JP2010247072A - Wastewater treatment method, wastewater treatment apparatus, and method and system of purifying energy gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide treatment technology of wastewater in energy gas purification by which ammonia and organic substances incorporated in the wastewater in energy gas purification can be treated stably and efficiently by using activated sludge without using materials from the outside of a system. <P>SOLUTION: An easily decomposable aromatic compound BTX separated by energy gas purification is supplied to an activated sludge treatment apparatus AC for treating the energy gas purification water to improve the function of activated sludge bacteria, the removal of a persistent compound is accelerated, and influence of an inhibitor is suppressed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wastewater treatment method and a wastewater treatment apparatus for treating refined wastewater generated when refining energy gas such as gasification fuel or synthesis gas obtained by gasifying fossil fuel such as coal, low-grade coal, and the like. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an energy gas purification method and purification system to be used. The present invention relates to a method and a purification system for energy gas.

  In recent years, global warming and resource depletion due to mass consumption of petroleum resources have become problems, and attention has been paid to effective use of resources that have not been used in the past. As such resources, methane gas that is gasified from low-grade coal such as lignite that has not been used before and that is obtained by fermenting livestock manure, etc. There is energy gas such as biogas as a component. These energy gases contain harmful substances such as hydrogen sulfide, ammonia, and cyan gas, which cause catalyst poisoning and equipment corrosion, depending on the type of the energy gas. Waste water containing water and cyanide is discharged. Therefore, in order to detoxify and release these harmful substances contained in the purified wastewater, it is necessary to treat each of them. There are various methods for the treatment of such harmful substances, such as methods using chemical agents and electrochemical energy, methods using physicochemical removal operations, combustion, etc., which are included in the treatment of energy gas purification wastewater. Selection is made in consideration of the substance and concentration to be used, and is performed in combination.

  The activated sludge treatment method known as one of the wastewater treatment methods is an excellent method of treating using the action of microorganisms without using expensive chemicals and the like, and is used in various fields. . For wastewater containing ammonia, nitrogen removal treatment by an activated sludge method (circulation modification) combining nitrification and denitrification has been attempted. For example, Patent Documents 1 and 2 below describe that an activated sludge treatment method is used for the treatment of safe water discharged in the production of coke. Moreover, in the following patent document 3, it is proposed to use activated sludge for the treatment of waste water that has been washed with gas generated in connection with thermal decomposition of combustible waste such as waste plastic, and after removing oil and heavy metals from the waste water. Disclosed is an activated sludge treatment.

  On the other hand, in the following Patent Document 4, it is described that the function of activated sludge is hindered by harmful components such as cyanide and sulfide in the treatment of activated sludge discharged from coke ovens and wastewater from petroleum refineries. As a method for coping with this, it has been proposed to add beer-squeezed rice cake or tofu-squeezed rice cake to waste water.

Japanese Patent Laid-Open No. 05-192679 Japanese Patent Laid-Open No. 07-204681 JP 2007-098353 A Japanese Patent Laid-Open No. 07-112194

  As can be seen from Patent Document 4, cyan and the like are obstacles to activated sludge treatment. Therefore, when energy gas refined wastewater containing cyanide is treated with activated sludge, the function of activated sludge is similarly inhibited. For this reason, it is necessary to take measures to maintain the function of activated sludge. However, in order to apply food waste such as the above-mentioned beer squeezed lees to the energy gas purification process, it is time and labor required to secure the source and transport it. And cost becomes a problem. Therefore, it is desired to develop a coping method that is practically easy to adopt.

  In view of the above problems, the present invention provides a wastewater treatment method and an energy gas purification method capable of stably and efficiently treating ammonia and organic matter contained in refined wastewater generated by energy gas purification using activated sludge. The task is to do.

  In addition, the present invention does not require the labor and complicated management of transportation, can take measures to maintain the function of activated sludge, and can efficiently process the hardly decomposable organic substances contained in the purified wastewater. It is an object of the present invention to provide a wastewater treatment apparatus and an energy gas purification system.

  In order to solve the above-mentioned problem, the present inventors have been able to suppress the functional inhibition of activated sludge by using an aromatic compound recovered in the energy gas purification process as a result of intensive studies. The present inventors have found that it is possible to treat ammonia and organic substances in waste water by effectively using the materials in the system without requiring the introduction of materials from the outside of the energy gas purification system, and the present invention has been completed.

  According to one aspect of the present invention, a wastewater treatment apparatus comprises an activated sludge treatment apparatus for treating purified wastewater discharged by energy gas purification, and a biodegradable aromatic compound discharged by energy gas purification. It has a gist of having an organic substance supply means for supplying to an activated sludge treatment apparatus.

