Abstract:
A system for separating waste materials from a flowing stream of surface water comprises a vertical cylindrical vessel and a vertical structure within the cylindrical vessel. The vertical structure comprises stacked filtering elements and weirs sized to accommodate normal and increased fluid flow for abnormally high surface water flow conditions. The flowing stream containing waste material under normal flow conditions enters the vessel and passes through a filtering wall portion in a lower section of the vertical structure and exits through and effluent pipe. Under higher flow conditions the water flows through an overflow structure mounted on top of a lower cylindrical structure The over flow structure comprises one or more upwardly extending filtering structures and weirs sized to accommodate the excess flow conditions, filter at least a portion of the waste material from said excess flow and direct such excess flow to the effluent pipe.

Description:
This application claims benefit of U.S. Provisional Application 61/525,650 filed Aug. 19, 2011. 
    
    
     FIELD OF INVENTION 
     The present invention relates to a hydrodynamic separator unit designed to separate solid matter from a surface water fluid stream flowing into and through the unit in both normal and abnormally high fluid flow conditions. 
     BACKGROUND 
     One example of a prior art hydrodynamic separator is shown in U.S. Pat. No. 5,788,848 patent. This patent shows a system comprising inner and an outer non-concentric cylinders, the inner cylinder including a screen portion (the screened separator). The debris containing stream is feed to the internal space within the inner cylindrical screened separator; the material contained therein is retained within and below the inner cylinder while the fluid flows from the inside of the inner screened cylinder to an annular space between the inner and outer cylinder and exits from the surrounding outer chamber. 
     U.S. Pat. No. 6,241,881 discloses a similar cylindrical waste separator which includes on its upper portion an inlet for loaded influent and an outlet for cleaned effluent. The separator comprises a cylindrical portion having a lower part incorporating a basket. The inflow stream containing solid matter flows in a rotary motion to the area inside the cylindrical portion above the basket. The solid matter of a size greater than that of the mesh openings in the basket are retained within the cylinder and in the basket at the lower end of the cylinder and the fluid with solid matter smaller than the mesh openings, referred to as cleaned effluent, passes outward through the basket and cylinder walls. Cleaned effluent entering the peripheral area surrounding the basket and cylinder then flows upwards into the outlet pipe. 
     These arrangement have the disadvantage of clogging as a result of retained waste material, such as plastic bags, bottles, leaves, etc, that can accumulate against the inner walls of the screen causing the swirling, inflowing stream to penetrate the only the upper portion of the screen which, in turn, causes the inflowing stream to flow only through the upper portion of the basket. Bulky waste obstructing the basket walls thus reduces the flow capacity of liquid passing through the basket and the efficiency of separation and the inflowing stream tends to bypass the separator and flow directly to the outlet through an overflow weir. 
     U.S. Pat. No. 6,641,720, shows a separator which has a plurality of protruding segments adjacent openings in the panel, with each segment extending from the face of the panel at a position upstream of respective openings so as to project into the fluid flow path to form a substantially closed face to the liquid flowing over the screen, the intent being to prevent blockage of the openings in the screen. 
     An alternative hydrodynamic separator for urban and industrial effluents, shown in EP Published application 2,181,748, incorporated herein in its entirety by reference, includes a tank having a centrally located cylindrical chamber, the cylindrical chamber having a tubular screen made of expanded or perforated metal within the space defined by the cylindrical chamber. In these separators, fluid flowing into the separator circulates in the tank in a space exterior to the cylindrical chamber. Waste is constrained in a cyclone-like vortex that forms in the tank but outside the screened cylinder and moves downwards to the bottom of the tank while cleaned fluid flows through the lateral surface of an expanded metal screen of the cylinder and exits from the bottom of the centrally located screened chamber. 
     The rotation of the effluent stream in the periphery helps avoid the deposition of waste or particles on the screen so that the screen remains unobstructed. 
     SUMMARY 
     A unit for separating particulate matter and solid waste, particularly large sized particles in a flowing stream of surface water includes a cylindrical filter structure onto which the effluent stream flows. The filter structure separates solid wastes of specific dimensions which cannot pass through the filter structure from the cleaned stream which flows through the filter to a downstream outlet chamber from which the effluent stream cleaned from the retained solid waste is discharged. Solid waste particles smaller in size than the apertures of the screen cylinder may also be captured through swirl concentration, vortex separation and particle sedimentation processes inherent under flow conditions. The filter structure consists of a screen, which is designed to be traversed by the flowing stream, an inlet chamber and an outlet chamber, which are both contained in a tank. Solid waste of large dimensions, which cannot pass through the filter structure, is collected at the bottom of the inlet chamber. The separator unit further includes structure on the top thereof designed to redirect excess fluid flow that exceeds the design capacity of the separator. This internal bypass structure is, comprised of a combination of additional filter structures and weirs, to filter and direct the bypass of very large flows that exceed the design capacity of the primary filter screen cylinder. This bypass structure provides screening treatment of the large bypass flows and baffling retention of floating solids. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a vertical axial cross-section and 
         FIG. 2  is a horizontal cross-section showing the hydrodynamic separator described in EP 2,181,748. 
