Patent Publication Number: US-2021171367-A1

Title: A Wastewater Treatment Device

Description:
TECHNICAL FIELD 
     This invention relates to a wastewater treatment device. 
     BACKGROUND 
     Wastewater such as that arriving at a sewage treatment facility can contain, among other things, fat, oil, grease and grit (FOGG) which may damage processing equipment and lead to a loss of performance. 
     A separator for the removal of grit from wastewater flow is described in U.S. Pat. No. 6,645,382. The separator comprises a tray assembly made up of a plurality of stacked settling plates, in the form of trays having a frusto-conical shape. Each tray has a centrally located opening and a lip which extends about the periphery of the tray and projects inwardly. The trays are spaced apart axially so that wastewater may flow between the trays. The stacked trays are submerged in a vessel, such as a grit basin. An influent duct channels wastewater in between the trays and ensures that the wastewater is distributed evenly across the tray stack. The influent duct is arranged to provide a tangential inlet such that a low energy vortex flow is established between adjacent trays. The low energy vortex allows grit particles entrained by the flow to settle on the sloping inner surface of each tray whereupon the particles gravitate towards and pass through the openings in the trays. The grit falls through the openings in underlying trays and out through the bottom of the tray assembly. The grit collects at the bottom of the separator from where it is removed as a concentrate. De-gritted wastewater flows out over the lips of the trays into the grit basin for further processing. 
     However, operating and maintaining the separator is a difficult, expensive, time-consuming and resource-intensive process. It is therefore desirable to provide a wastewater treatment device which is easier to operate and maintain. 
     SUMMARY 
     In accordance with a first aspect of the invention, there is provided a wastewater treatment device comprising: a vessel comprising an inlet for receiving an influent stream; a separator disposed within the vessel; a grit pot connected to the separator; a level sensor; one or more fluidizing nozzles; an extraction outlet; and a controller. The level sensor is configured to output a signal indicative of the level of grit within the grit pot. The one or more fluidizing nozzles are disposed within the grit pot and configured to deliver a jet of fluid from a fluid supply to fluidize grit accumulated on the lower surface of the grit pot. The extraction outlet is connected to a pump for extracting grit fluidized by the fluidizing nozzles. The controller is in communication with the level sensor. The controller and the pump are configured to activate the fluidizing nozzles based on the signal received from the level sensor. 
     The controller may be configured to activate the fluidizing nozzles when the signal is indicative of the level of grit within the grit pot being above a first predetermined threshold level. 
     The controller may be configured to activate the pump after a predetermined period of time has elapsed from activating the fluidizing nozzles. 
     The controller may be configured to deactivate the fluidizing nozzles and/or the pump when the signal is indicative of the level of grit within the grit pot being below a second predetermined threshold level. 
     The level sensor and/or the extraction outlet may be disposed within the grit pot. 
     A plurality of fluidizing nozzles may be provided which may be spaced around a circumference of the grit pot. 
     The plurality of spray nozzles may be connected to a ring manifold. 
     The fluidizing nozzles may be directed towards a center of the grit pot. 
     The fluidizing nozzles may be angled towards a lower surface of the grit pot. 
     The or each spray nozzle may be a flat-fan spray nozzle. 
     The extraction outlet may be located at or adjacent a center of the grit pot and above a lower surface of the grit pot. 
     In accordance with a second aspect of the invention, there is provided a wastewater treatment device comprising: a vessel comprising an inlet for receiving an influent stream; a separator disposed within the vessel; a grit pot connected to the separator; a level sensor; and a support. The level sensor is configured to sense the level of grit within the grit pot. The support extends into the grit pot from outside of the grit pot. The level sensor is movably connected to the support and is movable along the support between an operating position in which the level sensor is positioned within the grit pot and a maintenance position in which the level sensor is positioned outside of the grit pot so as to be accessible by a user. 
     The support may be an elongate member extending between the grit pot and an exterior of the vessel. The level sensor may be movable along a channel formed in the elongate member. 
     The support may be a support cable extending between the grit pot and an exterior of the vessel. The level sensor may be movable along the support cable. 
     The level sensor may be coupled to an actuation cable for moving the level sensor along the support. 
     The support may be provided with a pulley which supports the actuation cable. 
     The cable may be coupled to a motor for moving the level sensor along the support. 
     The level sensor may be coupled to a flexible rod for moving the level sensor along the support. 
