JP2006231106A - Offensive odor prevention method and offensive odor prevention system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize the prevention of offensive odor generation from a waste water storage tank at a low cost; to facilitate the design and construction of an odor prevention system. <P>SOLUTION: When ozone concentration in a gas phase in a storage tank 1 storing waste water where BOD load and organic SS load exist and their total is less than 50 kg/m<SP>3</SP>is D (ppb), discharge air quantity is E (m<SP>3</SP>/h), the half-life of ozone in air is τ (h), the upper target value of discharged ozone concentration control is D' (ppb), and the volume inside of an air discharge system of the storage tank 1 is V (m<SP>3</SP>) the volume inside of the air discharge system, V, is set so as to satisfy the following equation: V>τ×(log(D/D')/log2)×E. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for preventing generation of malodor from a tank storing wastewater in which a BOD (Biochemical Oxygen Demand) load and an organic SS (Suspended solid) load exist. It is about the system.

  In the kitchen wastewater and wastewater temporary storage tanks (including flow control tanks), which are wastewater with organic loads as described above, inflow of inflow water has been interrupted for a long time because air is not generally supplied. In such a case, the stored wastewater becomes anaerobic and bad odor is generated, and the odor is released to the outside through the ventilation pipe. It has become.

  In order to cope with this, recently, it has been proposed to purify a large-sized waste by supplying ozone-containing air into the wastewater after the filtration (Patent Document 1). As for the odor generated in the septic tank, it has been proposed that ozone is supplied directly to the upper space of the septic tank or waste water, and the ozone concentration in the air layer is maintained below 0.1 ppm to deodorize it (patent) Reference 2).

JP-A-9-314166 JP 2000-233192 A

  However, the conventional technique described in Patent Document 1 provides sufficient oxygen to the wastewater after filtration to activate the aerobic bacteria, and the household wastewater is purified by the aerobic bacteria. For this reason, it is necessary to perform filtration in the previous stage in order to prepare a breeding environment for aerobic bacteria, and in some cases, there is a possibility that odors may be generated from the aerobic bacteria that are breeding. In addition, since the technology described in Patent Document 1 is intended to purify the BOD to be 30 ppm or less, the supply amount of ozone-containing air to be supplied is large, and necessary equipment and energy are required for this purpose.

  On the other hand, in the one described in Patent Document 2, it is proposed that ozone is directly supplied to the upper space of the septic tank or wastewater, and the ozone concentration in the air layer is maintained at 0.1 ppm or less to deodorize it. The ozone concentration required for deodorization on the air layer side is not taken into account in that it depends on the odor component concentration and the treatment time, and that the remaining ozone concentration also depends on the decomposition half-life. Therefore, in this conventional technology, in order to maintain a predetermined ozone concentration in the air layer, excessive equipment, excessive exhaust air volume and processing volume are designed, energy is consumed more than necessary, and costs increase. There was a problem of being out.

  The present invention has been made in view of such a point, and achieves a predetermined residual ion concentration in consideration of the decomposition half-life of ozone, and in an amount smaller than the supply amount of ozone-containing air in the prior art described above. The purpose is to prevent the generation of malodor from the storage tank.

In order to achieve the above object, the present invention detects the generation of malodor from a tank in which waste water having BOD load and organic SS load is present and the sum of BOD load + organic SS load is less than 50 kg / m ^3. In order to prevent this, a method of supplying ozone-containing air into the waste water in the tank, wherein the ozone concentration in the gas phase in the tank is D [ppb (volppb)], and the amount of exhaust air from the tank is E [M ³ / h], half-life of ozone in the air τ [h], ozone discharge concentration control upper limit target value from the exhaust system of the tank D ′ [ppb (volppb)], exhaust system of the tank When the internal volume is V [m ³ ], the exhaust system internal volume V is set so as to satisfy the following formula.
V> τ × (log (D / D ′) / log2) × E

  The concentration upper limit target value D ′ is, for example, a work environment reference value of 100 ppb (volppb: volume ppb; hereinafter, “ppb” indicates “volume ppb” unless otherwise specified) or a living environment reference value 50 ppb is adopted. Then, the supply ozone amount and the air amount are set so that the ozone concentration D in the space near the waste water surface is about 100 to 1000 ppb.

For example, when ozone-containing air is supplied to the wastewater surface at an ozone concentration of 500 ppb without dissolving, assuming that the air supply rate is 5 m ³ / h, the concentration at the exhaust port is 100 ppb and the ozone half-life in the air is Assuming 1.5h, the exhaust system volume V is
V> 1.5 × (log (500/100) / log2) × 5 · [m ³ ] = 17 m ³
By doing so, the concentration of ozone in the exhaust port becomes 100 ppb.

