Abstract:
Improved settlement of solids is provided, while minimizing problems in collecting clarified liquid from a clarifier, by controlling the flow of clarified liquid from a given one of many flow channels of a clarifier. Such control is by causing a substantial amount of that flow of clarified liquid to be collected immediately as that flow exits the given flow channel. Such collection of the substantial amount, if not all of that flow of the clarified liquid from the given flow channel, minimizes if not eliminates, the mixing of the flow from all of the flow channels of a clairfier. As a result, during normal settling operations the flow of the clarified liquid from the given flow channel is substantially isolated. During such normal operations, the isolated flow may be separately sampled for examination of the performance of the separate flow channel. If too many solids are present in the clarified liquid from that separate flow channel then one or both of the plates that define that separate flow channel may be removed and replaced. Servicing operations of removal and replacement of the one or both plates are performed without interrupting the normal settling operations of the other flow channels.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to apparatus and methods for promoting settling of solids from waste water, and more particularly to supports for settler plates, wherein each support is provided with an integral outlet for clarified liquid flowing from an individual flow channel defined by adjacent settler plates. 
     2. Discussion of the Prior Art 
     Clarifiers (also known as “settlers”) are used to remove certain materials and particles from liquid. These materials are generally suspended in the liquid and can be removed under the force of gravity when the flow of the liquid is substantially reduced, as in a very low flow, or quiescent, zone (or flow channel) in the clarifier. Since these materials are generally solid and are said to “settle” out of the liquid, they are referred to as “settleable solids”. Such settleable solids may include naturally occurring materials (e.g., clay, silts, sand and dirt), chemical precipitants and biological solids. The word “solids” as used herein to describe the present invention refers to such settleable solids. 
     Clarifiers are used, for example, in water and waste water treatment plants. In water treatment, the water drawn from a water supply has various non-settleable colloidal solids therein. When mixed with chemicals, the colloidal solids and chemicals agglomerate to form solids. In waste water treatment, the solids include organic solids, among other wastes. Water and waste water are treated in clarifiers to remove such solids, thereby making the water clear and suitable for use, reuse, or for further treatment, such as tertiary treatment. The word “liquid” as used herein to describe the present invention refers to water and waste water. 
     An object of water and waste water clarifiers is to create quiescent zones having low flow rates to promote maximum settlement of solids to the bottom of the clarifiers. Clarifiers typically include a large detention basin where the settlement of the solids occurs. Tubes or flat plates mounted at fixed angles relative to the surface of the liquid have been used to form multiple thin liquid flow channels. For example, a support which may be in the form of a hollow pipe is connected to the top of one of the plates. Adjacent supports mount a pair of adjacent ones of such plates so that the adjacent plates define such a flow channel and create a quiescent zone within the detention basin in an attempt to promote settling of solids in less time using less space. The liquid containing the solids flows upwardly in the flow channels between the plates at flow rates that generally allow sufficient time for most of the solids to settle onto the plates or tubes. The hollow pipes are closed to the liquid and solids in the flow channels. Ideally, the solids then slide down the plates to the bottom of the detention basin for collection. After the solids have settled, the liquid without the settled solids is referred to as the “clarified liquid”. The clarified liquid flows upwardly past the adjacent hollow pipes and out of an open top of the flow channel defined by adjacent ones of the pipes. Such open top is between and at the top of the plates. Generally, the clarified liquid from each of the separate flow channels combines to form one or more common volumes of clarified liquid above the tops of the plates and above the hollow pipes. Thus, the clarified liquid from the separate flow channels commingles and mixes in the common volume(s). The common volume(s) of clarified liquid generally flows to an outlet at an end of the retention basin and exits the basin. 
     As an example, in U.S. Pat. No. 5,116,443 (issued in the name of Applicant), a hollow pipe having a rectangular cross-section is shown carrying rods that support the plates. Clarified liquid from between pairs of the plates flows together (i.e., commingles and mixes as described above) and exits the end of the basin via a trough. Because the hollow pipes are closed to the liquid and solids in the flow channels, the clarified liquid does not enter the pipes. Instead, the clarified liquid flows past and above the pipes into the and then flows to the trough. 
     As another example, in U.S. Pat. No. 4,865,753 (issued in the name of Applicant), a flap members is provided at the top of each flow channel and releasably closes the flow channel. As the flap releases, the clarified liquid from each flow channel flows past and above the respective flap, flows together, and then exits the basin via a trough. 
     In yet another example, in U.S. Pat. No. 5,378,378 (issued in the name of Applicant), clarified liquid from each of many flow channels flows out of the top of a clarifier section, flows together, and then exits the basin via an outlet. 
     As a further example, in U.S. Pat. Nos. 4,221,671 and 5,217,614 (issued in the name of Applicant), clarified liquid from each of many tubular flow channels flows out of the top of each of the tubes, then flows together, and then exits the basin via a trough. In the &#39;671 Patent, a perforated plate is placed over and spaced from the top of the tubes to define an overflow lauder. 
