JP2004202441A - Dioxin-contaminated water purfication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dioxin-contaminated water purification method which enables the removal of contaminants by using common coagulation equipment and at the same time, separate and remove dioxins at a low cost. <P>SOLUTION: In the dioxin-contaminated water purification method, a metallic coagulant and a radiation-crosslinked body of polyamino acid or a polyamino acid salt are added to dioxin-contaminated water to coagulate and precipitate the dioxins, thereby reducing the dioxin concentration in the contaminated water. As the dioxins can be coagulated and precipitated only by making the metallic coagulant and the radiation-crosslinked body coexist in the contaminated water, dioxin removal treatment can be carried out by the common coagulation equipment without special apparatus or equipment, which realizes low-cost dioxin treatment. As COD components, BOD components, and SS components present in the contaminated water can be coagulated and precipitated by the metallic coagulant and the radiation-crosslinked body, the dioxin removal and normal water purification treatment can be performed at the same time. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００９４】

【００９５】
表１から分かるように、ＰＧ２１をＰＡＣと共に原水に対して処理すると、ダイオキシン類の濃度は６３（ｐｇ／ｌ）から７．７（ｐｇ／ｌ）へと約１／８にまで低下する。これに対し、表２から分かるように、毒性当量では１．１４（ｐｇ−ＴＥＱ／ｌ）から０．０００６５（ｐｇ−ＴＥＱ／ｌ）まで約１／１８００まで急激に低下している。
【００９６】
前述したように、環境中における水質基準は、毒性当量において１（ｐｇ−ＴＥＱ／ｌ）である。原水では１．１４（ｐｇ−ＴＥＱ／ｌ）であるから水質基準をやや超えているが、ＰＧ２１を処理すると０．０００６５（ｐｇ−ＴＥＱ／ｌ）まで低下するから、水質基準を軽くクリアすることが実証された。このように、本発明方法を使用すれば、ダイオキシン処理が簡単に行えることが分かる。
【００９７】
[比較例：ＰＡＣ単独処理]
実施例で用いられたＣＯＤ３００の原水（ダイオキシン汚染水）に対し、金属系凝集剤であるＰＡＣだけを３０ｐｐｍ添加して凝集処理を行った。ＰＧ２１を併用しないときに、ダイオキシン類がどの程度凝集沈殿できるかどうかを試験して、ＰＡＣ２１使用の効果を証明するものである。凝集処理方法とダイオキシン類分析方法は実施例と全く同様にして行われた。
【００９８】
表３には、ダイオキシン類の実測濃度（ｐｇ／ｌ）が原水及びＰＡＣ処理水について示されている。また、表４には、ダイオキシン類の毒性当量（ｐｇ−ＴＥＱ／ｌ）が原水及びＰＡＣ処理水について示されている。
【００９９】

【０１００】

【０１０１】
表３及び表４から分かるように、ＰＡＣ単独処理では、濃度及び毒性当量ともに原水の約７０％程度の値に低減できるだけであることが分かった。本発明者等は各種の金属系凝集剤を単独使用して同様の実験を繰り返したが、金属系凝集剤単独ではダイオキシン類の濃度を５０％以下に下げることは困難であるとの結論に達した。毒性当量は０．７９（ｐｇ−ＴＥＱ／ｌ）であるから、水質基準の１（ｐｇ−ＴＥＱ／ｌ）を僅かにクリアしているが、原水のダイオキシン濃度がかなり高濃度である場合には、水質基準をクリアすることは難しいと思われる。つまり、ＰＡＣ単独では、産業廃水などの高濃度汚染水に対するダイオキシン浄化処理は困難である。
【０１０２】
このように、ダイオキシン汚染水に対しＰＡＣ単独処理では水質基準を満足させることは困難である。しかし、本発明のように、ＰＡＣなどの金属系凝集剤にＰＧ２１などの放射線架橋体を併用添加すれば、ダイオキシン濃度は約１／１０にまで低下し、しかも水質基準の対象となる毒性当量は約１／２０００にまで低減できることが可能になることが分かった。
【０１０３】
以上では、被処理水として飲料用原水、下水及び産業廃水を用いて浄化方法を説明したが、本発明により浄化できる対象物はダイオキシンを含有する水一般である。つまり、この発明は、河川水・湖沼水・地下水・雨水などの飲料用原水、食品加工や発酵工業などにおいて使用される食品排水、池や堀や噴水などの観賞用水、プールなどの水泳用水、都市下水や産業廃水、家庭用排水などの広範囲の水を浄化することができる。
【０１０４】
本発明は上記実施形態や実施例に限定されるものではなく、本発明の技術的思想を逸脱しない範囲における種々の変形例や設計変更もその技術的範囲内に包含されるものであることは云うまでもない。
【０１０５】
【発明の効果】
第１の発明によれば、金属イオンとの共存状態で放射線架橋体が急速に凝集沈殿する際に、水中に溶解しているダイオキシン類を放射線架橋体に吸着して強制的に同時沈殿させることができる。金属系凝集剤と放射線架橋体をダイオキシン汚染水に共存させるだけでよいから、通常の凝集処理設備によりダイオキシン除去処理が可能であり、特別の装置・設備が不要であるから低コストでダイオキシン分離処理が実現できる。また、ダイオキシン類だけでなく、汚染水中に存在するＣＯＤ成分やＢＯＤ成分やＳＳ成分なども金属系凝集剤と放射線架橋体によって凝集沈殿できるから、ダイオキシン類の除去と同時に通常の浄水処理も可能にした画期的な浄化処理方法を提供できる。
【０１０６】
第２の発明によれば、ダイオキシン汚染水に約３ｐｐｍを超えて放射線架橋体を溶解させ、これに金属系凝集剤を介して金属イオンを添加することにより、約３ｐｐｍを超えた過剰分量の放射線架橋体を凝集沈殿させることができ、この放射線架橋体の凝集沈殿によってダイオキシン類を強制沈殿させることができる。この約３ｐｐｍという溶解度の臨界値は本発明者等によって発見されたものであり、比較的高価な放射線架橋体を約３ｐｐｍを超える程度に微量添加するだけでよいから、ダイオキシンの除去処理を低コストで実施できる利点がある。
【０１０７】
第３の発明によれば、放射線架橋体を数ｐｐｍ以上（１〜３ｐｐｍ以上）の濃度の金属系凝集剤と共存させるだけでダイオキシン類を凝集沈殿できるから、金属系凝集剤を大量添加する必要が無く、ダイオキシン除去処理を低コストで実現できる。放射線架橋体を凝集沈殿させる金属系凝集剤の臨界濃度が１ｐｐｍ以上であることも、本発明者等によって初めて発見されたものであり、この発明はこの知見に基づいて為された画期的なものである。
【０１０８】
第４の発明によれば、納豆の糸引き成分でそれ自体食品であるγ―ポリグルタミン酸やγ―ポリグルタミン酸塩を放射線架橋体として使用するから、飲料用原水などの浄化剤として使用されても極めて安全である。しかも、その凝集活性は極めて高いから、安全且つ高効率にダイオキシン汚染水の浄化処理を行うことができる。
【０１０９】
第５の発明によれば、分子量が１０００万以上のγ―ポリグルタミン酸又はγ―ポリグルタミン酸塩の放射線架橋体を使用するから、この高分子の放射線架橋体の水溶性により、ダイオキシン汚染水に投入すると短時間に溶解することができる。一旦溶解すると汚染水全体に分散してダイオキシン類を効果的に吸着して凝集沈殿させることができ、ダイオキシン捕獲効果を短時間に奏し、ダイオキシン除去処理には最適の材料を提供できる。
【０１１０】
第６の発明によれば、菌産生のγ―ポリグルタミン酸又はγ―ポリグルタミン酸塩を使用するから、化学合成品と異なり極めて安全性が高く、通常の原水や排水に適用できるだけでなく、その中でも特に、人の口に入る飲料用原水の浄化方法として安心して使用できる。
【０１１１】
第７の発明によれば、培養物そのものを用いるため、培養物からγ―ポリグルタミン酸又はγ―ポリグルタミン酸塩を単離する操作が不要となり、培養物中のγ―ポリグルタミン酸又はγ―ポリグルタミン酸塩を直ちに放射線架橋体に変換できる。この放射線架橋された培養物を凝集剤として利用するから、凝集剤の生産価格の低減に寄与できる。特に、液体培地で培養して得られる培養液の場合には、この培養液を凝集剤原液として活用できるので、凝集剤の添加時に水溶液調整などの手間が省け取扱が簡単になる利点がある。
【０１１２】
第８の発明によれば、ポリアミノ酸又はポリアミノ酸塩の放射線架橋体は栄養源であるから、ダイオキシン類を吸着して沈殿した放射線架橋体をダイオキシン分解微生物に与えることにより、放射線架橋体を栄養源にして微生物は増殖活動し、その増殖活動の中でダイオキシン類を分解して無毒化することができる。従って、ダイオキシン分解微生物の繁殖槽を用意し、凝集沈殿した汚泥廃棄物を栄養源とするから、極めて安価にダイオキシン類を分解することができる。しかも回収した汚泥は微生物の栄養源として減量するから、ダイオキシン類を含有する汚泥処理が不要になる利点を有する。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for purifying raw water for water supply such as river water, lake water, groundwater, and rainwater, and wastewater such as industrial wastewater and sewage, and more specifically, removing dioxins from contaminated water containing dioxins. The present invention relates to a dioxin-contaminated water purification method for purifying even safe water.
