Biofilm support media assembly apparatus and method

An apparatus and method for the assembly of biofilm support structure modules from individual sheets of biofilm support structure. The apparatus consists of a number of dowel rods protruding from a base. Hollow tubes are placed over the rods. Alignment holes are made in the biofilm support structure sheets such that the sheets may be slid over the tubes. When the required number of biofilm support structure sheets have been stacked in this fashion, caps are attached to the ends of the tubes, holding the biofilm support structure sheets in place. The assembled biofilm support structure modules may then be placed in a wastewater treatment plant. The tubes may also be used as passages for outside air or water, allowing the biofilm support structure sheets to be cleaned while still inside the treatment plant.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to an assembly method for biofilm 
support structure modules used in the treatment of wastewater and to an 
apparatus used to effect this method. In particular, the present invention 
is directed toward a fast, simple method of assembling the biofilm support 
structure modules after shipping of individual components, saving on 
shipping costs and cutting down on assembly time compared with currently 
used assembly methods. It is also directed to an assembly fixture that is 
used to assemble the biofilm support structure modules from biofilm 
support structure sheets and module retainer tubes. 
2. Background and Description of the Related Art 
Biofilm refers to a layer of biologically active organisms which digest and 
hence eliminate organic matter from wastewater, thereby purifying the 
wastewater. In advanced applications of biofilm technology, biofilm is 
grown on or in a medium which acts as a carrier for such organisms. In 
some cases, the biofilm media are inorganic sheets or support structures 
which provide increased surface area on which the biofilm can grow. 
Biofilm support structures have been used in wastewater treatment processes 
for more than fifteen years. These structures predominantly made of 
plastic, usually are installed in trickling filters or placed in 
wastewater treatment aeration tanks to treat and purify wastewater. 
Biofilm support structures are sold assembled in modules for small scale 
home wastewater treatment plants and in larger sizes for commercial 
wastewater treatment plants. Assembly of the modules takes place in 
factories or in the field using a gluing method. Using this method, 
individual sheets of the biofilm support structure are layered on top of 
one another, with waterproof glue spread between each layer to bind them. 
The biofilm support structure sheets are not flat. Rather, each sheet has 
a texture that is pleated in two roughly perpendicular directions, forming 
alternating rounded peaks and valleys. In assembled form, adjacent sheets 
are oriented in corrugated fashion. That is, the orientation of adjacent 
sheets alternates so that valleys in a particular sheet rest on peaks of 
the sheet below it. The peaks of the upper sheet in turn support the 
valleys of the sheet placed on top of it. The sheets alternate in this 
manner in order to provide more available surface area for the growth of 
biofilm. This in turn provides more treatment surface area for wastewater. 
In certain wastewater treatment applications the entire biofilm support 
structure modules are submerged in the fluid being treated within a 
wastewater treatment plant. 
Because of the corrugated arrangement of the assembled biofilm support 
structure sheets in the assembled module, the factory assembled modules 
have a large shipping size, causing unnecessarily high freight costs. This 
cost could be reduced by assembling the modules in the field rather than 
before shipping. However, if the modules are assembled in the field using 
a gluing method, trained workers must travel to the assigned location to 
perform the assembly. The cost of the labor involved in this solution is 
ultimately much more expensive than the shipping costs incurred following 
assembly in the factory. A new method of assembling the biofilm support 
structure modules is therefore needed. This new method must be able to be 
performed in the field, but must be simple enough that trained workers are 
not necessary to carry it out, or must be quick and simple enough that 
assembly can be effected at a distribution plant after reception of the 
shipment from the factory. 
