JP5981096B2 - Wastewater treatment method and apparatus - Google Patents

Description

  The present invention relates to a sewage treatment method for purifying sewage containing human waste and septic tank sludge by a biological nitrification denitrification method, and in particular, relates to a sewage treatment method for stabilizing nitrification denitrification.

  Moreover, this invention relates to the sewage treatment apparatus which enforces such a sewage treatment method.

  Conventionally, for example, as shown in Non-Patent Documents 1 and 2, a sewage treatment method for purifying human waste, septic tank sludge, or sewage containing the sewage by a biological nitrification denitrification method is known. In this type of sewage treatment method, the nitrification step aerobically nitrifies ammonia nitrogen and oxidizes BOD components, and the denitrification step uses organic matter in the sewage or a hydrogen donor such as methanol added externally. Thus, nitrogen removal is performed anaerobically until the generation of nitrogen gas in an oxygen-free or near state.

  In addition, if the ratio of the organic substance density | concentration and the nitrogen density | concentration in the wastewater processed by nitrification denitrification method is high, ie, there are many organic substances, it can denitrify using only the organic substance, and nitrogen removal can be completed. However, when the ratio of organic substances is low, or when the overall concentration of nitrogen or organic substances is significantly lower than the designed value, a hydrogen donor such as methanol is added to the denitrification process as described above, and degassing is performed. It is necessary to assist the nitrogen reaction. Non-Patent Documents 1 and 2 also explain the addition of methanol in the denitrification step.

  The use of hydrogen donors such as methanol described above increases the chemical cost of sewage treatment facilities and increases the amount of sludge generated, thereby increasing the sludge disposal cost. Therefore, it is desired to reduce the amount used. . From such a viewpoint, as an example, in Patent Document 1 and Patent Document 2, an alkali agent is added to sludge generated in a solid-liquid separation tank (precipitation tank) that performs solid-liquid separation of sewage after nitrification and denitrification. A sewage treatment method has been proposed in which the water is returned to the nitrification denitrification step. According to this method, since the sludge generated in the solid-liquid separation tank can be used as a hydrogen donor, the amount of chemicals such as methanol can be reduced.

JP 2007-98279 A Japanese Patent No. 4627403

Human waste processing guidebook, pp240-253, Environmental Technology Study Group (1980) Kazuyoshi Honda et al., “Oxygen Aeration and Urine Denitrification”, pp35-38, Proceedings of the 4th National Urban Cleaning Research Presentation, National Urban Cleaning Conference (1983)

  However, the method described in Patent Document 1 does not clearly indicate the conditions for adding an alkaline agent to sludge. Usually, when an organic substance is used as a hydrogen donor for denitrification, the BOD component is about three times as much as nitrogen, which is an index for securing the necessary amount of organic substance. In addition, when the organic sludge is in an alkaline condition, the soluble BOD concentration can be increased relatively easily. However, since the BOD component of the sludge alkali treatment liquid includes components other than those that can quickly act as a hydrogen donor for denitrification, the BOD concentration and the effect as a hydrogen donor for denitrification do not match, Even if a sufficient amount of BOD component is added, there may be no effect on denitrification. For this reason, if the pH range, treatment time, etc. are set to the optimum conditions for producing the denitrification carbon source, and the composition as a hydrogen donor is not obtained, it will be ineffective or very small.

  Furthermore, when the sludge generated by solid-liquid separation after the nitrification denitrification process is treated with alkali, nitrogen in the sludge is eluted as ammonia nitrogen in addition to organic matter unless alkali solubilization is performed under the optimum conditions. As a whole, there is a problem that the nitrogen load increases.

  On the other hand, in the method described in Patent Document 2, the pH conditions and the sludge residence time after the addition of the alkaline agent are also exemplified, but these conditions are conditions for reducing the amount of surplus sludge generated. However, the effect as a hydrogen donor cannot be exhibited at all under the conditions shown here, particularly the residence time.

  The present invention has been made in view of the above circumstances, and in a sewage treatment method for purifying sewage containing human waste and septic tank sludge by biological nitrification denitrification, hydrogen such as methanol can be used without deteriorating the quality of the treated water. The purpose is to reduce the amount of donor used.

  Moreover, an object of this invention is to provide the sewage treatment apparatus which can implement such a sewage treatment method.

  The sewage treatment method of the present invention uses as a hydrogen donor a manure or septic tank sludge in sewage before being sent to the nitrification / denitrification treatment, and further, a component eluted from the returned sludge as a hydrogen donor. The amount of hydrogen donor used is reduced or can be kept to zero.

Been wastewater treatment method according to claim 1, raw sewage Oyo BiKiyoshi of tank wastewater treatment method comprising nitrification step and the denitrification step nitrifying denitrifying biologically treated wastewater containing at least septic tank sludge of the sludge In order to divide a part of the sewage before being sent to the nitrification denitrification treatment and to elute the denitrification carbon source from the branched sewage , an alkali treatment step of adding an alkali agent to the sewage , and a retention step of staying the dirty water the alkaline agent is added, the wastewater after the residence step and a step of supplying to said denitrification step, in the alkali treatment step, the residence time of sewage over 0.5 hours or less for 2 hours, and, pH of wastewater which accumulated in the alkali treatment step is at 11.6 to 12.5, in the residence step is the residence time of the sewage also the Ru der than 48 hours or more 12 hours .

The above as "wastewater containing at least septic tank sludge of night soil Oyo BiKiyoshi of tank sludge" is raw sewage Oyo least septic tank sludge of BiKiyoshi of tank sludge only, further concentrated, such as those based on It also includes sewage and sludge obtained by pre-treatment.

Wastewater treatment method according to claim 2, night soil Oyo nitrification step and the denitrification step of nitrification denitrification treatment biologically sewage containing at least one of BiKiyoshi of tank sludge, as well as the nitrification denitrification treatment In the sewage treatment method comprising the step of returning the sludge obtained by solid-liquid separation of the subsequent sewage before the nitrification step and the denitrification step, a part of the sludge is branched and the branched sludge is separated from the sludge. In order to elute the carbon source for denitrification, an alkali treatment step of adding an alkali agent to the sludge, a retention step of retaining the sewage obtained by adding the alkali agent to the sludge, and the sewage after the residence step are and a step of supplying a denitrification step, in the alkali treatment step, the residence time of the wastewater is less than 2 hours or more for 0.5 hour, and, pH of wastewater which accumulated in the alkaline treatment step is 11.6 to 12.5 or more , And the in the residence step, the residence time of the sewage is also the Ru der than 12 hours or more 48 hours.

Been wastewater treatment method according to claim 3, in wastewater treatment method according to claim 1 or 2, wherein, when the pH of the wastewater in the retaining step is less than 9, which adding sodium hypochlorite in this wastewater It is .

  In the sewage treatment method of the present invention, the retention step includes a step of partially increasing the solid concentration in the sewage, and the sewage with the increased solid concentration is returned to the alkali treatment step. It is desirable to supply the remaining sewage to the denitrification step.

The sewage treatment method described in claim 4 is the sewage treatment method according to any one of claims 1 to 3, wherein the sewage treatment method has a deodorization step of deodorizing the sewage or sludge atmosphere by alkali cleaning. the alkaline waste water is used for an a alkali treatment step a alkali agent and co.

