JP2014057919A - Waste water treatment apparatus, column, and waste water treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste water treatment apparatus which allows for efficient biological ammoniacal nitrogen removal.SOLUTION: A column 20 is filled with a filler 200 i.e. a herbaceous biomass delignification treated with alkali. A denitrification reaction tank 100 internally includes a plurality of columns 20 vertically disposed on a partition 110. The denitrification reaction tank 100 is provided with a valve 160 for injecting water to be treated at a lower part, and a valve 180 for acquiring treated water at an upper part, so that the water to be treated is supplied in upward direction.

Description

  The present invention relates to a wastewater treatment apparatus, a column, and a wastewater treatment method, and more particularly to a wastewater treatment apparatus, a column, and a wastewater treatment method for performing biological denitrification.

  Conventionally, wastewater treatment facilities mainly use microorganisms to reduce nitrite nitrogen and nitrate nitrogen in wastewater (treated water) in the presence of readily decomposable organic substances, and remove them in the gaseous state (hereinafter referred to as “ "Denitrification"), a biological denitrification method is used.

As a conventional denitrification method using microorganisms, referring to Patent Document 1, a nitrification tower that nitrifies ammoniacal nitrogen in wastewater with nitrifying bacteria that are aerobic autotrophic bacteria, nitrate nitrogen, and nitrite nitrogen Is a treatment method of nitrogen-containing wastewater using a biological nitrification denitrification apparatus having a denitrification tower for denitrification treatment with a denitrifying bacterium that is an anaerobic bacterium. Treatment of nitrogen-containing wastewater characterized by supplying treated water after nitrification denitrification treatment to the nitrification tower and using carbon dioxide dissolved in the treatment water as an inorganic carbon source necessary for the growth of the nitrifying bacteria A method is described (hereinafter referred to as Prior Art 1).
According to the prior art 1, there is provided a method for treating nitrogen-containing wastewater that can supply inorganic carbon necessary for the growth of nitrifying bacteria without using a special device and is inexpensive.

JP 2011-62653 A

Here, when the biological ammonia nitrogen removal method as in the prior art 1 is used for waste water containing less easily decomposable organic matter and phosphoric phosphorus, which are microbial energy sources, such as waste landfill leachate. Requires the addition of methanol as the hydrogen donor and phosphoric acid as the phosphorus source.
However, when chemicals such as methanol and phosphoric acid are added, there is a problem that the cost of wastewater treatment is high.
In addition, when treating wastewater, there has been a demand for a wastewater treatment apparatus that can treat the water to be treated with a small installation area and does not require a chemical injection tank or chemical injection pump.

  This invention is made | formed in view of such a condition, and makes it a subject to eliminate the above-mentioned subject.

In the wastewater treatment apparatus of the present invention, a water-permeable column filled with herbaceous biomass that has been delignified with alkali is disposed in the vertical direction, and the water to be treated is supplied upward from the bottom. A denitrification reaction tank is provided.
The wastewater treatment apparatus of the present invention is characterized in that the herbaceous biomass is compressed and pressure-molded to an appropriate filling rate against fluctuations in water temperature and water quality.
The wastewater treatment apparatus of the present invention is characterized in that the herbaceous biomass is Phragmites.
The wastewater treatment apparatus according to the present invention is characterized in that a packing rate of the metal in the column is 25% to 65%.
In the wastewater treatment apparatus of the present invention, the herbaceous biomass is rice husk.
The wastewater treatment apparatus of the present invention is characterized in that the filling rate of the rice husks into the column is 15% to 45%.
The wastewater treatment apparatus of the present invention is characterized in that the column is replaced when the oxidation-reduction potential accompanying denitrification changes at a predetermined voltage or higher.
The wastewater treatment apparatus of the present invention is characterized in that an appropriate contact residence time of the treated water is adjusted by the oxidation-reduction potential.
The column of the present invention is filled with herbaceous biomass that has been delignified with an alkali, and the herbaceous biomass is compressed and pressure-molded to an appropriate filling rate against changes in water temperature and water quality.
The wastewater treatment method of the present invention is characterized in that herbaceous biomass subjected to delignification treatment with alkali is contacted with water to be treated as a microorganism carrier for denitrification.
The wastewater treatment method of the present invention is characterized in that the herbaceous biomass is Phragmites.
The wastewater treatment method of the present invention is characterized in that the treated water is waste landfill leachate.

  According to the present invention, by using herbaceous biomass that has been delignified with alkali, it is not necessary to add chemicals such as methanol and phosphoric acid, and the cost of wastewater treatment can be reduced. A wastewater treatment method that is not required can be provided.