     The separator may comprise a tray assembly connected to the inlet. The tray assembly may comprise a plurality of nested tray units which define a separator axis and are spaced apart from one another along the separator axis. Each tray unit may comprise: a substantially conical tray which is aligned along the separator axis; and an aperture in the tray disposed at the separator axis and in communication with the grit pot. 
     For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective sectional view of a separator according to an embodiment of the invention; 
         FIG. 2  is a sectional view of the separator shown in  FIG. 1 ; 
         FIG. 3  is a sectional view of the separator shown in  FIG. 1  taken in a direction perpendicular to that of  FIG. 2 ; 
         FIG. 4  is a close-up sectional view of a grit pot of the separator shown in  FIG. 1 ; 
         FIG. 5  is a sectional plan view of the grit pot of  FIG. 4 ; 
         FIG. 6  is a close-up plan view of a nozzle shown in  FIG. 5 ; 
         FIG. 7  is a close-up sectional view of a nozzle of the grit pot of  FIG. 4 ; 
         FIG. 8  is a perspective view of a first mechanism for removing a level sensor; 
         FIG. 9  is a perspective view of a second mechanism for removing the level sensor; and 
         FIG. 10  is a perspective semi-transparent view of a separator according to another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a separator  2  comprising a tray assembly  4  disposed within a treatment vessel  6 . The tray assembly  4  comprises a plurality of nested tray units  14 . Five tray units  14  are shown in  FIG. 1 , but it will be appreciated that the tray assembly could comprise more or fewer tray units  14 . The nested tray units  14  define a separator axis  16 , shown in  FIGS. 2 and 3 , which is upright and preferably substantially vertical. The tray units  14  are spaced apart from each other along the axis  16 . The treatment vessel  6  is provided with an inlet chute  8  and a fluids outlet  12 . 
     Each tray unit  14  comprises a frusto-conical tray  18 , having a circular aperture  20  at the apex of the tray  18 . The axis of the conical shape of the tray  18  is aligned with the separator axis  16 . The tray  18  converges in a downward direction. A cylindrical rim  24  extends upwardly from the outer periphery of the tray  18  and an annular lip  26  extends radially inwardly from the extremity of the rim  24 . The radially inward portion of the annular lip  26  is inclined so as to be parallel to the direction of the upper surface of the tray  18 . The rim  24  and annular lip  26  may be formed integrally with the tray  18  by a folded over portion of the tray  18 . The rim  24  and annular lip  26  can be separately manufactured and assembled with the tray  18 , or can be formed integrally with the tray  18 , for example, when the tray is a plastics molding. 
     Referring to  FIGS. 2 and 3 , the inlet chute  8  has a single inlet  30  and a plurality of outlets  32 . The chute  8  extends into the treatment vessel  6  through an outer wall of the treatment vessel  6  and is in direct communication with the tray assembly  4 . The mid-portion of the chute  8  is inclined in a downward direction from the inlet  30  to the outlets  32 . The mid-portion of the chute  8  diverges in a vertical direction from the inlet  30  towards the outlets  32 . The outlets  32  are aligned vertically and extend from the lower end of the mid-portion of the chute in a horizontal direction. Each of the outlets  32  is in direct communication with a respective tray unit  14  and arranged tangentially with respect to the separator axis  16  (shown in  FIGS. 3 and 4 ). In particular, the outlets  32  are in direct communication with the region between the annular lip  26  and the upper surface of the tray  18 . 
     A plate  34 , provided with a funnel section  36 , is disposed within the base of the treatment vessel  6 . The plate  34  extends horizontally across the extent of the vessel  6  and the funnel section  36  converges in a downward direction. A grit pot  10  is provided in the lower region of the funnel section  36  and forms a sump for collecting grit at the base of the vessel  6 . The funnel section  36  is arranged coaxially with the separator axis  16 . 
     As shown best in  FIG. 4 , an extraction tube  37  extends through a wall of the grit pot  10  into the interior of the grit pot  10 . The end of the extraction tube  37  has a bell mouth opening which increases in diameter towards its distal end and which forms a grit outlet  39  for extracting grit from the grit pot  10 . The extraction tube  37  extends horizontally through the wall of the grit pot  10  and has a corner section adjacent the grit outlet  39  which transitions from horizontal to vertical such that the grit outlet  39  is directed downwards towards a lower surface  41  of the grit pot  10 . The grit outlet  39  is positioned at the center of the grit pot  10  at the separator axis  16 . As shown in  FIG. 1 , the other end of the extraction tube  37  is connected to a pump  43  which provides a suction force at the grit outlet  39  to remove grit from the grit pot  10 . 
