JP4972817B2 - Anaerobic treatment method for organic wastewater - Google Patents

Description

【００３４】
表１より次のことが明らかである。
【００３５】
ＮａＣｌの添加量が１ｍＭ以上、即ち、Ｋ^＋に対し、モル比で０．０２倍以上のＮａを添加した場合には、活性を増大させる効果が認められた。しかし、ＮａＣｌの添加量が２０ｍＭ以上では活性は低下傾向にあり、添加量が５０ｍＭを超えると活性は０．４ｇ−ＣＯＤ_Ｃｒ／ｇ−ＶＳＳ／ｄａｙに達しなかった。
【００３６】
［試験２］
実施例８，９、比較例４，５
以下に示す性状の合成排水を図２で示すフローで処理した。
【００３７】
ただし、実施例８及び９では原水にＮａＣｌを５８５ｍｇ／Ｌ（０．０１Ｍ）添加し、比較例４，５では原水にＮａＣｌを添加せずに処理した。
【００３８】
［合成排水性状］
エタノール ：１００００ｍｇ／Ｌ
酵母エキス ：５００ｍｇ／Ｌ
ＮＨ_４−Ｎ ：３００ｍｇ／Ｌ（ＮＨ_４Ｃｌとして１１７０ｍｇ／Ｌ）
ＰＯ_４−Ｐ ：５０ｍｇ／Ｌ（ＫＨ_２ＰＯ_４として２２０ｍｇ／Ｌ）
ＫＣｌ ：３７２５ｍｇ／Ｌ（Ｋ^＋として０．０５Ｍ）
ｐＨ ：７．５
各槽の仕様及び処理条件は以下の通りであり、ＵＡＳＢ槽５の処理水は原水量の３倍を酸発酵槽４に循環した。また、ＵＡＳＢ槽５では槽内の上昇流速を０．５ｍ／ｈｒに維持するために自己循環を行った。
【００３９】
嫌気性処理の後処理の好気性処理としては循環法による硝化・脱窒処理を行った。硝化槽７の処理水は原水量の５倍を脱窒槽６に循環し、沈殿槽８で分離した汚泥は脱窒槽６へ返送した。返送汚泥量は原水量の５倍とした。
【００４０】
［酸醗酵槽］
容量 ：２Ｌ
温度 ：３０〜３５℃
内部をポンプで攪拌し、メタン菌の活性維持のための微量金属としてＦｅ^２＋を１０ｍｇ／Ｌ、Ｃｏ^２＋、Ｎｉ^２＋をそれぞれ０．１ｍｇ／Ｌ添加した。
【００４１】
［ＵＡＳＢ槽］
内径 ：１０ｃｍ
高さ ：１２０ｃｍ
有効容量 ：８．５Ｌ
内部にビール工場排水を処理している実装置から採取したグラニュール汚泥４Ｌを汚泥濃度がＶＳＳとして５００００ｍｇ／Ｌとなるように充填した。
【００４２】
［脱窒槽］
容量 ：３Ｌ
温度 ：室温（約２５℃）
［硝化槽］
容量 ：４Ｌ
温度 ：室温（約２５℃）
［沈殿槽］
容量 ：２Ｌ
通水条件を表２に示すように変えて２週間処理し、後半の１週間での処理水質の平均値を表３に示した。
【００４３】
【表２】

【００４４】
【表３】

【００４５】
表３から次のことが明らかである。
【００４６】
負荷が高い場合、低い場合のいずれの場合も原水にＮａＣｌを添加した方がＮａＣｌを添加しない場合に比して嫌気、好気とも処理が良好であった。特に、高負荷での処理を行う場合において、ＮａＣｌを添加する場合としない場合との差が顕著であった。
【００４７】
また、実施例８と比較例４は嫌気処理水の水質は同程度であるにも関わらず好気処理水の水質は実施例８が比較例４より良好で、ＮａＣｌの添加が後段の好気性処理の処理効率を向上させることが示された。
【００４８】
［試験３］
参考例１
試験１で用いた合成排水のＫＣｌの添加量を変えて異なったＫ濃度とし、それぞれの濃度でアンモニアを添加した場合と添加しない場合とでメタン生成活性の違いを比較した。実験は、Ｋ濃度及びＮＨ_４の有無以外は試験１と同様にし、アンモニアを添加する場合のＮＨ_４濃度は０．０２５Ｍとした。
【００４９】
結果は、表４に示す通りであった。
【００５０】
【表４】