[0002]
[Prior art]
The water to be treated, such as raw drinking water, wastewater, and sewage, that is subject to purification treatment not only contains BOD components, COD components, and SS components, but also contains highly toxic dioxins. It has been known in recent years. However, in the conventional water purification treatment, attention has been focused on removing the BOD component, COD component, and SS component, and at present the dioxin purification method is behind.
[0003]
Dioxins are highly toxic chemicals that are generated in the incineration of waste and have attracted attention. In Japan, waste is first incinerated and the incineration residue is landfilled. If the waste contains chlorine-based organic substances or plastics, incineration produces dioxins as an intermediate substance, and the dioxins are mixed into the incineration residue.
[0004]
These dioxins are more toxic than potassium cyanide, and are said to be the most toxic substances as artificial substances. Among the dioxins, 2,3,7,8-TCDD has a carcinogenic effect at high concentration exposure, and its mechanism is said to be a promotion action to promote canceration.
[0005]
In animal experiments, dioxins induce malformations such as cleft palate and hydronephrosis, and it is said that a large amount of exposure affects reproductive function, thyroid function, and immune function. Effects on animals naturally imply similar effects on humans. From these studies, it must be said that the presence of dioxins in the environment is extremely dangerous, and it is extremely important to separate and remove dioxins from soil, water and air.
[0006]
However, when the incineration residue is disposed of in landfill, dioxins contained therein dissolve in rainwater and leak from the disposal site, flow into the sea, groundwater, and rivers, causing environmental pollution. It cannot be denied that this dioxin is concentrated through the food chain and accumulated in the human body through foods such as fish and shellfish and tap water.
[0007]
It has been found that dioxins generated by incineration can be almost removed by high-temperature incineration in a melting furnace or the like, but there is no other method than separating and decomposing dioxins flowing out into water. Therefore, as a technique for separating dioxins from dioxin-contaminated water, a precipitation treatment with a flocculant, an adsorption treatment with activated carbon, and a membrane separation treatment have been carried out.
[0008]
Further, as a decomposition treatment method, a decomposition treatment method using ultraviolet rays or ozone, a combined treatment method of dechlorination and an accelerated oxidation method, a microorganism decomposition method using filamentous fungi, white rot fungi, and the like are being developed.
[0009]
[Problems to be solved by the invention]
However, these conventional techniques have the following disadvantages. First, it is said that dioxins in contaminated water can be removed only by about 30% in a usual coagulation and precipitation treatment using a coagulant, because the sedimentation speed of fine particles is low. In addition, it has been pointed out that in the adsorption treatment using activated carbon, a large amount of expensive activated carbon is required, which not only increases the treatment price but also limits the dioxin adsorption power. Although membrane separation can treat a small amount of contaminated water, the ability to purify a large amount of contaminated water such as river water is limited.
[0010]
Further, in the decomposition treatment method using ultraviolet light or ozone, an ultraviolet light treatment device and an ozone treatment device are required, and a huge capital investment is required. Further, in the combined treatment method of the dechlorination and the accelerated oxidation method, the entire apparatus configuration becomes large-scale and complicated, so that a large capital investment is required, and as a result, the treatment cost rises. Although these processing methods can be realized in large-scale facilities, they cannot be realized in small-scale facilities due to financial constraints.
[0011]
The microbial decomposition method using filamentous fungi, white rot fungi, etc., which has attracted attention in recent years, has the advantage of high safety because it does not use chemical substances. However, since the treatment is a microorganism treatment, the treatment speed is relatively slow, and equipment specific to the microorganism treatment must be provided. In addition, there is a problem that since the cultivation of microorganisms is highly specialized, human costs also increase, and finally the treatment costs increase.
[0012]
Accordingly, the present invention provides a method for purifying dioxin-contaminated water that can efficiently separate and remove dioxins at low cost while removing COD components, BOD components, and SS components using ordinary coagulation treatment equipment. With the goal.
[0013]
[Means for Solving the Problems]
The present invention has been made to solve the above-mentioned problems, and a first invention is to add dioxin to a contaminated water containing a metal-based coagulant and a radiation crosslinked product of a polyamino acid or a polyamino acid salt. Is a method for purifying dioxin-contaminated water by coagulating and sedimenting dioxins to reduce the concentration of dioxin in the contaminated water. The present inventors have discovered that the radiation crosslinked product alone dissolves in water, but has a novel property that the solubility is rapidly reduced when coexisting with metal ions in water. Further, the present inventors have the property that, in the coexistence state with the metal ion, when the radiation crosslinked product coagulates and precipitates, the dioxins dissolved in water are adsorbed to the radiation crosslinked product and forcibly coprecipitate. The present inventors have newly discovered and completed the present invention. Dioxin removal treatment is possible with ordinary coagulation equipment because only metal coagulant and radiation cross-linking substance need to coexist in contaminated water. Dioxin treatment can be realized at low cost because no special equipment or equipment is required. . In addition, COD component, BOD component, SS component, etc. existing in contaminated water can be coagulated and precipitated by the metal-based coagulant and the radiation cross-linking body. A simple purification treatment method can be provided.