     A level sensor  28  is disposed within the grit pot  10  adjacent the center of the grit pot  10  and the separator axis  16 . The level sensor  28  is supported by a support  31  which passes through an upper surface  27  of the separator  2 , and extends downwards through the circular apertures  20  and into the grit pot  10 . The level sensor  28  is configured to output a signal which is representative of the level of grit within the grit pot  10 . 
     A fluidizing apparatus  42  is disposed within the grit pot  10  and spaced from the lower surface  41  of the grit pot  10 . The fluidizing apparatus  42  comprises a plurality of spray nozzles  22  which are spaced around an inner surface of a ring manifold  38 . 
     As shown in  FIG. 5 , the ring manifold  38  is formed by a pipe which is formed into a circle having a diameter which is less than that of an inner surface of the grit pot  10 . The ring manifold  38  thus extends around a periphery of the interior of the grit pot  10 . The manifold  38  carries five spray nozzles  22 , which are equally spaced around the circumference of the manifold  38 . The spray nozzles  22  extend inwards from the manifold  38  towards the center of the manifold  38 . The spray nozzles  22  are flat-fan nozzles which have a spray angle of approximately 65 degrees. 
     As shown in  FIG. 6 , the spray nozzles are angled in the same direction at approximately 50 degrees from the tangent of the manifold  38 . 
     Further, as shown in  FIG. 7 , the spray nozzles  22  are angled downwards, towards the lower surface  41  of the grit pot  10  at an angle of approximately 5 degrees. 
     The manifold  38  is connected to a fluid supply and distributes the fluid to the spray nozzles  22  when in use. The fluid may be a liquid, such as water, or a gas, such as air. The fluid supply may be connected to the manifold  38  via a solenoid valve (not shown), which allows the spray nozzles  22  to be selectively actuated. Each spray nozzle  22  may instead have its own dedicated fluid supply. 
     The output from the level sensor  28  is supplied to a controller (not shown). The controller is in communication with the pump  43  and the solenoid valve of the fluidizing apparatus  42 . As described in further detail below, the controller is configured to activate and deactivate the extraction pump  43  and the fluidizing apparatus based on the level of grit in the grit pot  10  as indicated by the output of the level sensor  28 . 
     The separator  2  may be part of a waste water treatment installation, and its function may be to separate fat, oil, grease and grit from a flow of waste water prior to further treatment processes. 
     During use, the treatment vessel  6  is flooded so that the tray assembly  4  is submerged. An influent mixture containing grit and grease entrained by water is supplied though the chute inlet  30  and flows downwardly along the chute  8  and through the outlets  32  into respective tray units  14 . The tangential arrangement of the outlets  32  causes the mixture to circulate within the tray units  14  about the separator axis  16 . 
     The circulating flow is a relatively low energy flow which allows the entrained grit to settle on the upper surfaces of the trays  18 . The sloped upper surface of each tray  18  causes the grit to gravitate towards the aperture  20  in the tray  18 . The grit falls through the aperture  20 . The grit settles on the upper surface of the underlying tray  18  and gravitates towards and through the aperture  20  of the underlying tray  18 . The grit passes through the apertures  20  of the underlying trays  18  until it is expelled from the bottom of the tray assembly  4 , where it is collected by the funnel section  36  and fed into the grit pot  10 . 
     The water from which grit is removed circulates within the tray units  14 . As the de-gritted water circulates within each tray unit  14  it flows upwardly over the annular lip  26  and over the rim  24  into the outer region of the treatment vessel  6 . The annular lips  26  thus help to retain grit which has collected on the surface of each tray  18  within the tray units  14 . De-gritted water which collects in the vessel  6  overflows through the outlet  12  which forms an overflow weir. 
