JP4981628B2 - Wastewater treatment equipment - Google Patents

Description

  The present invention relates to a wastewater treatment apparatus in which the entire apparatus does not become large, the sludge generation rate can be lowered, and even when an oxygen-free state continues for a long period of time, a decaying odor such as hydrogen sulfide is hardly generated.

  2. Description of the Related Art Conventionally, an activated sludge method in which organic matter in wastewater is oxidized and decomposed by aerobic microorganisms (activated sludge) to treat wastewater is widely used. However, surplus sludge generated in this treatment process is periodically carried out and disposed of by a cleaning company, but this surplus sludge disposal cost is rising year by year, and the maintenance cost tends to be high. In addition to the problem of maintenance costs, there is a demand for a wastewater treatment apparatus that prevents excessive sludge from being generated as much as possible from the influence on the global environment.

Therefore, conventionally, there is a wastewater treatment apparatus using hypochlorous acid, ozone, alkali, etc. for solubilization of sludge so as to suppress the generation of excess sludge (see, for example, Patent Documents 1 to 3).
JP 2007-209889 A JP 2006-314911 A JP 2005-246346 A

  However, in the above-described conventional wastewater treatment device, for example, when the aeration is continued when there is a problem that the whole device becomes large, or when wastewater is not generated due to, for example, a long-term leave of a factory, aerobic microorganisms eat nutrients. In some cases, aeration may be restricted in order to cause a problem. However, when the amount of aeration is insufficient, there is a problem that a spoiled odor such as hydrogen sulfide is generated by the action of anaerobic microorganisms.

  The present invention has been made in view of such points, and the entire apparatus is not overwhelmed, the sludge generation rate can be lowered, and even when anoxic conditions continue for a long time, almost all of the decaying odors such as hydrogen sulfide are generated. An object is to provide a wastewater treatment apparatus that does not.

The waste water treatment apparatus according to claim 1 is a regulating tank into which waste water flows, a first reaction tank into which waste water from the regulating tank flows and humic substances and silicates are introduced, and from the first reaction tank A second reaction tank into which wastewater flows, a precipitation tank into which wastewater from the second reaction tank flows in, and separates the inflowed wastewater into sludge and supernatant treated water; drainage in the adjustment tank; Intermittent aeration means for intermittent aeration of the waste water in one reaction tank and the waste water in the second reaction tank, and sludge return for returning sludge precipitated in the sedimentation tank to the adjustment tank and the first reaction tank A charging unit containing the humic substance and the silicate is disposed in the first reaction tank, and the intermittent aeration means is disposed in the adjustment tank. A first aeration section for intermittently supplying air to the waste water, and the first reaction tank A second aeration unit that intermittently supplies air to the waste water in the first reaction tank, and a lower vicinity of the charging unit in the first reaction tank, and the humic substances in the charging unit and the It has a 3rd aeration part which stirs a silicate, and a 4th aeration part which is arrange | positioned in the said 2nd reaction tank and supplies air intermittently to the waste_water | drain in this 2nd reaction tank .

  The waste water treatment apparatus according to claim 2 is the waste water treatment apparatus according to claim 1, wherein the sludge return rate, which is the ratio of the sludge return amount to the waste water inflow amount flowing into the adjustment tank, is 150% to 320%. .

  The waste water treatment apparatus according to claim 3 is the waste water treatment apparatus according to claim 1 or 2, wherein the intermittent aeration means includes at least intermittent aeration for the waste water in the first reaction tank and intermittent aeration for the waste water in the second reaction tank. Are performed simultaneously.

  The wastewater treatment device according to claim 4 is the wastewater treatment device according to any one of claims 1 to 3, wherein the ratio of the sludge return amount returned to the adjustment tank and the sludge return amount returned to the first reaction tank. Is 2 to 8.

  According to the first aspect of the present invention, since the humification reaction can be stably caused by the input of humic substances and silicates and the intermittent aeration by the intermittent aeration means, the entire apparatus does not become large, and the sludge The rate of occurrence can be lowered, and even if anoxic conditions continue for a long time, there is almost no rot odor such as hydrogen sulfide.

  According to the invention which concerns on Claim 2, since a sludge return rate is 150%-320%, while being able to reduce nitrogen in waste water effectively, the sedimentation property of the sludge in a sedimentation tank can be improved.

