JP2006088116A - Method and device for waste water treatment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste water treatment method and a device therefor where the amount of sludge caused by biological treatment itself can be reduced. <P>SOLUTION: The waste water treatment device comprises: a control tank 1 into which the raw water of exhaust water is introduced, and performing the control of its concentration, the inflow amount, or the like; a denitrification tank 2 for removing nitrogen in the waste water; a biological treatment tank 3 composed of a first aerator 3a, a second aerator 3b, a third aerator 3c and a fourth aerator 3d performing biological treatment; a precipitator 4 for separating water and sludge after the biological treatment; and a sterilization tank 5 for performing the sterilization of the water separated by the precipitator 4. An oxidation tank 7 as the front step of the first aerator 3a and also as the post step of the denitrification tank 2 is jointly provided with an ozone treatment apparatus 8 circulating water in the oxidation tank 7 and dissolving ozone. The ozone treatment apparatus 8 sucks the water in the oxidation tank 7, dissolves ozone into the sucked water so as to cause oxidation treatment, and returns the same into the oxidation tank 7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wastewater treatment method and apparatus for biologically treating wastewater such as sewage, human waste, factory wastewater and domestic wastewater.

  The most common method for treating wastewater containing organic matter such as sewage, human waste, industrial wastewater, and domestic wastewater is an activated sludge method in which biological treatment with aerobic microorganisms is performed. In the activated sludge method, activated sludge composed of many types of microorganisms purifies wastewater by decomposing organic matter in the wastewater. On the other hand, in this process, microorganisms repeat growth, proliferation, and death (sludge) using organic matter in the wastewater as a nutrient source. Some of the sludge microorganisms are decomposed again by biological treatment, but some become excess sludge.

  Although excess sludge is being reused as a soil conditioner and compost material, most of it is industrial waste, so volume reduction of this excess sludge has become a major issue. Conventionally, as a technique for reducing the volume of this excess sludge, for example, as described in Patent Documents 1 and 2, a method of treating the excess sludge with ozone and biologically treating it again has been proposed.

JP 2003-340485 A (2nd page, right column, lines 27-37, 3rd page, left column, lines 4-6) JP-A-7-96297 (page 3, left column, lines 27-46, FIG. 1)

  By the way, the capacity of the aeration tank for performing biological treatment is calculated and set by the amount of SS (floating matter) and BOD (biochemical oxygen demand) in the waste water. The amount of air supplied to the microorganisms in the aeration tank is also set according to the SS amount, BOD, and microorganism concentration. The conventional sludge volume reduction methods as described in Patent Documents 1 and 2 do not affect the calculation of the capacity of the aeration tank because the sludge after biological treatment is treated. .

  Generally, it is said that about 40% of the BOD of water for biological treatment is sludged. There have been no studies on reducing the amount of sludge generated by this biological treatment. The sludge volume reduction methods described in Patent Documents 1 and 2 have been studied on how to efficiently reduce the volume of generated sludge.

  An object of the present invention is to provide a wastewater treatment method and apparatus capable of reducing the amount of sludge generated by biological treatment.

  The wastewater treatment method of the present invention is a wastewater treatment method for biologically treating wastewater, characterized by performing biological treatment after circulating water before biochemical treatment to dissolve ozone. To do. Moreover, the wastewater treatment apparatus of the present invention is a wastewater treatment apparatus for treating wastewater with a biochemical treatment tank, and circulates water in the previous stage of the biological treatment tank to dissolve ozone. It is equipped with.

  According to the invention, since the wastewater is cyclically treated with ozone before being biochemically treated, the biodegradable organic matter in the wastewater is decomposed, and BOD, COD (chemical oxygen demand) corresponding to this amount is decomposed. Amount), SS amount decreases. If the amount of BOD, COD, and SS in the waste water is reduced, the amount of microorganisms in biological treatment can be reduced, and the amount of sludge generated by this biological treatment is also reduced.

  Here, when waste water that requires a large amount of nitrogen and needs to be denitrified is treated, it is desirable to perform denitrification before dissolving ozone. In the wastewater treatment apparatus of the present invention, it is desirable to provide the ozone treatment apparatus at the subsequent stage of the denitrification tank. Since denitrification in wastewater usually requires BOD and is desirably performed in an anaerobic state, ozone is dissolved after the denitrification treatment.

  On the other hand, in the case of treating waste water that has a small amount of nitrogen and does not require much denitrification, denitrification can be performed after ozone is dissolved. In the wastewater treatment apparatus of the present invention, the ozone treatment apparatus can be provided in the front stage of the denitrification tank. As a result, first, the amount of BOD, COD, and SS of the waste water is reduced by ozone treatment, and then denitrification is performed.