[0014]
The second invention is a dioxin-contaminated water purification method in which a radiation crosslinked product is added so that the concentration in water exceeds 3 ppm. The present inventors have newly found that the radiation crosslinked body alone dissolves in water to about 500 ppm, but when coexisting with metal ions, the solubility is reduced to about 3 ppm. Therefore, when the radiation cross-linked product is dissolved in dioxin-contaminated water in an amount exceeding about 3 ppm and metal ions are added thereto via a metal-based coagulant, the radiation cross-linked product corresponding to an excess amount exceeding about 3 ppm is coagulated and precipitated. And dioxins are forcibly precipitated by coagulation and precipitation of the radiation crosslinked product. The present invention has been achieved by discovering a solubility critical value of about 3 ppm. Since it is only necessary to add a relatively expensive radiation crosslinked product to a level exceeding about 3 ppm, the dioxin removal treatment can be performed at low cost. Becomes possible.
[0015]
The third invention is a method for purifying dioxin-contaminated water in which the concentration of a metal-based flocculant in water is adjusted to 1 to 3 ppm or more. The effect of selectively coagulating and precipitating dioxins by the radiation crosslinked product is exhibited when the coexisting metal coagulant concentration is 1 to 3 ppm or more. Variations within this range are affected by the concentration of contaminated water. Dioxins can be coagulated and precipitated only by coexisting a radiation crosslinked product with a metal-based coagulant having such a concentration, so that dioxin removal treatment can be performed at low cost.
[0016]
A fourth invention is a method for purifying dioxin-contaminated water, wherein the polyamino acid is γ-polyglutamic acid and the polyamino acid salt is γ-polyglutamate. γ-polyglutamic acid and γ-polyglutamate are stringent components of natto and are foods themselves, so they are extremely safe even when used as a purifying agent such as raw water for drinking, and have a very high coagulation activity. Accordingly, the dioxin-contaminated water can be purified safely and efficiently.
[0017]
The fifth invention is a method for purifying dioxin-contaminated water, in which a radiation cross-linked product of γ-polyglutamic acid or γ-polyglutamate mainly contains a radiation cross-linked product having a molecular weight of 10,000,000 or more. While γ-polyglutamic acid is hardly soluble in water, radiation-crosslinked γ-polyglutamic acid or γ-polyglutamate has water solubility. Due to the water-solubility of this radiation crosslinked product, when it is poured into dioxin-contaminated water, it dissolves in a short period of time and can effectively adsorb and coagulate and precipitate dioxin. Can provide the most suitable material.
[0018]
The sixth invention is a method for purifying dioxin-contaminated water, wherein γ-polyglutamic acid or γ-polyglutamate is γ-polyglutamic acid or γ-polyglutamate produced by a γ-polyglutamic acid-producing bacterium. Bacterial-produced γ-polyglutamic acid or γ-polyglutamate is extremely safe, unlike chemically synthesized products, so it can be applied not only to ordinary raw water and wastewater, but also, especially, raw water for eating and drinking that enters the human mouth. There is an advantage that it can be used as a purifying agent with confidence.
[0019]
A seventh invention is a dioxin-contaminated water, wherein the radiation cross-linked body of γ-polyglutamic acid or γ-polyglutamate is a radiation cross-linked body obtained by irradiating a culture obtained by culturing a γ-polyglutamic acid-producing bacterium. It is a purification method. Since the culture itself is used, the operation of isolating γ-polyglutamic acid or γ-polyglutamate from the culture is not required, and the γ-polyglutamic acid or γ-polyglutamate in the culture is immediately converted to a radiation crosslinked product. it can. Since the radiation-crosslinked culture can be used as a flocculant, it can contribute to a reduction in the production cost of the flocculant. In particular, in the case of a culture solution obtained by culturing in a liquid medium, this culture solution can be used as a stock solution of a flocculant, so that there is an advantage that the handling such as adjustment of an aqueous solution at the time of adding a flocculant is omitted and handling is simplified.
[0020]
The eighth invention relates to a radiation crosslinked product obtained by coagulating and precipitating dioxins by adding a radiation crosslinked product of a metal-based coagulant and a polyamino acid or a polyamino acid salt to contaminated water containing dioxins, and coagulating and precipitating the dioxin containing dioxins. Is given to a dioxin-decomposing microorganism as a nutrient source, and the dioxin-decomposing microorganism decomposes dioxins to make them harmless. Since the radiation cross-linked product of polyamino acid or polyamino acid salt is a nutrient source, if a radiation cross-linked product that adsorbs and precipitates dioxins is given to a dioxin-degrading microorganism, the radiation cross-linked product becomes a nutrient source and the microorganisms proliferate, Dioxins are decomposed and detoxified during the growth activity. Therefore, since a breeding tank for dioxin-degrading microorganisms is prepared and the collected waste is used as a nutrient source, dioxins can be decomposed extremely inexpensively.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
The present inventor has already disclosed in Japanese Patent Application Laid-Open No. 2002-210307 that a radiation cross-linked product of γ-polyglutamic acid or γ-polyglutamate has excellent agglutinating activity.・ We have repeated actual coagulation tests in the field of water treatment such as water treatment, industrial wastewater and sewage. Since γ-polyglutamic acid or γ-polyglutamate is itself a food and is harmless even in human mouth, it has been demonstrated to be an extremely safe flocculant.
[0022]
According to the study of the present inventors, this aggregation performance is not limited to radiation cross-linked products of γ-polyglutamic acid or γ-polyglutamate, but is a property common to radiation cross-linked products of polyamino acids or polyamino acid salts. I understand that. In other words, it was revealed that glutamic acid is only one kind of amino acid, and that a wide range of polyamino acids and polyamino acid salts can be used as a coagulant having strong and highest safety by radiation crosslinking.
[0023]
Through further research, the present inventors have discovered that when a radiation cross-linked product of a polyamino acid or a polyamino acid salt is used in combination with a metal-based flocculant, dioxins present in trace amounts in water are strongly adsorbed and coagulated and precipitated. I came to.
[0024]
First, dioxins will be described. Dioxins were found to be generated from chlorine-based organic compounds in garbage incinerators, which became a problem. At present, high-temperature incinerators that do not generate dioxins are being adopted, and existing incinerators are being discarded. With this problem as an opportunity, the Dioxins Control Measures Law was promulgated in 1999 as a regulation law for dioxins and has been up to the present.
[0025]
According to this law, dioxins are defined as being composed of polychlorinated dibenzo-para-dioxin (hereinafter referred to as PCDD), polychlorinated dibenzofuran (hereinafter referred to as PCDF) and coplanar polychlorinated biphenyl (hereinafter referred to as coplanar PCB). Have been. In this specification, dioxins are also called dioxins.
[0026]
PCDD is a compound in which two benzene rings are bonded via two Os. There are 75 kinds of PCDD compound groups (PCDDs) by adding H and Cl to the benzene ring. PCDF is a compound in which two benzene rings are bonded via one O, and it is known that 135 kinds of PCDF compound groups (referred to as PCDFs) exist by adding H and Cl to the benzene ring. Have been.
[0027]
Coplanar PCB is a compound in which two benzene rings are directly bonded, and is a dioxin-simulated product having the same toxicity as dioxins. By adding H and Cl to the benzene ring, there are more than a dozen types of PCB compounds (referred to as PCBs). Among the above-mentioned PCDDs, PCDFs and PCBs, there are 29 kinds of substances which are considered to be toxic.
[0028]
Among PCDDs, 2,3,7,8-TCDD, in which chlorine is added at positions 2, 3, 7, and 8, is known as the most toxic dioxin. An equivalent coefficient (referred to as TEF) is determined.