  According to the invention of claim 3, the intermittent aeration means simultaneously performs intermittent aeration for the wastewater in the first reaction tank and intermittent aeration for the wastewater in the second reaction tank. Therefore, even if the ecosystem balance of the microorganism group in the first reaction tank is lost, the ecosystem balance of the microorganism group in the second reaction tank changes accordingly, and the entire system balance is maintained. , Stable wastewater treatment can be performed.

  According to the invention which concerns on Claim 4, the ratio of the sludge return amount returned to the adjustment tank and the sludge return amount returned to the 1st reaction tank is set to 2 to 8, and phosphorus in the supernatant treated water is thereby reduced. It can be effectively reduced.

  An embodiment of the waste water treatment apparatus of the present invention will be described with reference to the drawings.

  In FIG. 1, 1 is a waste water treatment device, and this waste water treatment device 1 purifies organic waste water containing organic matter discharged from a food factory, for example.

  The wastewater treatment apparatus 1 includes a regulating tank 5 into which wastewater (raw water) from a drain pipe 3 of a drainage facility 2 such as a food factory flows, for example. In the adjustment tank 5, drainage with unstable water quality or the like flowing through the drain pipe 3 is temporarily stored, and stabilization of drainage water quality or the like on the downstream side is achieved.

  In addition, the waste water treatment apparatus 1 includes three tanks, that is, a first reaction tank (for example, a culture reaction tank) 6 into which waste water from the adjustment tank 5 flows and humic substances and silicate are introduced. A second reaction tank (for example, a culture accelerating tank) 7 into which the waste water from the first reaction tank 6 flows, and a waste water from the second reaction tank 7 flows into the sludge and supernatant by precipitation separation. A sedimentation tank 8 is provided for separation into treated water.

  The adjustment tank 5 and the first reaction tank 6 are connected by a first connection pipe 11, the first reaction tank 6 and the second reaction tank 7 are connected by a second connection pipe 12, and the second reaction tank 7 and The settling tank 8 is connected to the third connecting pipe 13. The settling tank 8 is connected to a discharge pipe 14 for discharging the supernatant treated water in the settling tank 8 to the outside of the apparatus.

  A metering pump (not shown), which is a pressure feeding means, is provided in the middle of the first connecting pipe 11, and the wastewater in the adjustment tank 5 is sent to the first reaction tank 6 by a certain amount by the operation of this metering pump. The second connection pipe 12 and the third connection pipe 13 are overflow pipes, and the waste water in the first reaction tank 6 is sent to the second reaction tank 7 through the second connection pipe 12 due to overflow. Waste water in the reaction tank 7 is sent into the precipitation tank 8 through the third connecting pipe 13 by overflow.

  In addition, in the first reaction tank 6, a charging unit 21 in which humic substances and silicates are placed is disposed, and this charging unit 21 is disposed so as to be immersed in the upper part of the first reaction tank 6, for example. The charging unit 21 is, for example, a mesh bag or a wire mesh basket containing humic substances and silicate.

The humic substance is extracted from, for example, terrestrial (forest) soil, seabed sediment, etc., and its structural formula is a macromolecular organic substance similar to tannin and lignin. Humic substances are decomposed by filamentous fungi, bacteria, etc. to produce nutrients (amino acids, nucleic acids, vitamins, hormones) necessary for the growth of plants, and finally, such as CO ₂ , water, NH ₃ , nitrates, phosphates, etc. Converted to inorganic material.

  Further, the waste water treatment apparatus 1 includes an intermittent aeration means 22 that simultaneously performs intermittent aeration on the waste water in the adjustment tank 5, the waste water in the first reaction tank 6 and the waste water in the second reaction tank 7, And sludge returning means 23 for distributing and returning the sludge (activated sludge) deposited in step 1 to the upstream adjustment tank 5 and the first reaction tank 6.

  The intermittent aeration means 22 performs aeration and stop for the three aeration tanks 5, 6, 7 simultaneously. The intermittent aeration means 22 is arranged at the lower part in the adjustment tank 5 and is provided at the lower part in the first reaction tank 6 and the first aeration part 31 for intermittently supplying air to the waste water in the adjustment tank 5. A second aeration unit 32 for intermittently supplying air to the waste water in the tank 6 and a third aeration for stirring the humic substances, silicates, etc. in the charging unit 21 disposed near the lower part of the charging unit 21 in the first reaction tank 6. And a fourth aeration unit 34 that is disposed in the lower part of the second reaction tank 7 and intermittently supplies air to the waste water in the second reaction tank 7. Each aeration part 31, 32, 33, 34 is, for example, an air diffuser tube in which a plurality of holes are formed.

