FIELD OF THE INVENTION 
   This invention relates to portable tanks, in particular, tanks transportable by trailer. 
   BACKGROUND OF THE INVENTION 
   A clarifier/thickener tank of a clarifier/thickener system serves two purposes. First, the clarifying aspect of the tank produces liquid clarified of suspended solids. Secondly, the thickener aspect of the tank concentrates the clarified suspended solids to an increased solids percentage. 
   Most conventional clarifier/thickener tanks have a cylindrical shape. A rectangular shape is sometimes used but is less common because of inefficiencies that can be introduced during clarification from this geometry. The cylindrical form is the most common configuration and efficient in terms of clarifier ability. The performance of the thickener aspect is independent of shape but dependent on the overall depth of the tank which provides weight from the fluid itself and the overlying thickened sludge to dewater or thicken the slurry. A clarifier/thickener tank typically has a funnel shaped bottom with steep sides to assist in removal of the solid slurry. For a conventional clarifier/thickener tank equipped with a sludge removal device such as a rake system, the slope of the bottom is about 1.5 inches for every twelve inches of run. The preferred diameter of a cylindrical clarifier/thickener tank can vary depending on the water flow rate, the density of the slurry, the slurry setting characteristics and other factors. 
   It is desirable to have a portable clarifier/thickener system so that the system may be transported to locations where the temporary use of the system is desired without the effort and expense of constructing and dismantling a fixed installation at each location the system is utilized. These construction and dismantling activities involve considerable expense from the labor, transportation and crane rental required to complete the installation. These costs become even more significant if the locale of operation is in a remote area or access to the site is intermittent. 
   The diameter of tanks which can be transported is limited by transportation laws which limit the width of a load which can be transported by road. As transported loads increase beyond a width of 10 to 12 feet, increasingly expensive and restrictive permits require purchase. For example, as load widths increase beyond 14 feet it is common for the permits to require the use of escort vehicles as well as limitations on the routes and times that the load can be transported. (See, for example, Nova Scotia Department of Transportation &amp; Public Works, Highway Operations, Policies and Procedures Manual, Procedure Number PR5033, Mar. 5, 2006.) As a result, the transport limitations place a limit on the clarifying rate of such a system since the clarifying rate of a clarifier/thickener tank is dependent on the square foot surface area of the interior of the tank. To overcome this limitation, multiple smaller tanks can be placed in series. However, this creates complexity in the system from duplication of piping, valves, sludge pumps, feed splitters, etc. Also, the capacity to accumulate and thicken solids depends on the volume of the tank. 
   SUMMARY OF THE INVENTION 
   A portable tank is disclosed which allows for rapid and inexpensive mobilization and demobilization of a clarifier/thickener at multiple locations while maintaining a desirable clarification. 
   According to one broad aspect, the invention provides a tank assembly comprising a plurality of tank sections each capable of being connected to at least one other tank section, wherein each tank section has a dimension that enables the section to be accommodated at or within a predetermined width limit for transportation by public road, and wherein a dimension of the tank directly across the sections when the tank is assembled exceeds said predetermined width limit. 
   In some embodiments, the tank assembly comprises a bottom and a side wall extending upwardly from said bottom and wherein at least two sections each comprise a portion of said bottom and a portion of said side wall. 
   In some embodiments, said predetermined width limit is defined as the maximum width for transportation without a permit in the jurisdiction in which said tank is to be transported. 
   In some embodiments, said dimension of the tank directed across the sections is 11 feet or more. 
   In some embodiments, each section has opposed edges in which one of said edges is for connection to another tank section and a dimension between said edges is greater than half said predetermined width limit. 
   In some embodiments, the tank assembly further comprises mounting means for mounting a fluid treatment device therein. 
   In some embodiments, said tank comprises mounting means for mounting a rotary device therein. 
   In some embodiments, said rotary device includes a rotor having a diameter which exceeds said predetermined width limit. 
   In some embodiments, said tank when assembled is substantially cylindrical. 
