JP2013017928A - Wastewater treatment method, and wastewater treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wastewater treatment technology which can cope with a wide change of water quality, and can stably continue removal of ammonia nitrogen and organic matter.SOLUTION: When wastewater includes high-concentration organic matter, the organic matter concentration is reduced by methane fermentation, and anammox treatment or activated sludge treatment is performed thereon based on the ratio of COD to ammonia nitrogen. The wastewater is preliminarily diluted, as needed, to reduce Kjeldahl nitrogen, and drainage water after activated sludge treatment is refluxed and used as dilution water. The wastewater after anammox treatment is subjected to activated sludge treatment.

Description

  The present invention relates to a wastewater treatment method and a wastewater treatment apparatus for purifying wastewater, and in particular, has a wide range of applicable water quality for wastewater treatment in which nitrification and denitrification of ammonia contained in wastewater is caused by the action of microorganisms. The present invention relates to a wastewater treatment method and a wastewater treatment apparatus with high nitrogen and organic substance removal efficiency.

  In the treatment of wastewater using microorganisms, the ammonia contained in the wastewater is converted to nitrogen gas by the progress of oxidation (nitrification) of ammonia nitrogen and denitrification of the oxidized nitrogen (nitric acid, nitrous acid) by bacteria. Can do. This processing method can be classified as follows.

  A) A method of converting ammonia into oxidized nitrogen by nitrifying bacteria using activated sludge, and converting oxidized nitrogen into nitrogen gas using an organic substance such as methanol as an electron donor (for example, the activity of Patent Document 1 below) See Sludge Modification).

  B) A method of converting oxidized nitrogen to nitrogen gas by a group of bacteria that convert ammonia to oxidized nitrogen by nitrifying bacteria and then oxidize sulfur to reduce oxidized nitrogen.

C) Oxidation of ammonia to nitrite nitrogen by ammonia oxidizing bacteria (partial nitrification), and generation of nitrogen gas from ammonia nitrogen and nitrite nitrogen by anammox bacteria belonging to denitrifying bacteria (NH ₄ (++ NO ₂ ⁻ → N ₂ + 2H ₂ O) step to convert ammonia into nitrogen gas (see Patent Document 2 below).

  Among the above processing methods, the processing method of A) is widely spread worldwide, and a highly stable formulation has been established based on many experiences. Since organic matter is required for reductive denitrification of nitrogen, it is not suitable for wastewater with little organic matter. Further, in actual treatment, in general, in order to enable operation only with organic substances contained in wastewater, the wastewater is circulated and applied in a form applied to repeat denitrification treatment and nitrification treatment. . However, in this case, oxidized nitrogen inevitably remains. Therefore, in order to reduce this concentration, it is necessary to increase the ratio of circulating the wastewater, and the repetition rate of the treatment is increased, which increases the operating cost. Moreover, the removal rate of oxidized nitrogen can be increased to about 90% by repeating the treatment by circulation. However, when the treatment is completed, it is necessary to add organic matter to the waste water from the outside, and the organic matter to be supplied Costs.

  Since the treatment method B) requires the addition of sulfur, the cost for using this chemical is required.

  The treatment method of C) does not require expensive chemicals and organic substances, and the oxygen supply amount necessary for the treatment is an amount that oxidizes half of the ammonia nitrogen at the start of the treatment. There is little load. However, in other words, organic matter contained in wastewater cannot be treated, and when applied to wastewater with a high concentration of organic matter, other bacteria are likely to grow. become unable. The nitrogen removal rate is about 90% or less, and the remaining about 10% remains in the wastewater as nitrate nitrogen.

  For this reason, in Patent Document 3 below, the ratio of chemical oxygen demand to the ammonia nitrogen concentration of wastewater (COD / N) is obtained, and in accordance with this value, desorption by anammox bacteria is performed before activated sludge treatment. A wastewater treatment method for determining whether or not to perform a nitriding treatment has been proposed.

JP-A-8-267087 Special table 2001-506535 gazette JP 2008-155085 A

  According to the method of Patent Document 3, wastewater having a high COD / N ratio of 7.0 or more is treated directly by activated sludge treatment, and the COD / N ratio of low organic substance concentration is low. Waste water of 0.3 or less is finally treated by activated sludge treatment after anammox treatment that does not require organic matter, so the treatment method is selected according to the quality of the waste water, and treatment according to the suitability of both treatments It is done efficiently.

  However, in the case of wastewater with extremely high organic matter concentration, even if the COD / N ratio is 7.0 or more, the toxicity when microorganisms come into contact with the wastewater becomes a level that cannot be ignored due to the high ammonia concentration. In order to perform stable treatment, it is necessary to dilute wastewater. In addition, even if the COD / N ratio is 0.3 or less, if the organic matter is at a high concentration, anammox bacteria having a slow growth rate may be driven out by other bacteria, so dilution of waste water is required. . In introducing diluted water, energy consumption for adjusting the temperature to a water temperature suitable for microbial treatment increases.

  In addition, organic matter in wastewater is decomposed into carbon dioxide by activated sludge treatment, but further improvement is desirable from the viewpoint of effective utilization of resources and environmental protection.

  The present invention is capable of efficiently treating organic matter and ammonia nitrogen in wastewater with a high removal rate without using expensive chemicals and organic matter addition, and can cope with a wide range of water quality, and wastewater containing a high concentration of organic matter. It is an object of the present invention to provide a wastewater treatment method and a wastewater treatment apparatus capable of suitably treating the wastewater.

  In addition, the present invention can easily cope with water quality fluctuations of wastewater, can stably remove wastewater ammonia nitrogen and organic matter, and can be converted to a more effective form by treatment of organic matter contained in high concentration. It is an object of the present invention to provide a wastewater treatment method and a wastewater treatment apparatus that can be used.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive research. As a result, the combination of A) activated sludge treatment and C) treatment with anammox bacteria, and further treatment with methanogenic bacteria. By introducing it, it can be used as an energy source by converting high-concentration organic matter into methane, and it can cope with a wider range of water quality, and can cope with a wide range of waste water quality fluctuations, with a high removal rate. It has been found that organic substances and ammonia nitrogen can be removed from wastewater, and the present invention has been completed.

  According to one aspect of the present invention, a wastewater treatment method includes methane fermentation treatment in which organic matter contained in wastewater is subjected to methane fermentation to reduce the concentration of organic matter, and ammonia waste bacteria and anammox bacteria are allowed to act on the wastewater. The gist is to have an anammox treatment for converting ammonia nitrogen into nitrogen gas and an activated sludge treatment for nitrifying ammonia nitrogen and denitrifying nitric acid / nitrite nitrogen by causing activated sludge to act on wastewater.

