide, etc. Compared with aerobic biological treatment, there is a merit that the amount of sludge generated is small and no electricity costs such as blower (aeration) are required, so there is no running cost, and the generated methane gas can be used effectively In recent years, it has attracted particular attention as a method for treating organic wastewater.

  As the methane fermentation treatment method, for example, UASB (abbreviation of Upflow Anaerobic Sludge Blanket) method, fixed bed method, fluidized bed method and the like are known. In particular, the UASB method uses granule sludge that is granulated into granules by contact with anaerobic bacteria such as methane bacteria, acid-producing bacteria, and sludge, thereby reducing the concentration of methane bacteria in the reaction tank. As a result, it can be maintained at a high concentration, and as a result, it can be efficiently treated even when the concentration of organic matter in the wastewater is considerably high. However, organic wastewater mainly composed of low molecular organic substances such as methanol and formaldehyde discharged from chemical factories has a problem that it is difficult to form and maintain granular sludge.

Further, when COD _Cr (oxygen demand by potassium dichromate) is intended for low-concentration raw water of 2000 mg / L or less, COD _Cr volumetric load of 10 kg / (m ³ .multidot.m, which is a design load in a general UASB treatment method. If you try to operate in d), the amount of organic wastewater will be excessive and the linear velocity LV (Liner Velocity) in the UASB reaction tank will exceed 3 m / h, so granule sludge will flow out of the UASB reaction tank. It becomes difficult to maintain the amount of sludge in the UASB reaction tank.

  As a measure to maintain the required amount of sludge in the UASB reaction tank, the granular sludge is present in the UASB reaction tank with a non-biological carrier and methane bacteria granules in a volume ratio of 100: 5 to 100: 500. A start-up operation method for starting the passage of organic waste water has been proposed (Patent Document 1). However, since it takes time for the methane bacteria granules to adhere to the non-biological carrier and form a biofilm, the granule sludge is disassembled before the biofilm is formed on the non-biological carrier and the methane bacterium flows out. Therefore, in order to secure the required amount of methane bacteria granules during steady operation, it is necessary to add a large amount of granular sludge at the start of water flow.

  The reaction vessel is charged with methane bacterium aggregates obtained by pulverizing the carrier and methane bacterium granules, and the reaction vessel is started up in a state where methane bacterium aggregates per liter of the carrier are present in the range of 1 to 900 g. (Patent Document 2). However, because the methane bacteria granules are pulverized, the sedimentation rate is reduced and it becomes easy to flow out of the reaction tank, and the desired amount of sludge cannot be maintained during the start-up operation. It is necessary to input a large amount of methane bacteria granules in anticipation of the amount.

Japanese Patent No. 5658902 JP, 2014-100680, A

An object of this invention is to provide the organic wastewater treatment method which shortened the starting operation period of the anaerobic reaction tank.
Another object of the present invention is to provide an organic wastewater treatment method that can reduce the need for maintenance of sludge amount according to load fluctuations.

Embodiments of the present invention are as follows.
[1] An anaerobic treatment method in which organic waste water is passed through an anaerobic reaction tank holding a carrier capable of supporting anaerobic microorganisms,
Granule sludge is used as seed sludge,
At the start of passing organic wastewater, the bulk capacity of the seed sludge is set to a ratio of 6 to 50 with respect to the bulk capacity 1 of the carrier,
An anaerobic treatment method for organic wastewater, wherein the carrier is additionally charged at least once before the S-COD _Cr removal rate reaches 90% in the COD _Cr design load of the anaerobic reaction tank.
[2] An upflow anaerobic reaction tank holding a carrier capable of supporting anaerobic microorganisms;
A carrier introduction pipe for introducing the carrier during the startup operation period of the upward flow anaerobic reaction tank;
A valve for controlling the introduction of the carrier from the carrier introduction pipe into the upward flow anaerobic reaction tank;
An anaerobic treatment apparatus for organic wastewater, comprising:
[3] An acid fermentation tank provided in a front stage of the upward flow anaerobic reaction tank;
Acid fermentation treated water introduction pipe for sending acid fermentation treated water from the acid fermentation tank to the upward flow anaerobic reaction tank;
The anaerobic treatment apparatus for organic wastewater according to [2], further comprising:

