Abstract:
An internally fed drum filter for treating waste water, includes an inlet distribution arrangement for distributing waste water entering the drum filter via an inlet duct, characterized in that the inlet distribution arrangement includes an adjustable flow deflection member arranged near the outflow opening of the inlet duct, downstream thereof, for adjusting the flow characteristics of waste water entering the drum filter via the inlet duct.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to an in internally fed drum filter for treating waste water, comprising an inlet distribution arrangement for distributing waste water entering the drum filter via an inlet duct. 
       BACKGROUND OF THE INVENTION 
       [0002]    The first step in the treatment of waste water is the removal of coarse solids, such as chunks of hard soil, in order to prevent these solids from damaging piping or other equipment further on in the treatment process. The removal of solids is for example effected by placing screens in the waste water stream to be treated, or by installing cloth filters. Another method of removing these solids is by feeding the waste water into a so-called internally fed drum filter. 
         [0003]    The use of internally fed drum filters for separating solid substances from fluids is known from for example U.S. Pat. No. 3,275,150, which describes a rotary drum filter for the thickening of e.g. fluids as used in the manufacturing of paper. The described apparatus comprises a drum revolving in a tank containing e.g. paper pulp stock. The fluid is drained away and thickened paper slurry is processed further to produce paper. When treating waste water the opposite is true, i.e. that the fluid is processed further whereas the solid substances are removed. 
         [0004]    Another internally fed drum filter is known from WO2011161327. This publication describes a process for treating waste water comprising organic material, such as waste water originating from a food industry plant, wherein waste water is led through a first purification phase comprising a drum screen, for separating the coarsest solid debris from the waste water. 
         [0005]    An internally fed drum filter generally comprises a water-permeable drum that is rotatable in a casing and an inlet duct that discharges e.g. waste water inside the drum filter. The inner surface of the drum filter is provided with a spiral that due to rotation of the drum enables solid substances present in the waste water to be pushed towards the end of the drum filter opposing the inlet duct end in order to be removed. At the same time the permeability of the drum enables water to leave the drum filter via the circular drum wall for receiving further treatment. 
         [0006]    However, a disadvantage is that the inlet areas of these drum filters are prone to clogging. Therefore, it has been proposed in the prior art to incorporate an inlet distributor into the filter design. These inlet distributors are generally of the “headbox” type. A headbox is a type of shallow water reservoir connected to the inlet pipe, that allows waste water to flow over the edges of the reservoir, whereas the solid substances remain in the reservoir to be discharged evenly to the drum filter via the bottom of the reservoir. 
         [0007]    These headbox type inlet distributors have several disadvantages. A first disadvantage is that debris may build up inside the reservoir, causing the headbox itself to clog. Another disadvantage is that foul water may be retained in the reservoir, especially during low supply rates of waste water via the inlet duct, causing fouling of the reservoir and causing it to generate a rather unpleasant smell. A further disadvantage is that the flow characteristics of the flow of waste water entering the drum filter via the inlet duct can not be adjusted, e.g. the flow velocity of the incoming waste water can not be regulated in any way. 
         [0008]    Therefore, it is an object of the invention to provide an inlet distribution arrangement for an internally fed drum filter, wherein the flow characteristics of the waste water entering the drum filter via the inlet duct can be adjusted. 
       SUMMARY OF THE INVENTION 
       [0009]    This object is achieved by providing an internally fed drum filter, wherein the inlet distribution arrangement comprises an adjustable flow deflection member arranged near the outflow opening of the inlet duct, downstream thereof, for adjusting the flow characteristics of waste water entering the drum filter via the inlet duct. 
         [0010]    The adjustable deflection member allows control of the flow characteristics of the waste water entering the drum filter via the inlet duct. Especially flow velocity and direction can be adjusted with the help of the deflection member. The absence of a headbox furthermore prevents the stalling of foul, smelly waste water, or clogging of the headbox. 
         [0011]    An embodiment relates to a drum filter, wherein the orientation and/or position of the flow deflection member can be adjusted in such a way, that the flow deflection member is upwardly inclined. By putting the flow deflection member in an upwardly inclined direction it is prevented that the waste water and solid substances present therein primarily collect below the outflow opening of the inlet duct. 
         [0012]    A further embodiment relates to a drum filter, wherein the angle of an upwardly inclined flow deflection member with respect to the plane coinciding with the outflow opening can be adjusted within the range of 40°-85°, corresponding to a range of 5°-50° with respect to the centre line of the inlet duct, when the plane of the outflow opening is perpendicular to the centre line. In practice, such an angle yields an optimal result with respect to preventing collection of substances below the outflow opening. 
