JPH0314520B2 - - Google Patents

Description

Claim 1 (a) A plurality of propeller-type air aeration devices each having a hollow tube having opposite ends, a longitudinal axis extending between the ends, and a propeller proximate one end of the ends. (b) locating the propeller and the tube end adjacent thereto below the upper surface of the water, and directing the longitudinal axis of each aeration device from the horizontal; (c) installing a plurality of air atomizers to form individual circulating flow patterns around each atomizer; (d) a plurality of air atomizers in a position to link together individual flow patterns formed by adjacent air atomizers to form a larger closed flow pattern as a whole; (e) injecting oxygen through a tube into the water in an area proximate to the propeller at a rate of not less than 1 pound per horsepower; (f) disposing the plurality of inducing a flow of at least 0.25 feet per second in a general flow pattern within the enclosed area in a horizontal direction across the cross section at an average linear velocity by rotating a plurality of propellers of the air aeration device; A method of treating water surrounded by a boundary by a propeller-type aeration device comprising: 2. Step (e) above includes injecting oxygen at a rate of 2.0 pounds per horsepower or more;
2. The method of claim 1, wherein (f) includes the step of inducing a general flow path within said closed region at a linear velocity of greater than 0.5 feet per second. 3. Step (f) comprises driving the propellers of the plurality of aeration devices underwater in the defined area at less than 0.5 horsepower per 1000 ft ³ of water in the closed area. 3. A method as claimed in claim 1 or claim 2, comprising inducing a general flow pattern within. 4. Step (f) comprises driving the propellers of the plurality of aeration devices underwater in the defined area at less than 0.1 horsepower per 1000 ft ³ of water in the closed area. 4. A method according to claim 3, comprising inducing a general flow pattern within. 5. The method of claim 1 or claim 2, wherein step (f) comprises maintaining the linear velocity in water within the area to a depth of at least 10 feet. 6 In step (b), the longitudinal axis is aligned with the horizontal line.
Claim 1 includes installing each air atomization device at an angle of 12 degrees and 25 degrees.
or the method described in paragraph 2. 7. The method of claim 6, wherein said angle is set at approximately 22 degrees with respect to the horizon. 8. The method of claim 1, wherein step (d) comprises arranging the plurality of air aeration devices to form a plurality of generally larger closed flow patterns. 9 (a) a hollow tube each having opposite ends, a longitudinal axis extending between the ends, and a propeller adjacent to one end of the ends, the one end of the tube adjacent to the propeller; (b) aerating a defined area of water by means of a plurality of propeller-type driven rotary aeration devices including means for injecting air into the water; arranged below the upper surface and with the longitudinal axis of each aeration device at an angle below the horizontal plane;
placing each air atomizer in a fixed area of water; (c) a forward horizontal flow vector directed in the forward direction of the propeller of the first air atomizer; inducing a first fluid flow path around the first air aeration device having an opposite horizontal flow vector toward a propeller of the device and a diffuse horizontal flow field connecting the forward and reverse flow vectors; (d) directing a forward horizontal flow vector in the direction of forward movement of a propeller of a second air atomization device; a second fluid flow path having a horizontal flow vector directed in a direction opposite to the direction toward the propeller of the air aeration device and a diffuse horizontal flow field leading to flow vectors in the forward and reverse directions of the second fluid flow path; (e) arranging and driving the second air blowing device to induce about the second air blowing device; (e) at least some reverse flow vectors through the second air blowing device; the second air blowing device in combination with at least some forward flow vectors through the first air blowing device to form an entire flow path generally in the direction of the forward flow vectors through the first and second air blowing devices. (f) introducing oxygen into the boundary water through the plurality of tubes of the plurality of aeration devices at a rate of not less than 1 pound per horsepower; (g) inducing a plurality of propellers of the plurality of aeration devices to cause water to flow through the cross section at an overall path average velocity of at least 0.25 feet per second. A method of treating water enclosed by a boundary by type aeration equipment. 10. Step (f) comprises injecting oxygen at a rate of 2.5 pounds per horsepower or more, and step (c) further comprises inducing a general flow path of the water at a linear velocity of 0.5 feet per second or more. , the method according to claim 9. 11 inducing the overall flow path of water by driving a plurality of propellers of the plurality of aeration devices in the fixed area of water with less than 0.5 horsepower per ¹⁰⁰⁰ ft of water in the fixed area of water; , claim 1