It is a photograph of the appearance of waste water treatment equipment 1 concerning an embodiment of the invention. It is the top view and side view of the wastewater treatment apparatus 1 which concern on embodiment of this invention. It is a perspective view which shows filling of the plant body to the column 20 which concerns on embodiment of this invention. It is a conceptual diagram which shows the process of the filling of the plant body to the column 20 which concerns on embodiment of this invention. It is a graph which shows the solubilization rate of Example 1 which concerns on embodiment of this invention. It is a conceptual diagram which shows the outline | summary of a structure of the waste water treatment apparatus 1, 2, 3, 4 of Example 2 which concerns on embodiment of this invention. It is a figure which shows the comparison result of the upflow type reaction tank of Example 2 which concerns on embodiment of this invention, and a crossflow type reaction tank. It is a figure which shows the influence of the filling rate which acts on denitrification of Example 3 which concerns on embodiment of this invention. It is a graph which shows the comparison of the denitrification result with the conventional methanol denitrification method of Example 4 which concerns on embodiment of this invention. It is a graph which shows the relationship between the nitrous acid and nitrate nitrogen concentration of Example 4 which concerns on embodiment of this invention, and oxidation-reduction potential. It is a figure which shows the structure of the waste water treatment apparatus 5, 6, 7, 8 of Example 5 which concerns on embodiment of this invention. It is a figure which shows the result of Example 5 which concerns on embodiment of this invention. It is a graph which shows the denitrification result of the waste water treatment apparatus 5 of Example 5 which concerns on embodiment of this invention. It is a graph which shows the denitrification result of the waste water treatment apparatus of Example 5 which concerns on embodiment of this invention.

<Embodiment>
[Configuration of waste water treatment apparatus 1]
With reference to FIGS. 1-2, the structure of the waste water treatment apparatus 1 which concerns on embodiment of this invention is demonstrated. FIG. 1A is a photograph of a side surface of the wastewater treatment apparatus 1, and FIG. 1B is a photograph of a plane of the wastewater treatment apparatus 1. 2A is a plan view of the wastewater treatment apparatus 1, and FIG. 2B is a side view of the wastewater treatment apparatus 1.
The wastewater treatment apparatus 1 is an example of an apparatus for realizing the biological ammonia nitrogen removal method according to the embodiment of the present invention. In the wastewater treatment apparatus 1, a denitrification reaction tank 100 is provided with a treated water input valve 160, a treated water acquisition valve 180, and a sludge extraction valve 190. Further, a plurality of columns 20 are arranged inside the denitrification reaction tank 100, and a partition 110 that supports the column 20 is provided.

The column 20 is filled with a filler 200 such as a plant body, and is denitrified by attaching denitrifying bacteria or cellulose-decomposing bacteria in the seeding liquid planted from the treated water (waste water). For example, a cylindrical column. As a seeding solution for this denitrifying bacterium or cellulose-degrading bacterium, primary sedimentation sludge, activated sludge, anaerobic digestion sludge, river sediment, and soil extract from a sewage treatment plant can be used directly or diluted.
The side surface of the column 20 is provided with a plurality of mesh nets and holes to the extent that the filler 200 does not flow out, so that the water to be treated can be infiltrated into the inside.
Since the filling material 200 is filled with the plant body pressed as described later, voids decrease toward the lower part due to its own weight and compaction, and an anaerobic environment effective for denitrification is naturally formed. The details of filling the column 20 with the filler 200 will be described later.

The denitrification reaction tank 100 is a cylindrical reaction tank made of a corrosion-resistant material such as stainless steel or titanium. For example, the denitrification reaction tank 100 is arranged such that the longitudinal direction is the same vertical direction as the gravity direction, and a plurality of columns 20 are placed vertically inside. On this, the denitrification reaction tank 100 is configured such that, for example, the lower surface is sealed to hold the water to be treated, and the upper surface is released to be in contact with the atmosphere.
In the denitrification reaction tank 100, a partition 110 is disposed, and a plurality of columns 20 filled with a filler are disposed thereon. At this time, a plurality of partitions 110 may be arranged, and the columns 20 may be arranged in a plurality of stages. FIG. 2 shows an example in which two columns 110 are used and the column 20 is arranged in two stages.
Further, the denitrification reaction tank 100 is provided with a treated water input valve 160 and a sludge extraction valve 190 in the lower part, and a treated water acquisition valve 180 in the upper part. Thereby, the denitrification reaction tank 100 comprises an upward flow type reaction tank.

The partition 110 is a plate made of a corrosion-resistant material having a mesh or a hole for supporting the column 20. The partition 110 is fixed upward from the bottom surface of the denitrification reaction tank 100 by a predetermined distance. When a plurality of partitions 110 are arranged, they may be fixed according to the height of the column 20.
Precipitation sludge is stored in the lower part of this partition 110, and denitrification reaction is advanced in the column 20 mounted in the upper part. In addition, the structure which does not use the partition 110, or the structure which suspends the column 20 from upper part is also possible.

  The treated water charging valve 160 is a valve for charging or stopping treated water such as waste water (raw water) for performing denitrification into the denitrification reaction tank 100. In addition, the amount of water to be treated may be adjusted by changing the amount of opening and closing by the water to be treated inlet valve 160.

  The treated water acquisition valve 180 is a valve for collecting treated water that has been denitrified. This treated water may be separately supplied to another wastewater treatment apparatus.

  The sludge extraction valve 190 is a valve for extracting sludge in the water to be treated and sludge generated and precipitated from the denitrification reaction tank. As shown in FIG. 2, the treated water input valve 160 is provided in the lower part of the partition 110, and the sludge settled from the sludge extraction valve 190 can be efficiently taken out by the momentum of input of the treated water. It becomes possible.

  Moreover, as shown in FIG. 6 which concerns on the following Example 2, the waste water treatment apparatus 1 can connect the to-be-treated water tank 40, the pump 50, the to-be-treated water line 60, etc. Furthermore, as will be described later, a filler such as a plant can be directly filled into the denitrification reaction tanks 100, 101, and the like.