     As another example, in U.S. Pat. No. 5,391,306 (issued in the name of Applicant), a member is attached to the top of each of many clarifier plates to support the respective plate. Members supporting adjacent ones of the plates also control the flow of the clarified liquid from the flow channel defined by the adjacent plates. Although the members are shown as being hollow, the hollow members are closed to the liquid and solids. Therefore, the clarified liquid does not enter the members. Instead, the clarified liquid from one flow channel flows past and above the members of that flow channel, and joins clarified liquid flowing out of the other flow channels, and then the clarified liquid from all of the flow channels flows to an outlet of the basin. 
     An additional example is found in U.S. Pat. No. 4,136,012, wherein two clarifier outlet pipes are provided in a clarifier basin for use with over seventy tubes. Each tube defines one flow channel, such that over seventy flow channels are served by the two outlet pipes. The outlet pipes are above the tops of tubes (and thus above the tops of the clarifier flow channels) and do not support the tubes that define the flow channels. As a result, it appears that most, if not all, of the clarified liquid flowing from each tube joins together in a common volume, rises and flows into apertures formed in one or both of the two outlet pipes for flow to an outlet of the basin. 
     U.S. Pat. No. 4,889,624 shows a frame containing about twelve lamella plates that define separate flow channels of a clarifier. Each flow channel is defined by adjacent ones of the lammella plates. Tops of the plates are provided with legs that tend to close the upper end of each of the flow channels. To allow the clarified liquid to flow out of the flow channel, orifices are provided in the legs. The clarified liquid flowing out of one flow channel flows through the orifices of that channel, rises and and joins clarified liquid flowing out of the other flow channels. Then the clarified liquid from all of the flow channels flows over the edge of the frame to an outlet trough of the basin. It appears that a pressure drop exists across the legs, with a higher pressure being below the legs than the pressure above the legs. As a result, the higher pressure below the legs tends to lift the legs and must be counteracted by asdditional structure, such as bolts, to hold the plates down. 
     As a settling element in addition to adjacent plates, U.S. Pat. No. 3,963,624 shows multiple troughs adjacent to the tops of some but not all of many of the plates in a basin. As clarified liquid flows horizontally over the troughs, the troughs block any vertical flow of the liquid. With the vertical flow blocked, any entrained solids will drop out into the troughs so that the once-clarified liquid is further clarified as it flows toward a weir for exiting from the basin. 
     In these clarifiers, when clarified liquid exits the upper end of one particular flow channel, the clarified liquid from one flow channel generally joins with the clarified liquid from most, if not all of, the other channels. In most cases, there are at least tens of separate flow channels, such that the flow from tens of flow channels joins together and flows to an outlet trough, for example. 
     In the operation of many types of clarifiers, plates may become fouled when solids accumulate on the plates, for example. In such situations, it is necessary to remove the fouled clarifier plate. With the one plated removed, the two plates adjacent to the fouled plate cooperate to define a now-wider one of the flow channels. Problems result when a prior art plate of the type shown in U.S. Pat. No. 4,889,624 is removed. For example, without the removed plate and the legs at the top end of the removed plate, there is no leg to restrict the flow of the clarified liquid out of the top of the original flow channel. As a result, it is likely that there will be an increased flow rate of liquid and solids in the now-wider channel between the two remaining adjacent plates, less settling in that now-wider channel, less clarified liquid for a given inflow of solids, and thus more solids flowing out of the now-wider channel. The increased flow rate tends to disturb the flow rates in the other channels, such that the operation of the clarifier may have to be interrupted during repair of the plate. 
     In other types of clarifiers without such legs at the top of the flow channels, there would be the same flow rate of liquid and solids in the now-wider channel between the two remaining adjacent plates. However, because of the removal of the middle plate, the vertical settling distance between the two remaining settler plates is now twice the former vertical settling distance. Therefore, because the flow of the liquid in the now-wider flow channel is the same as before removal of the middle plate, less of the solids will move vertically downward onto the lower of the two remaining plates, and therefore less of the solids will settle. To avoid allowing the less clarified liquid from the now-wider flow channel to flow to the trough, the operation of the clarifier may have to be interrupted during repair of the removed plate. 
     Also, in many clarifiers, the support for a particular plate tends to block the upward flow of the clarified liquid. Such blockage results, for example, from the need to increase the size of the support to increase the strength of the support and prevent sagging of the support as it extends across the clarifier basin. Even when the sagging problem is overcome with a minimum of such blockage, the prior supports, the clarified liquid from different flow channels still combines in the space above the flow channels. 
     Therefore, what is needed is a separate support for each settler plate, wherein each separate support reduces the blockage of clarified liquid from a flow channel and not only carries the one settler plate, but is also provided with an integral inlet for receiving clarified liquid flowing from flow channels adjacent to the separate support, and preferrably, for receiving clarified liquid primarily from one individual flow channel defined in-part by the settler plate carried by the one separate support. 
     SUMMARY OF THE INVENTION 
     Applicant has studied prior clarifiers in an endeavor to improve the settlement of solids while minimizing the problems described above, and to overcome these long-felt problems by controlling the flow of clarified liquid from a given one of many flow channels of a clarifier. Such control may be by causing a substantial amount of that flow of clarified liquid to be collected immediately as that flow of the clarified liquid exits the given flow channel. Such collection of the substantial amount, if not all of that flow of the clarified liquid from the given flow channel, minimizes if not eliminates, the mixing of the flow from all of the flow channels of a clairfier. As a result, during normal settling operations the flow of the clarified liquid from the given flow channel is substantially isolated. During such normal operations, the isolated flow may, for example, be separately sampled for examination of the performance of the separate flow channel. If it is found that too many solids are present in the clarified liquid from that separate flow channel, for example, then one or both of the plates that define that separate flow channel may be removed and replaced. 
