Abstract:
A cover apparatus for inhibiting the growth of algae on the fluid-contacting surfaces of an inboard launder channel disposed to receive a water flow from a central and from a peripheral region of a water treatment tank and for capturing noxious gases. Cover supports coupled to the sidewalls of the launder channel position the covers above the inboard launder channel and hinge means permit the covers to be pivoted away and toward the launder channel, for accessing the channel. In one embodiment, the inboard launder channel is circular and the covers are disposed above it with a substantially similar radial curvature. In another embodiment, the inboard launder channel is made up of straight sections angled at the end of each section to form a polygon, with fixed cover corner sections disposed in between adjacent straight sections. In still another embodiment, several straight inboard launder channels are parallel to each each other and each empty into a main channel.

Description:
RELATED DATA 
     This application is a continuation-in-part of U.S. patent application Ser. No. 08/927,621, filed Sep. 11, 1997, now U.S. Pat. No. 5,965,023, which is a continuation-in-part of U.S. patent application Ser. No. 08/696,358, filed Aug. 3, 1996, now U.S. Pat. No. 5,670,045, which is a continuation of U.S. patent application Ser. No. 08/333,411 filed Nov. 2, 1994, abandoned, all of which are incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     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 an inboard launder channel of sedimentation water treatment tanks employed in such facilities as well as a cover system that effects the capture of noxious gases in an inboard launder configuration. 
     BACKGROUND OF THE INVENTION 
     The necessity for providing sewage treatment plants to clean and purify water discharged from homes and factories is well known. The function of a sewage treatment facility is to receive raw sewage (water containing waste material) as discharged from a city sewage system and clean it to ultimately produce purified water. This is accomplished through a series of biological and mechanical processes. 
     In a typical water treatment facility, the raw sewage is received from the sewage system and passed through a coarse screen to remove large pieces of matter. The sewage is next directed to one or more primary sedimentation tanks or clarifiers. The sewage remains in primary sedimentation for a period of time sufficient to allow the majority of the heavy matter to settle to the bottom of the tank forming sludge. This sludge is removed for “digestion” by microorganisms. The digested sludge is then dried and can be used as compost or fertilizer. The remaining liquid is treated in a second biological system to remove ammonia. The liquid from this treatment is then aerated and passed into final sedimentation water treatment tanks to remove any remaining solid material. 
     Water treatment tank configurations vary with each treatment facility application. This notwithstanding, most final sedimentation water treatment tanks are circular. This simplifies automatic skimming, churning and/or bottom scraping operations. More specifically, by eliminating inaccessible corners and providing uniform surfaces, a revolving scraper arm or skimmer blade can provide complete and efficient churning and prevent sludge buildup. Water treatment tanks with non-circular configurations are not as common but are also used. 
     During operation of one type of circular water treatment tank having an inboard launder channel arrangement, water containing sediment enters the tank from influents located in both the central region of the circular tank and the outer perimeter region of the tank. If the launder channel, explained more fully in the next paragraph, does not prevent the water flow between the central region and the outer perimeter region of the tank, then the sediment-containing water can enter the tank from a single influent located anywhere in 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 sediment-containing water into the tank. The displaced clean water is forced to flow into an inboard launder channel which is disposed about the center of the tank. 
     The inboard launder channel is configured such that the inner perimeter of the launder channel is located a specified distance radially away from the center of the tank and the outer perimeter of the launder channel is located a greater specified distance away from the center of the tank, but is not contiguous with the outer perimeter of the tank. The resulting configuration permits sediment-containing water entering the tank to displace cleaner water which is forced to flow under the baffle plate and over the weir located at the inner perimeter of the launder channel. The configuration further permits sediment-containing water entering the tank to displace cleaner water which is forced to flow under a baffle plate and over a weir located at the outer perimeter of the launder channel. This system is commonly referred to as an inboard launder channel configuration. 
     FIG. 5 also shows a non-circular water treatment tank which can also have an inboard launder channel arrangement. In this configuration, sediment-containing water enters the tank and proceeds to displace the clean water into a plurality of parallel launder channels. Each launder channel has both a weir and a scum baffle plate located at each side of the channel. 
