Patent Publication Number: US-2022212974-A1

Title: Apparatus and methods for dewatering sludge

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a division of U.S. patent application Ser. No. 16/624,023 filed on Dec. 18, 2019, which is the US national stage of International Application No. PCT/CA2018/050760 filed on Jun. 21, 2018, which in turn claims the benefit of priority of U.S. Patent Application No. 62/523,033 filed on Jun. 21, 2017. U.S. patent application Ser. No. 16/624,023, International Patent Application No. PCT/CA2018/050760 and U.S. Patent Application No. 62/523,033 are hereby incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to sewage sludge treatment, and in particular to apparatus and methods for dewatering sludge and other materials. 
     BACKGROUND 
     Sewage sludge is composed of a mixture of solid and liquid. Separating the liquid from the solid allows the liquid to be reused and the solid to be more efficiently transported for treatment. Various systems for separating liquids from sludge or other materials exist in the prior art, including: U.S. Pat. Nos. 3,677,409, 5,503,753, 4,816,167, 3,028,011, US 2016/0289109, U.S. Pat. Nos. 5,462,661 and 4,021,347. 
     The inventor has determined a need for improved apparatus, methods and systems for dewatering sludge and other materials. 
     SUMMARY 
     One aspect of the present disclosure provides an apparatus for dewatering sludge. The apparatus comprises a tank having an internal space divided by a dividing wall into an intake chamber and an extract chamber, an intake pipe connected to the intake chamber by an intake valve, a discharge pipe connected to the extract chamber by a discharge valve, and a transfer pipe providing fluid communication between the intake chamber and the extract chamber. The transfer pipe has a first opening near the bottom of the intake chamber, and a second opening near the top of the extract chamber. A pump selectively creates positive and negative pressure within the intake chamber. A screen is positioned within the extract chamber between the second opening of the transfer pipe and the discharge pipe. 
     Another aspect provides a method for dewatering sludge. The method comprises providing a tank having an internal space divided by a dividing wall into an intake chamber and an extract chamber, an intake pipe connected to the intake chamber by an intake valve, a discharge pipe connected to the extract chamber by a discharge valve, a transfer pipe providing fluid communication between the intake chamber and the extract chamber, with a first opening near the bottom of the intake chamber and a second opening near the top of the extract chamber, a pump for selectively creating positive and negative pressure within the intake chamber, and, a screen within the extract chamber positioned between the second opening of the transfer pipe and the discharge pipe. The method further comprises applying negative pressure to the intake tank by the pump with the intake valve open to suck a mixture of solid and liquid into the intake tank, through the intake pipe; injecting a polymer into the intake tank to coagulate the solids; and applying positive pressure to the intake tank by the pump with the intake valve closed, the transfer valve open and the discharge valve open to force the mixture of coagulated solid and liquid through the transfer pipe into the extract chamber, whereby the screen traps the coagulated solids allowing liquid to pass through the discharge pipe. 
     Further aspects and details of example embodiments are set forth below. 
    
    
     
       DRAWINGS 
       The following figures set forth embodiments in which like reference numerals denote like parts. Embodiments are illustrated by way of example and not by way of limitation in the accompanying figures. 
         FIG. 1  shows a cross section of an example dewatering apparatus according to one embodiment with the door closed. 
         FIG. 2  shows a cross section of the apparatus of  FIG. 1  with the door open. 
         FIG. 3  shows an exterior view of a prototype dewatering apparatus according to one embodiment. 
         FIG. 4  shows a view of the interior of the extract chamber of the apparatus of  FIG. 3 . 
         FIG. 5  shows the screen of the apparatus of  FIG. 3 . 
         FIG. 6  shows the apparatus of  FIG. 3  with the door open for removing solids from the extract chamber. 
         FIG. 7  shows an example dewatering apparatus installed on a truck bed according to one embodiment. 
         FIG. 8  shows the apparatus of  FIG. 7  with the door open and the truck bed raised on an incline. 