  According to the anaerobic treatment method of organic wastewater of the present invention, the granular sludge that becomes seed sludge at the start of water flow is present around the carrier to increase the contact frequency between the carrier and the microorganism, By promoting the adhesion, adding a new carrier according to the degree of microbial adhesion to the carrier, and maintaining a state where there is always a granular sludge or a carrier with microorganisms attached around the new carrier, The sludge load can be controlled, and startup is possible with stable treatment. Moreover, the start-up period can be shortened by maintaining an appropriate amount of anaerobic microorganisms in the reaction tank.

It is explanatory drawing which illustrated the outline | summary of one form of the organic wastewater treatment method of this invention. It is explanatory drawing which shows an example of schematic structure of a methane fermentation tank as an anaerobic reaction tank. It is explanatory drawing which shows another example of schematic structure of a methane fermentation tank as an anaerobic reaction tank. It is a schematic diagram of a normal granule sludge cross section. It is a schematic diagram of the granular sludge adhering to a support | carrier. It is a graph which shows the daily change of the COD _Cr volumetric load (upper stage) and the S-COD _Cr removal rate (lower stage) of the comparative example 1. It is a graph which shows the daily change of the COD _Cr volumetric load (upper stage) and the S-COD _Cr removal rate (lower stage) of the comparative example 2. It is a graph which shows the time-dependent change of the COD _Cr volumetric load (upper stage) of Example 1, and a S-COD _Cr removal rate (lower stage). It is a graph which shows the daily change of the COD _Cr volumetric load (upper stage) of Example 2, and a S-COD _Cr removal rate (lower stage).

Embodiment

  FIG. 1 is an explanatory view illustrating the outline of one embodiment of the organic wastewater treatment method of the present invention. Generally, in organic wastewater treatment, raw water (organic wastewater) is treated in an acid fermentation treatment tank, then introduced into a methane fermentation tank, subjected to anaerobic treatment, and the resulting treated water is sent to the treatment water tank. The treated water from the treated water tank may be returned to the acid fermentation tank and / or the methane fermentation tank and used for controlling the upward flow rate in the tank.

  The methane fermentation tank in the present invention employs an anaerobic fluidized bed system in which an anaerobic microorganism is held on the surface of a fluid carrier in an upward flow type reaction tank. In the anaerobic reaction tank (methane fermentation tank), biogas (methane gas) generated by the anaerobic reaction rises in the anaerobic reaction tank, and is discharged and recovered from the upper part of the anaerobic reaction tank. At this time, the carrier holding the microorganisms may rise together and flow out of the anaerobic reaction tank as an overflow. In the apparatus for carrying out the present invention, a screen for separating the treated water and the carrier is installed at the overflow port in order to prevent the carrier from overflowing from the anaerobic reaction tank (methane fermentation tank) (see FIG. 2). Alternatively, an overflow water storage unit is attached outside the anaerobic reaction tank, the overflow water containing the carrier is temporarily stored, a screen is provided at the outflow part from the overflow water storage unit, and the carrier and the treated water are separated. It is good also as a structure which returns only to an anaerobic reaction tank (FIG. 3). The biogas recovered from the anaerobic reaction tank (methane fermentation tank) can be used in a boiler or the like after gas purification such as desulfurization as necessary.

  The methane fermenter used in the present invention comprises a carrier introduction tube for introducing a carrier during a startup operation period, and a valve for controlling the introduction of the carrier from the carrier introduction tube to the upward flow anaerobic reaction vessel. It is characterized by comprising. As needed, you may provide an acid fermenter in the front | former stage of a methane fermenter.

  The present invention is characterized by controlling the start-up operation of an anaerobic reaction tank (methane fermentation tank). Usually, in the anaerobic treatment of organic wastewater, it is necessary to perform anaerobic microorganism habituation operation until the design load of the anaerobic reaction tank is reached. Since stable adhesion and propagation of microorganisms on the carrier take a long time, the startup operation time may exceed 90 days. In the present invention, granule sludge is used as seed sludge for adhering microorganisms to the carrier, and the amount of carrier charged and the amount of the carrier charged so that there is always granule sludge or a carrier to which microorganisms adhere around the carrier. To control.

