JP2007098353A - Activated sludge treatment method of wastewater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for treating the washing wastewater of the gas, which is formed by the pyrolysis of combustible waste such as a waste plastic, shredder dust, etc., using activated sludge. <P>SOLUTION: The pyrolytic gas formed by the pyrolysis of combustible waste is washed with water and the obtained wastewater after washing is separated into a water phase, tar and an oil component phase on the basis of specific gravity. The water phase is recovered as specific gravity separated water and the pH of the specific gravity separated water is adjusted to 8-12 to sediment, separate and remove heavy metals contained in the specific gravity separated water while the water obtained after sedimentation and separation is subjected to activated sludge treatment. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a treatment method after pyrolyzing and gasifying combustible waste, and more particularly to a method for treating activated sludge of waste water generated by cleaning pyrolysis gas.

  In the process of pyrolyzing and gasifying combustible waste such as waste plastic, shredder dust, municipal waste, waste building materials, waste wood, mowing grass, food waste, oil-impregnated sludge, and tar, gas is used for gas purification. Wet cleaning with water is effective. By washing with water, the gas temperature is cooled, and some of the components gasified at high temperature are condensed and liquefied or solidified to be taken into the waste water of the washing water. In some cases, combustible waste such as shredder dust contains vinyl chloride. In this case, a large amount of chlorine is mainly contained in the form of HCl in the gas generated by thermal decomposition. Since chlorine is an element that may form harmful organic chlorinated substances such as dioxin and PCB, it is desired that chlorine contained in the pyrolysis gas be safely detoxified and removed.

  In addition, when metal is mixed in combustible waste such as automobile shredder dust, dust containing metal is also taken into the drainage of cleaning water. Of these substances that migrate from pyrolysis gas to cleaning wastewater, there is concern that some of them may have environmental impact or biotoxicity.

  Waste water treatment with activated sludge is a useful technique that has a water purification action such as decomposition of COD-causing substances by the action of microorganisms at normal temperature and pressure, and is safe, low cost, and capable of reducing environmental burden. However, there is a problem that harmful substances brought in from pyrolysis gas have an adverse effect on activated sludge microorganisms and make it difficult to treat with activated sludge, and in the treatment of waste plastic and shredder dust pyrolysis gas washing wastewater etc., At present, the technology for utilizing activated sludge has hardly been established. At present, there are few established methods for treating wastewater generated by thermal decomposition of combustible waste such as waste plastic and shredder dust.

  For example, Patent Document 1 discloses a method for removing a COD component, a normal hexane extract component, and a hydrophobic turbid component contained in cleaning wastewater of exhaust gas generated when pyrolyzing waste plastic. According to this document, COD components are oxidized by aeration with air supplied from a blower, and normal hexane extract components and hydrophobic turbid components adhere to and float on the surface of fine bubbles by aeration, and are then made weakly acidic by adding sulfuric acid. After adjusting the pH, add ferrous sulfate to microfloc the remaining hydrophobic turbid component, then adjust the pH by adding alkali, add a polymer agglomeration aid, and then microfloced the hydrophobic turbid component Is separated by coagulation precipitation, and the remaining normal hexane extract component and COD component are adsorbed on activated carbon, and activated sludge is not used.

  Patent Document 2 discloses a method for purifying pyrolysis gas containing oil generated by pyrolysis of waste such as waste plastic. This document discloses that hydrogen chloride contained in the pyrolysis gas can be neutralized and removed by using an alkaline aqueous solution such as sodium hydroxide as a cleaning solution for the pyrolysis gas. Furthermore, it is disclosed that low-boiling point oil and water are separated in an oil-water separation tank so that low-boiling point oil can be reused as recovered oil, and water is sent to a wastewater treatment facility for processing.

  Patent Document 3 discloses that chlorine contained in pyrolysis gas generated when carbonized waste plastic with coal in a coke oven is brought into contact with cold water generated in the coke oven, thereby chlorinating chlorine. A method of incorporating ammonium as ammonium into water is disclosed.

JP 2000-70995 A JP-A-9-279171 JP 2001-123180 A JP 2000-328071 A JP 2005-114197 A Water Waste Water Handbook (Edited by the Water Waste Water Handbook Editorial Committee) (1973) (Maruzen)

  As described above, although there are various techniques for the treatment of wastewater caused by cleaning of gas generated when combustible waste such as waste plastic is thermally decomposed, the following problems exist.

  For example, in Patent Document 1, when a normal hexane extract component and a COD component are adsorbed on activated carbon, a new process is required for discarding or regenerating the activated carbon on which the activated carbon is adsorbed. It is desirable that the normal hexane extract component and the COD component are decomposed and removed.

  Further, in Patent Document 2, although it is described that the waste water after purification of the pyrolysis gas is sent to a waste water treatment facility for treatment, a specific waste water treatment method is not shown at all and is unknown. There is no description such as activated sludge treatment.

  Patent Document 3 describes that chlorine contained in the pyrolysis gas is brought into contact with the aqueous water, and chlorine is taken into the aquatic water as ammonium chloride, but there is no description of using activated sludge as a subsequent treatment. .

  Here, wastewater treatment with activated sludge has a water purification action such as decomposition of a normal hexane extract component and a COD component by the action of microorganisms at normal temperature and pressure, and is widely known to be a useful technique.

  However, the treatment with activated sludge is hardly utilized for the treatment of cleaning wastewater used for gas purification of gas generated by thermal decomposition of combustible waste such as waste plastic and shredder dust. The reason for this is that the pyrolysis gas of combustible waste contains many kinds of substances that adversely affect the microorganisms of the activated sludge and is difficult to treat with the activated sludge. It can be said that there is no established method for treating waste water generated by thermal decomposition of combustible waste such as plastic and shredder dust.

