JP4799378B2 - Sewage treatment method - Google Patents

Description

  The present invention relates to a sewage treatment method using a sewage treatment plant for sewage, such as domestic household wastewater and business effluents of some business establishments, and in particular, can improve the septic odor generated at the sewage treatment plant, etc. The present invention relates to a sewage treatment method that can reduce the treatment load of a sewage treatment plant.

  Wastewater (so-called sewage) such as general household wastewater and business wastewater containing organic substances from some business establishments is collected in sewage treatment plants via pipes and purified by aerobic oxidation treatment by microorganisms. Usually released. In addition, household wastewater from villages and fishing villages in which ordinary households are dispersed is often collected through similar pipes to similar treatment facilities and purified by aerobic oxidation treatment with microorganisms.

  In this sewage treatment plant, etc., an increase in biochemical oxygen demand (BOD) and odor due to decay of sewage contents in an anaerobic basin, initial sedimentation tank (primary sedimentation tank) and gravity concentration tank In addition, there are problems such as deterioration of the gravity sedimentation efficiency due to the decay of sediment in the initial sedimentation tank and the like, and deterioration of the water quality of the initial sedimentation tank due to the return water.

  However, in the current management of sewage treatment plants, these problems are considered to be unavoidable due to the nature of sewage. The fact is that there is almost no point of view to make such improvements. Therefore, as countermeasures against odors, odor duct facilities are strengthened, sealing tents are strengthened, and deodorants are used.

  Comparing the current BOD value of the inflowing sewage with the BOD value at the inlet or outlet of the first settling tank, the BOD values at the first sinking tank inlet and outlet are often high, and this increase in BOD value is the first from the sewage inlet. It is clear that this is a result of rot in the process between the settling tank outlets or solubilization of the suspended suspended component (SS). Further, since the BOD increases due to the spoiled return water, it is necessary to increase the amount of aeration corresponding to the increase in the BOD, resulting in an increase in the load on the aeration tank. In addition, as a result of the progress of the decay of the first settling sludge, the use of a flocculant and the use of a deodorant are necessary. By the way, the sand basin and the first settling tank are facilities for sinking the object, so it is difficult to take aerobic anti-corruption measures.

  By the way, conventionally, various methods for promoting purification in the activated sludge method have been proposed. For example, a method for treating organic wastewater that predominates Bacillus bacteria in a biological treatment tank by selectively killing a group of microorganisms other than Bacillus bacteria in sludge has been disclosed (see Patent Document 1). In addition, sludge containing endospore-forming bacteria such as Bacillus bacteria is mixed with organic wastewater in advance, the spores of endospore-forming bacteria are germinated and converted to vegetative cells, and the mixed solution containing vegetative cells is aerated Is disclosed (see Patent Document 2). In addition, a microbial reaction method in which a plurality of microbial reaction tanks are provided and a microbial nutrient source-containing liquid moves alternately between the plurality of reaction tanks is disclosed (see Patent Document 3).

However, these conventional methods are only effective methods in the steps after the aeration tank, which is an aerobic atmosphere, and an anaerobic atmosphere settling basin, initial settling tank, or gravity concentrator provided in the preceding stage. A viewpoint to solve the above-described problems occurring in a tank or the like is not disclosed in the prior literature.
JP 2004-275960 A JP 2001-162297 A JP 2003-71479 A

  The present invention prevents the decay of organic matter containing wastewater in the treatment process located in the preceding stage of the aeration tank from the sand basin of the sewage treatment plant to the gravity concentration tank, suppresses the generation of odors such as hydrogen sulfide, and surplus sludge It is an object to provide a sewage treatment method capable of reducing the amount of wastewater and reducing the treatment burden.

  As a result of intensive studies to solve the above problems, the present inventors have reached the following method. That is, the present invention is a sewage treatment method for biologically treating wastewater by sending it to a sewage treatment plant via a pipe culvert and a relay pump station, and has a function of decomposing organic matter in the effluent in the pipe culm. A microorganism preparation containing microorganisms is introduced from the relay pump station, and at least a part of the organic matter is decomposed by the microorganisms generated from the microorganism preparation in the pipe tube from the relay pump station to the sewage treatment plant. This is a method for treating sewage.