The organic wastewater treatment method of the present invention is an anaerobic treatment method in which organic wastewater is passed through an anaerobic reaction tank holding a carrier capable of supporting anaerobic microorganisms, and is treated as seed sludge. At the beginning of the flow of organic waste water using the sludge, the bulk capacity of the seed sludge is 6 or more and 50 or less with respect to the bulk capacity 1 of the carrier, and the COD _Cr design load of the anaerobic reaction tank The carrier is additionally charged at least once until the S-COD _Cr (soluble COD _Cr ) removal rate reaches 90%.

  The anaerobic reaction in the present invention is an anaerobic treatment in all temperature ranges, such as a medium temperature methane fermentation treatment with an optimum temperature of 30 ° C to 40 ° C and a high temperature methane fermentation treatment with an optimum temperature of 50 ° C to 60 ° C. Can be used without limitation.

[Seed sludge]
As the seed sludge to be introduced in the present invention, granule sludge in which sludge containing anaerobic microorganisms is granulated by the self-granulating action of microorganisms to form sedimentary granules can be preferably used. Granule sludge is formed as a sludge layer in UASB (upflow anaerobic sludge bed method) or EGSB (expanded sludge bed method). Normal granular sludge has a structure in which filamentous or rod-shaped Methanosaeta methanogens are intertwined (FIG. 4). In the UASB method and the EGSB method, the granular sludge is used as a fluidized bed without holding the granular sludge on the carrier. In the present invention, granule sludge formed by the UASB method or EGSB method is used as seed sludge, held on a carrier, and microorganisms are propagated on the surface of the carrier. The granular sludge that can be used in the present invention preferably has a particle size of 0.5 mm to 4.0 mm, particularly 0.5 mm to 2.0 mm. If the particle size is 0.5 mm or less, it will be easy to flow out, and if it is 4.0 mm or more, it will be easy to float up with air bubbles inside. However, it is not necessary for all the granular sludge to have a particle size within the above range, and 80% or more, preferably 90% or more of the sludge amount may be within the above range.

The additional addition of granule sludge may be pumped to the inflow water inlet provided in the lower part of the methane fermentation tank shown in FIG. 1 or FIG. 3, or may be introduced from the upper part of the methane fermentation tank.
[Carrier]
The carrier can be used without particular limitation as long as it can carry microorganisms and can propagate microorganisms on the surface of the carrier.

  The shape of the carrier may be any shape such as spherical, cylindrical, rectangular parallelepiped, hollow, etc., but the amount of microorganisms supported, the contact efficiency between the propagated microorganisms and organic waste water, the amount of carriers retained in the anaerobic reaction tank In consideration of the above, a spherical shape is particularly preferable (FIG. 5).

  The size of the carrier is preferably 0.1 mm or more and 10 mm or less in average value (median diameter d50 in the case of spherical particles, and arithmetic average value of the maximum size and the minimum size in the case of other shapes), particularly 2 mm or more. 6 mm or less is preferable.

  The carrier is preferably a porous carrier having pores to which microorganisms easily adhere, and the pore diameter is preferably 1 μm or more and 100 μm or less, and particularly preferably 5 μm or more and 50 μm or less.

  Further, in order to develop the fluidized bed in an anaerobic reaction tank by upward flow, the upward linear velocity (LV) is increased to 1 m / h with upward flow of fresh water in a cylindrical column having a diameter of 80 mm filled with unused carrier. When the water is passed at a flow rate of 20 m / h or less, the expansion rate (the carrier height at the time of flow relative to the carrier height at the time of charging) is 105% or more and 150% or less, particularly LV2 m / h or more and 15 m / h or less. A carrier having an expansion coefficient of 110% to 130% is preferable.