The method described in item 0. 12 (h) a forward horizontal flow vector directed in the forward direction of the propeller of the associated air atomization device, and a horizontal flow vector directed from the region behind the propeller in a direction opposite to the direction toward the propeller of the associated air atomization device; additionally arranging and driving a series of aeration devices to induce around each aeration device each said fluid flow path having a diffuse horizontal flow field leading to forward and reverse flow vectors; and (i) forming a generally closed flow path by combining several backward flow vectors and forward flow vectors from a plurality of air aeration devices arranged in series. 10. The method of claim 9, including the step of arranging a series of additional pneumatic devices and said first and second plurality of pneumatic devices. 13 (j) installing at least a second set of a plurality of propeller-type aeration devices; and (k) a second set of a plurality of propeller-type aeration devices adjacent to the first generally closed flow path; a plurality of steps (a), (b), (c),
13. The method of claim 12, comprising the steps of (d), (e), (h) and (i). 14 (l) installing another set of propeller-type aeration devices; and (m) installing an additional set of propeller-type aeration devices such that the overall performing multiple steps (a), (b), (c), (d), (e), (h), and (i) to form a general flow path within an additional closed region within the flow path; 13. The method of claim 12, comprising the steps of: 15 (n) at least one of the additional plurality of air venting devices is connected to another closed area to prevent the formation of a flow area with no flow in the center of the overall flow path within the additional closed area. 15. The method of claim 14, including the step of locating the additional closed region out of alignment with the general flow path within the additional closed area toward the center of the general flow path to form a wake flow path. 16 (o) at least one pneumatic device in the series of pneumatic pneumatic devices is installed within the closed region to avoid the formation of a flow zone with no flow in the center of the overall flow path within the closed region. 13. The method of claim 12, including the step of locating out of alignment with the general flow path and toward the center of the general flow path within the closed region to form a wake path. TECHNICAL FIELD This invention relates generally to water treatment by aeration. Water aeration has been used to treat wastewater in oxidation ponds and to improve the quality of natural waters such as lake water. BACKGROUND OF THE INVENTION In most conventional design criteria evaluations for popular oxidation ponds, nearly all of the efforts have been focused on meeting the biochemical oxygen demand (BOD) of the wastewater. In other words, the amount of air or oxygen that should be supplied to the oxidation pond is:
Pollution was calculated by the amount of excess oxygen available from photosynthesis and air aeration. Until recently, agitation of sewage to keep solids in suspension in the presence of water surrounded by a fixed area has been neglected. WATER AND SEWAGE PLANT
Sam C. on pages 82-83 of SEWAGE WORKS).
White and Linvil G. Rich, in a paper entitled ``1977 Wastewater Standards - How to Plan an Exposed Oxidation Pond System to Meet the Removal of Soluble Substrate Relationships,'' included as a parameter. Sewage treatment aeration systems typically utilize either diffused air aeration devices or mechanical aeration devices. Diffused air type aeration devices introduce air or pure oxygen into the water via a forced diffuser submerged in the water. Mechanical type aeration devices agitate the water to promote the dissolution of air from the atmosphere into the water. These conventional aeration devices are primarily designed with a view to introducing a certain amount of oxygen into the water being treated. Since water agitation and oxygen introduction were not part of the planning standard, typical conventional aeration equipment systems do not have sufficient agitation capacity. For example, in a one-acre aeration pond for treating sewage from livestock, etc., which has a depth of 10 feet, a 3:1 sidewall slope, and a volume of 432,000 ft ³ , the conventional method for making an aeration system is requires a surface area capacity of approximately 200 to 400 horsepower or more than 1000 horsepower for the diffused air system. Such a powerful system will provide four times the oxygen demand that the pond can meet, but will likely not cause complete agitation of the pond because it ensures a flush rate of 0.5 feet per second throughout the pond. Mechanical surface aeration devices also have a further problem in that they have separate and usually colliding mixing vectors. That is, the force vectors from the air blowers are generally not controllable or manipulable, and therefore with multiple closely spaced air blowers, the mixing vector tends to disappear. Another problem with most conventional aeration equipment systems is that their oxygen transfer is