The present invention relates generally to the cleaning of sewage treatment

facilities and more particularly, to a cover system which inhibits the growth of algae on the

surfaces of sedimentation water treatment tanks employed in such facilities.

1

SUBSTITUTE SHEET (fHJLE 26)

1

2 BACKGROUND OF THE INVENTION

3

4 The necessity for providing sewage treatment plants to clean and purify water

5 discharged from homes and factories is well known. The function of a sewage treatment

6 facility is to receive raw sewage (water containing waste material) as discharged from a city

7 sewage system and clean it to ultimately produce purified water. This is accomplished through

θ a series of biological and mechanical processes.

_ In a typical water treatment facility, the raw sewage is received from the sewage

10 system and passed through a coarse screen to remove large pieces of matter. The sewage is

11 next directed to one or more primary sedimentation tanks or clarifiers. The sewage remains

12 in primary sedimentation for a period of time sufficient to allow the majority of the heavy

13 matter to settle to the bottom of the tank forming sludge. This sludge is removed for

14 "digestion" by microorganisms. The digested sludge is then dried and can be used as compost

15 or fertiliaZer. The remaining liquid is treated in a second biological system to remove

16 ammonia. The liquid from this treatment is then aerated and passed into final sedimentation

m. 7 water treatment tanks to remove any remaining solid material.

18 Water treatment tank configurations vary with each treatment facility

19 application. This notwithstanding, most final sedimentation water treatment tanks are circular.

20 This simplifies automatic skimming, churning and/or bottom scraping operations. More

21 specifically, by eliminating inaccessible corners and providing uniform surfaces, a revolving

22 scraper arm or skimmer blade can provide complete and efficient churning and prevent sludge

23 buildup.

During operation of one type of water treatment tank, water containing sediment enters the center of the tank. In a continuous process, the lighter clean water is effectively decanted from the heavier sediment containing water. More particularly, the clean water is

displaced from the tank by the constant flow of water containing sediment into the tank. The

displaced clean water is forced to flow under a baffle plate for collecting floating scum and

then over a weir, ultimately entering a clean water flow channel. The clean water flow

channel directs the water to the next treatment stage where it is chlorinated and further made

safe to be discharged into a river or stream.

Presently, algae growth in the trough or launder channel is a serious problem in clarifier tanks. Specifically, as algae builds up on the weirs of the clarifier tank, it can

substantially interfere with the hydraulic flow therethrough. Algae typically adheres to the

surfaces of the weir and the trough, where it becomes unsightly and odorous. When the launder is cleaned, however, the algae is often loosened and causes clogging of the

downstream filters. For many years, the removing of algae from the baffle, weir, spillway and clean

water flow channel has been completed primarily by scrubbing the tank structure with brushes manipulated by hand. Because the final treatment tanks are quite large, this is a labor-intensive and tedious process , involving a large expenditure of man-hours . Additionally ,

the algae removing process must be done frequently, thereby further adding to the cost. More recent proposals directed at the problem of algae growth have utilized

mechanical brushes to automate the cleaning process. One such device is disclosed in U.S. Pat. 4,830,748. While this apparatus is somewhat effective in cleaning the baffle, weir,

spillway and clean water flow channel of a circular tank, it is somewhat limited in application

in that it is adapted to be mounted to a revolving skimmer blade. Accordingly, it can only be effectively utilized with circular water treatment tanks incorporating such a blade. The cost of obtaining, installing, and maintaining such an automated system, though perhaps preferable

to the alternative of periodic manual scrubbing, is also quite high. Other waste water facilities

have utilized chlorine and other chemicals in sufficient concentrations to kill the algae.

However, a large number of waste water facilities utilize a denitrification process that precludes the use of such chemical additives. As such, a need is recognized for a proactive system that inhibits the growth of algae in the launder channel of a clarifier tank.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a cover system

which is positionable over selected portions of the clarifier tank to prevent sunlight from

reaching the surfaces of the launder channel. By blocking the sunlight, the cover system of

the present invention inhibits the growth of algae on the surfaces of the launder channel and obviates the need for frequent scrubbing or complex automated cleaning devices.

