KR20030033645A - Wastewater treatment with biological porous media - Google Patents

Abstract

PURPOSE: A wastewater treatment equipment using double layer biofilm media is provided, in which aerobic and anoxic conditions are formed respectively at the outer and inner sides of the media, so that nitrification and denitrification are carried out simultaneously. By using this media, nitrification rate is steadily kept at almost 80 % according to ammonia nitrogen load, and in case of high inlet load of ammonia nitrogen and high free ammonia, nitrous ammonia is accumulated thus inducing direct denitrification to raise utilizing rate of organic carbon for denitrification. CONSTITUTION: In the denitrification and nitrification treatment equipment of wastewater conducted in the same reactor, the equipment is characterized in that it comprises perforated tubular media(1) of fixed thickness installed in the reactor, wherein on the outer surface thereof nitrification microorganism is adhered and in the tube denitrification microorganism is adhered owing to mass transfer resistance of air, with the pores formed on the tube being radially penetrated from inside to outside; strainers installed at the top and bottom of the reactor for the prevention of any outflow of the media(1), wherein inflow is fed from bottom to flow upward and air is sparged just beneath the strainers.

Description

Wastewater treatment apparatus using double layer biofilm carrier {Wastewater treatment with biological porous media}

The present invention relates to a wastewater treatment apparatus using a double-layer biofilm carrier, and more particularly, to a wastewater treatment apparatus capable of performing nitrification and denitrification simultaneously in the same reactor by improving the double-layer biofilm carrier.

The biological nitrogen removal process of wastewater consists of nitrification by autotrophic microorganisms in aerobic state and denitrification by heterotrophic microorganisms using nitrogen oxide as electron acceptor with the help of electron donor in anoxic state. Therefore, in the conventional nitrogen removal process, the nitrification zone and the denitrification zone are separated, so that the size or process of the treatment facility is larger and more complicated than the conventional organic removal process, and the amount of oxygen (4.6 g O ₂ / g NH ₄ ⁺ -N) and denitrification required an organic carbon source of about 1.9 g / g NO ₃ ^-- N based on methanol. In particular, the activated sludge method currently used in biological wastewater treatment process is mostly developed for the purpose of removing floating substances or organic substances, so the removal efficiency of nitrogen components is low and requires high maintenance technology and large land area. There are many disadvantages of excess sludge. In addition, since the nitrified wastewater has to be conveyed to the denitrification tank, there is a problem that a conveying pump is required and a lot of power costs are required.

However, recently, as an alternative process to compensate for such drawbacks, a method of satisfying the appropriate conditions for nitrification and denitrification in one bioreactor has been attracting attention. That is, the ammonia nitrogen is nitrified by the nitrifying microorganism under the condition that the proper dissolved oxygen concentration is maintained. In addition, denitrification may be caused by denitrifying microorganisms when the dissolved oxygen concentration is sufficiently low in the state where the (a) nitrate ion and the electron donor are properly maintained. Such a conventional wastewater treatment apparatus is shown in FIG.

Figure 1 shows a schematic diagram of a conventional biofilm reactor divided into aerobic zone and anoxic zone.

Influent water including ammonia nitrogen and an organic carbon source is introduced into the lower portion of the biofilm reactor 20 through the raw water inlet pump 12. Air is introduced into the central portion of the biofilm reactor through the blower 17, the amount of air flowing through the air control valve 16 is adjusted. The carrier is separated into a nitrification zone and a denitrification zone by the central strainer 25. Since the strainers 25 'and 25 "are provided at the inlet and outlet portions of the reactor, the carrier is not discharged. An anoxic zone 18 is formed at the bottom of the biofilm reactor 20 and an aerobic zone 19 is formed at the top of the biofilm reactor 20, whereby denitrifying and nitrifying microorganisms can grow as dominant species, respectively. Nitrified at the upper end, which is an aerobic zone, and flows out of the reactor through the treated water outlet 22, and a portion of the treated water is returned to the lower end of the biofilm reactor by the treated water conveying pump 24 along the conveying line 23. At this time, the (ni) nitrate nitrogen contained in the return water is an electron acceptor, and the organic carbon source included in the influent water is used as an electron donor, which causes denitrification by denitrification microorganisms. In this reactor, the rate of nitrification and the rate of return of the treated water have a great influence on the removal efficiency of total nitrogen, and ammonia nitrogen is almost oxidized in the form of nitrate nitrogen. 13 represents a sludge discharge valve, 14 represents a sludge discharge port, 15, 15 'and 15 "sample sampling valves, and 21 represents an air discharge port.