     Further, the servicing operations of removal and replacement of the one or both plates may be performed without interrupting or substantially impairing the normal settling operations of the other flow channels. In particular, even though there is a tendency for the same flow rate of liquid and solids to occur in the now-wider channel between the two remaining adjacent plates, the flow through that now-wider flow channel into the trough may be blocked during the servicing operation. With the flow to the trough blocked from the now-wider flow channel, in the present invention the only flow is from the open top of the now-wider flow channel into a separate support (e.g., pipe or trough) for each of the remaining settler plates. That flow into the separate supports is via integral inlets (or apertures) provided in each of the separate supports. The integral inlets permit receipt of the clarified liquid flowing from the now-wider flow channel. However, because the integral inlets are designed to receive the flow only from the original adjacent narrower flow channels, the flow from the now-wider flow channel is restricted, such that the flow into and in the now-wider flow channel is reduced. With the reduced flow rate in the flow channel there is an increase of the residency time of the liquid and solids in the now-wider flow channel. For example, if the now-wider flow channel is twice as wide and the flow rate is half as much, there will be a return to the original settling rate of the former narrow flow channel. As a result, there is an increase in the likelihood of being able to continue normal settling operation of the clarifier during the removal of the fouled settler plate. 
     One embodiment of the present method of removing the clarified liquid from the basin may utilize hollow support pipes that normally extend across the basin from a first trough mounted opposite to a second trough. Opposite ends of the hollow support pipes are supported on the opposite troughs. A settler plate is hung from each hollow support pipe in a standard manner. Two adjacent support pipes and the corresponding settler plates hung from the respective pipes define one flow channel. A central support pipe, two support pipes (one on each side of the central support pipes), the corresponding settler plates define two adjacent flow channels. This embodiment does not permit the clarified liquid from one of flow channels to join a common volume or flowpath of clarified liquid flowing out of other flow channels of the clarifier. Instead, in this embodiment many of the integral inlets are provided in the upper side of each hollow support pipe, and facing a given one of the flow channels adjacent to the central support pipe. In this embodiment, the level of the clarified liquid extends to but not over the top of the hollow support pipes. This level of the clarified liquid preferrably extends over these integral inlets facing the one flow channel. With these integral inlets and the described level of the liquid, substantially all, if not all, of the clarified liquid flowing out of the given one of the flow channels flows through the integral inlets of one of the two hollow support pipes (i.e., of the central support pipe having the inlets that face the given one of the flow channels. That clarified liquid flowing out of the given one of the flow channels is collected in that one central hollow support pipe. The collected clarified liquid flows along that one central hollow support pipe, through a trough inlet, and is discharged from the trough inlet into the trough for flow out of the basin. 
     A second embodiment of the present method of removing the clarified liquid from the basin may utilize the same hollow support pipes that normally extend across the basin from the first trough mounted opposite to the second trough. In the second embodiment, the level of the clarified liquid extends to and over the top of the hollow support pipes, thus extends over the integral inlets of the one central support pipe. With these integral inlets and the described higher level of the liquid, a primary amount of the clarified liquid flowing out of the given one of the flow channels flows through the integral inlets of the central hollow support pipe (i.e., through the inlets that face that given one of the flow channels. The primary amount is not less than half of the amount of the clarified liquid flowing out of the one flow channel. That primary amount is collected in that one central hollow support pipe. The remainder of the the clarified liquid flowing out of the one flow channel is referred to as a secondary amount and flows through the inlets of the two hollow support pipes that are adjacent to the central support pipe. In each case, the collected clarified liquid flows along the respective hollow support pipe, through a trough inlet associated with the respective pipe, and is discharged from the trough inlet into the trough for flow out of the basin. 
     In contrast to prior art clarifiers that are designed to allow the clarified liquid from all of the flow channels to mix and flow above the flow channels to a common outlet trough at one end of the basin, for example, the present invention contemplates providing a pipe or other hollow member for both supporting an individual clarifier plate and collecting the clarified liquid from a flow channel that is adjacent to the pipe and to the supported individual clarifier plate. 
     The present invention also contemplates providing methods of and apparatus for clarifying liquid, wherein the upward flow of clarified liquid in one clarifier flow channel is primarily collected in one of the pipes that is used to support the spaced plates that define the flow channel, and the remainder of that upward flow of clarified liquid in the one clarifier flow channel is secondarily collected in other ones of the pipes that are adjacent to the one pipe. 