(Configuration of upward flow reactor)
As described above, the denitrification reaction tank 100 is preferably configured in an upward flow type in which the packing material such as the column 20 or the plant body is arranged in a direction perpendicular to gravity. This is because the upward flow type has a smaller contact area with the atmosphere of the water to be treated, and as a result, an anaerobic environment is easily maintained.
Actually, as shown in Example 2 described later, a wastewater treatment device 3 and a wastewater treatment device 4 (FIG. 6) that are a horizontal flow type in which wastewater flows horizontally, an upward flow type wastewater treatment device 1 and a wastewater treatment device. As a result of comparing the denitrification effect of No. 2, the upward flow type showed high denitrification ability.

Further, as described above, the denitrification reaction tank 100 has the treated water input valve 160 provided at the lower part of the denitrification reaction tank 100 and the treated water acquisition valve 180 provided at the upper part of the denitrification reaction tank 100. . As described above, since an anaerobic environment effective for denitrification is naturally formed in the lower part of the column 20, the nitrification water of the landfill leachate containing oxygen is used as the treated water from the lower part. This is because it is preferable to flow in. Further, when the upward flow type is configured, the sedimentation rate of the suspended matter including the filler is reduced due to the liquid level rising effect, and clogging is less likely to occur, and the sludge withdrawing valve 190 at the lower portion makes it easier to remove the precipitated sludge.
For this reason, it becomes effective for denitrification to comprise the denitrification reaction tank 100 as an upward flow type reaction tank which flows a to-be-processed water from the bottom to the top.

The shapes of the column 20 and the denitrification reaction tank 100 are not limited to the cylindrical shape, and various shapes such as an elliptic cylinder, a rectangular column, and a polygonal column can be used.
Moreover, the structure which arrange | positions the denitrification reaction tank 100 on a disk, rotates, and applies a centrifugal force instead of gravity is also possible. Thereby, the effect that it becomes easy to remove sludge with a centrifugal force is also acquired.

[Method for producing column 20]
Next, with reference to FIG. 3 and FIG. 4, the manufacturing method of the column 20 used for the ammonia nitrogen removal method which concerns on embodiment of this invention is demonstrated.
As shown in FIG. 3, the column 20 is packed with a plant body that is a biomass carrier as a filler 200.
At this time, the packing material 200 used for the column 20 can be a variety of plant bodies including a carbon source / phosphorus source necessary for denitrification and cellulose serving as a bacterial adhesion carrier.
In particular, it is preferable to use an alkali-treated cocoon as the plant body as described later.

(Configuration of filler 200)
More specifically, as the plant used for the filler 200, weeds, rice straw, rice husks, straw, etc., which are herbaceous biomass, can be used. In addition, thinned wood, pruned wood, bark, wood fragments, waste wood, wood chips, sawdust, sawdust, disposable chopsticks, old tatami mats, waste paper, waste pulp, etc., which are woody biomass, can also be used as plants. .
Among these, as the filler 200 according to the present embodiment, it is preferable to use alkali-treated stems of Phragmites, etc., particularly as herbaceous biomass. The soot is suitable as a filler for denitrification because of its hardness and surface area. In particular, persimmons grow by absorbing large amounts of nitrogen and phosphorus, so reuse by harvesting leads to environmental purification. In addition, cocoons are excellent in price and availability.
Below, in the wastewater treatment apparatus 1 of this embodiment, the example which uses the stalk of the cocoon which was alkali-treated for the filler 200 is demonstrated.
By filling the column 20 with a packing material 200 that is a herbaceous biomass carrier that has been subjected to alkali treatment, denitrifying bacteria, cellulose-degrading bacteria, and the like adhere to the surface. Elution of phosphorous and the like makes it possible to reduce and remove nitric acid and nitrite nitrogen in wastewater.

(Alkali treatment of filler 200)
As a result of extensive research, the present inventors have succeeded in dramatically improving the denitrification performance by using the column 20 packed with the filler 200 delignified by alkali treatment. Completed the invention.
In the alkali treatment of the filler 200, for example, the plant body is immersed in an alkaline solution and stirred, and then washed so that the pH is close to neutrality, thereby delignifying. Thus, by performing delignification by alkali treatment, solubilization of the filler 200 can be promoted, the concentration of dissolved organic matter in the reaction tank can be increased, and higher denitrification performance can be ensured. Also, since lignin is difficult for microorganisms to decompose, by reducing this, the filler 200 is likely to become a nutrient source for microorganisms. Moreover, the surface area to which microorganisms adhere increases by stirring, and the function as a carrier can be improved.
As a specific alkali treatment, when using soot for the filler 200, the following treatment can be performed. For example, a dried potato stalk cut to 5 to 10 cm is poured into a 0.5M sodium hydroxide aqueous solution in a water tank so as to be 10% (w / v). Then, the added soot is stirred for about 2 hours while keeping the temperature of the aqueous sodium hydroxide solution at about 40 ° C. Next, the alkali-treated soot is immersed in the same amount of neutral water as the sodium hydroxide aqueous solution, stirred for about 1 hour, dehydrated and washed. By repeating this operation 5 to 6 times until the pH of the dehydrating liquid becomes 8.0 or less, the influence of sodium hydroxide on microorganisms can be eliminated.
The specific effect of this alkali treatment will be described in Example 1 described later.

