Systems and methods for reducing hydrogen sulfide levels in wastewater and / or for producing unltrfine bubbles for a variety of nanobubble-enhanced processes

Abstract

A method for reducing hydrogen sulfide levels in wastewater flowing through a sewerage system. The method includes the steps of: providing a pumping station within the sewerage system that has a reservoir chamber and a pump for urging pressurized wastewater out of the pumping station. Also in this method is provided a recirculation loop that redirects part of the wastewater flowing through the pumping station back towards the reservoir chamber. And in addition, along the recirculation loop and / or in association with reservoir chamber is located an ultrafine bubble system that is designed to introduce ultrafine bubbles including an aeration gas into the wastewater.

Description

[0001] SYSTEMS AND METHODS FOR REDUCING HYDROGEN SULFIDE LEVELS IN WASTEWATER AND / OR FOR PRODUCING UNLTRFINE BUBBLES FOR A VARIETY OF NANOBUBBLE-ENHANCED PROCESSES TECHNICAL FIELD

[0001] Embodiments of the invention relate to systems and methods for reducing hydrogen sulfide levels in wastewater, in particular in pumping stations, force mains and wastewater treatment systems and / or for producing ultrafine bubbles for a variety of nanobubble-enhanced processes. BACKGROUND

[0002] Sewage treatment, also known as domestic or municipal wastewater treatment, is a process for removing contaminants from sewage, producing an effluent that can be safely discharged into the environment or reused for specific purposes.

[0003] Sewage typically includes wastewater from households, businesses, and sometimes pre-treated industrial wastewater. There are numerous sewage treatment methods available, ranging from decentralized systems, like on-site treatment, to large centralized systems that use networks of pipes and pump stations to transport sewage to a treatment facility.

[0004] Sulfide can be formed during sewage conveyance and treatment, particularly under anaerobic conditions. In sewage treatment, organic matter is broken down by bacteria, and in the absence of oxygen, sulfate-reducing bacteria can use sulfate as an electron acceptor, reducing it to hydrogen sulfide (H₂S). This process occurs mainly under anaerobic conditions, such as sewage conveyance pipes, in sludge digesters or in the anaerobic zones of sewage conveyance and treatment systems.

[0005] Hydrogen sulfide is a gas that can cause odor issues and corrosion in sewage conveyance and treatment facilities. Therefore, managing hydrogen sulfide levels is an important aspect of sewage conveyance and treatment.

[0006] Odor control systems including: Biofilters, activated carbon filters, or chemical scrubbers can be used to treat gases in the air emitted from wastewater treatment plants, capturing hydrogen sulfide before it is released into the environment.

[0007] However these types of solutions are often quite capital intensive, where the costs can be attributed to several factors, including: Installation Costs, Operational Costs, Maintenance Requirements (and the like).

[0008] Some chemicals can be added to sewage systems to quench hydrogen sulfide but they are costly, sometimes hazardous and add a chemical load to the sewer system.

[0009] Lowering the levels of hydrogen sulfide (H₂S) in sewage systems may include inducing ultrafine bubbles (including nanobubbles) into the wastewater, particularly ultrafine bubbles containing oxygen or ozone.

[0010] Ultrafine bubbles may be used in a variety of nanobubble-enhanced processes, such as in water treatment and purification, aquaculture, Mining and Mineral Processing, Agriculture and Irrigation, Food & Beverage Industry (etc.). SUMMARY

[0011] The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods which are meant to be exemplary and illustrative, not limiting in scope.

[0012] In an embodiment there is provided a method for reducing hydrogen sulfide levels in wastewater flowing through a sewerage system, the method comprising the steps of: providing a pumping station within the sewerage system that comprises a reservoir chamber and a pump for urging pressurized wastewater out of the pumping station, providing a recirculation loop for redirecting part of the wastewater flowing through the pumping station back towards the reservoir chamber, and locating along the recirculation loop and / or in association with reservoir chamber at least one ultrafine bubble system that is configured to introduce ultrafine bubbles comprising an aeration gas into the wastewater.