         FIG. 3  is a vertical axial cutaway view of a separator incorporating features of the invention. 
         FIG. 4  is an enlarged view of the portion of  FIG. 3  enclosed by circle B of  FIG. 3 . 
         FIG. 5  is a top view of the separator taken along line  5 - 5  of  FIG. 3 . 
         FIG. 6  is a schematic drawing showing the left side of the bypass system as shown in  FIG. 4  and the flow paths of fluid during a high flow situation through that left side. 
         FIG. 7  is a vertical, cutaway perspective view of the separator of  FIG. 3  prior to placement of the overflow structure. 
         FIG. 8  is a top view of the separator taken along line  8 - 8  of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
     Described and shown herein is a hydrodynamic separator for separating solid matter from a stream of liquid surface water such as urban and industrial storm water runoff containing waste material. Such a structure is typically used to separate debris in an inflowing stream before a finer treatment process can be applied to the flowing stream. The separator  10 , shown in  FIGS. 3-6  includes an upper extension  12 , referred to herein as the Quad Bypass Tower. This construction is an improvement over the prior art structures such as shown in  FIGS. 1 and 2 . 
     Referring to  FIG. 1 , baffle  333  comprises a solid walled, hollow cylinder mounted on top of a primary screen cylinder  332 , which can be an expanded, perforated, punched, slotted or otherwise made porous to provide a screen material. The elevation of the top of this cylinder is set so there is about 1 to 2-ft of freeboard above the expected water surface elevation of the flow over the bypass weir  344  that is in the separate diversion vault  340 . The diversion weir structure shown in  FIGS. 1 and 2  incorporates an overflow weir plate  344 . Under normal flow conditions, this weir plate diverts flow into the tank  300 . However in case of high flows, a portion of the flow passes over the overflow weir  344  and is directly discharged to the discharge chamber  349  and then to the effluent drain  350  without being filtered. 
     The separator consists of a hydrodynamic volume limited by a tank provided with an inlet for a waste containing influent stream and an outlet for the effluent stream with large particles removed. 
     To achieve the separation, the separator is divided into an inlet chamber and an outlet chamber, by a screen designed to retain large particles which accumulate in front of the screen or at the bottom of the separator. Clearing of the screen is achieved through the circulating movement of the effluent stream inside the separator. Cleaned effluents flow through the screen and are discharged at the outlet, without cluttering the screen. 
     The expanded, perforated, punched or slotted screen has a smooth metal separation surface of, for example, stainless steel with openings there through. The surface of the screen is installed vertically inside the tank. 
     The stream of effluent flowing along the separation surface induces a circular motion in the stream and waste of larger size, i.e. heavy solids is carried towards the center in a circular motion to descend to the bottom of the separator below the screen. Solid waste particles of smaller size than the apertures of the screen cylinder can also be captured along with the larger particles through swirl concentration, vortex separation and sedimentation. 
       FIGS. 7 and 8  show a hydrodynamic separator  10 , similar to that shown in  FIGS. 1 and 2 , prior to inclusion of the upper extension  12  and incorporating features of the invention. A primary difference over  FIGS. 1 and 2  of the hydrodynamic separator of 
       FIGS. 7 and 8  is that the top of the solid walled cylindrical partition baffle  133  is configured for addition of the upper extension  12  (Quad Bypass Tower), shown in  FIG. 3  and best shown in  FIG. 4 . The upper extension  12  allows large flows to bypass the separation/screening chamber, such as illustrated in  FIG. 6 , while still receiving screening and baffling treatment. In  FIGS. 1 and 2 , high flows will bypass over a weir  344  that is located in a separate structure upstream of the separator  10 , and these bypass flows would receive no screening or baffling treatment. The Quad Bypass Tower  12  allows the hydrodynamic separator  10  to be placed directly in the pipeline alignment and directly in the flow path without the separate upstream weir structure that is required for proper operation of the prior art structure, which diverts high flow rates around the unit. 
     Large installations, such as municipal installations, require a separate structure for diversion of treatment flows. On the other hand, the Quad Bypass Tower  12  is appropriate for installation in areas with moderate to small flow and with defined size drainage areas. The Bypass Tower  12  allows such an installation to accommodate the projected flows from a 25, 50 or 100-yr storm event. 
     Referring to  FIGS. 1 ,  2 ,  7  and  8  the separator consists of a cylindrical treatment tank  300 ,  100  of circular cross section having a partition baffle  330 ,  130  of cylindrical shape centrally mounted within the volume of the treatment tank  300 , 100 . The partition baffles  330 ,  130  comprise a solid walled lower portion  334 ,  134 , a separation screen  332 ,  132  of a cylindrical shape on top of the lower portion, and a solid walled cylindrical partition baffle  333 ,  133  on top of the separation screen  332 ,  132  enclosing an inner channel  320 ,  120 . 
     The assembly that is formed by the lower part  334 ,  134 , the screen  332 ,  132 , and the upper part  333 ,  133  subdivides the treatment tank  300 ,  100  into an external inlet chamber  310 ,  110 , to receive loaded effluents, and an internal outlet chamber  320 ,  120 , from which cleaned effluents are discharged. The internal chamber  320 ,  120  is connected to the effluent drain through a pipe  321 ,  121  which opens from the bottom of internal chamber  320 ,  120 . The effluent drain pipe  321 ,  121  also functions as an outlet siphon minimizing the sedimentation of very fine, suspended particles in the filtered liquids that flowed through the screen  332 ,  132  from accumulating in this portion of the flow path. 