  Moreover, according to one aspect of the present invention, an energy gas purification system uses an energy gas purification apparatus that purifies energy gas and discharges purified wastewater and biodegradable aromatic compounds, and the aromatic compound. The above-mentioned wastewater treatment apparatus is provided for treating the purified wastewater with activated sludge.

  Furthermore, according to one aspect of the present invention, the wastewater treatment method has an activated sludge treatment for treating purified wastewater discharged by energy gas refining, and biodegradation discharged by energy gas refining in the activated sludge treatment. The main point is to supply a functional aromatic compound.

  Further, according to one aspect of the present invention, a method for purifying an energy gas includes a purification step for purifying an energy gas and a biodegradable aromatic compound discharged in the purification step according to the above-described wastewater treatment method. The gist of the present invention is to have a wastewater treatment step of supplying the sludge treatment and treating the purified wastewater discharged in the purification step by the activated sludge treatment.

  According to the present invention, since the function inhibition of activated sludge can be suppressed using the aromatic compound recovered in the energy gas purification process, the introduction of materials from outside the energy gas purification system is not required, and the materials in the system Since the ammonia in the energy gas refining wastewater can be treated effectively, the energy gas refining system can be efficiently configured, and the maintenance and inspection costs of the facilities and the operation cost can be reduced. In addition, it is possible to improve the decomposition rate in the activated sludge treatment for organic substances that are hardly decomposed by microorganisms mixed in energy gas purification wastewater.

It is the schematic which shows the structure of one Embodiment of the energy gas purification system which concerns on this invention. It is a schematic block diagram which shows an example of the waste water treatment apparatus which concerns on this invention.

  Examples of the energy gas include gasified fuel obtained by a gasification process of fossil fuel such as low-grade coal, and synthetic gas obtained by pyrolysis or chemical synthesis of organic materials such as plastic. Such energy gases include tars (aromatic compounds), hydrogen sulfide, ammonia, cyanide gas, hydrogen chloride, carbonyl sulfide, etc., depending on the type, but these by-products are used for use. It is necessary to carry out a purification treatment for removing substances (hazardous components), and the treatment of the refined wastewater accompanying this is also carried out. Regarding the treatment of the above components, chemical, physicochemical or electrochemical treatment methods have been established, respectively, and can be selected and used according to the situation in consideration of the allowable concentration and the like.

  In general, in the energy gas purification process, dust, water-soluble components and oily organic substances can be removed by appropriately combining physicochemical operations such as scrubber water washing, phase separation or coagulation separation, absorption or adsorption. Carbonyl sulfide is chemically converted to hydrogen sulfide and removed by chemical desulfurization or biological desulfurization. As purified wastewater, wastewater containing tars, ammonia, cyanide and the like is generated, and it is necessary to treat such wastewater. Basic gas and acid gas in water can be released from water by adjusting the pH, neutralize the acid gas component by adjusting the wastewater to basic, release ammonia, and release cyanide by oxidation with chlorine or ozone. By decomposing, gaseous harmful components can be removed. Although these methods can efficiently treat ammonia and cyanide, it is necessary to reduce the concentration to a lower level in order to discharge water into the environment. For this, it is considered appropriate to use activated sludge treatment. However, refined wastewater of energy gas has a poor balance between biodegradable (microorganisms are easily decomposed) organic matter and nitrogen (ammonia nitrogen), components that inhibit the function of activated sludge such as cyanide, and chloro groups. In addition, organic compounds that are difficult to decompose for microorganisms such as compounds substituted with sulfo groups, nitro groups, amino groups, etc., and ether compounds can also be contained, so the nitrogen concentration cannot be reduced sufficiently, resulting in dilution with a large amount of water. Necessary.

  Therefore, in the wastewater treatment of the present invention, the function inhibition of activated sludge is suppressed using an aromatic compound (mainly benzene) separated as a light tar component in the energy gas purification process. Aromatic compounds such as benzene separated from energy gas are easily degradable compounds for bacteria, and by supplying this to activated sludge treatment, denitrification reaction of denitrifying bacteria can be activated, Furthermore, the decomposition of the hardly decomposable organic substance is promoted. Since this method makes effective use of substances separated in the energy gas purification process, it can be covered in the energy gas purification system and does not require input of materials from the outside.