The sewage treatment method according to claim 5 is the sewage treatment method according to any one of claims 1 to 4, wherein the solid content in the sewage is separated after the retention step , And a crystallization dephosphorization step of recovering phosphorus in the sewage by adding a calcium agent to the sewage after separation . In addition, the above “stage after the residence process” includes not only the stage immediately after the residence process but also the other stage, for example, the latter stage including the nitrification denitrification process of sewage. Shall be.

The sewage treatment method according to claim 6 is the sewage treatment method according to any one of claims 1 to 4, wherein in the alkali treatment step, sewage or sludge to which an alkali agent is added is continuously stirred , in distillation step, it is to stir intermittently wastewater.

Sewage treatment apparatus according to claim 7, human waste Oyo sewage treatment comprising a nitrification unit and denitrification means nitrifying denitrifying biologically treated wastewater containing at least septic tank sludge of BiKiyoshi of tank sludge In the apparatus, a part of the sewage before being sent to the nitrification denitrification treatment is branched, an alkali treatment means for adding an alkali agent thereto, a retention tank for retaining the sewage to which the alkali agent is added, and this the sewage after dwell and means for supplying to said denitrification unit, the alkali treatment means includes an alkali treatment tank for retention of the sewerage, this alkali treatment tank, the residence time of sewage over 0.5 hours 2 In this alkaline treatment tank, an alkaline agent is added in an amount such that the pH of the accumulated sewage is 11.6 or more and 12.5 or less, and the sewage residence time is 12 hours. 48 hours or less Also the in is that we have an effective volume to be.

Sewage treatment apparatus according to claim 8, night soil Oyo nitrification unit and denitrification means for nitrification denitrification treatment biologically sewage containing at least one of BiKiyoshi of tank sludge, after the nitrification denitrification treatment In the sewage treatment apparatus comprising means for solid-liquid separation of the sewage, and sludge return means for returning the sludge obtained by the solid-liquid separation before the nitrification means and denitrification means, the sludge to be returned In order to branch a part and elute the carbon source for denitrification from the branched sludge , an alkali treatment means for adding an alkaline agent to the sludge and a sewage in which the alkaline agent is added to the sludge are retained. and retention vessel, and a sewage means for supplying to said denitrification means after this dwell, the alkali treatment means includes an alkali treatment tank for retention of the sewerage, this alkali treatment tank, the residence time of the sewage Is 0 It has an effective volume of less than or equal to 2 hours or more .5 hours, in this alkali treatment bath, pH of wastewater which accumulated is added the amount of the alkali agent to be 11.6 to 12.5, the residence tank, definitive it the residence time of the sewage is also of that have an effective volume of less than or equal to 12 hours or more 48 hours.

The sewage treatment apparatus according to claim 9 is the sewage treatment apparatus according to claim 7 or 8 , wherein the means for detecting the pH of the sewage retained in the retention tank, and the pH detected by the means is less than 9. If, in which the means for adding the sodium hypochlorite in the sewage is provided.

In the above sewage treatment apparatus is disposed in the retention tank, and means for increasing the solids concentration in the wastewater partially to the alkali treatment means from the residence tank the solids concentration is increased sewage It is desirable that a return means is provided so that sewage other than the sewage whose solid matter concentration is increased is supplied from the retention tank to the denitrification means.

The sewage treatment apparatus according to claim 10 is the sewage treatment apparatus according to any one of claims 7 to 9, wherein deodorizing means for deodorizing the sewage or sludge atmosphere by alkali cleaning, and the alkalinity generated in the deodorization means. drainage, in which the means for supplying the a alkali processing means is provided.

The sewage treatment apparatus according to claim 11 is the sewage treatment apparatus according to any one of claims 7 to 10, wherein means for separating the solid content in the sewage at a stage after the residence tank , and the solid content is And a crystallization dephosphorization means for recovering phosphorus in the sewage by adding a calcium agent to the sewage after separation .

The sewage treatment apparatus according to claim 12 is the sewage treatment apparatus according to any one of claims 7 to 11, wherein the alkali treatment means is a stirring means for continuously stirring sewage or sludge to which an alkali agent is added. has, stagnation Tomeso are those that are provided stirring means for stirring the intermittently wastewater.

In the wastewater treatment method of the present invention, including a portion of the wastewater containing at least septic tank sludge of night soil Oyo BiKiyoshi of tank sludge before being sent to the nitrification denitrification treatment, or at least one of the raw sewage and septic tank sludge the sewage on the addition of the alkaline agent to a portion of the nitrification denitrification treatment and return sludge obtained by solid-liquid separation. Thus supplies the sewage (alkaline processing liquid) in the denitrification step, raw sewage Contact made available organic matter eluted from sewage or returned sludge, comprising at least septic tank sludge of I BiKiyoshi of tank sludge as a hydrogen donor.

Further, by performing the addition of the alkaline agent, the pH of the sewage supplied to the denitrification step, (will be described later and the preferred ranges thereof) by which maintains high over the return time required, excreta and wastewater comprising at least septic tank sludge of purification of tank sludge, or it is possible to more elution promptly utilized ingredients as de窒用carbon source of soluble organic substances in the return sludge, hydrogen the organics It can be used more effectively as a donor. Therefore, according to the sewage treatment method of the present invention, the amount of hydrogen donor such as methanol can be remarkably reduced or reduced to zero, so that the chemical cost of the sewage treatment facility can be remarkably reduced. The sludge disposal cost can be reduced by suppressing the increase in the amount of sludge generated by the hydrogen donor.

  And in the sewage treatment method of this invention, like the method shown by patent documents 1 and 2, the sludge generated by the solid-liquid separation after the nitrification denitrification process is alkali-treated and returned to the nitrification denitrification process. However, unlike those conventional technologies, the processing conditions such as the maintenance time of pH and the residence time of the alkaline processing liquid are optimized, so the organic matter and nitrogen phosphorus components as the carbon source for denitrification are removed from sludge. It can be eluted at an appropriate ratio as a carbon source. Therefore, according to the sewage treatment method of the present invention, it is possible to prevent the problem that the quality of the treated water is deteriorated because the organic substances eluted again are returned to the nitrification denitrification step.

First sewage treatment apparatus of the present invention, sewage treatment apparatus comprising a nitrification unit and denitrification means nitrifying denitrifying biologically treated wastewater containing at least septic tank sludge of night soil Oyo BiKiyoshi of tank sludge , A part of the sewage before being sent to the nitrification denitrification treatment is branched, an alkali treatment means for adding an alkali agent thereto, a residence tank for retaining the sewage to which the alkali agent is added, and this residence Bei give a means for supplying to said denitrification means wastewater after the alkali treatment means includes an alkali treatment tank for retention of the sewerage, this alkali treatment tank, the residence time of sewage over 0.5 hours 2 In this alkaline treatment tank, an alkaline agent is added in an amount such that the pH of the accumulated sewage is 11.6 or more and 12.5 or less, and the sewage residence time is 12 hours. 48 hours or less Since they have effective volume, it is possible to implement the first wastewater treatment method according to the present invention described above.