[0029]
When analyzing the dioxin concentration of water as in the present invention, the concentration of various dioxins contained in the sample is measured, and a value obtained by multiplying the concentration by the toxic equivalent coefficient and adding all the values is calculated, This is called the toxic equivalent (referred to as TEQ). According to laws and regulations, all reference values are specified in toxic equivalents.
[0030]
Article 7 of this law stipulates dioxin pollution standards for water quality, and environmental standards issued by the Environment Agency stipulate that public water bodies and groundwater shall be 1 pg-TEQ / l or less on an annual average. In other words, the condition is that the toxic equivalent per liter of sample water is 1 pg or less. Therefore, the standard is 1 pg-TEQ / l or less for tap water.
[0031]
In addition, Article 8 of this law sets forth the standards for water emission of dioxins, which are specified by Ordinance of the Ministry of the Environment according to the type and structure of a specific facility, taking into account the technical level. According to the Ordinance of the Ministry of the Environment, it is 10 pg-TEQ / l or less. That is, the discharge condition is that the toxic equivalent per liter of sample water is 10 pg or less. Therefore, in a facility such as a factory, a discharge standard of 10 pg-TEQ / l or less is a drainage discharge standard.
[0032]
A water purification method is required to meet the above-mentioned water quality standards (1 pg-TEQ / l or less) and drainage standards (10 pg-TEQ / l or less) for dioxins.
[0033]
The present inventors have started research on a radiation crosslinked product of a polyamino acid or a polyamino acid salt as a novel flocculant, and have accumulated various technical results. Dioxin contamination in tap water that people drink every day is a very serious problem, and the present inventors have also studied in detail a method for purifying dioxin-contaminated water using radiation cross-linked products of polyamino acids or polyamino acid salts.
[0034]
Among them, the present inventors have discovered a novel phenomenon in which the dioxin concentration in contaminated water rapidly decreases when a radiation cross-linked product of a polyamino acid or a polyamino acid salt is used (concurrently) with a metal-based flocculant. It has led to.
[0035]
Of course, the radiation cross-linked body is dissolved in water even when used alone, but the present inventors have found that the radiation cross-linked body has a novel property that the solubility of the radiation cross-linked body rapidly decreases when coexisting with metal ions in water. discovered. In other words, when the radiation crosslinked product coagulates and precipitates in the coexistence state with the metal ion, the dioxins dissolved in water are adsorbed on the surface and internal space of the radiation crosslinked product and are forced to co-precipitate. Was newly discovered this time.
[0036]
In contaminated water in which no metal ions are present, a considerable amount of the radiation cross-linked body is stably dissolved in water. When the metal-based coagulant is charged in this state, the radiation crosslinked body starts to be precipitated at countless places of the contaminated water.
[0037]
As will be described later, since the radiation crosslinked body has an infinite number of internal spaces, dioxins are trapped and precipitated in the innumerable internal spaces along with the COD component, the BOD component, and the SS component during precipitation.
[0038]
In particular, it is considered that dioxins are more often incorporated into SS components than exist alone in contaminated water. Therefore, it may be appropriate to consider that when the SS component is captured in the internal space, the dioxins are necessarily captured in the internal space. However, it should be noted that the status of contaminants at the molecular level is currently unknown, and the above situation is merely speculation.
[0039]
As described above, since the COD component, BOD component, SS component, and the like existing in the contaminated water can be coagulated and precipitated by the metal-based coagulant and the radiation crosslinked product, the ordinary water purification treatment can be realized simultaneously with the removal of dioxins. A periodical purification method was developed. Dioxin removal treatment is possible with ordinary coagulation equipment because only metal coagulant and radiation cross-linking substance need to coexist in contaminated water. Dioxin treatment can be realized at low cost because no special equipment or equipment is required. .
[0040]
In addition, the present inventors have studied the details of the addition concentration of the radiation crosslinked product. It has been newly discovered that the radiation crosslinked product alone dissolves in water at room temperature to about 500 ppm (or mg / l), but its solubility decreases to about 3 ppm when coexisting with metal ions.
[0041]
Therefore, for example, when 10 ppm of a radiation crosslinked body is added to contaminated water and then a metal-based flocculant is added, an excess of 7 ppm of the radiation crosslinked body is aggregated and precipitated. When the 7 ppm radiation crosslinked product coagulates and precipitates, dioxins in the contaminated water are adsorbed on the surface and the internal space of the radiation crosslinked product and precipitate together.
[0042]
In other words, to the dioxin-contaminated water at room temperature, the radiation cross-linked product is added at a concentration of about 3 ppm to about 500 ppm, and when the radiation cross-linked product in excess of 3 ppm coagulates and precipitates, the COD component in the contaminated water is reduced. Dioxins can be forcibly coagulated and precipitated together with the BOD component and the SS component. Since the radiation crosslinked product is relatively expensive, its concentration may be freely adjusted.
[0043]
As described above, the present invention has been achieved by finding a solubility critical value of about 3 ppm. Dioxins can be coagulated and precipitated only by adding a relatively expensive radiation crosslinker to a level exceeding about 3 ppm. Therefore, there is an advantage that dioxin treatment can be performed at low cost. Moreover, the toxic equivalent of dioxins can be reduced to 1 pg-TEQ / l or less, which is the standard of water quality, only by adding the radiation cross-linked product to this extent.
[0044]
Further, the present inventors have studied the concentration of the metal-based coagulant added. Since the metal-based flocculant is relatively inexpensive and is dissolved in a large amount in water, it can be added regardless of the concentration. However, it is also required to limit the amount of the metal-based coagulant as much as possible due to the problem of cost due to the amount of addition and the problem of remaining metal ions due to the addition of the metal-based coagulant. In particular, in a method for purifying raw water for drinking, it is determined that the amount of the coagulant added should be as small as possible.
[0045]
Then, when the addition concentration of the metal-based flocculant for rapidly lowering the solubility of the radiation crosslinked product was measured, it was found to be about 1 ppm at room temperature. That is, by setting the concentration of the metal-based coagulant to about 1 ppm or more and adding a radiation cross-linking substance exceeding about 3 ppm to contaminated water, it becomes possible to forcibly precipitate dioxins by coagulation of the radiation cross-linking substance. I found out.
[0046]
The upper limit of the concentration of the metal-based flocculant is not more than the solubility of the metal-based flocculant, and is an appropriate concentration according to the quality of the contaminated water. However, the solubility of the metal-based flocculant is extremely high, and usually no addition is made up to the solubility. Judging from common sense, low-concentration water is required for drinking water such as tap water, but if water quality deteriorates, it may be added up to about 50 ppm. In the case of high turbidity industrial contaminated water, 100 ppm to 1000 ppm may be added. Therefore, it can be said that the upper limit of the concentration of the metal-based flocculant is the solubility equivalent.
[0047]
Amino acids that can be used in the present invention include glycine, alanine, valine, norvaline, leucine, norleucine, isoleucine, phenylalanine, tyrosine, jod tyrosine, slinamin, threonine, serine, proline, hydroxyproline, tryptophan, thyroxine, methionine, cystine, cysteine, α-aminobutyric acid, aspartic acid, glutamic acid, lysine, hydroxylysine, arginine, histidine, asparagine, glutamine and the like. These include natural amino acids and synthetic amino acids, but natural amino acids are recommended from the viewpoint of safety. Polyamino acids or polyamino acid salts composed of these amino acids are used in the present invention.