     The present invention further contemplates servicing operations including removal and replacement of the one or both plates without interrupting or substantially impairing normal settling operations of the other flow channels. The flow through a now-wider flow channel into the trough may be blocked during the servicing operation by plugging up a trough inlet that is normally connected to a support pipe that carries the pipe that is to be removed for service. The removal forms a now-wider flow channel. With the flow to the trough blocked from the now-wider flow channel, in the present invention the only flow is from the open top of the now-wider flow channel into a separate support (e.g., pipe or trough) for each of the remaining settler plates. That flow into the separate supports is via integral inlets (or apertures) provided in each of the separate supports. The integral inlets permit receipt of the clarified liquid flowing from the now-wider flow channel. As described above, there is an increase in the likelihood of being able to continue normal settling operation of the clarifier during the removal of the fouled settler plate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, features and advantages of the present invention will be apparent from an examination of the following detailed descriptions, which include the attached drawings in which: 
     FIG. 1 is a perspective view of a clarifier basin showing hollow supports for clarifier plates. 
     FIG. 2A is an elevational view taken along line  2 A— 2 A in FIG. 1 showing the hollow supports having inlets for receiving clarified liquid. 
     FIG. 2B is an enlarged elevational view taken along line  2 B— 2 B in FIG. 2A showing the flow of liquid and solids from the bottom of the basin upwardly in the flow channels and into the hollow supports for flow in the hollow supports to the respective inlets and then to the outlet trough. 
     FIG. 3 is a plan view of a clarifier section showing the inlets in the hollow supports spaced along a longitudinal axis. 
     FIG. 4 is an elevational view taken along line  4 — 4  in FIG. 3 showing the hollow supports connected to respective inlets to an outlet trough for supplying clarified liquid from flow channels to the trough. 
     FIGS. 5A,  5 B, and  5 C are schematic elevational views respectively show a preferable, and more preferable, and a most preferable embodiment of the present invention in which the level of the clarified liquid is most preferably below the tops of the hollow supports, in which the level of the clarified liquid is more preferably about even with the tops of the hollow supports, and in which the level of the clarified liquid is preferably substantially above the top of the hollow supports. 
     FIG. 6 is a perspective view of a portion of FIG. 1 enlarged to show the inlets of the hollow supports, with the supports in the form of pipes. 
     FIG. 7 is a view showing the hollow supports connected to a bottom plate and to a cover plate of the trough for removably mounting the pipes on the trough. 
     FIG. 8 is a view taken along line  8 — 8  in FIG. 6 showing more details of the hollow supports connected to a bottom plate and to a cover plate of the trough for removably mounting the pipes on the trough. 
     FIGS. 9A and 9B are cross sectional views of two embodiments of the pipes that form the hollow supports. 
     FIGS. 10A,  10 B, and  10 C shows another embodiment of the hollow supports as a trough having either a generally V shape (FIGS. 10A and 10B) or a generally U-shape (FIG.  10 C). 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An invention is described for promoting settling of solids from waste water, and more particularly to providing supports for settler plates. The invention is described in terms of each support being provided with an integral outlet for clarified liquid flowing from an individual flow channel defined by adjacent settler plates. It will be obvious to one skilled in the art, that the present invention may be practiced without some or all of these specific details. In other instances well-known process operations or apparatus have not been described in detail in order not to obscure the present invention. 
     Clarifier  25   
     Referring to FIG. 1, a clarifier  25  is shown for removing materials such as solids  26  from liquid  27 . The clarifier  25  is shown including vertical outer walls  28  which define a detention basin  29  having an open top  30  and a bottom  31 . One embodiment of the clarifier  25  is shown in FIG.  1  and is referred to as a rectangular clarifier  25 A. The clarifier  25  may have other shapes, such as square or circular, and be used with the present invention. References to the clarifier  25  apply to all embodiments of the clarifier. 
     As the liquid  27  and the solids  26  flow through the detention basin  29  from an inlet  32  to outlets  33 , the flow of the liquid  27  and the solids  26  is substantially reduced according to the principles of the present invention to form many very low flow rate, or quiescent, zones or flow channels  34  in the clarifier  25 . The liquid  27  and the solids  26  flow upwardly (see liquid/solids flow arrows  27 A) in the quiescent zones  34  so that the solids  26  settle out of the liquid  27  and the resulting clarified liquid (represented by arrows  27 C), flows to the outlets  33  of the clarifier  25 . These outlets  33  may be in the form of openings from troughs  36 . 
     The detention basin  29  is divided into a number of sections  37 . Vertical internal partitions  38  define the center sections  37 . One partition  38  and one wall  28  define the outer sections  37 . One of the troughs  36  is preferably provided at the lateral side  36 A of each of the sections  37 . However, only one trough  36  may be provided for each section  37 , for example. 
     The liquid  27  and the solids  26  flow upwardly in the quiescent zones  34 . After the solids  26  settle out of the liquid  27 , the resulting clarified liquid  27 C flows to hollow supports  42  spaced along a longitudinal axis  43  of the basin  29 . Each of the hollow supports  42  carries one settler plate  44 . The settler plates  44  may be of any type, such as those described in Applicant&#39;s U.S. Pat. No. 5,391,306 issued Feb. 21, 1995 for Settler With Preset Outlet Area Deck and Variable Angle Removable Lamina and Method of Using Settler, the disclosure of which is incorporated herein by this reference. Adjacent ones of the hollow supports  42  carry respective adjacent ones of the the settler plates  44 . The adjacent settler plates  44  define one of the quiescent zones  34 . Opposite ends of each hollow support  42  are mounted on one of the troughs  36 . This mounting may be removable as described below. The described clarifier section  37  serves the function of containing the liquid  27  and the solids  26 . The described plates  44  serve the function of flow control extending across the clarifier section  3 , the flow control being performed by the plurality of separate flow control plates  44 . The described troughs  36  serve the function of mounting the plurality of flow control plates  44  in spaced relationship to each other for defining the separate clarifier channels  34  in which the liquid  27  flows to settle the solids  26  and provide the clarified liquid  27 C. 