  Moreover, according to one aspect of the present invention, a wastewater treatment apparatus converts a methane fermentation treatment tank that contains a methane-producing bacterium that methane-ferments organic matter contained in wastewater, and ammonia nitrogen contained in the wastewater into nitrogen gas. It is summarized that it has an anammox treatment tank containing ammonia oxidizing bacteria and anammox bacteria, and an activated sludge treatment tank containing activated sludge that nitrifies ammonia nitrogen contained in wastewater and denitrifies nitrate and nitrite nitrogen. And

  According to the present invention, by incorporating a methane fermentation treatment using methanogenic bacteria, it becomes possible to effectively use organic matter contained in wastewater, and organic matter in wastewater and anammox treatment and activated sludge treatment according to the COD / N ratio Ammonia can be effectively decomposed. In addition, depending on the organic matter concentration and ammonia concentration contained in the wastewater, by appropriately selecting and combining the treatment method from the activated sludge treatment method and the treatment method using anammox bacteria, organic matter and ammonia nitrogen can be efficiently obtained. It can be removed and wastewater can be treated in a wide range of organic substance concentration and ammonia concentration. Therefore, a wastewater treatment method and a treatment apparatus with high treatment efficiency and high applicability are provided. In addition, since a treatment suitable for the nature of the bacteria can be applied, the treatment can be continued without impairing the growth balance of microorganisms. Since it can be carried out without adding expensive chemicals or supplements to the processing system from the outside, it is advantageous in terms of processing cost and energy consumption, and the structure of equipment required for processing is also simple.

It is a flowchart which shows the wastewater treatment method which concerns on this invention. It is a schematic block diagram which shows one Embodiment of the waste water treatment apparatus which concerns on this invention.

  In the treatment method using activated sludge (activated sludge treatment method), denitrifying bacteria that convert nitrate nitrogen to nitrogen gas assimilate organic matter, so if the amount of organic matter is small, the treatment does not proceed and the ammonia concentration in the wastewater The higher the amount, the more organic matter is required. In contrast, in a treatment method using ammonia-oxidizing bacteria and anammox bacteria (hereinafter referred to as anammox treatment method), anammox bacteria produce organic substances when generating nitrogen gas from nitrite nitrogen and ammonia nitrogen. If it is not necessary and the organic substance concentration is high, other bacteria that assimilate this preferentially proliferate, so that the slow-growing anammox bacteria are easily destroyed. Therefore, in the anammox treatment method, it is necessary that the organic matter in the wastewater is relatively small.

  The applicant of the present application has found that the anammox treatment and the activated sludge treatment can be suitably implemented by using an adsorption treatment in which an organic substance contained in wastewater is adsorbed by an adsorbent, and is presented in Patent Document 3. Wastewater with reduced organic matter due to adsorption treatment is treated with ammonia-oxidizing bacteria and anammox bacteria after removing the adsorbent, and then subjected to anammox treatment. The adsorbent that has adsorbed organic matter is put into activated sludge treatment together with wastewater after anammox treatment. To do. As a result, the anammox treatment suitably proceeds with a small amount of organic matter, and the organic matter initially contained in the wastewater is effectively used in the activated sludge treatment. In addition, the nitrate nitrogen remaining after the anammox treatment is denitrified by the activated sludge treatment, and it becomes possible to eliminate the shortage of organic matter in the activated sludge treatment, so that the nitrogen removal rate of the wastewater is further improved. Moreover, since activated sludge can be used as an adsorbent, it does not require special equipment or chemicals, and can be easily implemented using conventional anammox treatment equipment and activated sludge treatment equipment.

  The wastewater treatment in which anammox treatment or activated sludge treatment is performed according to the ammonia concentration and organic matter concentration of the wastewater is excellent in that the treatment can be optimized according to the quality of the wastewater. However, the organic matter in the wastewater is utilized by microorganisms in the wastewater treatment using activated sludge, or is oxidized and decomposed and converted to carbon dioxide. It is not preferable from the viewpoint of effective use of resources and the environment that the entire amount of the organic substance having a high concentration is converted into carbon dioxide in this form. Moreover, when the organic matter density | concentration of waste water is still higher concentration, application will become difficult for activated sludge treatment and anammox treatment.

  The present invention proposes a wastewater treatment method that can deal with wastewater containing a higher concentration of organic matter and that can be effectively used by converting the organic matter to a substance other than carbon dioxide. Although methane fermentation is promising as a method for effectively using high-concentration organic matter, methanogenic bacteria are poisoned by ammonia, and therefore do not work well in wastewater with high ammonia concentration. Therefore, when methane fermentation of wastewater with a high organic matter concentration, ammonia nitrogen concentration (strictly, Kjeldahl nitrogen (Kj-N) concentration including organic nitrogen such as amine that becomes ammonia by biological reaction) is high. Reduces the ammonia nitrogen concentration in advance by dilution of wastewater. In this case, if external water is used, a non-negligible amount of energy is required to warm the water to a temperature suitable for biological reactions, so energy can be saved by recirculating wastewater that has been purified in subsequent wastewater treatment. Is possible.

  That is, in the present invention, methane fermentation treatment is combined with wastewater treatment using anammox treatment and activated sludge treatment, and is improved to be applicable to wastewater with a high organic matter concentration. In order to prevent the poisoning, the methane fermentation treatment, the activated sludge treatment or the anammox treatment is performed after adjusting the wastewater concentration according to the Kj-N concentration of the wastewater. This will be described in detail below.

  The amount of organic matter in waste water is usually evaluated by COD (chemical oxygen demand). Methane fermentation is a reaction in which methane and carbon dioxide are produced from acetic acid, hydrogen, and carbon dioxide produced through hydrolysis and acid generation of wastewater. When the concentration of organic matter is low, methane produced by methane fermentation is converted into water. Since it is almost dissolved and difficult to recover, it is appropriate that the COD value at which methane can be recovered efficiently is 3000 mg-COD / L or more. However, in order to avoid poisoning with ammonia, the Kj-N concentration of the wastewater needs to be 800 mg-N / L or less.

In addition, the activated sludge treatment method uses COD / N ratio [mg-COD / mg-N] (ratio of chemical oxygen demand [mg-O / L] to ammonia nitrogen concentration [mg-N / L] of wastewater. ) Is preferably applied to wastewater having an organic substance concentration of 7.0 or more, and if it is less than 7.0, the reaction is likely to stop midway (see: Water Research 39 (2005), 3715-3726). On the other hand, in the anammox treatment method, a reaction in which anammox bacteria produce nitrogen gas from ammonia and nitrous acid (NH ₄ ⁺ + 1.32NO ₂ ⁻ + 0.066HCO ₃ ⁻ + 0.13H ⁺ → 1.02N ₂ + 0.26NO ₃ ⁻ +0. 066CH ₂ O _0.5 N _0.15 +2.03 H ₂ O, see Appl. Microbiol. Biotechnol. (1998) 50, 589-596), from 1 mole ammonia nitrogen to 0.066 mole cell organic matter CH ₂ O _0.5 N _0.15 is synthesized. Based on this chemical formula, the COD per mole of the cell organic matter is 2.5 × 16 = 40 g, and the COD of the cell organic matter synthesized from 1 mg of ammonia nitrogen is 0.066 × 40/14 = 0.19 [mg-COD / mg-N]. In this regard, since the yield of general activated sludge that assimilate organic matter is about 0.6 [mg-COD / mg-COD], COD / in the case where the growth of anammox bacteria and other bacteria is balanced. When the N ratio is a, 0.6a = 0.19, and a = 0.19 / 0.6≈0.3. Therefore, the anammox treatment method is suitable for wastewater having a COD / N ratio of 0.3 [mg-COD / mg-N] or less, and if it exceeds 0.3, the growth frequency of bacteria other than anammox bacteria Will increase.

