JP3477161B2 - Wastewater treatment method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating wastewater, and more particularly, to treating wastewater having a high chromaticity and a large amount of nitrogen (ammonia nitrogen) compared to BOD components.
Particularly, it relates to nitrogen removal and decolorization treatment technology.

[0002]

2. Description of the Related Art Livestock wastewater, which is highly concentrated organic wastewater, is
Nitrogen content (ammonia nitrogen) is larger than that of the component D, the electron donor required for biological denitrification is insufficient, and nitrogen removal tends to be incomplete. Further, this wastewater has a coloring component derived from humic substances, and treatment of such wastewater, particularly nitrogen removal and decolorization, has become a major problem in livestock wastewater treatment.

Conventionally, Thiobacillus denitri is an autotrophic bacterium that utilizes sulfur as an electron donor for denitrification instead of organic matter for denitrification of wastewater containing nitrate nitrogen components.
Denitrification using ficans (a kind of sulfur-oxidizing bacteria) has been attempted (JP-A-11-299481). In these systems, the wastewater is once nitrified in the nitrification tank, the nitrogen content is converted to nitrate nitrogen, and then sulfur denitrification is performed in another tank, so the equipment becomes bulky and the energy for nitrifying ammonia to nitric acid is also used. large.

On the other hand, an aerobic nitrification bed and an anaerobic denitrification bed are formed in a single tank, and treated water is circulated between them in an upward flow or a downward flow, and by a facultative anaerobic heterotrophic bacterium. Denitrification method (Japanese Patent Publication No. 63-19239, Japanese Patent Publication No. 1-379)
No. 88, Japanese Patent Application Laid-Open No. 8-1193, etc.) have also been proposed.

In these methods, the apparatus space is relatively small, but the energy consumption required for nitrification up to nitric acid is large as in the above case, and the BOD as described above is used.
In order to denitrify wastewater with low T / N ratio, addition of an electron donor such as methanol is indispensable, and it is difficult to properly add and control the injection amount, and a process for removing excess methanol is also required. There's a problem. Furthermore, in the above-mentioned denitrification treatment by sulfur-oxidizing bacteria and this single-tank nitrification and denitrification treatment, decolorization of wastewater requires a new decolorization treatment (activated carbon adsorption method or ozone oxidation method). The equipment space is large and the processing cost is high.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and it is excellent in space saving and energy saving, and is a single unit of drainage capable of simultaneously removing nitrogen and decolorizing. A tank treatment method and apparatus are provided.

[0007]

According to the method of the present invention, waste water is supplied between the aerobic nitrification section formed in the upper part of the tank and the decolorization / denitrification section formed in the lower part of the tank having sulfur and alkali components. While maintaining the pH in the tank at 7.6 or higher, the treated water is circulated from the aerobic nitrification section to the decolorization / denitrification section at a predetermined circulation ratio, and the BOD / T-N ratio of the upstream is increased. It is characterized by treating low wastewater.

As described above, the circulation between the aerobic nitrification section and the decolorization / denitrification section of a single tank enables nitrification and denitrification in one tank, and the pH in the tank is 7.6 or more. If the ammonium nitrogen concentration is about 100 mg / L or more, the free ammonia nitrogen concentration in the tank will be about 1 mg / L.
As described above, nitrite oxidation (generation of nitrate nitrogen) is suppressed, nitrification energy is small, and coloring components (humic substances, etc.) of wastewater are decomposed due to sulfur oxidation, and decolorization occurs at the same time as denitrification. Be seen. At this time, if the circulation ratio of the treated water is set to about 2 to 4, all of nitrification up to nitrous acid, denitrification, and decolorization proceed efficiently.

When the decolorizing / denitrifying portion is formed of a mixed granular material composed of sulfur and calcium carbonate, the alkaline component is released smoothly, the pH is properly maintained, and the handling is easy.

The wastewater treatment equipment of the present invention comprises a fixed filter medium bed formed in the upper part of the treatment tank, a sulfur-containing filter medium bed formed in the lower part for holding sulfur and alkaline components, and aeration provided below the fixed filter medium bed. Means, drainage supplying means located below the aeration means and above the sulfur-containing filter medium bed, circulation means for circulating treated water from the upper part to the bottom part of the treatment tank, and treated water discharge means provided at the upper part of the treatment tank. It is characterized in that the wastewater having an upward flow and a high chromaticity and a low BOD / TN ratio is treated.