The second sewage treatment apparatus of the present invention, night soil Oyo nitrification unit and denitrification means for nitrification denitrification treatment biologically sewage containing at least one of BiKiyoshi of tank sludge, the nitrification and denitrification process and hand-stage wastewater you a solid-liquid separation after, the sewage treatment apparatus and a sludge return means for returning to the front of this solid-liquid the nitrification unit and denitrification means sludge obtained by the separation is returned by branching a portion of the sludge, to elute the de窒用carbon source from the branched allowed sludge, formed by addition of an alkali agent in the alkali treatment means and the sludge adding an alkali agent to the sludge wastewater a residence tank for retention of, e Bei and means for supplying the sewage after the dwell to the denitrification unit, the alkali treatment means includes an alkali treatment tank for retention of the sewerage, this alkali treatment tank, 0 sewage retention time It has an effective volume of less than or equal to 2 hours or more .5 hours, in this alkali treatment bath, pH of wastewater which accumulated is added the amount of the alkali agent to be 11.6 to 12.5, the residence tank, definitive it Since the sewage has an effective volume of 12 hours to 48 hours, the second sewage treatment method according to the present invention described above can be implemented.

  Hereinafter, the preferable addition amount of the said alkali agent is demonstrated. Alkaline treatment liquid supplied to the denitrification process can be expected to elute more soluble organic substances as hydrogen donors at higher pH. However, if a large amount of alkaline agent is used to do so, the chemical cost increases. In addition, there is an adverse effect on processing such as pH increase in the nitrification denitrification process. The present inventor examined the conditions of this alkali treatment using several types of human waste and septic tank sludge. From this, it was confirmed that the denitrification rate could be improved.

In order to search for the most cost-effective treatment conditions, a treatment test by adding an alkali agent and a denitrification rate test using the alkali treatment liquid were conducted on the septic tank sludge shown as “test sludge” in Table 1. went. In addition, this test is a model test performed by putting a test sludge in a beaker and adding an alkali agent thereto. Septic tank sludge generally has a wide range of properties, and in this test, septic tank sludge having various concentrations was used. In addition, analysis of septic tank sludge in various locations in Japan revealed that the average values and ranges shown in Table 1 were found, so in actual treatment facilities, SS and BOD were 50 to 200 of the test sludge used in this test. It is thought that sewage in the range of about% will be treated.

Alkaline agent is added to the above test sludge in a predetermined amount to adjust the pH to 4 conditions (conditions 1, 2, 3, 4), and stored at room temperature for 24 hours to simulate the alkali used in the present invention. A treatment solution was prepared. Using these four types of alkali treatment liquids, a denitrification rate test was conducted using activated sludge whose denitrification activity was kept constant by continuous treatment with a nitric acid solution as seed sludge. The amount of alkali treatment liquid added is 10% of the amount of seed sludge, and MLSS of seed sludge is 6,320 mg / l (liter). Table 2 shows the denitrification rate obtained in this test for each condition.

  The denitrification rate of the seed sludge without adding the alkali treatment liquid was 0.73 mg-N / g-SS / h. In contrast, when an alkali treatment solution is added to the seed sludge, the denitrification rate is about 1.1 to 1.2 mg-N / g-SS / h when the amount of alkali agent added is small or medium (conditions 1 and 2). However, it increased to 3.13 mg-N / g-SS / h, which is more than four times that in the case of no addition. Furthermore, in condition 4 where the amount of addition was high and the pH was high, the denitrification rate increased slightly from the above to 3.34 mg-N / g-SS / h. Since the improvement of the ratio is less than 10% as compared with the case of Condition 3, the amount of the chemical used is excessive. Moreover, also in condition 5 which measured the denitrification speed on the same conditions as condition 3 about return sludge, the denitrification speed similarly increased, and it was confirmed that the return sludge works effectively as a denitrification carbon source.

  The pH of the sludge greatly depends on the amount of alkali agent added. Focusing on this pH, in the case of Condition 3, which was most effective for the denitrification rate in consideration of the amount of chemical used, the pH immediately after the addition was 11.63, and thereafter the pH decreases with time. One hour after the addition, the pH was 10.24. In the case of conditions 1 and 2 where the addition amount is small, the pH immediately after addition of the alkaline agent is 9.4 to 10.5, and the pH after 1 hour is 8.8 to 9.7. From this, the pH controlled by the alkali treatment is at least 11.6, which is at least above pH 10.5 immediately after the addition of Condition 2, and preferably the same as the pH immediately after the addition of Condition 3. The pH for 1 hour is 12.5 or less. That is, in the sewage treatment method of the present invention, in order to most effectively improve the denitrification rate in consideration of the amount of chemicals used, the alkali agent addition amount in the alkali treatment step is set to 11.6 or more. It can be said that it is desirable to make the amount 12.5 or less.

In addition, when the same denitrification rate test was conducted using methanol that has been generally used as a denitrification carbon source, the denitrification rate did not improve much even if the amount added was increased, and a maximum of 600 mg / The denitrification rate was 2.13 mg-N / g-SS / h even when 1 was added to increase the BOD / NO ₃ -N ratio by 10 times or more. From this, it can be estimated that according to the present invention, the denitrification rate is improved as compared with the case of using methanol.

  Further, in the case of condition 3, the relationship between pH and denitrification rate with respect to the treatment time after addition of the alkali agent, that is, the residence time of the alkali treatment liquid, was examined using the same septic tank sludge. The examination result is shown in FIG.

  When paying attention to the relationship of FIG. 3, the pH drops sharply from 11.63 one hour after the addition of the alkaline treatment liquid, but drops to 10.2 after one hour, and then gradually decreases. The denitrification rate was almost the maximum in 24 hours, and it did not improve even if it was retained longer. For this reason, the residence time of the alkali treatment liquid is preferably 24 hours, and taking into consideration the property range of the septic tank sludge described above (SS and BOD are about 50 to 200% of the test sludge used in this test), It can be said that it is 12 to 48 hours.

In addition, since the above test is a batch test, the pH is highest immediately after the addition of the alkaline agent and then decreases as the reaction proceeds.However, in actual treatment, sewage is continuously supplied, and the inside of the tank is thoroughly mixed. Since it is in a close state, it is stable under the same pH conditions as the state where the batch treatment was performed for the same time as the sewage residence time. Therefore, Table 3 shows an example of pH change and denitrification rate when the alkali agent is used in the same amount as in condition 3 and the alkali agent is added little by little so that the wastewater pH does not exceed 10.5, and these points are graphed. This is shown in FIG. 10 (the unit of denitrification rate in Table 3 is the same as FIG. 10 and is [mg-N / g-SS / h]).

  At this time, the alkaline agent was added over 9 hours, and the highest pH was 10.4 9 hours after the start of addition, and the others were kept below that. The denitrification rate at this time increased only to 1.18 [mg-N / g-SS / h] at the maximum. If the residence time of the alkali treatment tank is set to 2 days and the residence time is not provided and the amount of the alkaline agent used in the condition 3 is continuously operated, the alkali treatment tank is stable at a pH lower than pH 9 after 47 hours in Table 3. As a result, sewage has never been exposed to high pH conditions and can only achieve a denitrification rate lower than the maximum denitrification rate of 1.18 [mg-N / g-SS / h] obtained by this treatment. It is expected that. From the above, the reaction time (usually the residence time in the alkaline reaction tank) between the sewage and the alkaline agent necessary for adjusting the pH of the alkaline treatment liquid to 10.5 or more, preferably 11.6 to 12.5 is the above pH. It is considered that one hour is necessary, which can be considered that the rate of decrease is fast and the reaction is progressing. Therefore, here again, considering the property range of the septic tank sludge described above and the fact that the denitrification rate after 1 hour after the addition of alkali shown in FIG. The reaction time in the range of 0.5 hours (30 minutes) to 2 hours, and the subsequent residence time of the alkaline treatment liquid in the residence tank may be set to the time obtained by subtracting this reaction time from the above 12 to 48 hours. It can be said that it is desirable to maximize the denitrification rate in the denitrification step.