  The aromatic compound supplied to the activated sludge in the present invention is a monocyclic aromatic compound having no functional group, including benzene, xylene and toluene, and obtained from an energy gas refining process as a light oil component mainly composed of benzene. Can do. These aromatic compounds, especially benzene, are biodegradable organic substances for activated sludge bacteria and supply energy for degrading biologically indegradable organic substances. Therefore, by adding the above-described biodegradable aromatic compound, acclimation to the inhibitor and the hardly decomposable organic substance is promoted, and the decomposition rate of the hardly decomposable organic substance is improved. The biodegradable aromatic compound is about 1.5 to 15 g-COD / g-N, preferably about 3 to 10 g-COD / g-N, in terms of the mass ratio of COD to ammonia nitrogen contained in the wastewater. When added to wastewater, the function of activated sludge is suitably exerted, and the removal rate by ordinary activated sludge treatment is also treated with a removal rate (COD conversion) of about 80% or more even for a hardly decomposable organic substance having a removal rate of about 50% or less. This improves the cyan density that sludge bacteria can handle. In addition, the improvement of the removal rate of the hardly decomposable organic substance by the addition of the biodegradable aromatic compound is because the acclimatization progresses because sufficient time is given for the metabolism of the hardly decomposable organic substance, so that the long acclimatization time is Degradability stabilizes when removed. Therefore, in actual wastewater treatment, it is desirable to acclimate by mixing an easily decomposable aromatic compound with wastewater containing a hardly decomposable organic substance and repeatedly acting on the activated sludge in advance.

  Hereinafter, a wastewater treatment apparatus and an energy gas purification system that perform treatment of energy gas purification wastewater according to the present invention will be described in detail.

  FIG. 1 shows an embodiment of an energy gas purification system according to the present invention. The energy gas purification system is composed of an energy gas purification device GP and a wastewater treatment device WT, and the purified wastewater discharged when the energy gas is purified in the energy gas purification device GP is treated and cleaned in the wastewater treatment device WT. It releases after becoming.

  The energy gas purification device GP includes a scrubber WS, an electrostatic precipitator DC, a deammonia device AR, a pressurized condenser PC, a cleaning unit CU, a carbonyl sulfide converter CT, and a desulfurization device DS. In this embodiment, the gasification furnace G is used as an energy gas supply source, and high-temperature coal gasification fuel is supplied as energy gas to the energy gas purification device GP. In the scrubber WS, the energy gas is first washed with spray water to remove solid particles and the like, and the gas content at about 500 ° C. is lowered to 100 ° C. or less, so that the tar content (molecular weight 90 to 90%) is contained in the energy gas. (Contains about 280 aromatic compounds) is condensed and separated from the gas and discharged together with the washing water. In addition, water-soluble organic substances such as phenol are also transferred to water, and part of the ammonia contained in the energy gas is absorbed by the washing water. In this embodiment, it is configured so that it can be highly purified using the electrostatic precipitator DC, the deammonia device AR, the pressurized condenser PC, and the cleaning unit CU, and the energy gas that has passed through the scrubber WS is used. Depending on the purpose, after removing ultrafine solid particles, ammonia and aromatic compounds and refining to the required level, the carbonyl sulfide in the gas is treated and supplied as an energy source for the gas turbine T and the like.

  Specifically, first, through the electrostatic precipitator DC, fine solid particles that are not removed by the scrubber WS are collected and removed by charging and adsorption. At this time, a gas cooler (not shown) can be used as necessary in order to adjust the temperature of the energy gas passing through the electrostatic precipitator DC to about 40 to 70 ° C. The energy gas from which the fine particles have been removed is supplied to the deammonia device AR, and the remaining ammonia in the energy gas is transferred to the washing water by being sufficiently washed with the spray water. The wash water that has absorbed the ammonia can be reused by supplying it to the regeneration tower and releasing it using stripping or the like and then refluxing it to the deammonia unit AR. The energy gas that has passed through the deammonia device AR is compressed in the pressure condenser PC, and a component having a boiling point of about 80 to 140 ° C. is condensed and liquefied. The liquid separated from the gas thereby contains an aromatic compound such as benzene, toluene, xylene and water, and the main component of this aromatic compound is benzene. Most of the benzene, toluene and xylene (collectively referred to as BTX) contained in the energy gas passes through the scrubber WS and is collected in the pressure condenser. The energy gas that has passed through the pressure condenser PC is supplied to the cleaning unit CU, sprayed with an organic solvent on the energy gas, and cleaned to absorb the organic compound. Thereby, organic compounds such as residual BTX are removed, and the concentration is lowered. As the organic solvent, for example, an aromatic solvent having low volatility such as methylnaphthalene can be used. Furthermore, if necessary, the residual concentration can be further reduced by passing through a packed bed using an absorbent / adsorbent such as activated carbon capable of absorbing or adsorbing ammonia and organic compounds. Organic solvents and absorbent / adsorbents can be regenerated and reused by conventional methods. The degree of purification from the electrostatic precipitator DC to the cleaning unit CU may be appropriately set to a necessary purification level according to the purpose of use.