  The first to fourth aeration units 31, 32, 33, 34 are connected to one blower 41 via branch pipes 36, 37, 38, 39 and a common pipe 40, and each branch pipe 36, Valves 42, 43, 44, 45 for adjusting the air amount for adjusting the amount of air flowing through the branch pipes 36, 37, 38, 39 are provided in the middle of 37, 38, 39, respectively.

  And by the one blower 41 of the intermittent aeration means 22, the intermittent aeration with respect to the waste_water | drain in the adjustment tank 5, the intermittent aeration with respect to the waste_water | drain in the 1st reaction tank 6, and the intermittent aeration with respect to the waste_water | drain in the 2nd reaction tank 7 are carried out. Done at the same time. In other words, the operation and stop timings of the aeration blower 41 are the same for the three tanks 5, 6, and 7. For example, the aeration blower 41 is set to turn on and off every 15 minutes.

  The sludge return means 23 has a sludge return pipe 51 having one end connected to the settling tank 8 and the other end connected to the adjustment tank 5 and the first reaction tank 6. A pump 52 that distributes and returns sludge precipitated in the tank 8 to the adjusting tank 5 and the first reaction tank 6 through the sludge return pipe 51 is provided.

  The blower 41 and the pump 52 are connected to control means (not shown) for controlling the blower 41 and the pump 52. And based on control of a control means, the sludge return rate which is a ratio of the sludge return amount with respect to the waste water inflow amount which flows into the adjustment tank 5 is set to a certain value within the range of 150% to 320%. The ratio of the sludge return amount returned to the adjustment tank 5 and the sludge return amount returned to the first reaction tank 6 is set to 2 to 8.

  Next, the operation of the waste water treatment apparatus 1 will be described.

  Drainage from the drainage facility 2 such as a food factory flows into the adjustment tank 5 through the drainage pipe 3 and is temporarily stored in the adjustment tank 5.

  The waste water in the adjustment tank 5 flows into the first reaction tank 6 through the first connection pipe 11 by the operation of the metering pump, and the waste water in the first reaction tank 6 passes through the second connection pipe 12 due to overflow. The waste water in the second reaction tank 7 flows into the second reaction tank 7 and flows into the sedimentation tank 8 through the third connection pipe 13 due to overflow.

  The wastewater that has flowed into the settling tank 8 is separated into solid and liquid sludge and supernatant treated water by sedimentation, and the supernatant treated water is discharged to the outside of the apparatus through the discharge pipe 14, and the sludge is returned to the sludge return pipe. It returns to the adjustment tank 5 and the 1st reaction tank 6 through 51.

  And in the adjustment tank 5, the 1st reaction tank 6, and the 2nd reaction tank 7, in the aerobic state in which aeration is performed by the action | operation of the blower 41 of the intermittent aeration means 22, the organic substance in waste_water | drain etc. are activated sludge. It is oxidatively decomposed by aerobic microorganisms and the waste water is purified.

  Moreover, in the 1st reaction tank 6, a temporary anaerobic state is produced by the stop of the blower 41 of the intermittent aeration means 22, and humification reaction generate | occur | produces by the effect | action of humic substance and a silicate. In this humus reaction, autotrophic bacteria (facultative anaerobic bacteria) contained in humic substances grow with silicate as energy to produce organic matter, and microorganisms grow with the organic matter as nutrient source. The wastewater purification process proceeds.

  The waste water from the second reaction tank 7 is separated into sludge and supernatant treated water in the sedimentation tank 8, but at this time, the settled sludge is retained under anaerobic conditions, so this retention time is long. Indeed, a large amount of phosphorus taken into the sludge is released into the waste water, and the phosphorus concentration of the supernatant treatment water in the sedimentation tank 8 increases.

  Therefore, by repeating sludge return, phosphorus is prevented from being released into the discharge water that is the supernatant treatment water of the sedimentation tank 8. This means that the sludge return rate is greatly related to the re-elution of phosphorus, but the problem is how the sludge was exposed to the aerobic state before reaching the sedimentation tank 8. It becomes. On the other hand, in order to strengthen the aerobic state, a method of increasing the ratio of the operation time of the blower 41 in intermittent aeration can be considered, but the wastewater treatment apparatus 1 focuses on the stability of the treatment against fluctuations in wastewater. Since the aeration conditions of the three tanks 5, 6, and 7 (at least the first reaction tank 6 and the second reaction tank 7) are unified and managed, the autotrophic bacteria contained in the humic substance of the first reaction tank 6 The time that the group is exposed to anaerobic conditions is reduced, weakening its function. Therefore, by returning the returned sludge not only to the first reaction tank 6 but also to the adjustment tank 5, the sludge can be obtained by extending the time of exposure to the aerobic state without breaking the balance between the aerobic state and the anaerobic state. Can promote the uptake of phosphorus.