  Septic tank sludge that has been subjected to alkali treatment (alkaline treatment liquid) is temporarily exposed to extremely high pH conditions, so that the activity of microorganisms there is greatly reduced, but the activity gradually recovers as the pH drops and over time To do. FIG. 4 shows the elapsed time after addition of the alkali treatment liquid in the condition 3 and the nitrification speed of the treatment liquid itself as a ratio of the nitrification speed before the alkali treatment.

  As shown in the figure, the nitrification rate ratio is 10% or less immediately after the addition of the alkaline agent, and the nitrification activity is almost lost, but it recovers with time and is about the same as untreated septic tank sludge after 48 hours. To recover. In other words, if the residence time of the alkali treatment liquid after the addition of the alkali agent becomes long, unless these activities are suppressed, the decomposition activity of the eluted soluble BOD component is also recovered, and the increased soluble BOD component It will be decomposed and the effect on denitrification will disappear.

  FIG. 5 shows the results of examining the increase or decrease in solubility BOD for each pH condition as an indication of the extent of this activity recovery. As shown here, the soluble BOD increases under alkaline conditions, but there is no increase or decrease as the pH decreases, and the soluble BOD component is decomposed when the activity of the microorganism returns to a certain pH or lower. That is, it can be confirmed that the solubility BOD does not increase or decrease from about pH 9, and the decomposition of the soluble BOD component occurs at pH 8 or less.

  Therefore, as long as the pH of the alkaline treatment liquid is maintained at least 8 or more, preferably 9 or more, it can be used for the denitrification step without decreasing the increased concentration of the soluble BOD component. Alkaline agent can be added at a pH of 9 or more as a guide. However, if there is a possibility that excessive addition of alkali agent may affect the treatment efficiency after the denitrification step, sodium hypochlorite is added to the alkali treatment solution. Addition of can suppress a decrease in soluble BOD. From the above, when the pH of the alkaline treatment liquid becomes less than 9, it is desirable to add sodium hypochlorite to the pH to maintain it at 9 or more.

  Here, as a treatment liquid after addition of the alkaline agent, a septic tank sludge having a soluble BOD of 550 mg / l was used as a simulation, and the addition rate when sodium hypochlorite was added to this, and two days at room temperature. The increase / decrease in soluble BOD after the passage is shown in FIG.

  As shown here, the soluble BOD component is decomposed by 300 mg / l or more unless sodium hypochlorite is added, and the soluble BOD is reduced, but sodium hypochlorite is reduced to an effective chlorine concentration of 60 mg / l. Under the added conditions, the soluble BOD component did not decrease and tended to increase further in the range of 125 to 375 mg / l. The sodium hypochlorite used is alkaline, but in this test range, the pH of the alkali treatment solution after addition is 8 or less, and biodegradation is suppressed by the oxidizing power of hypochlorous acid and sludge is acceptable. It seems that the soluble BOD component was increased by solubilization.

  In addition, it can be said that sodium hypochlorite is preferably added in order to suppress biodegradation due to a decrease in pH in the alkali treatment liquid retention tank.

Moreover, phosphate phosphorus can also be eluted from sludge by carrying out the alkali treatment of the septic tank sludge. When the septic tank sludge shown in Table 1 was treated with an alkali, it was confirmed that the phosphorous phosphorus concentration increased by about 4.5 times from 10.9 mg / l to 48.7 mg / l as an example. More specifically, when the alkali agent addition amount is between conditions 2 and 3 in Table 2 and the pH immediately after addition is 11.0, and when the alkali agent addition amount is between conditions 3 and 4 in Table 2, the pH immediately after addition is shown. FIG. 11 shows the result of measuring the concentration of phosphate phosphorus (PO ₄ -P) with respect to the case of 12.5. In FIG. 11, what is indicated by “blank” is the result when no alkaline agent is added, and the phosphorous phosphorus concentration in that case is 50 mg / l. On the other hand, when the pH is set to 11.0 as described above, the phosphate phosphorus concentrations when the pH is set to 12.5 are 108.8 mg / l and 341.8 mg / l. Phosphorus elution can be significantly increased by adding an alkaline agent. Especially in the latter case, most of the phosphorus in the sludge can be eluted. Phosphorus is an element that may be depleted of resources, and in recent years, phosphorus resource recovery facilities at urine treatment plants have begun to operate, but the currently applied crystallization dephosphorization method targets phosphate phosphorus, The phosphorus contained in the product cannot be recovered. Alkali treatment has the effect of eluting phosphorus in sludge, and therefore the amount of phosphorus to be recovered by the crystallization dephosphorization method can be increased by combining the crystallization dephosphorization method.

  In addition, the effect of the alkaline treatment liquid on the denitrification rate was compared by performing a denitrification rate test using only the total amount of the treatment liquid and the centrifugal supernatant. When the entire treatment liquid was added even when only the centrifugal supernatant was added. It was found that up to 97.8% of the denitrification rate can be secured. In addition, SS (floating solids) after the alkali treatment liquid was reduced by about 20% compared to before the treatment, but 80% still remained. On the other hand, by adding an alkali agent again, further soluble BOD Elution of components can be achieved. Therefore, a step of partially increasing the solid concentration is provided in the retention step of the alkali treatment liquid, and the alkali treatment liquid with a small amount of SS is introduced into the denitrification process, while the alkali treatment liquid containing a large amount of SS is returned to the alkali treatment process. This makes it possible to reduce the amount of alkaline agent used by re-elution of the soluble BOD component and returning the residual alkaline agent.

  At the same time, when the septic tank sludge is to be treated in the sewage treatment method of the present invention, this also contributes to stabilization of the treatment. Hereinafter, this point will be described in detail. Compared with surplus sludge and return sludge, septic tank sludge has a very large fluctuation range such as the amount of solids, soluble components, and responsiveness to pH. For this reason, the simple setting of the alkali agent addition rate and the pH control cannot cope with the fluctuation, and there is a possibility that the treatment is excessive or insufficient and the biological treatment is adversely affected. Therefore, if a treatment liquid containing a large amount of solid content is obtained by gravity sedimentation using a weir, and returned to the alkali treatment process, the sludge concentration in the alkali treatment tank is kept constant, and the septic tank While reducing the change in the properties of the sludge, the effect of eluting the unreacted organic matter again can be obtained.

  In the sewage treatment method of the present invention, since there is no circulation of sewage or sludge after the waste water treatment, there is no concern about efficiency reduction. In addition, since the remaining alkaline agent is consumed by taking an appropriate residence time after adding the alkaline agent, there is no need for neutralization in the biological treatment. In addition, although the organic matter is solubilized by the alkaline treatment of the sewage, it has only become easier to be biologically treated earlier within the range of the load that could be sufficiently decomposed by the residence time of the sewage treatment. Since it is first used as a hydrogen donor by introducing it into the process, the required amount of oxygen does not increase and the quality of treated water is not affected.

  Further, when returning sludge is treated in the sewage treatment method of the present invention, the amount of solid matter that does not exceed the amount of surplus sludge is limited to alkaline treatment, preventing reduction in efficiency due to sludge circulation treatment and nitrification. The effects on activity and sludge dehydration characteristics can be minimized.