  At this time, since the water after denitrification is in an anaerobic state, it is desirable to circulate the water after denitrification to dissolve oxygen. In the waste water treatment apparatus of the present invention, it is desirable to provide an oxygen treatment apparatus that circulates water in the latter tank of the denitrification tank and dissolves oxygen. Thereby, efficient oxygen supply can be performed in biochemical treatment.

  Moreover, it is desirable that the ozone treatment apparatus according to the present invention includes a refining means for refining solid matter in water. Thereby, since the solid substance in water is refined | miniaturized and the contact area with ozone is expanded, the BOD, COD, and SS amount of waste water can be reduced further.

(1) After the water before biochemical treatment is circulated to dissolve ozone, the biochemical treatment is applied to reduce the burden on the microorganisms that perform biological treatment of wastewater, and biological treatment It is possible to reduce the amount of sludge generated by the process. Further, since the amount of microorganisms necessary for biological treatment of waste water is reduced, the tank capacity of the biological treatment tank can be reduced, and the equipment can be downsized. Furthermore, since the amount of oxygen supplied to the microorganism can be reduced, the energy required for supplying oxygen can be reduced, and the running cost can be reduced.

(2) The configuration in which denitrification is performed before ozone is dissolved makes it possible to efficiently perform denitrification while ensuring the BOD necessary for treating wastewater that requires denitrification. It is possible to dissolve ozone after the treatment to reduce the amount of BOD, COD, SS, and to reduce the amount of sludge generated by biological treatment itself.

(3) Oxygen is supplied to water in an anaerobic state after denitrification by denitrification after ozone is dissolved and oxygen is dissolved by circulating the water after denitrification, and efficiently. Biological treatment can be performed.

(4) The ozone treatment device is equipped with a means to refine solids in water, further reducing the amount of BOD, COD, and SS, and reducing the amount of sludge generated by biological treatment. It becomes possible to do.

FIG. 1 is a schematic configuration diagram of a wastewater treatment apparatus according to an embodiment of the present invention.
In FIG. 1, the waste water treatment apparatus in the embodiment of the present invention includes an adjustment tank 1 that introduces raw waste water and adjusts the concentration and inflow amount, a denitrification tank 2 that removes nitrogen in the waste water, A biological treatment tank 3 comprising a first aeration tank 3a, a second aeration tank 3b, a third aeration tank 3c, and a fourth aeration tank 3d for performing biological treatment, and water and sludge after biological treatment are separated. A settling tank 4, a disinfection tank 5 for disinfecting water separated by the settling tank 4, and a press device 6 for pressing sludge separated by the settling tank 4.

  Further, this waste water treatment apparatus has an oxidation tank 7 at the front stage of the first aeration tank 3 a and at the rear stage of the denitrification tank 2. The oxidation tank 7 is provided with an ozone treatment device 8 that circulates water in the oxidation tank 7 and dissolves ozone. The ozone treatment device 8 sucks water in the oxidation tank 7, oxidizes it by dissolving ozone in the sucked water, and returns it to the oxidation tank 7. The blower 9 shown in FIG. 1 is for supplying air for aeration to the aeration tanks 3 a to 3 d of the biological treatment tank 3.

  In the wastewater treatment apparatus configured as described above, the raw water of the wastewater introduced into the adjustment tank 1 is first adjusted in concentration, inflow, etc. in the adjustment tank 1, and denitrified in the denitrification tank 2. Thereafter, ozone treatment is cyclically performed in the oxidation tank 7 by the ozone treatment device 8, and the amount of BOD, COD, and SS is reduced. Since ozone dissolved by the ozone treatment apparatus 8 is an unstable substance and is changed to oxygen immediately after the reaction, the water treated by the ozone treatment apparatus 8 is used for biological treatment in the biological treatment tank 3. It contains a large amount of necessary oxygen.

  In the biological treatment tank 3, the first aeration tank 3a, the second aeration tank 3b, the third aeration tank 3c, and the fourth aeration tank 3d are sequentially subjected to the aeration process. In these aeration tanks 3a to 3d, the amount of BOD, COD, and SS of the waste water is reduced in the preceding stage, so that the capacity thereof may be small and the amount of microorganisms may be small.

  Although the water after biological treatment is sent to the sedimentation tank 4, since this water contains a lot of oxygen, flocs (aggregates) are easy to grow and have good sedimentation properties. The supernatant of the sedimentation tank 4 is sterilized in the sterilization tank 5, adjusted for pH, and then discharged. Part of the sludge accumulated below the settling tank 4 is returned to the denitrification tank 2, the oxidation tank 7, or the first aeration tank 3a and reprocessed. A part of it is pressed by the press device 6 and discharged out of the waste water treatment device.