In the conventional reactor system in which nitrification and denitrification are separated, since ammonia nitrogen is mostly converted to nitrate nitrogen through nitrite nitrogen in the nitrification step and then transferred to the denitrification reactor, many electron donors are required for denitrification. do. Equation 1 is a stoichiometric expression of the amount of acetate (acetate) required for the denitrification of nitrate nitrogen and nitrite nitrogen.

^{_{8 NO 3 - + 5 CH 3}} COOH ---> 4 N 2 + 10 CO 2 + 6 H 2 O + 8 OH - (C / N = 1.07)

^{_{8 NO 2 - + 3 CH 3}} COOH ---> 4 N 2 + 6 CO 2 + 2 H 2 O + 8 OH - (C / N = 0.64)

When denitrified from nitrite nitrogen as shown in Equation 1 above, it can be seen that the electron donor can be reduced by about 40% compared to the nitrate nitrogen.

However, in order to completely remove the nitrogen component, aerobic nitrification and anoxic denitrification must be combined. In practice, however, since the two reactions occur under different environmental conditions, it is difficult to run both reactions simultaneously in one reactor. One possibility is a method of jointly immobilizing nitrifying microorganisms on the outside of the carrier and denitrifying microorganisms on the inner layer of the carrier. At this time, the nitrifying microorganism causes the inside of the oxygen-free state to proliferate mainly on the surface of the carrier because of resistance to oxygen substance transfer into the carrier. Denitrification microorganisms denitrify (nitrous) ions oxidized by nitrifying microorganisms in an oxygen-free carrier using an appropriate organic carbon source. That is, the product of the first microorganism becomes the substrate of the second microorganism, and the two-step bioconversion process proceeds as if it were a one-step process.

However, two microorganisms must be physically separated to constitute such a nitrification / denitrification system. If the two microorganisms are simply mixed and immobilized, denitrifying microorganisms that grow faster than nitrifying microorganisms predominantly exist in the presence of organic matter. But in order to solve this problem alginate (alginate) and Kara past research to produce a double-layer carrier immobilized microbial nitrification and denitrification microorganisms separately (K- carrageenan) progresses, these systems also poses many problems. First, microbial immobilization of bilayers is not suitable for mass production and expensive. Second, carriers such as alginate and carrageenan suitable for making such bilayers are not suitable for long-term operation in wastewater treatment plants due to their poor mechanical strength and chemical stability. . Third, the nitrogen gas produced by denitrification inside the carrier has difficulty in diffusing out of the carrier. In this case, the nitrogen bubbles inside the carrier lower the material transfer rate, and the bubbles are released in the pressurized state, causing cracking of the carrier or having different specific gravity of the carrier, thereby causing different carrier flow characteristics.

Accordingly, the present invention is to solve the problems of the prior art as described above, the object of the present invention is to improve the problems of the conventional double-layer biofilm carriers to treat the wastewater to perform nitrification and denitrification at the same time in the same reactor To provide a device.

1 is a schematic configuration diagram of a conventional biofilm reactor in which nitrification and denitrification reactions are separated.

Figure 2a to 2d is a view showing the structure of a bilayer biofilm carrier in accordance with the present invention.

Figure 3 shows the concentration of each substance in the microbial layer and nitrification denitrification attached to the bilayer biofilm carrier.

Figure 4 is a schematic diagram of a biofilm reactor for performing simultaneous nitrification and denitrification according to the present invention.

* Explanation of symbols for the main parts of the drawings

1: Bilayer Biofilm Carrier 11: Influent Storage Tank

12: raw water inlet pump 13: sludge discharge valve

14: Sludge outlet 15, 15 ', 15 ": sampling valve

16: air control valve 17: blower

21: air outlet 22: treated water outlet

25: strainer

In order to achieve the above object, the present invention provides a wastewater treatment apparatus for performing denitrification and nitrification of wastewater in the same reactor, which is installed inside the reactor, a plurality of voids are formed, and a hole is formed in the center thereof. In the form of a tube having a predetermined thickness, nitric oxide microorganisms are attached to the outside of the tube due to the transfer resistance of air, denitrifying microorganisms are attached to the inside of the tube, and the pores are perpendicular to the outside of the tube from the inside of the tube. A carrier formed through; And it characterized in that it comprises a strainer respectively installed on the top and bottom of the reaction tank to prevent the outflow of the carrier.