  Therefore, the problem to be solved by the present invention is to provide a method that enables the activated sludge treatment of waste water generated by thermal decomposition of combustible waste such as waste plastic and shredder dust, which has been difficult until now. It is.

  In order to solve the above-mentioned problems, the present inventors have intensively studied a method for stably performing the treatment with activated sludge on the cleaning waste water of gas generated by the thermal decomposition of combustible waste such as waste plastic and shredder dust.

  First, we examined activated sludge that is resistant and capable of decomposing against harmful substances and COD-causing substances contained in the cleaning wastewater of pyrolysis gas. As a result, it has been found that activated sludge mainly used for the decomposition treatment of COD-causing substances such as phenols and the like produced from coke ovens such as steelworks is suitable for the purpose of the present invention. The pyrolysis gas contains a large amount of chlorine mainly as HCl. However, the pyrolysis gas can be removed and fixed as harmless ammonium chloride by washing the pyrolysis gas with an aqueous solution containing high concentration of ammonia. Furthermore, the removal of chlorine can suppress the formation of harmful organic chlorinated substances such as dioxins and PCBs. Further, when waste is heated in a gasification melting furnace or the like to recover and purify the gas, if HCl is contained, it causes corrosion of the apparatus and piping. In this respect, it was found that the ability to remove HCl is effective in inhibiting corrosion.

  Therefore, by using activated sludge to treat the activated sludge generated from the coke oven at the steelworks to activated sludge, cleaning of the gas generated along with the pyrolysis of combustible waste such as waste plastic and shredder dust We succeeded in establishing the technology to treat wastewater as follows.

In addition, we examined the components contained in the wastewater generated by the thermal decomposition of combustible waste such as waste plastic and shredder dust. For each component that may adversely affect the activated sludge treatment from the detected components, the toxicity to the activated sludge microorganisms was quantitatively evaluated. By doing in this way, it succeeded in clarifying the component which has a bad influence on activated sludge among the components contained in the waste_water | drain generated with the thermal decomposition of combustible wastes, such as a plastic and shredder dust. Therefore, as described below, for the components that have an adverse effect on these activated sludges, substances that have an adverse effect on these activated sludge treatments in advance of the activated sludge treatment using the physicochemical properties of these substances. It has succeeded in making it possible to treat with activated sludge by removing or reducing the concentration in these wastewaters.
(1) The pyrolysis gas generated by the pyrolysis of combustible waste is washed with water, and the resulting waste water after washing is separated into specific phases of an aqueous phase and a tar and oil phase, and the aqueous phase is separated by specific gravity. It is recovered as water, the pH of the specific gravity separation water is adjusted to 8 or more and 12 or less, heavy metals contained in the specific gravity separation water are separated by precipitation, and the obtained water after precipitation separation is treated with activated sludge. Wastewater activated sludge treatment method.
(2) The activated sludge treatment method for wastewater according to (1), wherein the activated sludge treatment is a standard activated sludge method in which air is aerated in the mixed water of the water after the precipitation separation and the activated sludge.
(3) The activated sludge treatment method for wastewater according to (1) or (2), wherein the activated sludge is activated sludge for treating aqueous water generated from a coke oven in a steel production process.
(4) The activated sludge treatment method for wastewater according to any one of (1) to (3), wherein the water used for cleaning the pyrolysis gas is aqueous water generated from a coke oven in a steel production process.
(5) The water after the precipitation separation is further distilled or reduced in pressure to remove the components to be evaporated, and then the water after the removal of the evaporated components is treated with the activated sludge. (1) to (4) One of the activated sludge treatment methods for wastewater.
(6) The specific gravity separation water is mixed with the aqueous water generated from the coke oven in the steel production process, the pH is adjusted to 9.5 or more and 12 or less, and ammonia stripping, which is a method for removing ammonia in the aquatic water, is performed, (1) to (4) characterized in that heavy metals contained in pH-adjusted water are removed by precipitation and removed, and the components to be evaporated are removed, and the obtained water after removal of the evaporated components is treated with the activated sludge. ) Any activated sludge treatment method for wastewater.
(7) The water after the precipitation separation or the water after the removal of the transpiration component is diluted with at least one of aqueous water, deaerated water after the ammonia stripping treatment, and seawater, and the diluted water The activated sludge treatment method for wastewater according to any one of (1) to (6), wherein the activated sludge treatment is performed.
(8) The activated sludge treatment method for waste water according to (7), wherein the dilution is from a 2-fold dilution to a 10,000-fold dilution.
(9) The activated sludge treatment of wastewater according to (7) or (8), wherein the ratio of the total amount of the dewatered and dewatered water used for dilution and seawater is 1: 1 to 1:10 Method.
(10) Any one of (7) to (9), wherein the pH of the diluted water is adjusted to 6 or more and 9.5 or less, and then the water after the pH adjustment is treated with the activated sludge. Activated sludge treatment method for wastewater.
(11) The waste water after washing the pyrolysis gas is cyan, aniline, benzonitrile, benzoic acid, captolactam, phenol, chlorophenol, benzene, methylcyclopentane, 2-methylphenol, 3-methylphenol, 4- (1) to (10) characterized in that the waste water contains one or more of methylphenol, 1,2-benzenediol, 5-aminoindole, 2-ethenylbenzofuran, lead and zinc. Any activated sludge treatment method for waste water.
(12) Immediately before the activated sludge treatment, precipitation separation of the heavy metal so that the lead concentration of the water after the precipitation treatment, the water after removal of the transpiration component, or the water after the dilution is less than 1 mg / L. After adjusting with at least any means of pH adjustment in the dilution and dilution ratio adjustment in the dilution, the water after the adjustment is treated with the activated sludge, The drainage according to any one of (1) to (11) Activated sludge treatment method.
(13) Precipitation separation of the heavy metal so that the zinc concentration of the water after the precipitation treatment, the water after removal of the transpiration component, or the water after the dilution is less than 10 mg / L immediately before the activated sludge treatment After adjusting by at least any means of pH adjustment in the dilution and dilution ratio adjustment in the dilution, the water after the adjustment is treated with the activated sludge. (1) to (12) Activated sludge treatment method.
(14) In the distillation or reduced pressure so that the cyan concentration of the water after the precipitation treatment, the water after removal of the transpiration component, or the water after the dilution immediately before the activated sludge treatment is less than 5 mg / L. After adjusting with at least any means of transpiration and dilution ratio adjustment in the dilution, the water after the adjustment is treated with the activated sludge. (1) to (13) Sludge treatment method.
(15) The distillation or depressurization so that the benzonitrile concentration of the water after the precipitation treatment, the water after removal of the transpiration component, or the water after the dilution immediately before the activated sludge treatment is less than 5 mg / L. (1) to (14), wherein the activated sludge is treated with the adjusted water after adjusting by means of at least one of transpiration in the dilution and dilution ratio adjustment in the dilution. Activated sludge treatment method.
(16) The concentration of the normal hexane extract of the water after the precipitation treatment, the water after the removal of the transpiration component, or the water after the dilution immediately before the activated sludge treatment is less than 20 mg / L. The activated sludge is treated with the activated sludge after adjustment by at least one of the separation of tar and oil in specific gravity separation, transpiration in the distillation or reduced pressure, and dilution ratio adjustment in the dilution. The activated sludge treatment method for wastewater according to any one of (1) to (15).
(17) The combustible waste may be one or more of waste plastic, shredder dust, municipal waste, waste building materials, waste wood, cut grass, food waste, oil-containing sludge, and tar. The activated sludge treatment method for wastewater according to any one of (1) to (16).