  Here, it is preferable that the length of the pipe rod from the relay pump station to the sewage treatment plant is 5 km or more. In addition, it is preferable that the microorganism is a Gram-positive bacterium having a resolution of the organic matter and forming a spore. In addition, when the microbial preparation is introduced into the tube, it is preferably introduced after the microbial preparation is dispersed in water in advance, or dispersed in water in advance and aerated to form vegetative cells. Further, the microorganism is a Gram-negative bacterium that has the ability to decompose the organic matter and does not form spores, and the microbial preparation is a solid microbial agent that is solidified by using rice bran or wheat bran. preferable. The microbial preparation is preferably a solid microbial preparation containing gram positive bacteria and gram negative bacteria. Moreover, it is preferable that the microorganism is a genus Bacillus. Moreover, it is preferable that the microorganism is Bacillus toyoi. In addition, in introducing the microorganism preparation, the microorganism preparation is introduced so that the number of microorganisms in 1 ml of the wastewater is 1/1000 or more of the number of bacteria per ml originally present in the wastewater. preferable.

  Microorganisms that are introduced into the pipe tank from the relay pump station can surprisingly demonstrate the decomposition of organic matter in the pipe tank, and prevent decay in the sand basin, first settling tank, and gravity concentration tank in the sewage treatment plant. Is done. As a result, odors such as hydrogen sulfide are suppressed. In addition, the return water to the settling basin is prevented from being spoiled. As a result, the water quality of the first settling tank located downstream of the settling pond is improved, and biological wastewater with a low BOD flows into the aeration tank. The processing burden is reduced. Furthermore, in the aeration tank, microorganisms that have been thrown into the pipe can be propagated, so that stable water treatment is possible and excess sludge is reduced.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram illustrating a case where the method of the present invention is carried out using the entire general sewage treatment flow currently used. Wastewater including domestic wastewater 1 of houses and condominiums and business wastewater 2 from establishments such as food manufacturing factories is collected via pipes 3 and collected at relay pump stations 5 and 6. Then, it flows into the sand basin 10 of the sewage treatment plant 9 via the pipe rods 7 and 8 having a relatively large diameter from the relay pump stations 5 and 6, and is treated for sewage treatment.

  The pipe pipe here is a part of the sewer, which is a passage for removing sewage from houses, factories, etc., and sending it to a sewage treatment plant etc. via a relay pump station. It is normal. The tube rod has a circular cross section (in particular, called a sewer pipe), a semicircular shape, an oval shape, a horseshoe shape, a rectangular shape, etc., and has a tube diameter of about 15 cm or more. In addition, a combined pipe tube that joins rainwater may be included, but in order to keep the environment of the bacteria constant, it is preferable to use a divided pipe tube that does not join rainwater.

  In particular, pipes connected from the relay pump station to the sewage treatment plant are usually designed to have a pipe diameter that is about 7 to 5 times the amount of sewage, and the sewage is about 20% of the pipe volume. The remaining 80% becomes air. In such a pipe casing, since there is a sufficient amount of air in the pipe casing, the inside of the pipe casing becomes an aerobic atmosphere.

  In addition, a relay pump station is a dedicated site for sending sewage from a certain sewage drainage area to a drainage area where a sewage treatment plant is located, or for relaying sewage due to the depth and slope of pipes. Says the pumping station provided inside. Relay pump stations are often installed in urban areas.

  In this relay pump station, a microbial preparation containing microorganisms having a function of decomposing organic matter in the waste water is put into the tube. As a result, the microorganisms generated from the microbial preparation are propagated using the aerobic atmosphere in the pipe while the drainage flows down the pipe, and the organic matter that causes rot in the sewage treatment plant is decomposed as much as possible. Found that is possible.

