HK1164210B - Method and apparatus for use of mixing elements in wastewater/ recycle water uv disinfection system - Google Patents

Abstract

An apparatus and method for mixing at least one fluid flowing through a fluid system using ultraviolet light to control organisms. Ultraviolet lamps are positioned in the fluid flow and arrays of triangularly shaped mixing elements are arranged at spaced intervals along the length of each lamp, wherein the plurality of arrays of triangularly shaped mixing elements create four vortices surrounding each elongated member forming a square array of vortices.

Description

Method and apparatus for using mixing element in ultraviolet disinfection system for sewage/circulating water

Cross-reference to related applications:this application claims the benefit of prior filing date under 35u.s.c. § 119(e) of U.S. provisional application serial No.61/200,292 filed 11, 16, 2008, the content of which is incorporated herein by reference.

Technical Field

The present invention relates generally to systems for controlling biological organisms using Ultraviolet (UV) light, and in particular to the mixing of fluids in systems for disinfecting fluids using UV light.

Background

Sewage treatment plants are usually guided horizontally in the flow direction using lamp racks (lamp racks) in open channels (open channels). The illuminator emits ultraviolet light (UV) that inactivates pathogenic microorganisms, making the water safe to discharge to a host receiving the water or for reuse of the water (irrigation, reuse indirectly suitable for drinking, industrial use, for miscellaneous drainage unsuitable for drinking use, etc.). The gantry holds the lamps in an array distributed over the cross-section of the channel so that water flowing down the channel is not too far from any of the lamps. Known open channel fluid treatment devices are illustrated, for example, by U.S. Pat. Nos. 4,482,809 and 5,006,244, the disclosures of which are incorporated herein by reference.

There are practical limits to how far water can be removed from the illuminator while still being adequately disinfected. Fig. 1 is a graph showing a drop in UV irradiation in water with an increase in distance from an illuminator, in which the transmittance of UV is 55% T and 65% T.

A typical UV system using a low pressure mercury arc illuminator has the illuminators spaced about 7.5cm (centimeters) apart in a square array. With a quartz tube having a diameter of 2.5cm, this means a maximum distance of about 4cm from either illuminator. This provides sufficient space for the water to flow between the illuminators without excessive head loss, and close enough to achieve sufficient UV penetration, and thus sufficient disinfection, for all areas. These low pressure systems have an illuminator with a total power consumption below 100 watts and a UVC (germicidal UV) output below 50 watts.

More recent improvements in lamp technology have produced low pressure lamps with higher output. Higher illuminator output means that more water can be disinfected per illuminator, and thus the water flow must increase in proportion to the illuminator UVC output. However, due to the head loss limit across the bank of illuminators (a-banks of lamps) (too high head loss means that the water level upstream of the bank must be raised and some of the water will overflow the top of the illuminator bank and not be adequately treated), the illuminator spacing must be increased to accommodate the greater water flow. For example, an illuminator with a power usage of 250 watts and a UVC output of about 100 watts must be contained in an array with a 10cm illuminator spacing. The additional area for water flow limits the speed and thus defines head loss across the emitter pack. This results in a reduction in UV irradiance at the point furthest from all illuminators, as shown in fig. 2.

This reduced irradiance at the furthest point from the illuminator results in some reduction in performance efficiency associated with this greater illuminator separation, especially at low UV transmittance (55% T), but the advantage of being able to use fewer illuminators overcomes the resulting increase in power usage.

More recent developments in even higher power illuminators (500 watts, with a UVC output of 200W) will potentially result in the number of illuminators required being reduced to half that of systems employing 250W illuminators. However, this means that the flow at each illuminator must be doubled, resulting in a head loss that doubles across the illuminator set (head loss is proportional to the square of the velocity), unless the spacing of the illuminators is increased more. However, increasing the spacing beyond 10cm results in a further reduction in processing efficiency, negating the potential advantages of fewer high power illuminators.