  Therefore, based on the COD value and ammonia concentration of wastewater, when the COD / N ratio is 7 or more or 0.3 or less, wastewater treatment may be carried out according to activated sludge treatment or anammox treatment, respectively. In the range where the COD / N ratio is more than 0.3 and less than 7, it is possible to reduce the COD / N ratio to 0.3 or less by adsorbing and removing organic substances by adsorption treatment. A treatment method can be suitably applied.

  Therefore, the wastewater treatment method of the present invention is implemented by suitably combining the above three treatment methods, and the flow thereof will be described below. An embodiment of a wastewater treatment method according to the present invention will be described with reference to FIG.

  First, as shown in the flowchart of FIG. 1, the COD value, which is an index of wastewater Kj-N concentration and organic matter concentration, is measured (step S1). The Kj-N concentration of wastewater (analysis method: see JIS0102244) is the sum of ammonia nitrogen concentration and organic nitrogen concentration. In wastewater, it is usually about 80 to 100% of the total nitrogen concentration. Therefore, the converted value from the total nitrogen concentration may be used, or the ratio between the ammonia nitrogen and the Kj-N concentration of the wastewater may be examined in advance to use the converted value from the ammonia nitrogen concentration.

  Next, it is compared whether the Kj-N concentration of the wastewater is 800 mg-N / L or less (step S2). When the total nitrogen concentration or ammonia concentration is measured in step S1, these may be substituted and the comparison in step S2 may be performed. When it exceeds 800 mg-N / L in step S2, it is diluted to 800 mg-N / L or less (step S3). Since the applicability of the methane fermentation treatment is lost when it is excessively diluted, the amount of water used for the dilution in step S3 is preferably the minimum amount necessary to satisfy the requirement of the Kj-N concentration. By using the wastewater that has been subjected to the activated sludge treatment described later as dilution water, the energy consumed for heating for adjusting the water temperature can be reduced.

  Waste water with a Kj-N concentration of 800 mg-N / L or less is not diluted and is checked for a COD value of 3000 mg-COD / L or more (step S4), and a wastewater with a COD value of 3000 mg-COD / L or more is checked. Performs methane fermentation treatment (step S5), measures the COD value and ammonia nitrogen concentration of the obtained waste water (step S6), and proceeds to the comparison of the COD / N ratio (step S7). By the methane fermentation in step S5, the organic matter concentration of the wastewater is generally reduced to about 1000 mg-COD / L or less, but the ammonia nitrogen does not change, so there is no great variation in the ammonia nitrogen concentration of the waste water.

  If the COD value of the wastewater is less than 3000 mg-COD / L, even if methane fermentation is performed, the generated methane dissolves in water and is difficult to recover. Therefore, the COD / N ratio comparison (process) Proceed to S7).

  The COD value of the wastewater leading to step S7 is less than 3000 mg-COD / L, and the Kj-N concentration is 800 mg-N / L or less. Since Kjeldahl nitrogen is mostly converted to ammonia by biological treatment, the COD / N ratio of the wastewater after step S7 may be the COD / Kj-N ratio based on the Kj-N concentration (below) Is simply described as COD / N ratio).

  The COD / N ratio [mg-COD / mg-N] is obtained from the ammonia nitrogen concentration of wastewater and the COD value that is an index of the amount of organic substances, and it is judged whether the COD / N ratio is 7.0 or more. (Step S7).

  When the COD / N ratio is 7.0 or more, wastewater treatment (activated sludge treatment) using activated sludge is performed (step S8). If the COD / N ratio is less than 7.0, it is determined whether or not the COD / N ratio is 0.3 or less (step S9). If the COD / N ratio is 0.3 or less, the wastewater is treated with wastewater using anammox bacteria ( When the COD / N ratio exceeds 0.3, the anammox treatment is performed after the adsorption treatment (step S11) (step S10). In general wastewater quality, wastewater with a COD / N ratio of 0.3 to 7 can reduce the organic matter concentration so that it becomes 0.3 or less by one adsorption treatment. Includes a step of measuring again the ammonia nitrogen concentration and COD value of the wastewater after the adsorption treatment (step S11) (step S12), and a step of checking whether the COD / N ratio is 0.3 or less (step) S13) can be performed as necessary, and the necessity of repeating the adsorption process is determined based on the result.

  In addition, 7.0 and 0.3 which are the judgment reference values of the COD / N ratio in steps S7, S9 and S13 may be desirably changed depending on the water quality condition and tendency of wastewater. For example, when the organic matter in the wastewater includes those that are difficult to biodegrade, the judgment reference values of the COD / N ratio in steps S7, S9, and S13 are set to be larger than 7.0 and 0.3, respectively. . In the following description, it will be described that the standard values for judgment are 7.0 and 0.3.

  In the wastewater treatment method described above, the wastewater that has undergone the methane fermentation treatment has a COD value that is reduced to 1000 mg-COD / L or less, and in general, the COD / N ratio is easily less than 7.0. Therefore, the waste water that has undergone the methane fermentation treatment tends to be input to the activated sludge treatment through the anammox treatment.

  In the adsorption treatment of step S11, a material capable of physically or chemically adsorbing organic substances such as sludge and powdered activated carbon is brought into contact with wastewater as an adsorbent, and the adsorbent is removed after adsorbing organic substances from the wastewater. Specifically, if necessary, the waste water is agitated to uniformly disperse the adsorbent as necessary, and then the adsorbent is separated by settling separation by standing, centrifugation, etc., and solid-liquid separation or filtration of the supernatant is used. Remove the adsorbent from the wastewater. When using sludge as an adsorbent, the activated sludge recovered after the activated sludge treatment in step S8 can be used, and the activated sludge after the adsorption treatment is denitrified by returning to the activated sludge treatment. It can be used effectively for the activity and growth of bacteria, and nitrification and denitrification of a small amount of ammonia nitrogen contained in sludge is also possible. Even when a carbon material such as activated carbon is used as the adsorbent, it is possible to add carbon material adsorbing organic matter to the activated sludge and use it in combination to enhance the activated sludge adsorption function. Good. The amount of the adsorbent used in the adsorption treatment is appropriately set according to the adsorption capacity. When a carbon material is used, a ratio of about 0.01 to 1 g with respect to 1 g of the activated sludge dry mass is preferable. By the adsorption treatment, wastewater having a COD / N ratio of 0.3 or less is recovered from wastewater having a COD / N ratio of 0.3 to 7.0, and anammox treatment can be applied.