  Microbial preparations can be introduced at the site of the generation of biological wastewater in houses, etc., or at the manhole pumping station installed in the basement of the road, but contain relatively expensive Bacillus spp. In order to efficiently inject microbial preparations, use a relay pump station where the amount and frequency of injection are easy to manage, and the tube diameter of the tube is relatively large, making it a suitable environment for microbial growth. It is good. If there are multiple relay pump stations between the site where the wastewater is generated and the sewage treatment plant, all of the relay pump stations may be used. It is preferable to select at least one place and input it because it is efficient and low cost.

  By the way, even if a microorganism such as a Bacillus genus described later that excels in organic matter decomposition function is introduced into the tube that originally contains many bacteria, the activity of the bacteria decreases due to a decrease in the concentration of the bacteria. It was expected that it would be difficult to demonstrate the original decomposition performance. In addition, since microorganisms do not grow or dominate unless they are filled with a suitable environment such as water temperature and dissolved oxygen, and preferred foods, even if they are put into tube tubs under conditions where Bacillus bacteria do not dominate It was common sense that it was difficult to proliferate and dominate, and it was thought that the intended effect could not be demonstrated. However, unexpectedly, the growth of microorganisms was observed in the pipe tubs due to the introduction of microorganisms, resulting in the effect of reducing the odor at the sewage treatment plant.

  The reason why such a result was obtained is unknown, but the inside of the tube can be considered as a kind of aerobic bioreactor in which the dissolving action of oxygen and the stirring action by the flow occur. One reason may be that the relatively long flow-down distance is the place to earn biological reaction time (HRT). As a result, in the process in which the input microorganisms flow while growing while eating the organic matter in the tube, the easily decomposable organic matter that causes rot is treated, and the sand settling tank and the first settling tank in the downstream sewage treatment plant And the effect which prevents the decay of the easily decomposable organic substance in the gravity settling tank was acquired. Also, in these tanks, the previously introduced microorganisms can grow and become an effective organic matter-decomposing microbial species in the subsequent activated sludge tank. As a result, the effect of reducing excess sludge can be obtained.

  The flow length of the pipe dredging from the relay pump station to the sewage treatment plant is preferably 5 km or more. By providing such a distance, it takes about 5 to 7 hours at least for the drainage to flow down the pipe, and during this time, more time can be taken for the organic matter in the drainage to decompose. . The length of flow from the relay pump station to the sewage treatment plant is usually about 5 to 40 km depending on the location of the sewage treatment plant, and the drainage takes several hours to half a day to reach the sewage treatment plant. This time corresponds to the residence time (HRT) in the aeration tank of the sewage treatment plant or substantially equal to or longer than the residence time in the pipe tank, so that it is sufficient to use the pipe tank as a biological reaction tank. More preferably, it is 7 km or more, and further preferably 10 km or more.

  As the microorganism preparation to be introduced into the tube, the microorganism obtained from the preparation may be any microorganism that can effectively decompose the organic matter contained in the wastewater in the tube, but it can grow in the tube and be the dominant species. More preferably, it is a microorganism that can be.

  The shape of the microbial preparation is preferably a spore that can be stored stably for a long period of time. For example, Gram-positive bacteria that produce spores are preferable because they are easy to handle. The fungus itself is stable in the spore and can grow stably for more than one year in a solid mixture. On the other hand, Gram-negative bacteria, which are vegetative cells that do not become spores, should be solidified by mixing with wheat bran or rice bran. Gram-negative vegetative cells can be dried with a mixture of wheat bran, rice bran, etc. to give a solid microbial preparation, which can be used effectively even though it has a short shelf life as a preparation.

  As the spore bacterium, Bacillus is preferable because it has a high organic matter resolving power and can suppress the activity of anaerobic bacteria to reduce odor. Spore bacteria obtain nutrients from the surrounding sewage components while flowing down the long sewage pipes, become nutrient cells, adhere to the pipe sap and the inner wall of the tub, decompose organic matter in the sewage, and themselves Divides and grows.

  Among them, Bacillus toyoi is also used as an animal pharmaceutical as a microorganism that produces an intestinal regulating effect in the intestines of livestock, has high organic matter resolution, is highly active even in anaerobic conditions, and proliferates. Although the oxygen concentration for activity is not necessarily sufficient, it is the most suitable microorganism that maintains activity even under conditions relatively similar to the situation in the animal intestine and has high activity as an activated sludge fungus.