         [0013]    Another embodiment concerns a drum filter, wherein an end of the flow deflection member is hingeably connected to a lower part of the circumference of the outflow opening. The lower part of the circumference is very suitable for hingeably connecting the flow deflection member, because the flow deflection member can be rotated into and out of the incoming waste water stream relatively easily. Furthermore, the efficiency of the flow deflection member is increased, since the waste water will have a natural tendency to ‘fall’ onto the flow deflection member, due to gravity. 
         [0014]    A further advantageous embodiment comprises a drum filter, wherein the orientation and/or position of the flow deflection member can be adjusted in such a way, that the incoming flow is essentially divided into two flows directed at the sides of the drum filter. An even better distribution of incoming waste water over the drum filter surface is achieved by doing so. 
         [0015]    Another embodiment relates to a drum filter wherein the flow deflection member has a bent or curved flow deflection surface in a plane perpendicular to a longitudinal direction of the flow deflection member, wherein the convex side of the bent or curved surface is facing the outflow opening. The curved or bent surface aids in deflecting the incoming flow in the desired directions. 
         [0016]    A further embodiment concerns a drum filter wherein the flow deflection member is a plate. A plate is relatively easy to deform in order to give the flow deflection member the desired flow deflection characteristics. 
         [0017]    In a preferred embodiment the deflection member has a V-shaped cross-section resulting in the deflection member to have a sharp edge and two flanges connecting in the sharp edge, wherein the sharp edge of the V-shaped section substantially faces the outflow opening. Such a V-shaped member is very efficient for directing the incoming flow sideways. In this respect, “flange” means a substantially flat shape suitable for deflecting the incoming flow. 
         [0018]    Adjustment of the flow deflection member can be achieved by moving one or more actuators connected to the deflection member, wherein the one or more actuators can be activated by being connected to activation means situated outside the inlet end of the drum filter. Thus, the deflection member can be operated from outside the drum filter by the activation means, preventing the activation means from being exposed to the waste water. 
         [0019]    In a further embodiment the one or more actuators are substantially arranged close to the underside of the inlet duct and extend parallel thereto. Thus, the one or more actuators are minimally exposed to incoming waste water, preventing wear of the actuators while allowing them to effectively control the position and/or orientation of the flow deflection member. 
         [0020]    The one or more actuators preferably comprise a rod and/or a thread. Such a rod or thread has a very high mechanical reliability in hostile environments such as the inside of a drum filter for treating waste water. Compressive or tensile forces can also be easily transmitted to the deflection member for changing its position and/or orientation. For providing optimal control of the flow deflection member, a plurality of rods and/or threads is preferably used, the rods and/or threads being attached to different locations on the flow deflection member. 
         [0021]    An embodiment relates to a drum filter, wherein the acute angle of the flanges of the V-shaped member is 80°-160°, preferably around 120°. Thus, an optimal flow distribution towards the sides of the drum filter is achieved. 
         [0022]    In practice, an even better flow distribution is achieved by providing a drum filter, wherein the flange width of the V-shaped deflection member increases along the length thereof (also known as “tapering”). This increase of flange width in length direction may relate to both directions, i.e. an increase in one direction or an increase in the opposite direction may be desired depending on the required flow characteristics. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    An embodiment of a drum filter according to the invention will by way of non-limiting example be described in detail with reference to the accompanying drawings. In the drawings: 
           [0024]      FIG. 1  shows a schematic side view of the internally fed drum filter according to the invention, 
           [0025]      FIG. 2  shows a close-up side view of the inlet distribution arrangement according to the invention, 
           [0026]      FIGS. 3   a - 3   c  show various possible shapes for the V-shaped flow deflection member, and 
           [0027]      FIG. 3   d  shows a cross-section of the flow deflection member. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0028]      FIG. 1  shows an internally fed drum filter  1  in side view. The cylindrical, rotatable drum itself is not shown to increase clarity. The left part of  FIG. 1  shows an inlet duct  2  for supplying waste water to be treated by the drum filter  1  to the inside of the drum cylinder. In the lower part of  FIG. 1  an inclined collection tray  17  for collecting filtered waste water is shown. The degree of inclination has been chosen such that filtered waste water flows toward the filtered waste water discharge  6 . The collection tray  17  is supported by a support frame  8 , which can be any suitable kind of frame. The right part of  FIG. 1  shows a solid substance discharge  7  for removing filtered-out solid substances from the drum filter  1 . The inside of the drum cylinder is provided with a helicoid  10  for facilitating the transport of solid substances towards the solid substance discharge  7  when the drum rotates. Above the drum cylinder a brush  4  is situated for brushing solid particles out of the relatively small filtering holes of the drum cylinder in order to keep the drum cylinder water-permeable. Furthermore, a drive motor  5  is shown for rotating the drum cylinder. To the right of the outflow opening of the inlet duct  2  the inlet distribution arrangement  3  according to the invention is shown, comprising the adjustable flow deflection member  12 . The functioning of the inlet distribution arrangement  3  will be explained further with reference to  FIG. 2 . 