  In the present invention, “dealing water” refers to an aqueous water whose ammonia concentration has been reduced by an ammonia stripping treatment generated from a coke oven in a steel production process.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to carry out the activated sludge process of the waste_water | drain which generate | occur | produces with the gasification by thermal decomposition of combustible wastes, such as a waste plastic and a shredder dust, and also the existing water treatment activity of a steelworks It becomes possible to process easily using a sludge installation.

  The form for implementing this invention is demonstrated in detail below.

  Combustible waste such as waste plastic and shredder dust can be pyrolyzed to generate gas. As a method of thermally combusting combustible waste, for example, as described in Patent Document 4, combustible waste is continuously used in a fluidized bed low temperature gasification furnace and a high temperature gasification furnace. There is a gasification method. In addition, as described in Patent Document 5, the combustible waste is gasified and melted in a shaft furnace type gasifier using the amount of heat possessed by the combustible waste. Can do. In this case, the components contained in the pyrolysis gas obtained by pyrolyzing flammable waste at a high temperature of about 1600 ° C. to 2200 ° C. include methane, ethane, propane, butane, carbon monoxide, carbon dioxide, hydrogen , Nitrogen and hydrogen chloride. In addition to oil and dust, shredder dust and municipal waste may also contain heavy metal components such as lead, zinc, and copper. Dust is removed and washed by bringing water into contact with the generated gas. For example, there are gas cleaning methods such as passing the pyrolysis gas through a shower-like water curtain, flushing the pyrolysis gas with water, or passing the pyrolysis gas through the water in the column. Such gas cleaning using water is referred to as wet cleaning in the present invention. As described above, the drainage generated by the wet cleaning includes condensed water generated by cooling the gas.

  This wastewater contains tar and oil. There is a concern that tar and oil may contain harmful organic chlorinated substances such as fat-soluble dioxins. Therefore, the wastewater is phase-separated into a water phase and a tar and oil phase that may contain dioxins by specific gravity separation, and the water phase is recovered as specific gravity separation water.

  As a method of separating the tar and oil from the water phase by specific gravity, for example, the water phase is easily separated from the tar and oil phase which may contain dioxins by allowing the waste water to stand for 30 minutes or more. The supernatant can be recovered as specific gravity separation water. In addition to standing, tar, oil, and aqueous phase can be separated and specific gravity separated water can be recovered by centrifugation, decanter use, pressurized flotation, and the like.

  In addition to toxic substances such as tar, oil and fat-soluble organic chlorinated substances, the waste water often contains mixed metals, particularly in combustible waste such as shredder dust of automobiles. For example, when metals such as lead and zinc are contained in the waste water, they may adversely affect the activated sludge.

  Therefore, as described above, an alkali agent is added to the specific gravity separation water separated from tar and oil that may contain dioxins due to the difference in specific gravity, thereby making the specific gravity separation water alkaline. Preferably, the pH is adjusted to 8 or more and pH 12 or less. In this way, heavy metals contained in the wastewater are precipitated and separated and removed. For example, zinc precipitates as zinc hydroxide and lead precipitates as lead oxide, and can be separated and removed. If the pH is less than 8, precipitation of heavy metals hardly occurs, and if the pH is more than 12, heavy metals such as zinc and lead do not precipitate as complex ions and are dissolved again. For this reason, it is desirable to adjust to pH 8 or more and pH 12 or less. However, since the cost of alkaline agents such as sodium hydroxide used for pH adjustment is disadvantageous, it is more desirable to adjust the pH to 8 or more and 11 or less.