The features of the present invention can be broadly divided as follows.

First, in a device for removing nitrogen from wastewater, a carrier in the form of a porous tube (tube) is used, but nitrifying microorganisms are attached to the outside of the carrier, and denitrifying microorganisms are formed inside the carrier to form a double layer, and the wastewater in one reactor Nitrification of ammoniacal nitrogen at the same time and denitrification using organic matter contained in the waste water.

Second, both ends of the porous tube are open to one side or both sides, and the carrier having a porous tube (tube) form physically separates nitrifying microorganisms and denitrifying microorganisms due to air transfer resistance. In addition, the carrier material is a porous or hollow fiber of organic polymer material or inorganic material such as polyolefin composed of polyethylene, polypropylene, or a mixture thereof, and the ratio of diameter to length of the carrier is 1: 1 to 1: It has the form of 10 ranges. In order to increase the fluidity of the carrier, calcium carbonate or talc is added to adjust the apparent specific gravity to 1.1 to 1.8 g / cm 3.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figures 2a to 2d is a view showing the structure of a bilayer biofilm carrier according to the present invention.

The bilayer biofilm carrier 1 has a tubular shape as shown in FIG. 2A, and has a hole 2 leading into the carrier to form anoxic conditions in which denitrified microorganisms can inhabit. In addition, many voids 3 are formed on the surface of the double-layer biofilm carrier 1. The voids 3 formed on the surface are formed so as to vertically penetrate from the inner wall of the hole 2 to the outside of the tube as shown in Fig. 2B. These pores play a very important role in the mass transfer of oxidized nitrous nitrogen and organic material in the bilayer biofilm carrier, and thus it can be said that the nitrite nitrogen produced during nitrification can be denitrified. On the other hand, the biofilm carrier 1 according to the present invention can be manufactured in a form in which both ends are open as shown in Figure 2c. On the other hand, as shown in FIG. 2D, the tubular bilayer biofilm carrier may be manufactured in a sealed form at either end. In the case of the tubular carrier which is open on both sides, the movement of the material is smoother than that of the tubular carrier which is closed on one side, but conversely, the space for forming anoxic conditions inside the bilayer biofilm carrier may be reduced.

The material of the carrier is made of an organic polymer or inorganic material such as polyethylene, polypropylene, or a polyolefin composed of a mixture thereof. The carrier may be made of a porous tube or hollow fiber. In addition, the ratio of the diameter to the length of the carrier is in the range of 1: 1 to 1:10. In order to increase the fluidity of the carrier, calcium carbonate or talc is added to the material of the carrier to adjust the apparent specific gravity to 1.1 to 1.8 g / cm 3.

Figure 3 is a view showing the concentration change of each material in the microbial layer and nitrification denitrification process attached to the bilayer biofilm carrier.

The bilayer biofilm carrier according to the present invention is characterized in that nitrifying and denitrifying microorganisms naturally adhere to the carrier through continuous operation without artificially immobilizing the microorganisms. As shown in the figure, the nitrifying microorganism 5 is mainly attached to the outer wall of the double layer biofilm carrier 1, which is an aerobic region, and the denitrifying microorganism 4 is attached inside the carrier lacking dissolved oxygen. The ammonia nitrogen (8) introduced together with the wastewater (6) reacts with oxygen by the nitrifying microorganisms attached to the outer wall of the double-layer biofilm carrier, and is converted into (nitrous) nitrate ion (10). (N) The nitrate ions and the organic substance 7 diffuse through the micropores and both ends of the carrier, and are denitrated by the denitrifying microorganisms inside the carrier. At this time, the dissolved oxygen (9) is consumed by the nitrifying microorganisms, deficient in the carrier by the transfer resistance and becomes anoxic conditions.

4 is a schematic diagram of a biofilm reactor for performing simultaneous nitrification / denitrification according to the present invention.