(Packing step of column 20 with packing material according to the embodiment of the present invention)
Next, referring to FIG. 4, the packing process of the packing material 20 according to the embodiment of the present invention will be described.
First, as shown in FIG. 4A, after the dried soot is cut into 5 to 10 cm, lignin contained in the soot is solubilized and removed by an alkali treatment described later. Thereby, useful microorganisms, such as a cellulose, a hemicellulose decomposing bacterium, or a denitrifying bacterium, can make it easy to assimilate organic substances, such as a cocoon cellulose.
Next, as shown in FIG. 4B, the delignified soot is placed in the column 20 as a filler, and is compressed and pressure-molded by a press machine or the like and filled. As will be described later, the denitrification performance can be changed by changing the compression rate of the filler. At this time, it is possible to select an appropriate filling rate that provides stable denitrification ability against fluctuations in water temperature and water quality. Moreover, the wastewater treatment apparatus 1 provided with the column 20 can be reduced in size by being compressed and pressure-molded and filled. In addition, the filler 200 is reduced in the lower portion due to compaction, and an anaerobic environment suitable for denitrification is easily realized. After the filling material 200 is filled, the upper and lower sides of the column 20 are preferably sealed with a lid or the like.
FIG. 4C shows the appearance of the column 20 filled with the compressed filler 200.
FIG. 4D shows a photograph of the plane of the column 20 placed and loaded in the denitrification reaction tank 100. By using the cylindrical column 20, a plurality of columns 20 can be loaded into the denitrification reaction tank 100 with an appropriate gap. Thereby, it becomes possible to improve the reactivity and efficiency of denitrification. Moreover, the effect that it becomes easy to exchange the column 20 is acquired.

When alkali-treated soot is used for the filler 200, the dry weight base half-life is about 180 days, as shown in Example 1 described later. Therefore, stable denitrification ability can be maintained by replacing the filler 200 several times a year according to the quality of the water to be treated.
The timing of this exchange can be indirectly known by measuring a change in oxidation-reduction potential (ORP).
As shown in Example 4 to be described later, it can be understood that the denitrification proceeds sufficiently when the ORP is equal to or lower than the predetermined voltage.
Conversely, it can be seen that denitrification does not proceed when the ORP is equal to or higher than the predetermined voltage. Thus, when ORP becomes more than a predetermined voltage, it is considered that elution of easily decomposable organic substances and phosphorus elution are limiting factors for denitrification. Therefore, when the ORP changes for a predetermined time in a state where the ORP is equal to or higher than the predetermined voltage, it is preferable to replace the column 20 or the packing material.
In addition, when the ORP changes for a predetermined time at a predetermined voltage or higher, it is possible to adjust the residence time of the water to be treated in the denitrification reaction layer 100 of the water to be treated. That is, it is possible to adjust the water to be treated to have an appropriate contact residence time by using a predetermined oxidation-reduction potential accompanying reduction of nitrous acid / nitric nitrogen as a guide. At this time, if the ORP does not decrease even if the residence time is increased, it is preferable to replace the column 20 or the packing material.
As predetermined voltages of these ORPs, as shown in Example 4 to be described later, when an alkali-treated soot is used as a filler, for example, about −100 mV is preferably used.

In addition, when using alkali-treated soot for the filler 200, when efficiently denitrifying waste water containing less easily decomposable organic matter and phosphoric phosphorus, which are energy sources of microorganisms such as waste landfill leachate The packing rate into the column 20 is preferably about 25% to 65% (v / v), particularly about 40 to 50% (v / v). If it is less than 25%, the growth density of microorganisms such as nitrifying bacteria or denitrifying bacteria cannot be kept sufficiently, and sufficient denitrifying ability cannot be obtained. On the other hand, if the filling rate is higher than 65%, the voids cannot be kept sufficiently, and the water to be treated does not permeate into the column 20, so that sufficient denitrification ability cannot be obtained. Moreover, in an environment where easily decomposable organic substances and phosphorous phosphorus are sufficient, even if the compression rate is lowered to about 30% to 40% (v / v), sufficient denitrification ability can be obtained.
In addition, when an alkali-treated rice husk is used for the waste landfill leachate as the filler 200, a filling rate of about 15% to 45% (v / v) is preferable.

[Biological ammoniacal nitrogen removal method according to embodiments of the present invention]
As mentioned above, waste landfill leachate contains less readily decomposable organic matter and phosphorous phosphorus, so traditionally, in the biological ammonia nitrogen removal process of landfill leachate, hydrogen is donated in the denitrification process. Use methanol as the body and phosphoric acid as the phosphorus source. This incurs processing costs.
The inventor of the present invention has conducted extensive research to solve the above-described problems,
(1) The column 20 is packed with a filler 200 that is a herbaceous biomass carrier that has been delignified with an alkali,
(2) It is placed in a denitrification reaction tank 100 which is an upward flow reaction tank,
(2) By bringing the filler 200 into contact with the water to be treated as a microorganism carrier and supplying the water to be treated with easily decomposable organic substances and phosphorous phosphorus, the carbon neutral is excellent in cost and CO ₂ emission reduction. A biological ammonia nitrogen removal method was completed.