   In some embodiments, the plurality of tank sections comprise two substantially uniform semi-cylindrical halves. 
   In some embodiments, the opposed edges define an open face in a transportation position. 
   In some embodiments, the at least two tank sections are pivotally attached along the divide. 
   In some embodiments, at least two tank sections are pivotally attached. 
   In some embodiments, the tank assembly further comprises at least a portion of at least one of a clarifier and a thickener mounted to said tank assembly. 
   In some embodiments the tank sections are adapted to together hold liquid when the tank is assembled. 
   In some embodiments, the tank assembly further comprises a frame and wheels supporting the tank sections. 
   In some embodiments, the tank assembly further comprises a plurality of retractable downward supports for supporting the assembled tank. 
   According to one broad aspect the invention provides a tank assembly comprising a plurality of tank sections each capable of being connected to at least one other tank section and a fluid treatment apparatus capable of being mounted within the tank assembly when the tank assembly is assembled. 
   In some embodiments, the fluid treatment apparatus comprises at least one of a clarifier and a thickener. 
   In some embodiments, said tank assembly has an upper portion and a lower portion and the divide between at least two tank sections is directed from said upper portion to said lower portion of said tank. 
   In some embodiments, the at least two tank sections are pivotally attached along the divide. 
   In some embodiments, the tank assembly further comprises a first support connected to the first tank section at a position spaced from the pivotal axis, and extending upwardly therefrom and coupled to a second support for supporting at least part of the weight of at least one of the tank sections. 
   According to one broad aspect, the invention provides a method of transporting a tank assembly comprising providing at least two tank sections wherein each tank section has a dimension that enables the section to be accommodated at or within a predetermined width limit for transportation by public road and wherein a dimension of the tank assembly directed across the sections when the tank assembly is assembled exceeds said predetermined width limit and orienting each tank section for transportation with the dimension that enables the section to be accommodated at or within a predetermined width limit directed across the width of the road. 
   According to one broad aspect, the invention provides a method of assembling a first tank section and a second tank section pivotally connected to each other by a pivotal connection, comprising providing support for supporting the first tank section, such that the second tank section is free to move relative to said first tank section about said pivotal axis, and rotating the second tank section about the pivotal connection to form an assembled tank with the first tank section. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the invention will now be described with reference to the attached drawings in which: 
       FIG. 1  is left side view of a portable tank apparatus according to an embodiment of the invention; 
       FIG. 2  is a right side view of the embodiment of  FIG. 1 ; 
       FIG. 3  is a top view of the embodiment of  FIG. 1 ; 
       FIG. 4A  is a perspective view of a pivoting hinge post assembly according to the embodiment of  FIG. 1 ; 
       FIG. 4B  is a perspective view of a stationary hinge post assembly according to the embodiment of  FIG. 1 ; 
       FIG. 5  is a bottom perspective view of a pivot tank section according to the embodiment of  FIG. 1 ; 
       FIG. 6  is a bottom perspective view of a stationary tank section according to the embodiment of  FIG. 1 ; 
       FIG. 7  is a perspective view of the embodiment of  FIG. 1  with the pivot tank section in a partially rotated position; and 
       FIG. 8  is a perspective view of the embodiment of  FIG. 1  with the pivot tank section in a closed position. 
   


   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a portable tank assembly  10  which includes a trailer deck  16 , a stationary tank section  14  and a pivot tank section  12 . Supporting trailer wheels  18  are provided on the trailer deck  16  and are located towards the rear of the trailer deck  16 . The stationary tank section  14  rests on supports (not shown) on the trailer deck  16  towards the front of the trailer deck  16  and the pivot tank section  12  rests on supports (not shown) on the trailer deck  16  towards the rear of the trailer deck  16 . The supports are constructed of hollow structural steel welded to the trailer deck  16  and support each of tank sections  12  and  14  at three points on the respective tank sections  12  and  14 . The supports for the stationary tank section  14  are permanently welded, while the supports for the pivot tank section  12  are bolted to allow the pivot tank section  12  to pivot as required. 