[0048]
Generally, the structural formula of an amino acid is NH ₂ (COOH) -CH-R. Polyamino acids include a homopolymer in which the same amino acid is polymerized in a chain and a heteropolymer in which a plurality of types of amino acids are polymerized in a chain. Since hydrogen atoms H and oxygen atoms O in the polyamino acid form hydrogen bonds with water, the polyamino acid has a moisture retaining property of adsorbing water on the surface.
[0049]
Irradiation of the polyamino acid, which is a chain molecule, results in, for example, CH in the polyamino acid ₂ Becomes CH- by the dehydrogenation reaction, and CH- of the two polyamino acids binds to CH-HC to form a crosslinked product. When a large number of polyamino acids are cross-linked by radiation, a network structure is formed, and many bag-like spaces are formed inside the network structure. A cross-linking reaction may occur in a route other than the dehydrogenation reaction.
[0050]
Since crosslinking by radiation can be carried out without heating the polyamino acid, it has an advantage that a radiation cross-linked polyamino acid can be formed while maintaining the original properties of the amino acid. The radiation crosslinking reaction is a low-temperature crosslinking reaction, and is characterized in that it differs from the crosslinking reaction caused by heating. The polyamino acid undergoes thermal denaturation by heating, but is characterized in that it does not undergo thermal denaturation by the radiation crosslinking of the present invention.
[0051]
As described above, the crosslinked polyamino acid radiation product has a large number of bag-shaped spaces inside, and therefore has the ability to absorb and store water molecules in this bag-shaped space. it can. This water retention performance is considered to be the coagulation performance of absorbing and coagulating the suspended substance. That is, this water retention performance gives the ability to absorb COD components, BOD components, and SS components in water.
[0052]
The reason that the crosslinked polyamino acid adsorbs dioxins is considered as follows. As described above, polyamino acids have many H atoms and O atoms. On the other hand, since dioxins are composed of benzene rings, it is possible for hydrogen atoms attached to the benzene ring to hydrogen bond with the O atoms of the polyamino acid, or for hydrogen atoms of the polyamino acid to bond with the O atoms of the dioxins. It is. Due to such hydrogen bonding, countless dioxins are considered to be adsorbed on the surface of the polyamino acid radiation crosslinked product. When the dioxins are suspended in a hydrated state, it can be considered that the dioxins are adsorbed by hydrogen bonding to the polyamino acid.
[0053]
In addition, it is considered that dioxins are also adsorbed by hydrogen bonding to a large number of bag-like spaces inside the crosslinked polyamino acid radiation product. That is, it is considered that dioxins are adsorbed on the surface and inside of the radiation cross-linked polyamino acid together with the suspended substance. However, there are still many unclear points about the micro mechanism of the dioxin adsorption performance, and it is necessary to wait for future research.
[0054]
In this way, dioxins are adsorbed together with the suspended substance on the surface and inside of the radiation cross-linked polyamino acid, and when the radiation cross-linked is aggregated and precipitated by addition of metal ions, the dioxins adsorbed on the radiation cross-linked are Suspended material also results in simultaneous forced precipitation.
[0055]
Next, γ-polyglutamic acid will be considered as an example of a polyamino acid in order to further embody the above characteristics. γ-polyglutamic acid is (-OOC-CH ₂ -CH ₂ -CH (COOH) NH-) _n The subscript n gives the degree of polymerization. The starting material γ-polyglutamic acid preferably has a large molecular weight, particularly those having a molecular weight of several hundred thousand to several millions, and these molecular weights are determined by the degree of polymerization n.
[0056]
When this γ-polyglutamic acid is irradiated with radiation, CH is generated by a dehydrogenation reaction. ₂ Becomes CH-, the two linear chains of γ-polyglutamic acid are linked via CH-HC, and [(-OOC-CH ₂ -CH ₂ -CH (COOH) NH-) _n ] ₂ When the degree of cross-linking is further increased, [(-OOC-CH ₂ -CH ₂ -CH (COOH) NH-) _n ] _m Thus, a radiation crosslinked product having a large molecular weight is produced. Here, m indicates the degree of crosslinking and gives the number of linear chains of γ-polyglutamic acid to be cross-linked.
[0057]
By further increasing the degree of crosslinking m, the molecular weight of the γ-polyglutamic acid radiation crosslinked product is increased to 10,000,000 or more. Since γ-polyglutamic acid is a polypeptide chain, it has a network structure in which a large number of large spaces are formed inside by the connection of —CH—HC—. As described above, it is considered that the polluted water is absorbed into the many internal spaces and the pollutants are internally accumulated. In addition, it has the ability to strongly adsorb dioxins on its surface and internal space.
[0058]
As the polyamino acid according to the present invention, those produced by various production methods are used. Examples of the production method include a culture method using a microorganism and a chemical synthesis method. Polyamino acids produced by microorganisms are natural substances and are recommended from a safety point of view. Among polyamino acids, γ-polyglutamic acid is particularly effective.
[0059]
In the microorganism culturing method of γ-polyglutamic acid, bacteria such as Bacillus subtilis, Bacillus anthracis, Bacillus megaterium, and Bacillus natto of the genus Bacillus can be used. In particular, the F-2-01 strain of Bacillus subtilis is produced. It is suitable for. This strain produces .gamma.-polyglutamic acid having a molecular weight of hundreds of thousands to several millions and has a relatively large molecular weight, so that a crosslinked product can be efficiently produced by radiation.
[0060]
Γ-polyglutamic acid produced by microorganisms is a natural product that is harmless to humans and livestock, and has a great feature that it is a food, as it has been eaten as a main component of natto sticky substance since ancient times. In other words, this γ-polyglutamic acid is excellent not only in that it has coagulation performance and dioxin adsorption performance, but it is completely harmless even if it is erroneously eaten, and on the contrary, it becomes a nutrient.
[0061]
The γ-polyglutamic acid produced by the microorganism is a linear γ-peptide having no branch and is a copolymer of L-glutamic acid and D-glutamic acid, that is, a heteropolymer. Γ-polyglutamic acid having this heteropolymer structure is used as an example of a polyamino acid.
[0062]
The γ-polyglutamic acid produced by microorganisms is obtained by inoculating a microorganism in a liquid medium mixed with required nutrients, culturing at a required temperature for a required time, and isolating γ-polyglutamic acid from the culture solution. A solid medium other than the liquid medium may be used. In the present invention, not only γ-polyglutamic acid alone but also a culture solution itself or a culture containing γ-polyglutamic acid obtained by precipitation from the culture solution may be used. In this culture, γ-polyglutamic acid is produced simultaneously with γ-polyglutamic acid.
[0063]
As the chemically synthesized γ-polyglutamic acid, polymers having various structures such as a homopolymer of L-glutamic acid, a homopolymer of D-glutamic acid, and a mixture of these homopolymers are produced. These chemically synthesized γ-polyglutamic acids can also be used as examples of polyamino acids. That is, the polyamino acid may be a chemically synthesized product or a microbial synthesized product. As a water coagulant, a microbial synthetic product is recommended from the viewpoint of safety.
[0064]
The polyamino acid salt used in the present invention is produced as a salt by a neutralization reaction between the polyamino acid and a basic compound. A polyamino acid and a basic compound are dissolved in a solvent such as water at room temperature, and are efficiently produced by stirring with heating. Examples of the basic compound include hydroxides of alkali metals and alkaline earth metals, such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, and the like, and organic basic compounds such as ammonia and amines. There are compounds.