  Precipitation of generated heavy metals and mixing of tars and oils hinder the reuse of each, so if possible, the pH due to the addition of the above alkaline agent to the specific gravity separation water separated and recovered from tars and oils. Make adjustments. The aqueous phase is separated and recovered from the generated heavy metal precipitate. The water after precipitation separated and recovered from the precipitation of heavy metals in this way reduces the concentration of heavy metals such as lead and zinc that adversely affect the microorganisms of the activated sludge. When it does not contain, it becomes possible to process with activated sludge.

  As the activated sludge used here, it is desirable to use activated sludge for treating the low water generated from the coke oven. This is because activated water sludge has a function of decomposing aromatic chlorinated products such as phenols, organic chlorinated products such as cresol, and cyanide, compared with activated sludge used for municipal sewage treatment. This is because the resistance to materials that may adversely affect these activated sludges and the processing ability to decompose them are high.

  In addition, as water used for wet cleaning of gas generated by thermal decomposition of this combustible waste, fresh water such as industrial water, tap water, ground water, river water can be used, but waste plastic, shredder dust, etc. It is known that when pyrolyzing flammable waste, chlorine resulting from vinyl chloride or the like contained therein is mainly contained in the pyrolysis gas as HCl. Since chlorine is an element that can easily form organic chlorinated substances such as dioxins and PCBs by chlorination, it is desirable to use cleaning water that can remove chlorine from the pyrolysis gas in the wet cleaning. Aqueous water generated from the coke oven contains a high concentration of ammonia nitrogen. Therefore, when using water as the water used for wet cleaning, the chlorine contained in the pyrolysis gas is brought into contact with the pyrolysis gas and the water by the method as described above, as shown in the formula (1): It can be fixed and removed as harmless ammonium chloride.

HCl + NH ₄ OH → NH ₄ Cl + H ₂ O Formula (1)
In addition, since corrosive HCl can be removed, an effect of suppressing corrosion of the gas purification apparatus can be expected.

  In addition, when using the water other than the water for cleaning the pyrolysis gas, it is prepared so as to contain 100 mg / L or more and 5000 mg / L or less of ammonia for the purpose of removing chlorine contained in the pyrolysis gas. It is more desirable to use purified water. However, in this case, since it is costly to add ammonia, it is advantageous in terms of cost to use the safety water as washing water.

  As described above, heavy metals such as lead and zinc mainly derived from shredder dust among flammable wastes are separated as metal hydroxide precipitates, and the recovered water after separation has an adverse effect on activated sludge. However, the pyrolysis gas cleaning wastewater contains not only heavy metal components but also mainly organic substances that have an adverse effect on the activated sludge. There are many.

  Ingredients that may adversely affect activated sludge other than heavy metals contained in the above-mentioned pyrolysis gas cleaning wastewater include cyanide, aniline, benzonitrile, benzoic acid, captolactam, phenol, chlorophenol, benzene, methyl Examples include cyclopentane, 2-methylphenol, 3-methylphenol, 4-methylphenol, 1,2-benzenediol, 5-aminoindole, 2-ethenylbenzofuran, and the like. Many of these components can be removed from the water after precipitation separation by distillation or vacuum evaporation. For example, in the case of distillation, harmful components can be removed from the water after precipitation separation by boiling water for 10 minutes or more.

In a facility that treats aqueous water generated from a coke oven such as an ironworks, an ammonia stripping device is provided for evaporating and removing ammonia in the aquatic water by depressurization or distillation, and this can be used in the present invention. Ammonia stripping reduces the vaporization of ammonia by converting the ammonium salt existing as NH ₄ ⁺ contained in the water beforehand into an ammonia molecule (NH ₃ ) that is easy to evaporate by making it alkaline with a pH of 9.5 or higher. It is a process to promote.

  Usually, an iron strip ammonia stripping apparatus is continuously operated to remove ammonia from the water. Therefore, it is desirable that the water after the precipitation separation is mixed with this water and ammonia stripping treatment.

  Therefore, in the present invention, in the step of precipitating and separating the heavy metal by making the heavy metal contained in the waste water generated by washing the pyrolysis gas of the above-mentioned combustible waste or the water mixed with the water into alkaline water, By using an ammonia stripping device and adjusting the pH to 9.5 or more and 12 or less, heavy metals are precipitated and separated. By ammonia stripping, removal of ammonia and harmful components contained in the waste water by vaporization and removal of heavy metals are performed. Precipitation separation can be achieved at low cost using existing equipment. However, since the cost of an alkaline agent such as sodium hydroxide used for pH adjustment is disadvantageous, it is more preferable to adjust the pH to 9.5 or more and pH 11 or less. In this way, it is possible to efficiently carry out both the removal of ammonia from the safety water and the removal of harmful substances from the wastewater derived from the thermal decomposition of combustible waste.

  As described above, water to be used for the activated sludge treatment is obtained. Activated sludge used for the purpose of treating the aqueduct generated from the coke oven at an ironworks or the like is diluted with seawater diluted dewatered water or dewatered dewatered seawater. Because it is acclimatized to water, it is excellent in decomposing organic compounds with aromatic rings, which are difficult to biodegrade in activated sludge of general municipal sewage treatment, such as phenols contained in water, and heat It is thought that it is excellent also in the decomposition | disassembly of the component contained in the washing | cleaning waste water of decomposition gas.