  In the sewage treatment method of the present invention, when the treatment object is both human waste and septic tank sludge, only the septic tank sludge is to be charged with the alkaline agent, and the treatment amount is also limited to a certain ratio with respect to the whole. Thus, the influence of the alkaline agent on the biological treatment can be minimized. However, there are facilities where human waste and septic tank sludge are mixed, and facilities where the storage tank for human waste and septic tank sludge is common. Processing can be applied.

The schematic block diagram which shows the sewage treatment apparatus by the 1st Embodiment of this invention Schematic configuration diagram showing an apparatus for examining the effects of the present invention Graph showing relationship between residence time of alkaline treatment liquid and denitrification rate Graph showing the relationship between elapsed time after addition of alkaline agent and nitrification rate Graph showing the relationship between the pH of the alkali treatment solution and the increase or decrease in solubility BOD Graph showing the relationship between the amount of sodium hypochlorite added to the alkali treatment solution and the increase or decrease in solubility BOD The schematic block diagram which shows the sewage treatment apparatus by the 2nd Embodiment of this invention Schematic block diagram which shows the wastewater treatment apparatus by the 3rd Embodiment of this invention. The schematic block diagram which shows the sewage treatment apparatus by the 4th Embodiment of this invention Graph showing the relationship between denitrification rate and pH versus residence time of alkaline processing liquid A graph showing the relationship between the pH of the alkali treatment solution and the concentration of phosphate phosphorus (PO ₄ -P)

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing a sewage treatment apparatus 1 according to a first embodiment of the present invention. The sewage treatment apparatus 1 includes a denitrification tank 12 to which a human waste input path 10 and a septic tank sludge input path 11 are connected, a nitrification tank 13 to which sewage subjected to denitrification treatment is supplied in the denitrification tank 12, and the nitrification tank 13 includes a settling tank 14 to which sewage that has undergone nitrification treatment is supplied, and a sludge return path 15 that returns sludge from the settling tank 14 to the denitrification tank 12. In the nitrification tank 13, an air diffuser 16 including an air diffuser panel, an air diffuser, and the like is disposed. Aeration air is supplied to the air diffuser 16 from a blower 17.

  The sewage treatment apparatus 1 receives a septic tank sludge pipe 18 branched from the septic tank sludge input path 11, a sludge pump 19 interposed in the septic tank sludge pipe 18, and a septic tank sludge sent by the pump 19. The alkali treatment tank 20, the retention tank 21 to which sewage water (alkali treatment liquid) 4 subjected to alkali treatment described later in the alkali treatment tank 20 is supplied, and the alkali treatment liquid 4 retained in the residence tank 21 for a predetermined time are described above. A pipe 22 for supplying to the denitrification tank 12 and an alkaline processing liquid supply pump 23 interposed in the pipe 22 are provided.

  Further, the sewage treatment apparatus 1 includes an alkaline agent storage tank 25 that stores the alkaline agent 24, an alkaline agent supply pump 26 that supplies the alkaline agent 24 into the alkaline treatment tank 20, a pipe 27, and sodium hypochlorite 28. A sodium hypochlorite storage tank 29, a sodium hypochlorite supply pump 30 for supplying the sodium hypochlorite 28 into the retention tank 21, and a pipe 31.

  The alkaline treatment tank 20 is provided with a stirrer 32 for stirring the alkaline treatment liquid 4 and a pH meter 33 for measuring the pH of the alkaline treatment liquid 4. The retention tank 21 is also provided with a stirrer 34 for stirring the alkaline treatment liquid 4 staying there and a pH meter 35 for measuring the pH of the alkaline treatment liquid 4. A dam 36 is provided in the retention tank 21, one end of the sewage return pipe 37 is connected to the vicinity of the bottom of the retention tank 21 on the upstream side of the weir 36, and the other end is connected to the alkali treatment tank 20. Yes. A sewage return pump 38 is interposed in the middle of the sewage return pipe 37.

Hereinafter, the operation of the sewage treatment apparatus 1 will be described. In the sewage treatment apparatus 1, the denitrification tank 12 is supplied with human waste introduced from the human waste input path 10 and septic tank sludge input from the septic tank sludge input path 11. Wastewater containing these human waste and septic tank sludge (which, septic tank sludge may only include one of the raw sewage Oyo BiKiyoshi of tank sludge) 2 is subjected to a denitrification step in a denitrification tank 12. That is, here, the organic matter in the sewage 2 is used as a hydrogen donor, and nitrogen removal is performed anaerobically or in a state close to it until the generation of nitrogen gas.

  The sewage 2 that has undergone the denitrification process is then subjected to a nitrification process in the nitrification tank 13. That is, aeration is performed here, and nitrification of ammonia nitrogen and oxidation of BOD components are performed aerobically.

  The sewage 2 that has undergone the above-described nitrification denitrification step is then sent to a settling tank 14 where the solid components in the sewage 2 are precipitated and the supernatant is discharged. The sludge (solid component) precipitated in the settling tank 14 is collected, and a part thereof is returned to the denitrification tank 12 through the sludge return path 15.

  The above is the same as each process in the sewage treatment method by a conventionally known biological nitrification denitrification method. Next, assistance in the denitrification reaction according to the present invention will be described. A part of the septic tank sludge input from the septic tank sludge input path 11 is supplied to the alkali treatment tank 20 by the sludge pump 19 through the septic tank sludge pipe 18. Further, the alkaline agent 24 stored in the alkaline agent storage tank 25 is supplied to the alkaline treatment tank 20 through a pipe 27 by an alkaline agent supply pump 26. Thereby, the alkali treatment liquid 4 in which the alkaline agent 24 is added to the septic tank sludge is obtained.

  In addition, the effective volume of the alkali treatment tank 20 is set to a value in which the residence time of the alkali treatment liquid 4 is in the range of 30 minutes to 2 hours described above. The amount of sewage to which the alkaline agent 24 is added is preferably about 5 to 30% of the total amount of sewage to be treated.

  At this time, the stirrer 32 is continuously operated, and the alkaline agent 24 is uniformly added. Further, the pH of the alkaline treatment liquid 4 is measured by the pH meter 33, and the amount of the alkaline agent 24 added by the alkaline agent supply pump 26 is controlled so that the pH falls within the range of 11.6 to 12.5 as described above. . This control may be performed by appropriately using conventionally known means.

  The alkaline treatment liquid 4 is then sent to the retention tank 21 where it is retained for a predetermined time. The effective volume of the residence tank 21 is set to a value that is a time obtained by subtracting the residence time in the alkali treatment tank 20 from 12 to 48 hours as described above. In other words, the effective volumes of the alkali treatment tank 20 and the retention tank 21 are set to values at which the residence time of the alkali treatment liquid 4 is 12 to 48 hours. In addition, the alkali treatment tank 20 and the retention tank 21 may be comprised from one common tank.

  The alkaline treatment liquid 4 retained in the retention tank 21 is supplied to the denitrification tank 12 by the alkaline treatment liquid supply pump 23 through the pipe 22. By doing so, the organic matter eluted from the septic tank sludge can be used as a hydrogen donor in the denitrification step. Furthermore, since the alkaline agent 24 is added to increase the pH of the alkali treatment liquid 4, more of the soluble organic matter in the septic tank sludge can be eluted, so that the organic matter can be used more effectively as a hydrogen donor. It is available. Therefore, in this sewage treatment apparatus 1, it is not necessary to use a hydrogen donor such as methanol at all. Therefore, the chemical cost of the sewage treatment facility is remarkably reduced, and the amount of sludge generated by the externally added hydrogen donor is further reduced. It is possible to reduce the sludge disposal cost by suppressing the increase in the amount of wastewater.