SUMMARY OF THE INVENTION 
The present invention comprises a module assembly fixture, to be used in 
conjunction with biofilm support structure sheets, module retainer tubes, 
and retainer caps. At the factory, the biofilm support structure sheets 
are first trimmed to the size required for the particular application. At 
least two holes are then made in each biofilm support structure sheet. The 
biofilm support structure sheets are then stacked together in a carton and 
shipped to the assigned location for installation, or to a distribution 
plant. The stacking arrangement used for shipping unassembled biofilm 
support structure sheets is different from that used in assembling the 
modules. The biofilm support structure sheets are nested; that is, all the 
sheets are oriented the same way, so that the peaks and valleys of all the 
sheets line up vertically. Stacked in this way, the volume of the biofilm 
support structure sheets is much smaller than that of the assembled 
biofilm support structure modules. For example, for a 500 gallon per day 
home wastewater treatment plant (a "plant"), the volume of an assembled 
biofilm support structure module is 21.78 cubic feet, but the volume of 
the nested stacked biofilm support structure sheets used to assemble the 
biofilm support structure module is only 3.79 cubic feet. Thus, the 
shipping volume is greatly reduced, saving in cost or allowing more 
biofilm support structure sheets to be shipped at the same time. 
After the biofilm support structure sheets are shipped to the desired 
destination, the plant installer can easily assemble the biofilm support 
structure modules using the module assembly fixture. The module assembly 
fixture aids in a module assembly procedure, simplifying and speeding up 
the task. 
The fixture comprises a base with extended dowel rods, and may be made of 
any sturdy material, such as metal or wood. The steps in the assembly 
procedure are as follows: 
1. Slide module retainer tubes over the dowel rods. 
2. Slide the biofilm support structure sheets onto the dowel rods, over the 
module retainer tubes, one at a time until the required thickness of 
biofilm support structure sheets is attained. 
3. Glue the retainer caps onto the top ends of the retainer tubes. 
4. Take the module out of the assembly fixture. 
5. Turn the module over and glue retainer caps on the bottom ends of the 
retainer tubes. 
After assembly in the above fashion, assembled biofilm support structure 
modules can be installed in the aeration tanks or trickling filters of 
wastewater treatment plants. The time required for assembly using the 
method of the present invention is much less than that required using a 
gluing method. Further, the method of the present invention requires much 
less exposure to the potentially toxic vapors of the glue that is normally 
used. The method of the present invention is also much simpler, obviating 
the need for specially trained workers to perform the task. During use 
within the wastewater treatment plant, the module retainer tubes can be 
used in the cleaning of the modules by connecting them to an outside water 
or air source. 
It is therefore an object of the present invention to provide a biofilm 
support structure module assembly method which allows the module 
components to be shipped in a more compact form than factory-assembled 
biofilm support structure modules, substantially saving on shipping costs. 
It is a further object of the present invention to provide a biofilm 
support structure module assembly method which is faster and easier than 
the gluing method, substantially saving on labor costs. 
It is yet another object of the present invention to provide a biofilm 
support structure module that allows for biofilm support structure sheet 
cleaning by connecting module retainer tubes with an outside air source or 
water source. 
It is still a further object of the present invention to provide a module 
assembly fixture to be used in performing the assembly method of the 
present invention. 
It is an additional object of the present invention to provide an assembly 
method for a biofilm support structure module that is safer 
environmentally than are current methods, in that glue fumes are not 
dissipated into the atmosphere.

DETAILED DESCRIPTION OF THE INVENTION 
The detailed description of the present invention is based on a home 
wastewater treatment plant which is designed to process 500 gallons of 
fluid per day. All dimensions and numbers used in the description are 
based on the amount of biofilm support structure necessary for such a 
treatment plant. The sizes of the biofilm support structure sheets, the 
dimensions of the module assembly fixture, the number of dowel rods, and 
other dimensions and quantities specified may vary with the size and type 
of fluid treatment plant contemplated for use with the present invention. 
Thus, numbers specified herein are not limitations on the scope of the 
present invention but are merely illustrative of one particular 
application. 