The treated water (treated water) of the ammonia nitrogen removing method according to the embodiment of the present invention includes nitrogen-containing inorganic industrial waste water, industrial waste landfill leachate, digestion desorption liquid, or low carbon / nitrogen. Organic wastewater with a ratio (C / N ratio) or nitrification water of these can be used. Ammonia nitrogen can be nitrified and denitrified from the water to be treated, and the total nitrogen concentration of the water to be treated can be significantly reduced.
For example, the biological ammonia nitrogen removal method of the present embodiment can biologically treat waste water containing a large amount of nitrogen leached from the final disposal site for industrial waste to remove nitrogen.
Specifically, as shown in Example 3 to be described later, the wastewater treatment apparatus 1 was flown for 60 days in the up-flow type wastewater treatment apparatus 1 with the leachate leachate requiring nitrification treatment as the treated water. However, a treatment performance with an average denitrification rate of 98% was obtained.

As described above, in the ammoniacal nitrogen removal method according to the embodiment of the present invention, it is not necessary to add chemicals such as methanol and phosphoric acid as in the prior art 1, and it is possible to reduce the cost of wastewater treatment. Become.
Moreover, since the wastewater treatment apparatus 1 which concerns on embodiment of this invention does not use methanol, phosphoric acid, etc. in the case of processing of to-be-processed water, a chemical injection tank and a liquid feed pump are not required. For this reason, to-be-processed water can be processed with a small installation area, and the cost of wastewater treatment can be reduced. In addition, by measuring the change in oxidation-reduction potential accompanying decomposition, the progress of denitrification can be grasped, and maintenance management becomes easy.
In addition, since the wastewater treatment apparatus 1 according to the embodiment of the present invention uses a biomass carrier such as a herbaceous system that is carbon neutral as the filler 200, CO ₂ emissions are reduced as compared with the case where methanol is used as the hydrogen donor. Can be reduced.
The wastewater treatment apparatus and the wastewater treatment method according to the embodiment of the present invention are not limited to nitrate nitrogen and nitrite nitrogen, but widely denitrify ammonia nitrogen, which is various compounds including other biological nitrogen. And can be removed.

  Hereinafter, a biological ammonia nitrogen removing method using the wastewater treatment apparatus 1 according to the embodiment of the present invention will be specifically described as an example. However, the present invention is not limited to the following examples.

(Comparison of alkali treatment, physical treatment, and no treatment)
First, referring to FIG. 5, the results of an experiment confirming the effectiveness of delignification by alkali treatment will be described as Example 1.
Specifically, the effect of pretreatment for promoting solubilization of organic matter of the biomass carrier according to the embodiment of the present invention was measured. For this reason, dried rice cake (produced in Watarase area, Tochigi Prefecture) is treated with alkali (filler 200), untreated (filler 210), pressurized hot water treatment (filler 220), and ultrasonic treatment (filler), respectively. 230) The solubilization rate of the organic matter was measured.
As a specific procedure for the alkali treatment, the filler 200 was charged with 10% (w / v) of dried cocoon stems cut to the same length as that of the untreated, in a 0.5M aqueous sodium hydroxide solution. . While keeping the temperature of the sodium hydroxide aqueous solution at 40 ° C., the added soot is stirred at 50 rpm for 2 hours. Next, in order to eliminate the influence of sodium hydroxide on microorganisms, the soot that had been subjected to alkali treatment was washed. The alkali-treated soot was dipped in the same amount of tap water as the sodium hydroxide aqueous solution and stirred at 50 rpm for 1 hour, and then dehydrated. This operation was repeated 5 to 6 times until the pH of the dehydrated liquid became 8.0 or less.
As the filler 210, 130 g was used as it was without being treated by cutting the same dry straw stem as the filler 200 into 5 to 10 cm.
The filler 220 used was a pressurized hot water treatment procedure in which 200 g of untreated soot and 3 L of water same as the filler 210 were placed in a pressure vessel and steam-pressed in an autoclave at 125 ° C. for 60 minutes. . The filling amount of the filler 220 was 130 g which is the same as that of the filler 210.
As a procedure of ultrasonic treatment, the filler 230 is charged with 200 g of untreated soot and 3 L of water, which are the same as those of the filler 210, in an ultrasonic cleaner (Fine FU-13H) manufactured by Tokyo Glass Instrument Co., Ltd. Minutes were used after sonication. The filling amount of the filler 230 was 130 g which is the same as that of the filler 210.

The soot that has undergone these treatments is filled as a biomass carrier, and is an upward flow type similar to that of the wastewater treatment apparatus 1 in the process of the above-described embodiment (FIG. 2). A small denitrification reaction tank made of acrylic having a thickness of 23.5 cm (effective volume is 1.18 L) was filled. The filling rate at this time was 17%.
About these small denitrification reaction tanks, the artificial waste water which made the total nitrogen 40 mg / L with the same sewage sludge was made into a to-be-processed water, the residence time was adjusted to 8 hours, and it was operated for 3 months.
Thereafter, the difference in the dry weight of the filler after 3 months was determined from the dry weight of the charged filler.