In the device of the present invention, DO (dissolved oxygen) is used.
By maintaining and controlling the pH value, nitrification, denitrification, and decolorization can be performed in a single tank while suppressing nitrite oxidation, and a wastewater treatment device excellent in space saving and energy saving can be provided.

The sulphur-containing filter medium bed formed from a granular body containing sulfur and calcium carbonate is easy to handle,
Excellent retention of sulfur-oxidizing bacteria, smooth release of alkaline components, and pH maintained at an appropriate value. In addition, when decolorization proceeds sufficiently even with the minimum aeration strength necessary for nitrification up to nitrous acid, a floating filter media bed is provided between the fixed filter media bed and the sulfur-containing filter media bed, and the lower sulfur-containing filter media bed is installed. Oxygen diffusion is suppressed, and the DO concentration of the sulfur-containing filter medium bed is kept low to suppress unnecessary sulfur oxidation. Also, a fixed filter medium bed made of a fiber knitted tube and a non-woven material and a floating filter medium bed made of a lumped polyurethane foam have a high ability to retain microorganisms and are inexpensive, so that a practical biofilm filter bed can be formed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the device and method of the present invention will be described in detail with reference to the drawings showing an embodiment of the device of the present invention. FIG. 1 is a schematic side sectional view of an embodiment of the wastewater treatment device of the present invention to which a sedimentation tank is added, and FIG. 2 is a schematic cross-sectional view of another embodiment of the wastewater treatment device of the present invention to which a sedimentation tank is added. It is a figure.

In FIG. 1, the main body 1 of the processing tank is a vertical cylindrical tank body, and a conical hopper 1a is formed at the bottom.
A fixed filter medium bed 2 filled with a filter medium composed of a fiber knitting tube and a non-woven material is provided on the upper portion. Fixed filter media floor 2
A disk-shaped air diffusing device 3 which is an aeration means is provided below. The air diffuser 3 diffuses air from a blower or a compressor (not shown) provided outside the tank into the air diffuser 3a.
Is supplied from the air diffuser 3, and air is jetted from the porous surface of the upper surface of the air diffuser 3 to supply air, that is, oxygen, to the fixed filter medium bed 2 to form an aerobic layer.

At the lower part of the main body 1 and on the hopper 1a, there is formed a sulfur-containing filter medium bed 4 which is filled with granular materials composed of sulfur and calcium carbonate (hereinafter referred to as sulfur-containing filter medium). As the granular material, for example, the composition described in JP-A No. 11-285377 is preferably used. However, if the composition contains sulfur and an alkaline component, the sulfur-containing filter medium bed 4 is filled with an appropriate granular material. Can be formed.

A drainage supply pipe 5 having a pump 5a, which is a drainage supply means, opens on the side wall of the main body 1 above the sulfur-containing filter medium bed 4 and supplies drainage from here. The treated water circulation pipe 6 having a pump 6a, which is a circulation means, is connected from the side wall of the tank main body 1 above the fixed filter medium bed 2 to the bottom of the lower hopper 1a, and a predetermined amount of treated water is circulated by the pump 6a. . A discharge pipe 7 which is a means for discharging treated water is connected to the circulation pipe 6, and a settling tank 8 having a hopper 8a at the bottom due to overflow of the treated water in an amount corresponding to the supply and drainage from the discharge pipe 7.
To introduce. The supernatant water of the settling tank 8 is taken out as treated water from the overflow pipe 8b.

Next, a wastewater treatment method using this wastewater treatment equipment will be described. Prior to the wastewater treatment, nitrifying bacteria are acclimated to the fixed filter media based on the activated sludge of the livestock wastewater treatment facility, and are made to adhere to the fixed filter medium. While maintaining the DO of the sulfur-containing filter medium bed at a low level while circulating the circulation pipe 6 with the sulfur-containing filter medium, the sulfur-containing filter medium is acclimated and adapted to the sulfur-oxidizing bacteria. Perform processing.