     Flow of Clarified Liquid  27 C 
     FIG. 2A is an elevational view showing the two adjacent hollow supports  42  spaced along the longitudinal axis  43  of the basin  29 . Each of the adjacent hollow supports  42  is shown carrying one of the settler plates  44 . The plates  44  are shown as being adjacent to each other and together defining one of the quiescent zones  34  between the adjacent plates  44 . FIG. 2B shows an elevational view of the face of two of the plates  44  and the corresponding hollow supports  42  which are mounted on the opposite troughs  36 . The solids  26  and the liquid  27  flow upwardly from near the bottom  31  of the basin  29  and into the flow channels  34 . As described above, during the upward flow in the zone  34 , the solids  26  settle to the bottom  31  and the clarified liquid  27 C flows to an upper end  46 Z of the zone  34 , which end  46 Z corresponds to the upper ends  46 P (FIG. 2A) of the respective plates  44 . The clarified liquid  27 C flows past the upper ends  46 P and  46 Z and through an elongated outlet  47  shown in FIG. 2A extending between the two adjacent hollow supports  42 . 
     The clarified liquid  27 C assumes a level  48  in the basin  29  that may vary according to which of a plurality of embodiments of the present invention is being described. For example, FIGS. 2A,  2 B,  5 C show the level  48  as a level  48 - 1  of a first most preferable level embodiment. The level  48 - 1  of the clarified liquid  27 C is somewhat below a top  49  of the respective hollow support  42 , such as in a range from about 0.25 inches to about 0.125 inches below the top  49 . With the level  48 - 1  in that range, the clarified liquid  27 C between the adjacent plates  44  most preferably does not completely submerge the hollow supports  42 . In this manner, the clarified liquid  27 C does not flow over either or both of the hollow supports  42 . Rather, all of the clarified liquid  27 C flows upwardly from one of the flow channels (or zones)  34 , flows through the outlet  47 , and flows into an aperture or opening  51  in the hollow support  42 . Since the first level embodiment has the level  48 - 1  lower than the top  49  of the hollow support  42 , the clarified liquid  27 C directly and completely flows into and through the opening  51 . Thus, in this embodiment normally none of the clarified liquid  27 C from the outlet  47  flows completely over either or both of the hollow supports  42 , such that there is no commingling of clarified liquid  27 C from one flow channel  34  with clarified liquid  27 C from another one of the flow channels  34 . 
     FIG. 3 shows the inlets  51  in the hollow supports  42  spaced along a longitudinal axis  52  of the hollow supports  42 . The spacing of the inlets  51  along the axis  52  is selected according to the anticipated range of flow rates of the liquid  27  and the solids  26  into the basin  29 . In this manner, with such flow rate into the basin  29  and with a particular embodiment of the levels  48  of the present invention, the desired flow rate of clarified liquid  27 C through the inlets  51  is obtained. For example, flow rates into the basin  29  of about 6 gallons per minute (GPM) to about 9 GPM are common; and flow rates of about from one GPM to 1.5 GPM into the inlets  51  may be expected. As described above for the first level embodiment, for example, with the level  48 - 1  all of the clarified liquid  27 C flows (arrow  27 C) from the outlet  47  through the openings  51 . 
     Outlet Troughs  36   
     FIGS. 3 and 4 show that the clarified liquid  27 C flows in the hollow supports  42  toward the respective outlet trough  36  and exits through a trough inlet  53  into the outlet trough  36 . The hollow supports  42  are connected to the respective trough inlets  53  of the outlet troughs  36  for supplying clarified liquid  27 C from the hollow supports  42  to the outlet troughs  36 . In FIG. 4 a weir  54  is shown provided at the top of each side  56  of the outlet troughs  36  and may be adjusted higher or lower relative to the side  56  to allow the level  48  of the clarified liquid  27 C to be set according to the particular embodiment  48 - 1 , or  48 - 2 , or  48 - 3  of the level  48  that is desired (see respective FIGS. 5A,  5 B, and  5 C). 