  And in this sewage treatment apparatus 1, since the sludge generated by the solid-liquid separation after the nitrification denitrification process is not alkali-treated and returned to the nitrification denitrification process, the organic matter stabilized through the nitrification denitrification process Is not eluted again. Therefore, according to the sewage treatment apparatus 1 of the present embodiment, it is possible to prevent the problem that the quality of the treated water is deteriorated because the organic substances eluted again are returned to the nitrification / denitrification step.

  In addition, the weir 36 provided in the residence tank 21 fulfill | performs the effect | action which raises the solid substance concentration of the alkaline processing liquid 4 partially in the upstream. A part of the alkali treatment liquid 4 with the solid matter concentration thus increased is returned to the alkali treatment tank 20 by the sewage return pump 38 through the sewage return pipe 37. By returning the alkali treatment liquid 4, the sludge concentration in the alkali treatment tank 20 is kept constant to reduce the change in properties of the septic tank sludge, and the effect of eluting unreacted organic substances again is obtained. In order to more reliably obtain the solid-liquid separation action of the weir 36 that produces the above effects, it is desirable to operate the stirrer 34 of the retention tank 21 intermittently.

  In this embodiment, the pH of the alkali treatment liquid 4 in the retention tank 21 is measured by the pH meter 35. When this pH is less than 9, the sodium hypochlorite supply pump 30 is operated to perform the alkali treatment. Sodium hypochlorite 28 is added to the liquid 4. Thereby, as above-mentioned, the fall of soluble BOD can be suppressed. In addition, since the biodegradation starts in the residence tank 21 of the alkaline treatment liquid 4 due to a decrease in pH, it is desirable to add sodium hypochlorite 28 to suppress this. In addition, it is preferable to employ | adopt the value when the stirrer 34 operated intermittently is drive | operated and the alkali treatment liquid 4 is equalized | homogenized as the pH measurement value of the pH meter 35. Moreover, the operation control of the sodium hypochlorite supply pump 30 may be performed by appropriately using conventionally known means.

  Next, a sewage treatment apparatus according to a second embodiment of the present invention will be described with reference to FIG. In FIG. 7, the same elements as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted unless necessary (the same applies hereinafter).

  Compared with the sewage treatment apparatus 1 shown in FIG. 1, the sewage treatment apparatus 100 of the present embodiment is basically provided with a means for deodorizing the atmosphere of the sewage 2, and the alkaline wastewater generated there together with the alkaline agent 24 is subjected to an alkali treatment. It is different in that it is being used for. That is, in this apparatus, for example, the air in contact with the sewage 2 in the nitrification tank 13 is sucked by the fan 101 and first sent to the acid cleaning tower 103 through the duct 102 and subjected to deodorizing treatment by acid cleaning, and then the duct. It is further sent to the alkali cleaning tower 105 via 104, where it is deodorized by alkali cleaning, and then discharged from the duct 106 to the atmosphere.

  A cleaning liquid 108 such as sulfuric acid or hydrochloric acid stored in the cleaning liquid storage tank 107 is supplied to the acid cleaning tower 103 through a pipe 110 by a cleaning liquid supply pump 109. The air sent to the acid cleaning tower 103 through the duct 102 comes into contact with the cleaning liquid 108 flowing down in the acid cleaning tower 103. Therefore, odorous components such as ammonia and trimethylamine contained in the air are neutralized and deodorized. The cleaning liquid 108 that has flowed down to the bottom of the acid cleaning tower 103 is returned to the upstream side of the acid cleaning tower 103 through the pipe 112 by the cleaning liquid circulation pump 111 and reused.

  The alkaline cleaning tower 105 is supplied with an alkaline cleaning liquid 118 such as a sodium hydroxide aqueous solution or a sodium hypochlorite aqueous solution stored in a cleaning liquid storage tank 117 through a pipe 120 by a cleaning liquid supply pump 119. After the acid cleaning, the air sent to the alkali cleaning tower 105 through the duct 104 comes into contact with the cleaning liquid 118 flowing down in the alkali cleaning tower 105. Therefore, odorous components such as hydrogen sulfide and methylcaptan contained in the air are neutralized and deodorized. The cleaning liquid 118 that has flowed down to the bottom of the alkali cleaning tower 105 is returned to the upstream side of the alkali cleaning tower 105 by the cleaning liquid circulation pump 121 through the pipe 122 and is reused.

  The alkaline cleaning liquid 118 flowing down to the bottom of the alkali cleaning tower 105 is partly drained from the bottom of the cleaning tower or the cleaning liquid circulation line. This alkaline drainage is supplied to the alkali treatment tank 20 through the pipe 123, and the alkaline agent. 24 and the above-described alkali treatment. As described above, the cleaning liquid 118 is used for neutralizing hydrogen sulfide, methylcaptan, and the like, but normally, the cleaning liquid 118 is not completely neutralized completely, so that an alkaline component remains in the waste water. If such alkaline drainage is used for alkali treatment together with the alkaline agent 24, the amount of the alkaline agent 24 used can be reduced, which is economical.

  Next, a sewage treatment apparatus according to a third embodiment of the present invention will be described with reference to FIG. The sewage treatment apparatus 200 of the present embodiment is basically different from the sewage treatment apparatus 1 shown in FIG. 1 in that a means for collecting phosphorus in the septic tank sludge is provided. That is, in the present apparatus, the alkali treatment liquid 4 that has been retained in the retention tank 21 for a predetermined time is then sent to a membrane separation tank (solid-liquid separation tank) 201, and the alkali treatment liquid 4 is separated from the membrane separation tank 201. The alkali treatment liquid 4 sucked by the pump 205 through the membrane 202 and permeated through the separation membrane 202 to remove solid components is sent to the crystallization dephosphorization tank 209 through the pipe 206.

  An air diffuser 203 including an air diffuser panel and an air diffuser is disposed at the bottom of the membrane separation tank 201. Further, a blower that supplies air for preventing clogging of the separation membrane 202 to the air diffuser 203 is provided. 204 is provided. The alkaline treatment liquid 4 that has not permeated the separation membrane 202 of the membrane separation tank 201 is sent to the denitrification tank 12 through the pipe 208 by the pump 207. The effect | action by the alkali treatment liquid 4 sent in this way is the same as that in the above-mentioned embodiment.

  The alkaline treatment liquid 4 sent to the crystallization dephosphorization tank 209 is provided for phosphorus recovery there. That is, the calcium agent 212 stored in the calcium agent storage tank 213 is introduced into the crystallization dephosphorization tank 209 through the pipe 215 by the calcium agent supply pump 214. As a result, phosphorus that was present in the alkali treatment liquid 4, that is, that was present in the septic tank sludge, is deposited in the form of calcium phosphate and can be recovered.

  In the crystallization dephosphorization tank 209, the alkaline treatment liquid 4 and the calcium agent 212 are stirred by the stirrer 211 while the liquid flow is controlled by the baffle plate 210. The alkaline treatment liquid 4 after receiving the phosphorus recovery treatment is sent to the pipe 208 via the pipe 216 and sent to the denitrification tank 12 together with the alkaline treatment liquid 4 from the membrane separation tank 201.