【００５１】
表４から以下のことが明らかである。
【００５２】
ＮＨ_４が共存する場合もしない場合もＫ濃度が高くなるに従ってメタン生成活性は低下する。また、活性の低下は、ＮＨ_４が共存する場合の方が、ＮＨ_４が共存しない場合より著しく、特にＫ濃度が０.０３モル以上存在する場合、ＮＨ_４による阻害は顕著となった。
【００５３】
［試験４］
参考例２
参考例１において、Ｋ濃度を０．０５Ｍとし、ＮＨ_４の添加濃度を変えてメタン活性の違いを比較した。結果は表５に示す通りであり、ＮＨ_４濃度が０．０２Ｍを超えると活性が急激に低下した。
【００５４】
【表５】

【００５５】
【発明の効果】
以上詳述した通り、本発明の有機性排水の嫌気性処理方法によれは、ＮＨ_４ ^＋共存下でのＫ^＋による微生物阻害を防止して、有機性排水の嫌気性処理を安定且つ効率的に行って、高水質の処理水を得ることができる。
【図面の簡単な説明】
【図１】本発明の有機性排水の嫌気性処理方法の実施の形態を示す系統図である。
【図２】実施例８，９及び比較例４，５で用いた試験装置を示す系統図である。
【符号の説明】
１，４ 酸発酵槽
２ メタン発酵槽
３ 曝気槽
５ ＵＡＳＢ槽
６ 脱窒槽
７ 硝化槽
８ 沈殿槽[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an anaerobic treatment method for organic wastewater, and more particularly to a method for anaerobically treating organic wastewater containing potassium ions at a high concentration in a stable and efficient manner.
[0002]
[Prior art]
Anaerobic treatment methods are applied to the treatment of industrial wastewater such as food wastewater.
[0003]
Anaerobic treatment consists of an acid fermentation process that converts organic substances in wastewater into organic acids by acid producing bacteria under anaerobic conditions, and a methane fermentation process that decomposes the generated organic acids into methane by methanogenic bacteria under anaerobic conditions. It consists of two steps. This anaerobic treatment apparatus includes a two-phase type in which the acid fermentation process and the methane fermentation process are performed in separate tanks, and a single-phase type in which these are performed in a single tank.
[0004]
The two-phase anaerobic treatment device is mainly composed of an acid fermenter and a methane fermenter at the subsequent stage. In some cases, part of the treated water from the methane fermenter is returned to the acid fermenter, and the rest goes out of the system. It is discharged and further advanced processing is performed by an aerobic processing device or the like.
[0005]
On the other hand, in the one-phase type anaerobic treatment apparatus, a circulation line for extracting the liquid in the anaerobic tank and returning it to the anaerobic tank is provided to circulate the treated water.
[0006]
The anaerobic treatment method has advantages such as less generation of surplus sludge and less power consumption compared to aerobic treatment such as activated sludge, and the biogas generated in the anaerobic treatment uses 50 methane. Since about 90% is contained, it has the outstanding feature that it can be effectively used as fuel for boilers and the like.
[0007]
As the reaction format of the anaerobic treatment, a high load type such as UASB, EGSB, fluidized bed, fixed bed or the like is preferable from the viewpoint of treatment efficiency, depending on the type of microorganisms. Among them, the UASB method, that is, the upflow anaerobic sludge blanket process, is a method in which methanogenic bacteria are granulated into self-granulating or core substances without using an adherent carrier. This is a method in which raw water is passed in an upward flow through a reaction tank in which a sludge bed (sludge blanket) of granulated sludge (granule) is formed, and EGSB method, that is, an anaerobic expansion granule bed The method (Expanded Granular Sludge Bed Process) is a method in which water is flowed upward at a high flow rate into a reaction tank similarly formed with a sludge blanket, and these are all treated in the reaction tank at 15000 to 70000 mg-VSS / L. organic since it is possible to retain high levels of microorganisms degree at high-load processing to obtain _{0.4~1.5kg-COD Cr / kg-VSS} / day about high methane activity It has the advantage that the organic matter in the waste water can be efficiently decomposed and removed.
[0008]
By the way, monovalent cations such as potassium ions (K ⁺ ) and sodium ions (Na ⁺ ) have an inhibitory effect on anaerobic treatment and aerobic biological treatment when they are present at high concentrations in waste water. It is known that there is. In particular, it is known that methanogens and nitrifying bacteria, which are autotrophic bacteria involved in microorganisms such as anaerobic treatment and nitrification / denitrification, are more sensitive to these cations than normal other vegetative bacteria. It has been. In general, the inhibitory concentration range of K ⁺ , Na ^{+ and the} like is 0.1 to 0.2 M or more, and 0.1 M or less has almost no influence.
[0009]
[Problems to be solved by the invention]