One way to overcome this is to close off the top of the illuminator bank so that water cannot overflow the top of the illuminator bank and be forced to flow at higher velocities and cause pressure losses through the illuminators with smaller illuminator spacings of 4 inches or less. This has been successfully used where much higher powered Medium Pressure (MP) illuminators (2500 watts/illuminator, 370 watts UVC) are used (U.S. patent No.5,590,390, the disclosure of which is incorporated herein by reference), and in systems employing triangular or delta wing (delta wing) mixing elements with even greater spacing and 5000 watts illuminators (750 watts UVC) (U.S. patent No.6,015,229, the disclosure of which is incorporated herein by reference). Even if the system disclosed in U.S. patent No.6,015,229 has a closed top, the illuminator spacing must be increased to reduce overall velocity and head loss. In the system disclosed in U.S. patent No.6,015,229, the 5000 watt MP illuminator is relatively short (60cm long). One disadvantage of the system disclosed in U.S. patent No.6,015,229 is that if a longer illuminator is used, the vortices (vortics) generated by the delta wing disappear and are less effective. Therefore, the system disclosed in U.S. patent No.6,015,229 is preferably used with a relatively short MP illuminator (60cm long versus the typical 1.8m (meter) length of a LP illuminator).

In the case where a delta wing array was placed at the beginning of the LP illuminator set, the vortex essentially disappeared after about 40 cm. This has been modeled using a Computational Fluid Dynamics (CFD) model and is shown in fig. 3 and 4. FIG. 3 is a velocity vortex diagram showing vortices 2cm downstream of the delta wing. FIG. 4 is a velocity swirl chart showing swirl 40cm downstream of the delta wing.

The rotational speed, and hence the ability of the vortex to mix in the water furthest from the illuminator, is characterized by the velocity vectors in figures 3 and 4, so with the longer arrow representing a higher rotational speed immediately behind the illuminator (figure 3) and the shorter arrow representing a lower rotational speed 40cm downstream of the delta wing.

Disclosure of Invention

Embodiments of the present invention include devices and methods for mixing at least one fluid flowing through a fluidic system, comprising an array of rows and columns of elongate members, wherein each elongate member is horizontally aligned with an elongate member in an adjacent column and vertically aligned with an elongate member in an adjacent row of elongate members, and wherein the axis of each elongate member is aligned with the direction of fluid flow; and a plurality of arrays of mixing elements arranged at spaced intervals along the length of each elongated member, wherein the plurality of arrays of mixing elements create four vortices around each elongated member forming a square array of vortices. Embodiments of the invention include wherein each elongated member is an ultraviolet light source, and wherein the mixing element comprises a mixing element having a triangle shape with one apex pointing upstream and at an angle to the flow direction.

Drawings

Referring now to the drawings, in which like numerals represent the same or corresponding parts throughout the several views referred to.

Fig. 1 is a graph showing UV irradiation at 55% (dashed line) and 65% water transmission per centimeter, corresponding to increasing distance from the illuminator/quartz combination shown.

Fig. 2 is a graph showing relative irradiance at a central point between 4 illuminators in a square illuminator array versus illuminator spacing between adjacent illuminators in the array.

FIG. 3 is a velocity vortex diagram showing vortices 2cm downstream of the delta wing.

FIG. 4 is a velocity swirl chart showing swirl 40cm downstream of the delta wing.

FIG. 5a is a graph of the effect of an array of zero, one, three, and four delta wings equally spaced along the length of the illuminator on the inactivation performance of microorganisms.

Fig. 5b is pilot bioassay test data of flow rate per illuminator for MS2 reduced Equivalent Dose ("RED" (Reduction Equivalent Dose)) at 67% transmittance with (dashed line) and without (delta) according to an embodiment of the present invention.

Fig. 6 is pilot bioassay test data for MS2 RED with and without delta wings (dashed lines) at 60% transmittance according to an embodiment of the present invention.

Figure 7 is pilot bioassay data for MS2 RED with and without delta wings (dashed lines) at 50% transmittance according to an embodiment of the present invention.

Figure 8 shows that a prior art implementation using delta wings has employed a delta wing array that generates 8 vortices around each illuminator. This drawing is taken from FIG. 4 of U.S. Pat. No.6,015,229.

Fig. 9 shows a vortex pattern (vortex pattern) with a smaller quartz diameter to illuminator spacing ratio proposed in patent No.6,015,229, showing that the highly treated water region near the illuminator is not stirred by the vortex wrap (sweep).