actually limited by the inability to adequately agitate the wastewater. Most conventional aeration equipment systems tend to affect only a very limited core area, i.e., because of the inability of the equipment for agitation, the equipment itself causing high dissolved oxygen concentrations in the vicinity of Therefore, such conventional systems create conditions of oxygen supersaturation instead of being under saturation, which promotes oxygen transfer. Many conventional air aeration devices are tested in small tanks and the measured oxygen transfer rates for the tests at zero dissolved oxygen are reported as a basis for comparison. However, this criterion is not accurate in the field of application. This is because dissolved oxygen is required in higher amounts in the field of application. In the field of installation, conventional devices tend to overwhelm the immediate area and thereby tend to operate effectively against themselves. Dissolved oxygen does not effectively reach remote areas. Other problems have also arisen due to the failure of prior art aeration systems to properly mix the wastewater being treated. In the absence of proper mixing, for example if a horizontal velocity of 0.5 fps is not achieved, an exposed oxidation pond will suffer from the disadvantages of hydraulic short circuiting and/or the formation of sludge-like solids. When sewage is introduced into an unstirred oxidation pond, a certain proportion of the sewage goes directly to the outlet without sufficient time to interact with other oxidation pond contents for adequate treatment. do. If the pond is completely stagnant, inlet velocity effects or moments cause such "short-circuiting" flow, and this problem is exacerbated by thermal stratification effects. Under agitation in the oxidation pond, the cell is aerobically similar to any pond.
Develops into anaerobic region. Anaerobic sludge deposits found in unstirred oxidation ponds are
Produces noxious odors such as H ₂ S and/or NH ₃ gas. These gases result in high concentrations of oxidizing organic matter (i.e., BOD) in the water. lastly,
The generation of these gases with CH ₄ and N ₂ contributes to the suspension of solids and their tendency to blow out to the oxidation pond or cell outlet. This mass of material is conveyed to a continuous processing chamber or discharged as a final effluent. Sludge deposits deposited in the oxidation pond must be considered uncontrolled. Anaerobic digestion occurs when temperatures permit, resulting in cyclical operations. If the effluent suspended solids at BOD concentration becomes a function of such factors, the system cannot effectively control its operation. Such systems cannot reliably guarantee the degree of effort required to meet the performance standards issued today. The method of the present invention overcomes the above-mentioned drawbacks of conventional systems both by aerating the water and by agitating the aerated water at an effective power level. BRIEF SUMMARY OF THE INVENTION The present invention relates to a method for treating water. The method includes the following steps: a plurality of propeller-shaped air bubbles each having a hollow tube having opposite ends, a longitudinal axis extending between the ends, and a propeller proximate one end of the ends; aerating water within a defined area by means of an air atomizer equipped with an air atomizer; disposing the propeller and the tube end adjacent thereto below the upper surface of the water; placing each atomization device in a defined area of water, oriented downwardly at an angle; and placing a plurality of aeration devices to form individual circulating flow patterns around each atomization device; driving the plurality of air atomization devices such that individual flow patterns formed by adjacent aeration devices combine with each other to form an overall flow pattern within a larger enclosed area; agitating the water in an array; injecting oxygen through a tube into the water in an area proximate the propeller at a rate of 1 pound per horsepower or more; inducing a general flow pattern within the closed region in a horizontal direction across a cross section at an average linear velocity of at least 0.25 feet per second by rotating a propeller. In a preferred embodiment, the method includes the step of injecting oxygen at a rate of 2.0 pounds or more of oxygen per horsepower per hour;
Multiple steps of inducing a general flow pattern within a constant area at a linear velocity of 0.5 feet per second or more by driving the propellers of multiple aeration devices underwater within a closed area with less than 0.1 horsepower per ¹⁰⁰⁰ ft3 Contains. Induction of oxygen injection and flow patterns at the low horsepower rates described above results in efficient treatment of wastewater and an effective reduction in biological oxygen demand (BOD) of the effluent. Efficient treatment of wastewater is
It is believed that it depends on the ability of both to induce a flow pattern and to inject oxygen to maintain the solids in suspension at the rated effective power. The overall flow pattern in the water within a fixed area is achieved by combining together multiple circulating flow patterns from multiple adjacent aeration devices.