However, as a result of various studies on the anaerobic treatment of the organic waste water and the aerobic treatment after the anaerobic treatment, the present inventors have found that in high load type anaerobic treatment such as UASB and EGSB using granule, ⁺ conventionally, inhibition even at much lower 0.025M about than the concentration that is to occur, ammonium ion (NH 4 ^₊₎ has found that inhibiting the coexisting least about 1/2 mole of K ⁺ is expressed.
[0010]
The present invention provides a method for preventing microbial inhibition by K ⁺ in the presence of NH ₄ ⁺ and obtaining high-quality treated water by performing anaerobic treatment of organic wastewater stably and efficiently. The purpose is to do.
[0011]
[Means for Solving the Problems]
Anaerobic treatment method of an organic waste water of the present invention comprises a potassium nitrogen compound, ^{K +} concentration is 0.025M~0.05M, _NH ^{4 +} concentration is equal to or greater than 1/2 times by mole of ^{K +} concentration In the method for treating organic wastewater by anaerobic treatment using granules, the amount of sodium ion relative to potassium ion in the organic wastewater is 1/50 to 1 mol times , and sodium in the organic wastewater An anaerobic treatment is performed after adding a sodium ion source to the organic waste water so that the ion concentration becomes 1 to 50 mM .
[0012]
That is, the present inventors have further result of extensive studies to solve the problems of microbial inhibition by K ⁺ in the anaerobic treatment, by the coexistence of 1 / 50-1 mol per mol of Na ⁺ with respect to K ⁺ The ability of K ⁺ to mitigate microbial inhibition and to perform anaerobic treatment stably and efficiently, and the effect of Na ⁺ is not only for anaerobic treatment but also for removal of BOD after anaerobic treatment. The present invention has been completed by finding that it is also effective for the aerobic treatment step and the nitrification denitrification step for denitrification.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an anaerobic treatment method for organic waste water according to the present invention will be described below in detail with reference to the drawings.
[0014]
FIG. 1 is a system diagram showing an embodiment of the organic wastewater anaerobic treatment method of the present invention.
[0015]
The method shown in the figure is a method for performing an aerobic treatment after performing a two-phase anaerobic process in which an acid fermentation process and a methane fermentation process are performed in separate tanks, and the raw water (organic wastewater) is acid fermentation. Anaerobic treatment is performed in the tank 1 and the methane fermentation tank 2. A part of the treated water in the methane fermentation tank 2 is circulated to the acid fermentation tank 1, the remainder is aerobically treated in the aeration tank 3, and the treated water is discharged out of the system.
[0016]
The treatment in the acid fermentation tank 1 may be performed with stirring using a suspended dispersion sludge, or may be a tank that also serves as a precipitation separation tank for SS without stirring. The treatment conditions for the acid fermenter 1 are preferably as follows.
[0017]
[Acid fermenter treatment conditions]
pH: 4-8
Temperature: 25-40 ° C
Residence time: 1 to 48 hr
The methane fermentation tank 2 is preferably a high-load type such as UASB or EGS B , particularly a UASB or EGSB tank capable of high-load treatment using granular sludge. The treatment conditions of the methane fermentation tank 2 are as follows: It is preferable to do this.
[0018]
[Methane fermentation tank treatment conditions]
pH: 6 to 8.5
Temperature: 25-40 ° C
Residence time: 2 to 48 hr
Organic load: 4 to 30 kg-COD _Cr / m ³ / day
A part of the treated water in the methane fermentation tank 2 is returned to the acid fermentation tank 1. That is, in the acid fermenter 1, the pH is usually lowered due to the generation of acid, whereas in the methane fermenter 2, the pH is increased by the treatment, so that a part of the treated water in the methane fermenter 2 is circulated to the acid fermenter 1. Although pH adjustment can be performed by doing this, this circulation is not necessarily required and the whole amount of treated water in the methane fermentation tank 2 may be supplied to the aeration tank 3.
[0019]
The aeration tank 3 is a tank for performing aerobic treatment with activated sludge to remove BOD, and the following treatment conditions are employed.