         [0029]    When waste water to be treated enters the drum filter  1  via the inlet duct  2  it flows onto the flow deflection member  3 , which alters the characteristics of the incoming flow, such that an improved distribution of the waste water, and especially solid substances present therein, over the drum cylinder is achieved. 
         [0030]      FIG. 2  shows a close-up view of the inlet distribution arrangement  3  comprising the flow deflection member  12  according to the invention. The flow deflection member  12  is connected to the underside of the inlet duct  2  by means of a hinge  16 , that allows rotation of the flow deflection member  12  from and towards the outflow opening  11  of the inlet duct  2 . This rotation can be effected by displacing an actuating rod  15  connected to a flange of the flow deflection member  12  from left to right and vice versa. To this end activation means (not shown) are to be positioned outside the drum cylinder, i.e. left of the separation wall  18 . The rod  15  projects through this separation wall  18 . Although a single rod  15  is discussed here, multiple rods, threads or similar force transmission means can be used. The rod  15  can be conveniently positioned just below the inlet duct  2  and parallel thereto. The rod  15  can furthermore be supported by an intermediate rod support  19  arranged on the underside of the inlet duct  2 . Thus, the rod  15  is shielded as much as possible from the waste water flowing out of the outflow opening  11 . Operation of the rod  15  can be achieved in an automated fashion, for example by using electric, hydraulic or pneumatic activation means. The activation means preferably automatically adapt the angle of the flow deflection member  12 , for example based on the water level in the drum filter  1 . The rod  15  can also be provided with a screw thread, such that it is moveable in a length direction by rotation thereof, the rotating movement being provided by the activation means. 
         [0031]    The flow deflection member  12  preferably has a V-shaped cross-section. The flow deflection member  12  (thus) has a sharp edge  13  at the intersection of two flanges  14 . The sharp edge  13  is preferably turned towards the outflow opening, the sharp edge  13  splitting or diverting the incoming flow along its length into two flows directed towards the internal surface of the drum cylinder for obtaining a better flow distribution. The rotational angle of the sharp edge  13  of the flow deflection member  12  with respect to the plane coinciding with the outflow opening  11  preferably lies within the range of 40°-85°, corresponding to a range of 5°-50° with respect to the centre line of the inlet duct  2  (as shown in  FIG. 2 ), when the plane of the outflow opening  11  is perpendicular to the centre line. Other rotational angles are also conceivable, since a preferred range of angles is shown in  FIG. 2 . 
         [0032]      FIGS. 3   a - 3   c  show various possible shapes for the V-shaped flow deflection member.  FIG. 3   a  shows a top view of a first shape wherein the width of the flanges  14  increases along the length of the flow deflection member  12 . In contrast thereto,  FIG. 3   c  shows a decrease of flange  14  width in the same direction (i.e. an increase in opposite direction). The lower part of  FIG. 3   a  shows that (the projection of) the flange end sides, when viewed from above, can be put under an angle with respect to each other if desired.  FIG. 3   d  shows a cross-section of the V-shaped flow deflection member  12 . The acute angle of the flanges  14 , i.e. the angle between the ‘legs’ of the V-shape, preferably lies within the range of 80°-160°, more preferably is around 120°. 
         [0033]    Thus, the invention has been described by reference to the embodiment discussed above. It will be recognized that this embodiment is susceptible to various modifications and alternative forms well known to those of skill in the art without departing from the spirit and scope of the invention. Accordingly, although a specific embodiment has been described, this is an example only and is not limiting upon the scope of the invention. 
       REFERENCE NUMERALS 
       [0034]      1 . Internally fed drum filter 
         [0035]      2 . Inlet duct 
         [0036]      3 . Flow distribution arrangement 
         [0037]      4 . Brush 
         [0038]      5 . Drive motor 
         [0039]      6 . Filtered waste water discharge 
         [0040]      7 . Solid substance discharge 
         [0041]      8 . Support frame 
         [0042]      9 . (Drum) 
         [0043]      10 . Helicoid 
         [0044]      11 . Outflow opening 
         [0045]      12 . V-shaped flow deflection member 
         [0046]      13 . Sharp edge 
         [0047]      14 . Flange 
         [0048]      15 . Actuator rod 
         [0049]      16 . Hinge 
         [0050]      17 . Water collection tray 
         [0051]      18 . Separation wall 
         [0052]      19 . Rod support