  In the wastewater treatment apparatus in this embodiment, the biochemical treatment is performed after circulating the water before biochemical treatment to dissolve ozone, thereby reducing the load on the microorganisms that perform the biological treatment of wastewater. The amount of sludge generated by biological treatment can be reduced. Moreover, the amount of flocculant used when the sludge is pressed is reduced by reducing the amount of sludge generated.

  Further, since the amount of microorganisms necessary for biological treatment of waste water is reduced, the capacity of the biological treatment tank can be reduced, and the equipment can be downsized. Furthermore, since the amount of oxygen supplied to the microorganism can be reduced, the energy required for supplying oxygen can be reduced, and the running cost can be reduced. In addition, as a result of experiments conducted by the inventor using the testing machine, the amount of electricity used for biological treatment is ½, the amount of sludge is reduced by 50 to 70%, the amount of chemical used is ½, and the equipment space Was 1/2 and the running cost was 1/2 or less.

  Further, in the wastewater treatment apparatus of FIG. 1, ozone is dissolved in the water after denitrification, so BOD necessary for denitrification is included in the wastewater. Thereby, when there is much nitrogen amount in waste_water | drain, after performing a denitrification process in the denitrification tank 2, BOD can be reduced by ozone treatment and a biological process can be performed. On the other hand, when the amount of nitrogen is small and denitrification is not necessary, the configuration shown in FIG. 2 can be adopted.

FIG. 2 is a schematic configuration diagram of a waste water treatment apparatus showing another embodiment of the present invention.
The wastewater treatment apparatus shown in FIG. 2 has substantially the same configuration as that shown in FIG. 1, but the ozone treatment apparatus 8 is provided in the adjustment tank 1 in the preceding stage of the denitrification tank 2 and the water in the adjustment tank 1 is circulated. Thus, the difference is that ozone is dissolved, and the oxygen treatment apparatus 10 is provided in the first aeration tank 3a, and water is circulated in the first aeration tank 3a to dissolve oxygen.

  In such a configuration, first, the amount of BOD, COD, and SS of the waste water is reduced by ozone treatment, and then denitrification is performed. Although the water after the denitrification treatment is in an anaerobic state, the oxygen treatment apparatus 10 provided in the first aeration tank 3a in the subsequent stage circulates the water after the denitrification to dissolve the oxygen. It is possible to supply a good oxygen.

  In the denitrification tank 2, it is desirable to manage the oxidation-reduction potential (ORP) with -300 mV as a guide. Denitrification must be performed in an anaerobic state, and if ORP is negative, it is in a reduced state, that is, an anaerobic state. By managing the ORP with −300 mV as a guide, the denitrification tank 2 can be maintained in an anaerobic state, and denitrification can be performed efficiently. If ORP is positive, it is in an oxidized state, that is, an aerobic state.

Next, details of the ozone treatment apparatus 8 will be described.
The ozone treatment device 8 is a device that injects ozone gas into the inhaled waste water and reacts the waste water and the ozone gas. The inside of the ozone treatment apparatus 8 is pressurized to about 0.15 to 0.3 MPa. The ozone treatment apparatus 8 includes a nozzle 30 shown in FIG. 3 as a finer means for refining solid matter such as SS (floating matter) in the wastewater to be introduced. 3A is a front view of the nozzle 30, FIG. 3B is a longitudinal sectional view, and FIG.

  As shown in FIG. 3B, the nozzle 30 has an inner / outer double structure including an inner nozzle 31 and an outer shell 32. Waste water is discharged from the inner nozzle 31 into the ozone treatment device 8. As shown in FIGS. 3B and 3C, the tip of the inner nozzle 31 opens downward. The opening 33 of the inner nozzle 31 is provided with a plurality of claws 34 a and 34 b that protrude alternately inside and outside the inner nozzle 31. The drainage discharged from the inner nozzle 31 is refined by colliding with the inner claw 34a. A part of the waste water discharged from the inner nozzle 31 is refined by colliding with the outer claw 34b when diffusing outward from the inner nozzle 31.

  The outer shell 32 includes a plurality of slits 35 as shown in FIG. The slit 35 has a shape in which irregularities are alternately arranged like a saw tooth. The solid matter in the waste water discharged from the inner nozzle 31 is further refined by colliding with irregularities such as saw teeth when passing through the slit 35. Further, a scattering plate 36 is provided below the outer shell 32 and directly below the inner nozzle 31 for colliding and discharging the water discharged from the inner nozzle 31.