[0065]
Under the reaction conditions of the polyamino acid and the basic compound, the heating temperature is preferably 5 to 100C. If the temperature is lower than 5 ° C., the reaction will be slow. If the temperature exceeds 100 ° C., water, which is a kind of solvent, will boil and the reaction may not be stable. The pH is preferably in the range of weakly acidic to weakly basic, and particularly preferably in the range of 5 to 10. Further, the amount of the polyamino acid and the basic compound is suitably a stoichiometric reaction amount without excess or deficiency.
[0066]
As the polyamino acid or polyamino acid salt used in the present invention, those having a molecular weight of hundreds of thousands to several millions are suitable, and in the case of microbial production, the molecular weight is relatively large and falls within the above range. Many are distributed. Even in the case of chemical synthesis, those polymerized to hundreds of thousands or more are suitable.
[0067]
In the present invention, the polyamino acid or polyamino acid salt is cross-linked by radiation to produce a cross-linked product having a molecular weight of 10,000,000 or more. If it is 10,000,000 or more, an innumerable bag-like space is formed in the radiation crosslinked body, and the suspended solid absorbing performance and dioxin adsorption performance are high enough to withstand practical use.
[0068]
In addition to irradiating the polyamino acid or polyamino acid salt alone, irradiating the culture solution, culture, solid medium, etc., radiation-crosslinked polyamino acid or polyamino acid salt alone or contaminants of the radiation crosslinked body Can be obtained. Any of them can be used as the radiation crosslinked product according to the present invention. In particular, when the culture solution is irradiated with a radiation, a solution containing a radiation cross-linked body is generated, and when added to the liquid to be treated, the handling method and concentration adjustment are easy.
[0069]
As radiation for crosslinking, α-rays, β-rays, γ-rays, X-rays, electron beams, neutron beams, meson beams, ion beams and the like can be used. Among them, γ-rays, X-rays, and electron beams are preferred from the viewpoint of good operability. As X-rays, both X-ray tube and non-tube types can be used, and radiated light radiated from an electron ring that has been widely used in recent years can also be used. For the electron beam, a known electron beam irradiation device can be used according to the beam energy.
[0070]
Gamma rays are excellent in that they can use a radiation source. As the γ-ray source, there are cobalt 60, strontium 90, zirconium 95, cesium 137, cerium 141, ruthenium 177 and the like, but from the viewpoint of half-life and energy, cobalt 60 and cesium 137 are preferable.
[0071]
In the present invention, a radiation crosslinked product of a polyamino acid or a polyamino acid salt having a molecular weight of 10,000,000 or more is produced by radiation crosslinking of a polyamino acid or a polyamino acid salt. When the molecular weight is crosslinked to 10,000,000 or more, the radiation-crosslinked product has good aggregation characteristics and dioxin adsorption performance.
[0072]
In order to crosslink a polyamino acid to a molecular weight of 10,000,000 or more, it is necessary to irradiate the polyamino acid raw material with radiation at an absorption dose of 1 to 500 kGy, and crosslinking does not proceed easily at 1 kGy or less, and crosslinking proceeds excessively at 500 kGy or more. Therefore, the internal space formed by the network structure of the crosslinked body becomes smaller, and conversely, the aggregation activity decreases. From the viewpoints of crosslinkability and aggregation activity, the absorbed dose is more preferably 5 to 100 kGy. The above items are common to γ-polyglutamic acid and γ-polyglutamate.
[0073]
For example, γ-polyglutamic acid and γ-polyglutamate itself have the property of not being dissolved in organic solvents such as alcohol and acetone. Further, γ-polyglutamate is soluble in water, but γ-polyglutamic acid is insoluble in water. However, when this is subjected to radiation crosslinking, the surface of the radiation-crosslinked body is modified so as to have an affinity for water or a water-containing organic solvent such as water-containing alcohol or water-containing acetone. This characteristic of surface modification is also found in polyamino acid systems other than γ-polyglutamic acid.
[0074]
Therefore, by becoming a radiation crosslinked product, both γ-polyglutamic acid and γ-polyglutamate have an affinity for water or a water-containing organic solvent, and specifically, are dissolved in the water to be treated. Become. Since this property is also observed in other polyamino acids, a radiation cross-linked polyamino acid containing γ-polyglutamic acid is used in the present invention.
[0075]
The metal-based coagulant used in combination with the radiation crosslinked product in the present invention is composed of a metal-inorganic coagulant or a metal-organic coagulant. As the inorganic coagulant, known water treatment agents such as aluminum compounds such as basic aluminum chloride, aluminum sulfate, and aluminum chloride, and iron compounds such as basic ferric sulfate, ferric chloride, and ferrous chloride are used. You. As the metal organic coagulant, a known metal organic compound having coagulation performance is used.
[0076]
The object to be purified according to the present invention is generally water. This water includes drinking water such as river water, lake water, groundwater and rainwater, food wastewater used in the food processing and fermentation industries, ornamental water such as ponds, moats and fountains, swimming water such as pools, and urban water. Includes sewage, domestic wastewater, and industrial wastewater. In the present invention, when dioxin is mixed in the water to be treated, the water to be treated is referred to as dioxin-contaminated water.
[0077]
In the present invention, a dioxin contained in water is rapidly reduced by using a radiation cross-linked product comprising a polyamino acid or a polyamino acid salt and a metal-based flocculant in combination, and especially when treated in raw drinking water, dioxins are used. Can be provided. Therefore, the method of the present invention is most suitable as a method for purifying tap water or raw drinking water. However, it goes without saying that the present invention is applicable to all water containing dioxins (referred to as dioxin-contaminated water).
[0078]
For example, a case in which the present invention is applied to tap water treatment will be described. In the current normal treatment, raw water is taken from rivers, etc., and purified through the following processes: raw water → sedimentation basin → coagulation sedimentation basin → intermediate chlorination basin → rapid sand filtration basin → chlorination pond → distribution tank. Tap water is supplied to each home and business.
[0079]
In advanced treatment, purified water is processed through the following steps: raw water → sedimentation basin → coagulation sedimentation basin → medium ozone contact pond → rapid sand filtration pond → post-ozone contact pond → activated carbon adsorption pond → chlorine contact pond → distribution pond. Water is supplied to each home and business.
[0080]
In the above-mentioned ordinary treatment and advanced treatment, the step to which the purification method of the present invention is applied is a step of a coagulation sedimentation tank. In this coagulation sedimentation basin, a sulfuric acid band (aluminum sulfate) is supplied to forcibly coagulate and precipitate fine suspended substances (BOD component, COD component, SS component, etc.) in raw water.
[0081]
In the method of the present invention, a radiation crosslinked product of, for example, γ-polyglutamic acid or γ-polyglutamate is added to raw water for drinking simultaneously with the sulfate band. A sulfate band concentration M is added at least 1 ppm or more, and a radiation crosslinked body concentration m is added to a concentration exceeding about 3 ppm. As a result, it became possible not only to precipitate fine suspended substances (COD component, BOD component, SS component) by the synergistic action of both coagulants, but also to coagulate dioxins.