Strainers 25 are installed at the top and bottom of the biofilm reactor, respectively, to prevent the outflow of the fluidized bed carrier, and the inflow water is introduced in an upward flow through the raw water inflow pump 12. The treated water is discharged through the treated water outlet 22 at the top of the biofilm reactor. In addition, the reactor does not require separate conveyance for denitrification. Air is supplied to the lowest end of the biofilm reactor 20 through the blower 17, and the flow rate of the air supplied through the air control valve 16 is adjusted. In addition, the present double-layer biofilm carrier 1 can be effectively mixed with the wastewater and the carrier to stabilize the treatment efficiency without having to install its own stirrer or flow device to supply air. In the drawing, 11 is an influent storage tank, 13 is a sludge discharge valve, and 15, 15 ', and 15 "are sampling valves, respectively.

In order to verify the applicability of simultaneous nitrification denitrification and the efficiency of nitrification and denitrification of wastewater according to the ratio of C / N in a fluidized bed bioreactor using a polyethylene hollow fiber carrier, an acrylic round tube About 40% of the reactor inside the reactor was filled with a carrier, and a laboratory scale biofilm device designed to be flowed by air was designed and manufactured.

The bilayer biofilm carrier used was a hollow fiber piece containing micropores of polystyrene material having a length of 3 mm and an outer diameter of 1.1 mm. The polystyrene hollow yarn used in the present invention uses a hole having a diameter of about 0.8 mm at both ends to allow microorganisms to move and inhabit the inside as well as the outer surface. In addition, materials necessary for the growth and reaction of microorganisms may be delivered through holes at both ends. In addition, since the polystyrene hollow fiber material has a porosity of about 60%, the material can be moved through the wall of the hollow yarn.

The microbial sludge used in the experiment was inoculated with activated sludge from the sewage treatment plant. Wastewater contains organic carbon and nitrogen sources. Table 1 shows the operating conditions of the fluidized bed biofilm reactor during the experiment.

Example One 2 3 4 Driving period (days) 0-56 57-84 85-116 117-143 NH ₄ ⁺ -N concentration (mg / l) 100 100 200 50 Acetate concentration (mg C / l) - 100 100 50 Inflow NH ₄ ⁺ -N load ^{(kg N / m 3 · d} ) 1.4-2.0 (1.8 average) 1.9-2.4 (2.1 average) 3.7-4.7 (Average 4.2) 1.0-1.2 (1.1 average) Hydraulic dwell time (h) 1.3-1.7 1.0-1.3 1.0-1.2 0.9-1.2 Air supply rate ^{(m 3 / m 2 · min} ) 0.3 0.3-0.6 0.3-0.6 0.3-0.6

At this time, the water quality and treatment efficiency discharged from the treatment apparatus are shown in Table 2.

Example One 2 3 4 Influent NH ₄ ⁺ -N (mg N / L) 100 100 200 50 COD (mg / L) 0 100 100 50 Runoff NH ₄ ⁺ -N (mg N / L) 18 16 65 9 COD (mg / L) 0 0 0 0 NO ₂ ^-- N (mg N / L) 35 5 6 4 NO ₃ ^-- N (mg N / L) 44 12 4.6 8 Processing efficiency Average nitrification rate (%) 82 84 68 82 Average total nitrogen removal rate (%) 3 67 62 58 Effluent (%) 44 29 57 33

Here, the effluent is NO ₂ -N / NO ₂ -N + NO ₃ -N.

Nitrous nitrogen is rarely found in the nitrification system of general biological wastewater treatment. Accumulation of nitrite nitrogen has several causes, mainly due to the inhibition of nitrite oxidizer activity by dissociating ammonia (NH ₃ ) or dissolved oxygen deficiency.

In the present invention, the air supply rate is 0.3-0.6 m ³ / m ² · min to maintain a low dissolved oxygen concentration of 1-2 mg / L, the nitrite oxidizing bacteria by the oxygen transfer resistance to the inside of the hollow fiber Due to their inefficient use, some nitrite nitrogen appears to have accumulated and not oxidized to nitrate nitrogen.

As shown in Table 2, the bilayer biofilm process used in the present invention shows very high nitrification rate and total nitrogen removal rate when compared to the general wastewater treatment with organic and ammonia nitrogen. Excellent performance for nitrification and denitrification.