  Thereafter, the energy gas is supplied to the carbonyl sulfide converter CT, and a chemical reaction for converting carbonyl sulfide to hydrogen sulfide proceeds. Further, hydrogen sulfide is removed in the desulfurization apparatus DS. When a biological desulfurization apparatus is used as the desulfurization apparatus DS, carbonyl sulfide can be oxidatively decomposed to sulfuric acid by the action of sulfur-oxidizing bacteria, and the carbonyl sulfide converter CT can be omitted. In addition to the energy source of the gas turbine T, the use of the energy gas thus purified includes a fuel source for a power generation system using a fuel cell, a raw material for production of various chemical products, and chemical synthesis.

  On the other hand, the wastewater treatment apparatus WT includes liquid separators LS1 and LS2, a pressure separator PS, an ammonia stripper AM, a cyan decomposition apparatus OX, and an activated sludge treatment apparatus AC. Since the wash water discharged from the scrubber WS as purified wastewater is accompanied by an oil phase composed of condensed organic substances, the water phase is changed to the oil phase (including tar and solid particles that are insoluble in water and exhibit precipitation) in the liquid separator LS1. Is removed. In addition, the aromatic compound discharged as a condensed liquefied product from the pressure condenser PC is also accompanied by moisture, and is separated into a water phase and an oil phase (such as BTX) in the liquid separator LS2. The aqueous phase is supplied to the pressure separator PS together with the waste water discharged from the liquid separator LS1. Since the water phase of the condensed liquefied product supplied to the liquid separator LS2 contains a saturated concentration of BTX, it is preferable to use an oil-water separator with improved separation efficiency as the liquid separator LS2. Oil-water separators include those that promote the coarsening and floating of oily components using filters and lipophilic members, and those that promote the floating of oily components using electrolysis. Good.

  Waste water discharged from the liquid separators LS1 and LS2 is ammonia, water-soluble organic compounds (mono or polyphenols such as phenol, amines, etc.), fine solid particles suspended in the liquid separator, and emulsified organics. Contains compounds, etc., and includes trace amounts of BTX. When the energy gas contains an acidic gas component such as cyan or a basic compound, these can also be contained in the waste water. By supplying such a wastewater to the pressure separator PS and pressurizing it, tar and the like dispersed in an emulsion form agglomerate and float and separate from the aqueous phase. At this time, fine solids are also separated from the aqueous phase. Most of the ammonia is removed and removed from the wastewater discharged from the pressure separator PS after being removed by the ammonia stripper AM. After this, waste water is supplied to the cyanide decomposition apparatus OX, and organic compounds and cyanide are removed by oxidative decomposition. However, in order to reduce the ammonia and organic matter remaining even after these treatments to a level at which water can be discharged. The waste water is supplied to the activated sludge treatment apparatus AC.

  The ammonia stripper AM has a packing that allows liquid or gas to pass through while being packed and held in the tower, and a flood nozzle that submerses the waste liquid on the packing, and the waste water passes through the packing. While flowing down, ammonia is actively released from the wastewater by gas-liquid contact between the wastewater and the atmosphere. The filling is made of a member made of a granular, net-like or porous material, or a member generally used as a filler to increase the gas-liquid contact area such as Raschig ring or Lessing ring. Can be configured. Further, when the waste water discharged from the pressure separator PS is adjusted to basic with an alkaline agent such as an aqueous sodium hydroxide solution before being supplied to the ammonia stripper AM, the solubility of ammonia is lowered and the waste water is easily discharged from the waste water. In this case, the wastewater preferably has a pH of 11 or more. Further, in order to promote the release of ammonia, it is effective to raise the temperature of the waste water. For example, a heater for heating the packing is provided, and the waste water in contact with the packing is preferably 60 ° C. or more, more preferably. Is preferably heated in the range of about 60 to 100 ° C.

  When waste water is sent to the cyanide decomposition apparatus OX, cyan contained in the wastewater is oxidized and decomposed by ozone. As the structure of the ozone oxidizer OX, for example, ozone is blown into stored wastewater, or ozone is brought into gas-liquid contact with wastewater when the wastewater passes through a liquid-permeable filler, and absorbed. Although what was comprised so that it may decompose | disassemble with ozone etc. is mentioned, it is not limited to these, It can deform | transform suitably as needed. When a cooling device for cooling the packing is attached and the waste water is cooled via the packing, the solubility of ozone in the flowing down waste water is improved, and the residence time can be shortened. Depending on the cyan concentration contained in the wastewater, the wastewater temperature can be lowered to increase the absorption rate of ozone into the wastewater. The absorption of gas into water by gas-liquid contact is particularly efficient when the temperature is 10 ° C. or lower.