   The pivot tank section  12  and the stationary tank section  14  are semi-cylindrical tank halves with vertical side walls, a semi-conical shaped bottom, an open face and an open top. 
     FIG. 1  shows an interior view of the tank sections  12  and  14 . Vertical flanges  60  are provided on both tank sections  12  and  14 . The vertical flanges  60  extend up the two vertical edges of the open face of each of the tank sections  12  and  14 . The vertical flanges  60  extend outward from the vertical edges parallel to the open faces of the tank sections  12  and  14  and form opposed edges extending between an upper portion and a lower portion of the tank sections  12  and  14 . The flanges  60  have a plurality of closely spaced bolt holes defined therethrough. Similarly, bottom flanges  62  are provided which extend outward from the edge of the semi-conical shaped bottom of the open face of the tank sections  12  and  14 . The bottom flanges  62  extend parallel to the open faces of the tank sections  12  and  14 . The flanges  60  and  62  define a divide between the two tank sections  12  and  14  when assembled. A plurality of bolt holes are also defined through the bottom flanges  62 . 
   Both tank sections  12  and  14  include weir halfs  26 . The weir halfs  26  are continuous pieces of sheet metal with serrated upper edges. Each of the weir halfs  26  are welded to the tank sections  12  and  14 . The weir halfs  26  are positioned along an upper inner circumference of the wall of each of the tank sections  12  and  14 . Each of the weir halfs  26  is angled inward from the respective wall of tank sections  12  and  14  at an approximately 45 degree angle. The weir halfs  26  are welded to the walls of tank sections  12  and  14  with a water-tight seal. The weir halfs  26  include weir flanges  92  located at the vertical edges of the weir halfs  26 . The weir flanges  92  extend inward parallel to the open faces of the tank sections  12  and  14 . The weir flanges  92  also have a plurality of bolt holes defined therethrough. 
   Three stationary jack legs  20  are fixed to the bottom surface of the stationary tank section  14 . The stationary jack legs  20  are spaced around the circumference of the stationary tank section  14 . The stationary jack legs  20  overhang the edge of the trailer deck  16 . The stationary jack legs  20  are shown in retracted position in  FIG. 1 . 
   Three pivot jack legs  22  are affixed to a bottom surface of the pivot tank section  12 . The pivot jack legs  22  are spaced around the circumference of the pivot tank section  12 . The pivot jack legs  22  are depicted in  FIG. 1  in a retracted and folded position. In the folded position, the pivot jack legs  22  may rest on the trailer deck  16 . The jack legs  20  and  22  are shown in more detail in  FIGS. 5 and 6 . The jack legs  20  and  22  provide retractable support for the tank sections  12  and  14 . 
   The stationary tank section  14  includes a stationary cross member  38 . The stationary cross member  38  extends laterally across the stationary tank section  14  adjacent an upper end of the open face of the stationary tank section  14 . Similarly, the pivot tank section  12  includes a pivot cross member  40 . The pivot cross member  40  extends laterally across the pivot tank section  12  adjacent an upper end of the open face of the pivot tank section  12 . Six hand rails  24  are attached to the cross members  38  and  40 . The hand rails  24  are bolted to the inner longitudinal sides of the cross members  38  and  40  opposite to the open face of the tank sections  12  and  14 . 
   A drive assembly is supported by the cross member  38 . The drive assembly consists of an electric motor  44 , a gear reducer  46  and drive plate  48  at an upper end. The electric motor is connected to the gear reducer  46  which in turn is connected to the drive plate  48 . The drive assembly also includes a drive pipe  52 , a dispersion plate  54 , a tube  42 , an input pipe  50  and a rake assembly  166 . The drive plate  48  is connected to the drive pipe  52  which extends down through a center of the tube  42 . The dispersion plate  54  is connected to the tube  42  by four threaded rods (not shown). The rake assembly  166  is bolted to a lower end of the drive pipe  52 . The input pipe  50  is connected to an outside pipe connection  51  by a flexible connection (not shown). The input pipe  50  extends out from an upper side of the tube  42 . The input pipe  50  ends in a flange for easy connection to outside connection pipe connection  51 . The means by which the drive assembly is supported is described in greater detail with respect to  FIG. 3 . 