  The peripheral edge of the scattering plate 36 has a shape that is slightly warped upward so as to go to the slit 35 of the outer shell 32 after the drainage discharged from the inner nozzle 31 collides. The solid matter in the waste water discharged from the inner nozzle 31 collides with the scattering plate 36 and is scattered and further refined by passing through the slit 35.

  In the ozone treatment device 8, the solid matter in the wastewater is oxidatively decomposed by ozone gas. Since the solid matter in the wastewater is refined by the nozzle 30 as described above, the solid matter in the wastewater and the ozone gas Is more actively performed, and the oxidative decomposition of organic matter is further promoted. Here, since ozone is a very unstable substance, there are a substance that reacts directly with an organic substance and decomposes into oxygen, and a substance that self-decomposes in water, as shown below.

(1) Direct reaction O ₃ + M (organic) → MO + O ₂
(2) Self-decomposition O ₃ + H ₂ O → HO ₃ + OH ^{−
_{HO 3 + + OH - → 2HO}} 2 ·
O ₃ + HO ₂ · → OH · + 2O ₂

As shown in (2), ozone decomposes with water (hydrolysis) to form hydroperoxy radicals (HO _2. ), And further reacts with ozone to generate OH radicals (OH.). That is, OH radicals having very strong oxidizing power are generated in the waste water in the ozone treatment apparatus 8. Therefore, organic substances in the wastewater are oxidatively decomposed by the OH radicals.

  Since the ozone treatment apparatus 8 includes the nozzle 30 as described above, the solid matter in the waste water is refined and the contact area with ozone is expanded, so that the reaction with ozone is further promoted. Therefore, the amount of BOD, COD, and SS of waste water can be reduced more efficiently. Further, since the inside of the ozone treatment apparatus 8 is pressurized, more ozone gas or the like is dissolved in the waste water, reacts with the organic matter in the waste water, and the organic matter is oxidatively decomposed.

  The wastewater treatment method and apparatus of the present invention are useful as a method and apparatus for biologically treating wastewater such as sewage, human waste, factory wastewater and domestic wastewater. In particular, the wastewater treatment method and apparatus of the present invention are suitable as a compact and energy-saving wastewater treatment method and apparatus because the amount of sludge generated by biological treatment itself can be reduced.

It is a schematic block diagram of the waste water treatment equipment in embodiment of this invention. It is a schematic block diagram of the waste water treatment equipment which shows another embodiment of this invention. (A) is a front view of a nozzle, (b) is a longitudinal cross-sectional view, and (c) is a view on arrow A.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Adjustment tank 2 Denitrification tank 3 Biological treatment tank 3a 1st aeration tank 3b 2nd aeration tank 3c 3rd aeration tank 3d 4th aeration tank 4 Settling tank 5 Disinfection tank 6 Press apparatus 7 Oxidation tank 8 Ozone treatment apparatus 9 Blower DESCRIPTION OF SYMBOLS 10 Oxygen processing apparatus 30 Nozzle 31 Inner nozzle 32 Outer part 33 Opening part 34a, 34b Claw 35 Slit 36 Scatter plate 37 Water level sensor

Claims (10)

  A wastewater treatment method for biochemically treating wastewater, wherein the biochemical treatment is performed after ozone is dissolved by circulating water before the biochemical treatment.   The wastewater treatment method according to claim 1, wherein denitrification is performed before the ozone is dissolved.   The wastewater treatment method according to claim 1, wherein denitrification is performed after the ozone is dissolved.   The wastewater treatment method according to claim 3, wherein the water after the denitrification is circulated to dissolve oxygen.   A wastewater treatment apparatus for treating wastewater with a biochemical treatment tank, comprising an ozone treatment apparatus that circulates water in a preceding tank of the biological treatment tank and dissolves ozone.   The wastewater treatment apparatus according to claim 5, wherein the ozone treatment apparatus is provided in a subsequent stage of the denitrification tank.   The wastewater treatment apparatus according to claim 5, wherein the ozone treatment apparatus is provided in a front stage of a denitrification tank.   The wastewater treatment apparatus according to claim 7, further comprising an oxygen treatment apparatus that circulates water in a subsequent tank of the denitrification tank and dissolves oxygen.   The wastewater treatment apparatus according to claim 8, wherein the oxygen treatment apparatus circulates water in the first tank of the biological treatment tank to dissolve the oxygen.   The wastewater treatment apparatus according to any one of claims 5 to 9, wherein the ozone treatment apparatus includes a refining means for refining the solid matter in the water.

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