Fig. 10 is a vortex pattern with four vortices around each illuminator illustrating improved entrainment of water near the illuminator according to an embodiment of the invention.

FIG. 11 shows a triangular mixing element that produces the swirl pattern shown in FIG. 10.

Fig. 12 is a schematic diagram of an illuminator gantry having a triangular mixing component in accordance with an embodiment of the invention.

Fig. 13 is a cross-sectional view of three illuminator racks together showing a support, a wiper drive arm, a quartz tube, and a triangular mixing component, according to an embodiment of the invention.

Figure 14 is a cross-sectional view of an illuminator gantry showing a wide support directing more water through the quartz tube, according to an embodiment of the invention.

Fig. 15 is a cross-section of an illuminator gantry showing a narrow support that directs water away from a quartz tube according to the prior art.

Figure 16a shows a triangular mixing element with the apex removed, according to an embodiment of the present invention.

Fig. 16b shows a triangular mixing element with the top not removed.

Figure 17 shows a half triangular mixing element at the bottom of a channel according to an embodiment of the present invention.

Fig. 18 is a schematic view of a half-triangular mixing element according to an embodiment of the invention.

Figures 19a and 19b are side and end views showing an illuminator rack in an open channel with semi-triangular mixing members at the top and bottom water levels of the channel, according to an embodiment of the invention.

FIG. 20 is an alternative triangular mixing member support arrangement with fixed vertical support bars or strips according to an embodiment of the invention.

FIG. 21 is an alternative triangular mixing member support arrangement with removable vertical support bars or strips according to an embodiment of the invention.

Fig. 22 is a possible layout for a closed vessel reactor with an array of four illuminators according to an embodiment of the invention.

Fig. 23 shows a perspective view of a closed vessel reactor, according to an embodiment of the invention.

Fig. 24 is a longitudinal cross-sectional view of the closed vessel reactor of fig. 23.

Fig. 25 is a cross-sectional end view of the closed vessel reactor of fig. 23.

FIG. 26 is a cross-sectional end view of a closed vessel reactor showing a quartz cleaning mechanism, according to an embodiment of the invention.

Fig. 27 is a layout of a closed vessel reactor for an array having sixteen illuminators, according to an embodiment of the invention.

Detailed Description

Embodiments of the invention employ more than one array of delta wings (triangular mixing elements) at spaced intervals along the length of the UV illuminator in a system that uses the UV illuminator for fluid disinfection. The layout of the triangular hybrid component array was tested using a computational fluid dynamics model in combination with a model of the irradiation field to simulate microbial inactivation. The effect of an array of zero, one, three and four triangular mixing elements equally spaced along the length of the illuminator on the microbial inactivation performance is shown in figure 5 a. It can be seen that the arrangement of three triangular mixing elements spaced along the illuminator has improved performance over a layout having only one array of triangular mixing elements.

This layout of three triangular mixing element arrays spaced along the length of the UV illuminator was tested using a lead system at a sewage treatment plant using the surrogate (surrogate) microorganisms MS2 phage and T1 phage (known surrogate organisms used in bioassays), with and without the triangular mixing elements. The spacing of the illuminators on the test system was 6 inches (15 cm).

Except for the test, untreated water was about 67% UV transmittance, which was adjusted to 60% T and 50% T using humic acid to simulate natural low transmittance water. Figures 5b, 6 and 7 show the performance improvement achieved with and without the three triangular mixing element arrays.

Previous embodiments using triangular mixing elements have employed an array of triangular mixing elements that generate eight vortices around each illuminator. This is shown in figure 4 of us patent No.6,015,229, reproduced here as figure 8, in which the UV illuminator 5 is surrounded by a tube 13 and each triangular mixing element produces a pair of counter-rotating vortices 10.

The idea proposed in us patent No.6,015,229 is to take highly treated water close to the illuminator and remove it therefrom, and to take untreated or lightly treated water away from the illuminator and move it close to the illuminator.