[0082]
In other words, dioxins that were conventionally difficult with ordinary treatment of tap water can be removed, and dioxins can be removed at the stage of coagulation sedimentation with advanced treatment, so ozone treatment and activated carbon treatment can be used to treat other hardly decomposable substances. You can focus.
[0083]
The method of the present invention can also be used for dioxin removal treatment of sewage and industrial wastewater. Even in this case, for example, a radiation crosslinked product of γ-polyglutamic acid or γ-polyglutamate is added to the water to be treated simultaneously with the sulfate band. In the case of sewage or industrial wastewater, a large amount of metal coagulant may be charged. Therefore, the concentration of the sulfuric acid band may be 100 ppm or more in some cases, and a radiation crosslinked product may be added in several tens ppm in order to surely remove dioxins.
[0084]
As a result, it becomes possible not only to precipitate fine suspended substances (COD component, BOD component, SS component) but also to coagulate dioxins and other hardly decomposable substances by the synergistic action of both coagulants. .
[0085]
According to the method of the present invention, the radiation crosslinked product that has adsorbed and coagulated and precipitated dioxins can be used as a nutrient source for microorganisms that decompose dioxins. Since the radiation cross-linked product is composed of amino acids, the radiation cross-linked product itself becomes a nutrient source for microorganisms, and the microorganism can decompose dioxins by using the radiation cross-linked product as a nutrient source. Therefore, an epoch-making method for decomposing the adsorbed and coagulated dioxins while reprocessing the coagulated sedimented radiation crosslinked sludge as a waste as a nutrient source of microorganisms is proposed.
[0086]
Filamentous fungi, white-rot fungi, and other microorganisms are used as dioxin-degrading microorganisms. It is said that oxidase genes are involved in the degradation of dioxins by microorganisms. As a biodegradation method, a biofilm method such as a contact aeration method or a rotating disk method, or a biological denitrification treatment is used.
[0087]
Moreover, when the radiation crosslinked sludge collected as waste is anaerobically fermented with a dioxin-decomposing microorganism in an anaerobic fermenter, the sludge itself becomes a nutrient source in addition to the decomposition of dioxins, and the sludge can be reduced in volume. That is, instead of storing the sludge collected by coagulation and sedimentation, it is utilized as a nutrient source, and an epoch-making method capable of realizing sludge reduction can be realized.
[0088]
【Example】
[Example: PAC and radiation crosslinked product (PG21)]
In this example, water having a COD of 300 obtained by pretreating industrial wastewater was used as raw water (dioxin-contaminated water). The measurement of dioxin concentration and toxic equivalent was performed in two stages. First, the concentration and dioxin equivalent of dioxins in this raw water were measured. Next, 30 ppm of a flocculant PAC (referred to as PAC) for commercial water treatment whose main component is polyaluminum chloride is added to the raw water, followed by stirring and mixing, and then a radiation crosslinked polyglutamic acid (referred to as PG21) is added. And aggregated and filtered through a glass filter. The concentration of dioxins and the toxic equivalent of this filtrate (treated water) were measured. Since the concentration and the toxic equivalent of dioxins were determined in accordance with JIS-K-0312, the details are omitted.
[0089]
The measured PCDDs were 12 kinds, 2,3,7,8-TetraCDD, TetraCDDs, 1,2,3,7,8-PentaCDD, PentaCDDs, 1,2,3,4,7,8-HexaCDD, 1 , 2,3,6,7,8-HexaCDD, 1,2,3,7,8,9-HexaCDD, HexaCDDs, 1,2,3,4,6,7,8-HeptaCDD, HeptaCDDs, 1,2 , 3,4,6,7,8,9-OctaCDD and OctaCDDs. Concentrations and toxic equivalents are summarized as PCDDs.
[0090]
The measured PCDFs were 14 kinds, 2,3,7,8-TetraCDF, TetraCDFs, 1,2,3,7,8-Penta-CDF, 2,3,4,7,8-PentaCDF, PentaCDFs , 1,2,3,4,7,8-HexaCDF, 1,2,3,6,7,8-HexaCDF, 1,2,3,7,8,9-HexaCDF, 2,3,4,6 , 7,8-HexaCDF, HexaCDFs, 1,2,3,4,6,7,8-HeptaCDF, 1,2,3,4,7,8,9-HeptaCDF, HeptaCDFs, 1,2,3,4 , 6,7,8,9-OctaCDF. Concentrations and toxic equivalents are summarized as PCDFs.
[0091]
Furthermore, the measured PCBs were 12 kinds, 3,4,4 ′, 5-TetraCB, 3,3 ′, 4,4′-TetraCB, 3,3 ′, 4,4 ′, 5-PentaCB, 3, 3 ', 4,4', 5,5'-HexaCB, 2 ', 3,4,4', 5-PentaCB, 2,3 ', 4,4', 5-PentaCB, 2,3,3 ', 4,4'-PentaCB, 2,3,4,4 ', 5-PentaCB, 2,3', 4,4 ', 5,5'-HexaCB, 2,3,3', 4,4 ', 5 -HexaCB, 2,3,3 ', 4,4', 5'-HexaCB and 2,3,3 ', 4,4', 5,5'-HexaCB. Concentrations and toxic equivalents are summarized as PCBs.
[0092]
Table 1 shows the measured concentrations (pg / l) of dioxins for raw water and PG21-treated water. Table 2 shows toxic equivalents (pg-TEQ / l) of dioxins for raw water and PG21-treated water. In the table, ND (Not Detected) means that it could not be detected.
[0093]

[0094]

[0095]
As can be seen from Table 1, when PG21 is treated with PAC on raw water, the concentration of dioxins decreases from 63 (pg / l) to 7.7 (pg / l), about 1/8. On the other hand, as can be seen from Table 2, the toxic equivalent sharply decreased from 1.14 (pg-TEQ / l) to 0.00065 (pg-TEQ / l) to about 1/1800.
[0096]
As described above, the water quality standard in the environment is 1 (pg-TEQ / l) in terms of toxic equivalent. The raw water has 1.14 (pg-TEQ / l), which slightly exceeds the water quality standard. However, when the PG21 is treated, the water quality drops to 0.00065 (pg-TEQ / l). Has been demonstrated. Thus, it can be seen that the dioxin treatment can be easily performed by using the method of the present invention.
[0097]
[Comparative example: PAC treatment alone]
The raw water of COD300 (dioxin-contaminated water) used in the examples was subjected to a flocculation treatment by adding only 30 ppm of PAC as a metal-based flocculant. The purpose of the present invention is to test the extent to which dioxins can coagulate and precipitate when PG21 is not used together to prove the effect of using PAC21. The coagulation treatment method and the dioxin analysis method were performed in exactly the same manner as in the examples.
[0098]
Table 3 shows the measured concentrations (pg / l) of dioxins for raw water and PAC-treated water. Table 4 shows toxic equivalents (pg-TEQ / l) of dioxins for raw water and PAC-treated water.
[0099]

[0100]

[0101]
As can be seen from Tables 3 and 4, it was found that in the PAC treatment alone, both the concentration and the toxic equivalent could be reduced to about 70% of the raw water. The present inventors have repeated similar experiments using various metal-based flocculants alone, but have come to the conclusion that it is difficult to reduce the concentration of dioxins to 50% or less by using a metal-based flocculant alone. did. Since the toxic equivalent is 0.79 (pg-TEQ / l), it slightly clears the water quality standard of 1 (pg-TEQ / l), but when the dioxin concentration of the raw water is considerably high, It seems difficult to meet the water quality standards. That is, it is difficult to perform dioxin purification treatment on high-concentration contaminated water such as industrial wastewater using PAC alone.