[0020]
[Aeration tank treatment conditions]
pH: 5-7
Temperature: 15-35 ° C
Residence time: 4 to 48 hours
Organic load: 0.5 to ³ kg-COD _Cr / m ³ / day
In the present invention, in such treatment, the Na ⁺ source is added so that the Na ⁺ concentration is 1/50 to 1 mol times the concentration of K ^{+ in} the raw water to be anaerobically treated. As this Na ⁺ source, NaOH, NaCl, Na ₂ CO ₃ or the like can be used.
[0021]
Microbial inhibition by K ^{+ in the} presence of NH ₄ ^{+ is} under the condition where ammonia contained in raw water or ammonia produced by decomposition of organic nitrogen (protein) by anaerobic treatment coexists with more than 1/2 mol of K ⁺ . for methane, the fermentation inhibitor, it is sufficient Na ⁺ source is added so Na ⁺ as described above is present in the methane fermentation system, the addition point in Fig. 1, the inlet (circled acid fermentation tank 1 1), the acid fermentation tank 1 (2 circled number), methane fermentation tank 2 inlet (3 circled) may be either methane fermentation tank 3 (4 circled).
[0022]
When the Na ⁺ concentration in the methane fermentation system is less than 1/50 mol times the K ⁺ concentration, microbial inhibition cannot be sufficiently prevented. If the Na ⁺ concentration is more than an equimolar multiple of the K ⁺ concentration, Na ⁺ ions may inhibit the activity of anaerobic microorganisms.
[0023]
Therefore, the Na ⁺ source is added so that the Na ⁺ concentration is 1/50 to 1 mol times, preferably 1/25 to 1/5 mol times the K ⁺ concentration.
[0024]
The addition of such Na ⁺ source prevents microbial inhibition in the anaerobic treatment system, and anaerobic treatment of the anaerobic treated water that has sufficiently decomposed organic matter by the anaerobic treatment is high even in the aerobic treatment. BOD removal efficiency can be obtained.
[0025]
The method shown in FIG. 1 is an example of the embodiment of the organic waste water anaerobic treatment method of the present invention, and the present invention is not limited to the illustrated method. For example, a decarboxylation tank may be provided between the acid fermentation tank 1 and the methane fermentation tank 2 to perform a decarboxylation treatment, or a pH adjustment tank may be provided between the acid generation tank 1 and the methane fermentation tank 2. good.
[0026]
In addition, the anaerobic treatment is not limited to the illustrated two-phase method, and may be a one-phase method in which acid fermentation and methane fermentation are performed in the same tank. Furthermore, in addition to aerobic treatment of anaerobic treated water, nitrogen removal may be performed by a combination of denitrification (anaerobic) and nitrification (aerobic).
[0027]
Such a method of the present invention has a K ⁺ concentration of 0.025 M (975 mg / L) or more, contains nitrogen that is converted to ammonia nitrogen by anaerobic treatment, and has an NH ₄ ⁺ concentration of K at the time of methane fermentation treatment. ⁺ 1/2 mole times or more of concentration, Na ⁺ concentration is significantly lower than the ^{K +} concentration, for example, is particularly effective in the treatment of certain such organic waste water below 0.001 M.
[0028]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples, Comparative Examples and Reference Examples.
[0029]
[Test 1]
Examples 1-7, Comparative Examples 1-3
Acetic acid and ammonia were added to city water to make acetic acid concentration 300mg / L, ammonia concentration 0.025M, adjusted to pH 7 with KOH, and further using KCI to make K concentration 0.05M The experiment was conducted.
[0030]
The above synthetic waste water is brought into contact with granule sludge added with about 1 g of VSS in a 500 mL Erlenmeyer flask as VSS, treated in an isothermal water bath at 35 ° C. while anaerobically stirring, and the amount of NaCl added is changed to generate gas. The speed was examined. Granule sludge was collected from a UASB tank for comprehensive wastewater treatment at a beer factory, and the sludge concentration was about 50000 mg / L as VSS.
[0031]
The gas generation rate per VSS was determined from the gas generation rate and the amount of sludge in the flask, and the acetic acid-assimilating methane generation activity was compared.
[0032]
Table 1 shows the NaCl addition amount (Na concentration) and the methanogenic activity in Examples 1 to 7 and Comparative Examples 1 to 3.
[0033]
[Table 1]