By the way, the general number of microorganisms originally present in the wastewater is about 10 ⁵ to 10 ⁶ cells / ml. It is preferable to set the number to be 10 ³ or more per ml. That is, it is preferable to set it to about 1/1000 or more of the number of microorganisms originally present in general waste water. When the amount ratio of the microbial preparation is within this range, the introduced microorganism can sufficiently act in the tube and continue to grow. The effect is more certain as the input amount of the microbial preparation is larger, but there is an upper limit to the appropriate input amount due to the balance between the cost of the preparation and the effect of reducing sludge and electricity costs. As a result of the growth of the input microorganisms under the flow of the pipe, the input microorganisms have water treatment performance even in the aeration tank where about 10 ⁸ to 10 ⁹ microorganisms per ml exist after passing through the sand basin and the initial sedimentation tank. Demonstrate activities that can be demonstrated. More preferably, it is 1/500 or more.

  As a method for introducing microorganisms or the like, an injection method suitable for the management state of the relay pump station may be appropriately determined depending on the input location and the management status. The specified amount of powder may be added as it is, or the powder may be dispersed in water before pumping, but it is convenient and preferable to disperse in water before pumping. In the case of using Gram-positive bacteria that form spores, it is preferable to disperse a microbial preparation containing Gram-positive bacteria in water in advance, and aerate and add them as vegetative cells because the organic matter decomposition effect is high.

  In addition, since the drainage always flows down, it is preferable to continuously put the microbe preparation into the tube. However, it is possible to insert it intermittently at a pace of once every day or once every three days. But it ’s okay. The introduction interval may be increased if the microorganisms that have been introduced into the tube for a certain period are sufficiently acclimatized in the tube and grow on the tube wall. For example, on holidays where there is no manager of the relay pump station, a method may be employed in which an amount larger than the normal amount is input before the holidays.

  The wastewater in which at least a part of the organic matter is decomposed in the pipe dredes flows into the sand basin 10 of the sewage treatment plant 9 and stays in the sand basin for a certain time. During this time, large dust or sand contained in the waste water is settled and removed. The drainage from which the sand and the like have been removed moves from the settling basin 10 to the initial settling tank 13 via the pipe 12. In the initial settling tank 13, the drainage is made to flow more slowly to settle and remove dust, mud, etc. that could not be removed in the sand basin 10.

  The waste water from which mud and the like have been removed in the initial settling tank 13 moves to the aeration tank 20 via the pipe 18. Further, the sludge 14 that has settled in the initial settling tank 13 is drawn out of the initial settling tank 13 and transferred to the gravity concentration tank 16 through the pipe 15. In the gravity concentration tank 16, the extracted sludge is stored and further sludge components are precipitated and concentrated. The initially settled sludge 28 concentrated in the gravity concentration tank 16 is sent to the sludge storage tank 30. On the other hand, the remaining waste water from which the sludge has been removed in the gravity concentration tank 16 is returned to the sand basin 10 as return water 17. The amount of the return water 17 is about 5 to 10% of the waste water flowing into the sewage treatment plant.

  A series of processing steps composed of the sand basin 10, the initial sedimentation tank 13, and the gravity concentration tank 16 are located in the front stage of the aeration tank 20, and exhibit a function of removing sludge by sedimentation. Such processing cannot be performed. Therefore, it has become an anaerobic atmosphere in which aerobic treatment cannot be performed, and conventionally, organic matter contained in wastewater has been easily rotted. In addition, the wastewater containing the rotted organic matter returns to the settling basin 10 as the return water 17 and circulates through the initial settling tank 13 to the gravity concentration tank 16 to the settling basin 10, so that the rot easily proceeds. In addition, although the amount of the return water 33 from the dehydrator 32 described later is small, the BOD value is high, and the water quality of the sand basin 10 is deteriorated.