[0102]
As described above, it is difficult to satisfy the water quality standards by the PAC treatment alone for dioxin-contaminated water. However, when a radiation crosslinker such as PG21 is added to a metal-based coagulant such as PAC as in the present invention, the dioxin concentration is reduced to about 1/10, and the toxic equivalent, which is the target of water quality, is reduced. It has been found that it can be reduced to about 1/2000.
[0103]
In the above, the purification method has been described using the raw water for drinking, sewage, and industrial wastewater as the water to be treated. However, the object that can be purified by the present invention is dioxin-containing water in general. In other words, the present invention relates to raw water for drinking such as river water, lake water, groundwater, and rainwater, food wastewater used in food processing and fermentation industries, ornamental water such as ponds, moats and fountains, and swimming water such as pools. It can purify a wide range of water, such as municipal sewage, industrial wastewater, and domestic wastewater.
[0104]
The present invention is not limited to the above embodiments and examples, and various modifications and design changes without departing from the technical idea of the present invention are included in the technical scope. Needless to say.
[0105]
【The invention's effect】
According to the first invention, when the radiation crosslinked product rapidly coagulates and precipitates in the coexistence state with the metal ion, the dioxins dissolved in water are adsorbed to the radiation crosslinked product and forcedly coprecipitated. Can be. It is only necessary to make the metal-based flocculant and the radiation cross-linked substance coexist in dioxin-contaminated water. Dioxin removal treatment is possible with ordinary coagulation equipment, and special equipment and equipment are not required, so low-cost dioxin separation treatment. Can be realized. In addition, not only dioxins, but also COD components, BOD components and SS components present in contaminated water can be coagulated and precipitated by the metal-based coagulant and radiation cross-linking body, enabling normal water purification treatment at the same time as removal of dioxins. A novel and innovative purification method can be provided.
[0106]
According to the second invention, an excess amount of radiation exceeding about 3 ppm is dissolved in the dioxin-contaminated water by dissolving the radiation cross-linked body in an amount exceeding about 3 ppm and adding a metal ion thereto through a metal-based coagulant. The crosslinked product can be coagulated and precipitated, and dioxins can be forcibly precipitated by coagulated precipitation of the radiation crosslinked product. The critical value of the solubility of about 3 ppm has been discovered by the present inventors, and it is only necessary to add a relatively expensive radiation cross-linked product in a trace amount exceeding about 3 ppm. There is an advantage that can be implemented.
[0107]
According to the third invention, dioxins can be coagulated and precipitated only by coexisting a radiation crosslinked product with a metal-based coagulant having a concentration of several ppm or more (1 to 3 ppm or more). And the dioxin removal treatment can be realized at low cost. The present inventors have also discovered for the first time that the critical concentration of a metal-based flocculant for coagulating and precipitating a radiation crosslinked product is 1 ppm or more, and the present invention is an epoch-making epoch-making based on this finding. Things.
[0108]
According to the fourth invention, since γ-polyglutamic acid or γ-polyglutamic acid, which is a food itself, is used as a radiation cross-linked product as a stringing component of natto, it can be used as a purifying agent such as raw water for drinking. Extremely secure. Moreover, since the coagulation activity is extremely high, the dioxin-contaminated water can be purified safely and efficiently.
[0109]
According to the fifth invention, since a radiation cross-linked product of γ-polyglutamic acid or γ-polyglutamate having a molecular weight of 10,000,000 or more is used, the radiation cross-linked product of this polymer is charged into dioxin-contaminated water due to its water solubility. Then, it can be dissolved in a short time. Once dissolved, it can be dispersed throughout the contaminated water to effectively adsorb dioxins and coagulate and precipitate, exhibiting a dioxin-capturing effect in a short time, and provide an optimal material for dioxin removal treatment.
[0110]
According to the sixth invention, since γ-polyglutamic acid or γ-polyglutamate produced by the bacterium is used, it is extremely high in safety, unlike a chemically synthesized product, and can be applied not only to ordinary raw water and wastewater, but also among them. In particular, it can be safely used as a method for purifying raw drinking water that enters the human mouth.
[0111]
According to the seventh invention, since the culture itself is used, the operation of isolating γ-polyglutamic acid or γ-polyglutamate from the culture is unnecessary, and γ-polyglutamic acid or γ-polyglutamic acid in the culture is eliminated. The salt can be immediately converted to a radiation crosslinked product. Since this radiation-crosslinked culture is used as a flocculant, it can contribute to a reduction in the production price of the flocculant. In particular, in the case of a culture solution obtained by culturing in a liquid medium, this culture solution can be used as a stock solution of a flocculant, so that there is an advantage that the handling such as adjustment of an aqueous solution at the time of adding a flocculant is omitted and handling is simplified.
[0112]
According to the eighth invention, the radiation crosslinked product of the polyamino acid or the polyamino acid salt is a nutrient source. Therefore, the radiation crosslinked product which adsorbs and precipitates dioxins is given to the dioxin-degrading microorganism, so that the radiation crosslinked product is nourished. As a source, microorganisms proliferate and can decompose and detoxify dioxins during the proliferating activity. Therefore, a dioxin-decomposing microorganism breeding tank is prepared, and the sludge waste that has been coagulated and settled is used as a nutrient source, so that dioxins can be decomposed extremely inexpensively. Moreover, since the recovered sludge is reduced as a nutrient source for microorganisms, there is an advantage that the sludge treatment containing dioxins becomes unnecessary.

Claims (8)

Dioxin-contaminated water characterized by adding a metal-based flocculant and a radiation cross-linked product of a polyamino acid or a polyamino acid salt to contaminated water containing dioxins to coagulate and precipitate dioxins, thereby reducing the dioxin concentration in the contaminated water. Purification method. The method for purifying dioxin-contaminated water according to claim 1, wherein the radiation-crosslinked body is added so that the concentration in water exceeds 3 ppm. The dioxin-contaminated water purification method according to claim 1, wherein the concentration of the metal-based flocculant in water is adjusted to 1 to 3 ppm or more for the radiation crosslinked product. 4. The method for purifying dioxin-contaminated water according to claim 1, wherein the polyamino acid is γ-polyglutamic acid, and the polyamino acid salt is γ-polyglutamate. 5. The method for purifying dioxin-contaminated water according to claim 4, wherein the radiation crosslinked product of γ-polyglutamic acid or γ-polyglutamate mainly contains a radiation crosslinked product having a molecular weight of 10,000,000 or more. The method for purifying dioxin-contaminated water according to claim 4, wherein the γ-polyglutamic acid or γ-polyglutamate is γ-polyglutamic acid or γ-polyglutamate produced by a γ-polyglutamic acid-producing bacterium. The dioxin contamination according to claim 4, wherein the radiation crosslinked product of γ-polyglutamic acid or γ-polyglutamate is a radiation crosslinked product obtained by irradiating a culture obtained by culturing a γ-polyglutamic acid-producing bacterium with radiation. Water purification method. Dioxin is added to contaminated water containing dioxins by adding a metal coagulant and a radiation cross-linked product of a polyamino acid or a polyamino acid salt to coagulate and precipitate the dioxin. A method for decomposing dioxins, wherein said method comprises degrading dioxins with said dioxin-decomposing microorganisms to render them harmless.