  The material of the carrier may be any material as long as anaerobic microorganisms adhere to it, and activated carbon, polyvinyl alcohol, ethylene glycol, and the like are particularly preferable because the above-described requirements are satisfied.

[Operating conditions of anaerobic reaction tank (methane fermentation tank)]
The LV of the anaerobic reaction tank (methane fermentation tank) is preferably 1 m / h or more and 20 m / h or less, particularly preferably 2 m / h or more and 10 m / h or less. In order to adjust the inside of the anaerobic reaction tank (methane fermentation tank) to a predetermined LV, a part of the anaerobic reaction (methane fermentation) treated water is provided at the lower part of the anaerobic reaction tank (methane fermentation tank). It can be circulated to the water inlet. The treated water to be circulated may be treated water containing no carrier after passing the treated water accompanied by the carrier flowing out from the anaerobic reaction tank (methane fermentation tank) through the screen and separating the carrier, or treatment containing the carrier. Water can be used. When the treated water containing the carrier is circulated, it is preferable to use a snake pump or a gas lift that does not destroy the carrier. When the carrier is separated, it is preferable to return the carrier to the anaerobic reaction tank (methane fermentation tank) (FIG. 3).

The design load (COD _Cr volumetric load) of the anaerobic reaction tank (methane fermentation tank) depends on the raw aqueous state, but can be in the range of 5 to 50 kg / (m ³ · d). Granule sludge floats with air bubbles inside, and granule sludge may be dismantled due to excessive gas mixing, so high load treatment is difficult.In the present invention, granular sludge is used as seed sludge. As a result, it is possible to carry a higher load treatment by carrying it on a carrier.

  In general, granule sludge contains not only methanogens but also acid producers, and has high activity near the surface, but low activity in the center (FIG. 4). On the other hand, in the present invention, when granule sludge is carried as a seed sludge on a carrier and propagated, highly active methanogens propagate on the surface of the carrier (FIG. 5). The methanogenic activity of general granular sludge is 0.4 to 0.8 kg / (kg-MLVSS · d). The methanogenic activity of the microorganisms supported on the carrier used in the present invention is 1. It is as high as 0 to 2.0 kg / (kg-MLVSS · d).

[Organic wastewater]
The organic wastewater COD _Cr that can be treated by the organic wastewater treatment method of the present invention is not particularly limited, and the organic substance concentration in the range of 100 mg / L to 50,000 mg / L is low to high. Can be applied to waste water. In the case of organic wastewater having a high organic matter concentration, it is preferable to dilute appropriately in order to mitigate the inhibition of raw water components.

  The organic wastewater treatment method of the present invention is particularly useful for the treatment of organic wastewater having a composition that cannot maintain granular sludge. For example, organic sludge containing low-molecular-weight organic substances with 5 or less carbon atoms such as ethanol, methanol, and acetic acid that cannot maintain the granular sludge because the strength of the granular sludge is reduced, and pipe cleaning agents that dismantle the granular sludge It is effective for the treatment of organic wastewater from beverage factories, etc. containing chelating agents and bactericides.

Although the organic waste water shows the processing flow which flows into an methane fermentation tank after performing an acid fermentation process in an acid fermentation tank, an acid fermentation process is not essential. In the case of organic wastewater in which acid fermentation has already progressed sufficiently, or organic wastewater that can be treated only with a methane fermentation tank without performing acid fermentation treatment, it is not necessary to use an acid fermentation tank. Specifically, for example, organic waste water in which the total of COD _Cr conversion values of organic acids having 5 or less carbon atoms with respect to organic waste water COD _Cr accounts for 40% or more, or low molecular organic substances having 1 carbon atom such as methanol and formaldehyde. In the case of organic waste water that occupies 70% or more of the organic waste water COD _Cr , acid fermentation treatment is unnecessary. When acid fermentation treatment is performed, the pH is adjusted with an alkaline agent so that the acid fermentation tank has a pH suitable for acid-producing bacteria of 5.5 or higher. By circulating the methane fermentation treated water to the acid fermenter, the amount of alkali agent added can be reduced by the alkali components contained in the methane fermentation treated water. The residence time of the acid fermenter can be appropriately determined in the range of 2 hours to 48 hours depending on the components contained in the organic waste water, but when it contains a saccharide component that is easily decomposed, it is 2 hours to 6 hours. And often.