  By ammonia release and ozone oxidation, the ammonia concentration and cyanide concentration of the wastewater are reduced to about 100 mg-N / L or less and tens of mg-CN / L or less, respectively, and organic substances that are easily decomposed are also oxidized and decomposed. This waste water is supplied to the activated sludge treatment apparatus AC in order to reduce ammonia, phenol, cyan and the like remaining even after the above-described waste water treatment to a level at which water can be discharged.

  In the cyan decomposition apparatus OX, the readily decomposable organic compound in the wastewater is decomposed. Phenols contained in the energy gas refining wastewater are also mostly decomposed through the cyan decomposition apparatus OX, but are not mineralized and remain as organic substances. The energy gas purification wastewater also contains organic compounds that are hardly decomposable for microorganisms. That is, since the organic matter contained in the wastewater supplied to the activated sludge treatment apparatus AC has a high ratio of hardly decomposable compounds, the removal efficiency of the organic matter by the activated sludge is low in the conventional method and is not suitable for discharge as it is. Moreover, since there is a shortage of readily degradable organic matter, activated sludge bacteria cannot act satisfactorily and it is difficult to remove ammonia. Therefore, in order to activate the bacteria of the activated sludge treatment apparatus AC, it is necessary to add an easily decomposable organic compound to the waste water. In the present invention, aromatic compounds such as benzene, toluene, and xylene discharged as a liquefied product in the purification of energy gas are supplied to the activated sludge treatment apparatus AC and used as an organic source for activated sludge bacteria. Usually, organic substances used by microorganisms are biodegradable compounds such as saccharides and lower alcohols, compounds substituted with functional groups such as chloro group, sulfo group, nitro group and amino group, ether compounds, polycyclic aromatics Compounds are organic substances that are difficult to decompose for microorganisms, but monocyclic aromatic compounds without functional groups such as benzene, toluene and xylene (BTX) are relatively biodegradable. It is easily disassembled. Therefore, when activated sludge bacteria denitrify nitrate nitrogen by supplying the oil phase (BTX) separated as a light tar component in the separator LS2 to the activated sludge treatment apparatus AC as a biodegradable aromatic compound. In this way, nitrification and denitrification of ammonia in wastewater proceeds suitably. At this time, the supplied wastewater contains aromatic persistent organic substances, but the supply of BTX, particularly benzene, promotes the acclimation of activated sludge bacteria to the persistent organic substances, It has the effect of increasing the processing speed for decomposing wastewater organic matter and the effect of improving resistance to cyanide.

  As an optimal treatment form to be carried out in the activated sludge treatment apparatus AC, there is an activated sludge treatment by a circulation modification method in which nitrification and denitrification of ammonia nitrogen is performed. Ammonia nitrogen and organic matter can also be treated by adding anaerobic treatment after aeration treatment by the standard activated sludge method, but the required amount of added organic matter increases and the load tends to be excessive, generating excess sludge. The amount becomes enormous. For this reason, in order to perform wastewater treatment efficiently and simply, activated sludge treatment by a circulation modification method is preferable, and the above-mentioned biodegradable aromatic compound is supplied to wastewater subjected to an anaerobic process to advance the denitrification reaction. . As a result, the nitrate nitrogen of the wastewater is reduced to gas and the organic substance concentration is reduced. Residual organic substances are consumed in the subsequent aerobic process, and ammonia nitrogen is nitrified.

  The addition amount of the biodegradable aromatic compound (BTX) supplied to the activated sludge treatment apparatus AC can be appropriately set according to the ammonia concentration of the wastewater as long as the sludge bacteria are not subjected to an excessive organic load. BTX is preferably added at a ratio of about 3 to 10 g-COD / g-N with respect to the ammonia nitrogen of the wastewater. In addition, it is preferable to add a biodegradable aromatic compound at a ratio of a certain level or more with respect to the organic matter in the wastewater in order to increase the decomposition efficiency of the hardly decomposable organic matter, preferably about 5% or more of the organic matter in the wastewater It is preferable that about 10 to 30% (COD conversion) is added so as to be a biodegradable aromatic compound. Although the water solubility of BTX is low, the amount required for the treatment of energy gas purification wastewater can be sufficiently dissolved within the saturation concentration.

  The amount of activated sludge used in the activated sludge treatment is generally 0.2 to 0.6 kg-COD / (kg activated sludge · Day).