   A bottom cone  56  is provided at a bottom point of the semi-conical shape bottom of the stationary tank section  14 . Two output pipes  58  extend out from angled sides of the bottom cone  56 . The output pipes  58  end with flanges for ready connection to associated piping and sludge pump (not shown). 
   The pivot tank section  12  is connected to the stationary tank section  14  by a loose hinge assembly. The hinge assembly includes hinge posts  30  and  32  and pairs of hinge plates  34  and  36 . The pivot hinge post  32  is vertically oriented and bolted to the pivot tank section  12  by the frontward vertical flange  60  of the pivot tank section  12 . The pivot hinge plates  34  are bolted to the pivot hinge post  32 . The stationary hinge post  30  is vertically oriented and bolted to the stationary tank section  14  by the rearward vertical flange  60  of the stationary tank section  14 . The stationary hinge plates  36  are bolted to the stationary hinge post  30 . Each of the pairs of hinge plates  34  and  36  are bolted to opposite ends of the hinge posts  30  and  32 . The hinge assembly is described in greater detail with reference to  FIGS. 4A and 4B . 
   A mast assembly extends upward from the stationary hinge post  30 . The mast assembly includes a mast  28 , a cable  162 , a mast support  160  and a mast arm  164 . The mast  28  is a steel tube. The mast  28  has associated with it a mast upper top plate  170 , a mast lower top plate  172 , a plate angle support  174 , an upper mast pivot  176  and a lower mast pivot  178 . 
   The mast upper top plate  170  and the mast lower top plate  172  each have a protrusion with a hole defined therethrough. The mast upper top plate  170  and the mast lower top plate  172  are fastened at the top of the mast  28  with the mast lower top plate  172  spaced below the mast upper top plate  170 . The holes in their protrusions are vertically aligned. The plate angle support  174  is a triangle plate welded between the mast  28  and the bottom of the protrusion of the mast lower top plate  172  for support. 
   The upper mast pivot  176  are cylindrical with an attachment flange extending from one side. A pin extends through the hole in the protrusion in the upper top plate  170  through the center of the upper mast pivot  176  and through the hole in the protrusion in the lower top plate  172 . 
   The mast support  160  is a steel rod. The mast support  160  is angled between a rearward brace leg  82  (see  FIG. 6 ) and an upper point of the mast  28 . The mast support  160  is removably bolted at each end. 
   The mast arm  164  is a steel rod. The mast arm  164  is horizontal and is connected at one end to an intermediate point of a brace  74  (see  FIG. 3 ) and at the other end to the lower mast pivot  178 . The mast cable  162  connects the upper mast pivot  176  to the end of the mast arm  164  which connects to the brace  74  (see  FIGS. 7 and 8 ). 
   The bottom end of the mast  28  is bolted to the top of a mast bearing support end flange  128  (see  FIG. 4B ). 
     FIG. 2  shows a rear view of the tank sections  12  and  14 . The tank sections  12  and  14  include vertical stiffeners  72 . The vertical stiffeners  72  are comprised of elongated flat pieces of metal. The vertical stiffeners  72  are welded to an outer surface of the walls of the tank sections  12  and  14  such that they extend vertically. The tank sections  12  and  14  also includes similar horizontally oriented stiffeners (not shown) on the bottom. 
   The stationary tank section  14  includes a discharge box  68  which is located adjacent the top rear of the stationary tank section  14 . The discharge box  68  is hollow and open topped with a substantially triangular cross-section and a discharge pipe  70  extending from its bottom surface. The discharge pipe  70  ends in a flange for attachment to other piping of the assembly (not shown). The discharge box  68  communicates with the interior of the stationary tank section  14  through a hole in the wall of the stationary tank section  14  (not shown). The hole through the wall of stationary tank section  14  is defined above the weir half  26  of the stationary tank section  14 . The discharge box  68  is welded to the rear surface of the stationary tank section  14  in a fluid tight manner. 