FIG. 1 shows nested sheets of biofilm support structure, stacked as they 
would be for shipping from the factory to the plant installer. As shown, 
alternating biofilm support structure sheets are rotated 180 degrees 
before packing in order to effect the nesting arrangement. This method of 
stacking is preferred, as it saves time (and therefore money) during 
assembly of the modules. However, stacking the biofilm support structure 
sheets in a nesting configuration without rotating alternating sheets is 
compatible with the present invention. Both long sheets 1 and short sheets 
2 of biofilm support structure are required for the wastewater treatment 
plant, which utilizes two long modules and two short modules. The long 
sheets 1 are rectangles 15 inches by 48 inches in dimension and the short 
sheets 2 are rectangles 15 inches by 221/2 inches in dimension. Twenty-six 
long sheets 1 and twenty-four short sheets 2 are required for one home 
wastewater treatment plant. The biofilm support structure stacks, nested 
as shown, are packed in a 57.5 inch by 16.25 inch by 7 inch carton and 
shipped to a plant installer. This carton occupies a volume of 3.79 cubic 
feet. The volume of an assembled biofilm support structure module using 
the same sheets of support structure is 21.78 cubic feet. Thus, shipping 
the biofilm support structure module in unassembled form results in a 
savings of 82.6 percent of the assembled biofilm support structure module 
shipping volume. The savings in shipping costs associated with this 
reduction in volume is substantial. 
The module assembly fixture 3 is shown in FIG. 2. The plant installer uses 
the module assembly fixture 3 to assemble the biofilm support structure 
modules from the biofilm support structure sheets. The module assembly 
fixture consists of a base 11 supporting a number of dowel rods 4. The 
dowel rods 4 protrude from the base 11 at some angle, preferably 90 
degrees. The dowel rods 4 are of a length that is equal to or less than 
the thickness of a biofilm support structure module. The dowel rods 4 act 
as an aligning means for components of the biofilm support structure 
module. 
As shown in FIG. 3, hollow module retainer tubes 6 are slid over the dowel 
rods 4. Each module retainer tube 6 is a hollow cylinder having a 
cylindrical outside wall and a bore through its longitudinal axis. At 
least one end of each module retainer tube 6, the bottom end, is open. 
A first biofilm support structure sheet 5 is moved from the stack of long 
sheets 1 or the stack of short sheets 2 and is placed on the assembly 
fixture 3 by sliding the holes in the biofilm support structure sheets 
over the dowel rods 4. A second biofilm support structure sheet is then 
placed on top of the first biofilm support structure sheet 5 so that the 
two sheets are oriented in corrugated fashion. If the sheets were shipped 
stacked in the preferred manner, as shown in FIG. 1, the second biofilm 
support structure sheet is placed on the first without rotating the second 
biofilm support structure sheet; the second biofilm support structure 
sheet is simply moved by a distance of one pleat so that there is a 
corrugated arrangement rather than a nesting one. If the biofilm support 
structure sheets were not shipped stacked as shown in FIG. 1, the second 
biofilm support structure sheet may have to be rotated 180 degrees with 
respect to the first biofilm support structure sheet in order to effect 
the proper corrugated orientation. The holes made in the biofilm support 
structure sheets and the alignment function of the dowel rods 4 ensures 
that the sheets will be oriented properly. 
The above process is repeated until all the required biofilm support 
structure sheets have been stacked on the assembly fixture 3. Thirteen 
long sheets 1 are required for each of the two long modules and twelve 
short sheets 2 are required for each of the two short modules. 
After the required number of biofilm support structure sheets are placed on 
the assembly fixture 3, retainer caps 7 are glued onto the top ends of the 
module retainer tubes 6. The plant installer then holds the bottom of the 
first biofilm support structure sheet 5 and lifts the entire biofilm 
support structure module off the assembly fixture 3. The module is turned 
over and retainer caps 7 are glued onto the bottom ends of the module 
retainer tubes 6. The assembly of the biofilm support structure module is 
now complete. FIG. 4 shows completed long and short biofilm support 
structure modules 8 and 9. 
In alternative embodiments, the retainer caps 7 may be fastened to the 
module retainer tubes 6 in a manner other than gluing. The attachment 
means may be a clip which fits around the retainer cap 7 and holds the 
retainer cap 7 in place. The ends of module retainer tubes 6 may be 
threaded, either on the inside surface, the outside surface, or on both 
surfaces, so as to mate with threaded retainer caps 7. The module retainer 
tubes 6 may have annular ridges which mate with annular tabs on the 
retainer caps 7. The bottom ends of the module retainer tubes 6 may not 
require retainer caps 7 at all; an embodiment of the present invention may 
utilize module retainer tubes 6 having outwardly extending lips on the 
bottom ends, the diameter of the lips being large enough to hold the 
biofilm support structure sheets in place. The exact fastening means used 
is not a limiting feature of the present invention. What is important is 
that the biofilm support structure sheets be securely attached to the 
module retainer tubes 6. 
The above process is repeated until all the biofilm support structure 
modules necessary for the given application are complete. The completed 
long biofilm support structure modules 8 and short biofilm support 
structure modules 9 are then packed into an aeration compartment 10, as 
shown in FIG. 5. 
The diameter of the dowel rods 4 can be any size, as long as it is smaller 
than the inside diameter of the module retainer tubes 6. In the preferred 
embodiment, the diameter of the dowel rods 4 varies from 1/4 inch to 7/8 
inch, and the inside diameter of the module retainer tubes 6 varies from 
1/2 inch to 1 inch. The module retainer tubes 6 are of a length sufficient 
to approximately span the thickness of a biofilm support structure module. 
In some cases, the module retainer tubes 6 are slightly shorter than the 
thickness of the biofilm support structure module, so that the biofilm 
support structure sheets must be compressed in order to attach retainer 
caps 7. These biofilm support structure modules are used in applications 
in which the biofilm support structure sheets must be tightly bound. In 
other cases, the module retainer tubes 6 are slightly longer than the 
thickness of the biofilm support structure module. These biofilm support 
structure modules are used in applications in which the biofilm support 
structure sheets are to be given more freedom of movement within the 
wastewater treatment plant. In the preferred embodiment, the length of the 
module retainer tubes 6 is from two inches shorter to one inch longer than 
the thickness of the biofilm support structure module. The module retainer 
tubes 6 and retainer caps 7 may be made from PVC or other plastic 
material. 
The described method of assembling the biofilm support structure modules is 
simple and quick. Compared with the various gluing methods prevalent in 
the art, module assembly time is reduced from 50 to 85 percent using the 
method of the present invention. Thus, labor expenses are greatly reduced, 
as is exposure of assemblers to potentially toxic glue fumes. 
The present invention can be used to assemble biofilm support structure 
modules constructed from any material and manufactured in any shape. It 
therefore has much broader application than any of the prevalently used 
gluing methods, which may only be used with PVC materials. 
The module assembly fixture 3 may be made of any sturdy material, and is 
preferably made of wood or metal. The number of dowel rods 4 used and the 
distance between adjacent dowel rods 4 is determined by the size of the 
biofilm support structure sheet, the distance between the valleys on the 
sheet, the material used to construct the biofilm support structure sheet, 
and the shape of the biofilm support structure sheet. The dowel rods 4 
should be spaced close enough together so that a biofilm support structure 
module assembled on the assembly fixture 3 is held securely together. The 
holes in the biofilm support structure sheets corresponding to the dowel 
rods 4 may be drilled, cut, stamped, or otherwise provided at the factory 
prior to shipping in order to save labor costs at the plant. It will be 
appreciated by those skilled in the art that the inter-dowel rod distance 
may be adjusted in an alternative embodiment of the invention so that 
different structures and applications may be accommodated by merely 
sliding and then securing the dowel rods 4 at an inter-dowel rod distance 
appropriate to the application. 
In an alternate embodiment, shown in FIG. 6, U-shaped rod binders 12 are 
used in place of dowel rods 4. All retainer caps 7 may thus be attached 
without flipping the assembled biofilm support structure module. 
The module retainer tubes 6 can also be utilized as orifice pipes. To be 
used in this manner, the module retainer tubes 6 are connected by at least 
one end with an outside air source or water source. Module cleaning can 
then be accomplished while the biofilm support structure modules are 
installed in the wastewater treatment plant by using outside air or water 
to flush the biofilm support structure module. To do this, the retainer 
caps 7 on at least one end of module retainer tubes 6 must be formed so as 
to allow liquid or air to pass through from the outside of the module 
retainer tubes 6 to the inside hollow portion of the module retainer tubes 
6. For example, a hole may be made in the end of the retainer caps 7 and a 
hose or other conduit carrying the forced air or water can be connected to 
the retainer cap 7. As long as the outside diameter of the retainer caps 7 
is larger than the holes in the biofilm support structure sheets, the 
biofilm support structure modules will be securely bound. The module 
retaining tubes 6 may be perforated with at least one hole, and 
preferrably with a number of holes, along their lengths to allow incoming 
air or water to flush the biofilm support structure sheets for cleaning 
purposes. 
FIG. 7 shows an example of a cleaning apparatus 13 which may be connected 
to the ends of the module retainer tubes 6 during the process of cleaning 
the modules. It is preferred that when the biofilm support structure 
module to be cleaned is installed in the water treatment plant, one end of 
at least some of the module retainer tubes 6 is located along the 
periphery of the plant or is otherwise available to the cleaning apparatus 
13. The outlets of the cleaning apparatus 13 may be inserted into the 
retainer cap 7, or may be attached by a coupling means 14. The coupling 
means 14 may be a threaded sleeve or some other means for attaching the 
cleaning apparatus 13 to the retainer caps 7. Alternatively, the coupling 
means 14 may replace the retainer caps 7 on the ends of the module 
retainer tubes 6 that will be attached to the cleaning apparatus 13. The 
coupling means 14 will thus also perform the function of keeping the 
biofilm support structure sheets secured to the module retainer tubes 6. 
Water or air enters the inlet 16 of the cleaning apparatus 13 and is 
distributed among the module retainer tubes 6 used in the biofilm support 
structure module. Retainer caps 7 fastened to the other ends of the module 
retainer tubes 6 prevent the water or air ("fluid") from flowing out those 
ends. The fluid is therefore forced out the holes 15 which perforate the 
module retainer tubes 6, flushing the nearby biofilm support structure 
sheets. Cleaning of the biofilm support structure sheets is accomplished 
in this manner. 
Other cleaning apparatus 13 configurations are possible. If both ends of 
the module retainer tubes 6 are accessible, the cleaning apparatus 13 may 
be attached at both ends, or may be attached to one end on some of the 
module retainer tubes 6 and at the other end of the other module retainer 
tubes 6. In larger water treatment plants, the module retainer tubes 6 of 
adjacent biofilm support structure modules may line up so as to provide a 
longer flow path for incoming water or air. To allow cleaning of both 
biofilm support structure modules, the cleaning apparatus 13 is attached 
to the module retainer tubes 6 of a first biofilm support structure 
module. At least some of the module retainer tubes 6 in this first biofilm 
support structure module will not be perforated with holes 15. The 
retainer caps 7 on both ends of such module retainer tubes 6 are open, 
allowing the cleaning fluid to pass completely through the module retainer 
tube 6. The fluid will then flow into the open end of a module retainer 
tube 6 in the second biofilm support structure module. The module retainer 
tube 6 in this module will be perforated with holes 15, and the retainer 
cap 7 on the far end will be closed, in order to prevent further flow of 
fluid through the end of the module retainer tube 6 and forcing the fluid 
out of the holes 15. Thus, using the module retainer tubes 6 of the first 
biofilm support structure module as a fluid conduit, cleaning of the 
biofilm support structure sheets in the second biofilm support structure 
module is accomplished. 
It will be recognized by persons skilled in the art that the apparatus and 
method of the present invention has applications beyond the construction 
of biofilm support structure modules. The present invention is an 
improvement over any process involving the binding of any sheet material 
having a similar structure in a stack or module. For example, certain 
commercial heating units or air conditioning units use sheets of fibrous 
filter material that are loosely bound in a stack. This filter material 
may have a structure similar to that of the biofilm support structure 
sheets. It is contemplated that the present invention would be applicable 
for use in the binding of such sheet material, and of any sheet material 
for any purpose. 
Preferred and alternate embodiments of the present invention have now been 
described in detail. It is to be noted, however, that this description is 
merely illustrative of the principles underlying the inventive concept. It 
is, therefore, contemplated that various modifications of the disclosed 
embodiments will, without departing from the spirit and scope of the 
present invention, be apparent to persons skilled in the art.