  Since the degradation rate of persistent organic substances varies depending on the degree of acclimatization of the bacteria, the time required for anaerobic (denitrification) and aerobic (nitrification) processes is the quality of wastewater (nitrate nitrogen concentration, organic substances) It is preferable to appropriately detect the concentration and ammonia nitrogen concentration) according to the water quality and the acclimation of bacteria, but the activated sludge treatment to which BTX is added also improves the decomposition rate of the hardly decomposable organic substance. The suitability time for the anaerobic process can be generally set to about 10 minutes to 30 hours. The time required for the aerobic process can be generally set to about 30 minutes to 90 hours, although it depends on the supply rate of oxygen and the like.

  As a suitable activated sludge treatment apparatus, the activated sludge treatment apparatus 1 shown in FIG. 2 is mentioned, for example.

  2 includes a denitrification tank 10 in which a denitrification reaction proceeds, a nitrification tank (aeration tank) 20 in which a nitrification reaction proceeds, and a sedimentation tank (separation tank) 30 that separates activated sludge from wastewater. The denitrification tank 10 is equipped with a stirrer 13 for uniformly mixing and dispersing the activated sludge S in the waste water W. The bottom of the nitrification tank 20 is for supplying oxygen (air) to the waste water W. An aeration device 22 is installed, and the activated sludge S is uniformly dispersed in the waste water W by aeration. Further, a pump 21 is provided for returning a part of the waste water after nitrification from the nitrification tank 20 to the denitrification tank 10.

  In this embodiment, the waste water W discharged from the cyan decomposition / oxidation apparatus OX is supplied to the denitrification tank 10 by the pump 11, and the biodegradable aromatic compound (BTX) obtained as a light oil component from the liquid separator LS2 is obtained. It is added to the waste water of the denitrification tank 10 through the pump 12 at a desired ratio, and mixed and homogenized. A preliminary tank may be provided as a front stage of the denitrification tank 10 and used as a storage tank for waste water or a biodegradable aromatic compound. In the denitrification tank 10 to which the waste water W and light oil are supplied, the anaerobic process is started.

  In the denitrification tank 10, the waste water W and the activated sludge S are mixed by the stirring device 13, and the inside of the tank is blocked from the outside air as necessary. However, if the dissolved oxygen from the water surface is negligible, Blocking is not necessary. In this step, nitrate nitrogen in the wastewater W (included in the reflux water from the nitrification tank 20) is reduced to nitrogen and released from the wastewater W by the activity of the denitrifying bacteria, so that the concentration of nitrate nitrogen decreases. . At this time, the easily decomposable aromatic compound added to the wastewater acts as a hydrogen donor for the denitrifying bacteria, and the metabolism of the denitrifying bacteria is promoted, so that the uptake and decomposition of the hardly decomposable organic substances in the wastewater are promoted. Is prompted. Accordingly, the organic substance concentration in the wastewater is also reduced. When nitrate nitrogen runs out, the denitrification reaction stops. The waste water after the denitrification reaction has flowed down to the nitrification tank 20, and the aerobic nitrification reaction proceeds with the oxygen supplied from the aeration apparatus 11, and the ammonia nitrogen in the waste water W is oxidized by nitrifying bacteria and nitrate. Produce. At this time, the consumption of oxygen supplied to the wastewater tends to precede the nitrification bacteria in the denitrification bacteria, and the progress of nitrification tends to start when the consumption of organic matter declines. Therefore, in order to save energy and shorten the reaction time by reducing the amount of aeration (oxygen supply), it is better that the organic matter concentration in the wastewater at the start of the aerobic process is as low as possible. When the amount of the easily decomposable aromatic compound supplied to the waste water of the process is set, the aerobic process proceeds efficiently.

  A part of the waste water W after nitrification flows down to the settling basin 30 through the pipe 23 and settles and separates the activated sludge S, and then the waste water (treated water) is discarded from the pipe 32. Most of the activated sludge S separated in the sedimentation basin 30 is returned to the denitrification tank 10 by the pump 31, and the sludge corresponding to the growth of microorganisms accompanying the wastewater treatment is extracted as excess sludge and discharged out of the system. . By this operation, the sludge concentration in the denitrification tank 10 and the nitrification tank 20 is kept constant.

  As described above, ammonia nitrogen in the wastewater is obtained by repeating the above-mentioned denitrification step, nitrification step, sludge separation, wastewater and return of sludge while continuously supplying new wastewater W to the denitrification tank 10. And organic substances (easily decomposable aromatic compounds and hardly decomposable organic substances) are removed, and wastewater to be treated whose nitrate nitrogen concentration is reduced to an acceptable low concentration is discharged from the sedimentation basin 30 of the activated sludge treatment apparatus. .