[0013] In an embodiment there is also provided an auxiliary system for reducing hydrogen sulfide levels in wastewater flowing through a pumping station of a sewerage system, the auxiliary system comprises: a recirculation loop for redirecting part of the wastewater flowing through the pumping station back towards a reservoir chamber of the pumping station, and at least one ultrafine bubble system for introducing ultrafine bubbles comprising an aeration gas into the wastewater flowing through the pumping station, wherein the at least one ultrafine bubble system is located along the recirculation loop and / or in association with the reservoir chamber of the pumping station.

[0014] In yet a further embodiment there is also provided a generator for generating ultrafine bubbles for a variety of nano-bubble enhanced processes, the generator having a generally disc shape formation formed about a central axis and comprises axially spaced apart first and second planar faces and a plurality of atomizers for generating ultrafine bubbles.

[0015] And in yet a further embodiment there is provided a generator for generating ultrafine bubbles for a variety of nano-bubble enhanced processes, the generator comprising: an outer housing, a cone-shaped structure comprising an internal passage passing therethrough along the structure’s cone axis, wherein the cone-shaped structure being oriented in an inverted manner within the housing with its wider open end at the top.

[0016] In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the figures and by study of the following detailed descriptions. BRIEF DESCRIPTION OF THE FIGURES

[0017] Exemplary embodiments are illustrated in referenced figures. It is intended that the embodiments and figures disclosed herein are to be considered illustrative, rather than restrictive. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying figures, in which:

[0018] Fig. 1A schematically shows a map of an urban area and a sewerage system in accordance with an embodiment of the present invention for transporting wastewater collected from the urban area to a treatment facility;

[0019] Fig.1B schematically shows only the sewerage system seen in Fig.1A;

[0020] Fig. 2 schematically shows a pumping station within the sewerage system of Fig. 1, incorporating one or more ultrafine (e.g. Nano) bubble systems in accordance with various embodiments of the invention for reducing the sulfide levels in wastewater of the sewerage system;

[0021] Fig.3 schematically shows an embodiment of an ultrafine bubble system;

[0022] Figs. 4A and 4B schematically show perspective top and bottom views of a generator for generating ultrafine bubbles, which may be used in the ultrafine bubble system of Fig.3;

[0023] Fig. 5 schematically shows an exploded view of the generator revealing interior sides of two segments of the generator;

[0024] Fig.6 schematically shows a partial cross sectional view of the generator;

[0025] Fig. 7 schematically shows a cross sectional view of the generator taken along plane VII-VII marked in Fig.6;

[0026] Figs. 8A and 8B schematically show another embodiment of an ultrafine bubble system; and

[0027] Fig. 9 schematically shows a pumping station within the sewerage system of Fig. 1, incorporating one or more ultrafine (e.g. Nano) bubble systems in accordance with various embodiments of the invention for reducing the sulfide levels in wastewater of the sewerage system.

[0028] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated within the figures to indicate like elements. DETAILED DESCRIPTION

[0029] Attention is first drawn to Fig. 1A schematically showing a map 10 of an urban area and a sewerage system 100 in accordance with an embodiment of the present invention for transporting wastewater collected from the urban area to a treatment facility 12. With attention additionally drawn to Fig. 1B, elements of the sewerage system 100 can be seen in isolation without the map in the background.

[0030] Here the sewerage system 100 can be seen including a network of pipes and pumping stations 14 for transporting sewage to a treatment facility. The ‘dotted’ lines represent pressure pipes 16 along which wastewater is pumped or pressurized to move through a system, typically against gravity or over long distances. The ‘continuous’ lines represent gravity pipes 18 that rely on the natural slope or gradient of the terrain to move wastewater from higher elevations to lower elevations.

[0031] Attention is drawn to Fig. 2 schematically showing a pumping station 14 within the sewerage system 100. Such a pumping station 14 typically includes an incoming chamber 141 for receiving incoming wastewater arriving e.g. from one or more pressure and / or gravity pipes 16, 18.

[0032] From incoming chamber 141 the wastewater, as seen in this example, can flow downstream towards a screening chamber 142, which in this example can be seen including a bar screen 7 that has a primary function of filtering out of the wastewater relatively large debris such as rags, wipes, sticks, plastics (and the like).