  Therefore, there is no need to constantly monitor the ozone concentration. An appropriate processing system can be constructed at the design stage. That is, it is possible to easily secure an exhaust system volume for attenuating ozone released into the air without being dissolved in the wastewater to a predetermined concentration at the design stage.

Regarding the daily supply amount Q [kg / day] of the ozone-containing air,
Q <{(BOD load + SS load) kg / day} × 50,
Supply amount Q ozone [kg / day] per day of pure water ozone in the ozone-containing air is
{(BOD load + SS load) kg / day} × 0.0001 <Q ozone <{(BOD load + SS load) kg / day} × 0.05,
It is good.

  First, according to the knowledge of the inventors, if the supply amount Q of ozone-containing air per day is about 50 times {(BOD load + SS load) kg / day}, the deodorizing purpose and the stirring effect can be sufficiently achieved. Therefore, it is sufficient to use equipment such as a blower and a pump that satisfies this condition, and the installation space, energy consumption, cost, etc. can be saved accordingly.

  The lower limit of the daily supply of ozone-containing air is naturally determined by the performance of the ozone generator, that is, the generated ozone concentration. For example, when an ozone generator using air as a raw material is used, since the generated ozone concentration is about 1% at the highest, 99% of the air is included.

  On the other hand, the lower limit value of the supply amount Q ozone [kg / day] per day of pure water ozone in ozone-containing air is considered as {(BOD load + SS load) according to the knowledge of the inventors in consideration of deodorization purposes. ) Kg / day} × 0.0001 is set from the viewpoint of necessity. If the upper limit of supply amount Q ozone [kg / day] is 0.05 times or more than {(BOD load + SS load) kg / day}, the equipment and equipment to be used, such as an ozone generator, will become larger. Since the price increases, considering the cost, it may be less than 0.05 times {(BOD load + SS load) kg / day}.

The deodorization system of the present invention is constructed as a system capable of carrying out the deodorization method, and includes a supply pipe for supplying ozone-containing air into the waste water of the storage tank, an exhaust pipe for exhausting the atmosphere in the tank to the outside of the tank, An ozone-containing air supply device that mixes ozone generated by the generator and air and sends the mixture to the supply pipe is provided. The ozone concentration in the gas phase in the tank is D [ppb (volppb)], the exhaust air volume from the tank is E [m ³ / h], the half-life of ozone in the air is τ [h], When the upper limit target value of ozone emission concentration control from the tank exhaust system is D ′ [ppb (volppb)] and the volume of the exhaust system inside the tank is V [m ³ ], the exhaust system is satisfied so that the following formula is satisfied. An internal volume V is set.
V> τ × (log (D / D ′) / log2) × E

  When constructed as a system, the internal volume of the exhaust system means the total volume of the space above the water surface of the reservoir (so-called gas phase part) and the inside of the exhaust pipe (the part up to the exhaust port leading to the atmosphere). .

  When the deodorization system is constructed according to the present invention, a sensor for measuring the concentration of ozone flowing through the exhaust pipe, and a control device for controlling supply from the ozone-containing air supply device based on the measurement result of the sensor are further provided. You may make it have. As a result, if the ozone concentration exceeds the specified value, the amount of ozone consumed in the wastewater has decreased, which means that the amount of organic substances including bacteria that are the source of odor has decreased. means. Therefore, the generation of odor can be prevented even if the ozone supply is stopped at that time. If such a state continues, the ozone concentration after the supply of air is reduced due to self-decomposition, so that the ozone-containing air is supplied again when the ozone concentration falls below a predetermined value. By repeating such an operation, the deodorizing performance is maintained, the exhaust ozone concentration is always below a predetermined value, and the operating cost can be saved.

  An ozone removing device capable of decomposing ozone may be further provided in the exhaust pipe or the exhaust system after the exhaust pipe. The ozone concentration decreases due to decomposition of odor components and self-decomposition, but if the concentration exceeds the upper limit target value, it is predicted that, for example, the ozone concentration at the exhaust port will be, for example, the work reference value (100 ppm) or more. It is effective in some cases.

  According to the present invention, by supplying a small amount of ozone-containing air, it is possible to prevent the generation of malodor in the wastewater storage tank, and this can be realized at low cost. In addition, the system design is easy to design and can be easily applied to existing equipment.