     FIG. 3  shows the position of the tank sections  12  and  14  on the trailer deck  16 . In particular, the tanks sections  12  and  14  take up substantially the entire length of the trailer  16  and slightly overhang the edges of the trailer  16 . The weir halfs  26  extending around the circumference of the tanks sections  12  and  14  can be clearly seen in  FIG. 3 . The substantially triangular cross-sectional shape of discharge box  68  can also be clearly seen in  FIG. 3 . 
     FIG. 3  shows the support structure for the drive assembly. In particular, the pivot tank section  12  has drive supports  76  and angle braces  78 . The drive supports  76  extend laterally from the bottom surface of the cross member  40  symmetrically spaced around a midpoint of the cross member  40 . The drive supports  76  extend toward the open face of the pivot tank section  12 . The angle braces  78  extend at an approximate 45 degree angle between the cross member  40  and an outer end of the drive supports  76 . The drive supports  76  are spaced to fit under the drive plate  48 . The drive assembly is shown in its transportation position such that it is not centered on the center line of the tank. In this position, the drive assembly is supported by the drive supports  88  of stationary tank section  14  alone. In operation mode the drive plate  48  is unbolted from the drive supports  88  and shifted and bolted on both the drive supports  88  and the drive supports  76  present on both tank sections  12  and  14  and centered along the centerline of the assembled tank. 
   The cross member  40  also includes brace legs  84 . The brace legs  84  extend laterally from the open face side of the cross member  40  and terminate in flanges at the open face of the pivot tank section  12 . The brace  74  is provided in the pivot tank section  12 . The brace  74  extends horizontally between a centre point of the cross member  40  and the outer surface of the tank. The brace  74  is a beam which helps prevent deformation of the pivot tank section  12  during rotation. 
   The stationary tank section  14  also include drive supports  88  (see  FIG. 6 ) and angle braces  86  which provide support for the drive assembly. The drive supports  88  extend outwardly from the cross member  38  under the drive plate  48 . The angle braces  86  extend at an approximately 45 degree angle between the cross member  38  and ends of the drive supports  88 . 
   The cross member  38  also includes brace legs  82 . The brace legs  82  are spaced along the cross brace  38  and extend outwardly therefrom. The brace legs  82  terminate in flanges at the open face of the stationary tank section  14 . The brace legs  82  are positioned to mate with leg braces  84  when the tank is in a closed position. 
   Also visible in  FIG. 3  are cone bottom flanges  80  of the tank sections  12  and  14  which have a plurality of bolt holes defined therethrough. Cone bottom flanges are horizontal and connect the bottom cone  56  to the tank sections  12  and  14  when assembled. 
     FIGS. 4A and 4B  show details of the hinge posts  30  and  32  and the hinge plates  34  and  36 . Turning to  FIG. 4A ,  FIG. 4A  shows the pivot hinge post  32 . The pivot hinge post  32  is an elongated hollow steel post with a square cross section. Also depicted are two hinge base plates  104 . Each of the hinge base plates  104  is a flat rectangular plate with six bolt holes defined around the perimeter. A first hinge base plate  104  is welded at an upper end of the pivot hinge post  32  and a second hinge base plate  104  is welded at the bottom end of the pivot hinge post  32 . Defined in the opposite face of the pivot hinge post  32  from the hinge base plates  104  is an upper rim opening  100  and a lower rim opening  102 . The upper rim opening  100  is located adjacent the top of the pivot hinge post  32  and accommodates a top side rim  98  ( FIG. 5 ) of the pivot tank section  12  when the pivot hinge post  32  is bolted to the pivot tank section  12 . Similarly, the lower rim opening  102  accommodates a bottom side rim  96  ( FIG. 5 ) of the pivot tank section  12  when the pivot hinge post  32  is bolted to the pivot tank section  12 . 