[0033] From the screening chamber 142 the wastewater can flow onwards downstream to a reservoir chamber 143 (normally called the wet chamber) where wastewater is temporarily collected and stored, before flowing towards a pump 144 that functions to urge pressurized wastewater onwards downstream out of the pumping station 14 via a pressure pipe (force main) 16 to flow through the sewerage system 100.

[0034] It is noted that incoming chamber 141, screening chamber 142, reservoir chamber 143 and pump 144 - are all typical possible elements of a pumping station 14.

[0035] In an embodiment of the present invention, the pumping station 14 may be provided with an auxiliary system 800 including a recirculation loop 145 for redirecting part of the wastewater from the pump 144 back towards the reservoir chamber 143.

[0036] In this example the recirculation loop 145 includes a screening chamber 7 and a downstream operational tank 8. The screening chamber 7 is adapted to filter out of the recirculated wastewater relative small sized debris from being recirculated back via the operational tank 8 towards reservoir chamber 143.

[0037] In one example, the screening chamber 7 is adapted to remove debris ranging in size from about 1 millimeter and larger from being recirculated towards the operational tank 8 and onwards back to the reservoir chamber 143.

[0038] Within the operational tank 8 and possibly also other sections of the pumping station 14, such as the reservoir chamber 143, may be located an ultrafine bubble system 5 of the auxiliary system 800 that is adapted to introduce ultrafine bubbles including an aeration gas such as oxygen and / or ozone into the wastewater. Such ultrafine bubbles typically have a diameter on the scale of nanometers, e.g. from about 20 to 200 nanometers (nm).

[0039] The ultrafine bubble systems described herein (such as systems 50 and 500) and their respective generators (55, 550), will be described with respect to their utilities in lowering levels of hydrogen sulfide (H₂S) by inducing ultrafine bubbles containing gaseous such as oxygen and / or ozone into wastewater. Nevertheless, it is noted that these ultrafine bubble systems and generators may be used for a variety of other nanobubble-enhanced processes, such as water treatment and purification, aquaculture, Mining and Mineral Processing, Agriculture and Irrigation, Food and Beverage Industry (etc.). The gaseous used in such nanobubble-enhanced processes may vary and may include e.g. any one of oxygen, ozone, Ethylene, CO2 (and the like) depending on the intended application.

[0040] Additionally, it is noted that the ultrafine bubble systems described herein (such as systems 50 and 500) and, more specifically, their respective generators (55, 550), can be positioned either inside or outside the tanks or reservoirs where the ultrafine bubbles are intended to be introduced. For instance, adapting generator 55 to discharge liquid containing ultrafine bubbles from an external location into a tank or reservoir may involve placing the generator 55 in a separate body of liquid outside the tank or reservoir, with its primary and secondary ports (771, 772) submerged in this body of liquid. The liquid, now infused with ultrafine bubbles, may then be directed into the target tank or reservoir.

[0041] Attention is drawn to Fig. 3 schematically showing an embodiment of an ultrafine bubble system 50. The ultrafine bubble system 50 includes an incoming cell 51, in this example including openings each covered with a screen 52 for filtering wastewater being sucked into the cell 51 via a pump 53 of the system.

[0042] The pump 53 in turn transfers the incoming wastewater in this example via a main tube 541 to a juncture 542 where the wastewater branches off towards two primary tubes 543 and one secondary tube 544.

[0043] Each primary tubes 543 branches off in this example into two coupling tubes 545, which are each connected via the coupling tube to a generator 55. Through the primary and coupling tubes 543, 545, pressurized wastewater is channeled towards the generators 55 for generating ultrafine bubbles.

[0044] The secondary tube 544 may be adapted to periodically divert some of the pressurized wastewater back into the upper side of the incoming cell 51 to a rotating emitter (not seen) that emits this pressurized wastewater towards the inner sides of the screens 52 to dislodge dirt accumulated on the outer sides of screens 52 during use.