Hereinafter, preferred embodiments of the present invention will be described. FIG. 1 shows an outline of the malodor control system, and a lid 3 that covers the opening 2 is provided at the upper part of the storage tank 1. Further, a pipe 4 for allowing miscellaneous wastewater to flow into the tank and a pipe 5 for allowing kitchen wastewater to flow into the tank are connected to the upper portion of the storage tank 1. An exhaust pipe 6 for exhausting the atmosphere in the tank is connected to the upper part of the storage tank 1. This storage tank 1 is a facility in which kitchen wastewater and miscellaneous wastewater of 40 m ³ / day flow in and is used as a primary storage tank, and discharges sewage without performing detoxification.

  A drainage pump 11 is provided in the vicinity of the bottom in the storage tank 1, and waste water in the storage tank 1 is discharged to the outside through the drain pipe 12. In the vicinity of the bottom in the storage tank 1, an ozone-containing air discharge part 13 is provided. Outside the storage tank 1, there are provided a blower 14 that takes in air and sends it, and an ozone generator 15 that generates ozone from the surrounding air. The ozone generated in the ozone generator 15 and the air from the blower 14 Are mixed and supplied as ozone-containing air to the discharge unit 13 through the air supply pipe 16, and the ozone-containing air is supplied to the wastewater in the storage tank 1 through the discharge unit 13.

  Next, a specific example of the deodorizing method using this system will be described. In the storage tank 1, drainage is performed to the sewage side by the drainage pump 11 because of the necessity of pumping up to the sewer pipe. However, at night and on holidays when wastewater does not flow in, it is stored for a long time at the minimum set water level, so it becomes an anaerobic state, which is the largest cause of bad odor, and bad odor is generated. This bad odor leaks not only through the exhaust pipe 6 but also into the room where the storage tank 1 is installed, for example, the basement, from the gap of the manhole, which causes a long-term problem.

  According to the system according to the above-described embodiment, the ozone-containing air is supplied from the discharge unit 13 into the storage tank 1, so that the growth of bacteria that are a source of malodor is suppressed. Moreover, since ozone-containing air is directly sent to wastewater, the growth of anaerobic bacteria, which cause the generation of malodors, is also suppressed by avoiding complete anaerobic conditions. The odor components partially released from the surface of the wastewater into the gas phase are also decomposed including odor components other than those derived from bacteria by the action of residual ozone that is not absorbed by the liquid phase. Therefore, generation of malodor from the storage tank 1 is prevented.

Next, examples will be described. The ozone concentration in the gas phase in the storage tank 1 is 500 [ppb] for D, the exhaust air volume E is 5 [m ³ / h], the half-life time τ of ozone in the air is 1.5 [h], and the ozone is discharged. If the concentration control upper limit target value D ′ is set to 100 [ppb], the exhaust system internal volume V of the tank is
From V> τ × (log (D / D ′) / log2) × E,
It should be larger than 7.1 [m ³ ]. Thus, the ozone concentration at the exhaust port 6a of the exhaust pipe 6 can be set to 100 [ppb]. The exhaust system internal volume V in FIG. 1 is the volume V0 of the gas phase part in the storage tank 1 (the space part partitioned by the water surface of the wastewater and the lid 3 in the storage tank 1) and the exhaust port of the exhaust pipe 6. It is the sum of the volume V1 up to 6a.

Further, examples of the total supply amount of ozone-containing air and the ozone supply amount according to the present invention are determined as follows, for example.
First, for miscellaneous wastewater, 10 m ³ per day, BOD load in miscellaneous wastewater is 100 g / m ³ , SS load is 50 g / m ³ ,
For kitchen drainage, 30 m ³ per day, BOD load in miscellaneous drainage is 600 g / m ³ , SS load is 200 g / m ³ ,
If (BOD load + SS load) kg / day is X,
X = (100 + 50) × 10 + (600 + 200) × 30 = 25500 [g / day] = 25.5 kg / day Therefore, the total supply amount Q [kg / day] of ozone-containing air per day is
Q <25.5 kg / day × 50 = 75 kg / day is set.

On the other hand, the supply quantity Q ozone [kg / day] of pure ozone in the ozone-containing air is
(25.5 kg / day × 0.0001 = 0.026 kg / day) <Q ozone <(25.5 kg × 0.005 = 1.275 kg / day)
Thus, 0.0026 kg <Q ozone <1.275 kg.
In the examples, Q ozone was set to 0.018 kg / day.