In the method of the present invention, the filling amount of the sulfur-containing filter medium is determined so that the pH in the tank becomes 7.6 or more, and the circulation ratio of treated water (circulated amount of treated water / amount of supplied waste water) is 2 to 4. To Since the pH in the tank is maintained at 7.6 or more by the alkaline component released from the sulfur-containing filter medium, when the ammonia nitrogen concentration is about 100 mg / L or more, the free ammonia nitrogen concentration is at a level of 1 mg / L or more. , The nitrite oxidation is suppressed, the oxygen consumed for nitrification is reduced, and the energy required for aeration is reduced. Also, at the bottom of the sulfur containing filter media bed maintained at a low DO level,
Denitrification is performed by sulfur-oxidizing bacteria, and along with the sulfur oxidation reaction of the sulfur-oxidizing bacteria, humic substances and other coloring components in the wastewater are decomposed in all layers of the sulfur-containing filter media bed, and the wastewater is also decolorized. If the pH exceeds 8.5, it is not suitable for discharging treated water. Therefore, it is preferable to keep the pH at 8.5 or less.

In the apparatus of the embodiment shown in FIG. 1, the DO at the upper part of the sulfur-containing filter medium bed 4 is 1.5 m in order to accelerate decolorization.
It is maintained at about g / L or more, and the lower part of the sulfur-containing filter medium bed 4 is maintained at DO at a level not deteriorating denitrification. Here, in order to further improve the decolorizing performance, the amount of aeration may be increased in the apparatus of FIG. 1 to increase the DO in the upper portion of the sulfur-containing filter medium bed to accelerate the sulfur oxidation.

When decolorization is sufficiently advanced even with the minimum aeration intensity required for nitrification up to nitrous acid, excessive diffusion of the sulfur filter medium is prevented by suppressing oxygen diffusion to the upper part of the sulfur-containing filter medium bed. It is better to do so. In order to prevent oxygen diffusion into the sulfur-containing filter medium bed, as in the embodiment shown in FIG. 2, a floating filter medium bed 9 filled with a floating filter medium made of polyurethane foam may be arranged above the sulfur-containing filter medium bed 4A. .
2 is the same as that of FIG. 1 except that the floating filter medium bed 9 is arranged and the thickness of the sulfur-containing filter medium bed 4A is made thin, and those having the same functions as those of FIG. , Description is omitted.

In the above description, the sulfur filter medium containing calcium carbonate was used to supplement the alkaline component. However, in the sulfur-containing filter medium bed, lumpy simple sulfur was used, and a granular material containing calcium and gradually dissolving was used. The alkaline components may be mixed, and an alkaline solution such as caustic soda or caustic potash may be appropriately injected to control and maintain the pH in the tank. However, it is convenient to use a mixed granulated product of sulfur and calcium carbonate, and it is stable as a filter bed.

[0022]

EXAMPLE An example in which wastewater treatment was carried out using the treatment apparatus shown in FIG. 2 will be described, and the effect of the present invention will be described in comparison with a comparative example. The volume of the apparatus is 28 L of tank main body, 10 L of fixed filter media floors, 2.5 L of sulfur containing filter media floors, 10 of floating filter media floors.
It is L, and the sewage of pig house is the UA for 2 days of HRT.
Using wastewater treated with SB (shown in Table 1), this wastewater was introduced into a treatment tank maintained at 20 ° C, and HRT was set to 2 days (inflow wastewater volume: 0.54 L / day), and a circulation ratio of 8 (comparative example), Four
(Example) 2 (Example), 1 (Comparative Example), 0 (Comparative Example) were changed, and the processing of the Example was performed together with the Comparative Example. The results are shown in Table 2.

[Table 1]

[Table 2] From this result, it can be understood that nitrogen removal is promoted and a relatively large amount of sulfate ion is generated at a circulation ratio level of 2 to 4, and the decolorizing performance is well expressed. In the above description of the present invention, the emphasis has been placed on nitrogen removal and decolorization. However, in the method and apparatus of the present invention, at the same time as nitrogen removal and decolorization, each pollutant component (BOD, CO
It is clear from the above results that the D component) is also significantly removed.

The pH in each table was measured with a pH meter and the Col
or (U) (coloring degree) was centrifuged at 15000 rpm for 5 minutes to remove the suspension, and then the coloring degree meter (NDR-20
00, Nippon Denshoku Industries Co., Ltd.). BOD is HACK
The 5-day method using a BOD TRACK automatic measuring device manufactured by Co., Ltd. was used to measure TCODcr by the COD measuring system (DR / 700 Colorimeter & COD React) manufactured by HACK.
or) was used for the measurement. TN (total nitrogen) and TP
For (total phosphorus), a flow injection analyzer (TN / TP meter) manufactured by Sanuki Co., Ltd. was used, and TN was 140 °.
The T-P was quantified by the 880 nm absorbance measurement by the molybdenum blue method after the decomposition of potassium persulfate at 140 ° C by the absorbance under the acidic condition of hydrochloric acid after the decomposition of potassium persulfate C. NH4-N is a flow injection method (Aquatec
5400 Analyzer Foss Tecator, AQUATEC)
Measured by NO3-N, NO2-N, PO4-P and SO4-S, dilute the sample 50-fold and use Millipore HA
After filtering with a filter, it was analyzed by ion chromatography (IC7000, Yokogawa).