[0034]
From Table 1, the following is clear.
[0035]
When the addition amount of NaCl was 1 mM or more, that is, 0.02 times or more of Na in terms of molar ratio with respect to K ⁺ , an effect of increasing the activity was observed. However, the amount of NaCl is 20mM or more activity is on a downward trend, active when the amount exceeds 50mM did not reach _{0.4g-COD Cr / g-VSS} / day.
[0036]
[Test 2]
Examples 8 and 9, Comparative Examples 4 and 5
The synthetic wastewater having the following properties was treated by the flow shown in FIG.
[0037]
However, in Examples 8 and 9, 585 mg / L (0.01 M) of NaCl was added to the raw water, and in Comparative Examples 4 and 5, the raw water was treated without adding NaCl.
[0038]
[Synthetic drainage properties]
Ethanol: 10000 mg / L
Yeast extract: 500 mg / L
NH ₄ —N: 300 mg / L (1170 mg / L as NH ₄ Cl)
PO ₄ -P: 50 mg / L (220 mg / L as KH ₂ PO ₄ )
KCl: 3725 mg / L (0.05 M as K ⁺ )
pH: 7.5
The specifications and treatment conditions of each tank were as follows, and the treated water in the UASB tank 5 was circulated to the acid fermentation tank 4 by 3 times the amount of raw water. Further, in the UASB tank 5, self-circulation was performed in order to maintain the rising flow velocity in the tank at 0.5 m / hr.
[0039]
As an aerobic treatment after anaerobic treatment, nitrification and denitrification treatment was performed by a circulation method. The treated water in the nitrification tank 7 was circulated to the denitrification tank 6 five times the amount of the raw water, and the sludge separated in the precipitation tank 8 was returned to the denitrification tank 6. The amount of returned sludge was 5 times the amount of raw water.
[0040]
[Acid fermentation tank]
Capacity: 2L
Temperature: 30-35 ° C
The inside was stirred with a pump, and Fe ²⁺ was added at 10 mg / L, and Co ²⁺ and Ni ²⁺ were added at 0.1 mg / L as trace metals for maintaining the activity of methane bacteria.
[0041]
[UASB tank]
Inner diameter: 10 cm
Height: 120cm
Effective capacity: 8.5L
Granule sludge 4L collected from an actual apparatus treating beer factory waste water was filled so that the sludge concentration would be 50000 mg / L as VSS.
[0042]
[Denitrification tank]
Capacity: 3L
Temperature: Room temperature (about 25 ° C)
[Nitrification tank]
Capacity: 4L
Temperature: Room temperature (about 25 ° C)
[Settling tank]
Capacity: 2L
The water flow conditions were changed as shown in Table 2, and the treatment was conducted for 2 weeks. The average value of the treated water quality in the latter half of the week was shown in Table 3.
[0043]
[Table 2]

[0044]
[Table 3]

[0045]
From Table 3, the following is clear.
[0046]
In both cases of high load and low load, treatment with both anaerobic and aerobic treatment was better when NaCl was added to the raw water than when NaCl was not added. In particular, when processing with a high load is performed, the difference between the case where NaCl is added and the case where NaCl is not added is remarkable.
[0047]
Further, in Example 8 and Comparative Example 4, although the quality of the anaerobic treated water is similar, the quality of the aerobic treated water in Example 8 is better than that in Comparative Example 4, and the addition of NaCl is the latter aerobic. It has been shown to improve the processing efficiency of the process.
[0048]
[Test 3]
Reference example 1
The amount of KCl added to the synthetic waste water used in Test 1 was varied to obtain different K concentrations, and the difference in methane production activity was compared between when ammonia was added and when it was not added. The experiment was the same as in Test 1 except for the K concentration and the presence or absence of NH ₄ , and the NH ₄ concentration when adding ammonia was 0.025 M.
[0049]
The results were as shown in Table 4.
[0050]
[Table 4]

[0051]
From Table 4, the following is clear.
[0052]
Whether NH ₄ coexists or not, the methanogenic activity decreases as the K concentration increases. A decrease in the activity is better when the NH ₄ coexist significantly than when NH ₄ does not coexist, particularly when K concentration occurs more than 0.03 mol, inhibition by NH ₄ became prominent.
[0053]
[Test 4]
Reference example 2
In Reference Example 1, the difference in methane activity was compared by changing the concentration of K ₄ to 0.05 M and changing the concentration of NH ₄ added. The results are as shown in Table 5. When the NH ₄ concentration exceeded 0.02M, the activity decreased rapidly.
[0054]
[Table 5]

[0055]
【Effect of the invention】
As described above in detail, according to the method for anaerobic treatment of organic wastewater of the present invention, microorganisms are prevented from being inhibited by K ⁺ in the presence of NH ₄ ⁺ , so that the anaerobic treatment of organic wastewater is stable and efficient. It is possible to obtain high-quality treated water.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of the organic waste water anaerobic treatment method of the present invention.
FIG. 2 is a system diagram showing a test apparatus used in Examples 8 and 9 and Comparative Examples 4 and 5;
[Explanation of symbols]
1,4 Acid fermentation tank 2 Methane fermentation tank 3 Aeration tank 5 UASB tank 6 Denitrification tank 7 Nitrification tank 8 Precipitation tank

Claims (2)

And a potassium ion and a nitrogen compound, ^{K +} concentration is 0.025M~0.05M, _NH ^{4 +} concentration is 1/2 mole times or more of the organic waste water of the ^{K +} concentration, anaerobic treatment with granular In the method of processing in
A sodium ion source in the organic waste water such that the amount of sodium ions relative to potassium ions in the organic waste water is 1/50 to 1 mol times , and the sodium ion concentration of the organic waste water is 1 to 50 mM. An anaerobic treatment method for organic wastewater, characterized by anaerobic treatment after addition of. 2. The method for anaerobic treatment of organic waste water according to claim 1, further comprising aerobic treatment of the anaerobic treated water.

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