  From the above, the ozone concentration of the ozone-containing air is 0.018 / 72 = 25 ppm. The amount of ozone dissolved in the wastewater varies depending on the depth of the storage tank 1, water temperature, air supply method, stored water quality, etc. In this example, the concentration of ozone in the open supply air to the atmosphere side depends on the conditions of the applicable facility. The optimal ozone air supply method can be determined. Therefore, at the system design stage, the purpose of deodorization is sufficient, and it is possible to comply with a desired value, for example, a standard value for living environment, for the ozone concentration in the air after the deodorization treatment is discharged. The total supply amount Q of the ozone-containing air is determined by the range in which the stored water in the tank can be stirred only by this supply.

  Further, actual evaluation of the above-described embodiment will be described. The processing conditions of the above-described embodiment are set as condition 1, and as the comparison target conditions, the total supply amount of ozone-containing air is the same, and the pure ozone supply amount is set as the lower limit (0.0026 kg). The results of comparison with the case where no measures were taken were evaluated as follows.

  The evaluation before and after the application of the deodorizing method according to this example is qualitative, but “1: unpleasant odor is strong, 2: unpleasant odor is present, 3: unpleasant odor is present, but smell is present, 4: almost odor is present. It was performed by 3 subjects in 4 stages of “No”. The results are shown below.

Before countermeasure: 1 + 2 + 1 = 4 points After countermeasure for condition 1: 3 + 3 + 4 = 10 points After countermeasure for condition 2: 2 + 3 + 2 = 7 points

  The measure under Condition 1 clearly shows the improvement effect. On the other hand, the results under Condition 2 (lower limit) show that the improvement effect is clear, but the level of achievement of deodorization is insufficient. Regarding the cost, compared with the conventional countermeasures using only air supply, the initial cost under Condition 1 is almost the same, but the simulation result that the present invention is about 1/3 in terms of the operating cost is obtained. It was. In addition, with respect to the countermeasures by installing a conventional deodorizing device in the air system, the present invention is much cheaper at the initial cost, and the operating cost varies greatly depending on the replacement frequency of the deodorizing filter, etc. The result was that it was much cheaper.

Next, another embodiment will be described. In FIG. 2, a partition plate 21 for horizontally partitioning the gas phase portion is provided in the gas phase portion in the storage tank 1. An opening 21 a is formed in the partition plate 21, and the opening 21 a is closed with a lid 22. Therefore, in this case, the gas phase portion above the partition plate 21 has a volume V0. The volume V0 can be arbitrarily adjusted by changing the vertical position of the partition plate 21 in the tank (that is, changing the vertical position). In order to make it possible to change the vertical position of the partition plate 21 in the tank, for example, the peripheral portion of the partition plate 21 is configured to be slidable on the inner wall of the storage tank 1, and the partition plate 21 is moved by an appropriate drive source. It can be proposed to move up and down. In such a case, for example, if a guide such as a rail or a groove is formed on the inner wall of the storage tank 1 and a member that fits the guide is provided at the peripheral edge of the partition plate 21, the partition plate 21 is kept stable while being maintained in a horizontal state. Can be moved up and down. As the vertical movement mechanism itself, for example, a worm gear device may be used, or another mechanism may be employed in which the partition plate 21 is suspended by a wire, and the wire is wound and unwound by a motor or the like.
In addition, for example, if a step is provided on the inner wall of the storage tank 1 or an upright wall provided on the inner side of the storage tank 1 and the partition plate 21 is fitted to this, the type of the partition plate is appropriately changed and set. As a result, the position in the vertical direction can be changed, and the volume V0 can be adjusted.

  In the example of FIG. 2, a sensor 31 for detecting the ozone concentration is further provided in the exhaust pipe 6, and the measurement result is input to the control device 32. The control device 32 performs start / stop control on the ozone generator 15 based on the measurement result.

  According to the system of FIG. 2 as described above, it is possible to set the ozone supply amount and supply concentration higher, and the system is improved in the following points with respect to the example of FIG. That is, it becomes possible to supply ozone at a higher concentration, and the odor prevention performance is improved. Also, more reliable management of ozone exhaust concentration is possible. Furthermore, depending on the quality of the wastewater, the amount of supply ozone in the liquid phase may increase, and the gas phase concentration may decrease drastically. However, as in the system of FIG. By controlling the ozone generator 15 based on this, it is possible to always control the ozone concentration to a predetermined concentration. This makes it possible to reliably treat malodorous components that can be partially released into the gas phase. When the consumption of ozone in the liquid phase decreases when the water quality is cleaner, in the example of FIG. 1, the same amount is always supplied even in such a case, but waste occurs, but in the example of FIG. Since the start and stop of the generator 15 can be controlled, the ozone generator 15 is stopped when the water quality is relatively clean, so there is no waste.