     The pipe  321 ,  121  opens to the bottom part of a discharge chamber  349 , which is located below the input channel  341 ,  141  through which flow is fed into the treatment tank  300 ,  100 . The influent stream containing waste material flows successively through the influent drain  341 ,  141  to the diversion weir box  340 , then tangentially to the tank  300 ,  100  as indicated by the arrows in  FIG. 2 . The influent stream then flows in a swirl inside the external chamber  310 ,  110  following the rotational direction indicated by the two arrows F 301 . As a result of the rotational flow, the waste in the influent stream is washed from the outer surface of screen  332 ,  132 . This allows the cleaned effluent to flow through the screen, leaving the macro-waste in the peripheral space outside the surface of the cylindrical screen, and the cleaned effluent subsequently drains through the internal chamber  320 ,  120 , and is discharge through the effluent drain  321 ,  121 . 
     The hydrodynamic separator is typically from about 0.3 to about 10 meters in diameter and from about 0.6 to 15 meters in height, respectively. The access hole  302  on the lid  301  of tank  300  provides access into the external cell  310 , and also to the exterior of screen  332 . 
     In the previous designs, such as in U.S. patent U.S. Pat. No. 6,241,881, the loaded influent stream flows to a space enclosed by the screen and is filtered by passing outward through the screen so that the removed solid material tends to fill the space interior of the cylindrical screen. In the current separator, the feed stream is fed to the outside of the screen and flow is around the outer surface of the screen with the inflowing stream passing through the screen to provide a filtered stream exiting from the space within the cylindrical screen. 
     Referring to  FIGS. 3 ,  4  and  6 , the following describes the screened, baffled and bypass flows in a unit that incorporates the Quad Bypass Tower exposed to high fluid flows. This enhancement enables the high fluid flows to bypass the main filter system while still being processed in a single manhole structure, making it more versatile than the currently available manhole units such as shown in  FIGS. 1 and 2  or inside to outside flow separators such as shown in the prior art described above. The flows referred to below are best shown in the  FIG. 6 . The hydraulic conditions of the screened flow through the Quad Bypass Tower are such that clogging is minimized. 
     The Quad Bypass Tower in a preferred embodiment comprises a first filtering structure screen  235 , preferably a metal screen, attached to a pedestal  202  on the top of the baffle  333 . Above the first filtering structure is a second filtering structure  240 , comprising, in a preferred embodiment, upwardly extending, spaced apart bars. In a further preferred embodiment these bars are arranged in a conical manner. Above the second filtering structure is a cylindrical vertical wall  222 , the cylindrical wall  222  functioning as a first weir so that excess fluid input flows over the top thereof. A cylindrical hanging baffle  224  with a diameter greater than the diameter of the cylindrical vertical wall  222  extends both above and below the top of cylindrical vertical wall  222 . The cylindrical hanging baffle  224  also functions as a weir with even greater excess input fluid flowing over the top thereof to accommodate extremely high bypass flow conditions. While the first filtering structure  235  and second filtering structure  240  are shown to be a metal screen and a bar screen, respectively, one skilled in the art will recognize that other alternative filtering structures can be utilized. The intent is to provide a filtering function to remove at least a portion of the waste material in an overflow situation while allowing the same or greater flow of a cleaned (i.e., less waste containing) stream through the filtering structures and into the centrally located outlet from the internal chamber  320 ,  120 . For example, any combination of screens, meshes, bars or porous flow barriers can be used. 
     If a high flow situation occurs a first bypass flow  200  passes through the first filtering structure (a perforated, punched, slotted or expanded metal screen)  235  mounted on the pedestal  202 . It functions as a non-blocking screen, like the primary separation screen  132  in the lower cylinder described above. 
     As flow increases a second bypass flow  210  passes through the second filtering structure (a bar screen)  240 . The bar screen  240  can comprise vertically oriented spaced apart bars but in a preferred arrangement they are oriented, as shown in the figures, configured as a cone. The second bypass flow  210  is intended to handle the greater amount of fluid as influent flow rate increases. Because the bar screen has a tendency to cause waste material to be pinned against its surface, this pinning tendency is mitigated by placing the bars at an incline downward angle in a conical configuration. With this configuration the trapped material tends to slide downward off the bar surface. 
     As the flow further increases a third bypass flow  220 , which is not screened, is allowed to spill over the top  223  of the cylindrical vertical wall  222  (functioning as a weir) and into the center of the internal chamber  120 . However, some waste obstruction is provided by the cylindrical hanging baffle  224  which retains floatables and also functions as another weir. 
     If very high flows are encountered bypass flow  230  occurs. The flow proceeds unfiltered upward external of, and then over, the top of the cylindrical hanging baffle  224  and into the internal chamber  120 . Under this flow condition, the first, second and third bypass flows  200 ,  210 ,  220  are at maximum flow and all the flow goes into the center of the internal chamber  120 . 
     The separator  10  may also be configured to include a discharge pipe (not shown) through the wall of the unit with its inlet positioned at an elevation equal to the top of the hanging baffle. The inclusion of this additional discharge pipe is dictated by hydraulic conditions and is intended to discharge fluid only in the most severe flow conditions which are far in excess of the normal design capacity of the separator  10 . 
     The various components of the system are sized in relationship to each other to have an acceptable flow through the system without any internal flow obstruction. Referring to  FIG. 4  (not drawn to be dimensionally accurate but to readily illustrate the features), the dimensions below are provided as examples of a first embodiment with a 24″ internal diameter inlet pipe, and are not intended as limitations on the scope of the disclosure. 
     Referring to  FIG. 6 : 
     