         FIG. 9  shows an example dewatering apparatus according to one embodiment. 
         FIG. 10  is an exploded view of the apparatus of  FIG. 9 . 
         FIG. 11  is a top view of the apparatus of  FIG. 9 . 
         FIG. 11A  is a sectional view taken along line A-A in  FIG. 11 . 
         FIG. 11B  is a side view of the apparatus of  FIG. 9 . 
         FIG. 11C  shows a detailed view of the area in circle C of  FIG. 11A . 
         FIG. 11D  shows a detailed view of the area in circle D of  FIG. 11B . 
         FIG. 12  shows the transfer pipe of the apparatus of  FIG. 9 . 
         FIG. 12A  is a side view of the transfer pipe of  FIG. 12 . 
         FIG. 12B  is a front view of the transfer pipe of  FIG. 12 . 
     
    
    
     DETAILED DESCRIPTION 
     The following describes example apparatus and methods for dewatering sludge. 
     For simplicity and clarity of illustration, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. Numerous details are set forth to provide an understanding of the examples described herein. The examples may be practiced without these details. In other instances, well-known methods, procedures, and components are not described in detail to avoid obscuring the examples described. The description is not to be considered as limited to the scope of the examples described herein. 
       FIG. 1  and  FIG. 2  show a cross section of an example apparatus  100  for dewatering sludge. The apparatus  100  comprises a tank  102  having an internal space divided by a dividing wall  104  into an intake chamber  106  and an extract chamber  108 . A pump  110  is connected to the intake chamber  106  to selectively create positive and negative pressure in the intake chamber  106 . The pump  110  may have a primary filter  112  and a secondary filter  114 . The pump  110  and filters  112 / 114  may be substantially the same as those in standard vacuum trucks. An intake pipe  116  having an intake valve  117  is connected to the intake chamber  106  for drawing sludge or other materials into the tank as discussed below. A coarse intake filter (not shown), such as for example a canister filter, may be provided on the intake pipe to prevent large (e.g. greater than about ½ inch diameter) solids from entering the intake chamber. A discharge pipe  118  having a discharge valve  119  is connected to the extract chamber  108  for discharge of liquids from the tank as discussed below. 
     A transfer pipe  120  provides fluid communication between the intake chamber  106  and the extract chamber  108 . The transfer pipe  120  has a first opening  122  near the bottom of the intake chamber  106  and a second opening  124  near the top of the extract chamber  108 . The dividing wall  104  has an opening near the top thereof to permit the transfer pipe  120  to pass through, but otherwise seals off the extract chamber  108  from the intake chamber  106 . 
     A screen  130  is positioned within the extract chamber  108  between the second opening  124  of the transfer pipe  120  and the opening of the discharge pipe  118 . In some embodiments, as illustrated in  FIG. 1 , the screen  130  may substantially conform to the shape of the extract chamber  108  and may have a hole for the second opening  124  of the transfer pipe  120 . Details of an example screen are discussed below with reference to  FIG. 5 . In the illustrated example, the end portion of the extract chamber  108  of the tank  102  comprises a door  140  which may be opened to permit access to the extract chamber  108  for removal of solids. The screen  130  comprises an open end with a generally circular rim  132  which presses up against a rim  142  of the door  140  when the screen  130  is in place and the door  140  is closed. The door  140  may be held closed by a buckle latch  144 , as shown in  FIG. 2 , or any other suitable mechanism. The tank  102  may also be provided with a relief valve  152  and pressure gauge  154 . In some embodiments, the tank  102  also has an access hatch  156  (see  FIG. 1 ) in an upper portion of the intake chamber  106  for providing access thereto, and a cleaning port  158  (see  FIG. 1 ) in a lower portion of the intake chamber  106  near the bottom of the transfer pipe  120  and the dividing wall  104 . The hatch  156  and/or port  158  may be at different locations in other embodiments. 