     As examples in addition to the most preferable level embodiment  48 - 1  described above, the preferable embodiment of the level  48 - 3  is shown in FIGS. 4 and 5A, in which the level  48 - 3  of the clarified liquid  27 C is preferably substantially above the top  49  of the respective hollow support  42 . The phrase “substantially above” indicates that such level  48 - 3  is from about two inches to about six inches above the top  49  of the respective hollow support  42 . With the level  48 - 3  in that range, the clarified liquid  27 C preferably is not only between the hollow supports  42  and between the adjacent plates  44 . In particular, the clarified liquid  27 C is also shown flowing upwardly from one of the flow channels (or zones)  34 - 3  and over (see arrow  27 C- 3 ) the hollow supports  42  past the opening  51  into the outlet  47  of the next adjacent flow channel  34 - 3 . Although the benefits of the first level embodiment described with respect to FIG. 5C are reduced, as indicated by the two arrows  27 C-P, there is still a substantial amount of flow of the clarified liquid  27 C into the hollow supports  42  through the openings  51 . In this situation, the word “substantial” means that at least half of the clarified liquid  27 C flowing upwardly in the flow channel  34 - 3  below the outlet  47  flows into the openings  51  in the hollow support  42  shown on the left in FIG.  5 A. Preferably, the “substantial” amount of flow means that as much as two thirds of the clarified liquid  27 C flowing upwardly in the flow channel  34 - 3  below the outlet  47  flows into the openings  51  in that hollow support  42 . Accordingly, in the third level embodiment normally there is some commingling of clarified liquid  27 C (see arrows  27 C- 3 ) from one flow channel  34 - 3  with clarified liquid  27 C from another one of the flow channels  34 - 3 . However, this amount of commingling involves less than half of the clarified liquid  27 C flowing upwardly in the flow channel  34 - 3  below the outlet  47  flows into the opening  51  in the hollow support  42 . As a result, during normal settling operations, the flow of clarified liquid  27 C in the hollow support  42  may be separately sampled for examination of the performance of the separate flow channel  34 - 3  that supplies the primary amounts  27 C-P of clarified liquid  27 C to that hollow support  42 . Further, as described below, flow from the flow channel  34 - 3  may still be substantially blocked during servicing involving replacing a fouled support  42 . Here, “substantially blocked” means that only the flow  27 C- 3  that would normally have entered the next support  42  to the left in FIG. 5A, for example, will not be blocked upon removal of the right hand support  42  shown in FIG.  5 A. 
     As indicated above, if it is found by such sampling that too many solids  26  are present in the clarified liquid  27 C from that flow channel  34 - 3 , then one or both of the plates  44  (“fouled plates”) (and the corresponding hollow supports  42 ) that define that flow channel  34  may be removed and replaced. Further, as shown with respect to FIG. 6, the servicing operations of removal and replacement of the one or both such fouled plates  44  may be performed without interrupting or substantially impairing the normal settling operations of the other flow channels  34 . FIG. 6 shows that one hollow support  42  and one corresponding fouled plate  44  have been removed to define a now-wider flow channel  34 W between remaining plates  44 W- 1  and  44 W- 2 . As described above, there is the tendency for the same flow rate of liquid  27  and solids  26  to occur in the now-wider flow channel  34 W between the two remaining adjacent plates  44 W- 1  and  44 W- 2 . However, such flow through and out of that now-wider flow channel  34 W into the outlet troughs  36  may be blocked. FIG. 6 shows that during one aspect of the servicing operation the blocking is achieved by placing a plug  61  in each of the trough inlets  57  corresponding to where the now-removed hollow supports  42  were. 
     With such flow to the outlet trough  36  from the now-wider flow channel  34 W blocked by the plugs  61 , the only flow of the clarified liquid  27 C from the now-wider flow channel  34 W would be over the top  49  of the respective hollow support  42 , and whether that flow occurs depends on the current embodiment of the level  48  (and thus on the setting of the weirs  54 ). For example, in embodiment  48 - 1  (FIG. 5C) there would be no flow of the clarified liquid  27 C from the now-wider flow channel  34 W over the top  49  of the respective hollow support  42 . As another example, in embodiment  48 - 3  there would be the flow  27 C- 3  of the clarified liquid  27 C from the now-wider flow channel  34 W over the top  49  of the respective hollow support  42 . As a further example, in embodiment  48 - 2  shown in FIG. 5B, there would be the flow  27 C- 2  of the clarified liquid  27 C from the now-wider flow channel  34 W over the top  49  of the respective hollow support  42 . 
     Any such flow  27 C- 2  or  27 C- 3  would be into a separate hollow support  42  associated with each of the remaining settler plates  44 W- 1  and  44 W- 2  (FIG.  6 ). That flow  27 C- 2  or  27 C- 3  into the separate hollow supports  44 W- 1  or  44 W- 2  is via the integral inlets  51  provided in each of those separate hollow supports  42 W- 1  or  42 W- 2 . These integral inlets  51  permit receipt of the clarified liquid  27 C- 2  or  27 C- 3  flowing from the now-wider flow channel  34 W. However, because these integral inlets  51  are designed to receive the flow only from the original adjacent narrower flow channels  34 , the flow from the now-wider flow channel  34 W is restricted, such that the flow into and in the now-wider flow channel  34 W is reduced. As described above, with the reduced flow rate in the now-wider flow channel  34 W there is an increase of the residency time of the liquid  27  and the solids  26  in the now-wider flow channel  34 W. For example, if the now-wider flow channel  34 W is twice as wide and the flow rate is half as much, there will be a return to the original settling rate of the former narrow flow channel  34 . As a result, there is an increase in the likelihood of being able to continue normal settling operation of the clarifier  25  during the removal of the fouled settler plate  44 . 