In particular, the amount of organic matter consumed in the operation period of Example 3 of Table 1 is the same as the amount of organic matter consumed in the operation period of Example 2, but the demassage is about twice the level. If 62% of the nitrogen introduced was denitrated from nitrate nitrogen, the amount of organic matter would be about 1.3 times that of the currently introduced carbon. That is, since many denitrifications are not immediately converted from nitrite nitrogen to nitrate nitrogen, organic consumption is considered to be reduced. This can also be confirmed that the nitrite nitrogen concentration in the reactor is higher than the nitrate nitrogen compared to the other experimental period.

As a result of the above experiment, air transmission efficiency and organic material consumption reduction effect of each period are shown in Table 3. The air transfer efficiency was expressed as the amount of ammonia nitrogen removed and the total nitrogen removed in the section supplied with the same amount of air. In addition, the amount of organic matter used was compared with the amount of organic matter used corresponding to the total amount of nitrogen removed assuming that all ammonia nitrogen was converted to nitrate nitrogen.

Example One 2 3 4 Removed ^{_{NH 4 + -N (kg N /}} m 3 · d) 1.48 1.76 2.84 0.89 % Utilization of air used to remove NH ₄ ⁺ -N 54 64 100 33 Total nitrogen removed (kg N / m ³ · d) 0.05 1.4 2.6 0.64 % Utilization of air used to remove total nitrogen 2 54 100 25 Organic matter used (kg C / m ³ · d) 0 2.1 2.1 1.1 Theoretical organic matter required for total nitrogen removed (kg C / m ³ · d) 0.054 1.5 2.78 0.68 Organic utilization rate (%) - 71 132 62

* Theoretical organic matter required for total nitrogen removed (kg C / m ³ · d) = total nitrogen removed (kg N / m ³ · d) × 1.07 (C / N required for denitrification)

Next, to test the effect of the pore of the polystyrene hollow fiber carrier used in the experiment as described above on the nitrogen removal rate and the total nitrogen removal rate depending on whether one side is opened or closed, as shown in FIGS. 2C and 2D, Experiments under the same nitrogen loading conditions.

Experimental conditions correspond to Example 3 of Table 1 and were tested for a total of 10 days. The experimental results are shown in Table 4.

Item Carriers with holes open on both sides Carrier with one hole open NH ₄ ⁺ -N removal rate (%) 67 65 Total Nitrogen Removal Rate (%) 62 61

As a result of the experiment, it was confirmed that the removal rate of nitrogen with respect to opening and closing of the hole inside the carrier showed little difference.

In order to verify the applicability of simultaneous nitrification / denitrification and the efficiency of nitrification and denitrification of wastewater according to the ratio of C / N in the fluidized bed biofilm reactor using polypropylene hollow fiber carrier . The bilayer biofilm carrier used had a hole having a length of 5 mm, an outer diameter of 1.1 mm and a diameter of about 0.8 mm at both ends, and had a porosity of about 50%.

All experimental conditions are the same as in Table 1, and the air supply rate was always maintained at 0.4 m ³ / m ² · min. Table 5 shows the operating conditions of the fluidized bed biofilm reactor during the experiment.

Example 5 6 7 8 Driving period (days) 0-30 31-67 68-93 94-123 NH ₄ ⁺ -N concentration (mg / l) 100 100 200 50 Acetate concentration (mg C / l) - 100 100 50 Inflow NH ₄ ⁺ -N load ^{(kg N / m 3 · d} ) 1.6-2.1 (1.9 average) 1.7-2.4 (2.1 average) 3.4-4.8 (4.0 average) 1.1-1.4 (1.2 average) Hydraulic dwell time (h) 1.1-1.5 1.0-1.4 1.0-1.4 0.9-1.1 Air supply rate ^{(m 3 / m 2 · min} ) 0.4 0.4 0.4 0.4

At this time, the water quality and treatment efficiency discharged from the treatment apparatus are shown in Table 6.

Example 5 6 7 8 Influent NH ₄ ⁺ -N (mg N / L) 100 100 200 50 acetate (mg C / L) 0 100 100 50 Runoff NH ₄ ⁺ -N (mg N / L) 14 18 54 6 acetate (mg C / L) 0 0 0 0 NO ₂ ^-- N (mg N / L) 31 6 7 4 NO ₃ ^-- N (mg N / L) 53 10 5 7 Processing efficiency Average nitrification rate (%) 86 82 73 88 Average total nitrogen removal rate (%) 2 66 67 66 Effluent (%) 37 38 58 36

Here, the effluent is NO ₂ -N / NO ₂ -N + NO ₃ -N.