     In the circular tank configuration, the baffle plate and weir, the functions of which will be explained more fully later, are circular in shape when seen in the plan view. As explained previously, they are typically located at the inner and outer perimeters of the launder channel. The displaced clean water ultimately enters the launder channel which 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 launder channel is a serious problem in clarifier tanks. Specifically, as algae builds up on the surfaces of the clarifier tank, particularly on the weirs, it can substantially interfere with the hydraulic flow therethrough. Algae typically adheres to the wet surfaces of the weir and the channel, where it becomes unsightly and odorous. When the launder channel 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. The additional time and cost of manually cleaning the baffle, weir and spillway is compounded by the inboard launder configuration, since the inboard launder configuration typically utilizes two scum baffles, weirs and spillways, as opposed to a single baffle, weir and spillway in a conventional configuration. This results in roughly twice the surface area which needs to be kept free of or cleaned of algae build-up. Furthermore, since the inboard launder channel is centrally located in the tank, rather than along the tank&#39;s outer perimeter, it is difficult for a worker to manually reach the baffles, weirs and spillways in order to clean them by hand, forcing additional expediture of resources to insure the safety for the workers employed for the task. 
     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. No. 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, wherein the launder channel is disposed about the outer perimeter of the tank, 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. An inboard launder configuration is even less suitable for this type of mechanical brush operation, since the inner and outer baffles, weirs and spillways would require, in the circular tank configuration, two mechanical brush systems—one which brushed the inner baffle, weir and spillway from the center of the tank, and a second which rotated around the outer perimeter of the tank in order to reach the baffle, weir and spillway located at the outer perimeter of the launder channel. The non-circular tank configuration, due to its irregular shape as shown in FIG. 5, is also unsuitable for a mechanical brush system. 
     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 inboard 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 an inboard launder channel of a clarifier tank to prevent sunlight from reaching the surfaces of the inboard 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, both weirs, and in some embodiments, over the two scum baffles, of a clarifier tank to prevent sunlight from reaching the surfaces thereof. In accordance with one embodiment of the present invention intended for use with a circular inboard launder channel, one or more panel members having an outer radius of curvature corresponding to the radius of curvature of the inboard launder channel may be employed so that the outer edge of the panel member or members may be arranged in a contiguous fashion along the outer sidewall of the inboard launder channel. The outer sidewall of the inboard launder channel is the sidewall which is located a greater radial distance from the center of the circular clarifier tank, as compared to the inner sidewall of the inboard launder channel, as will be fully explained later. Where a plurality of cover 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 plurality of 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 launder channel configurations. In another embodiment of the present invention, the cover system of the present invention is configured so as to obviate the need for scum baffles, as the cover system accomplishes an identical function as performed by the scum baffle. 
     Referring to the mounting of the panel members in an end-to-end fashion as described above, the adjacent-abutting panel members in another embodiment 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. 
     Typically, water treatment tanks having a circular inboard launder configuration include an influent for sediment-containing water, a pair of scum baffles, a pair of substantially vertical weirs, a pair of spillways, and a launder channel having a sidewall located at its inner perimeter, another sidewall located at its outer perimeter and a width between the two sidewalls. The first of each of the baffles, weirs and spillways are located at the inner perimeter of the launder channel and are configured to allow into the launder channel from the center region of the clarifier tank the clean water which is displaced by the sediment-containing water. The second of each of the baffles, weirs and spillways are located at the outer perimeter of the launder channel and are configured to allow into the launder channel from the peripheral region of the clarifier tank the clean water which is displaced by the sediment-containing water. 
     The present invention comprises a cover panel apparatus positionable over the launder channel, for preventing light from reaching interior surfaces thereof, secured to upper edges of the two sidewalls of the inboard launder channel. The cover panel apparatus comprises a first panel member which is dimensioned and arranged to span the width of said launder channel and is comprised of a substantially opaque material. Additional components of the cover panel apparatus which are suitably attached to the first panel member are also secured to the sidewalls of the inboard launder channel, permitting the first cover panel to be fixedly mounted above the launder channel. Similar to the first cover panel member, a plurality of other panel members are dimensioned and arranged to span the width of the launder channel and are comprised of a substantially opaque material. The plurality of panel members, in addition to being secured to the sidewalls of the launder channel in the same fashion as the first panel member, are secured in end-to-end immediately-adjacent relation to the first panel member and to each other so as to completely cover the launder channel. 