Wastewater having a COD / N ratio of 0.3 or less undergoes partial nitrification (nitritation) and denitrification by the anammox treatment in step S10. That is, ammonia oxidizing bacteria and anammox bacteria are introduced into wastewater, oxygen is supplied in the presence of bicarbonate, and ammonia nitrogen is converted to nitritation and conversion to nitrogen gas. In this process, the oxygen to the waste water is supplied, the reaction of ammonia oxidizing bacteria to convert ammonia to nitrite nitrogen (nitrite ^{_{reduction, 2NH 4 + + 3O 2 →}} 2NO 2 - + 4H + + 2H 2 O) and, de Reaction of nitromophilic anammox bacteria to generate nitrogen gas from ammonia and nitrous acid (NH ₄ ⁺ + 1.32NO ₂ ⁻ + 0.066HCO ₃ ⁻ + 0.13H ⁺ → 1.02N ₂ + 0.26NO ₃ ⁻ + 0.066CH ₂ O _0.5 N _0.15 +2.03 H ₂ O) proceeds, and the treatment is performed in one or two stages depending on the condition setting. Since anammox bacteria have a slow growth rate and are easily driven out when the growth of other bacteria becomes dominant, consideration should be given to stabilizing the activity of anammox bacteria for stable treatment. In order to stabilize anammox bacteria, 1) a method of preventing the destruction of anammox bacteria by suppressing the growth of nitrifying bacteria that nitrate nitrite nitrogen by reducing the pH of the wastewater to 7.2 or less, and 2) The increase in nitrite nitrogen is prevented by adjusting the activity balance of the bacteria or the supply of oxygen so that the nitritation rate of ammonia nitrogen is rate-limiting, and anammox bacteria have a high concentration of nitrite nitrogen. There is a method of avoiding poisoning and inactivation due to. In method 2), partial nitrification and conversion to nitrogen gas proceed simultaneously. Supply control of oxygen is important, and the accuracy of supply control is enhanced by supplying oxygen (air) while confirming the dissolved oxygen concentration of the wastewater under anaerobic conditions. Since the waste water after the anammox treatment does not substantially contain ammonia nitrogen and the organic matter is not consumed and remains, the COD / N ratio exceeds 7.0, and the activated sludge treatment becomes possible. Further, nitrate nitrogen corresponding to about 10% of the initial ammonia nitrogen remains, but the nitrogen content can be sufficiently removed by applying activated sludge treatment together with organic matter.

  The activated sludge treatment in step S8 is a sludge treatment in which activated sludge is brought into contact with waste water to denitrify nitrate nitrogen and nitrify ammonia nitrogen in the waste water. A batch system may be used. In the activated sludge treatment, the denitrification process of oxidized nitrogen proceeds under anaerobic conditions, and the nitrification process of ammonia nitrogen proceeds under aerobic conditions. A large volume of wastewater is adjusted to an anaerobic condition by leaving the contact area with oxygen small by standing or the like, and adjusted to an aerobic condition by supplying oxygen to the wastewater by aeration or the like. In the denitrification process, nitric acid is converted to nitrogen gas by the denitrification bacteria and removed. In the nitrification process under aerobic conditions, organic substances are oxidized and decomposed by aeration, and ammonia is oxidized to nitric acid by the nitrification bacteria. In the nitrification process, activated sludge also takes in phosphate phosphorus in wastewater. If the wastewater contains ammonia, nitric acid corresponding to the initial ammonia concentration remains in the wastewater after these steps, but a part of the wastewater after the nitrification step is returned to the denitrification step for treatment. By being configured to be repeatedly applied, the residual nitric acid concentration of the wastewater discharged from the treatment system decreases. Thereby, in the normal activated sludge treatment, it is possible to reduce the residual nitric acid concentration to about 10% of the initial ammonia concentration. In the present invention, it is further reduced by using the activated sludge used for the adsorption treatment. It is also possible. Moreover, the waste water after a nitrification process can be utilized as dilution water of process S3.

  The wastewater treatment in FIG. 1 can be performed using, for example, a wastewater treatment apparatus as shown in FIG. The wastewater treatment apparatus 1 includes a batch-type methane fermentation treatment tank 2, an adsorption treatment tank 10, an anammox treatment tank 20, a continuous activated sludge treatment tank 30, and a final sedimentation tank 40, and includes a water quality measuring device (illustrated). The methane fermentation treatment tank 2, by switching the switching valves 3 and 11 according to the Kj-N concentration of the wastewater measured by (omitted) and the COD / N ratio determined from the ammonia nitrogen concentration and the COD value, Waste water is supplied to any one of the adsorption treatment tank 10, the anammox treatment tank 20, and the activated sludge treatment tank 30. In order for the switching valves 3 and 11 to be switched automatically, an electromagnetic valve or the like is used as the switching valve 3 or 11, and a control signal based on the Kj-N concentration and the COD / N ratio is supplied using the measured value of the water quality measuring device. An arithmetic processing unit may be provided. The activated sludge treatment tank 30 is divided into an anaerobic tank 30a that performs denitrification treatment and an aerobic tank 30b for nitrification treatment that includes an aeration device 31 for supplying oxygen, and waste water is continuously fed at a constant rate. Although it is continuously processed by supplying it to the anaerobic tank 30a, even if these tanks are used in a batch system, or a single tank batch-type processing tank that performs both anaerobic processing and aerobic processing in stages. It may be. The aerobic tank 30b is an aerobic condition, and the methane fermentation treatment tank 2, the adsorption treatment tank 10, the anammox treatment tank 20, the anaerobic tank 30a, and the final sedimentation tank 40 are anaerobic conditions. An air supply device 22 capable of controlling the speed is provided, and the rate of oxidation of ammonia into nitrous acid by the ammonia-oxidizing bacteria is adjusted by adjusting the air supply rate, that is, the oxygen supply rate. In this embodiment, activated sludge is used as an adsorbent, and the activated sludge having adsorbed organic matter in the adsorption treatment tank 10 is supplied to the activated sludge treatment tank 30 and used as activated sludge that advances denitrification and nitrification. After that, it is separated from the waste water in the final sedimentation tank 40 and returned to the adsorption treatment tank 10 to be used again as an adsorbent. The waste water in the final sedimentation tank 40 is discharged to the outside, but a part of the waste water can be used as dilution water for diluting the raw waste water by refluxing from the switching valve 42.

  When the COD value and the Kj-N concentration are obtained in step S1 of FIG. 1, the necessity of dilution in step S3 is found, and at the same time, the dilution ratio and the Kj-N concentration become 800 mg-N / L or less when diluting. The Kj-N concentration of the wastewater after dilution can be calculated, and it is also predicted whether or not the methane fermentation process in step S5 is selected in step S4. Furthermore, selection of a treatment based on the COD / N ratio when no methane fermentation treatment is selected is also predicted. Therefore, after all the comparison judgments of steps S2, S4, S7, and S9 are performed according to the calculation based on the measurement value, when dilution is performed, the drainage water of the final sedimentation tank 40 through the pipe from the switching valve 42 to the switching valve 11 Is diluted by feeding back with the waste water by the pump 43, and when dilution is not performed, only the waste water may be supplied from the switching valves 3 and 11 to each part. As a result, waste water (or diluted waste water) having a COD value of 3000 mg-COD / L or more and a Kj-N concentration of 800 mg-N / L or less is supplied from the switching valve 3 to the methane fermentation treatment tank 2 through the pipe, Processing is performed. Waste water (or diluted waste water) having a COD value of less than 3000 mg-COD / L and a Kj-N concentration of 800 mg-N / L or less is based on the COD / N ratio, the adsorption treatment tank 10, the anammox treatment tank 20, or activated sludge. It is supplied to one of the treatment tanks 30 via the switching valve 11.