  In addition, the activated water treatment sludge is acclimatized by diluting the dehydrated water or dewatered water at a volume ratio or flow rate ratio of 1: 1 to 1:10 with seawater. Therefore, also in the present invention, it is desirable to dilute the water to be treated with the activated sludge in advance with at least one of low-grade water, de-grade water or seawater. When diluting the water to be treated with activated sludge with water or dehydrated water, the water to be treated with activated sludge + water to be treated with activated sludge + (with activated sludge) It is desirable to dilute the dilution ratio represented by the water to be treated + dealed water) / the water to be treated with activated sludge to 2 to 10,000 times. In addition, when the water to be treated with activated sludge is diluted with seawater, the dilution ratio represented by (water to be treated with activated sludge + seawater) / water to be treated with activated sludge is more than 2 times and 10,000. It is desirable to dilute to less than twice. More preferably, it is 100 times or less.

  The activated water sludge is usually acclimatized to seawater-diluted water or seawater-diluted dewatered water, so the water after precipitation separation is not diluted with water, dewatered water or seawater, and is separated by precipitation. If the subsequent water or the water after removal of the transpiration component is directly treated with the water-activated activated sludge, the activated sludge treatment may be adversely affected by adversely affecting the microorganisms of the activated sludge.

  Therefore, it is desirable that the activated sludge treatment is performed after diluting at least two times with at least one of water, de-almized water, and seawater. From the viewpoint of reducing the influence on the water-activated activated sludge, the higher the dilution ratio, the better. However, if the dilution ratio is too high, the treatment of water after precipitation or removal of transpiration components is difficult to proceed quantitatively. . Therefore, the dilution factor is desirably 10,000 times or less. It is also possible to dilute using both aqueduct or deaerated water and sea water. It is desirable to use the ratio in the range of 1: 1 to 1:10. In addition, for the purpose of reducing the nitrogen concentration, it is more preferable to use deanized water rather than ammonia water for dilution.

  In addition, the pH of the water flowing in for treatment with activated sludge, that is, the water after the precipitation treatment, the water after the removal of the transpiration component, or the water after the dilution immediately before the treatment of the activated sludge is reduced to the activated sludge microorganisms. In order to prevent the adverse effects of the above, it is desirable to adjust in advance using sulfuric acid, hydrochloric acid, or an acid waste liquid that has pH of 6 or more and 9.5 or less if available.

  As mentioned above, wastewater generated by wet cleaning of pyrolysis gas of combustible waste such as waste plastic and shredder dust and activated sludge contained in condensed water generated by cooling pyrolysis gas can be adversely affected. As possible substances, cyan, aniline, benzonitrile, benzoic acid, captolactam, phenol, chlorophenol, benzene, methylcyclopentane, 2-methylphenol, 3-methylphenol, 4-methylphenol, 1,2-benzene Examples include diol, 5-aminoindole, 2-ethenylbenzofuran, lead, and zinc. Ammonia activated sludge has the function of decomposing aromatic chlorinated products such as phenols and organic chlorinated products such as cresols and cyanide compounds, so these activated sludges are compared with activated sludge used for municipal sewage treatment. It has a high resistance to materials that can adversely affect sludge and a high ability to decompose them.

  Among the above substances, the lead that may adversely affect the activated sludge is removed by precipitation separation of lead by adjusting the pH so that the lead concentration of water flowing into the activated sludge is less than 1 mg / L. In addition, it is desirable to control the concentration by diluting with low-grade or de-grade water or seawater. For example, the concentration of lead contained in the water to be treated with activated sludge is monitored, and if the concentration is 1 mg / L or more, or there is a risk of it, precipitation of lead is further promoted by precipitation separation of the heavy metal. The pH of the water after precipitation can be reduced by adjusting the pH as described above. Alternatively, the lead concentration can be reduced to less than 1 mg / L by increasing the dilution ratio of dilution with water or de-altered water or seawater performed before the activated sludge treatment.

  Among the above substances, zinc that may adversely affect activated sludge is obtained by adjusting the pH, as in the case of lead, so that the zinc concentration of water flowing into activated sludge is less than 10 mg / L. It is possible to control the concentration by removing zinc by precipitation separation and diluting with aqueous or deaerated water or seawater.

  Among the above substances, cyan which may adversely affect activated sludge, the removal of cyan by distillation or vacuum evaporation so that the cyan concentration of water to be treated with activated sludge is less than 5 mg / L, And, it is possible to control the concentration by dilution using the above-mentioned safe water, de-alted water or seawater.

  In addition, high-concentration thiosulfuric acid is contained in the low-grade water or de-grade water. Thiosulfuric acid reacts with cyanide to convert it to thiocyanate. Thiocyanate is a substance that is not detected by the measurement of all cyan described in JIS K102, and is not cyan. Thiocyanate is also contained in a high concentration in low and dehydrated water, but its toxicity is much lower than cyan and it is easily decomposed by activated water treatment sludge. When the thiocyan concentration of water flowing into the activated sludge is 600 mg / L or less, there is no adverse effect on the water-treated activated sludge and it can be decomposed satisfactorily.

  Regarding benzonitrile that may adversely affect activated sludge among the above substances, removal of benzonitrile by distillation or evaporation under reduced pressure so that the benzonitrile concentration of water flowing into activated sludge treatment is less than 5 mg / L. It is possible to control the concentration by diluting with water or de-alarm water or seawater.

  In addition, for oils that may have an adverse effect on activated sludge, the concentration of normal hexane extractables used as an indicator of oil content is less than 20 mg / L. Thus, it is possible to control the concentration by separating water from the tar and oil, removing the oil by distillation or vacuum transpiration, and diluting with cold or de-altered water or seawater.

  In addition, because water-activated activated sludge has the activity of decomposing organic chlorinated substances such as cresol, the wastewater and pyrolysis gas generated by wet cleaning of pyrolysis gas of combustible waste such as plastic and shredder dust are cooled. It is possible to decompose the organic chlorinated substances contained in the condensed water generated by this.