   Two rotating hinge support plates  110  extend outwardly from the pivot hinge plate  34 . The rotating hinge support plates  110  are perpendicular to the pivot hinge plate  34 . A rotating hinge  106  extends through and is connected to the outer end of each rotating hinge support plate  110 . A pivot hinge web plate  108  is provided which extends between the two rotating hinge support plates  110 . Also provided are two pivot hinge gussets  112  which connect from the rotating hinge support plate  110  to the pivot hinge plate  34 . The pivot hinge web plate  108  and the pivot hinge gussets  112  further support the hinge assembly. The entire hinge assembly structure may be welded together or may be cast as a single part. The pivot hinge plate  34  has six bolt holes defined therethrough which match to the bolt holes in the hinge base plate  104  to allow each pivot hinge plate  34  to be bolted to one of the hinge base plate  104 . 
   Turning to  FIG. 4B ,  FIG. 4B  shows the stationary hinge post  30  which is also an elongated steel hollow post having a square cross section. A series of bolt holes  190  are defined up a side face of the stationary hinge post  30  to enable bolting of the stationary hinge post  30  to the rearward vertical flange  60  of the stationary tank section  14 . A lower rim opening  124  is defined adjacent a lower end of one face of the stationary hinge post  30 . The lower rim opening  124  is shaped to accommodate the bottom side rim  196  (see  FIG. 6 ) of the stationary tank section  14 . Similarly, adjacent an upper end of the stationary hinge post  30 , there is defined an upper rim opening  122  which is sized to accommodate the top side rim  198  (see  FIG. 6 ) of the stationary tank section  14  such that the stationary hinge post  30  can be bolted flush against the exterior side of the stationary tank section  14 . 
   The stationary hinge assembly includes hinge base plates  120  and stationary hinge plates  36 . The hinge base plates  120  are located on an opposite face of the stationary hinge post  30  from the openings  122  and  124 . There are two hinge base plates  120 , one adjacent the lower end of the stationary hinge post  30  and the other adjacent the upper end of the stationary hinge post  30 . The flat steel hinge base plates  120  have four holes spaced along each of their vertical edges to accommodate attachment of the stationary hinge plates  36 . 
   The stationary hinge plates  36  have four holes defined on each of the vertical edges which align with the holes of the hinge base plates  120  to allow bolting together of the stationary hinge plate  36  and the hinge base plates  120 . Three stationary hinge support plates  118  extending laterally outwardly from the hinge base plates  36 . A stationary hinge  114  is located at an outer end of each of the stationary support plates  118 . The stationary hinges  114  are cylindrical and in vertical alignment but spaced apart to accommodate the rotating hinges  106  of the pivot hinge plate  34  when assembled. Two stationary hinge web plates  116  connect pairs of the stationary hinge support plates  118 . The hinge assembly can be cast as a single part or have component parts welded together. 
   The mast bearing support end flange  128  and a mast bearing support  126  are also provided. The mast bearing support end flange  128  is substantially a square flat plate with protrusion extending from one corner. There are bolt holes defined through the four corners of the square portion to allow bolting of the mast  28  to the mast bearing support end flange  128 . There is also a hole defined through the outer end of the protrusion. The mast bearing support  126  has the same shape as the protrusion of the mast bearing support end flange  128 . A mast bearing support end flange  128  is positioned atop the stationary hinge post  30 . The mast bearing support  126  is positioned directly in a vertical alignment below the mast bearing support end flange  128  and above the upper stationary hinge plate  36 . The mast bearing support  126  also has a hole defined through it at an extent which is in alignment with the hole defined through the end of the protrusion of the mast bearing support end flange  128 . The mast bearing support  126  and the protrusion of the mast bearing support end flange  128  extend outwardly laterally from a corner from the stationary hinge support  30  over the stationary hinge plates  36 . A cylindrical lower mast pivot  178  (see  FIG. 1 ) is provided with an attachment flange extending from one side. The mast bearing support  126  and the mast bearing support end flange  128  support an end of the mast arm  164  (see  FIG. 1 ) through the lower mast pivot  178 . 