This arrangement is not suitable for systems in which the ratio of quartz diameter to lamp spacing is lower than that proposed in us patent No.6,015,229 because the vortex does not entrain a large portion of the highly treated water near the lamps as illustrated in figure 9. In particular, FIG. 9 illustrates what would happen if the layout disclosed in U.S. Pat. No.6,015,229 were used with a smaller quartz diameter to illuminator spacing ratio. As illustrated, the vortex pattern shows a highly treated water region near the illuminator that is not affected by the vortex or is not stirred away by the wrap.

The layout of embodiments of the present invention is more suitable for systems where the ratio of quartz diameter to illuminator spacing is lower than that proposed in U.S. patent No.6,015,229. In an embodiment of the invention, as shown in FIG. 10, four large vortices 20 surround each illuminator 22, forming a square vortex array. It can be seen that the vortex is positioned adjacent to the illuminator 22, taking the highly treated water and moving it away from the illuminator 22, and conversely taking the water away from the illuminator (at a central point 24 between the four illuminators 22) and moving it closer to the illuminator 22.

As shown in FIG. 11, the layout of the present invention has a triangular wing or triangular mixing element 26 that creates a vortex pattern having four vortices 20 disposed adjacent the illuminator. Each triangular mixing section 26 is directed upstream with one apex and is arranged at an angle to the flow direction. As illustrated in fig. 11, pairs of triangular mixing sections 26 are arranged back-to-back such that the longest side 28 of each triangular mixing section 26 is arranged parallel to and adjacent to the longest side (trailing edge) 28 of the other triangular mixing section 26 in the pair.

Each triangular mixing element 26 creates a pair of counter-rotating vortices 20 and the back-to-back triangular mixing elements 26 create four counter-rotating vortices 20 that rotate substantially all of the water in the space between each pair of four surrounding lamps 22. This opposite rotation is important in terms of the vortices 20 strengthening each other in terms of higher rotational velocity and longer persistence. This arrangement of triangular mixing components 26 is also preferred from a mechanical perspective because the triangular mixing components 26 can be attached to their respective illuminator racks, and the entire illuminator rack assembly can be removed without affecting adjacent illuminator racks. This is important for routine maintenance of the UV disinfection system in the tunnel. Support rods 30 that hold the triangular mixing elements 26 in place are also shown in fig. 11. As can be seen therein, the rods 30 are positioned so as to be outside the entrainment range of the two counter-rotating vortices 20 created by each triangular mixing segment 26, but still in a favorable position to be able to secure the trailing edge of the triangular mixing segment 26.

An assembled illuminator gantry 32 (each gantry 32 having three illuminators 22) in a preferred embodiment of the system is shown in fig. 12. Additional supports 34 are placed further towards the tip (lead angle) 35 of each triangular mixing element 26. The second support 34 is used to properly align the angle (angle of attack) of the triangular mixing element 26 with the direction of flow and further secure the triangular mixing element 26 in place. The second support 34 is also positioned at the centerline of the triangular mixing member 26 so as not to interfere with the rotational entrainment of the vortex 20.

In embodiments of the invention, the illuminator gantry layout 32 is provided with four, six, or eight vertical illuminators 22 per gantry 32. However, any number of illuminators 22 may be included in a single gantry 32. A number of racks 32 are arranged adjacent to one another to form an illuminator array for use in an open channel UV disinfection system. FIG. 13 illustrates a cross-sectional view of three illuminator gantries 32 together, showing the support 36, the scraper drive arm 38, the quartz tube containing the illuminator 22, and the triangular mixing component 26. The illuminators 22 are arranged in a square array in this and other disclosed embodiments such that each illuminator 22 is horizontally aligned with illuminators 22 in adjacent columns of illuminators and vertically aligned with illuminators 22 in adjacent rows of illuminators.

Most open channel gantries mounted to UV systems have vertical support members 40 at each end of the illuminator gantry to support the quartz tube and illuminator 22. As shown in the cross-sectional view of fig. 15, the vertical support in the prior art system is disposed close to the illuminator. This tends to force water away from the lamps, into the region between the lamps, and results in reduced performance of the UV system.