  The combustible waste targeted by the present invention is waste plastic, shredder dust, municipal waste, waste building materials, waste wood, mowing grass, food waste, oil-containing sludge, and tar. Among these wastes, the waste plastic and the shredder dust contain any of polypropylene, polyethylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, and polychlorinated biphenyl as a composition.

  The main components contained in these pyrolysis gas wash waters that may adversely affect activated sludge are cyan, aniline, benzonitrile, benzoic acid, captolactam, phenol, chlorophenol, benzene, Contains some of methylcyclopentane, 2-methylphenol, 3-methylphenol, 4-methylphenol, 1,2-benzenediol, 5-aminoindole, 2-ethenylbenzofuran, lead, and zinc as major components It can be reduced by the method of the present invention.

  The activated sludge used in the present invention is used for the purpose of removing COD and decomposing the above-mentioned harmful components. It is desirable that the activated sludge contains microorganisms belonging to at least one of Delia, Alkaligenes, Rhodoclas, Actinobacteria, Bacillus, Desulfuromonas, Rhodobacter, Chromatium, Thios Rix, Planktmyces, Sulfur-oxidizing bacteria, and Nitrosomonas. This is because these microorganisms are present in the activated water treatment sludge and have the action of decomposing COD components and harmful substances contained in the aqueous water and pyrolysis gas washing waste water.

  By using this activated sludge, it is possible to decompose and treat the COD causative substance and the normal hexane extract contained in the water flowing into the activated sludge of the present invention by the standard activated sludge method in which air is aerated. . The standard activated sludge method uses aerobic microorganisms (activated sludge) floating in the aeration tank, supplies oxygen by aeration and mixes and agitate the tank to bring the sewage and microorganisms into sufficient contact. This is a basic activated sludge treatment method. (For example, see Non-Patent Document 1, etc.)

Example 1
An embodiment of the present invention will be described below based on the processing flow shown in FIG.

With respect to the gas generated from the shaft furnace type gasification furnace 1 that thermally decomposes the shredder dust at 2000 ° C., the gas water 3 generated from the coke oven 18 is cleaned by bringing the water into contact with the gas in the gas cleaning device 2. When the properties of the gas cleaning waste water 5 generated by this were investigated, the components as shown in Table 1 were contained. The amount of wastewater generated after gas cleaning was 100 m ³ / day.

  The washed waste water was treated based on the treatment flow shown in FIG. First, specific gravity separation was performed by allowing the gas washing wastewater to stand in a specific gravity separation tank 6 for 30 minutes, and the aqueous phase was separated from a tar and oil phase that may contain dioxins. The separated aqueous phase was transferred to a tank 7 where heavy metals were separated by precipitation. Sodium hydroxide solution which is alkaline agent 8 was added, and the pH was adjusted to pH 8.5 in heavy metal precipitation separation tank 7. By this pH survey, heavy metals such as lead and zinc contained in the wastewater were separated by precipitation. The concentration of heavy metals such as lead and zinc that adversely affect the microorganisms of activated sludge is reduced in the water after separation and recovered from the precipitation of heavy metals in this way. Cyanide and benzonitrile, which have adverse effects, were included in this wastewater. Therefore, the water from which heavy metals were separated was distilled at 100 ° C. for 30 minutes using a distillation apparatus 9. The water 10 after removal of the transpiration component obtained by the distillation treatment is diluted 4 times with deanized water 13 in a dilution and pH adjustment tank 12, and then this water is further diluted 2.5 times with seawater 14, The pH was adjusted to 8.5 with the alkaline agent 8. The ratio of dewatered water to seawater used for dilution was 1: 2.

  Table 2 shows the properties of the diluted water before the activated sludge treatment thus obtained.

  Here, the concentration of thiocyanate or thiosulfuric acid is higher than that of the gas washing waste water shown in Table 1 because it is brought in from the deaerated water used for dilution.

  The lead concentration after dilution for activated sludge treatment is 0.1 mg / L, the zinc concentration is 1 mg / L, the cyan concentration is 3 mg / L, the benzonitrile concentration is 1 mg / L, and the normal hexane extract substance concentration is 5 mg / L. It was confirmed that the water quality suitable for the activated sludge treatment was obtained by the treatment in the previous step.

  The water thus obtained was used in a steelworks to be used for the decomposition treatment of phenols, thiocyanate and sulfur compounds contained in the aqueduct, and was put into an aquatic treatment activated sludge tank 15 for treatment. This activated sludge contained microorganisms such as comamonas, alkaligenes, deinococcus, sulfur-oxidizing bacteria, and nitrosomonas, which were contained in activated sludge acclimated to water-safe treatment. The activated sludge treatment was a standard activated sludge method in which air was aerated and operated at a water temperature of 30 ° C. and an HRT of 36 hours.

  Table 3 shows the properties of the treated water 16 obtained after the activated sludge treatment.

  While the COD of the water flowing into the activated sludge was 1200 mg / L, the COD of the treated water decreased to 50 mg / L. Also, no harmful components such as cyan and benzonitrile due to the gas cleaning wastewater were detected. This treated water satisfied the drainage standards stipulated in the Water Pollution Control Law.

For comparison, a separate study was conducted for a case where the pH of the heavy metal precipitation separation tank 7 was less than 8 or higher than 12, but heavy metals such as zinc and lead did not precipitate and remained in the aqueous phase at a high concentration. As a result, the activated sludge in the latter stage was adversely affected.
(Example 2)
The embodiment of the present invention will be described below based on the processing flow shown in FIG.

In response to the gas generated from the gasification furnace 1 that thermally decomposes municipal waste including waste plastic and shredder dust at 1800 ° C., the gas-washing device 2 converts the water-safety 3 generated from the coke oven 18 into the gas. When the properties of the gas cleaning wastewater 5 generated by contact and cleaning were examined, components as shown in Table 4 were contained. The amount of gas cleaning wastewater generated was 150 m ³ / day.