In one embodiment, a single series of a plurality of aeration devices or a set of a plurality of aeration devices are arranged in a general flow path within a single closed area. In other embodiments, a second set of a plurality of aeration devices is arranged in close proximity to the first set to form a second closed flow pattern within the area of water. In other embodiments, a second set of pneumatic devices forms a closed flow pattern within the closed region flow pattern formed by the first set of pneumatic devices. One or more air aeration devices may be arranged from the overall flow pattern toward the center of the overall flow pattern to prevent areas of no flow within the center of the overall flow pattern. This arrangement of one or more air aeration devices creates a wake pattern to avoid dead-flow areas. By injecting oxygen at a controlled rate and simultaneously controlling wastewater flow and flow patterns, a controlled and efficient wastewater treatment system can be maintained. The suspended solids are equalized in the various oxidation ponds and the effluent is operated by a series of systems with suitably controlled agitation of the oxidation ponds. Appropriate solids can provide seasonally controlled emissions while keeping the liquids in flow.
Because this strategy is carried out by aeration devices and turbulence (agitation), aeration becomes less and less during the winter months as the temperature decreases. This is valid. Less oxygen is required because the rate of oxygen demand declines with temperature and oxygen transfer efficiency improves as the dissolved oxygen saturation value increases. Another advantage of this process is that the solids are preferentially settled out of suspension and the oxidation pond essentially provides storage and retention of the solids during winter operations. The solids then accumulate as a blanket of thin aerobic sludge for slow digestion during the winter. As mentioned above, the level of aeration decreases during the winter, when the surface of the oxidation pond must be at least partially open to the atmosphere, or at least aerobic conditions must prevail throughout the water volume. . Sludge layers kept under aerobic conditions for long periods of time can be expected to undergo decomposition and be discarded. When rainwater inflow occurs and the flow level increases and the oxidation pond forms again, the degree of aeration and turbulence conditions resuspends the solids, providing for a discharge of solids proportional to the flow. and reinstated early and gradually to increase processing. Thus, by using the present invention, a system capable of controlling wastewater treatment all year round can be achieved at effective power levels. The features of novelty and various advantages which characterize the invention are pointed out in and form a part of the appended claims. However, the present invention
For an even better understanding of the advantages of the invention and what may be obtained by its use, preferred embodiments of the invention are illustrated and described above, and the accompanying drawings and accompanying drawings form a part of the invention. Description should be referred to.

[Brief explanation of the drawing]

FIG. 1 is a side view of a single propeller type air aeration device used in the method of the invention;
Figure 2a is a plan view schematically showing the particular arrangement of a number of propeller-type aeration devices in water bounded by a boundary and the overall flow path induced by the multiple aeration devices; Figure 2b is a plan view similar to Figure 2a showing a plurality of propeller-type air aeration devices in water surrounded by different boundaries; Figure 3a is a plan view similar to Figure 2a; Figure 3b is a diagram showing the velocities measured at various locations in the water bounded by the boundary shown in Figure 2b; FIG. 4 is a diagram showing the velocity measured at the position;
FIG. 5 is a plan view schematically illustrating individual horizontal circulating flow patterns induced by a plurality of propeller-type air aeration devices and the combination of adjacent circulating flow patterns according to the method of the present invention;
FIG. 6 is a plan view schematically showing another arrangement of multiple propeller type air aeration devices and the resulting close overall flow path; FIG. FIG. 2 is a schematic plan view showing an arrangement of a plurality of propeller-type air ablation devices in the circulating general path formed by placing the air ablation devices offset from the general flow path; FIG. 7 shows a plurality of propellers in a single global flow path in which a number of air blowing devices are placed off-set from the global flow path to form a wake flow path; FIG. 2 is a plan view schematically showing the arrangement of a type of air aeration device.

[Detailed description of the invention]

With reference to the drawings, a propeller-type aeration device used in the method of the invention is illustrated in FIG. The aeration device 10 is shown placed in a liquid 12, preferably water or waste water. Air exposure device 10
includes an outer tubular housing 14 and an inner tube 16 rotatably disposed within the outer tubular housing 14.
has. Inner tube 16 extends within tubular housing 14 to a position above the uppermost surface of liquid 12 and is operatively connected to a motor located within motor housing 18 . inner tube 16
In order to introduce air into the interior of the tube 16, the liquid 1
The upper end of the tube has at least one hole above the highest point of the tube. An inner tube 16 extends outwardly below the lower end of the tubular housing 14 and has a propeller 2 fixedly attached thereto.