     To facilitate the above-described removal of a fouled plate  44  and the corresponding hollow support  42 , FIGS. 7 and 8 depict an embodiment of the trough  36  in which the respective hollow supports  42  are removable from the trough  36 . The upper end of the trough  36 , which may be the weir  54  for example, is formed in two pieces  71 . A lower support plate  72  of the pieces  71  is mounted on the trough  54 . The upper surface  73  of the lower plate  72  is scallop-shaped to define a series of depressions  74 . Each depression  74  is adapted to receive one of the hollow supports  42  and to space such hollow support  42  from an adjacent hollow support  42  according to the desired width W of the flow channels  34 . As described below, for the various embodiments of the hollow supports  42  the scallop shape is adapted to conform to the shape of the external surface of the particular hollow support  42 . An upper mounting plate  76  is placed over the hollow supports  42  and fastened to secure the hollow supports  42  to the lower plate  72 . The lower surface of the upper plate  76  is also scallop-shaped to define a series of depressions  77  corresponding to the depressions  74 . Each depression  77  is also adapted to receive the top  49  of one of the hollow supports  42  and to work with the lower plate  72  to space such hollow support  42  from an adjacent hollow support  42  according to the desired width W of the flow channels  34 . 
     To permit removal of any one of the hollow supports  42  that is held on the trough  36  by the plates  72  and  76 , the upper plate  76  is removed from the lower plate  72 . The desired hollow support  42  is then removed from the appropriate depression  74 , exposing the trough inlets  53  formerly connected to the now-removed hollow support  42 . Once the desired hollow support  42  is removed, the plugs  61  are inserted into the now-exposed trough inlets  53  to block those inlets  53 . 
     Embodiments of Hollow Supports  42   
     In FIGS. 1 through 8 the hollow supports  42  are shown as pipes or tubes (here referred to as  42 P) that are by definition hollow so as to contain the flowing clarified liquid  27 C. Such pipes or tubes  42 P also have structural properties that enable them to span opposite outlet troughs  36  and carry the respective settler plates  44  without sagging. Such pipes or tubes  42 P comprise one embodiment of the hollow supports  42 . FIGS. 9A and 9B show two ways of providing the openings  51  the tubes  42 P to admit the clarified liquid  27 C. FIG. 9A shows the opening  51  provided in an upper half  71  of the pipe  42 P as defined by axes  72  and  73 . The opening  51  thus faces toward the right, which is toward all of the primary flows  27 C-P shown in FIGS. 5A-5C. This opening is referred to as  51 P to designate the primary flow. This facing of the opening  51 P fosters these primary flows  27 C-P and the desired flow of clarified liquid  27 C from one flow channel  34  primarily, if not exclusively, into the adjacent pipe  42 . 
     FIG. 9B also shows the opening  51  provided in the upper half  71  of the pipe  42 P and designated  51 C. The opening  51 C is centered on the axis  73  to foster receipt of clarified liquid  27 C from each flow channel  34  on the opposite sides of the one pipe  42 P, for example. Such opening  51 C is useful, for example, in the third embodiment of the level  48  shown in FIG. 5A in that the level  48 - 3  is above the tops  49  of the pipes  42 P and relatively equal flow (see arrows  27 C-E in FIG. 9B) from both such sides of the one pipe  42 P into the opening  51  C may be desired. 
     FIGS. 10A and 10B show a second embodiment of the hollow supports  42 , which are in the form of support and collection troughs referred to as  42 T. The troughs  42 T have a V-shaped cross section and have structural properties that enable them to span opposite outlet troughs  36  and carry the respective settler plates  44  without sagging. Also, inlet notches  81  may be provided in each opposite edge  82  to admit the clarified liquid  27 C. 
     The troughs  42 T are mounted on the outlet troughs  36  so that the height of the edges  82  is below that of the top of the weirs  54 . With the clarified liquid  27 c below the top of the weirs  54  the clarified liquid  27 C flows into the notches  81 . The upper end of the outlet troughs  36 , which may be the weir  54  for example, may be formed in two pieces  71  in the manner described with respect to FIG. 8 (as shown in FIG.  10 A). For efficiency of disclosure, in FIG. 10A only the lower support plate  72  of the pieces  71  is shown mounted on the outlet trough  54 . The upper surface  73  of the lower plate  72  is scallop-shaped to define a series of depressions  74 . Each depression  74  shown in FIG. 10A is V-shaped to receive one of the troughs  42 T and to space such trough  42 T from an adjacent trough  42 T according to the desired width W of the flow channels  34 . The scallop shape is adapted to conform to the shape of the lower external surface of the trough  42 T, Not shown in FIG. 10A is an upper mounting plate  76  placed over the trough  42 T and removably fastened to secure the trough  42 T to the lower plate  72 , which is done in the manner described with respect to FIG.  8 . The lower surface of the upper plate  76  is also scallop-shaped to define a series of depressions  77  corresponding to the shape of the upper surface of the V-shaped trough  42 T. Each depression  77  is also adapted to receive the top  49  of one of the trough  42 T and to work with the lower plate  72  to space such trough  42 T from an adjacent trough  42 T according to the desired width W of the flow channels  34 . 