  The operation and stop timings of the blower 41 of the intermittent aeration means 22 are the same in the three tanks 5, 6, 7, but the air amount adjusting valves 42, 43, By adjusting the opening degree of 44 and 45, it is necessary to set DO (dissolved oxygen) optimum for the reaction in each of the tanks 5, 6, and 7.

  For example, the DO of the first reaction tank 6 is set to 0.3 to 0.7 smaller than the DO of the second reaction tank 7, and the DO of the second reaction tank 7 is set to about 2.0. In particular, in the first reaction tank 6, DO (dissolved oxygen) needs to be reduced to 0 at least partially while the blower 41 is stopped.

  Thus, according to the waste water treatment apparatus 1, since the humification reaction can be stably caused by the input of humic substances and silicate and the intermittent aeration by the intermittent aeration means 22, the entire apparatus does not become large. The sludge generation rate can be lowered, and even if the oxygen-free state continues for a long period of time, there is almost no spoilage odor such as hydrogen sulfide.

  Moreover, since the sludge return rate is 150% to 320%, it is possible to effectively reduce nitrogen in the wastewater and improve the sedimentation property of the sludge in the settling tank 8. This means that if the sludge return rate is too low, TN (total nitrogen) cannot be reduced sufficiently. Conversely, if the sludge return rate is too high, the sludge suction force from the settling tank 8 is too high, and the precipitation This is because the sludge in the tank 8 is rolled up and the supernatant treated water cannot be discharged efficiently. Furthermore, if the sludge return rate is too high, the environment of each tank 5, 6, 7 will be made uniform, that is, the difference between each tank 5, 6, 7 will disappear, and the role of wastewater treatment that each played will collapse. The water quality will deteriorate.

  Furthermore, the intermittent aeration means 22 performs intermittent aeration on the waste water in the first reaction tank 6 and intermittent aeration on the waste water in the second reaction tank 7 at the same time. Even if the ecological balance of the six microbial groups is lost, the ecological balance of the microbial groups in the second reaction tank 7 changes correspondingly, and the overall balance of the system is maintained. Waste water treatment can be performed. In addition, each blower 41 can easily control each of 5, 6, and 7, and the manufacturing cost can be reduced, and maintenance is easy.

  Moreover, phosphorus in the supernatant treated water can be effectively reduced by setting the ratio of the amount of sludge returned to the adjustment tank 5 and the amount of sludge returned to the first reaction tank 6 to 2: 8. That is, in a sufficiently aerobic state, the sludge is in a state of holding phosphorus, and if the anaerobic state continues, the sludge releases phosphorus, so the aeration time in the second reaction tank 7 is lengthened to promote the aerobic state, Even if the aeration time in the first reaction tank 6 is shortened to promote the anaerobic state, the phosphorus concentration in the supernatant treated water is reduced. However, in this case, when the concentration or amount of waste water from the drainage facility 2 changes, there is a high risk that the balance of the entire apparatus will be greatly disrupted. On the other hand, if sludge return is performed so that the ratio of the sludge return amount returned to the adjustment tank 5 and the sludge return amount returned to the first reaction tank 6 is 2 to 8, the total residence time is long. Since the aerobic state can be promoted, the above risk can be reduced and phosphorus in the supernatant treated water can be effectively reduced.

  The ratio of the amount of sludge returned to the adjustment tank 5 and the amount of sludge returned to the first reaction tank 6 is set to 2: 8, the aeration time is 15 minutes, on / off, and the sludge on the side of the sedimentation tank In order to prevent winding up, the sludge return amount was set to 320% and the test was conducted. Table 1 shows the test conditions.

  The average MLSS of the adjustment tank 5 and the reaction tanks 6 and 7 on December 1 increased from 4900 mg / L to the average MLSS = 6367 mg / L after 22 days. The average inflow BOD for 22 days was 1034 mg / L.

When the total BOD amount for 22 days is expressed by the following formula Total BOD amount = Daily raw water inflow amount × 22 days × BOD average value
= A 1.0 m3 / day × 22 days × 1034g / m ³ = 22748g.

On the other hand, the increase amount ΔMLSS of the sludge in the tank after 22 days can be calculated as (6367-4900 g / m 3) × 2.4 m ³ = 3521 g, assuming the tank capacity to be 2.4 m ³ .