has 0. Diffusion tube 22 is also attached to inner tube 16 and has an inner cavity that communicates with the inner cavity of inner tube 16 . When inner tube 16 is rotated by the motor, propeller 20 also rotates. propeller 20
As it rotates, the propeller creates a directional, turbulent flow field within the liquid 12. The reduced pressure zone caused by this downward flow of the propeller draws or pulls air down the hollow tube 16 and introduces the air as bubbles 24 into the liquid through the open end of the diffusion tube 22. . The bubbles 24 are then dispersed by the turbulence caused by the propeller. In this manner, the propeller aeration device atomizes while stirring. As will be described in more detail below, the aeration device 10 is arranged to provide a unidirectional flow with the aeration device 10 attached to additionally contribute to a uniform mixing pattern involving water within the entire defined area. be able to. The liquid flow can therefore be directed and circulation formation developed to ensure a favorable velocity vector within the total volume of water to be treated. Inner tube 16 has a longitudinal axis indicated by line 26. The pneumatic device 10 is supported within the liquid 12 by a platform or boom 28. The air blower 10 is mounted to the platform 28 in a conventional manner, such as by a bracket 30. The air aeration device has a longitudinal axis 2
6 is supported in liquid 12 so as to form an angle between 15 and 25 degrees with the horizontal plane. Preferably the angle is set to 22 degrees. In this manner, agitation energy caused by rotating the propeller promotes circulation and flow over a larger area than is typical of conventional turbine aeration equipment. If the angle is increased beyond 25 degrees, the tube 14 becomes more vertical and some higher oxygen transfer is obtained at the expense of agitation.
When the angle is reduced to less than 15 degrees with respect to the horizontal plane,
Agitation is increased at the expense of oxygen transfer. Regarding the tilt angle, a range of 15 to 25 degrees is the optimal compromise range for mixing and aeration;
It has been found that a tilt angle of 22 degrees is preferred. The method of the present invention is primarily employed in aeration oxidation ponds or ponds used as part of a general wastewater treatment process. A vented oxidation pond system can be designed for three different degrees of agitation. The degree of agitation is generally determined by the degree of contamination in the water or the required BOD. For most sewage treatment ponds where relatively dilute livestock waste is introduced, the power required to meet oxygen demands most of the year is limited to keeping the solids in suspension. significantly smaller than that required.
Even at the lowest input, sufficient oxygen must be delivered to satisfy the BOD in the wastewater. Delivery of 0.7 to 1.4 pounds of oxygen per pond is typical. Moderate inputs must be provided for a uniform distribution of oxygen within the oxidation pond in addition to simply supplying a certain amount of oxygen.
Therefore, additional power is required over and above that required to simply introduce oxygen so that minimal circulation effects are achieved and uniform distribution of oxygen is ensured throughout the oxidation pond. However, at such medium levels, sufficient turbulence may not keep solids in suspension. The highest level of input reasonably required will provide a minimum oxygen dispersion and flow rate such as 0.4 to 0.5 feet per second (fps). Prior art aeration systems achieve such flow rates by:
Requires at least 0.5hp/1000 ³ of water and high power output. The method of the present invention accomplishes both the introduction of an adequate amount of oxygen into the wastewater and the agitation of the aerated wastewater at an effective power level. The present invention allows oxygen introduction and agitation speed to be adjusted or controlled at effective power levels under a variety of water contamination conditions. The method of the invention comprises the step of providing a plurality of propeller-type air atomizers, each air atomizer having a hollow tube at opposite ends and extending within the ends. It has a propeller adjacent the longitudinal axis and one of the ends. Air exposure device 10 is particularly preferred for the method of the invention. A plurality of aeration devices are provided with a propeller and a tube end adjacent to the propeller below the highest surface of the water and a longitudinal axis of each aeration device disposed at an angle below the horizontal plane. Mounted underwater surrounded by a boundary such as an oxidation pond. The water is distributed through the aeration devices such that individual circulating flow patterns are formed around each aeration device and the individual flow patterns combine with each other to form an overall flow pattern within a larger enclosed area. is stirred by arranging and driving. That is, air atomization devices are designed such that when the device's propeller is driven at a high enough velocity to inject ambient air into the water, individual flow patterns are formed around each atomization device and within a larger enclosed area. so arranged that they combine together to form an overall flow pattern in the flow pattern. The state of individual flow patterns and combinations of adjacent individual flow patterns is illustrated in FIG.