     In the illustrated example, the transfer pipe  120  is at an approximately 45 degree angle from the horizontal. The transfer pipe  120  may be at a different angle from the horizontal in other embodiments. As used herein, the term “horizontal” refers to a direction parallel to the longitudinal axis of the tank  102 , such that the absolute angle of “horizontal” may change as the orientation of the tank  102  changes. This configuration permits any sludge or other materials remaining in the intake chamber  106  or transfer pipe  120  to fall into the extract chamber  108  when the tank  102  is tipped for dumping or cleaning as discussed below. In the illustrated example, an angled portion  105  of the dividing wall  104  is also at an approximately 45 degree angle from the horizontal. The dividing wall  104  and transfer pipe  120  may be differently configured in other embodiments (for example, the dividing wall may extend vertically upward from the first opening at the bottom end of the transfer pipe in some embodiments, or the dividing wall may comprise a curved wall and the transfer pipe may be substantially vertical, as discussed below with reference to  FIGS. 9-12 ), and thus the intake and extract chambers  106  and  108  and screen  130  may have different shapes in different embodiments. 
       FIGS. 3, 4 and 5  show features of a prototype dewatering apparatus  100 A according to one embodiment. Elements of the prototype apparatus  100 A of  FIGS. 3-5  are correspondingly numbered with corresponding elements of apparatus  100  of  FIG. 1 .  FIG. 4  shows a view of the interior of the extract chamber  108 A of the tank  102 A of apparatus  100 A of  FIG. 3 , wherein the second opening  124 A of the transfer pipe  120 A is shown protruding through the dividing wall  104 A.  FIG. 5  shows the screen  130 A of the apparatus  100 A of  FIG. 3 . The screen  130 A comprises a rim  132 A with a structural support frame  134 A extending therefrom. A web  136 A of wire mesh and fine screen material is supported by the rim  132 A and frame  134 A.  FIG. 6  shows the apparatus  100 A of  FIG. 3  with the door  140 A open for removing solids from the extract chamber. 
     In some embodiments, dewatering apparatus  100 / 100 A may be installed on a truck bed (as shown in  FIGS. 7 and 8 ), on a trailer or any other transport platform to move the apparatus to and from worksites. The operation of the example apparatus  100  of  FIGS. 1 and 2  is shown in  FIG. 7  and  FIG. 8  with the apparatus  100  in different orientations and the door  140  in a closed position and open position. In some embodiments, the apparatus  100  may move to a different orientation, for example by raising a truck bed on an incline, as shown in  FIG. 8  with the door in an open position. 
     To commence sludge intake, the intake pipe  116  is connected to a hose or the like (not shown) that is placed into a source of sludge. Negative pressure is applied to the intake chamber  106  by the pump  110 , with the intake valve  117  open, causing the sludge to be drawn into the intake chamber  106  through the intake pipe  116 . A polymer is injected into the intake chamber  106 , for example through a separate polymer injection valve (not shown). Injecting a suitable polymer into the intake chamber  106  causes solids in the sludge to coagulate into clumps as known in the art. 
     Once the sludge is in the intake chamber  106 , the intake valve  117  is closed and positive pressure is applied to the intake chamber  106  by the pump  110 , with the discharge valve  119  open. This positive pressure causes the sludge to be forced into the first opening  122 , up the transfer pipe  120 , and through the second opening  124  into the extract chamber  108 . After the sludge passes through the second opening  124  into the extract chamber  108  the screen  130  separates the solid and liquid by blocking the solid and permitting the liquid to pass through the screen  130  and out through the discharge pipe  118 . 
     In some embodiments, once liquid has been discharged, the door  140  is opened and the solids caught by the screen  130  within the extract chamber  108  are manually removed by shoveling or other means. In some embodiments, the tank  102  may be tipped for dumping, for example by raising a truck bed on an incline as shown in  FIG. 8 . 