  Therefore, since the total BOD amount of 22748 g is converted to 3521 g of sludge, the sludge generation rate is 15.5%.

In addition, experience that MLSS has increased to 6000mg / L, water temperature has decreased from 22 to 10 ° C, and the sludge concentration in the aeration tank at the facility is 5000mg / L, SV30 = 98 or higher. As a result, it was possible to maintain sludge sedimentation even at high MLSS. BOD volume load at this time, day raw water inflow × BOD average split / biological tank (3 tank × 0.8 m ³⁾ = 1 m ³ / day ^{× 1034g / m 3 /1000/2.4m 3 =} 0.43kg / m 3 When subtracting the day adjustment tank, the total of the two reaction tanks was 0.65 kg / m ³ days.

  Next, Tables 2 and 3 show the results of water collection after the test conditions were stabilized (December 15th and 22nd). In addition, Table 4 and FIG. 2 show the water sampling results of the TN concentration and the TP concentration in the treated water.

  During the test period, the TN concentration in the treated water was 2.5 to 3.4 mg / L, and the TP concentration was 1.4 to 6.0 mg / L. In addition, it was effective not only for BOD and SS but also for nitrogen removal when the water temperature in the microbial tank was less than 10 ° C, and stable treatment could be continued even under water temperature conditions that were difficult to treat with the aerobic biological method represented by the activated sludge method. .

  In the activated sludge method represented by the aerobic biological treatment method, organic substances are oxidatively decomposed by aerobic microorganisms and converted into carbon dioxide, water, and excess sludge. Since the blower is operated for 24 hours in the processing step, the power cost becomes a burden, and the problem of energy saving becomes obvious. This test method combines humic synthesis and organic oxidation of complex microorganisms, not organic oxidation of bacteria, protozoa and metazoans, by introducing humic substances and silicates into activated sludge. However, unlike the activated sludge method, which is widely applied, the power cost can be reduced by about 50% by intermittently operating the blower.

  Moreover, the sludge generation rate is also less than 20%, and the generation rate can be suppressed to about 50 to 60% in comparison with the activated sludge method.

It is a lineblock diagram of the waste water treatment equipment concerning one embodiment of the present invention. It is a graph which shows the water sampling result of TN density | concentration in treated water, and TP density | concentration.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Waste water treatment equipment 5 Adjustment tank 6 1st reaction tank 7 2nd reaction tank 8 Sedimentation tank
21 input unit
22 Intermittent aeration means
23 Sludge return means
31 1st aeration part
32 2nd aeration part
33 3rd aeration part
34 4th aeration part

Claims (4)

An adjustment tank into which wastewater flows,
A first reaction tank into which waste water from the adjustment tank flows and humic substances and silicate are introduced;
A second reaction tank into which waste water from the first reaction tank flows,
Waste water from the second reaction tank flows in, and a sedimentation tank that separates the inflow waste water into sludge and supernatant treated water;
Intermittent aeration means for performing intermittent aeration on the waste water in the adjustment tank, the waste water in the first reaction tank and the waste water in the second reaction tank;
A sludge return means for returning the sludge precipitated in the settling tank to the adjustment tank and the first reaction tank ,
In the first reaction tank, a charging unit containing the humic substance and the silicate is disposed,
The intermittent aeration means includes
A first aeration unit that is arranged in the adjustment tank and intermittently supplies air to the drainage in the adjustment tank;
A second aeration unit disposed in the first reaction tank and intermittently supplying air to the waste water in the first reaction tank;
A third aeration unit disposed in the lower vicinity of the charging unit in the first reaction tank, and stirring the humic substance and the silicate in the charging unit;
A wastewater treatment apparatus comprising a fourth aeration unit that is disposed in the second reaction tank and intermittently supplies air to the wastewater in the second reaction tank . The wastewater treatment apparatus according to claim 1, wherein a sludge return rate, which is a ratio of a sludge return amount to a wastewater inflow amount flowing into the adjustment tank, is 150% to 320%. The waste water treatment apparatus according to claim 1 or 2, wherein the intermittent aeration means simultaneously performs at least intermittent aeration of the waste water in the first reaction tank and intermittent aeration of the waste water in the second reaction tank. The wastewater treatment apparatus according to any one of claims 1 to 3, wherein the ratio of the amount of sludge returned to the adjustment tank and the amount of sludge returned to the first reaction tank is 2 to 8.

Images