A plurality of air aeration devices 10a, 10b, 10c are the fourth
Diagrammatically illustrated in the figure. A plurality of horizontal flow vectors indicating the horizontal flow of water are connected to each air atomization device 1.
It shows that it is flowing around 0a, 10b and 10c. Multiple forward horizontal flow vectors 3
2 shows the horizontal flow of fluid in front of the propeller of the air blower 10a. The counter-directional horizontal flow of the plurality of vectors 34 represents a horizontal flow of fluid drawn toward the propeller of the operator 10 from the area behind the propeller. Horizontal flow vector 36 is a horizontal flow vector 36 of the fluid that curves backward from the forward flow represented by vectors 32 and is interconnected with or forms part of the flow represented by vector 34 in the opposite direction. Shows directional diffusive flow. As seen in FIG. 4, a plurality of air blowing devices 10
a, 10b and 10c indicate that at least some of the flows indicated by the reverse direction flow vectors 34 of one of the plurality of air blowing devices are at least some of the plurality of forward flow vectors 32 due to adjacent air blowing devices. are arranged with each other so that they are connected to the vector of In this manner, a generally horizontal flow is created in the general direction of the forward flow vector 32. Figures 2a and 2b show a plurality of propeller-type air aeration devices supported on a plurality of platforms or balloons in a pair of water treatment oxidation ponds in which the present invention was studied. Flow vectors or arrows 40, 38 indicate the overall horizontal flow pattern or flow path within the closed area of wastewater. The outer set or outer circle of the plurality of air venting devices 10 forms the overall flow pattern indicated by vector 38. The overall flow pattern indicated by vector 40 is formed by the inner set or inner circle formed by air venting device 10. The overall flow pattern represented by vectors 40 cycles within the overall flow pattern shown by vectors 38. Figures 2a and 2b schematically represent plan views of two oxidation ponds or ponds forming part of a wastewater treatment plant in which the method of the invention is utilized. The water treatment plant also includes a primary settling device, a roughing filter and then a clarification body with a pond or oxidation pond having four ponds, and the second a and second b of the four ponds are respectively The first and second multiple ponds of the system are illustrated respectively. These first two ponds have a surface area of about 3/4 of an acre and a water capacity of about 275,000 ft ³ . The ponds are approximately 175 feet wide and 190 feet long. The pond shown in Figure 2a has a plurality of aeration devices 10 installed with a total power of 36 hp. The pond shown by Figure 2b has a plurality of air aeration devices 10 installed with a combined power of 20 hp. Booms 28 extend inwardly from about the center of each side of each pond. Each outer pneumatic device is located approximately 30 feet from its respective side wall and each inner pneumatic device is located approximately 60 feet from its respective side wall. Figure 3a is a longitudinal section of the pond shown in Figure 2a along the 195 foot length line passing between SE and NW. FIG. 3b is a similar longitudinal section along a 195 foot length line from SW to NE within the pond shown in FIG. 2b. 3rd a
Figures 3b and 3b show that the air aeration device 10 is
in feet per second (fps) measured at various depths in multiple ponds along the cross-section while operating to form the overall flow pattern shown by 8,40. Represents a measured value of the expressed velocity. The velocity measured in Figure 3a is an average horizontal linear velocity of 0.77 fps across the first pond cross-section, and the velocity measured in Figure 3b is a global average linear velocity of 0.77 fps across the second pond cross-section. The average linear velocity in this direction is 0.58fps. These measured average velocities of the ponds are also the average velocities of the overall flow pattern within a closed area within the ponds. A total of 36 hp is used in the first pond, and the first pond has a volume of about 275,000 ft ³ and water
Average speed of the pond using 0.13hp per ^1000ft3
Get 0.77fps. The second pond also has a volume of approximately 275,000 ft ³ and uses 0.07 hp per 1000 ft ³ of water to obtain an average speed of 0.58 fps for the second pond. The 20 hp used in the second pond was sufficient speed to keep the solids in complete suspension. Using a 5-horsepower propeller-type atomizer and positioning the atomizer approximately 22 degrees below horizontal, sufficient horizontal flow to maintain solids in suspension will occur at least 60 feet in front of the atomizer. A spreading and dispersing flow field is formed approximately 60 feet wide. When using a 2-horsepower propeller-type air atomizer and positioned at an angle of less than about 22 degrees below the horizontal, the horizontal forward flow field sufficient to maintain solids in suspension is about 30 to 40 degrees. It has a width of a foot. It is generally accepted that an average velocity of 0.50 fps is sufficient to keep solids in suspension within wastewater treatment capacity. Increase accumulated in pond system
Because of the BOD, the high power used in the first pond is used. As mentioned above, the average pond velocity achieved in the pond as shown in Figures 2a and 2b kept all solids in suspension. It is also within the concept of the present invention to use such low flow rates that the solids can only be partially suspended. but,
The present invention contemplates an average pond velocity of 0.25 fps or greater for mixing wastewater. In a preferred embodiment, a pond average velocity of 0.5 fps or greater is used.