Table 7 shows the air transfer efficiency and the organic matter saving effect according to the embodiment of the fluidized bed biofilm reactor using the polypropylene hollow fiber carrier.

Example 5 6 7 8 Removed ^{_{NH 4 + -N (kg N /}} m 3 · d) 1.63 1.72 2.92 1.06 % Utilization of air used to remove NH ₄ ⁺ -N 56 59 100 36 Total nitrogen removed (kg N / m ³ · d) 0.04 1.72 2.68 0.79 Utilization of air used to remove total nitrogen (%) One 64 100 29 Organic matter used (kg C / m ³ · d) 0 2.1 2.0 1.2 Theoretical organic matter required for total nitrogen removed (kg C / m ³ · d) 0.043 1.84 2.87 0.85 Organic utilization rate (%) - 88 144 71

* Theoretical organic matter required for total nitrogen removed (kg C / m ³ · d) = total nitrogen removed (kg N / m ³ · d) × 1.07 (C / N required for denitrification)

In the present invention, the air supply rate was kept constant at 0.4 m ³ / m ² · min, and the dissolved oxygen concentration was kept low around 2 mg / L. The polypropylene hollow fiber carrier used showed very high nitrification rate and total nitrogen removal rate as in polystyrene hollow fiber, and especially the accumulation of nitrite nitrogen and nitrite nitrogen in the section of Example 7 where the load of ammonia nitrogen was the highest Denitrification was confirmed to reduce the consumption of organic matter.

According to the present invention made as described above, the outside and inside of the bilayer biofilm carrier can maintain aerobic and anoxic conditions, respectively, it can be carried out nitrification and denitrification at the same time. In addition, when the carrier according to the present invention was used, the nitrification rate was stably maintained at almost 80% or more according to the ammonia nitrogen loading. In addition, when the load of ammonia nitrogen in the influent is high, the dissociation ammonia (free ammonia) or high dissolved oxygen concentration is denitrified as nitrite accumulates immediately there is an effect that the denitrification utilization efficiency of the organic carbon increases. Therefore, according to the present invention, in addition to the reduction in the scale of the reactor can be expected the advantage that the denitrification utilization efficiency of the organic carbon is increased.

Claims (10)

In the wastewater treatment apparatus for performing denitrification and nitrification of wastewater in the same reactor, It is installed inside the reactor, a plurality of voids are formed in the form of a tube having a hole in the center and a certain thickness, nitric oxide microorganism is attached to the outside of the tube due to the transfer resistance of air, A carrier to which denitrifying microorganisms are attached, and wherein the pores are vertically penetrated from the inside of the tube to the outside of the tube; And Wastewater treatment apparatus comprising a strainer respectively installed on the top and bottom of the reaction tank to prevent the outflow of the carrier. The method of claim 1, The waste water treatment apparatus, characterized in that the inflow water is introduced into the reaction tank in an upflow manner, the air is supplied from the lower portion of the strainer installed at the lower end of the reaction tank. The method of claim 1, Both ends of the carrier in the form of a tube, characterized in that the open wastewater treatment apparatus. The method of claim 1, Either one of the two ends of the tube-shaped carrier is closed, characterized in that the waste water treatment apparatus. The method according to claim 1 or 2, The waste water treatment apparatus, characterized in that the carrier is a porous tube made of an organic polymer material such as polyolefin composed of polyethylene, polypropylene or a mixture thereof. The method according to claim 1 or 2, The carrier is a wastewater treatment apparatus, characterized in that the hollow fiber made of an organic polymer material such as polyolefin consisting of polyethylene, polypropylene or a mixture thereof. The method according to claim 1 or 2, Waste water treatment apparatus, characterized in that the carrier is a porous tube made of an inorganic material. The method according to claim 1 or 2, Waste water treatment apparatus, characterized in that the carrier is a hollow fiber (hollow fiber) made of an inorganic material. The method according to claim 1 or 2, Waste water treatment apparatus, characterized in that the ratio of the diameter to the length of the carrier is 1: 1 to 1:10. The method of claim 5, In order to control the specific gravity for the air flow of the carrier, waste water treatment apparatus, characterized in that calcium deoxygen or talc is added as a material of the carrier.