  If phosphorus existing in the septic tank sludge can be recovered as described above, it can be effectively used as a resource. In this embodiment, the septic tank sludge is not sent to the phosphorus recovery process as it is, but the septic tank sludge (alkali treatment liquid 4) that has been subjected to the alkali treatment having a phosphorus elution effect is used for phosphorus recovery. Recovery efficiency can be obtained.

  Next, a sewage treatment apparatus 300 according to a fourth embodiment of the present invention will be described with reference to FIG. In the first to third embodiments described above, a part of the septic tank sludge before being put into the denitrification tank 12 is branched, and an alkali agent is added thereto, and then supplied to the denitrification process after residence. However, in the present embodiment, instead of the septic tank sludge, a return sludge obtained by solid-liquid separation of nitrification denitrification wastewater is used. This is different from the embodiment.

  That is, in this embodiment, as shown in FIG. 9, a part of the sludge return path 15 similar to that shown in FIGS. 1, 7 and 8 is branched, and the branched sludge return path 15 feeds the sludge pump 19. It is connected to the alkali treatment tank 20 via The configuration of supplying the alkali treatment liquid 4 to the denitrification tank 12 from the retention tank 21 and the subsequent retention tank 21 and the retention tank 21 is basically the same as in the first to third embodiments.

  Therefore, in this configuration, the organic matter eluted from the returned sludge can be used as a hydrogen donor in the denitrification step. Furthermore, by adding the alkaline agent 24 to increase the pH of the alkaline treatment liquid 4, it is possible to elute more of the soluble organic matter in the returned sludge, so that the organic matter can be used more effectively as a hydrogen donor. It is available. Accordingly, this sewage treatment apparatus 300 also uses no hydrogen donor such as methanol, reduces the chemical cost for sewage treatment, and further suppresses the increase in the amount of sludge generated by the externally added hydrogen donor. Disposal cost can be reduced.

  In the present embodiment, as in the third embodiment, phosphorus existing in the septic tank sludge and the like is recovered, but the configuration for that is the configuration in the third embodiment. It is different. This will be described below.

  That is, in this embodiment, a separation membrane 202 similar to that in FIG. 8 is disposed in the nitrification tank 13, and sewage in the nitrification tank 13 is sucked by the pump 205 through this separation membrane 202 and passes through the pipe 206. It is sent to the crystallization dephosphorization tank 209. Therefore, in this configuration, phosphorus is precipitated and collected by the crystallization dephosphorization tank 209 from the sewage from which the solid component has been removed by passing through the separation membrane 202, that is, from the septic tank sludge and manure. The configuration for phosphorus precipitation and recovery is the same as that in FIG. That is, when the calcium agent 212 stored in the calcium agent storage tank 213 is charged into the crystallization dephosphorization tank 209, phosphorus is precipitated and recovered in the form of calcium phosphate.

  Here, the pH of the sewage in the nitrification tank 13 varies depending on conditions such as the pH and amount of the alkaline treatment liquid 4 supplied to the denitrification tank 12, but depending on these conditions, the pH of the sewage is increased. It is also possible to elute most of. By doing so, the phosphorus concentration in the sewage sent to the crystallization dephosphorization tank 209 can be made sufficiently high, and the amount of phosphorus recovered by the crystallization dephosphorization tank 209 can be greatly increased.

  Next, as an example of the present invention, the results of a treatment experiment in which an alkaline treatment liquid was introduced into a continuous denitrification apparatus will be described. FIG. 2 is a schematic configuration diagram showing the sewage treatment apparatus 50 used in this experiment. The sewage treatment apparatus 50 includes a denitrification tank 51, a membrane separation tank 52 to which sewage treated in the denitrification tank 51 is supplied, a pipe 53 connected to the membrane separation tank 52, and the pipe 53 And a pump 55 that sucks the sewage in the membrane separation tank 52 through the separation membrane 54.

  The denitrification tank 51 is provided with an agitator 56 for agitating the sewage staying there. On the other hand, an air diffuser 57 composed of an air diffuser panel, an air diffuser and the like is disposed at the bottom of the membrane separation tank 52, and further, air for preventing clogging of the separation membrane 54 is supplied to the air diffuser 57. A blower 58 is provided. One end of a sludge return pipe 59 is connected to the membrane separation tank 52, and the other end is connected to the denitrification tank 51. A sludge return pump 60 is interposed in the sludge return pipe 59.

  Further, the sewage treatment apparatus 50 stores a nitrate solution storage tank 62 that stores a nitrate solution 61, a nitrate solution supply pump 63 that supplies the nitrate solution 61 into the denitrification tank 51, a pipe 64, and an alkaline treatment liquid 65. An alkali treatment liquid storage tank 66, an alkali treatment liquid supply pump 67 for supplying the alkali treatment liquid 65 into the denitrification tank 51, and a pipe 68 are provided.

  In the sewage treatment apparatus 50, the nitrate solution 61 to be treated is subjected to denitrification treatment in the denitrification tank 51, and then solid-liquid separated by the separation membrane 54 of the membrane separation tank 52, and the treated water is sucked and discharged by the pump 55. Is done. The sludge (solid matter component) separated in the membrane separation tank 52 is returned to the denitrification tank 51 by the sludge return pump 60 through the sludge return pipe 59.

  The alkali treatment liquid 65 was prepared by batch treatment for the septic tank sludge shown in Table 1. The alkali agent addition rate with respect to the sludge amount was 7.2 g / l, and the pH was maintained at 11.6 or more for 1 hour after the addition of the alkali agent, and then the alkali treatment liquid 65 was left at room temperature for 23 hours. Since the pH was about 10 at this time, sodium hypochlorite was not added. This alkali treatment liquid 65 was put into the alkali treatment liquid storage tank 66 of FIG. 2 and the denitrification effect by continuous denitrification was evaluated.

  This sewage treatment apparatus 50 continuously injects a nitrate solution 61 having an N component of 100 mg-N / l into a denitrification tank 51 and separates it into a solid-liquid separation by a separation membrane 54 while circulating between the membrane separation tank 52 and processing. It is the structure which obtains water, Thereby, the effect on the denitrification reaction realizable by this invention can be confirmed. Septic tank sludge was used as the seed sludge, and methanol was used in place of the alkali treatment liquid 65, the operation was performed for several months, and after acclimatization, data was collected when the alkali treatment liquid was added.

The denitrification tank 51 has a capacity of 3 l (liter), the membrane separation tank 52 has a capacity of 0.8 l, and the nitrate solution 61 is treated at about 5.5 l / day. Then, methanol or an alkali treatment liquid 65 as a denitrification carbon source was added to the denitrification tank 51 at a rate of about 0.8 l / day. The amount returned from the membrane separation tank 52 to the denitrification tank 51 was set to about 6 times the amount of treated water. The results are shown in Table 4 for RUN1 using methanol and RUN2 using alkaline treatment liquid 65.

In RUN1 using methanol, the removal rate of nitrate nitrogen was only 45% even though the BOD / NO ₃ -N ratio was sufficiently high at 9.0. On the other hand, in RUN2 using the alkali treatment liquid 65, although the BOD / NO ₃ -N ratio was 3.5, which was lower than that of methanol, the nitrate nitrogen removal rate was 75% and a good denitrification effect was obtained.