An average pond velocity of 0.5 fps or higher is sufficient to maintain solids in complete suspension. In the pond illustrated by Figures 2a and 2b, oxygen was injected at a rate of over 2.0 pounds of oxygen per horsepower. The method of the present invention contemplates injecting oxygen at a rate of at least 1 pound of oxygen per horsepower and preferably at least 2 pounds of oxygen per horsepower. In the process of the present invention, oxygen injection at rates in excess of 3 pounds of oxygen per horsepower can be obtained using a propeller-type aeration device such as that shown in FIG. While some conventional air atomization devices claim the ability to inject oxygen at the above rates, Applicants have proposed combining both oxygen injection and flow rate induction according to the method of the present invention. I am not aware of any other air-exposure device that can do this. Figures 2a and 2b illustrate one form of the overall flow pattern according to the method of the invention.
The overall flow pattern includes the overall flow pattern within the closed region indicated by vector 40, which flows within the closed region indicated by vector 38. FIG. 5 shows another overall water flow pattern in which two sets of air venting devices are arranged side by side or adjacent to each other in a pair of closed areas. It is used to form tracts. The overall flow path within the adjacent closed region is indicated by a plurality of horizontal flow vectors 44,46. FIG. 6 shows an overall flow pattern system similar to the flow pattern systems shown in FIGS. 2a and 2b, but in which the overall flow path within the outer closure area is directed toward horizontal flow. Indicated by vector 50. The overall flow path of the inner closed region is a horizontal flow vector 52
It is shown by. The outer flow path, indicated by vector 50, is formed by the outer set of air blowers and the inner flow path is formed by two air blowers. One or more air venting devices, two of which are shown in FIG. 6 and designated by the numeral 54, are oriented out of alignment with the inner channel and toward its center. are arranged. An air venting device 54 provided outside the general flow path within the closed area is
It is directed towards the center of the channel to form a wake of water to prevent the formation of a no-flow area in the center of the pond. The wake path is indicated by horizontal parallel flow vectors 56. FIG. 7 shows a change in orientation of the air blowing devices similar to FIG. is utilized to form a general flow path within the closed area. In FIG. 7, a number of aeration devices, illustrated by the numeral 60, are indicated by the horizontal flow vector 62, to prevent the formation of dead-flow channels in the center of the pond. , arranged out of alignment with the general flow within the closed region to form wake channels. Although four pneumatic devices 60 are shown arranged out of alignment, it should be understood that many pneumatic devices can be arranged in this manner. The air aeration device of the present invention was installed in a pond where industrial wastewater flows. Propeller-type air atomization device used15
It had four horsepower air blasting devices and two 2 horsepower air blasting devices, with a total of 64 hp. The installation was done according to the method shown in Figure 2. As a result of the experiment, the BOD value was initially 2500 mg/
mg/. In other words, the BOD reduction rate is 98%
It was hot. Furthermore, eight 15-horsepower air aeration devices were used to investigate BOD by placing them in a pond into which factory wastewater was introduced.
The initial BOD was 2000mg/, but it was reduced to 10mg/
The BOD reduction rate was 95%. Numerous features and advantages of the invention are set forth in the foregoing description, together with details of its structure and function, and the novel features of the invention are pointed out in the appended claims. . However, the above disclosure is illustrative only, and within the spirit of the invention, insofar as indicated by the broad general meaning of the words expressed in the appended claims, there is no need to pay particular attention to details, particularly shapes. , may vary with respect to size and arrangement of parts.