  This gas cleaning waste water was processed based on the processing flow shown in FIG.

  First, the effluent was subjected to specific gravity separation using a decanter as the specific gravity separation tank 6 for tar and oil water, and the aqueous phase was separated and recovered from the tar and oil phase that may contain dioxins. The separated specific gravity separated water was transferred to a tank 7 where heavy metals were precipitated and separated. Sodium hydroxide solution as alkaline agent 8 was added to adjust pH to pH10. By this pH survey, heavy metals such as lead and zinc contained in the wastewater were precipitated and separated and removed. The water separated and recovered from the precipitation of heavy metals in this way reduces the concentration of heavy metals such as lead and zinc that adversely affect the microorganisms of the activated sludge. Cyanide and benzonitrile were contained in this waste water.

  Therefore, the water obtained by precipitating and separating heavy metals from the waste water as described above is diluted 10-fold with the water 3 of the steelworks, then treated with the ammonia stripping device 19, and volatile such as cyan and benzonitrile by vacuum evaporation. Organic matter and ammonia were removed. Ammonia stripping treated water (dealted water) 20 was diluted 2.5 times with seawater in the dilution and pH adjustment tank 12, and the pH was further adjusted to pH9.

  The diluted water thus obtained was subjected to activated sludge treatment. Table 5 shows the properties of the diluted water subjected to this activated sludge treatment.

  Here, the concentration of thiocyanate or thiosulfuric acid is higher than that of the gas washing waste water shown in Table 1 because it is brought in from the deaerated water used for dilution.

  Lead concentration of diluted water used for activated sludge treatment is 0.1 mg / L, zinc concentration is 0.2 mg / L, cyan concentration is 2 mg / L, benzonitrile concentration is 0.5 mg / L, normal hexane extractable substance concentration Was 1 mg / L, and it was confirmed that the water quality suitable for the activated sludge treatment was obtained by the treatment in the previous step.

  The water obtained in this manner was used in a steelworks to be used for the decomposition treatment of phenols, thiocyanate, and sulfur compounds contained in the aqueduct or into an aquatic treatment activated sludge tank 15. This activated sludge contained microorganisms such as ammonia-oxidizing bacteria, cytophaga, Bacteroides, Alteromonas, etc. contained in the activated sludge acclimated to the water treatment. The activated sludge treatment was a standard activated sludge method in which air was aerated and operated at a water temperature of 30 ° C. and an HRT of 36 hours. Table 6 shows the properties of the treated water 16 treated with activated sludge.

  While the COD of the water flowing into the activated sludge was 1100 mg / L, the COD of the treated water was reduced to 40 mg / L.

Also, no harmful components such as cyan and benzonitrile due to the gas cleaning wastewater were detected. This treated water satisfied the drainage standards stipulated in the Water Pollution Control Law.
(Example 3)
Hereinafter, an embodiment of the present invention will be described based on the processing flow shown in FIG.

  For the gas generated from the gasification furnace 1 that thermally decomposes the shredder dust generated from the automobile at 2000 ° C., the water 3 generated from the coke oven 18 is cleaned by bringing the water into contact with the gas in the gas cleaning device 2. did. The washing wastewater 5 is recovered by separating water from tar and oil in a tar and oil water specific gravity separation tank 6 and then recovered, and then sodium hydroxide is added to the recovered specific gravity separated water in a heavy metal precipitation tank 7 with a pH of alkaline agent 8. Thus, the pH was adjusted to 10.4, and heavy metals were precipitated and separated. The water after precipitation after separating heavy metals was recovered. The organic matter contained in the water was analyzed by GC-MS (gas chromatogram mass spectrometry) (see FIG. 4).

  Further, the water recovered by precipitation separation of the heavy metal was further distilled at 100 ° C. for 30 minutes by the distillation apparatus 9. Furthermore, the water 10 after removal of the transpiration component obtained by the distillation was recovered, and the organic matter contained in the water after removal of the transpiration component was also analyzed by GC-MS (see FIG. 5). In addition, the COD and TOC of these waters before and after distillation were also measured. Table 7 shows the analysis results of COD and TOC. It was found that both COD and TOC were reduced by distillation.

  The results of analyzing the water before distillation by GC-MS are shown in FIG.

  The data in FIG. 4 is shown below.

  Next, the result of analyzing the distilled water by GC-MS is shown in FIG.

  A clear peak was confirmed only for <1> benzene.

  From FIG. 4 and FIG. 5, it was confirmed that various organic substances were removed by distillation.

  As described above, aniline, benzonitrile, benzoic acid, captolactam, phenol, chlorophenol, benzene, methylcyclopentane, 2-methylphenol, 3 contained in the wastewater generated by washing the shredder dust with pyrolysis gas. It was confirmed that -methylphenol, 4-methylphenol, 1,2-benzenediol, 5-aminoindole, and 2-ethenylbenzofuran can be reduced by distillation.