     FIG. 5  shows bottom details of the pivot tank section  12 . In particular, the connection of the brace legs  84 , the drive supports  76 , and the angle braces  78  to the cross member  40  can be more clearly seen. The drive supports  76  and the angle braces  78  extend along a bottom of the cross member  40  and are fastened thereto by welding or bolting. 
   The pivot jack legs  22  can also be seen in more detail in  FIG. 5 . In particular, the pivot jack legs  22  each comprise a pivot leg bottom  140  a pivot leg top  144 , a jack connection  142 , and a leg post  150 . The pivot leg bottoms  140  and the pivot leg tops  144  are connected by the jack connections  142 . A leg support plate  146  is provided at the top of each pivot leg top  144 . Each leg support plate  146  is a flat square plate which is perpendicular to the direction of the leg  22  and overhangs the sides of the pivot leg top  144 . Defined in each of the four corners of the leg support plates  146  are bolt holes. 
     FIG. 5  also shows leg base plates  148  which are flat square plates with bolt holes defined in the four corners which mirror the bolt holes of the leg support plates  146 . The leg base plates  148  are located at the lower end of the leg posts  150  which are permanently fixed to the bottom of the pivot tank section  12 . The leg base plates  148  and the leg support plates  146  are hinged along one edge (see  FIG. 1 ). In  FIG. 1 , the legs  22  are shown in a folded position. In  FIG. 5 , the legs  22  are shown in their use position in which legs  22  are rotated about the hinge between the leg support plates  146  and the leg base plates  148  to be brought into the vertical position. The leg  22  is then retained in this position by bolting together the leg support plates  146  and the leg base plates  148 . 
     FIG. 6  shows the bottom details of the stationary tank section  14 . As with  FIG. 5 ,  FIG. 6  shows how the drive supports  88 , the angle braces  86  and the brace legs  82  are connected to the cross brace  38 . In particular, the drive supports  88  and the angle braces  86  extend across a bottom surface of the cross member  38  and are bolted or welded thereto. 
     FIG. 6  also shows the stationary jack legs  20 . The stationary jack legs  20  are comprised of stationary leg tops  156 , stationary leg bottoms  154  and jack connectors  152 . The stationary leg tops  156  and the stationary leg bottoms  154  are square steel legs. The stationary leg top  156  and the stationary leg bottom  154  are connected by the jack connection  152 . The stationary leg tops  156  terminate at their upper ends with leg base plates  158 . Each leg base plate  158  has bolt holes defined through each of its four corners for attachment to the bottom of the stationary tank section  14 . 
   The portable tank assembly  10  is transported in the position depicted in  FIGS. 1 ,  2  and  3  with the exception that the mast  28  is normally lowered for transportation. In particular, the mast support  160 , the mast  28  and the mast cable  162  are removed for transportation. The hand rails  24 , bottom cone  56  and one rake arm of the rake assembly  166  that extends beyond the footprint of the trailer deck  16  are removed.  FIG. 7  shows the one arm that needs to be removed during transport. 