  Still another embodiment will be described. In FIG. 1 and FIG. 2, the waste water is agitated by the ozone-containing air sent from the discharge unit 13 into the waste water. In the example of FIG. 3, the operation is performed by the driving source 41 such as a motor during the liquid phase. A stirrer 42 is installed. As a result, it is possible to reduce the supply amount of ozone-containing air that has been sent from the discharge unit 13 to the wastewater in order to achieve a stirring effect, and the stirring effect itself is high. Therefore, the blower 14 itself becomes unnecessary. And since the agitation effect is high, the risk of generating local anaerobic spots is reduced, and ozone reliably reaches every corner of the wastewater in the storage tank 1, and as a result, reliability of suppressing malodorous sources in the liquid phase. Is further improved.

  Further, as shown in FIG. 3, an ozone removing device 43 capable of ozone decomposition treatment may be separately provided at the exhaust port 6a of the exhaust pipe 6. As a result, it is possible to prevent a situation in which the ozone concentration in the exhaust gas exhausted through the exhaust pipe 6 exceeds a predetermined environmental standard value, for example. The ozone removing device 43 may be installed at any location as long as it is an exhaust system of the storage tank 1 such as in the middle of the exhaust pipe 6.

  The present invention is useful for deodorizing treatment of wastewater.

It is explanatory drawing which shows the outline | summary of the deodorizing system concerning embodiment. It is explanatory drawing which shows the outline | summary of the deodorizing system concerning other embodiment provided with the partition plate and the density | concentration sensor. It is explanatory drawing which shows the outline | summary of the deodorizing system concerning other embodiment provided with the stirrer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Storage tank 4,5 Piping 6 Exhaust pipe 6a Exhaust port 11 Drain pump 12 Drain pipe 14 Blower 15 Ozone generator

Claims (6)

To BOD load and organic SS load is present, the sum of BOD load + organic SS load to prevent malodor generation from the tank that stores the wastewater of less than 50 kg / m ^3, the tanks containing ozone air A method of supplying the wastewater in
The ozone concentration in the gas phase in the tank is D [ppb (volppb)], the exhaust air volume from the tank is E [m ³ / h], the half-life of ozone in the air is τ [h], and the tank When the upper limit target value of ozone emission concentration control from the exhaust system is D ′ [ppb (volppb)] and the internal volume of the exhaust system of the tank is V [m ³ ], the contents of the exhaust system satisfy the following formula: A foul odor prevention method characterized by setting the product V.
V> τ × (log (D / D ′) / log2) × E The supply amount Q [kg / day] of the ozone-containing air per day is
Q <{(BOD load + SS load) kg / day} × 50,
The supply amount Q ozone [kg / day] of pure water ozone in the ozone-containing air per day is
{(BOD load + SS load) kg / day} × 0.0001 <Q ozone <{(BOD load + SS load) kg / day} × 0.05
The malodor control method according to claim 1, wherein: A system for preventing the generation of malodor from a tank storing wastewater,
A supply pipe for supplying ozone-containing air into the waste water of the tank;
An exhaust pipe for exhausting the atmosphere in the tank to the outside of the tank;
An ozone-containing air supply device that mixes ozone generated by the ozone generator and air and sends the mixture to the supply pipe;
Have
The ozone concentration in the gas phase in the tank is D [ppb (volppb)], the exhaust air volume from the tank is E [m ³ / h], the half-life of ozone in the air is τ [h], and the tank When the upper limit target value of ozone emission concentration control from the exhaust system is D ′ [ppb (volppb)] and the internal volume of the exhaust system of the tank is V [m ³ ], the contents of the exhaust system satisfy the following formula: Odor control system characterized by setting product V.
V> τ × (log (D / D ′) / log2) × E 4. A sensor for measuring the concentration of ozone flowing through the exhaust pipe, and a control device for controlling supply from the ozone-containing air supply device based on a measurement result of the sensor. Odor prevention system as described in. The malodor control system according to claim 4, further comprising an ozone removing device capable of decomposing ozone in the exhaust pipe or an exhaust system after the exhaust pipe. The malodor according to any one of claims 3 to 5, further comprising a partition plate for horizontally partitioning a gas phase portion of the tank, wherein the partition plate can be repositioned in a vertical direction in the tank. Prevention system.

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