     A further object of the invention is to provide a cover system in which the cover acts to capture noxious gases within the launder channel. The gas is then drawn off or blown out under pressure and sent to a scrubber or to other gas processing apparatus. For this purpose, the joints of the cover must be sealed with a suitable gasket. 
     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 OF THE DRAWINGS 
     In the drawings, wherein like reference numbers denote similar elements throughout the several views: 
     FIG. 1 is a cross-sectional side view of an inboard launder channel showing a cover panel member secured thereon in accordance with one embodiment of the invention; 
     FIG. 2 is a plan view of several straight cover panel members located in an adjacent end-to-end fashion, seperated by fixed corner sections, in accordance with one embodiment of the invention; 
     FIG. 3 is a plan view of several curved cover panel members located in an adjacent end-to-end fashion wherein the cover panel members, in accordance with one embodiment of the invention; and 
     FIG. 4 is a cross sectional side view of two adjacent cover panel members to show the ship-lap type construction in accordance with one embodiment of the invention. 
     FIG. 5 is a plan view of a non-circular inboard launder configuration for a water treatment tank, as employed in accordance with one embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     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  200  of a clarifier or final sedimentation water treatment tank  12 . In the embodiment depicted in FIG. 1, only one of the panel members of system  10  is shown. In accordance with the present invention, numerous panel members can be utilized and secured to launder channel  200 . When installed in the position shown in FIG. 1, the panel members are dimensioned to completely cover launder channel  200 . FIGS. 2 and 3, which will be explained fully later, show plan views of two embodiments of cover system  10 , illustrating two ways in which the panel members of cover system  10  can be configured around an inboard launder channel. 
     As discussed previously, a principal object of the present invention is to prevent the growth of algae on the interior surfaces of launder channel  200 . To this end, each cover panel member  40  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 or 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. 
     In a currently preferred implementation, the individual covers are fabricated from a molded reinforced fiberglass composite. Each molded cover  10  incorporates a cover panel member  40 , and, advantageously, an interior edge surface  30  and an exterior edge surface  50  to facilitate securing the panel member to the clarifier tank. Most preferably, the thickness of the fiberglass panels is in the range of about {fraction (3/16)} to ¾ of an inch, a range that provides substantial structural strength and rigidity while remaining sufficiently light weight for ease of installation. Each panel member 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. Additionally, and as shown in FIG. 1, cover panel member  40  may be arcuate so as not to allow rain and snow to accumulate and puddle thereon. 
     As shown in FIG. 1, launder channel  200  is defined by first and second sidewalls  212   a  and  212   b,  and channel bottom  212   c.  As illustrated, sidewall  212   a  is the inner sidewall, as it is radially closer to the center of tank  12  and thus, is adjacent to interior edge surface  30  of cover panel member  40 . Conversely, sidewall  212   b  is the outer sidewall, as it is radially farther from the center of tank  12  and thus, is adjacent to exterior edge surface  50  of cover panel member  40 . Suitably fastened to first and second sidewalls  212   a  and  212   b,  by any conventional mechanical fastening means, are corresponding first and second weirs  100  and  110 , respectively. Weirs  100  and  110  are typically V-notched at spaced intervals, to permit water flow therethrough. 
     As will be readily appreciated by those skilled in the art, a variety of fastening devices and techniques may be used to secure cover panel members  40  in position over launder channel  200 . In the embodiment shown in FIG. 1, cover support brackets  232  and  234  are upwardly extending from sidewalls  212   a  and  212   b  and fasten to interior edge surface  30  and exterior edge surface  50 , respectively. In the embodiment shown, cover support bracket  232  comprises three sections: a vertical section  232   a  which fastens to interior edge surface  30 , a vertical section  232   c  which fastens to sidewall  212   a,  and an angled section  232   b  for connecting section  232   a  to  232   c.  In a similar fashion, cover support bracket  234  comprises three sections: a vertical section  234   a  which fastens to exterior edge surface  50 , a vertical section  234   c  which fastens to sidewall  212   b,  and an angled section  234   b  for connecting section  234   a  to  234   c.  It can be appreciated that a plurality of cover support brackets  232  and  234  can be disposed around inner and outer sidewalls  212   a  and  212   b  of launder channel  200  at various intervals as desired. The number, size and strength of a plurality of cover support brackets  232  and  234  are determined by conventional mechanical strength analysis and will depend on the weight of the cover panel as constructed and whether the cover panels will be walked on by workers, thereby subjecting the brackets to increased weight loads. Regardless of the number, size and strength of the brackets chosen, however, the brackets should be narrow enough and located at adequate radially-spaced intervals to avoid substantial interference with the hydraulic flow therethrough. It can also be appreciated that cover support brackets  232  and  234  can be replaced by any conventional mechanical support elements in a variety of configurations, as long as the mechanical supporting means utilized secure cover panel system  10  in a position above launder channel  200  and do not substantial interfere with hydraulic flow. 