  Methane fermentation in the methane fermentation treatment tank 2 is an anaerobic reaction involving the metabolic processes of multiple types of anaerobic microorganisms including methanogenic bacteria, and is carried out using microorganisms obtained as a self-granulated anaerobic microorganism carrier. It is possible (eg UASB reactor). The wastewater supplied to the methane fermentation treatment tank 2 is subjected to methane fermentation under anaerobic conditions by dispersing microorganisms C such as methanogenic bacteria. Since methane and carbon dioxide are generated by the progress of the reaction, it is appropriately recovered from the upper part of the tank using piping or the like (not shown). The methane fermentation treatment tank 2 has a stirrer 5 for dispersing the microorganisms C in the wastewater as necessary, and a separation tank 6 for efficiently separating the microorganisms C from the treated wastewater is additionally provided. The waste water sent to the separation tank 6 by the pump 4 is allowed to stand to settle and separate the microorganisms C, and the waste water is sent to the switching valve 11 by the pump 7. The separated microorganism C is refluxed to the methane fermentation treatment tank 2 by the pump 8. If the structure of the methane fermentation treatment tank 2 is modified so that the wastewater is allowed to pass through and contacted with the layer on which the microorganism C is fixedly supported, the separation of the wastewater and the microorganism C becomes unnecessary, so the separation tank 6 is omitted. be able to.

  The metabolic processes of microorganisms that constitute methane fermentation include hydrolysis of organic substances (carbohydrates, proteins, lipids), fermentation of hydrolysates (sugars, amino acids, peptides) by acid-producing bacteria, and fermentation by absolute hydrogen-producing acetic acid-producing bacteria. Through conversion of substances (volatile organic acids such as propionic acid and butyric acid) to acetic acid and hydrogen, and conversion of acetic acid and hydrogen to methane and carbon dioxide by methanogenic bacteria. Of these, the reaction that is most likely to be rate-limiting is the conversion of volatile organic acid to acetic acid and hydrogen, so that the microorganisms are not affected by a decrease in pH due to the accumulation of organic acid, etc. The rise is adjusted so that the wastewater is in the range of about pH 6.5 to 8.2 in consideration of suppressing methane fermentation. The water temperature is suitably about 35 to 65 ° C., and is heated as necessary so as to be within this range, preferably about 35 to 55 ° C. Microorganisms in methane fermentation treatment use sulfide and phosphorus as essential nutrients and require Co, Ni, Zn, etc. as trace metals, but the required amount in anaerobic treatment is very small compared to aerobic treatment. These may be supplied from waste water, but if insufficient, they may be replenished as necessary.

  Wastewater having a COD / N ratio exceeding 0.3 (less than 7.0) is supplied from the switching valve 11 to the adsorption treatment tank 10 and is used as an adsorbent using an agitator 12 attached as necessary. Sludge A1 is disperse | distributed, waste water and activated sludge are fully contacted, and the organic matter of waste water is made to adsorb | suck to activated sludge A1. After that, the waste water is allowed to stand and the activated sludge A1 is settled and separated, and the waste water is supplied to the anammox treatment tank 20 through the pipe by the water supply means 13 such as a pump. The activated sludge A1 (including some ammonia) adsorbing organic substances is introduced into the anaerobic tank 30a of the activated sludge treatment tank 30 through a pipe by a supply means 14 such as a pump. The organic matter contained in the activated sludge A1 is used in a reaction in which denitrifying bacteria convert oxidized nitrogen (nitrous acid and nitric acid) into nitrogen gas in the anaerobic tank 30a.

  Waste water having a COD / N ratio of 0.3 or less is supplied to the anammox treatment tank 20, and using a stirrer 21 attached as required, disperses the bacterial agent B containing ammonia bacteria and anammox bacteria, Partial nitrification by ammonia bacteria is advanced by oxygen supplied from the air supply device 22. At this time, the anammox bacteria produce nitrogen gas from the produced nitrite nitrogen and ammonia nitrogen. By this treatment, about 90% of the ammonia in the wastewater is converted into nitrogen gas, and about 1/10 of the ammonia nitrogen concentration remains as nitrate nitrogen. The treated waste water is allowed to stand to settle and separate the bacterial agent B, and is fed to the anaerobic tank 30a of the activated sludge treatment tank 30 through a pipe by a water feeding means 23 such as a pump.

  Waste water having a COD / N ratio of 7.0 or more or waste water after the anammox treatment is supplied to the activated sludge treatment tank 30 and contacts the activated sludge A2 in the anaerobic tank 30a. During this time, denitrifying bacteria ingest organic matter and convert oxidized nitrogen (nitrate ions and nitrite ions) in the wastewater into nitrogen gas. Thereafter, the wastewater is sent to the aerobic tank 30b, the organic matter is oxidatively decomposed by oxygen supplied from the aeration apparatus 31, and the ammonia nitrogen is nitrified by nitrifying bacteria to be converted into nitrate nitrogen. The activated sludge treatment tank 30 further includes water supply means 32 such as a pump in order to return a part of the waste water after the treatment in the aerobic tank 30b to the anaerobic tank 30a through the pipe. Thereby, since the denitrification process in the anaerobic tank 30a is repeatedly performed to wastewater, the final nitric acid concentration of wastewater falls. Wastewater from the aerobic tank 30a is sent to the final sedimentation tank 40 through a pipe by a water supply means 33 such as a pump.

  The waste water supplied to the final sedimentation tank 40 is left still and discharged after the activated sludge A3 is settled and separated. When used as dilution water, it is refluxed by the pump 43 from the switching valve 42. The separated activated sludge A3 is put into the adsorption treatment tank 10 through a pipe by a supply means 41 such as a pump.

  Waste water containing ammonia or adsorbent after adsorption treatment undergoes activated sludge treatment, and oxidized nitrogen converted from ammonia remains. In contrast, waste water that has undergone anammox treatment does not substantially contain ammonia nitrogen, and nitrate nitrogen corresponding to about 10% of organic matter and initial ammonia nitrogen undergoes denitrification and nitrification according to activated sludge treatment. Therefore, it is not necessary to repeat the treatment by refluxing. Therefore, the wastewater after the anammox treatment is substantially treated with nitric acid when treated with activated sludge separately from the wastewater having a COD / N ratio of 7.0 or more in step S7 and the adsorbent subjected to the adsorption treatment in step S11. It can be discharged as wastewater that does not contain water.

  The activated sludge bacteria used in the above-described adsorption treatment oxidize the organic matter adsorbed in the aerobic tank after sufficiently ingesting the organic matter. By repeating this, the bacteria grow and adapt to the environment, and the activated sludge organic matter Improve storage capacity. As a result, the organic matter can remain in the activated sludge even after the nitrification step, and the second denitrification step can be performed without supplying the organic matter when the denitrification step and the nitrification step are repeated. Therefore, when such an activated sludge having a high organic matter accumulation capacity is prepared, ammonia is obtained by providing a plurality of pairs of anaerobic tanks 30a and aerobic tanks 30b in the activated sludge treatment tank 30 of the wastewater treatment apparatus of FIG. Since the residual nitrate nitrogen is removed in the second anaerobic tank even in the wastewater containing the wastewater, it becomes possible to deal with wastewater having all COD / N ratios, and wastewater from which nitrogen has been sufficiently removed can be obtained. In addition, accumulation of a large amount of organic matter in the adsorption treatment also increases the activity of phosphorus-accumulating bacteria, which effectively incorporates the phosphorus component in the wastewater in the aerobic tank, which is also effective in improving the phosphorus removal rate of the wastewater. .

