JPH05154491A - Treatment of waste water containing high-concentration nitrogen - Google Patents

Abstract

PURPOSE:To biologically remove water pollutants (BOD) shown as biological oxygen demand, water pollutants (COD) shown as chemical oxygen demand and ammonia compound being reductive nitrogen compound from waste water containing high-concentration nitrogen. CONSTITUTION:Two-stage treatment is performed for waste water containing high-concentration nitrogen by both a fluidized bed type reactor 3 and a fixed bed type reactor 11 in which a microorganism immobilization carrier is used. Thereby organic substance and reductive nitrogen compound contained in waste water are simultaneously removed. Treatment efficiency and nitrogen removal performance are made excellent by the subject method.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to pollutants (BOD) and chemical oxygen demands expressed as biological oxygen demands contained in wastewaters such as municipal sewage, organic industrial wastewater, and sludge treated water. The present invention relates to a method for biologically removing displayed pollutants (COD) and ammonia compounds which are reducing nitrogen compounds.

[0002]

2. Description of the Related Art Conventionally, as a method for biologically removing BOD and ammonia compounds contained in municipal sewage at the same time, the Bardenpho method (J.
L. Barnard, Water Wastes En
gg. 33, 1974), or JP-A-54-24.
There are an A / O method and an A ₂ / O method described in Japanese Patent No. 774. Furthermore, as a variant of A ₂ / O method Sho 61-17558 JP, methods and the like are known incorporating a rotating disc for immobilizing microbial nitrification tank. In these methods, BOD is removed mainly by oxidative degradation of aerobic microorganisms, and ammonia compounds are oxidized by nitrifying bacteria to oxidize nitrate nitrogen.

Further, Japanese Patent Laid-Open No. 54-24774 discloses a reactor in which activated sludge is present in one anaerobic tank and one aerobic tank.
Tank, anaerobic 2 tanks, and aerobic 2 tanks are divided into 4 parts, and various aerobic and anaerobic levels are controlled using the redox potential (ORP) as an index, and blast furnace water granulation as a carrier for immobilizing activated sludge. A biological method for removing BOD, ammonia compounds and phosphorus compounds of wastewater by using slag, fine powder of carbon, etc. is described. Compared to the dissolved oxygen concentration (DO) and nitrogen compound concentration, which have been used as indicators until then, ORP is superior as a measure of aerobic and anaerobic levels, and nitrogen compounds can be efficiently removed.

In addition to this, in the treatment of sewage and organic wastewater,
In addition to the biological treatment process, if the concentration of biologically persistent organic substances and nitrogen compounds is high and it is considered to be difficult to remove by biological treatment, after biological treatment, chemical oxidation treatment is performed. The process of applying is applied. The main oxidizers used in chemical oxidation treatment are ozone, chlorine,
There is hydrogen peroxide. In particular, the method of using hydrogen peroxide and an iron salt such as ferrous sulfate together is called the Fenton method, and since the generated hydroxyl radical has a strong oxidizing power, it is difficult to biologically decompose organic compounds or nitrogen compounds. It is widely known as a method for treating industrial wastewater having a high concentration of water (for example, "Aikon Sesho", No. 17, 1989).

[0005]