     In the illustrative embodiment shown in FIG. 1, water level  5  corresponds to the water level in tank  12 . As previously discussed, and as well known in the art, cleaner water is located just below water level  5 , as opposed to sediment-containing water which settles to the bottom of the tank. Water level  5  roughly corresponds to the bottom of the V-notch of weirs  100  and  110 , as water will be displaced through the V-notch of weirs  100  and  110  as additional sediment-containing water enters tank  12 . Not shown in FIG. 1, though usually employed by a clarifier tank and well known in the art, is a scum baffle. A scum baffle typically extends several inches above and several inches below water level  5  and extends along the length of the weir. The scum baffle prevents floatable scum which collects on top of water level  5  from being displaced through the weirs with the cleaner water. As shown, the bottom edges of interior edge surface  30  and exterior edge surface  50  extend below water level  5 . Thus, interior edge surface  30  and exterior edge surface  50  perform the identical function as a scum baffle, and eliminate the need to build, maintain and clean the scum baffle. In the case of the inboard launder channel, which would ordinarily have a scum baffle located adjacent to both the inner and outer sidewalls of the launder channel, the illustrated embodiment eliminates the need for two scum baffles. 
     The top surface of each cover panel member  40  may be provided with handle means  41 , which may protrude from or be recessed in cover panel member  40 , for facilitating the installation, removal or opening of cover panel members  40 . In the embodiment illustrated in FIG. 1, service personnel may easily open covers  40  by hand to access the launder channel for regular scheduled maintenance. In this embodiment, exterior edge surface  30  is rotatably mounted to cover panel  40  by means of a hinge  20 . The end of cover panel  40  opposite interior edge surface  30 , comprising exterior edge surface  50  attached to the edge of panel member  40 , could then be rotatably lifted upward, providing access to launder channel  200 . It should be noted that it is not required that hinge means  20  be located at interior edge surface  30 , but could alternatively be located at exterior edge  50 . In this case, handle means  41  would be located near to interior edge surface  30  and interior edge surface  30  could then be rotatably lifted upward to provide access to launder channel  200 . In the preferred embodiment, hinge means  20  is fabricated from stainless steel to prevent corrosion. 
     The type of hinge  20  used by cover system  10  to rotatably mount interior edge surface  30  to cover panel member  40  is dependent upon the configuration of the cover system. For instance, in the configuration of cover panels shown in FIG. 2, a continuous hinge, extending from one lateral side  31  of a particular cover panel member  40  to the other lateral side  31  of the same cover panel member  40 , can be utilized. In this configuration, hinge means  20  can be located at either interior edge surface  30  or exterior edge surface  50 , as described previously. 
     FIG. 2 shows a plan view of launder channel  200  which, rather than being circular, comprises a plurality of straight sections  21  having an angle ø at the end of each section, relative to an adjacent section  211 , such that all of the sections together enclose a polygon. In this configuration, fixed corner panel sections  25  are positioned over the angled corners formed by launder channel sections  21 , and straight cover panel members  40  are disposed above straight sections  21  of launder channel  200 . 