As shown in fig. 14, in the embodiment of the present invention, this is improved by having a wide support 36, which wide support 36 blocks water on the vertical plane farthest from the illuminator 22 and guides more water on the vertical plane of the illuminator 22. Fig. 14 also illustrates the location of an open area around the illuminator 22, and obstructions to flow (support legs) are located away from the illuminator 22.

A UV sensor (not shown) for measuring UV radiation in the water is placed between two quartz tubes in the illuminator stand. It is desirable to clean the sensor and the quartz tube with a scraper (scraper) or scraper member that moves periodically along the length of the illuminator. The wiper assembly may be driven by a vertical wiper drive arm 38 constrained to a (finished to) motor driven screw drive 41. Examples of doctor blades are disclosed in U.S. patent No.7,159,264, the disclosure of which is incorporated herein by reference. Embodiments of the present invention have an improved triangular mixing element 260 with the apex removed. The improved triangular mixing member 260 provides sufficient clearance between the sensor wiper and the triangular mixing member 260. The tip of the triangular mixing member 260 may interfere with the motion of the UV sensor wiper. Fig. 16a and 16b show triangular mixing elements 260 with their tips removed and triangular mixing elements 26 with their tips not removed. Fig. 13 illustrates the necessary clearance for the squeegee drive arm 38.

Computer modeling of CFD and irradiation intensity fields has been done to show through the reactor that this tip removal has little effect on microbial inactivation.

Embodiments of the invention also use half-triangular mixing members 42 at the top and bottom of the illuminator rig. This generates a single complete vortex in the same way that a complete triangular mixing element generates a pair of vortices, as shown in figure 17. Since the bottom of the tunnel is located at the center point between the two illuminators, the half-triangular mixing element 42 moves up approximately 0.7cm to accommodate the support rod 30. Fig. 18 shows a half triangular mixing element 42. Figures 19a and 19b show the illuminator gantry in an open channel with semi-triangular mixing members 42 at the top and bottom water levels of the channel.

An alternative arrangement for supporting the triangular mixing elements 26 is through the use of vertical support bars or strips 44, as shown in fig. 20. This has several disadvantages and advantages over the horizontal support arrangement described above. The vertical supports 44 create more obstruction to water flow, resulting in higher head loss through the reactor and also breaking the vortex to some extent. However, in a large illuminator rig (e.g., vertically stacking eight illuminators), each rod supports seven complete triangular mixing members and two half triangular mixing members. This is in contrast to three triangular mixing elements per rod in a horizontal support arrangement. This therefore reduces the system cost. In addition, the use of the vertical support bar 44 makes it possible to remove the triangular mixing member (for example for cleaning) without having to remove the entire housing. This is important in more dirty waters where triangular mixing elements may have a tendency to accumulate waste clusters (algae), which are common in sewage from secondary sewage treatment plants.

An alternative support arrangement with removable vertical support rods or bars 440 is shown in fig. 21. In addition, it is possible that a single rod supports both of the triangular mixing component pairs between the illuminator racks, in which case, in the eight illuminator rack embodiment cited above, a single rod supports fourteen full triangular mixing components and four half triangular mixing components, further reducing cost.

As shown in fig. 22 to 27, embodiments of the present invention include arrangements in closed vessel reactors. Similar to that described above in the open channel embodiment, the vortex array can be generated in a closed vessel UV disinfection system, where the illuminator is enclosed in the tubular vessel with flow in the vessel length direction, and the illuminator is parallel to the flow.

Fig. 22 shows a tubular reactor 46 of four illuminators 22. The additional mixing provided by the triangular mixing component 26 enables the reactor to be used with water having a lower UV transmittance because, in an open channel arrangement, the vortex 20 generated by the triangular mixing component 26 carries the water furthest from the illuminator 22 to close the illuminator 22 and removes the water closest to the illuminator 22 from the illuminator 22. As shown in fig. 23, such a reactor 46 may have an inlet 48 and an outlet 50, with the inlet 48 flowing horizontally to the illuminator and the outlet 50 flowing water transversely to the illuminator.

In an open channel reactor, one or more sets of triangular mixing elements 26 are positioned at spaced intervals along the length of the illuminator. Fig. 24 shows three groups. A screw drive 410 (fig. 24-26) driving the quartz cleaning member 52 moves centrally through the length of the reactor 46.