  However, when the microorganism preparation is introduced into the pipe tub from the relay pump station, the amount of organic matter in the wastewater flowing into the sand basin 10 is reduced, and the septic in the sand basin 10 is less likely to occur. For this reason, it is difficult for the initial settling tank 13 and the gravity concentration tank 16 to be spoiled, and the return water 17 is also less likely to increase the BOD value. That is, it becomes difficult to produce rot in the entire circulation cycle composed of the sand basin 10 to the initial sedimentation tank 13 to the gravity concentration tank 16, and the generation of odor is also suppressed. Furthermore, since the BOD value of the return water 33 is also improved, a considerable improvement occurs throughout the circulation cycle.

  The steps from the sand basin 10 through the initial settling tank 13 to the gravity concentrating tank 16 where the decay is most advanced are facilities for settling SS components, and all oxygen in the water is consumed and redox. The potential (ORP) is in a negative state. Therefore, it is not common sense to suppress the decay of organic matter in this conventional state. By the way, it is conceivable that aerobic microorganism preparation for preventing corruption is introduced into the sand basin 10 to suppress corruption after the first sedimentation tank 13, but even if aerobic bacteria are introduced in a situation where ORP is negative, The fact is that there is no prevention effect.

  The wastewater moved from the initial settling tank 13 to the aeration tank 20 is biologically treated with activated sludge in the aerobic atmosphere of the aeration tank 20, and the sludge dissolved in the wastewater is absorbed or adsorbed as nutrients to decompose or settle. Change to easy-to-use sludge. At this time, since the organic matter content in the waste water flowing into the aeration tank 20 is reduced, the amount of air in the aeration tank 20 is reduced and the amount of activated sludge necessary for the treatment is also reduced.

  The wastewater treated in the aeration tank 20 moves to the final settling tank 22 via the pipe 21, and the activated sludge 23 is settled. The supernatant liquid from which the activated sludge has been settled and removed is sterilized via the pipe 40 and then discharged into public water areas such as rivers and lakes. On the other hand, a part of the activated sludge 23 settled and removed in the final settling tank 22 is returned to the aeration tank 20 as a return sludge 25 via a pipe 24, and the rest is sent to a surplus sludge machine concentration tank 26 as surplus sludge. . As a result of reducing the burden on the aeration tank 20 by introducing the microorganism preparation into the tube beforehand, the amount of excess sludge moving to the excess sludge machine concentration tank 26 also decreases, and the sludge treatment load after the aeration tank 20 is reduced. Can be reduced overall.

  In the excess sludge machine concentration tank 26, centrifugal force is applied by the machine to increase the sludge concentration, and the sludge is further sent to the sludge storage tank 30. In the sludge storage tank 30, it stores together with the first sedimentation sludge 28 sent from the gravity concentration tank 16. By introducing the microbial preparation into the tube beforehand, both the initial settling sludge 28 and the excess sludge 27 are reduced. When a certain amount of the sludge is stored, it is sent from the sludge storage tank 30 to the dehydrator 32 via the pipe 31, and if necessary, a flocculant is added and dehydrated by centrifugal force to become a dehydrated cake 35. The dehydrated cake is taken out of the hall, and finally disposed of by incineration.

  On the other hand, the squeezed water separated from the sludge by the dehydrator 32 is returned to the settling basin 10 as return water 33 although the amount is small. Since the microorganism preparation has been put in the pipe in advance, the return water 33 is not easily spoiled, and the return water 33 with relatively good water quality is returned to the sand basin 10. Thereby, the decay in the sand basin 10 is further prevented, and the generation of odor is less likely to occur.

  In addition, what is necessary is just to perform the measurement of the grade of the odor which generate | occur | produces by decay at the measurement port of the odor duct of the deodorizing equipment conventionally provided in the sewage treatment plant. In addition, water quality such as drainage may be measured at any time by normal sampling. For example, it may be measured and managed at the drainage inlet of the settling basin 10, the return water 34, the pipe 18 at the initial settling tank outlet, or the like. Furthermore, the degree of the effect by introducing the microbial preparation can be confirmed by comparing each measured value with the same month last year.