  Alternatively, it is also possible to perform the above-described processing operation as a batch-type process in which the function of the tank is sequentially switched as a denitrification tank, a nitrification tank, and a settling tank using a single biological reaction tank by timer control or the like.

  In the above-described wastewater treatment embodiment, treatment such as ozone oxidation, alkali chlorine method, electrolytic oxidation method, and thermal hydrolysis method can be used as cyan treatment. In addition, instead of ammonia stripping, it is possible to use treatment such as a method using combustion in combination with this, a discontinuous point method, a catalytic wet oxidation method, a high temperature oxidation method using sodium hypochlorite, etc. It is. Accordingly, in the wastewater treatment apparatus WT of FIG. 1, the ammonia stripper AM and the cyan decomposition apparatus OX can be appropriately replaced with apparatuses that perform these alternative methods.

  It is obvious that the present invention can be applied not only to the energy gas described above but also to a gas from which BTX aromatic compounds are separated during gas purification. For example, an energy source gasified from biomass is used. There are examples in which the inclusion of an aromatic compound is reported, and such a thing can also be used.

  Hereinafter, with reference to an Example, the processing apparatus of the energy gas refinement | purification wastewater of this invention is demonstrated concretely.

<Treatment 1: Treatment of scrubber wastewater>
Energy gas refining wastewater (scrubber wastewater) is mixed with benzene at a ratio of 90:10 in terms of oxygen demand CODCr ratio due to potassium dichromate. State nitrogen: 300 mg / L) was prepared.

  Using the simulated wastewater as raw wastewater, nitrification and denitrification wastewater was treated by the batch method as follows.

  The amount of activated sludge is 3000 mg / L, the anaerobic process is 60 minutes, the aerobic process is 180 minutes (DO: 7-8 mg / L), and the stationary water is 40 minutes. It was. This wastewater treatment was continued for 2 weeks. During this time, the COD value of the treated wastewater was measured, and the removal rate of organic matter in terms of COD was calculated to be around 60%. Moreover, when the Kjeldahl nitrogen concentration and nitrate nitrogen concentration of the treated wastewater were measured and the nitrogen removal rate was calculated, it was around 50%.

  Further, benzene is mixed with the scrubber wastewater at a ratio of 80:20 in the CODCr ratio to prepare simulated wastewater with 20% benzene having a COD of about 1000 mg-COD / L, and this is used as raw wastewater. When the wastewater treatment was continued for 3 weeks in the same manner as described above, the organic matter removal rate of the wastewater was 70% or more in terms of COD. The nitrogen removal rate at this time was about 60%.

<Treatment 2: Scrubber wastewater treatment>
Prepare benzene 0% simulated wastewater (COD: about 750 mg-COD / L) that does not contain benzene and does not contain organic substances other than CODCr derived from energy gas refined wastewater. When the wastewater treatment was performed, and the removal rate of organic substances in terms of COD conversion of the wastewater after treatment was determined, it was around 50%. The nitrogen removal rate was 30%.

  The biodegradation rate in wastewater containing 100% benzene is 100%, and the biodegradation rate of scrubber wastewater CODCr is 50% as described above. Therefore, the theory when the mixing ratio of benzene is 10% and 20%. When the above biodegradation rate is calculated, it becomes 55% (benzene 10%) and 60% (benzene 20%). When this calculated value is compared with the result of treatment 1, the value of treatment 1 exceeds the calculated value. From this, it is clear that the resolution of persistent organic substances by activated sludge is improved by the addition of benzene. The nitrogen removal ability is also clearly improved by the addition of benzene.

<Treatment of scrubber wastewater>
Simulated wastewater was prepared by mixing energy gas refined wastewater (scrubber wastewater) with a benzene aqueous solution in a ratio of 30%, 50%, 60% or 70% in terms of CODCr ratio. Using a standard activated sludge treatment device consisting of an aeration tank and a sedimentation tank, simulated wastewater was changed sequentially every week under the conditions of wastewater treatment volume: 5.5 L / d and activated sludge volume: 300 mg / L. The treatment was continued while increasing the scrubber wastewater ratio. For each simulated wastewater, the removal rate of organic substances by treatment was calculated in terms of COD. The removal rates were 97% (scrubber water: 30%), 95% (scrubber water: 50%), and 95% (scrubber), respectively. Water: 60%) and 93% (scrubber water: 70%). Considering that the biodegradation rate of the scrubber wastewater CODCr is 50% as described above, it is clear that the addition of benzene improves the decomposition rate of organic matter (refractory organic matter) derived from the scrubber wastewater.