  An example in which wastewater treatment equivalent to the wastewater treatment apparatus of FIG. 2 is continuously performed using a plurality of batch-type treatment tanks is shown below. In this example, the wastewater has a Kj-N concentration of 800 mg-N / L or less, a COD value of 3000 mg-COD / L or more, and the COD / N ratio of the wastewater after methane fermentation is 0. .3 or less. Here, six treatment tanks a to f are used, the treatment tanks a and b are methane fermentation treatment tanks, the treatment tank c is an anammox treatment tank, the treatment tanks d and e are activated sludge treatment tanks, and the treatment tank f is It is divided into roles as a separation tank. Therefore, means for supplying air (oxygen) is attached to the processing tanks c to e.

  In the step (a), the processing tank a is in a state in which a methane fermentation treatment (about 0.5 to 2 days) is started, the processing tank b is in a state in which raw waste water is stored, the processing tank c is in an anammox process, and the processing tank d Indicates a state in which nitrification by activated sludge has been completed, and treatment tank e indicates a process during denitrification treatment by activated sludge. Thereafter, steps (b) to (i) are continued.

  In the step (b), a part of the waste water in the treatment tank d is transferred to an empty treatment tank f to settle and separate sludge (about 1 hour). In the treatment tank c, the anammox treatment is completed, and the bacterial agent is settled and separated (about 20 minutes).

  In the step (c), the processing tank a finishes the methane fermentation and settles and separates the bacterial agent (about 20 minutes). In the treatment tank e, waste water is aerated and nitrification is started.

  In the step (d), the supernatant waste water of the processing tank f is discharged, and the sludge is sent to the processing tank d. The supernatant waste water of the processing tank c is sent to the processing tank d, and the denitrification process is started (about 20 minutes). The supernatant waste water of the processing tank a is sent to the processing tank c, and the anammox process (about 200 minutes) of the processing tank c is started.

  In the step (e), the bacterial agent in the processing tank a is sent to the processing tank b, and the methane fermentation process (about 0.5 to 2 days) is started. The processing tank a which has become empty starts to store raw wastewater.

  In the step (f), the aeration of the treatment tank e is completed, and a part of the waste water is transferred to an empty treatment tank f to settle and separate sludge (about 1 hour). In the treatment tank c, the anammox treatment is completed, and the bacterial agent is settled and separated (about 20 minutes).

  In the step (g), the treatment tank b finishes the methane fermentation and settles and separates the bacterial agent (about 20 minutes). In the treatment tank d, waste water is aerated and nitrification treatment is started.

  In the step (h), the supernatant waste water of the processing tank f is discharged, and the sludge is sent to the processing tank e. The supernatant waste water of the processing tank c is sent to the processing tank e, and the denitrification process is started (about 20 minutes). The supernatant waste water of the processing tank b is sent to the processing tank c, and the anammox process (about 200 minutes) of the processing tank c is started.

  In the step (i), the bacterial agent in the treatment tank b is sent to the treatment tank a, and the methane fermentation treatment (about 0.5 to 2 days) is started. The processing tank b that has become empty starts to store raw wastewater.

  Thereafter, returning to the step (a), the steps (a) to (i) are repeated. In the above, the treatment tank f can be applied so as to be combined with the adsorption treatment as necessary. For example, the steps (d) and (h) are respectively performed as the following steps (d1) and (d2). By changing to steps (h1) and (h2), it is possible to adsorb the supernatant wastewater from the treatment tank a or b in the treatment tank f before the anammox treatment in the treatment tank c.

  In the step (d1), the supernatant wastewater of the processing tank f is discharged, the supernatant wastewater of the processing tank a is sent to the processing tank f, and the adsorption process is started (about 10 to 20 minutes).

  In the step (d2), the supernatant wastewater of the treatment tank c is sent to the treatment tank d, the supernatant wastewater of the treatment tank f is sent to the treatment tank c, and the anammox treatment (about 200 minutes) of the treatment tank c is started. The sludge in the processing tank f is sent to the processing tank d, and the denitrification process is started (about 20 minutes).

  In the step (h1), the supernatant wastewater of the processing tank f is discharged, the supernatant wastewater of the processing tank b is fed to the processing tank f, and the adsorption process is started (about 10 to 20 minutes).

  In the step (h2), the supernatant wastewater of the treatment tank c is sent to the treatment tank e, the supernatant wastewater of the treatment tank f is sent to the treatment tank c, and the anammox treatment (about 200 minutes) of the treatment tank c is started. The sludge in the processing tank f is sent to the processing tank e, and the denitrification process is started (about 20 minutes).

  In this way, wastewater containing high-concentration organic matter that is difficult to handle by activated sludge treatment and anammox treatment can be suitably treated, and an appropriate wastewater treatment procedure can be selected based on the COD / N ratio of the wastewater to select nitrogen components and Wastewater treatment with high organic matter removal rate is implemented.