  As explained above, the introduced microbial preparation can function to proliferate in the pipes and decompose the organic matter in the wastewater against the common sense that has been considered in the past, and as a result, spoilage in the sewage treatment plant is prevented. As a result, the odor generation is reduced and the volume of sludge to be treated in the subsequent process is reduced. Such a biological treatment process is not limited to the case where an aerobic treatment for decomposing BOD as described above is used, but also an anaerobic method such as an anaerobic-aerobic method or anaerobic-anoxic-aerobic for denitrification. It is also effective in the process of processing methods that combine sex processing. Moreover, the process process after an aeration tank, such as a sludge process process, can also be changed. Hereinafter, the present invention will be described more specifically with reference to examples.

The test was conducted using the A sewage treatment plant having the same treatment process as shown in FIG. The wastewater treatment capacity of the A sewage treatment plant is 13,500 m ³ / day, the current inflow is 12,000 m ³ / day, and the activated sludge treatment method is a mechanical concentrating method. The dehydrated cake hung on is taken off-site. The distance from the relay pump station where the microbial preparation is to be introduced to the sewage treatment plant is about 15 km, which is almost equal to the flow length of the pipe.

As a microbial preparation, a powder in which Bacillus toyoi, glucose, magnesium carbonate, and amino acid are uniformly dispersed is prepared, and this preparation is dispersed in water immediately before charging, so that the concentration of Bacillus toyoi is 6 × 10. It adjusted so that it might become ⁹ piece / ml, and it was set as the main liquid for injection | throwing-in.

The charging method was as follows. First, 60 L of this liquid is introduced on the first day from the introduction hole provided in the relay pump station. On the second day, 12 L of this solution is introduced in the same manner. Thereafter, 12 L of this liquid is added every day. In introduction of the liquid 12L relative drainage 12,000 m ^3, since the ratio in biological waste water of the present solution is about 1 ppm, steady cell concentration in the waste water of Bacillus Toyoi bacteria, calculated on 6 × 10 ³ pieces / ml.

  The analysis items for judging the effect of water quality are SS concentration and BOD value as the drainage properties at the entrance of the sedimentation basin, and the transparency of the initial sedimentation tank outlet water that is homogenized by circulating the return water from the gravity concentration tank, As the pH, SS concentration and BOD value, the monthly average of these measured values after the introduction of the microorganism preparation was determined. And the effect was judged by contrasting these with the average value for every month of each measured value of the previous year and the year before last. The water quality after the sewage treatment was measured by measuring the transparency, SS concentration, and BOD value of the outlet water of the final settling tank, and compared with that before the introduction of the microorganism preparation.

  Regarding the decay of drainage before the entrance of the aeration tank, a gas sample was taken from the sampling hole of the deodorization equipment provided in front of the entrance of the aeration tank, and the concentration of hydrogen sulfide and methyl mercaptan was measured. . In addition, the height of the sludge stored in the gravity concentration tank was measured at the interface between the sludge and the supernatant and compared.

  Evaluation in the aeration tank is to measure the SS component, MLSS concentration, VSS rate, aeration amount and aeration ratio, return sludge concentration, return sludge dry sludge (DS) amount and return sludge amount in the aeration tank, respectively. The change with time was observed. Regarding the evaluation of surplus sludge, the amount of surplus sludge extracted from the final settling tank after the introduction of the microorganism preparation, the concentration of surplus sludge and the DS amount were measured and compared with the measured values before the introduction of the microorganism preparation.

  Table 1 shows the amount of inflow of actual wastewater from the A sewage treatment plant up to 2005, when the microbial preparation was evaluated from 2003. The injection of the microbial preparation started on March 20, 2005 and was carried out every day for 6 months until September 20. March and April were acclimatized periods in the sand basin, the initial sedimentation tank, the primary sedimentation gravity concentration tank and the aeration tank in the pipe dredger and sewage treatment plant.