       FIGS. 9-11D  show another example apparatus  200 . Elements of the apparatus  200  of  FIG. 9-11D  are correspondingly numbered with corresponding element of apparatus  100  of  FIG. 1 , in the form of  2   xx  instead of  1   xx . The apparatus  200  operates substantially similarly to the apparatus  100  of  FIG. 1  but differs from apparatus  100  in a number of details, including the shape of the intake chamber  206 , extract chamber  208 , dividing wall  204 , transfer pipe  220  and screen  230 , as discussed below. In the example of  FIGS. 9-11D , elements of the apparatus  200  constructed from steel or other rigid materials are shown, but various flexible hoses connecting pipes of the apparatus  200  to each other are not shown, as described below. 
     The apparatus  200  comprises a tank  202  having an internal space divided by a dividing wall  204  into an intake chamber  206  and an extract chamber  208 . In this embodiment the dividing wall  204  does not have an angled section, but is instead curved in a manner similar to the opposite side of the intake chamber  206  such that the intake chamber  206  itself is in the form of a pressure tank. In the illustrated example, the intake chamber  206  has a baffle assembly  207  (see  FIG. 11A ) therein for reducing sloshing of material within the tank  202  when a truck is driving with the apparatus  200  mounted thereon. 
     The tank  202  is mounted on a deck assembly  250  configured to be mounted on a truck. A sill assembly  252  is attached to the bottom of the tank  202 , and the sill assembly  252  is pivotally coupled to hinge pins  254  at the rear of the deck assembly  250  such that the tank  202  may be tilted up at the front for dumping. The sill assembly  252  may be higher at the front that the back such that the tank  202  is at a slight incline, as best seen in  FIGS. 11A and 11B . 
     A pump (not shown) is connected to the intake chamber  206  to selectively create positive and negative pressure in the intake chamber  206 . In the illustrated example the pump is configured to be coupled to a primary float trap  212  though a first connecting pipe  211 A mounted on the side of the tank  202  and a second connecting pipe  211 B mounted on the deck assembly  250 . Flexible hoses (not shown) are connected between the primary float trap  212  and the first connecting pipe  211 A, between the first connecting pipe  211 A and the second connecting pipe  211 B, and between the second connecting pipe  211 B and the pump. The pump may also have one or more secondary filters (not shown) associated therewith. The pump, float trap  212  and filters may be substantially the same as those in standard vacuum trucks. 
     An intake pipe  216 / 216 A/ 216 B having an intake valve  217  is connected to the intake chamber  206  for drawing sludge or other materials into the tank as discussed below. In the illustrated example, a coarse intake filter  215 , such as for example a canister filter, is connected by flexible hoses (not show) between a first portion  216  of the intake pipe and a second portion  216 A of the intake pipe to prevent large (e.g. greater than about ½ inch diameter) solids from entering the intake chamber. The second portion  216 A of the intake pipe is connected by another flexible hose (not shown) to a third portion  216 B of the intake pipe that has the intake valve  217 . A discharge pipe  218  having a discharge valve  219  is connected to the extract chamber  208  for discharge of liquids from the tank as discussed below. 
     With reference to  FIGS. 10, 11A, 11C, 12, 12A and 12B , the apparatus  200  comprises a transfer pipe  220  which is generally vertically oriented (with a bend near the top thereof such that the top is generally horizontal) when the tank  202  is horizontal. The transfer pipe  220  provides fluid communication between the intake chamber  206  and the extract chamber  208 . The transfer pipe  220  has a first opening  222  near the bottom of the intake chamber  206  and a second opening  224  near the top of the extract chamber  208 . The dividing wall  204  has an opening near the top thereof to permit the transfer pipe  220  to pass through, but otherwise seals off the extract chamber  208  from the intake chamber  206 . A screen  230  is positioned within the extract chamber  208  between the second opening  224  of the transfer pipe  220  and the opening of the discharge pipe  218 . In some embodiments, the screen  230  may substantially conform to the shape of the extract chamber  208 . The screen  230  has a hole for receiving the upper end of the transfer pipe  220  such that the second opening  224  is inside of the screen  230 . In the illustrated example, a snorkel assembly  226  is attached to the second opening  224  of the transfer pipe  220 , as described below. 