[0045] Attention is drawn to Figs. 4A and 4B schematically showing perspective top and bottom views of an embodiment of a generator 55 for generating ultrafine bubbles. Generator 55 may be made from a variety of materials, such as PVDF, PVC, Aluminum, Teflon (and the like).

[0046] The generator 55 has a disc shape formation with opposing first and second planar faces 551, 552. The disc shape of the generator is formed about a central axis C, with a through going opening 553 formed extending along axis C at its center. The generator has in addition several (here eight) atomizers 77 that are symmetrically distributed therein about axis C.

[0047] Each atomizer 77 includes primary and secondary ports 771, 772 opening out of the atomizer, respectively, at the generator’s first and second planar faces 551, 552. Each atomizer 77 includes in addition an inlet 6 that opens out into the generator’s opening 553.

[0048] As seen in the enlarged section in Fig. 4B, inlet 6 preferably has a cross sectional elongated, possibly oval, shape formed along an axis L, which is generally parallel to axis C of the generator.

[0049] As seen in Fig. 4A, the generator 55 includes a peripheral support 554 that is located above the generator’s first planar face 551. The support 554 supports a plurality of inserts 555 located each above a primary port 771 of a respective one of the atomizers 77. Each insert in turn at its side that is distal to the generator is connected to a conduit 556 that is adapted to supply an aeration gas towards the insert during use of the generator. Preferably the aeration gas is ozone.

[0050] Attention is drawn to Fig. 5 schematically showing an exploded view of the generator 55 revealing interior sides 11, 22 of two segments 1, 2 of the generator.

[0051] Each atomizer 77 can be seen including a swirl chamber 9 divided into two primary and secondary sections 91, 92. The atomizer’s primary port 551 opens into the swirl chamber’s primary section 91 and the atomizer’s secondary port 552 opens into the swirl chamber’s secondary section 92.

[0052] Also seen in this figure is that the atomizer’s inlet 6 is divided into two primary and secondary inlet sections 61, 62 each being formed, respectively, on the first and second segments 1, 2 of the generator.

[0053] Also, an inlet channel 88 is provided for leading fluid into each swirl chamber 9 from its inlet 6, and said inlet channel 88 can be seen being divided into primary and secondary channel section 881, 882 formed, respectively, on the first and second segments 1, 2 of the generator.

[0054] In an assembled state of the generator 55, the two segments 1, 2 of the generator 55 are attached one to the other at an interface formed where their interior sides 11, 22 engage.

[0055] The two segments 1, 2 are attached to each other with the various corresponding elements located on each segment and forming each atomizer 77 being aligned one with the other to form functioning atomizers.

[0056] For example, primary and secondary sections 91, 92 of each swirl chamber 9 are aligned one over the other, primary and secondary inlet sections 61, 62 of each inlet 6 are aligned one over the other, and primary and secondary channel section 881, 882 of each inlet channel 88 are aligned one over the other.

[0057] Attaching segments 1, 2 in a sealing manner one to the other to form a functioning generator 55 where the flow channels of each atomizer are sealed against unintentional leakage at the interface where the segments engage, may be accomplished using screws and / or adhesives.

[0058] With attention drawn to the enlarged section at the upper side of Fig. 5, a peripheral recess 33 is seen possibly formed on at least one of the interior sides (here 11) of the generator segments. This recess 33 as seen substantially bounds the elements of the atomizer formed on this interior side (see, e.g.61, 881, 91).

[0059] Adhesive 44 (see marked in gray) placed within such a recess 33 may then be used to assist in sealing against unintentional leakage at the interface where the segments engage, while also bonding together the segments.

[0060] Attention is drawn to Figs. 6 and 7 schematically showing, respectively, a partial cross sectional view of the generator 55, and a cross sectional view of the generator taken along plane intersecting one of its atomizers 77 revealing, inter alia, the swirl chamber 9 of this atomizer.

[0061] As seen in Figs. 6 and 7, inlet channel 88 tangentially intersects with a peripheral surface 99 surrounding the swirl chamber 9 at a generally cylindrical portion of surface 99. The intersection may be preferably smooth without an abrupt change in direction of the incoming liquid into the swirl chamber. A transition zone 89 where a gradual blend or fillet at the intersection can be seen where inlet channel 88 transitions into the swirl chamber 9.

[0062] Designing the entry of inlet channel 88 into the swirl chamber 9 to be generally tangential, facilitates a flow path into swirl chamber 9 with minimal disruption that assists to create a swirling or vortex motion within the swirl chamber 9.

[0063] Additionally, designing inlet 6 (and inlet channel 88) with an elongated cross-sectional shape along axis L directs the incoming wastewater flow along the peripheral surface 99 of the swirl chamber, thereby enhancing the formation of ultrafine bubbles.

[0064] Fluid (e.g. ozone, or the like) supplied via insert 555 towards primary port 771 may be urged through primary port 771 into the atomizer’s swirl chamber due to suction ignited via vacuum created within the swirl chamber, e.g. by the swirling motion of the wastewater.

[0065] Interaction between the incoming gas (e.g. ozone) and the swirling wastewater within the atomizer is arranged to produce ultrafine bubbles (e.g. nano bubbles), which may then be ejected out of the atomizer 77 via its primary 771 and secondary 772 ports.

[0066] As seen in Fig. 6, the generator may include primary and secondary ledges 101, 102 formed, respectively, along sections of peripheral walls of the first and second segments 1, 2 of the generator that surround opening 553. These ledges 101, 102 are located on opposing sides of the openings 6 and function a limits against which ends of tubes, such as coupling tubes 545, may engage.

[0067] Wastewater provided via such a tube to the generator may be free to flow via the inlets 6 (which remain unconcealed) into the swirl chambers of the generator in order to generate ultrafine bubbles. In certain cases, a tube section having a closed end (such as tube section 546 in Fig. 3) may be placed against the opposing ledge in cases where only one generator 55 is being “fed” with wastewater.

[0068] If additional generators 55 are to be “fed” with wastewater, opened ended tubes (such as 545) may be placed as extensions (instead of tube section 546) for feeding such additional generators 55.

[0069] These ultrafine bubbles produced within each generator 55 at its atomizers 77 when being fed into the wastewater assist in managing sulfide levels in the wastewater that is then fed out of the pumping stations 14 via pressure pipes 16.

[0070] Attention is drawn to Figs. 8A and 8B schematically showing another embodiment of an ultrafine bubble system 500. The ultrafine bubble system 500 includes a generator 550 having an outer housing 501 that encloses a cone-shaped structure 502 with a spiral rib 503 formed around its outer periphery. The cone- shaped structure 502 is oriented in an inverted manner within the housing with its wider open end 510 positioned at the top.

[0071] A bulge 509 extending downwards from the upper side of the housing towards the upper open side 510 of the cone-shaped structure is adapted to encourage wastewater flowing through generator 550 to enter into the upper open side 510.

[0072] The spiral rib 503 is adapted to guide incoming wastewater, which enters a lower side of the housing through a main incoming tube 504, to generally flow along a path it defines in a swirling motion upwards towards the cone’s upper open side 510. The wastewater is then directed into a hollow passage 505 extending through the cone structure along the cone’s axis - to flow downwards and exit the housing at an outlet tube 507 at its lower side.

[0073] Preferably, an internal diameter Ø2 of outlet tube 507 and an internal diameter Ø1 of incoming tube 504 may be sized such that Ø2 may be larger than Ø1. For example, Ø2 and Ø1 may satisfy a ratio of: Ø2 being equal to between about one and a half and two times Ø1 (i.e. to 2 x Ø1). Such sizing of Ø2 to be larger than Ø1 may assist in forming a pressure drop along the flow paths through generator 550 (e.g. along its cone-shaped structure), so that immediately downstream to throat 508, a suitable pressure may be formed for drawing gaseous to be infused with the liquid flowing into the generator’s outer housing 501

[0074] During the wastewater's entry into the housing via incoming tube 504, a gas such as oxygen or ozone in this example, is introduced into the wastewater through a separate inlet tube 506 that merges into the incoming tube 504. A liquid such as wastewater flowing downstream through incoming tube 504 passes through a throat 508 (e.g. a narrowed section) of incoming tube 504 just before the point where inlet tube 506 merges into it.

[0075] The liquid flowing through throat 508 increases its velocity while decreasing in pressure (according to Bernoulli's principle). The lower pressure of the liquid at the throat 508 creates a condition where gas supplied via inlet tube 506 can more easily dissolved into the liquid.

[0076] The combination of the wastewater's swirling motion along the spiral ledge 503 and the gaseous introduced into the system generates nano-bubbles in the wastewater. As a result, the water exiting the system is infused with e.g. oxygen or ozone in the form of nano-bubbles.

[0077] Attention is drawn to Fig. 9 schematically showing a pumping station 14 within the sewerage system of Fig. 1, incorporating an auxiliary system 8000 having one or more ultrafine (e.g. Nano) bubble systems 5 in accordance with various embodiments of the present invention.

[0078] In the example of auxiliary system 8000, the ultrafine bubble systems 5 are located outside of the wastewater in reservoir chamber 143 and operational tank 8. Wastewater flowing through the pumping station 14 may be fed into such ultrafine bubble systems 5 and the wastewater with induced ultrafine bubbles may be emitted / discharged back into chambers and / or tanks of such a pumping station.

[0079] An ultrafine bubble systems in the form of ultrafine bubble system 500 with its generator 550 - may be used in the manner described with respect to Fig. 9, with main incoming tube 504 being used to feed wastewater flowing through pumping station 14 into the ultrafine bubble system and outlet tube 507 being used to emit / discharge wastewater with induced ultrafine bubbles back into chambers and / or tanks of such a pumping station 14.

[0080] In the description and claims of the present application, each of the verbs, “comprise” “include” and “have”, and conjugates thereof, are used to indicate that the object or objects of the verb are not necessarily a complete listing of members, components, elements or parts of the subject or subjects of the verb.

[0081] Further more, while the present application or technology has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and non- restrictive; the technology is thus not limited to the disclosed embodiments. Variations to the disclosed embodiments can be understood and effected by those skilled in the art and practicing the claimed technology, from a study of the drawings, the technology, and the appended claims.

[0082] In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures can not be used to advantage.

[0083] The present technology is also understood to encompass the exact terms, features, numerical values or ranges etc., if in here such terms, features, numerical values or ranges etc. are referred to in connection with terms such as “about, ca., substantially, generally, at least” etc. In other words, “about 3” shall also comprise “3” or “substantially perpendicular” shall also comprise “perpendicular”. Any reference signs in the claims should not be considered as limiting the scope.

[0084] Although the present embodiments have been described to a certain degree of particularity, it should be understood that various alterations and modifications could be made without departing from the scope of the invention as hereinafter claimed.

Claims

CLAIMS:

1. A method for reducing hydrogen sulfide levels in wastewater flowing through a sewerage system, the method comprising the steps of: providing a pumping station within the sewerage system that comprises a reservoir chamber and a pump for urging pressurized wastewater out of the pumping station, providing a recirculation loop for redirecting part of the wastewater flowing through the pumping station back towards the reservoir chamber, and locating along the recirculation loop and / or in association with reservoir chamber at least one ultrafine bubble system that is configured to introduce ultrafine bubbles comprising an aeration gas into the wastewater.

2. The method of claim 1 and comprising an operational tank located along the recirculation loop and the at least one ultrafine bubble system is associated with the operational tank.

3. The method of claim 1 or 2, wherein the aeration gas comprises oxygen and / or ozone.

4. The method of any one of the preceding claims, wherein the at least one ultrafine bubble system comprises at least one generator for generating the ultrafine bubbles.

5. The method of claim 4, wherein the at least one generator has a generally disc shape formation formed about a central axis and comprises axially spaced apart first and second planar faces and a plurality of atomizers for generating ultrafine bubbles.

6. The method of claim 5, wherein the atomizers are symmetrically distributed within the generator about the central axis of the generator.

7. The method of claim 5 or 6, wherein each atomizer comprises primary and secondary ports opening out of the atomizer, respectively, at the generator’s first and second planar faces.

8. The method of any one of claims 5 to 7, wherein the generator comprises a hollow opening formed along the central axis that opens out at generator’s first and second planar faces.

9. The method of claim 8, wherein each atomizer comprises an inlet that opens out into the generator’s opening.

10. The method of claim 9, wherein the inlet comprises an elongated, possibly oval, shape formed along an axis that is generally parallel to the central axis of the generator.

11. The method of claim 7, wherein the generator comprises a plurality of inserts located each above a primary port of a respective one of the atomizers for communicating an aeration gas, e.g. oxygen and / or ozone, towards such primary ports.

12. The method of claim 11, wherein the generator comprises a peripheral support located above the generator’s first planar face for holding in place the plurality of inserts.

13. The method of any one of claims 5 to 12, wherein the generator being formed from two segments and at least certain elements forming each atomizer being formed on interior sides of each one of the segments.

14. The method of claim 13, wherein each atomizer comprises a swirl chamber being divided into two primary and secondary sections being formed each within a different segment of the generator.

15. The method of claim any one of claims 5 to 14, wherein the at least one generator is located within the wastewater.

16. The method of claim 4, wherein the at least one generator is located outside of the wastewater.

17. The method of claim 16, wherein the at least one generator comprises an outer housing and a cone-shaped structure located within the housing, and wastewater flowing through the generator initially flows along an outer side of the cone-shaped structure and then through a passage formed through the cone-shaped structure.

18. The method of claim 17, wherein the cone-shaped structure is oriented in an inverted manner within the housing with its wider open end positioned at the top.

19. The method of claim 18 and comprising a bulge extending downwards from an upper side of the housing towards the upper open side of the cone-shaped structure.

20. The method of any one of claims 17 to 19 and comprising a spiral rib formed around an outer periphery of the cone-shaped structure in order to guide incoming wastewater to generally flow along a path it defines in a swirling motion.

21. An auxiliary system for reducing hydrogen sulfide levels in wastewater flowing through a pumping station of a sewerage system, the auxiliary system comprises:a recirculation loop for redirecting part of the wastewater flowing through the pumping station back towards a reservoir chamber of the pumping station, and at least one ultrafine bubble system for introducing ultrafine bubbles comprising an aeration gas into the wastewater flowing through the pumping station, wherein the at least one ultrafine bubble system is located along the recirculation loop and / or in association with the reservoir chamber of the pumping station.

22. The auxiliary system of claim 21 and comprising an operational tank located along the recirculation loop and the at least one ultrafine bubble system is associated with the operational tank.

23. The auxiliary system of claim 21 or 22, wherein the aeration gas comprises oxygen and / or ozone.

24. The auxiliary system of any one claims 21 to 23, wherein the at least one ultrafine bubble system comprises at least one generator for generating the ultrafine bubbles.

25. The auxiliary system of claim 24, wherein the at least one generator has a generally disc shape formation formed about a central axis and comprises axially spaced apart first and second planar faces and a plurality of atomizers for generating ultrafine bubbles.

26. The auxiliary system of claim 25, wherein the atomizers are symmetrically distributed within the generator about the central axis of the generator.

27. The auxiliary system of claim 25 or 26, wherein each atomizer comprises primary and secondary ports opening out of the atomizer, respectively, at the generator’s first and second planar faces.

28. The auxiliary system of any one of claims 25 to 27, wherein the generator comprises a hollow opening formed along the central axis that opens out at generator’s first and second planar faces.

29. The auxiliary system of claim 28, wherein each atomizer comprises an inlet that opens out into the generator’s opening.

30. The auxiliary system of claim 29, wherein the inlet in a cross section comprises an elongated, possibly oval, shape formed along an axis that is generally parallel to the central axis of the generator.

31. The auxiliary system of claim 27, wherein the generator comprises a plurality of inserts located each above a primary port of a respective one of the atomizers for communicating an aeration gas, e.g. oxygen and / or ozone, towards such primary ports.

32. The auxiliary system of claim 31, wherein the generator comprises a peripheral support located above the generator’s first planar face for holding in place the plurality of inserts.

33. The auxiliary system of any one of claims 25 to 32, wherein the generator being formed from two segments and at least certain elements forming each atomizer being formed on interior sides of each one of the segments.

34. The auxiliary system of claim 33, wherein each atomizer comprises a swirl chamber being divided into two primary and secondary sections being formed each within a different segment of the generator.

35. The auxiliary system of claim any one of claims 25 to 34, wherein the at least one generator is located within the wastewater.

36. The auxiliary system of claim 24, wherein the at least one generator is located outside of the wastewater.

37. The auxiliary system of claim 36, wherein the at least one generator comprises an outer housing and a cone-shaped structure located within the housing, and wastewater flowing through the generator initially flows along an outer side of the cone-shaped structure and then through a passage formed through the cone-shaped structure.

38. The auxiliary system of claim 37, wherein the cone-shaped structure is oriented in an inverted manner within the housing with its wider open end positioned at the top.

39. The auxiliary system of claim 38 and comprising a bulge extending downwards from an upper side of the housing towards the upper open side of the cone-shaped structure.

40. The auxiliary system of any one of claims 37 to 39 and comprising a spiral rib formed around an outer periphery of the cone-shaped structure in order to guide incoming wastewater to generally flow along a path it defines in a swirling motion.

41. A generator for generating ultrafine bubbles for a variety of nano-bubble enhanced processes, the generator having a generally disc shape formation formed about a central axis and comprises axially spaced apart first and second planar faces and a plurality of atomizers for generating ultrafine bubbles.

42. The generator of claim 41, wherein the atomizers are symmetrically distributed within the generator about the central axis of the generator.

43. The generator of claim 41 or 42, wherein each atomizer comprises primary and secondary ports opening out of the atomizer, respectively, at the generator’s first and second planar faces.

44. The generator of any one of claims 41 to 43 and comprising sa hollow opening formed along the central axis that opens out at generator’s first and second planar faces.

45. The generator of claim 44, wherein each atomizer comprises an inlet that opens out into the generator’s opening.

46. The generator of claim 45, wherein the inlet comprises an elongated, possibly oval, shape formed along an axis that is generally parallel to the central axis of the generator.

47. The generator of claim 43 and comprising a plurality of inserts located each above a primary port of a respective one of the atomizers for communicating gaseous towards such primary ports.

48. The generator of claim 47 and comprising a peripheral support located above the generator’s first planar face for holding in place the plurality of inserts.

49. The generator of any one of claims 41 to 48 and being formed from two segments and at least certain elements forming each atomizer being formed on interior sides of each one of the segments.

50. The generator of claim 49, wherein each atomizer comprises a swirl chamber being divided into two primary and secondary sections being formed each within a different segment of the generator.

51. A generator for generating ultrafine bubbles for a variety of nano-bubble enhanced processes, the generator comprising: an outer housing, a cone-shaped structure comprising an internal passage passing therethrough along the structure’s cone axis, wherein the cone-shaped structure being oriented in an inverted manner within the housing with its wider open end at the top.

52. The generator of claim 51 and comprising a bulge extending downwards from an upper side of the housing towards the upper open side of the cone-shaped structure.

53. The generator of claim 51 or 52 and comprising a spiral rib formed around an outer periphery of the cone-shaped structure for guiding incoming liquid to generally flow in a swirling motion along a path defined by the rib.

54. The generator of any one of claims 51 to 53 and comprising a main incoming tube leading into a lower side of the housing and an outlet tube for communicating liquid out of a lower side of the passage passing through the cone-shaped structure.

55. The generator of claim 54 and comprising an inlet tube merging into the incoming tube and a throat located along the incoming tube just before the point where the inlet tube merges into the incoming tube.

56. The generator of claim 54, wherein liquid flowing through the throat is adapted to increase its velocity while decreasing in pressure (according to Bernoulli's principle).

57. The generator of claim 55 or 56, wherein the incoming tube comprises an internal diameter Ø1 and the outlet tube comprises an internal diameter Ø2 that is sized to be larger than Ø1, for example according to Ø2 being about 1.5 to 2 times Ø1.

Images