  The SS concentration and BOD value of the inflow water to the sewage treatment plant in March and April from 2002 to 2017, and the average value of SS concentration and BOD value from April to August of each year, respectively. Measured and shown in Table 2. From Table 2, there is almost no change in the SS concentration before and after the introduction of the microbial preparation, but the average BOD value from April to August in 2005 is 115 ppm, clearly compared with the previous three years It can be confirmed that it has decreased. As a reminder, Table 3 shows the detailed evaluation results of the influent water condition in March before the start of introduction in 2005 and from April to September after the start. It can be seen that the BOD value has decreased on average in any month after the introduction. From this, it can be seen that the purification is carried out by decomposing a part of the organic matter contained in the wastewater in the pipe by introducing the microbial preparation.

  The wastewater that has flowed into the sewage treatment plant from the pipe first flows into the sand basin 10. The settling basin 10 is supplied with the total return water 34, which is the return water 17 from the gravity concentration tank 16 and the return water 33, which is the squeezed water from the dehydrator 32, which is the circulating water in the sewage treatment plant. To do. By the way, the total amount of the return water 34 is about 5 to 10% of the amount of waste water flowing into the sewage treatment plant.

  The drainage discharged from the settling basin 10 is transferred to the initial settling tank 13 through the pipe 12, where the SS component settles, and the supernatant water flows from the initial settling tank 13 into the aeration tank 20 through the pipe 18, It receives activated sludge treatment here. Table 4 shows the measurement results for the SS concentration and BOD value of the initial sedimentation tank in March and April 2005 before acclimatization, and the measurement results and average values from May to September after acclimatization. It was shown to. As is clear from Table 4, there is no clear difference in the SS value before and after the acclimatization, but the average value of the BOD value is 88 ppm after the acclimatization, which is clearly lower than before, The effect in the first sedimentation tank by the introduction of the microbial preparation can be read.

  Next, Table 5 shows the results of measuring the odor gas concentration in the exhaust duct of the deodorization equipment in the gravity concentration tank 16 in which the sludge moves from the initial settling tank 13. The gas to be measured was hydrogen sulfide and methyl mercaptan. During the acclimatization period from March to April, the hydrogen sulfide concentration is 10 to 15 ppm, and methyl mercaptan is below the lower limit of quantification, but it is confirmed by the gas detector tube method that it exists qualitatively. did it. On the other hand, from May to September after the acclimatization, hydrogen sulfide decreased to about 0 to 2 ppm, and methyl mercaptan could not be detected qualitatively. It can be seen that the rot progression in the gravity concentration tank 16 is suppressed by the introduction of the microorganism preparation into the tube.

  Furthermore, the height of the sludge interface of the gravity concentration tank 16 was measured, and the amount of sludge was evaluated. The results are shown in Table 6. At the beginning of the introduction of the microbial preparation, the sludge interface was as high as about 1 m, and as shown in the gas measurement results in Table 5, there was 10 ppm or more of hydrogen sulfide, and the septic fermentation was in progress. The sludge interface dropped from May, when the acclimatization of the input microorganisms progressed, and stabilized at less than 40 cm. At the same time, the generation of hydrogen sulfide was suppressed. It can be seen that the amount of sludge generated in the settling basin 10, the initial settling tank 13, and the gravity concentration tank 16 is reduced by the introduction of the microorganism preparation.

  Next, since the waste water which flowed into the aeration tank 15 from the first settling tank 13 is subjected to the activated sludge treatment here, the treatment conditions in the aeration tank 15, the improvement effect of the activated sludge tank, and the biologically treated water quality are shown in Table 7. Indicated. In order to obtain a predetermined predetermined water quality, operation is performed with the aeration air amount changed, but the aeration magnification of each month, which means the volume ratio of the aeration air amount to the inflow amount of biological wastewater, is March, 4 Compared to the moon, it began to drop in May and dropped to 4.6 times in September.

  The MLSS of the aeration tank 15 was about 1700 to 1800 in March and April, but gradually decreased from 1500 to 1400 when the acclimatization was sufficiently completed. This is consistent with the fact that the aeration rate decreases with the progress of habituation. Furthermore, the VSS rate of the activated sludge tank is also reduced by about 2%, and it can be seen that the amount of organic matter in the sludge (the amount of activated sludge bacteria) is also reduced. From the above, it can be seen that the processing load in the aeration tank 15 is clearly reduced. This means that the transparency, SS concentration, and BOD value of the effluent water obtained from the outlet of the final sedimentation tank 22 following the aeration tank 15 described in Table 7 are compared with March before acclimatization. It can also be seen from the fact that it has improved considerably in May to September after the acclimatization. Thus, it can be seen that also in the aeration tank 20, due to the effect of the input microorganism preparation, a predetermined water quality can be maintained with a low MLSS value, and the aeration amount is reduced to reduce the aeration magnification. As a result, the operating electricity cost of the aeration tank 15 was reduced by about 20%.