     FIG. 10C shows a third embodiment of the hollow supports  42 , which are in the form of support and collection troughs referred to as  42 U. The troughs  42 U have a U-shaped cross section and have structural properties that enable them to span opposite outlet troughs  36  and carry the respective settler plates  44  without sagging. Also, inlet notches  81  may be provided in each opposite edge  82  to admit the clarified liquid  27 C. The troughs  42 U may also be mounted on the outlet troughs  36  so that the height of the edges  82  is below that of the top of the weirs  54 , and the two pieces  71  used to removably mount the troughs  42 U on the outlet trough  36  as described above with respect to the troughs  42 T, for example. 
     Clarification Methods 
     A first embodiment of the method of the present invention clarifies the liquid  27  by separating the suspended solids  26  from the liquid  27   1 . The first embodiment may include operations of defining the separate channels  34  in the basin  29  for guiding the clarified liquid  27 C. A given one of the separate channels  34  has the upper end  47  defined by the first and second spaced hollow supports  42 . Another operation is providing at least one of the apertures  51  in at least one of the first and second hollow supports  42  that define the given one of the separate channels  34  to collect the clarified liquid  27 C from the upper end of the given one of the separate channels  34 . 
     A second embodiment of the method of the present invention also clarifies the liquid  27  by separating the suspended solids  26  from the liquid  27 . The second embodiment may include an operation of providing the clarifier section  37  with first and second opposite sides  28 , each of the sides  28  having an outlet trough  36  mounted thereon. Separate channels  34  are defined in the clarifier section  37  for guiding the clarified liquid  27 C, with each separate channel  34  having the upper end  47 . A pair of spaced hollow supports  42  are provided at the upper end  47  of each of the channels  34  and extending across the clarifier section  37  between the first and second opposite sides  28 . A series of the openings  51  is provided in each of the hollow supports  42  to collect the clarified liquid  27 C from the upper end  47  of each of the separate channels  34 . The supports  42  guide the collected clarified liquid  27 C to the outlet trough  36 . 
     A third embodiment of the method of the present invention also clarifies the liquid  27  by separating the suspended solids  26  from the liquid  27 . The third embodiment may include an operation of defining the clarifier section  37  in the basin  29 , the section  37  having opposite sides  28  and the trough  36  at each opposite side  28 . For each of two settler plates  44 , an operation provides the hollow support  42  extending between the troughs  36 . The providing of the supports  42  is effective to support each respective plate  44  with an upper end  47  of the respective plate  44  positioned above a lower end of the respective plate. Liquid  27  and the solids are directed between the two supported settler plates  44  from the lower end to the upper end  47  to settle the solids  26  from the liquid  27  and provide clarified liquid  27 C to the upper ends  47  of the two settler plates  44 . In a next operation there is collecting the clarified liquid  27 C in at least one of the hollow supports  44 . 
     A fourth embodiment of the method of the present invention also clarifies the liquid  27  by separating the suspended solids  26  from the liquid  27 . The fourth embodiment may include an operation of flowing the clarified liquid  27 C in a plurality of the separate upwardly extending flow paths  34 . Each flow path  34  has the upper end  47 . Another operation is separately collecting the clarified liquid  27 C from each of the plurality of separate upwardly extending flow paths  34 , as shown in level embodiment  48 - 1  (FIG.  5 C), for example. 
     A fifth embodiment of the method of the present invention also clarifies the liquid  27  by separating the suspended solids  26  from the liquid  27 , and may include suboperations of the operations of the fourth method described above. The fifth embodiment may include suboperations of the fourth embodiment operations of separately collecting and directing. The suboperations are include defining a separate conduit (e.g., the support  42 ) at the upper end  47  of each of the respective separate flow paths  34 . Each of the separate conduits  42  receives clarified liquid  27 C from a separate flow path  34  and supplies the clarified liquid  27 C to the outlet trough  36  through a separate inlet  53 . Further suboperations include determining that one of the separate conduits  42  is not performing the collecting operation properly (see description above of FIG.  6 ). A further suboperation includes removing the one conduit  42  from the upper end  47  of the respective separate flow path  34  in conjunction with closing the separate inlet  53  to the trough  36  corresponding to the one removed conduit  42 . The closing may be by inserting the plug  61  into the inlet  53 . Then there is an operation of installing a new separate conduit  42  conduit at the upper end  47  of the respective separate flow path  34  and opening the separate inlet  53  to the trough  36  corresponding to the new separate conduit  42 . The opening may be by removing the plug  61  from the inlet  53 . 
     In the above methods, the operations of collecting clarified liquid  27 C may be by providing the tubes or pipes  42 P, or by providing the troughs  42 T or  42 U, for example. The troughs  42 T have the opening  51  provided by the open top of the trough  51  T, which may have the notches  81 , for example. 
     In a sixth embodiment of the method of the present invention there may be provided a primary path, such as one of the flow paths  27 C- 1  or  26 C- 2  or  27 C- 3 , for a primary amount of the clarified liquid  27 C to flow from the upper end  47  into and through the left, for example, pipe  42 P shown in FIGS. 5A-5C. 
     It is to be understood that the scope of the present invention is to be defined by the appended claims and not limited by the foregoing description, which describes the presently preferred ways in which the present invention may be embodied. Numerous other embodiments may be devised and still come within the scope of the present invention.