It is a figure which shows the processing flow of Example 1 of this invention. It is a figure which shows the processing flow of Example 2 of this invention. It is a figure which shows the processing flow of Example 3 of this invention. It is a figure showing the result of GC-MS of the water before distillation. It is a figure showing the result of GC-MS of the water after distillation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shredder dust pyrolysis gasification furnace 2 Gas cleaning apparatus 3 Aqueous water 4 Gas after washing 5 Gas cleaning drainage and / or condensed water 6 Tar, oil water separation tank 7 Heavy metal precipitation separation tank 8 Alkaline agent addition 9 Distillation apparatus 10 Distilled water DESCRIPTION OF SYMBOLS 11 Distillation gas trap apparatus 12 Dilution and pH adjustment tank 13 Dewatered water 14 Seawater 15 Activated sludge tank 16 Treated water 17 Outflow 18 Coke oven 19 Ammonia stripping apparatus 20 Ammonia stripping treated water (dealted water)
21 Transpiration gas trap equipment, ammonium sulfate production equipment

Claims (17)

  The pyrolysis gas generated by pyrolysis of combustible waste is washed with water, and the resulting washed waste water is separated into specific phases of an aqueous phase and tar and oil components, and the aqueous phase is recovered as specific gravity separated water. Waste water characterized by adjusting the pH of the specific gravity separation water to 8 or more and 12 or less to precipitate and remove heavy metals contained in the specific gravity separation water, and subjecting the resulting water after precipitation separation to activated sludge treatment. Activated sludge treatment method.   2. The activated sludge treatment method for wastewater according to claim 1, wherein the activated sludge treatment is a standard activated sludge method in which air is aerated in a mixed water of the water after precipitation separation and activated sludge.   The activated sludge treatment method for wastewater according to claim 1 or 2, wherein the activated sludge is activated sludge for treating low water generated from a coke oven in a steel production process.   The activated sludge treatment method for waste water according to any one of claims 1 to 3, wherein the water used for cleaning the pyrolysis gas is aqueous water generated from a coke oven in a steel production process.   The water after the precipitation separation is further distilled or reduced in pressure to remove the components to be evaporated, and then the water after the removal of the evaporated components is treated with the activated sludge. The activated sludge treatment method for waste water described.   The specific gravity separation water is mixed with the aqueous water generated from the coke oven in the steel production process, the pH is adjusted to 9.5 or more and 12 or less, ammonia stripping is performed as a method for removing ammonia in the aquatic water, and the pH is adjusted. 5. The activated sludge treatment is performed on the water after removal of the transpiration component obtained by precipitating and removing heavy metals contained in the water, and removing the transpiration component obtained. The activated sludge treatment method for waste water according to Item.   The water after the precipitation separation or the water after the removal of the transpiration component is diluted with at least one of aqueous water, deaerated water after the ammonia stripping treatment, and seawater, and the diluted water is activated sludge. The activated sludge treatment method for waste water according to any one of claims 1 to 6, wherein treatment is performed.   8. The activated sludge treatment method for wastewater according to claim 7, wherein the dilution is from a 2-fold dilution to a 10,000-fold dilution.   9. The activated sludge treatment method for wastewater according to claim 7 or 8, wherein the ratio of the total amount of safe water and dewatered water used for the dilution to seawater is 1: 1 to 1:10.   10. The pH of the diluted water is adjusted to 6 or more and 9.5 or less, and then the water after the pH adjustment is treated with the activated sludge. An activated sludge treatment method for wastewater.   The waste water after washing the pyrolysis gas is cyan, aniline, benzonitrile, benzoic acid, captolactam, phenol, chlorophenol, benzene, methylcyclopentane, 2-methylphenol, 3-methylphenol, 4-methylphenol, 11. The waste water containing one or more of 1,2-benzenediol, 5-aminoindole, 2-ethenylbenzofuran, lead, and zinc. The activated sludge treatment method of waste water as described in 2.   The pH adjustment in the precipitation separation of the heavy metal so that the lead concentration of the water after the precipitation treatment, the water after the removal of the transpiration component, or the water after the dilution is less than 1 mg / L immediately before the activated sludge treatment. The wastewater according to any one of claims 1 to 11, wherein the activated sludge treatment is performed on the water after the adjustment after adjusting by at least any means for adjusting the dilution ratio in the dilution. Activated sludge treatment method.   Immediately before the activated sludge treatment, pH adjustment in precipitation separation of the heavy metal so that the zinc concentration of the water after the precipitation treatment, the water after the removal of the transpiration component, or the water after the dilution is less than 10 mg / L The wastewater according to any one of claims 1 to 12, wherein the activated sludge treatment is performed on the water after the adjustment after adjusting by at least any means for adjusting the dilution ratio in the dilution. Activated sludge treatment method.   The transpiration in the distillation or reduced pressure so that the cyan concentration of the water after the precipitation treatment, the water after the removal of the transpiration component, or the water after the dilution is less than 5 mg / L immediately before the activated sludge treatment, The activated sludge treatment method for wastewater according to any one of claims 1 to 13, wherein the activated water is treated with the activated sludge after the adjustment with at least one means of dilution ratio adjustment in dilution. .   Transpiration in the distillation or reduced pressure so that the benzonitrile concentration of the water after the precipitation treatment, the water after the removal of the transpiration component, or the water after the dilution is less than 5 mg / L immediately before the activated sludge treatment, The activated sludge treatment of waste water according to any one of claims 1 to 14, wherein the activated water is treated with the activated sludge after the adjustment with at least any means of dilution ratio adjustment in the dilution. Method.   In the specific gravity separation so that the concentration of the normal hexane extract substance of the water after the precipitation treatment, the water after the removal of the transpiration component, or the water after the dilution is less than 20 mg / L immediately before the activated sludge treatment. 2. The activated sludge treatment is performed on the water after adjustment after at least one of separation of tar and oil, transpiration in the distillation or reduced pressure, and adjustment of dilution ratio in the dilution. The activated sludge treatment method for wastewater according to any one of -15.   The combustible waste is one or more of waste plastic, shredder dust, municipal waste, waste building material, waste wood, cut grass, food waste, oil-containing sludge, and tar. The activated sludge treatment method for waste water according to any one of 1 to 16.

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