     The level sensor  28  outputs a signal representative of the level of grit within the grit pot  10  to the controller. The controller uses the signal to determine whether the level of grit within the grit pot  10  exceeds a first predetermined value. If the level of grit within the grit pot  10  is determined to exceed the first predetermined value, the spray nozzles  22  are activated by the controller by activating the solenoid valve. This fluidizes the grit that has collected within the grit pot  10 . As described previously, the plurality of spray nozzles  22  are angled towards the center of the manifold and downwards towards the lower surface of the grit pot  10 . Consequently, the fluidizing apparatus creates a circulating flow within the grit pot  10  which acts to move grit towards the center of the grit pot  10  and the location of the grit outlet  39 . The angle of the spray nozzles  22  and their spray (fan) angle is selected to ensure that the fluid can fluidize grit collected on the entire lower surface of the grit pot  10 . The type, location and orientation of the nozzles  22  enables them to effectively mobilize material whilst minimizing water (or other fluid) usage. Since the arrangement of nozzles  22  provides an evenly distributed flow, the creation of tunnels through the material and pockets of grit that cannot be evacuated are avoided. This allows the system to be effectively used with large grit pots. 
     The controller may activate the pump  43  after a predetermined period of time following the activation of the fluidizing apparatus  42 . As mentioned previously, when the pump  43  is activated, it provides a suction force at the grit outlet  39 . This causes the fluidized grit contained within the grit pot  10  to be sucked out of the grit pot  10 , through the grit outlet  39  and along the extraction tube  37 , thus evacuating the grit pot  10  of fluidized grit. 
     The level sensor  28  continues to output a signal representative of the level of grit within the grit pot  10  to the control system. When the level of grit within the grit pot  10  is determined to be below a second predetermined level, the fluidizing apparatus  42  and the pump  43  are deactivated by the controller. As the fluidizing apparatus  42  is only activated intermittently, the amount of water (or other fluid) required is minimized. Similarly, intermittent use of the pump  43  reduces the energy required to power the system (e.g. in operating a compressor). The fluidizing apparatus  42  and pump  43  may be deactivated at different times and one or both may be deactivated after a predetermined period of time rather than based on the level of grit sensed by the level sensor  28 . 
       FIG. 8  shows a first mechanism which may be used to withdraw the level sensor (not shown in this figure) from the treatment vessel  6  of the separator  2 . The mechanism comprises a hollow strut  131 , a pulley  144 , a cable  146  and an actuator (such as a motor, not shown). The hollow strut  131  forms an enclosed channel. The hollow strut  131  replaces the support  31  and, as per the support  31 , passes through an upper surface  27  of the separator  2 , downwards through the circular apertures  20  and into the grit pot  10 . The cable  146  loops over the pulley  144  and extends down the enclosed channel of the hollow strut  131 . The sensor is attached to the end of the cable  146  disposed within the hollow strut  131 . The other end of the cable  146  is attached to the actuator, which is able draw in or release the other end of the cable  146 . Accordingly, the actuator can be controlled so as to adjust the length of the cable  146  extending through the hollow strut  131 , and thus the height of the sensor within the treatment vessel  6 . 
     The actuator of the mechanism may therefore be controlled to deploy the sensor to an operating position, where it is positioned at a lower end of the hollow strut  131 , close to the lower surface of the grit pot  10 . In this position, the sensor is able to output a signal representative of the level of grit within the grit pot  10 . The actuator may also be used to withdraw the sensor for maintenance, repair or any other purpose. 
     In particular, the sensor may be drawn out of the upper end of the hollow strut  131  so as to provide access to the sensor. The mechanism may be configured such that the operating position is maintained consistently each time the sensor is withdrawn and deployed. This may be achieved by defining a stop position of the cable  146 , which may be a physical stop or visual indicator or other means. 
     In other embodiments, the strut  131  may form an open channel. For example, the strut may have a C-shaped or U-shaped profile along which the level sensor is movable. 
     In other embodiments, the actuator may be dispensed with and the cable  146  may be actuated manually so as to manually move the sensor from the operating position to the maintenance position. 
       FIG. 9  shows a second mechanism which may be used to withdraw the level sensor (numbered as  228  here). The second mechanism generally comprises a guide cable  231  and a flexible rod  246 . An upper end of the guide cable  231  is attached to a support  248  fixed to the upper surface  27  of the separator  2 . The lower end of the guide cable  231  is attached to the lower surface (not shown) of the grit pot  10 . The upper surface  27  of the separator  2  is provided with an opening  250  through which the guide cable  231  extends, and which is sufficiently large to allow the flexible rod  246  and sensor  229  to pass through. The sensor  228  is slidably connected to the guide cable  231  such that it is able to move from a lower position in which the sensor  228  is positioned close to the lower surface of the grit pot  10 , and an upper position in which the sensor  229  is positioned above the upper surface  27  of the separator  2 . 