  As described above, the activity of anammox bacteria is affected by the dissolved oxygen concentration and nitrous acid concentration in the system, resulting in a decrease in activity or poisoning. The treatment proceeds under conditions such that the nitric acid concentration is 20 mg-N / L or less, preferably 5 mg-N / L or less, and the dissolved oxygen concentration is 1 mg-O / L or less, preferably 0.5 mg-O / L or less. This is very important. For this purpose, the nitrite nitrogen produced by the ammonia-oxidizing bacteria is all consumed by the anammox bacteria by controlling the conditions so that the treatment rate of the ammonia-oxidizing bacteria (nitrite-nitrogen production rate) is rate-limiting. It is good to. This includes: a) controlling the supply of oxygen to the wastewater (ie ammonia oxidizing bacteria), and b) the ability of ammonia oxidizing bacteria in the system (the ability to produce nitrite nitrogen) to be the ability of anammox bacteria. (Nitrite uptake capacity) The two factors of adjusting the bacterial balance to be below are factors, and whether the rate of nitrite nitrogen production is rate-limiting or not is determined by measuring the dissolved oxygen concentration of wastewater It can be judged by whether or not the concentration increases. When the oxygen supply rate is low, the nitrite nitrogen production rate is rate-limiting regardless of the bacterial balance, but in the bacterial balance where the processing capacity of ammonia oxidizing bacteria in the system exceeds the processing capacity of anammox bacteria, oxygen supply If nitrite nitrogen exceeds the processing capacity of anammox bacteria due to the increase in nitrite, the nitrite nitrogen concentration immediately rises and poisons. If the capacity of ammonia-oxidizing bacteria is less than the capacity of anammox bacteria, an excess supply of oxygen is detected by increasing the dissolved oxygen concentration of wastewater before nitrite nitrogen exceeding the capacity of anammox bacteria is generated. Is possible. Considering the safety regarding poisoning, it is preferable that the treatment capacity [mol-N / h] of the anammox bacteria is 1.5 times or more than the nitrite nitrogen production capacity [mol-N / h] of the ammonia oxidizing bacteria. In the case of a bacterial balance in which the treatment capacity of ammonia-oxidizing bacteria exceeds the treatment capacity of anammox bacteria, it is desirable that the oxygen supply rate be 0.5 equivalent or less with respect to the treatment capacity of anammox bacteria. By doing so, inactivation of the anammox bacteria can be avoided, so that a preparation step for curing the bacteria and the like is not required, and the processing efficiency is improved. In addition, the growth and activity of anammox bacteria can be stably continued. Since the reaction of partial nitrification and denitrification in the anammox treatment requires bicarbonate ions, a bicarbonate such as sodium bicarbonate is usually added. The base constituting the bicarbonate is not particularly limited as long as it does not inhibit the growth and proliferation of bacteria such as heavy metals. It is preferable to add an amount of 0.1 to 2 moles of bicarbonate per mole of ammonia, depending on the ammonia concentration of the wastewater. However, carbon dioxide in the air can be used, and bicarbonate is not necessarily used when the pH of the wastewater is high. Ammonia-oxidizing bacteria and anammox bacteria may be prepared by culturing bacteria in advance or commercially available. Culture of each bacterium can be appropriately performed by a known technique according to a conventional method, and can be obtained by a known method from sludge of an existing water treatment plant that decomposes ammonia. Ammonia-oxidizing bacteria can be isolated with reference to, for example, the literature of B. Sorriano and M. Walker (J. Applied Bacteriology, 31, 493-497 (1968)). The sludge deposited with the registration number 94987 (December 12, 1987) by the Centraal Bureau voor Schimmelcultures in Baarn, the Netherlands can be used. The amount and activity of each cultured bacterium are examined as follows, and the treatment ability of each bacterium can be understood from these.

(Ammonia-oxidizing bacteria)
Bacterial mass: Wagner M., Rath G., Amann R., Koops H.-P. and Schleifer K.-H., "In situ identification of ammonia-oxidizing bacteria", Syst. Appl. Microbiol. 18 (1995 ), p251-264.
Activity: Grunditz C. and Dalhammar G., "Development of nitrification inhibition assays using pure cultures of nitrosomonas and nitrobacter", Water Research, Vol.35 (2001), Issue 2, p433-440.
(Anamox bacteria)
Cell weight: Schmid M. et al., "Candidatus" Scalindual brodae ", sp. Nov., Candidatus" Scalindua Wagneri ", sp. Nov., Two New Species of Anaerobic Ammonium Oxidizing Bacteria", Syst. Appl. Microbiol. , 26 (2003), No. 4, p529-538.
Activity: Sliekers A. et al., "Completely autotrophic nitrogen removal over nitrite in one single reactor", Water Research, Vol. 36 (2002), Issue 10, p2475-2482.
Hereinafter, the treatment of wastewater according to the present invention will be specifically described with reference to Examples.

  Except for changing the activated sludge tank 30 to a batch-type single tank, the following wastewater treatment was performed using a wastewater treatment apparatus having the same configuration as in FIG. The anammox treatment tank 20 is provided with a measuring device for measuring the dissolved oxygen concentration of the wastewater.

Example 1
A methane fermentation treatment tank 2 containing 4 kg of a methane fermentation microbial agent containing methane-producing bacteria (packed granules for UASB reactor) has a Kj-N concentration of 700 mg-N / L (ammonia concentration of 650 mg-N / L), nitric acid / suboxide. Add 8L of raw waste water with nitric acid concentration 0mg-N / L, COD value 4000mg-COD / L, and stir at 35 ° C to disperse the microbial agent, then react under intermittent anaerobic conditions with gentle stirring As a result, bubbles started to be generated from the wastewater. The reaction was continued for 48 hours while collecting this gas through a pipe, and the microbial agent was settled and separated to measure the ammonia concentration and COD value of the supernatant wastewater. The ammonia concentration was 620 mg-N / L, the COD value was 150 mg-COD / L, and the COD / N ratio was 0.3 or less. 8 L of the supernatant waste water is converted into 2 L of a bacterial agent containing ammonia-oxidizing bacteria and anammox bacteria (treatment capacity of ammonia-oxidizing bacteria: 12 g-N / (L · d) in terms of ammonia consumption rate, treatment capacity of anammox bacteria: in terms of ammonia consumption rate) The anammox treatment tank 20 containing 18 g-N / (L · d)) was charged. About 5 g of methane was obtained from the gas recovered from the methane fermentation tank 2 during the reaction.

When 500 g of sodium bicarbonate was added to the waste water of the anammox treatment tank 20 and stirred to disperse the bacteria, and the dissolved oxygen concentration measuring device was started to measure the dissolved oxygen concentration, 0.1 mg-O ₂ / L It was constant. The pH value of the waste liquid was 7.5. Thereafter, the aeration apparatus was operated to adjust the air blowing rate so that the oxygen supply rate was 0.2 g-O ₂ / (L · d), and aeration of the wastewater was started. The dissolved oxygen concentration slightly increased with the start of aeration, but since then it was almost constant, aeration was continued. 15 hours after the start of aeration, the dissolved oxygen concentration began to rise, so the supply of oxygen was stopped and the wastewater was allowed to stand. After the bacterial sludge settled at the bottom of the tank, the quality of the supernatant wastewater was measured. The ammonia concentration was 0.1 mg-N / L, the nitric acid concentration was 73 mg-N / L, and the nitrite concentration was 0 mg-N / L. L. The COD value was 20 mg-COD / L, and the COD / N ratio was 200. The pH value was 7.0. The supernatant waste water 8L was discharged into an activated sludge treatment tank containing activated sludge (containing water) 42L. The wastewater quality of the activated sludge treatment tank was ammonia concentration: 26 mg-N / L, nitric acid concentration: 18 mg-N / L, and nitrous acid concentration: 0 mg-N / L. The COD value was 53 mg-COD / L, and the pH value was 6.8.

  The waste water in the activated sludge treatment tank was anaerobic, and denitrification was performed for 6 hours with gentle stirring. Thereafter, the aeration apparatus is operated to perform a nitrification treatment under an aerobic condition for 5 hours, 8 L of waste water (20% by volume of the total amount) is discharged from the activated sludge treatment tank to the final sedimentation tank 40, and the activated sludge is settled and separated. . When the water quality of the supernatant was measured, the ammonia concentration was 5.3 mg-N / L, the nitric acid concentration was 15 mg-N / L, and the nitrous acid concentration was 0.1 mg-N / L. The COD value was 5 mg-COD / L, and the pH value was 6.8.

(Example 2)
When the quality of the new wastewater was measured, it was Kj-N concentration 2400 mg-N / L (ammonia concentration 2200 mg-N / L), nitric acid / nitrite concentration 0 mg-N / L, and COD value 5000 mg-COD / L. Therefore, the Kj-N concentration was diluted 3 times so as to satisfy 800 mg-N / L or less. 8 L of this diluted raw wastewater was put into the methane fermentation treatment tank 2 after the treatment in Example 1, and reacted in the same manner as in Example 1. As a result, the supernatant wastewater had an ammonia concentration of 760 mg-N / L, a COD value of 50 mg-COD / L, and the COD / N ratio was 0.3 or less. About 3 g of methane was obtained from the gas recovered from the piping during the reaction. The supernatant waste water 8L was put into the anammox treatment tank 20 in the same manner as in Example 1.