GP: energy gas purification device, WT: wastewater treatment device,
WS: scrubber, CT: carbonyl sulfide converter, DS: desulfurizer,
DC: electrostatic precipitator, AR: deammonia device, PC: pressurized condenser, CU: cleaning unit,
LS1, LS2: liquid separator, PS: pressure separator, AM: ammonia stripper,
OX: ozone oxidizer, AC: activated sludge treatment equipment,
10: Denitrification tank, 20: Nitrification tank, 30: Sedimentation basin, 13: Stirring device,
22: Aeration device, W: Waste water, S: Activated sludge,

Claims (14)

Activated sludge treatment equipment for treating refined wastewater discharged by energy gas refining,
An organic matter supply means for supplying a biodegradable aromatic compound discharged by energy gas refining to the activated sludge treatment device.   The refined wastewater contains ammonia nitrogen and a hardly decomposable organic compound, and the activated sludge treatment device is configured to alternately perform nitrification of ammonia nitrogen and denitrification to convert nitrate nitrogen to nitrogen. The wastewater treatment apparatus according to claim 1, wherein the aromatic compound to be supplied is used in denitrification.   The refined wastewater is an energy gas refined wastewater containing a gasification product of fossil fuel and contains phenol, and the aromatic compound supplied by the organic substance supply means is selected from the group consisting of benzene, toluene and xylene. The wastewater treatment apparatus according to claim 1 or 2, comprising at least one kind.   The said organic substance supply means is a wastewater treatment apparatus in any one of Claims 1-3 which has a liquid separator which removes the water accompanying the said aromatic compound discharged | emitted by energy gas refining from the said aromatic compound.   Furthermore, a stripping device that lowers the ammonia nitrogen concentration of energy gas refining wastewater to 100 mg-N / L or lower, and the cyan concentration of energy gas refining wastewater to a concentration that does not substantially affect the activated sludge treatment. The wastewater treatment apparatus according to any one of claims 1 to 4, further comprising: a cyanide decomposition apparatus, wherein the energy gas refined wastewater is supplied to the activated sludge treatment apparatus via the stripping apparatus and the cyanide decomposition apparatus. . An energy gas purifier for purifying energy gas and discharging purified wastewater and biodegradable aromatic compounds;
The purification system of the energy gas which has a wastewater treatment apparatus in any one of Claims 1-5 which performs the activated sludge process of the said refinement | purification wastewater using the said aromatic compound.   The energy gas purification device has a scrubber device for washing the energy gas with water and a pressure condenser for liquefying the aromatic compound contained in the energy gas, and contains ammonia nitrogen and an organic compound from the scrubber device. The purification system of the energy gas of Claim 6 from which the refinement | purification waste water to discharge is discharged | emitted.   A wastewater treatment method comprising an activated sludge treatment for treating purified wastewater discharged by energy gas refining, and supplying the activated sludge treatment with a biodegradable aromatic compound discharged by energy gas refining .   The refined wastewater contains ammonia nitrogen and a hardly decomposable organic compound, and the activated sludge treatment includes nitrification of ammonia nitrogen and denitrification for converting nitrate nitrogen to nitrogen, and the activated sludge treatment. The wastewater treatment method according to claim 8, wherein the aromatic compound supplied to the tank is used in denitrification.   The refined wastewater is a refined wastewater of energy gas containing a gasification product of fossil fuel, containing phenol, and the aromatic compound contains at least one selected from the group consisting of benzene, toluene and xylene. The wastewater treatment method according to 8 or 9.   The wastewater treatment method according to any one of claims 8 to 10, further comprising a liquid separation step of removing water accompanying the aromatic compound discharged by energy gas purification from the aromatic compound.   Further, stripping for reducing the ammonia nitrogen concentration of the energy gas refining wastewater to 100 mg-N / L or less, and cyan for reducing the concentration of cyanide of the energy gas refining wastewater to a concentration that does not substantially affect the activated sludge treatment. The wastewater treatment method according to any one of claims 8 to 11, wherein the energy gas refined wastewater is treated by the activated sludge treatment after the stripping and the cyanide decomposition. A purification process for purifying the energy gas;
The biodegradable aromatic compound discharged | emitted by the said refinement | purification process is supplied to the activated sludge process according to the wastewater treatment method in any one of Claims 8-12, and the refinement | purification wastewater discharged | emitted by the said refinement | purification process is activated A method for purifying an energy gas comprising a wastewater treatment process for treatment by sludge treatment.   The purification step has a scrubber treatment for washing the energy gas with water and a pressure condensation treatment for liquefying the aromatic compound contained in the energy gas, and the purification step contains ammonia nitrogen and an organic compound. The method for purifying energy gas according to claim 13, wherein the waste water is discharged.

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