  Next, the volume reduction of sludge by inputting a microbial preparation will be described. Table 8 shows the amount of sludge processed each month in the gravity concentration tank 16 and the mechanical concentration tank 26. Although there is no particular change in the amount of sludge in the gravity concentration tank 16 before and after acclimatization, the situation is different with respect to the excess sludge processed in the mechanical concentration tank 26. The concentration of excess sludge is almost constant from 4.1 to 4.5%, but the amount of sludge in each month is gradually decreasing. Therefore, the monthly amount of sludge converted into dry sludge was about 36 tons / month in March before acclimatization, but is stable at around 31 tons / month, a decrease of about 15% after acclimatization. This result is that Bacillus toyoi introduced into the tube begins to grow in the tube, reaches the inside of the aeration tank 20 through the initial settling tank, etc., and exhibits an effective biological treatment function in the aeration tank 20 It is thought that.

  The table also shows the results of comparing the effect of reducing excess sludge between the four months from June to September 2003 and the same period in 2005 when the microbe preparation was not introduced. 9 shows. The amount of inflow to biological wastewater sewage treatment plants has been increasing year by year, and the amount of surplus sludge should increase in proportion to the amount of inflow. However, the actual amount of surplus sludge in 2005 is the previous inflow. It was lower than the amount of excess sludge estimated from the amount of water and the amount of excess sludge, and was even lower than the previous year.

It is the conceptual diagram which showed the whole processing flow at the time of implementing the method of this invention.

Explanation of symbols

1 Domestic wastewater 2 Business drainage 3 Pipe dredging from drainage point to relay pumping station 5, 6 Relay pumping station 7, 8 Pipe dredging from relay pumping station to sewage treatment plant 9 Sewage treatment plant 10 Sedimentation basin 12 First from sedimentation basin Liquid feed pipe 13 to the settling tank Initial settling tank 14 Initial settling sludge 15 Sludge liquid feed pipe 16 from the initial settling tank to the gravity concentration tank Gravity concentration tank 17 Return water 18 Liquid supply pipe 20 from the first settling tank to the aeration tank 20 Aeration Tank 21 Liquid feed pipe from aeration tank to final sedimentation tank 22 Final sedimentation tank 23 Sediment sludge 24 Sludge liquid feed pipe 25 Return sludge 26 Surplus sludge machine thickener 27 Surplus concentrated sludge 28 Primary sedimentation sludge 30 Concentrated sludge storage tank 31 Sludge Liquid feed pipe 32 Dehydrator 33 Return water 34 Return water 35 Dehydrated cake 36 Coagulant 40 Sewage treated water 41 Disinfection discharge 50, 51 Microbial preparation input

Claims (4)

  A sewage treatment method for sending wastewater to a sewage treatment plant via a pipe culvert and a relay pump station, and biologically treating the sewage treatment plant, and having the function of decomposing organic matter in the effluent in the pipe culm A microorganism preparation containing bacteria is introduced from the relay pump station, and at least a part of the organic matter is decomposed by microorganisms generated from the microorganism preparation in the pipe tube from the relay pump station to the sewage treatment plant. A sewage treatment method.   2. The sewage treatment method according to claim 1, wherein a length of the pipe culvert from the relay pump station to the sewage treatment plant is 5 km or more.   The sewage treatment method according to claim 1 or 2, wherein the microorganism is a Gram-positive bacterium having a resolution of the organic matter and forming a spore.   When the microbial preparation is introduced into the tube, the microbial preparation is dispersed in water in advance, or dispersed in water in advance and aerated to form vegetative cells. 4. The sewage treatment method according to any one of 3.

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