     In use, the user may wish to deploy the sensor  228  to an operating position by pushing the sensor  228  along the guide cable  231  using the flexible rod  246  until the sensor  228  is positioned at a lower end of the guide cable  231 , close to the lower surface of the grit pot  10 . In this position, the sensor  228  is able to output a signal representative of the level of grit within the grit pot  10 . The sensor  228  can be subsequently retracted by pulling the sensor  228  from the operating position along the guide cable  231  using the flexible rod  246 , such that the sensor  228  is drawn out of the treatment vessel  6  through the opening  250 . In this position, the user is able to access the sensor  229  for maintenance. 
     Although it has been described that the sensor  229  is slidably connected to the guide cable  231 , in other embodiments, the guide cable  231  could be replaced by a tube or other conduit for the sensor  229  to pass along, as per the arrangement of  FIG. 8 . 
     The user may decide himself when to carry out maintenance on the level sensor. Alternatively, the user may be prompted by the separator  2  when it is necessary to carry out maintenance. For example, the level sensor could prompt the user to maintain the level sensor after a period of time has elapsed since the last maintenance event or based on the number of extraction (fluidizing) cycles performed or the amount of grit removed. This information may be provided by the controller. 
     It will be appreciated that the number and arrangement of spray nozzles  22  may differ from that shown and described above. In particular, the number, position and orientation of the spray nozzles  22  may be chosen based on the size of the grit pot  10 . In some arrangements, it may be desirable for the jets from the nozzles  22  to overlap. For smaller grit pots  10 , a single spray nozzle  22  may be sufficient to fluidize grit collected on the entire lower surface of the grit pot  10 . 
     It has been described that the separator comprises a tray assembly disposed within a treatment vessel. However, the separator need not comprise a tray assembly and may instead comprise any form of assembly for the treatment of wastewater.  FIG. 10  shows an example of an alternative separator  102 . The separator  102  comprises a treatment vessel  106 , grit pot  110 , fluids outlet  112 , level sensor  128 , inlet  130 , support  131 , funnel section  136 , extraction tube  137 , fluidizing apparatus  142  and pump  143  which substantially correspond to the features described previously with respect to  FIGS. 1 to 9 . However, the separator  102  of  FIG. 10  does not feature a tray assembly  4  and instead comprises a central shaft  154  which is provided with a cone  156  at its distal end. The central shaft  154  is in the form of a cylindrical tube, and extends from an upper region of the vessel  106  towards a lower region of the vessel  106  along a separator axis  116 . The cone  156  extends from a lower end of the shaft  154  and defines a hollow frustroconical surface. Accordingly, a first passageway  158  is formed by and extends along the interior of the center shaft  154  and the center cone  156 . The level sensor  128  is disposed within the grit pot  110  adjacent the center of the grit pot  110  and the separator axis  116 . The level sensor  128  is supported by the support  131  which passes through the first passageway  158  and into the grit pot  110 . The separator  102  further comprises a dip plate  160  substantially in the form of a cylindrical tube. The dip plate  160  defines the fluids outlet  112 . The center shaft  154  is disposed centrally within the dip plate  160  such that a second passageway  162  having an annular profile extends around the center shaft  154 , from a lower portion of the dip plate  160  to the fluids outlet  112 . 
     In use, flow is introduced through the inlet  130 . The inlet  130  is positioned tangentially so as to cause a rotational flow around the treatment vessel  106  and the central shaft  154 . The flow spirals down the wall of the treatment vessel  106  as solids settle out by gravitational forces and forces created by the rotational flow. Grit contained within the flow collects in the grit pot  110 . The central cone  156  simultaneously directs flow away from the grit pot  110 , up and around the shaft  154  and within the inside of the dip plate  160  where it exits the vessel  106  via the fluids outlet  112 . The upward flow rotates at a slower velocity than the downward flow. The resulting “shear” zone scrubs out finer particles in the fluid. 
     The remaining operation of the alternative separator  102  corresponds to that of the separator  2  described previously with respect to  FIGS. 1 to 9 . The separator  102  may be used in conjunction with a mechanism as described with reference to  FIGS. 8 and 9  in order to withdraw the level sensor for maintenance, repair or any other purpose.