  From the above, it was confirmed that if the alkaline treatment liquid of septic tank sludge or return sludge is used according to the present invention, the amount of methanol used in the nitrification denitrification treatment can be reduced and stable nitrogen removal can be realized.

  The biological nitrification denitrification method is widely used as a treatment method for sewage and industrial wastewater as well as human waste treatment. It is not necessary to add a denitrification carbon source if the ratio of the BOD component to be treated and the nitrogen component is high, but if the ratio of BOD is low, it is common to add a denitrification carbon source such as methanol. . The present invention can be applied to a treatment facility using these methanol.

DESCRIPTION OF SYMBOLS 1, 50, 100, 200, 300 Sewage treatment apparatus 4, 65 Alkaline treatment liquid 10 Human waste input path 11 Septic tank sludge input path 12, 51 Denitrification tank 13 Nitrification tank 14 Sedimentation tank 15 Sludge return path 18 Septic tank sludge pipe 19 Sludge pump 20 Alkaline treatment tank 21 Residence tank 22, 27, 31, 68 Piping 23 Alkali treatment liquid supply pump 24 Alkaline agent 25 Alkaline agent storage tank 26 Alkaline agent supply pump 28 Sodium hypochlorite 29 Sodium hypochlorite storage tank 30 Hypochlorous acid Soda supply pump 32, 34 Stirrer 33, 35 pH meter 36 Weir 37 Sewage return pipe 38 Sewage return pump 61 Nitrate solution 62 Nitrate solution storage tank 66 Alkali processing liquid storage tank 67 Alkali processing liquid supply pump 105 Alkali cleaning tower 117 Cleaning liquid storage tank 118 Alkaline Cleaning liquid 119 Cleaning liquid supply pump 09 crystals phosphorus removal tank 212 Calcium 213 Calcium reservoir 214 Calcium supply pump

Claims (12)

In wastewater treatment method comprising nitrification step and the denitrification step nitrifying denitrifying biologically treated wastewater containing at least septic tank sludge of night soil Oyo BiKiyoshi of tank sludge,
An alkali treatment step of adding an alkaline agent to the sewage and diluting a part of the sewage before being sent to nitrification denitrification, and eluting the carbon source for denitrification from the branched sewage , and the alkali A retention step of retaining the wastewater to which the agent is added;
And supplying the sewage after the staying step to the denitrification step,
In the alkali treatment step , the sewage residence time is 0.5 hours or more and 2 hours or less, and the pH of the sewage water retained in the alkali treatment step is 11.6 or more and 12.5 or less ,
In the retention step , the wastewater retention time is 12 hours or more and 48 hours or less. Human waste Oyo nitrification step and the denitrification step of nitrification denitrification treatment biologically sewage containing at least one of BiKiyoshi of tank sludge, and were obtained by solid-liquid separation of sewage after the nitrification denitrification treatment In the sewage treatment method comprising the step of returning sludge before the nitrification step and the denitrification step,
By branching a portion of the sludge, to elute the de窒用carbon source from the branched allowed sludge, comprising the alkali agent is added to the alkali treatment step and the sludge adding an alkali agent to the sludge A retention step for retaining sewage;
The wastewater after the residence step and a step for supplying to said denitrification step,
In the alkali treatment step , the sewage residence time is 0.5 hours or more and 2 hours or less, and the pH of the sewage water retained in the alkali treatment step is 11.6 or more and 12.5 or less ,
In the retention step , the wastewater retention time is 12 hours or more and 48 hours or less. Residence distillate when the pH of the wastewater is less than 9 in step wastewater treatment method according to claim 1 or 2, wherein the addition of sodium hypochlorite in the wastewater. It has a deodorization process that deodorizes the atmosphere of sewage or sludge by alkali cleaning,
Alkaline wastewater generated in the deodorizing process, wastewater treatment method according to any one of claims 1 to 3, characterized by using the A alkali agent and co in A alkali treatment step. In later stage than distillation step stagnation, and separating the solids in the wastewater,
Sewage according to any one of claims 1 to 4 The solid is characterized in that chromatic and crystallization phosphorus removal step of recovering phosphorus in the wastewater by adding calcium agent sewage after separation Processing method. In A alkali treatment step, and continuously stirring the wastewater or sludge alkaline agent is added,
In residence distillation process, wastewater treatment method according to any one of claims 1 to 5, characterized in that stirring intermittently wastewater. In sewage treatment apparatus comprising a nitrification unit and denitrification means nitrifying denitrifying biologically treated wastewater containing at least septic tank sludge of night soil Oyo BiKiyoshi of tank sludge,
Alkaline treatment means for adding an alkali agent to the sludge and diluting a part of the sewage before being sent to the nitrification denitrification treatment and eluting the carbon source for denitrification from the branched sludge and the alkali A retention tank for retaining sewage to which an agent is added;
A means for supplying the sewage after the retention to the denitrification means,
The alkali treatment means includes an alkali treatment tank for retention of the sewerage, this alkali treatment tank has an effective volume of the residence time of sewage is less than 2 hours or more 0.5 hours at which alkali treatment tank, the residence The alkaline agent is added in such an amount that the pH of the wastewater is 11.6 or more and 12.5 or less,
The sewage treatment apparatus characterized in that the stagnation tank has an effective volume in which the sewage residence time is 12 hours or more and 48 hours or less. Night soil Oyo nitrification unit and denitrification means for nitrification denitrification treatment biologically sewage containing at least one of BiKiyoshi of tank sludge, means for solid-liquid separation of sewage after the nitrification denitrification treatment, the solid In a sewage treatment apparatus comprising a sludge return means for returning sludge obtained by liquid separation before the nitrification means and the denitrification means,
By branching a part of the sludge to be returned, to elute the de窒用carbon source from the branched allowed sludge, alkaline agent is added to the alkali treatment means and the sludge adding an alkali agent to the sludge A retention tank for retaining sewage,
A means for supplying the sewage after the retention to the denitrification means,
The alkali treatment means includes an alkali treatment tank for retention of the sewerage, this alkali treatment tank has an effective volume of the residence time of sewage is less than 2 hours or more 0.5 hours at which alkali treatment tank, the residence The alkaline agent is added in such an amount that the pH of the wastewater is 11.6 or more and 12.5 or less,
The sewage treatment apparatus is characterized in that the stagnation tank has an effective volume in which the sewage stays for 12 to 48 hours. It means for detecting the pH of the wastewater to be retained in the residence Tomeso,
The sewage treatment apparatus according to claim 7 or 8, further comprising means for adding sodium hypochlorite to the sewage when the pH detected by the means is less than 9. Deodorizing means for deodorizing the atmosphere of sewage or sludge by alkali cleaning,
The resulting alkaline wastewater in the deodorizing means, sewage treatment apparatus as claimed in the preceding claims 7, characterized in that the means for supplying the A alkali processing means is provided 9. In residence stage after Tomeso, means for separating the solids in the wastewater,
Any one according to claim of claims 7 to 10 this solids, characterized in that it further comprises a crystallization phosphorus removal means for recovering phosphorus in the wastewater by adding calcium agent sewage after separation Sewage treatment equipment. A alkali treatment means includes a stirring means for continuously stirring the wastewater or sludge alkaline agent is added,
Stagnation Tomeso is sewage treatment apparatus of any one according to claim of claims 7 to 11, characterized in that a stirring means for stirring the intermittently wastewater is provided.

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