       
         
               
               
               
             
               
               
             
               
               
               
             
           
               
                   
               
             
             
               
                 d 0  = diameter (Φ) of Inlet Pipe 345, 
                 24 
                 in 
               
               
                 d 1  = diameter (Φ) of screen cylinder 235, 
                 20 
                 in 
               
               
                 d 2  = top diameter (Φ) of bar screen cylinder 240, 
                 28 
                 in. 
               
               
                 d 3  = diameter (Φ) of cylindrical hanging baffle 224, 
                 34 
                 in. 
               
               
                 h 1  = ,Height of screen cylinder 235, 
                 8 
                 in 
               
               
                 h 2  = Height of bar screen cylinder 240, 
                 8 
                 in 
               
               
                 h 3  = Height of cylindrical vertical wall 222, 
                 20 
                 in 
               
               
                 h 4  = Plunge depth of cylindrical vertical wall 222 
                 20 
                 in 
               
               
                 h 5  = Height of hanging baffle cylinder 224 
                 20 
                 in 
               
             
          
           
               
                 Open area of perforated, punched, slotted or expanded 
                 0.33%, 
               
               
                 Screen (α) 
               
               
                 Open area of Conical Bar Screen (β) 
                 0.5%, 
               
             
          
           
               
                 First Bypass Flowrate 200, (Q) 
                 10.15 
                 ft 3 /s 
               
               
                   
               
             
          
         
       
     
     Circumferential Weir Length of cylindrical Overflow Weir  222 , (L=π·d 2 ) 7.33-ft, 
     q=1.385(ft3/s)/ft,=Q/L, (Unit Weir Flow) 
     D c =0.390-ft, (q 2 /g) 1/3  (Critical Depth at Circular Overflow Weir)=4.7-in 
     H m =0.586-ft, 3/2·D c , Minimum Hydraulic Head above Circular Weir=7.0-in 
     One skilled in the art, based on the teachings herein can readily adjust these dimensions based on greater or lesser normal flow conditions and excess flows as may be projected for a 25, 50 and 100 year storm event and typify one possible set of dimensions for the Quad Bypass system. 
     One skilled in the art will recognize that the disclosure set forth herein is not limited to the specific embodiments shown or described herein. It should be further recognized that the bypass system described herein is not limited to outside-to-inside flow hydrodynamic separators but can be readily adapted for addition to the inside-to-outside flow structures shown in the prior art, for example as described above.