Problems to be Solved by the Invention Conventional biological biological nitrogen removal processes such as municipal sewage represented by the A ₂ / O method and the like are compared because the concentration of ammonia compounds is about 20 to 50 mg / l. It is possible to biologically oxidize ammonia compounds to nitrate nitrogen (NO ₃ —N). However, it should be applied as it is to industrial wastewater containing BOD and COD at high concentrations and containing 50-100 mg / l or more of ammonia compounds, and municipal wastewater and sludge treated water into which a large amount of industrial wastewater is flowing. Is quite difficult. That is, when the wastewater contains a high concentration of organic substances and ammonia compounds, there is a strong tendency for nitrite (NO ₂ —N) type oxidation to proceed and accumulate in the reactor, and 1 mg of NO ₂ —N as COD Since it is measured as 0.14 mg, there is a concern that COD in the treated water will increase. Further, in order to prevent this nitrite type oxidation, controlling the organic matter load and the aerobic degree of the reactor are very important subjects, and it is quite difficult to prevent the nitrite type oxidation by the conventional method. The above is described in, for example, “Wat. Res.” 1990, Vol. 24, N
o. 3, pp. No. 303-312. That is, when an artificial wastewater containing 80 mg / l of an ammonia compound was treated in a fluidized bed reactor in which DO was maintained at 0.5 mg / l under the treatment time of 4 days, NO ₂ −
N was reported to have accumulated 60 mg / l, and nitrite-type oxidation was D
We conclude that even if O is low, it will progress. Furthermore, an experiment was conducted in which the COD of the inflow water was changed, and it was reported that the organic matter load affects the nitrite type oxidation. As described above, in the conventional biological nitrogen removal process, the treatment time becomes very long when treating high-concentration nitrogen-containing wastewater containing 50 to 100 mg / l or more of ammonia compounds, and the equipment cost is enormous. Becomes Further, the influence of the organic matter load on the nitrification reaction and the method of controlling the aerobic level have not been clarified.

Further, in order to efficiently oxidize reducing nitrogen compounds in municipal wastewater to NO ₃ -N, the reactor in which activated sludge is present is controlled using ORP as an index, and the activated sludge is immobilized. It is considered that the process using a fluidized bed reactor that uses granulated blast furnace slag, carbon fine powder, etc. as a carrier is efficient. This is because the nitrification reaction of ORP is easier to control than DO and the nitrifying bacteria can be maintained at a high concentration in the reactor because an immobilized carrier is used. By the single treatment process of this fluidized bed reactor, reducing nitrogen compounds in municipal wastewater can be efficiently and stably removed.
However, when the single treatment process of the fluidized bed reactor is also applied to the treatment of wastewater containing a high concentration of organic matter and ammonia compound, the organic matter of the wastewater inhibits the biological oxidation of the ammonia compound to NO ₃ -N. There are cases.

Further, there is a method of combining such a biological treatment method with a chemical oxidation treatment method such as Fenton oxidation method. 17, 1989, the Fenton oxidation method uses C in raw water.
It is recognized that it has an effect on OD removal and NO ₂ —N oxidation. However, in the case of wastewater treatment with a high concentration of reducing nitrogen compounds, the amount of reagents consumed for nitrite type oxidation increases,
Compared to a single biological treatment process, the combined biological treatment and chemical oxidation treatment process increases the running cost and is extremely uneconomical.

The present invention eliminates problems by improving the conventional treatment method for treating wastewater containing high concentration nitrogen as described above, and establishes a stable and efficient treatment method for wastewater containing high concentration nitrogen. The purpose is to do.

[0009]

The present invention provides a method for treating wastewater containing high-concentration nitrogen by performing two-stage treatment of a fluidized bed type reactor and a fixed bed type reactor using a microorganism-immobilized carrier. The method for treating high-concentration nitrogen-containing wastewater is characterized by simultaneously removing the organic matter and reducing nitrogen compound.

In the fluidized bed reactor, granulated blast furnace slag, silica sand, activated carbon, plastics, cristobalite, carbon fine powder, etc. are used as a carrier for immobilizing microorganisms, and the redox potential of the reactor is the oxidation of organic matter in wastewater. Aeration is performed by supplying air and / or oxygen-enriched air and / or oxygen so as to control the range of 0 to +100 mV (based on gold-silver / silver chloride electrode) suitable for decomposition.

Further, the fixed bed reactor includes a saddle-type ceramic, which is mainly made of granulated blast furnace slag, and silica.
Using alumina-based ceramics or the like as a carrier for immobilizing microorganisms, air and / or air is controlled so that the redox potential of the reactor is controlled to +100 mV or more (gold-silver / silver chloride electrode reference) suitable for oxidizing ammonia compounds in wastewater. Alternatively, aeration is performed by supplying oxygen-enriched air and / or oxygen.