[0024]

According to the method of the present invention, waste water is supplied between the aerobic nitrification section formed in the upper part of the tank and the decolorization / denitrification section formed in the lower part of the tank which has sulfur and alkali components. While maintaining the internal pH at 7.6 or higher, the treated water is circulated from the aerobic nitrification section to the denitrification section at a predetermined circulation ratio, and BOD / T is applied in an upward flow.
-Since wastewater with a low N ratio is treated, there is no need to add a carbon source such as methanol, maintenance is easy, there is little nitrification energy, and space-saving equipment can simultaneously perform denitrification and decolorization. It is a treatment method and apparatus which can be used and which is particularly suitable for colored wastewater having a low BOD / TN ratio.

[Brief description of drawings]

FIG. 1 is a schematic side sectional view of an embodiment of the wastewater treatment apparatus of the present invention to which a sedimentation tank is added.

FIG. 2 is a schematic side sectional view of another embodiment of the wastewater treatment apparatus of the present invention to which a sedimentation tank is added.

[Explanation of symbols]

1 Processing tank body 2 Fixed filter media floor 3 Air diffuser (aeration means) 4, 4A Sulfur-containing filter media bed 5 Drainage supply pipe (drainage supply means) 6 Circulation pipe (circulation means) 7 discharge pipe (discharge means) 8 settling tank 9 Floating filter media floor

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yasuo Tanaka 4-26, Matsushiro, Tsukuba-shi, Ibaraki 412-101 (56) References JP-A-11-285377 (JP, A) JP-A-11-319880 (JP , A) JP 63-123496 (JP, A) JP 64-47495 (JP, A) Tadano Hano et al., Development of nitrogen removal system by autotrophic bacteria, Chemical engineering, Japan, Chemical Engineering Society, 1997 February 5, Vol. 61, No. 2, p. 50, 51 (58) Fields investigated (Int.Cl. ⁷ , DB name) C02F 3/28-3/34 C02F 3/02-3/12

Claims (7)

(57) [Claims] 1. A drainage is supplied between an aerobic nitrification section formed in the upper part of the tank and a decolorizing / denitrifying section having sulfur and alkali components and formed in the lower part of the tank, and the pH in the tank is 7.6. While maintaining the above, the treated water is circulated from the aerobic nitrification section to the decolorization / denitrification section at a predetermined circulation ratio, and the upward flow has high chromaticity and high BOD /
A wastewater treatment method comprising treating wastewater having a low TN ratio. 2. The wastewater treatment method according to claim 1, wherein the decolorizing / denitrifying portion is formed of a granular body made of sulfur and calcium carbonate. 3. The circulation ratio is set to 2 or more and 4 or less.
Or the wastewater treatment method described in 2. 4. A fixed filter medium bed formed in the upper part of the treatment tank, a sulfur-containing filter medium bed formed in the lower part for holding sulfur and alkali components, aeration means provided below the fixed filter medium bed, and the aeration. Wastewater supply means located below the means and above the sulfur-containing filter medium bed, circulation means for circulating treated water from the upper part of the treatment tank to the bottom part, and treated water discharge means provided at the upper part of the treatment tank, Upward flow and high chromaticity BOD / T-
A wastewater treatment device that treats wastewater having a low N ratio. 5. The waste water treatment apparatus according to claim 4, wherein the sulfur-containing filter medium bed is formed of a granular body containing sulfur and calcium carbonate. 6. The waste water treatment apparatus according to claim 4, wherein a floating filter medium bed is provided between the fixed filter medium bed and the sulfur-containing filter medium bed. 7. The waste water treatment apparatus according to claim 6, wherein the fixed filter medium bed is made of a fiber knitting tube and a non-woven fabric material, and the floating filter medium bed is made of block polyurethane foam.