EXAMPLES Hereinafter, although this invention is demonstrated further more concretely using an Example and a comparative example, this invention is not limited by these Examples.
In Comparative Examples and Examples, organic waste water (raw water), which is a soft drink factory effluent with COD _Cr adjusted to about 3,000 mg / L, is alkaline so that the residence time is 6 hours, the water temperature is 36 ° C., and the pH is 6.5. After adding sodium hydroxide as an agent and performing an acid fermentation treatment, an anaerobic treatment was performed using an upflow anaerobic reaction tank (methane fermentation tank) having a capacity of 10 L. A 2.0 mm wide screen was provided at the treated water outflow part in the upper part of the methane fermentation tank so that the carrier did not flow out of the methane fermentation tank. A part of the methane fermentation treated water was circulated in the inflow part at the bottom of the methane fermentation tank, and the LV of the methane fermentation tank was adjusted to 5.0 m / h.

  In an anaerobic reaction tank (methane fermentation tank), gel particles of polyvinyl alcohol having an average particle diameter of 4.0 mm and an LV of 10 m / h in an unused fresh water test of 115% were used as a carrier. As the seed sludge, granular sludge collected from UASB whose diameter 0.5 mm to 2.0 mm accounts for 92% of the whole was used.

The design load of the methane fermenter was 20 kg / (m ³ · d).
In the evaluation of the treatment performance, 1 μm filtrate soluble COD _Cr (S-COD _Cr ) was employed in order to eliminate the influence of the spilled sludge.

[Comparative Example 1]
The granular sludge 4.0L and the support | carrier 4.0L were injected | thrown-in to the methane fermentation tank at once, and the water supply of acid fermentation treated water was started. In this case, the ratio (Rgc) of the bulk capacity of the seed sludge to the bulk capacity of the carrier at the start of the flow of the organic waste water is 1.0.

Set load of COD _Cr volumetric load is 5 kg / (m ³ · d), 7.5 kg / (m ³ · d), 10 kg / (m ³ · d), 15 kg / (m ³ · d) and 20 kg / (m ^The operation was started up in 5 stages (3.d) and the operation period of each stage was 7 days. The S-COD _Cr removal rate on the last day of each set load was determined. The results are shown in Table 1.

When the COD _Cr volumetric load (set value) was 10 kg / (m ³ · d) or more, granulated sludge flowed out of the methane fermentation tank and the S-COD _Cr removal rate decreased. On the 21st and 28th days after the start of operation, 2.0 L of granule sludge was added each time, but it flowed out in about 3 days after the start, and the granule was measured when measured on the 35th day after the start of operation. The residual rate of sludge was 0%, and no improvement in the S-COD _Cr removal rate was observed. When the operation was continued as it was, the S-COD _Cr removal rate stabilized at about 90% after the 57th day. As a result, the startup operation period was 57 days.

[Comparative Example 2]
Although 4.0 L of the carrier was put into the methane fermenter, the raw water without acid fermentation was started in a state where the seed sludge was not put. After passing the raw water for 10 days, 4.0 L of granule sludge was added. In this case, the ratio (Rgc) of the bulk capacity of the seed sludge to the bulk capacity of the carrier at the start of the flow of the organic waste water is zero.

Set load of COD _Cr volumetric load is 5 kg / (m ³ · d), 7.5 kg / (m ³ · d), 10 kg / (m ³ · d), 15 kg / (m ³ · d), 20 kg / (m ^The stage was raised step by step on the 5th floor of ³ · d), and the start-up operation was performed with the operation period of each stage being 4 days. The S-COD _Cr removal rate on the last day of each set load was determined. The results are shown in Table 2.

The granule sludge in the methane fermenter sharply decreased after the 15th day from the start of operation, and the S-COD _Cr removal rate decreased to about 52% on the 26th day after the start of operation. When the operation was continued as it was, the S-COD _Cr removal rate stabilized at about 90% after the 62nd day. As a result, the startup operation period was 62 days.

[Example 1]
6.0 L of granule sludge and 1.0 L of support | carrier were injected | thrown-in to the methane fermentation tank, and the water supply of acid fermentation treated water was started. In this case, the ratio (Rgc) of the bulk capacity of the seed sludge to the bulk capacity of the carrier at the start of the flow of the organic waste water is 6.0.

Set load of COD _Cr volumetric load is 5 kg / (m ³ · d), 7.5 kg / (m ³ · d), 10 kg / (m ³ · d), 15 kg / (m ³ · d) and 20 kg / (m ^The operation was started up in 5 stages (3.d) and the operation period of each stage was 5 days. On the 5th and 10th days after the start of operation, 1.0 L and 2.0 L of carrier were additionally charged, respectively. The S-COD _Cr removal rate on the last day of each set load was determined. The results are shown in Table 3.

On the 21st day after the start of operation, the S-COD _Cr removal rate decreased to about 80%, but after about 28th day after the start of operation, it was stable at about 90%. As a result, the startup operation period was 28 days.

[Example 2]
4.0 L of granule sludge and 0.4 L of support | carrier were injected | thrown-in to the methane fermentation tank, and water flow of acid fermentation treated water was started. In this case, the ratio (Rgc) of the bulk capacity of the seed sludge to the bulk capacity of the carrier at the start of the flow of the organic waste water is 10.0.

Set load of COD _Cr volumetric load is 5 kg / (m ³ · d), 7.5 kg / (m ³ · d), 10 kg / (m ³ · d), 15 kg / (m ³ · d) and 20 kg / (m ^The operation was started up in 5 stages (3.d) and the operation period of each stage was 5 days. On the fifth, tenth and fifteenth days after the start of operation, 0.6 L, 1.0 L and 2.0 L of carrier were additionally charged, respectively. The S-COD _Cr removal rate on the last day of each set load was determined. The results are shown in Table 4.

Although the S-COD _Cr removal rate temporarily decreased to about 70% on the 21st day after the start of operation, it was stable at about 90% after the 32nd day after the start of operation. As a result, the startup operation period was 32 days.

FIG. 6 shows changes over time in the COD _Cr volume load (upper stage) and S-COD _Cr removal rate (lower stage) of Comparative Example 1, and FIG. 7 shows the COD _Cr volume load (upper stage) and S of Comparative Example 2. -COD _Cr removal rate (lower stage) shows daily changes, FIG. 8 shows COD _Cr volumetric load (upper stage) and S-COD _Cr removal rate (lower stage) daily changes of Example 1, and FIG. These show the daily change of COD _Cr volume load (upper stage) and S-COD _Cr removal rate (lower stage) of Example 2.

  The results of Comparative Examples 1-2 and Examples 1-2 are summarized in Table 5.

Claims (3)

An anaerobic treatment method in which organic waste water is passed through an anaerobic reaction tank holding a carrier capable of supporting anaerobic microorganisms,
Granule sludge is used as seed sludge,
At the start of passing organic wastewater, the bulk capacity of the seed sludge is set to a ratio of 6 to 50 with respect to the bulk capacity 1 of the carrier,
An anaerobic treatment method for organic wastewater, wherein the carrier is additionally charged at least once before the S-COD _Cr removal rate reaches 90% in the COD _Cr design load of the anaerobic reaction tank. An upflow anaerobic reactor holding a carrier capable of supporting anaerobic microorganisms;
A carrier introduction pipe for introducing the carrier during the startup operation period of the upward flow anaerobic reaction tank;
A valve for controlling the introduction of the carrier from the carrier introduction pipe into the upward flow anaerobic reaction tank;
An anaerobic treatment apparatus for organic wastewater, comprising: An acid fermentation tank provided upstream of the upward flow anaerobic reaction tank;
Acid fermentation treated water introduction pipe for sending acid fermentation treated water from the acid fermentation tank to the upward flow anaerobic reaction tank;
The anaerobic treatment apparatus for organic wastewater according to claim 2, further comprising: