Abstract:
An aeration device adapted for the introduction of gas into a liquid medium is provided, including an elongated primary distribution member with a proximal end adapted to be connected to a gas source and a distal end adapted to be immersed into the medium. Additionally, at least one aeration member is connected to the primary distribution member at a location on the distribution member spaced from the proximal end thereof and being in fluid communication with the distribution member, adapted for bringing the gas into a state entrappable within the liquid medium. Also, a flotation member is provided, mounted onto the primary distribution member and adapted to assume various positions along the distribution member according to the level of the liquid medium. An aeration system is also provided, the system including an array of aeration devices as described above.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to aeration devices, particularly to devices adapted to be inserted into a liquid medium for the introduction therein of a gas. 
       BACKGROUND OF THE INVENTION 
       [0002]    Known in the art are devices adapted to infuse air into basins of water and other fluid materials, this infusion being generally referred to as aeration. The aeration may be performed for different purposes. For example, such purposes include improving the growth of a fish population and providing better conditions for fish breeding in fish ponds, treatment of sludge, etc. 
         [0003]    One type of aeration device is usually in the form of a piping network deployed over a basin and having pipe extensions lowered below the water level in the basin to provide air thereto. 
         [0004]    Another type of aeration device is usually in the form of fans deployed on the surface of the water of the basin, and adapted to rotate while emitting air so as to provide the desired infusion. 
       SUMMARY OF THE INVENTION 
       [0005]    According to one aspect of the present invention there is provided an aeration device adapted for the introduction of gas into a liquid medium, said device comprising:
       an elongated primary distribution member having a proximal end adapted to be connected to a gas source and a distal end adapted to be immersed into said medium;   at least one aeration member connected to the primary distribution member at a location on said distribution member spaced from said proximal end thereof, being in fluid communication with the distribution member and being adapted for bringing said gas into a state entrappable within said liquid medium; and   a flotation member mounted onto said primary distribution member and adapted to assume various positions along said distribution member between said proximal end and said location at which the aeration member is connected to the distribution member, according to the level of the liquid medium.       
 
         [0009]    The connection between said at least one aeration member and the primary distribution member may be in the form of at least one corresponding auxiliary distribution member where one end thereof is connected to the primary distribution member at said location and the other end thereof holds said aeration member. 
         [0010]    The primary distribution member may be formed as an essentially hollow mast having a main axis, where said mast may be made of a non-permeable material, i.e. any suitable metal such as steel, plastic, etc. The proximal end of said mast may be formed with an attachment port connectable to a gas feed line adapted to introduce said gas into said mast. The distal end of said mast may be provided with a plurality of outlet ports distributed around the main axis, oriented transversely thereto, circumferentially spaced from each other. Each outlet port is adapted for connection thereto of at least one of the auxiliary distribution members. The outlet ports may be formed integrally with the mast, or the mast may have at its distal end a distribution hub formed with said outlet ports. 
         [0011]    The auxiliary distribution members may be formed as rods which are also essentially hollow and have an inlet end and an outlet end. The rod may be adapted for mounting onto the mast by inserting the inlet end thereof into one of said outlet ports such that when mounted, the rod extends essentially perpendicular to the mast, i.e. radially with respect to the main axis thereof. 
         [0012]    The outlet end of each auxiliary distribution member may be formed integrally with, or have mounted thereon, said aeration member. The aeration member may be adapted to produce bubbles from said gas, for the aeration of said medium. Thus, the aeration member may be in the form of a bubble generator such as a diffuser, adapted to transform the gas introduced thereto into a plurality of bubbles. 
         [0013]    The diffuser may be so designed as to allow control over the average bubble size. The bubble size is defined by the average diameter of the bubbles and may be, for example, coarse, e.g. about 5-7 mm, or fine, e.g. about 1 mm. Coarse bubbles may be used for aeration of a liquid in a slurry form whereas fine bubbles may be used for aeration of regular liquids. 
         [0014]    In addition, different diffusers may be used providing the aeration device with a wide range of aerating capacities. Furthermore, Variable Frequency Drive (VFD) may be used allowing adjustment of the capacity of air introduced into the water. 
         [0015]    The floatation member may be made of a material adapted to float on the liquid medium, i.e. having a lower specific weight than said liquid. Alternatively, the floatation member may be formed as an essentially hollow body with air or any other gas contained therein and adapted to facilitate floatation of the entire device. According to a specific embodiment, the hollow body may be in the form of a disc, the diameter of which corresponds to the length of the mast for optimal floatation stability thereof. 
         [0016]    The device may further comprise an anchoring assembly attached to the proximal end of said primary distribution member and adapted for suspending the device above the liquid medium level, by connection of the assembly to an anchoring line extending across the medium. Alternatively, the device may be suspended from a crane-like assembly. Suspension may be used in a variety of situations, e.g. prior to lowering of the device into the water, during cleaning or draining of the pool, for cleaning of the device, etc. 
         [0017]    The anchoring assembly and anchoring line may also be used to position the device at a desired location across the medium. Thus, for example, the device may be displaced along the anchoring line until it reaches a desired position above the liquid medium, and may then be detached from the anchoring line and dropped into the liquid. 
         [0018]    The device may further comprise support elements extending from the distal end thereof and adapted to prevent impact of the primary distribution member and/or auxiliary distribution members with the bottom surface of a basin in which the liquid medium is disposed. The support elements may be in the faun of legs made of any appropriate material, e.g. steel, and may be equipped with cushion fittings adapted to prevent excessive impact on the device when coming in contact with the basin floor. Soft impact of the aeration device with the basin floor may also prevent damage to the basin floor. 
         [0019]    The gas feed line may be made of a light weight material which may be adapted to float on the surface of the liquid medium. For example, it may be made of High Density Polyethylene (HDPE). The gas feed line is adapted to be connected to the device throughout a working process thereof, in order to provide a constant supply of gas, for example oxygen, thereto. In operation, the gas source begins pumping gas through the gas feed line into the primary distribution member, wherefrom it is supplied via auxiliary distribution members to the aeration members, which then transform the gas into bubbles of desired size and emit said bubbles into the liquid medium. 
         [0020]    In a normal position, when the level of liquid in the basin is relatively high, the floatation member is positioned at the top of the primary distribution member, i.e. adjacent its proximal end, and the device is suspended therefrom into the liquid medium. In this position, said support elements are disposed above the bottom surface of the basin. When the level of the liquid medium drops, the entire device is displaced downwards as well, until the support elements encounter the bottom surface of the basin. Once the support elements are positioned on the bottom surface of the basin, further lowering of the liquid level will cause the floatation member to be displaced downwards along the primary distribution member. This allows the aeration device to maintain its desired orientation with the aeration members being in an essentially horizontal position. 
         [0021]    This is opposed to common aeration devices known in the art in which the floatation member is fixed, where when the liquid level drops, the floating member may appear to be held above this level. Thus, the floatation member may turn into a counterweight which, due to its high wind resistance, may act as a ‘sail’ and tilt the entire aeration device and even tip it over. 
         [0022]    It would also be appreciated that the aeration device according to the present invention may be particularly useful in cases where the basin floor is uneven, e.g. resulting from construction quality. The aeration device may also be useful in cases where the level of the basin floor tends to change due to collection of sludge or solids. 
         [0023]    According to another aspect of the present invention, there is provided a system comprising an array of aeration devices as described above, in each of which the location of their floating members along the primary distribution member is individually adjustable. 
         [0024]    It should be noted here that according to a specific design variation, the formation of the aeration members and/or their or the auxiliary distribution members&#39; articulation to the primary distribution member may be such as to cause the bubbles to perform a rotary motion about the main axis of the primary distribution member, thereby to facilitate aeration and penetration of gas bubbles into the liquid, and better mixing capacity of the basin. 
         [0025]    Another advantage of the aeration device according to the present invention lies in the fact that it comprises no moving parts within the water during operation thereof. This provides infusion of a considerable amount of oxygen into the medium of the basin, while maintaining an essentially low power consumption of the aeration device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which: 
           [0027]      FIG. 1  is a schematic isometric view of one example of an aeration device according to the present invention; 
           [0028]      FIG. 2A  is a schematic view of an anchor holding the device shown in  FIG. 1  suspended therefrom, in accordance with one embodiment of the present invention; 
           [0029]      FIG. 2B  is a schematic view of an alternative anchoring arrangement according to another embodiment of the present invention; 
           [0030]      FIG. 3A  is a schematic view of the device shown in  FIG. 1  in its position within a liquid medium, whose level exceeds the entire length of the device; 
           [0031]      FIG. 3B  is a schematic view of the device shown in  FIG. 1  in its position within a liquid medium, whose level is equal to the length of the device; 
           [0032]      FIG. 3C  is a schematic view of the device shown in  FIG. 1  in its position within a liquid medium, whose level is lower than the length of the device; and 
           [0033]      FIG. 4  is a schematic view of an array of aeration devices shown in  FIG. 1  in a basin having an undulated bottom surface. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0034]      FIG. 1  shows an aeration device generally designated at  10 , adapted for introducing oxygen into a liquid medium (shown in  FIGS. 2-4 ). 
         [0035]    The aeration device  10  comprises an elongated primary distribution member  20  having a proximal end  20   a  and a distal end  20   b , a distribution assembly  30  attached to the distal end  20   b  of the primary distribution member  20 , a floatation member  40  mounted on the primary distributor  20 , and an anchoring member  50  attached to the proximal end  20   a  of the primary distribution member  20 . 
         [0036]    The primary distribution member  20  is an essentially hollow cylindrical mast of a diameter of about 2-3″, and having an axis X-X and formed at its proximal end  20   a  with an attachment port  24  adapted for the attachment thereto of a oxygen feed line  60 , shown in  FIGS. 2 to 4 , and a distribution port  26  which is threaded in order to mount thereon the distribution assembly  30 . The mast  22  may be made of a variety of impermeable materials, for example steel, plastic etc. 
         [0037]    The distribution assembly  30  comprises a plurality of auxiliary distribution members  34  each having a proximal end  34   a  and a distal end  34   b , and a central distribution hub  32  to which the members  34  are attached at their proximal ends  34   a . The auxiliary distribution members  34  are in the form of radially extending hollow arms which are in fluid communication with the mast  20  via the hub  32 . The auxiliary distribution members  34  extend radially with respect to the axis X-X and are equally angularly spaced from each other. 
         [0038]    Each of the auxiliary distribution members  34  is fitted at its distal end  34   b  with an aeration member  38  which has an inlet port  38   a  in fluid communication with the interior of the distribution member  34 . In this case, each aeration member  38  is in the form of a tubular diffuser adapted for transforming oxygen entering its inlet port  38   a  into a plurality of bubbles of a predetermined size and discharging these bubbles through a membrane jacket of the diffuser. An example of such a diffuser may be the Airflex™ Tube Diffuser 2. 
         [0039]    For example, fine bubbles may be about 1 mm, in which case the diffuser may have a diameter of about 6.5 cm, and coarse bubbles may be 5-7 mm in which case the diffuser may have a diameter of about 9.4 cm. Coarse bubbles may be used for aeration of a liquid in a slurry form whereas fine bubbles may be used for aeration of regular liquids. 
         [0040]    The device  10  further comprises a set of legs  35  projecting axially and outwardly from the auxiliary distribution members  34  and adapted to prevent the diffusers  38  from impacting a solid surface (not shown in  FIG. 1 ) above which the device is to be used (e.g. the bottom of a basin in which the liquid medium to be aerated is disposed). Each leg  35  is fitted with a cushioning pad  37  adapted to avoid damage to the basin liner and the device  10 , in the case that such an impact occurs. 
         [0041]    The floatation member  40  is formed with a central bore  44  adapted to let the mast  22  freely pass therethrough. The floatation member  40  is in the form of a cylinder of a diameter of about 1.3 m filled with air, and having sufficient buoyancy so as to keep the entire device floating on the surface of the liquid to be aerated, when the floatation member is in its uppermost position on the mast  20 . The floatation member  40  also employs polymeric agent to block water entrance when damaged, as known per se. 
         [0042]    The anchoring member  50  is attached to the proximal end  20   a  of the mast  20  and is adapted to facilitate suspension of the device  10  by any suitable means. The anchoring member  50  has a dimension in the direction perpendicular to the axis X-X which is greater than the maximal dimension of the bore  44 , allowing the anchoring member  50  to serve as a stopper for the floatation member  40 , preventing the latter from detachment from the mast  22 . 
         [0043]    In assembly, the floatation member  40  is mounted on the mast  22  in a free manner to be able to be displaced along the mast  22 . Thereafter, the distribution hub  32  with auxiliary distribution members  34  mounted thereon is mounted onto the distal end  20   b  of the mast  22  and the aeration members  38  are attached to each of the auxiliary distribution members  34  such that the aeration members  38  extend radially outwards relative to the main axis of the mast  22 . Next, the aeration device  10  is attached to an oxygen feed line  60  and the anchoring member  50  is attached to the proximal end  20   a  of the mast  22 . 
         [0044]    Turning to  FIG. 2A , the aeration device  10  is shown before operation, suspended over a basin  100  having an uneven basin bed  104  and containing water  102  having a surface  101 . A crane  70  is positioned on the basin bank  106  with its crane arm  72  reaching out across the basin  100 . The crane arm  72  is equipped with a hook  74  to which the anchoring member  50  of the device  10  is attached. An oxygen feed line  60  is attached to the attachment port  24  of the mast  22  (see  FIG. 1 ) to connect the mast to an oxygen source  62  (not shown in  FIG. 2 ), positioned on the bank  106 . The crane arm  72  is adapted to bring the device  10  to a desired location over the basin  100 . Once in position, the device  10  is detached from the hook  74  and plummets into the water  102 . 
         [0045]    Turning to  FIG. 3A , the device  10  is shown floating in the water  102 . The floatation member  40  causes the device  10  to be suspended above the bottom surface  104 , leaving the distribution assembly  30  completely submerged in the water  102 . The depth L 1  of the water is greater than the length D of the device  10  such that the legs  37  do not touch the bottom surface  104  of the basin  100 . 
         [0046]    Turning to  FIG. 3B , when the water level drops to L 2 =D, the device  10  rests on the legs  37 , the floatation member  40  being still positioned at the top of the mast  22 , enabling vertical orientation of the mast. 
         [0047]    Turning to  FIG. 3C , when the water level drops to L 3 &lt;D, the legs  37  continue abutting the bottom surface  104 , whilst the floatation member  40  is displaced downwardly along the mast  22 . Consequently, the mast  22  continues to be maintained in its vertical orientation due to the floatation member  40 , which would not be the case if the floatation member were fixed on the mast, in which case the floatation member would have been suspended above the water level, causing the aeration device to tip over and malfunction. 
         [0048]    It should be noted that according to the above described example, once the device  10  is positioned within the basin  100 , it is attached only to the oxygen feed line  60 , eliminating the need for a large, bulky and expensive infrastructural construction over the basin  100  to support the device  10  in a suspended state. Since the oxygen feed line  60  is made of a light material, as mentioned above, it may float on the water  102 , thus avoiding the need to suspend it above the basin  100 . 
         [0049]    In operation, the device  10  receives oxygen from the oxygen source  62  through the oxygen feed line  60  attached to the mast  20 , through which oxygen is transferred, via the arms  34 , to the aeration members  38 , from which the oxygen is emitted into the water  102  in the form of oxygen bubbles  12 . During operation of the aeration device  10 , the emission of the bubbles from auxiliary distribution assembly  30  causes turbulence of the water around the mast  22 , facilitating better infusion of the air within the water  102  of the basin  100 . 
         [0050]    With reference to  FIG. 2B , an example is shown in which the crane  70  is substituted with a cable assembly  80  comprising anchoring masts  82  positioned on the basin bank  106 , and a guiding cable  84  extending therebetween at a height smaller than the distance between the proximal end  20   a  and the floating member&#39;s upper surface  42   a.    
         [0051]    According to this example, the device  10  is anchored to the cable  84  by its anchoring member  50  and is displaced along the cable  84 , for example in a ferry-like manner, until it reaches a desired location across the basin  100 . Once the desired position has been reached, the device  10  is released from the cable  84  and remains there and begins its operation. This construction also proves to be easy to set up and cost efficient, requiring only the anchoring masts  82  and the guiding cable  84 . 
         [0052]    Referring to  FIG. 4 , an aeration system  110  is shown comprising an array of the devices  10  as described above, positioned at spaced apart locations in a basin  120  having such a topography of its bottom surface  140  that water level L at these locations is different. As shown, in view of the different water level L, all the devices have different positions of their floatation members  40  along the masts  20 . 
         [0053]    Those skilled in the art to which this invention pertains will readily appreciate that numerous changes, variations, and modifications can be made without departing from the scope of the invention, mutatis mutandis.