Fig. 27 shows an array of sixteen illuminators with four rows of four illuminators 22 each. In a similar manner, an array of nine, twenty-five, or thirty-six illuminators may be produced by three rows of three illuminators 22 each, five rows of five illuminators 22 each, or six rows of six illuminators 22 each, respectively. In larger arrays, baffles (not illustrated) may be included to prevent water from flowing into the area near the wall not covered by the vortex.

Any and all patents, patent publications, articles and other printed publications discussed or referred to herein, if not otherwise indicated, are hereby incorporated by reference as if fully set forth herein.

It should be understood that the apparatus and methods of the present invention may be configured and implemented as suitable for use in any of the present environments. The above-described embodiments should be considered in all respects as illustrative and not restrictive.

Claims (20)

1. An apparatus for mixing at least one fluid flowing through a fluid system, the apparatus comprising:

an array of elongate members, wherein each elongate member is horizontally aligned with elongate members in adjacent columns and vertically aligned with elongate members in adjacent rows of elongate members, and wherein the axis of each elongate member is aligned with the direction of fluid flow; and

a plurality of triangular mixing element pairs arranged at spaced intervals along the length of each elongate member, each triangular mixing element pair being arranged such that the longest side of each triangular mixing element is parallel to and adjacent to the longest side of the other triangular mixing element of the each triangular mixing element pair.

2. The apparatus of claim 1, wherein each elongated member is an ultraviolet light source.

3. Apparatus as claimed in claim 1 or 2, wherein the portion of the triangular mixing element has an apex pointing upstream and at an angle to the direction of flow.

4. The device of claim 1 or 2, wherein the mixing elements comprise mixing elements having a half-triangular shape, and wherein the half-triangular mixing elements are arranged along the elongated members in an area of the device not enclosed by four elongated members.

5. The apparatus of claim 1 or 2, wherein the mixing element is mounted on a horizontal support bar.

6. The apparatus of claim 1 or 2, wherein the mixing element is mounted on a vertical support rod.

7. The apparatus of claim 1 or 2, wherein the elongate members are vertically arranged on a rack and the mixing elements are mounted on vertical support rods that are respectively removable from the rack.

8. The apparatus of claim 7, wherein each rack comprises a rack having spaced apart vertical bars creating an open area around the elongated member.

9. The device of claim 1, wherein the leading apex of one or more triangular mixing elements is removed.

10. The device of claim 1 or 2, the fluidic system being a closed channel system.

11. A method for mixing at least one fluid flowing through a fluid system, the method comprising:

submerging a device in the fluid flow, wherein the device comprises:

an array of elongate members, wherein each elongate member is horizontally aligned with elongate members in adjacent columns and vertically aligned with elongate members in adjacent rows of elongate members, and wherein the axis of each elongate member is aligned with the direction of fluid flow;

a plurality of triangular mixing element pairs arranged at spaced intervals along the length of each elongate member, each triangular mixing element pair being arranged such that the longest side of each triangular mixing element is parallel to and adjacent to the longest side of the other triangular mixing element of the each triangular mixing element pair.

12. The method of claim 11, wherein each elongated member is an ultraviolet light source.

13. The method of claim 11 or 12, wherein the portion of the triangular mixing element has an apex pointing upstream and at an angle to the flow direction.

14. The method of claim 11 or 12, wherein the mixing elements comprise mixing elements having a half-triangular shape, and wherein the half-triangular mixing elements are arranged along the elongated members in an area of the device not enclosed by four elongated members.

15. A method as claimed in claim 11 or 12, wherein the mixing elements are mounted on a horizontal support bar.

16. A method as claimed in claim 11 or 12, wherein the mixing elements are mounted on a vertical support bar.

17. A method as claimed in claim 11 or 12, wherein the elongate members are vertically arranged on a frame and the mixing elements are mounted on vertical support rods which are respectively removable from the frame.

18. The method of claim 17, wherein each rack comprises a rack having spaced apart vertical bars creating an open area around the elongated member.

19. The method of claim 11, wherein the leading apex of one or more triangular mixing elements is removed.

20. The method of claim 11 or 12, wherein the fluid system is a closed channel system.