[0012]

The fluidized bed reactor is intended to efficiently remove organic substances contained in wastewater. By using granulated blast furnace slag, silica sand, activated carbon, plastics, cristobalite, carbon fine powder, etc. as a carrier for immobilizing microorganisms, the sedimentation of microorganisms is improved and it becomes possible to maintain a high concentration in the reactor, Treatment time is 1/2 to 1/3 compared to the case where it is not used for immobilization carrier.
Can be shortened to. Among them, granulated blast furnace slag contains calcium as a main component, and the immobilization performance of microorganisms is superior to that of other immobilization carriers due to the effect of promoting aggregation of calcium, and it is most desirable as the immobilization carrier. Furthermore, the ORP of the fluidized bed reactor is 0 to +10.
By maintaining at 0 mV (gold-silver / silver chloride electrode standard), the oxidative decomposition of BOD in wastewater can be sufficiently promoted. When the BOD concentration in the wastewater is high, the ORP of the fluidized bed reactor is 0 to +100 m in air aeration.
It may be difficult to maintain V, and if too much air is used, the activated sludge will be destroyed or fragmented, and it will flow into the treated water without settling sufficiently in the sludge settling tank, causing deterioration of the treated water. There are cases. In such a case, it is desirable to supply oxygen-enriched air and / or oxygen to perform aeration.

The fixed bed reactor is a biologically efficient oxidation of nitrogen compounds contained in wastewater, mainly reducing nitrogen compounds such as Kjeldahl nitrogen compounds and ammoniacal compounds, to nitrate nitrogen compounds by nitrification reaction. The purpose is to do. Since the organic matter in the wastewater is sufficiently removed by the fluidized bed reactor in the previous stage, there is no inhibitory effect on the nitrification reaction of the organic matter, and the nitrification reaction can be efficiently advanced. Efficient nitrification reaction by immobilizing nitrifying bacteria with slow growth rate at high concentration by using saddle-type ceramics, silica-alumina ceramics, and plastics, which are mainly made of granulated blast furnace slag, as a carrier for immobilizing microorganisms. You can proceed. In particular, saddle-type ceramics that use granulated blast furnace slag as the main raw material have calcium as the main component, so nitrifying bacteria are easily immobilized,
Further, since it has a saddle shape, the gas-liquid mixing performance in the fixed bed reactor is excellent, and it is most desirable as the immobilization carrier for the fixed bed reactor. Furthermore, by maintaining the ORP of the fixed bed reactor at +100 mV (gold-silver / silver chloride electrode standard) or more, reducing nitrogen compounds such as Kjeldahl nitrogen compounds and ammoniacal compounds are converted into nitrate nitrogen compounds by nitrification reaction. It can be efficiently oxidized. When the concentration of reducing nitrogen compounds in wastewater is high,
In air aeration, it may be difficult to maintain the ORP of the reactor at +100 mV or more, and in such a case, oxygen enriched air and / or oxygen may be supplied to perform aeration. Furthermore, the microorganisms that flow out of the fixed-bed reactor into the treated water are calculated as suspended solids (SS),
By providing a filtration device filled with saddle-type ceramics containing granulated blast furnace slag as a main material in the subsequent stage of the fixed bed reactor, it is possible to remove efficiently at a filtration rate of 50 to 100 m / day.

[0014]

[Example] In an urban sewage treatment plant into which a large amount of organic industrial wastewater flows, a field experiment was conducted using actual sewage as shown in Fig. 1. As shown in Table 1, the characteristics of actual sewage are BO
D averages 600 mg / L, COD averages 450 mg / L
L and ammoniacal nitrogen are 150 mg / L on average, and the sewage has an organic matter concentration and ammoniacal nitrogen concentration that are extremely higher than those of municipal sewage.

[0015]

[Table 1]

The fluidized bed reactor 3 has an average particle size of 60.
Micron-sized granulated blast furnace slag fine powder was added as a microorganism-immobilized carrier in an amount of 3 wt% per reactor volume, and after acclimatization of activated sludge for about 10 days, the treatment time of the reactor was 8
~ 12 hours (BOD volume load 1.2-1.8 kg /
The actual sewage was passed through and treated so as to have m ³ ). Further, the ORP of the fluidized bed reactor 3 is +5 by air.
It was maintained at 0 mV.