   The trailer deck  16  is connected to a transport truck and towed to the location where the portable assembly  10  is to be used. In this configuration, the width of the assembly tank sections  12  and  14  across the width of the road is within a predetermined width limit for transportation without a permit or for transportation using the desired permit level (i.e. acceptable cost and restrictions). Once at the location for use, the pivot tank section  12  is prepared to be rotated to align with the stationary tank section as shown in  FIGS. 7 and 8 . The mast  28  is positioned vertically and bolted to the top of the mast bearing support end flange  128 . The mast cable  162  is attached from the upper mast pivot  176  at the top of the mast  28  to an outside corner of the mast arm  164 . The mast assembly provides support to the pivot tank section  12  during rotation. The bottom cone  56  is attached to the stationary tank section  14  and the rake arm that extends beyond the trailer footprint is attached ( FIG. 7 ). A gasket (not shown) is placed between the flanges  60 ,  62  and  92  of the two tank sections  12  and  14  and between the bottom cone  56  and the flanges  80  of the two tank sections  12  and  14 . The pivot tank section  12  rotates about the hinges  106  and  114 , which in use, have a pin extending therethrough to connect the hinges  106  and  114 . The pivot tank  12  is rotated through the position shown in  FIG. 7  to the position shown in  FIG. 8 . At this point, bolts are inserted in all of the bolt holes in the flanges  60 ,  62 ,  92  and  80  to fasten the two tank halves together in a liquid tight manner to hold liquid. Flanges at the ends of the brace legs  82  and  84  are fastened. The stationary jack legs  22  are jacked down to provide support. The pivot jack legs  20  are also positioned to provide support by first unfolding the jack legs to the vertical position and bolting the leg supports  146  to the leg base plates  148  (see  FIG. 5 ). The pivot leg bottoms  140  are then jacked down to provide support for the pivot tank section  12 . Next, the hand rails are installed and a fiberglass walkway (not shown) is positioned between the hand rails  24  and rests on the cross members  38  and  40  to provide access for an operator to walk to the drive assembly. The motor, gear reducer, tube and drive pipe and drive plate assembly is shifted to operation mode. 
   Connections are then made to the various pipes to allow operation of a clarifier/thickener system utilizing the portable tank assembly  10 . In particular, a pipe is connected to input pipe  50  to pump the fluid to be treated into the assembled portable tank assembly  10 . In operation, the dispersion plate  54  acts to evenly spread the incoming slurry across the bottom of the assembled tank. The slurry enters in through the input pipe  50  flows down through the tube  42  and is evenly spread through the circumference of the tank by the dispersion plate  54 . The threaded rods allow the adjustment of the gap between the dispersion plate  54  and the tube  42  to allow for different flow rates. The connection of the drive pipe  52  to the rake assembly  166  connects the rake assembly  166  to the gear reducer  46  and motor  44 . The rake moves at a rate around 3 rpm at the rake tips and functions to “pull” the thickened sludge to the center of the tank at the point of the bottom cone so that it can be continuously pumped from the tank. The drive unit is actuated to drive the drive assembly. The rake assembly  166  rakes in a circular motion around the bottom of the tank for sludge treatment. Slurry is drained out of the bottom of the tank through bottom output pipes  58 . Clarified water spills over the weir  26  and exits the tank through the discharge box  68 . The operation of the clarifier/thickener system is conducted in a manner known in the art. 
   In the operation configuration, the width of the assembly tank sections  12  and  14  across the width of the road exceeds the predetermined width limit. 
   Although a specific embodiment of the invention has been explained, it will be evident to those skilled in the art that modifications can be made within the scope of the invention. For example, forms of legs other than jack legs and folding legs can be used. The legs could alternatively be transported separately and installed at the worksite. Hydraulic legs may also be used. 
   With respect to the hinge, any sufficiently durable pivot means known in the art could be used. With respect to pivoting the tank section  12  into position, means other than the mast assembly shown could be used to support the pivot tank section  12 . For example, pivot section  12  could be supported manually from the bottom. 
   Other drive systems with or without rake systems could be used for the clarifier/thickener system. Additionally, this tank can be used in other applications, including other fluid treatment applications, and apparatuses outside of the field of clarifier/thickener systems. Other rotary devices may also be used. The tank may be used for a clarifier or thickener system alone, rather than for both. 
   The portable tank assembly is preferably all steel construction but other materials of acceptable strength and durability can be substituted. Welding and bolting of the steel section has been described. Other attachment means can, of course, be alternatively use. 
   Although the invention is disclosed as having two equal semi-cylindrical sections, it will be understood other tank shapes and unequal division of the tank into two or more sections is contemplated by the invention.
A tank assembly is disclosed having a plurality of tank sections each capable of being connected to at least one other tank section, wherein each tank section has a dimension that enables the section to be accommodated at or within a predetermined width limit for transportation by public road, and wherein a dimension of the tank directly across the sections when the tank is assembled exceeds said predetermined width limit.