FIG. 5 is a graph showing the solubilization rate of the filler subjected to each treatment for 3 months in the treatment experiment system. The solubilization rate (%) was calculated by the following formula (1):

Solubilization rate (%) = [(Dry weight of input filler-Dry weight of filler after three months) × 100] / Dry weight of input filler ...... Equation (1)

According to FIG. 5, by performing alkali treatment, decomposition of the filler 200 is promoted, solubilization rate is increased, and an easily decomposable organic substance or phosphate phosphorus that is a nutrient source of microorganisms is effectively supplied. It can be seen that

(Comparison between upflow and crossflow reactors)
Next, referring to FIG. 6 and FIG. 7, the results of experiments comparing denitrification effects will be described as Example 2 using an upflow type reaction tank and a cross flow type reaction tank.
FIG. 6 is a schematic plan view illustrating the configuration of the apparatus according to the second embodiment.
The wastewater treatment apparatus 1 and the wastewater treatment apparatus 2 have an upward flow configuration in which the denitrification reaction tank 100 is disposed upward with respect to gravity, similarly to the wastewater treatment apparatus 1 according to the above-described embodiment. . In Example 2, the wastewater treatment apparatus 1 was directly filled with the filler 200 that had been subjected to alkali treatment without using the column 20. In addition, the wastewater treatment apparatus 2 has an upflow configuration similar to that of the wastewater treatment apparatus 1 and is directly filled with the untreated filler 210.
The waste water treatment device 3 and the waste water treatment device 4 have a configuration of a cross-flow type waste water treatment device arranged in a horizontal direction. The denitrification reaction tank 101 of the wastewater treatment device 3 and the wastewater treatment device 4 is configured to seal both end surfaces in the longitudinal direction of the wastewater treatment device 1, and to include a treated water input valve 160 on the upstream end surface. A treated water acquisition valve 180 and a sludge extraction valve 190 are provided on the end face of the nozzle. The denitrification reaction tank 101 of the wastewater treatment device 3 and the wastewater treatment device 4 has air holes (not shown). Other than that, it is exactly the same as the wastewater treatment apparatus 1 and the wastewater treatment apparatus 2, the wastewater treatment apparatus 3 is directly filled with the filler 200, and the wastewater treatment apparatus 4 is directly filled with the filler 210.
The filling rate of the filler 200 or the filler 210 of each waste water treatment apparatus 1 to waste water treatment apparatus 4 was 20%.

In Example 2, the water to be treated is provided in the water tank 40 to be treated as in Example 1 described above, and the water line 60 to be treated is connected to each of the waste water treatment apparatuses 1 to 4 by a general pump 50. The average total nitrogen, nitrite ion, nitrate ion, ammonium ion, etc. of the water to be treated and the treated water are treated with an ultraviolet-visible spectrophotometer (UV-2450) manufactured by Shimadzu or an ion chromatograph manufactured by Shimadzu. (Prominence HIC-SP).
The experiment was carried out for 3 months with the residence time adjusted to 24 hours, and the concentration of each inorganic nitrogen in each wastewater treatment device 1 and wastewater treatment device 2 was measured.

In FIG. 7, the experimental result of Example 2 is shown. FIG. 7 shows that the raw water of wastewater treated with nitrification solution (Akita Prefectural Environmental Conservation Center / Water Treatment Facility, Daisen City) for landfill leachate was treated water for the number of specimens n = 21. The measurement results of denitrification in the wastewater treatment apparatus 1 to the wastewater treatment apparatus 4 are shown respectively. Among each item, TN shows the average of the total average nitrogen (Total Nitrogen), the minimum value (min), and the maximum value (max). The removal rate (%) indicates the removal rate of average total nitrogen. Further, nitrification been nitrate nitrogen NO ₃ -N, nitrite nitrogen NO ₂ -N, for NH ₄ -N ammonium nitrogen, show the respective measurement results.
As a result, the wastewater treatment apparatus 1 using the filler 200 subjected to the alkali treatment showed the highest total nitrogen removal ability, that is, the highest biological denitrification ability. Further, the upflow-type wastewater treatment device 1 and the wastewater treatment device 2 show higher denitrification capability than the crossflow-type wastewater treatment device 3 and the wastewater treatment device 4, and the nitrite / nitrate nitrogen It was efficient for removal.
As described above, the denitrification can be effectively performed by using the upward flow type reaction tank in which the water to be treated is flowed from the bottom to the top using the filler 200 subjected to the alkali treatment.

(Effect of filling rate on denitrification)
Next, referring to FIG. 8, the results of experiments on the influence of the filling rate on denitrification will be described as Example 3.
In the same manner as in Example 2 described above, the alkali-treated soot is used as the filler 200, and the wastewater treatment apparatus 1 is directly filled so that the filling rate becomes 20%, 25%, and 40%, respectively. The effect of filling rate on denitrification was examined by flowing treated water.
The experiment was conducted after using the nitrification solution (Akita Prefectural Environmental Conservation Center / Water Treatment Facility, Daisen City), which is the oxidation treatment water of actual landfill leachate, to stabilize after 3 days from installation. The residence time was adjusted to 24 hours, and the average total nitrogen concentration before and after the treatment was measured.
As shown in FIG. 8, it can be seen that the higher the filling rate, the higher the removal rate of total nitrogen, which affects the denitrification efficiency. For this reason, in order to ensure an appropriate filling rate that can provide a stable denitrification ability against fluctuations in water temperature and water quality, in addition to the alkali treatment of the filler, pressure molding for increasing the filling rate is effective. .

(Comparison between the wastewater treatment apparatus 1 of this embodiment and the treatment apparatus of the methanol denitrification method)
Next, with reference to FIG. 9 and FIG. 10, the results of experiments on comparison with the methanol denitrification method will be described as Example 4.
As Example 4, as in the case of the cocoon subjected to the alkali treatment in Example 1 described above, 40 kg of dried potato stalks were cut to 5 to 10 cm, and 2 to 40 ° C. 0.5 M sodium hydroxide aqueous solution. After immersing for 3 hours to perform delignification treatment, it was washed with water until the cleaning solution had a pH of 8.0 or less. 0.9 kg of this lignin treated paddle is used as a filler 200, and 5 mm diameter holes are placed in a column (diameter 77 mm, height 772 mm) at intervals of 10 mm and pressed to 250 g / cm ³ with a compression molding machine. Column 20 was prepared. 33 columns 20 filled with the soot were arranged in two columns in the upper and lower rows in a cylindrical denitrification reaction tank 100 having a diameter of 40 cm and a height of 160 cm to constitute an upflow type wastewater treatment apparatus 1. By arranging 33 columns 20 in the denitrification reaction tank 100, the filling rate of the denitrification reaction tank 100 is 40% (v / v).
In addition, for comparison, after denitrification treatment using a landfill leachate water treatment facility (Akita Prefectural Environmental Conservation Center / Water Treatment Facility, manufactured by Kurimoto Steel Works), to which methanol is added, similar to Conventional Technology 1, Treated water was collected twice a week for water quality analysis.
The comparative experiment was conducted for 60 days, and the average total nitrogen (mg / L) of water to be treated and treated water was measured. The total nitrogen was measured by an ultraviolet absorption spectrophotometry using an ultraviolet-visible spectrophotometer (UV-2450) manufactured by Shimadzu Corporation.
Moreover, NO ₂ —N and NO ₃ —N were measured with an ion chromatograph manufactured by Shimadzu Corporation, and the oxidation-reduction potential was measured with an ORP meter manufactured by Yamagata Toa DKK.

In the wastewater treatment apparatus 1 of Example 4 and the apparatus that performs the methanol denitrification method, as in Example 3, the nitrification water of landfill leachate having an average total nitrogen concentration of 32.5 mg / L is treated water. As a result, the treatment performance was confirmed by an experiment for about 60 days while continuously flowing so that the contact residence time was 24 hours.
FIG. 9 shows the results of this experiment. The total nitrogen concentration of the treated water by the wastewater treatment apparatus 1 is 2.5 mg / L on average (minimum 0.4 mg / L to maximum 6.0 mg / L), which is lower than the conventional methanol denitrification method, and an average denitrification rate of 98 % Processing performance was obtained.
FIG. 10 shows the relationship between the concentration of nitrous acid / nitric nitrogen (NO _{2 + 3-} N) and the oxidation-reduction potential (ORP) of the treated water of Example 4 and the wastewater treatment apparatus 1 of Example 2. The horizontal axis is the oxidation-reduction potential measured immediately after collecting the treated water with an ORP meter manufactured by Yamagata Toa DKK, and the vertical axis is nitrous acid / nitric nitrogen (NO _{2 + 3} −) measured by Shimadzu ion chromatograph. N) concentration (mg / L).
Thus, the progress of denitrification can be grasped by measuring the change in the oxidation-reduction potential. Moreover, optimal denitrification can be performed by adjusting the contact residence time with reference to a predetermined oxidation-reduction potential.

(Comparison with Tomomi Tomoe)
Next, with reference to FIG. 11 to FIG. 14, as a fifth example, the results of a comparative experiment using the same herbaceous rice husk and rice husk as a biomass carrier will be described.

The wastewater treatment apparatus 5 of FIG. 11 is provided in the denitrification reaction tank 102 in which small acrylic denitrification reaction tanks having an inner diameter of 7.8 cm, a height of 25 cm, and an effective volume of 1.2 L are arranged in three stages. In the same manner as above, the filler 200, which is a soot that has been cut into a size of 5 to 10 cm and alkali-treated, is directly filled in each small denitrification reaction tank so that a filling rate of 45% (v / v) is obtained. did. The denitrification reaction tank 102 includes treated water acquisition valves 182, 181 and 180 whose flow rates are adjusted so that the contact residence time (HRT) of the treated water passing therethrough is 4, 8, and 12 hours, respectively. A partition 111 is provided. Others are the same as that of the small denitrification reaction tank of Example 1. In this way, a wastewater treatment apparatus 5 was created.
The waste water treatment apparatus 6 is configured in the same manner as in Examples 1 and 2, in which the untreated soot filler 220 is filled at the same filling rate as in the waste water treatment apparatus 5 and arranged in the denitrification reaction tank 102. It is.
The wastewater treatment apparatus 7 fills each small denitrification reactor with the filler 240 obtained by alkali-treating rice husk in the same manner as the straw so that the filling rate becomes 180%, and the denitrification rate becomes 33% (v / v). The configuration is arranged in the reaction vessel 102.
The wastewater treatment device 8 has a configuration in which a filler 250, which is an untreated rice husk, is filled at the same filling rate as in the wastewater treatment device 7 and disposed in the denitrification reaction tank 102.
The above four wastewater treatment apparatuses 5, 6, 7, and 8 were created, and a continuous experiment was performed as an upward flow type in which water to be treated was introduced from below. Specifically, potassium nitrate was added to nitrification / denitrification treated water (Akita Prefectural Environmental Conservation Center / Water Treatment Facility, Daisen City) in actual landfill leachate so that the total nitrogen concentration was 30 mg / L. Further, potassium dihydrogen phosphate was added so as to have a nitrogen / phosphorus ratio of 0.05 and used as water to be treated. The flow rate was adjusted, and continuous operation was performed at room temperature of 20 ° C. for 80 days.

FIG. 12 is a diagram showing the results of Example 5. The wastewater treatment apparatus 5 filled with the filler 200 that was subjected to alkali treatment and the wastewater treatment apparatus 7 filled with the filler 240 that was subjected to alkali treatment showed high denitrification efficiency.
On the other hand, the wastewater treatment apparatus 6 filled with the filler 210 as untreated soot and the wastewater treatment apparatus 8 filled with the filler 250 as untreated rice husk have denitrification efficiency of alkali treatment. It was low compared to.
In the case of the waste water treatment device 7 filled with the filler 240, which is an alkali-treated rice husk, the average total nitrogen concentration of treated water is 2.2 mg / L and the average removal rate is 92 at a contact residence time (HRT) of 12 hours. %Met.
Further, in the case of the wastewater treatment device 5 filled with the filler 200 which is an alkali treatment soot, the average total nitrogen concentration of the treated water was 1.7 mg / L, and the average removal rate was 94%.

FIG. 13 is a graph showing the concentration of nitrous acid and nitrate nitrogen in the water to be treated (raw water) and the treated water in the wastewater treatment apparatus 5 filled with the alkali treated soot. The horizontal axis indicates the number of days elapsed, and the vertical axis indicates NO2 _{+ 3-} N (mg / L). Dotted lines indicate environmental standards.
FIG. 14 is a graph showing changes over time in the water to be treated (raw water) and the concentration of nitrous acid / nitric nitrogen in the treated water in the wastewater treatment apparatus 7 filled with the rice husk subjected to the alkali treatment. The horizontal axis indicates the number of days elapsed, and the vertical axis indicates NO2 _{+ 3-} N (mg / L). Dotted lines indicate environmental standards.
As described above, the wastewater treatment apparatuses 5 and 7 filled with the soot or rice husk subjected to the alkali treatment can remove the nitrous acid / nitric nitrogen concentration to below the environmental standard for 80 days in the proper contact residence time. In addition, stable denitrification ability was shown.

  Note that the configuration and operation of the above-described embodiment are examples, and it is needless to say that the configuration and operation can be appropriately changed and executed without departing from the gist of the present invention.

  INDUSTRIAL APPLICATION Since this invention can provide the wastewater treatment apparatus and wastewater treatment method which remove nitrous acid and nitrate nitrogen efficiently using herbaceous biomass cheaply, it is industrially applicable.

1, 2, 3, 4, 5, 6, 7, 8 Waste water treatment apparatus 20 Column 40 Water to be treated tank 50 Pump 60 Water to be treated 100, 101, 102 Denitrification reaction tank 110, 111 Partition 160 Water to be treated input valve 180, 181, 182 Treated water acquisition valve 190 Sludge extraction valve 200, 210, 220, 230, 240, 250 Filler

Claims (12)

A column having a water permeability and filled with herbaceous biomass that has been delignified with alkali is arranged in the vertical direction, and is equipped with a denitrification reaction tank in which water to be treated is supplied upward from the bottom. A featured wastewater treatment system. The herbaceous biomass is
The wastewater treatment apparatus according to claim 1, wherein the wastewater treatment apparatus is compressed and pressure-molded to an appropriate filling rate with respect to fluctuations in water temperature and water quality. The wastewater treatment apparatus according to claim 1 or 2, wherein the herbaceous biomass is Phragmites. The waste water treatment apparatus according to claim 3, wherein a packing rate of the metal in the column is 25% to 65%. The wastewater treatment apparatus according to claim 1 or 2, wherein the herbaceous biomass is rice husk. The waste water treatment apparatus according to claim 5, wherein a packing rate of the rice husk into the column is 15% to 45%. The wastewater treatment apparatus according to any one of claims 1 to 6, wherein the column is replaced when an oxidation-reduction potential accompanying denitrification changes at a predetermined voltage or higher. The waste water treatment apparatus according to claim 7, wherein an appropriate contact residence time of the treated water is adjusted by the oxidation-reduction potential. Packed with herbaceous biomass delignified with alkali,
A column for a wastewater treatment apparatus, wherein the herbaceous biomass is compressed and pressure-molded to an appropriate filling rate against fluctuations in water temperature and water quality. A wastewater treatment method comprising: denitrifying a herbaceous biomass that has been delignified with an alkali by bringing it into contact with water to be treated as a microorganism carrier. The wastewater treatment method according to claim 9, wherein the herbaceous biomass is Phragmites. The wastewater treatment method according to claim 10, wherein the water to be treated is waste landfill leachate.

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