The fixed bed type reactor 11 is filled with saddle type ceramics (FIG. 2), which is mainly made of granulated blast furnace slag, as a microorganism immobilization carrier, charged with activated sludge and circulated for one day, After immobilizing the activated sludge on the ceramics, the treated water was passed through the fluidized bed reactor so that the reactor treatment time was 6 to 8 hours. Further, the ORP of the fixed bed reactor 11 was maintained at +100 mV or more by oxygen-enriched air. At the outlet of the fixed bed reactor 11, a filtration device 13 filled with saddle type ceramics containing granulated blast furnace slag as a main material was installed and operated so that the filtration speed was 50 to 100 m / day.

The experimental results are shown in Table 1. From the results in Table 1,
The final treated water has a BOD of 10 mg / L or less and a COD of 60.
mg / L or less, SS is 15 mg / L or less, ammoniacal nitrogen is 15 mg / L or less, nitrite nitrogen is 10 mg / L
It was good as follows.

Further, it was revealed from the nitrogen balance of the sewage and the treated water that the denitrification reaction occurred in the ceramics-filled filtration device 13.

From these experimental results, it became clear that the method of the present invention can efficiently remove organic substances and reducing nitrogen compounds in sewage.

[0021]

From the above, the present invention has the following effects in the treatment of wastewater containing a high concentration of reducing nitrogen compounds such as Kjeldahl nitrogen compounds and ammoniacal compounds.

Since the organic substance removal process by the fluidized bed reactor and the reducing nitrogen compound removal process of the Kjeldahl nitrogen compounds, ammonia compounds and the like by the fixed bed reactor are carried out in two stages, the organic substances and nitrogen are removed in each process. Excellent performance. That is, reducing nitrogen compounds such as ammoniacal nitrogen can be efficiently oxidized to nitrate nitrogen as compared with a single treatment process using a fluidized bed reactor or a fixed bed reactor.

The removal of organic substances by the fluidized bed reactor is excellent in treatment efficiency and removal performance because it is treated with an ORP suitable for oxidative decomposition while using a microorganism-immobilized carrier.

Since the reducing nitrogen such as ammoniacal compound is removed by the fixed bed reactor by using the ORP suitable for nitrification reaction while using the microorganism-immobilized carrier, the treatment efficiency and the removal performance are excellent.

[Brief description of drawings]

FIG. 1 illustrates the method of the present invention.

FIG. 2 is a view showing a saddle type ceramics.

[Explanation of symbols]

 1 Waste Water Tank 2 Waste Water Pump 3 Fluid Bed Type Reactor 4 Blower 5 ORP Sensor 6 ORP Controller 7 Sludge Settling Tank 8 Return Sludge Pump 9 Treated Water Tank 10 Transfer Pump 11 Fixed Bed Reactor 12 Ceramics Packing Tank 13 Filtration Device 14 Ceramics Packing Tank 15 ORP sensor 16 ORP control device 17 Oxygen-enriched air manufacturing device 18 Treated water 19 Saddle type ceramics

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location C02F 9/00 A 6647-4D

Claims (4)

[Claims] 1. A method for treating high-concentration nitrogen-containing wastewater, wherein two-stage treatment of a fluidized bed reactor and a fixed bed reactor using a microorganism-immobilized carrier is performed to remove organic matter and reducing nitrogen compounds in the wastewater. A method for treating high-concentration nitrogen-containing wastewater, characterized by simultaneous removal. 2. The method for treating highly concentrated nitrogen-containing wastewater according to claim 1, wherein granulated blast furnace slag is used as the microorganism-immobilized carrier of the fluidized bed reactor. 3. The method for treating high-concentration nitrogen-containing wastewater according to claim 1, wherein saddle-type ceramics containing blast-furnace granulated slag as a main material is used as the microorganism-immobilized carrier of the fixed-bed reactor. 4. The method according to claim 1, wherein the amount of air and / or oxygen-enriched air and / or oxygen blown into the fluidized bed reactor and / or the fixed bed reactor is controlled by using the redox potential of the reactor. 3. The method for treating wastewater containing high-concentration nitrogen according to 3.