The waste water in the anammox treatment tank 20 was aerated in the same manner as in Example 1 so that the oxygen supply rate was 0.2 g-O ₂ / (L · d), and 15 hours after the start of aeration, the dissolved oxygen concentration Started to rise from 0.1 mg-O ₂ / L, the supply of oxygen was stopped and the wastewater was allowed to stand. The ammonia concentration of the supernatant wastewater was 0.1 mg-N / L, the nitric acid concentration was 73 mg-N / L, and the nitrous acid concentration was 0 mg-N / L. The COD value was 30 mg-COD / L, and the COD / N ratio was 300. The pH value was 7.0. The supernatant waste water 8L was discharged into an activated sludge treatment tank containing activated sludge (containing water) 42L. The wastewater quality of the activated sludge treatment tank was ammonia concentration: 0 mg-N / L, nitric acid concentration: 52 mg-N / L, and nitrous acid concentration: 0 mg-N / L. The COD value was 48 mg-COD / L, and the pH value was 6.8.

  The waste water in the activated sludge treatment tank was anaerobic, and denitrification was performed for 6 hours with gentle stirring. Thereafter, the aeration apparatus is operated to perform a nitrification treatment under an aerobic condition for 5 hours, 8 L of waste water (20% by volume of the total amount) is discharged from the activated sludge treatment tank to the final sedimentation tank 40, and the activated sludge is settled and separated. . When the water quality of the supernatant was measured, the ammonia concentration was 0.1 mg-N / L, the nitric acid concentration was 1.2 mg-N / L, and the nitrous acid concentration was 0.1 mg-N / L. The COD value was 15 mg-COD / L, and the pH value was 6.8.

(Comparative example)
When 8 L of new waste water used in Example 2 was added to the methane fermentation treatment tank 2 without dilution and reacted in the same manner, almost no bubbles were generated in the waste water after 2 hours from the start of the reaction. It was. The amount of methane obtained from the recovered gas was about 0.2 g. Moreover, when the water quality of the supernatant wastewater solution was measured, the ammonia concentration was 1800 mg-N / L, the nitric acid concentration was 0 mg-N / L, and the nitrous acid concentration was 0 mg-N / L. The COD value was 4000 mg-COD / L (COD / N ratio: 2.2), and the pH value was 9.1. This indicates that the bacteria of the methane fermentation microbial agent are poisoned.

  Waste water treatment equipment that can efficiently treat with high purification rate without the need to add organic matter or expensive chemicals is provided, waste water treatment containing high concentration organic matter can be suitably treated, and waste water treatment that supports a wide range of water quality is implemented It becomes possible. Disclosed are a wastewater treatment method and a wastewater treatment apparatus that can easily cope with fluctuations in the quality of wastewater and can stably perform purification treatment.

2: methane fermentation treatment tank, 10: adsorption treatment tank, 20: anammox treatment tank, 30: activated sludge treatment tank, 40: final precipitation tank

Claims (15)

Methane fermentation treatment to reduce the organic matter concentration by methane fermentation of organic matter contained in wastewater,
An anammox treatment in which ammonia-oxidizing bacteria and anammox bacteria are allowed to act on wastewater to convert ammonia nitrogen contained in the wastewater into nitrogen gas;
A wastewater treatment method comprising activated sludge treatment in which activated sludge is allowed to act on wastewater to nitrify ammonia nitrogen and denitrify nitric acid / nitrite nitrogen.   The waste water treatment method according to claim 1, wherein the methane fermentation treatment is applied to waste water having an organic substance concentration of 3000 mg-COD / L or more in terms of chemical oxygen demand and a Kjeldahl nitrogen concentration of 800 mg-N / L or less. .   In the anammox treatment, the COD / N ratio [mg-COD / mg-N], which is the ratio of the chemical oxygen demand to the ammonia nitrogen concentration, is 0.3 or less, and the Kjeldahl nitrogen concentration is 800 mg-N / L or less. The wastewater treatment according to claim 1 or 2, wherein the activated sludge treatment is applied to wastewater having a COD / N ratio of 7.0 or more and a Kjeldahl nitrogen concentration of 800 mg-N / L or less. Method.   The wastewater treatment method according to any one of claims 1 to 3, further comprising a dilution treatment for adjusting the Kjeldahl nitrogen concentration to 800 mg-N / L or less by diluting the wastewater based on the Kjeldahl nitrogen concentration of the wastewater.   When the Kjeldahl nitrogen concentration of the wastewater exceeds 800 mg-N / L, the wastewater is subjected to the dilution treatment in advance, and any one of the methane fermentation treatment, the anammox treatment, and the activated sludge treatment is performed based on the organic matter concentration of the wastewater. The wastewater treatment method according to claim 4.   The wastewater treatment method according to claim 4 or 5, wherein the dilution water used in the dilution treatment is wastewater after the activated sludge treatment.   The wastewater having a COD / N ratio exceeding 0.3 and less than 7.0 has an adsorption treatment for reducing the organic matter concentration of the wastewater by causing an adsorbent capable of adsorbing the organic matter to act. Wastewater treatment method.   The wastewater treatment method according to any one of claims 1 to 7, wherein the activated sludge treatment is performed on the wastewater after the anammox treatment. A methane fermentation treatment tank containing methanogens for methane fermentation of organic matter contained in waste water;
An anammox treatment tank containing ammonia oxidizing bacteria and anammox bacteria that convert ammonia nitrogen contained in wastewater into nitrogen gas;
A wastewater treatment apparatus comprising an activated sludge treatment tank containing activated sludge for nitrifying ammonia nitrogen contained in wastewater and denitrifying nitric acid / nitrite nitrogen.   The wastewater treatment apparatus according to claim 9, further comprising dilution treatment means for diluting wastewater having a Kjeldahl nitrogen concentration exceeding 800 mg-N / L to adjust the Kjeldahl nitrogen concentration to 800 mg-N / L or less.   The wastewater treatment apparatus according to claim 9 or 10, further comprising a switching means for switching the supply of wastewater to any one of the methane fermentation treatment tank, the anammox treatment tank, and the activated sludge treatment tank based on the quality of the wastewater.   The waste water treatment apparatus according to claim 10 or 11, wherein the dilution processing means supplies waste water discharged from the activated sludge treatment tank as dilution water.   Furthermore, the wastewater treatment apparatus in any one of Claims 9-12 which has an adsorption treatment tank which accommodates the adsorbent which can adsorb | suck the organic substance contained in wastewater and can reduce the organic matter density | concentration of wastewater.   The waste water treatment apparatus according to claim 13, wherein the adsorbent includes activated sludge or activated carbon.   The wastewater treatment apparatus according to any one of claims 9 to 14, further comprising water supply means for supplying wastewater discharged from the anammox treatment tank to the activated sludge treatment tank.

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