The inventive cover system comprises at least one panel member positionable above the channel, weir, and sometimes partially over scum baffle of a clarifier tank to prevent

sunlight from reaching the surfaces thereof. In accordance with an illustrative embodiment

of the present invention intended for use with a circular clarifier tank, one or more panel

members having an outer radius of curvature corresponding to the radius of curvature of the

tank may be employed so that the outer edge of the panel member or members may be arranged in a contiguous fashion along the inwardly facing wall of the tank and secured thereto

at selected intervals. Where a plurality of panel members are employed, they may be mounted

in an end to end abutting fashion such that the lateral side of each cover abuts a lateral side of an adjacent cover. In this manner, the panel members may be arranged over an entire launder

channel to substantially prevent light from reaching the interior surfaces thereof. The cover system of the present invention has application to other tank configurations, such, for example,

as those possessing a rectangular cross section. Referring to the mounting of the panel member in an end to end abutting

fashion, the adjacent-abutting panel members form a smoothly-continuous surface by virtue

of a shiplap-type joint through which each panel member are interconnected . This shiplap-type

joint allows for the first lateral side of the panel member to be secured to the next adjacent one

of said plural panel members so that together they form the smoothly -continuous surface. A method for inhibiting the growth of algae on fluid contacting surfaces of a

water treatment tank is also provided. Typically, water treatment tanks include a central

influent, at least one substantially vertical peripheral wall having an upper and interior surface,

a peripheral baffle having inside and outside surfaces, a substantially vertical weir, a spillway,

and a launder channel having a width. The method of inhibiting the growth of algae includes

the step of securing to the peripheral tank wall, a first panel member positionable over at least

a portion of the launder channel, for preventing light from reaching interior surfaces thereof. The first panel member is dimensioned and arranged to span the width of said launder channel and is comprised of a substantially opaque material. Thereafter, a second panel member is

secured to the peripheral tank wall, the second panel member being positionable over at least a portion of the launder channel, for preventing light from reaching interior surfaces thereof. Similar to the first panel member, the second panel member is dimensioned and arranged to

span the width of the launder channel and is comprised of a substantially opaque material. The second panel member is secured in end-to-end immediately-adjacent relation to said first panel

member. Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of

illustration and not as a definition of the limits of the invention, for which reference should

be made to the appended claims.

BRIEF DESCRIPTION OP THE DRAWINGS

In the drawings, wherein like reference numbers denote similar elements throughout the several views:

FIG. 1 is a cutaway sectional view of a clarifier tank showing a cover panel

member constructed in accordance with an illustrative embodiment of the present invention

positioned thereon; FIG. 2 is a partial perspective view depicting an arrangement of cover panel

members along the perimeter of a generally arcuate clarifier tank in accordance with the

embodiment of FIG. 1; FIG. 3 is a perspective view of the cover panel member of FIG. 1;

FIG. 4 is a cross sectional side view of a cover panel member constructed in accordance with another embodiment of the present invention and installed over a launder

channel; FIG. 5 is a cross sectional side view of the cover panel member of FIG. 4

shown installed at a downwardly sloping incline; FIG. 6 is a cross sectional side view of the cover member of FIG. 4 shown installed at a downwardly sloping incline utilizing a modified support structure; FIG. 7 is a cross-sectional view of a cover member configured for installation

over a dual- eir launder channel in accordance with a further embodiment of the present

invention; and FIG. 8 is a cross-sectional view of a cover member configured in accordance

with a further illustrative embodiment of the present invention positioned thereon; FIG. 9 A is a perspective view of a molded mounting flange having a radius of

curvature substantially equal to the peripheral tank wall;

FIG. 9B is a perspective view of a plurality of resilient clips which act to secure each cover over the channel; and

FIG. 10 is a side view of a clarifier tank showing a cover panel member

constructed in accordance with an illustrative embodiment of the present invention positioned

thereon; and FIG. 11 is a perspective view of the cover panel as shown in FIG. 10.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Reference is now made to FIG. 1 showing the cover system 10 of the present invention installed over the clean water flow or launder channel C of a final sedimentation

water treatment tank 12. In the illustrative embodiment depicted in FIG. 1, system 10 is

configured as a modular assembly of individual panel members 14, only one of which panel members is shown. In accordance with the present invention, each panel member 14 is

securable to tank 12 and, when installed in the position shown in FIG. 1, is dimensioned to

completely cover the launder channel C, the spillway S, the weir gate W, and scum baffle B.

As discussed previously, a principal object of the present invention is to prevent

the gr< th of algae on the interior surfaces of the launder channel, weir, spillway and baffle. To this end, each panel member as panel member 14 comprises an opaque material which

reflects and/or absorbs substantially all light incident thereon. In this regard, it will be readily

appreciated that a wide variety of rigid or flexible materials may be utilized for the construction of the panel members. The panel members may, for example, be formed from

metal or alloys thereof, fiberglass, or from substantially opaque thermosetting "*r thermoplastic materials. It is also possible, of course, to make the panel member opaque by applying a suitable coating, such as a light reflective or absorptive coating, to the exterior and/or interior

surfaces thereof. In so doing, it is possible to utilize even transparent or translucent plastic

materials to fabricate the panel members of the present invention. With reference now to FIG. 2, it will be seen that the panel members 14 of

cover system 10 may be dimensioned and contoured to achieve a contiguous relationship with the interior surface of the clarifier tank and with each other. In the illustrative embodiment

of the present invention depicted in FIGS. 1-3, the clarifier tank has a circular sidewall

configuration. Accordingly, each panel member 14 defines an exterior edge surface 14a having a radius of curvature corresponding to the radius of curvature of the tank. Moreover,

the lateral side surfaces 16a, 16b of panel member 14 diverge in a direction toward exterior edge surface 14a so that adjacent panel members may be mounted in an end to end abutting

fashion.

To prevent light from entering the channel between the adjacent lateral edge

surfaces of abutting panel members, lateral overlapping regions 17a and 17b are provided (FIG. 3). When panel members 14 are assembled in the manner shown in FIG. 2, a cover

system is formed which extends substantially around the entire clarifier tank over the launder channel. Light is thereby prevented from reaching the interior surfaces of the launder channel,

spillway, weir, and baffle. In a currently preferred implementation, the individual covers are fabricated from a molded reinforced fiberglass composite as a one piece, unitarily-integrated unit. Thus, each molded cover incorporates the panel member, and, if desired, an end bracket or flange

to facilitate securing of the panel member to the clarifier tank. Advantageously, this enables significant reductions in both manufacturing time and for installation as compared to other prior art arrangements and systems. Most preferably, the thickness of the fiberglass panels

is in the range of about 3/16 to 3/4 of an inch, a range that provides substantial structural strength and rigidity while remaining sufficiently light weight for unusual ease of installation.

Each panel member 14 can also be provided with a network of cross braces or other strengthening members (not shown) to enhance the rigidity to each panel member and provide

a walkway surface capable of supporting one or more maintenance workers. Typically, such

cross braces or other strengthening members can be fabricated out of a lightweight material

such as balsa wood which can then be sandwiched between two or more layers of fiberglass. If desired, the upper surface of each panel member may be provided with a roughened, non- skid texture to prevent injury to such workers.

As will be readily appreciated by those skilled in the art, a variety of fastening

devices and techniques may be used to secure panel members 14 in position over the launder

channel C. In the embodiment shown in FIG. 1 , panel member 14 incorporates an upwardly

extending, mounting flange portion 18 having an exterior surface contoured for contiguous

engagement with the interior, circumferential surface of clarifier tank 12. Mounting flange portion 18 may be secured directly to the peripheral wall of the clarifier Uuik using

conventional mechanical fasteners at radially spaced intervals. As seen in FIG. 1, it will be seen that each panel member 14 may also be

provided with one or more mounting flange portions 20 having a radius of curvature

corresponding to that of the substantially vertical, inner surface of weir W. Of course, the length of flange portions 20 must be relatively short so as not to substantially obstruct the flow

of clean water over the weir. When secured to weir W by appropriate fastening means , second mounting flange portions 20 maintain the lower edge of panel member 14 in fixed position

relative to the launder channel and thus the panel member 14 is mounted in cantilever fashion over the weir and spillway. Advantageously, the second mounting flange portions 20 may be provided with a vertical arrangement of slots or grooves (not shown) to allow vertical adjustment relative to the weir and, thus, adjustment of the panel member 14. In this way, the

horizontal axis of the panel members can be adjusted if desired. The top surface of each panel member may be provided with handle means,

such as recessed regions 22 (. 2) for facilitating the installation or removal of the cover. Service personnel may thus easily remove the covers by hand to access the launder channel

for regular scheduled maintenance. When it is anticipated that frequent access to the channel

may be required, the cover can be secured to the interior wall or other surfaces of tank 12 and/or the weir W by a series of corrosion resistant retaining members.

In the illustrative embodiment of FIGS. 1-3, the retaining members are

configured as resilient clips which act to secure each cover over the channel in much the same way as the previously described upper and lower mounting flanges. A plurality of upper clips,

only one of which - generally indicated at 24 - is shown, are mounted on the peripheral wall and are engageable with an upwardly extending portion of panel member 14. Illustratively, clips 24 may be dimensioned and arranged to receive the upper flange portion 18, as shown

in FIG. 1. In a similar manner, a plurality of lower clips, only one of which --generally indicated at 26-- are mounted proximate the weir and engageable with a downwardly

depending portion of panel member 14. By way of particular example, clips 26 may be

dimensioned and arranged to receive the lower flange portion of panel member 14. It will, however, be readily ascertained by those skilled in the art that the panel members need not include the upper and lower flange structures discussed above and that various clip engageable

surface portions may be utilized for the purpose of retaining the panel members in an easily removed condition in accordance with the teachings of the present invention. For example,

clips dimensioned and arranged to receive a lower portion of the exterior edge surface 14a may be secured to the interior surface of the peripheral wall of tank 12. Such a configuration would permit each panel member 14 to be secured to the peripheral wall in a cantilevered

fashion over the surface of the launder channel.

As shown in FIGS. 8 and 9B, clips 13 are dimensioned and arranged to receive

a lower portion of the exterior edge surface 14a may be secured to the interior surface of the

peripheral wall of tank 12. Similar to the embodiment described above, such a configuration would permit each panel member to be secured to the peripheral wall 12 in a cantilevered fashion over the surface of the launder channel.

To effect removal of the panel member of FIG. 1, handles 22 are grasped and

an upward vertical force is applied in order to disengage both the upper and lower edges of

the cover from retaining members 24, 26. As best seen in FIG. 3, the upper surface of each panel member may also be provided with one or more covered access ports 28 to facilitate

inspection of the launder channel. Illustratively, the access ports 28 may be configured as

doors 30 which are provided with a hinging means 31 to facilitate service and inspection. With reference now to FIGS. 4-6, there is shown in cross section a modular

panel member 114 constructed in accordance with an alternate embodiment of the present

invention. As seen in FIG. 4, panel member 114 has a substantially planar upper and lower surface and is secured to opposed interior surfaces of launder channel C by fixed supports 132

and 134. Supports 132 and 134 define upper supporting surfaces 132a, 134a which may be provided with suitable apertures to accommodate the insertion of suitable mechanical fasteners . As shown in FIG. 5, supports 132\ 134 which define downwardly inclined upper support

surfaces 132a\ 134aM may be utilized if it is desired to mount panel member 114 in a downwardly inclined orientation. Alternatively, and as shown in FIG. 6, supports 132' ' and

134' ', which define downwardly inclined upper support surfaces 132a" and, 134a" respectively, may be utilized to mount panel member 114 in a downwardly inclined

orientation.

In FIG. 7, a modified embodiment of the present invention is shown. In this embodiment, panel member 214 is configured specifically for mounting over a dual weir

launder trough. In accordance with this embodiment of the present invention, the trough C is defined by first and second sidewalls 212a, 212b and is bounded on either side by

corresponding first and second weirs Wj and W ₂ . Panel member 214 may be secured in

position above trough C using any suitable securing means. In the illustrative embodiment of FIG. 7, the upper and lower surfaces of panel member 214 are provided with an upwardly

converging contour. Accordingly, support members 232 and 234, defining correspondingly contoured supporting surfaces 232a and 234a, may be utilized to secure the panel members in

position. In FIG. 8, resilient clips 13 are provided and which act to secure each cover 14 over the channel in much the same way as the previously described upper and lower mounting flanges. A plurality of lower clips 13, only one of which - generally indicated at 13 - is shown in FIG. 9B, are mounted on the peripheral wall and are engageable with an downwardly

extending portion of panel member 14. Illustratively, clips 13 may be dimensioned and arranged to receive the lower portion of the exterior edge surface 14a. By utilizing the flange

portion 20 described earlier, such a configuration would permit each panel member 14 to be secured to the peripheral wall in a cantilevered fashion over the surface of the launder channel. As shown in FIG. 9A, a mounting flange 15 is provided having a radius of

curvature corresponding to that of the substantially vertical, peripheral wall of tank 12. Of

course, the length of flange portions 15 can be variable but preferable is the length of the cover so as to fully support the cover 14. Specifically, the mounting flange which can be fabricated out of the same material as the cover such a fiberglass, has a first portion 15a that

can be secured to the peripheral wall of tank 12 by a appropriate fastening means such as

bolts, screws, rivets of the like. When secured to the peripheral wall by a appropriate

fastening means, the second portion 15b is adapted to receive and support the lower portion

of the exterior edge surface 14a. Thus, the cover 14 may be secured to the interior surface

of the peripheral wall of tank 12.

As shown in FIGS. 10 and 11, each panel member 14 may also be provided

with a shiplap-type joint 17 intregally molded into the panel member 14 so that the adjacent-

abutting panel members (not shown) form a smoothly-continuous surface by virtue of a shiplap-type joint through which each panel member 14 are interconnected. This shiplap-type

joint 17 allows for the first lateral side of the panel member 14 to be secured to the next

adjacent one of said plural panel members (not shown) so that together they form the

smoothly-continuous surface. When utilizing this structure, lateral side surfaces 16a (FIG. 2)

are preferably not provided, thus allowing for further weight and cost reductions. Moreover,

the overlapping of the lateral sides of the panel member 14 prevents unintended leakage or passage of fine particulate matter through the connection between the immediately-adjacent

panel members. And still further, this overlap advantageously permits appropriate adjustment, during installation of the inventive cover system, of the relative positions of adjacently-

disposed baffle members to compensate It would be understood that the preferred embodiments and examples described

are for illustrative purposes only and are not to be construed as limiting the scope of the present invention which is properly delineated only in the appended claims.