     Alternatively, in the previously described, circular configuration of cover panels shown in FIG. 3, a short hinge means  20  must be utilized, since the cover panel will open in a clam-like fashion. Preferably, short hinge means  20  would be located centrally at exterior edge surface  50 , an equal distant from each of the two lateral sides  31  of the cover panel. In this embodiment, the lateral sides  31  of the cover panel would not stay closely disposed to interior edge surface  30  in the opened position. In the opened position, only that portion of the cover panel member  40  and interior edge surface  30  which are attached to the centrally located hinge means  20  remain closely disposed to each other. Lateral sides  31  of cover panel member  40  would separate from interior edge surface, thus making a continuous hinge means unpractical. Additionally, and unlike the previously described configuration of cover panels shown in FIG. 2, the circular configuration of cover panels shown in FIG. 3 is not compatible with hinge means located at interior edge surface  30 . 
     As shown in the embodiment illustrated in FIG. 1, a quick release fastener  70  is utilized in order to prevent cover panel  10  from being rotatably lifted unintentionally. Quick release fastener  70  fastens exterior edge surface  50  of cover panel  40  to cover support bracket  234 . Unless quick release fastener  70  is unfastened by the worker, access to launder channel  200  will not be possible. As will be appreciated, any type of removable quick release clips, pins or fasteners may be utilized for this purpose, so long as exterior edge surface  50  may be quickly disengaged from cover support bracket  234  for access when needed. For instance, a pin may be insertable through a hole in exterior edge surface  50  and through a similar sized hole in cover support bracket  234 . It will also be appreciated that any number of pins or fasteners may be utilized with an individual cover panel member  40 . 
     With reference to FIG. 1, it will be seen that the panel members of cover system  10  may be dimensioned and contoured to achieve a contiguous relationship with the interior surfaces of the launder channel and with each other. In the illustrative embodiment of the present invention, launder channel  200  of primary tank  12  has a sidewall configuration which is circular in the plan view (see FIG.  3 ). As seen in FIG. 3, each panel member defines an interior and an exterior edge surface having a radius of curvature corresponding to the radius of curvature of first and second sidewalls  212   a  and  212   b  of launder channel  200 . 
     FIG. 4 shows the ship-lap type joint in accordance with one embodiment of the present invention. To prevent light from entering the channel between adjacent lateral edge surfaces  31  (as shown in FIGS. 2 and 3) of abutting panel members  40 , ship-lap type lateral overlapping joints  1   a  and  2   a  are provided. Shiplap-type joints  1   a  and  2   a  can be integrally molded into each cover panel member  40  so that the adjacent-abutting panel members form a smoothly-continuous surface. Shiplap-type joints  1   a  and  2   a  allow for first lateral side  31  of cover panel member  40  to be secured to next lateral side  31  of adjacent cover panel member  40 , so that together they form a smoothly-continuous surface. The overlapping of lateral sides  31  of cover panel members  40  also prevents unintended leakage or passage of particulate matter through the connection between the immediately-adjacent cover panel members, and eliminates a tripping hazard for workers. 
     FIG. 5 illustrates a non-circular, inboard launder channel configuration. In accordance with one embodiment, the present invention is suitable for use with this tank configuration. Launder channel  200   a,    200   b  and  200   c  each permit water to flow into it over sidewalls  212   a  and  212   b.  Each launder channel  200   a,    200   b  and  200   c  is connected to a main channel into which the clean water collects and flows to the next step in the treatment process. Similar to the other tank configurations previously discussed, the cover panels in this embodiment are supported by and coupled to the upper region of each sidewall, in order to prevent the growth of algae on the interior surfaces of the launder channel. 
     In addition to the principal object of preventing the growth of algae on the interior surfaces of the launder channel, spillway and weir, a further object of the present invention is to control the odor that may emanate from clarifier tank  12 . It is recognized that a large percentage of the noxious gases generated in a settling tank are released as the clarified water spills over weirs  100  and  110 . Accordingly, by capturing these hazardous gases in the launder channel region and drawing them off to a scrubber system or other gas processing apparatus (not shown) or to otherwise dispose of the gases, one is able to reduce the discharges of gases into the atmosphere to an acceptably safe level. 
     As shown in FIG. 1, when interior edge surface  30  and exterior edge surface  50  extend below water level  5 , they act to seal launder channel  200  from the atmosphere. Pipes or ducts may be coupled to the sealed cover system  10  so that a fan or pump (not shown) in operation may draw off the noxious gases to a scrubber system. In this way, noxious gases emitted into launder channel  200  are prevented from being discharged into the atmosphere. 
     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.