     The first opening  222  at the bottom of the transfer pipe  220  has a funnel-type structure  223  for guiding fluid into the transfer pipe  220 . As best seen in  FIG. 12A , the bottom of the funnel-type structure  223  is shaped to conform to the bottom of the tank  202  and bottom portion of the dividing wall  204  where it meets the tank  202 . A flange  225  is provided near the second opening  224  of the transfer pipe  220 . The flange  225  is configured to be bolted to a corresponding flange  227  of the snorkel assembly  226 , which is attached to the screen by a sealing gasket  228 . The snorkel assembly  226  also comprises a floating ball valve  229  which allows material to enter the extract chamber  208  from the transfer pipe  220  when positive pressure is applied to the intake chamber  206 , and prevents material from leaving the extract chamber  208  through the transfer pipe  220  when negative pressure is applied to the intake chamber  206 . 
     In the illustrated example, the end portion of the extract chamber  208  of the tank  202  comprises a door  240  which may be opened to permit access to the extract chamber  208  for removal of solids. The screen  230  comprises an open end with a generally circular rim  232  which presses up against a rim  242  of the door  240  when the screen  230  is in place and the door  240  is closed. The screen  230  may have pins  231  on opposed sides thereof configured to be received in pin receivers  233  (see  FIG. 10 ) on the inside of the extract chamber  208 . One or more sealing rings (not shown) may be provided at the interface between the rim  242  of the door  240  and the rim  232  of the screen. The door  240  may be held closed by a plurality of latches  244  or any other suitable mechanism. 
     The tank  202  may also be provided with a relief valve (not shown) and a pressure gauge (not shown). In the illustrated example, the tank  202  has an access hatch  256  (see  FIGS. 11 and 11B ) at one of the sides of the intake chamber  206  for providing access thereto, and the door  240  has a dump port  258  in a lower portion thereof. The hatch  256  and/or dump port  258  may be at different locations in other embodiments. The dump out  258  may be referred to as an access hatch, a mud gate, cleanout, and so on. 
     In operation, to commence sludge intake, the intake pipe  216 B is connected to a hose or the like (not shown) that is placed into a source of sludge. Negative pressure is applied to the intake chamber  206  by the pump, with the intake valve  217  open, causing the sludge to be drawn into the intake chamber  206  through the intake pipe  216 . A polymer is injected into the intake chamber  206 , for example through a separate polymer injection valve (not shown). Injecting a suitable polymer into the intake chamber  206  causes solids in the sludge to coagulate into clumps as known in the art. Once the sludge is in the intake chamber  206 , the intake valve  217  is closed and positive pressure is applied to the intake chamber  206  by the pump, with the discharge valve  219  open. This positive pressure causes the sludge to be forced into the first opening  222 , up the transfer pipe  220 , and through the second opening  224  into the extract chamber  208 . After the sludge passes through the second opening  224  into the extract chamber  208  the screen  230  separates the solid and liquid by blocking the solid and permitting the liquid to pass through the screen  230  and out through the discharge pipe  218 . 
     It will be appreciated that numerous specific details are set forth in order to provide a thorough understanding of the exemplary embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the embodiments described herein. Furthermore, this description is not to be considered as limiting the scope of the embodiments described herein in any way, but rather as merely describing implementation of the various example embodiments described herein. 
     The description provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed. 
     Although the embodiments have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As can be understood, the examples described above and illustrated are intended to be exemplary only. 
     As will be apparent to those skilled in the art in light of the foregoing disclosure, many alterations and modifications are possible to the methods and systems described herein. While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as may reasonably be inferred by one skilled in the art. The scope of the claims should not be limited by the embodiments set forth in the examples, but should be given the broadest interpretation consistent with the foregoing disclosure. 
     The present disclosure may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive.