Title:
Methods of removing solids from liquids
Kind Code:
A1


Abstract:
A method of removing solid matter from liquid using two or more sets of screening devices installed in series. Each set of screening devices consists of one or more identical or nearly identical screening devices. Each downstream set of screening devices has smaller openings than the preceding upstream set of screening devices. Solid matter collected by the screening devices is automatically discharged onto two or more conveyor systems that deposit the material onto one or more central collection areas for final removal and disposal. The present invention uses screening devices in a special configuration to achieve enhanced removal of solid matter from liquid (i.e. a series installation with screen opening size decreasing in a downstream direction).



Inventors:
Suthard, Clifford James (Vero Beach, FL, US)
Mccully, William Keith (Vero Beach, FL, US)
Application Number:
11/601469
Publication Date:
05/22/2008
Filing Date:
11/17/2006
Primary Class:
Other Classes:
210/159
International Classes:
E02B5/08
View Patent Images:



Primary Examiner:
POPOVICS, ROBERT J
Attorney, Agent or Firm:
SALIWANCHIK LLOYD & SALIWANCHIK;A PROFESSIONAL ASSOCIATION (PO BOX 142950, GAINESVILLE, FL, 32614-2950, US)
Claims:
We claim:

1. A method for collecting objects or materials from a conduit of moving liquid comprising: placing in series, within the conduit, at least two sets of screening devices having self-cleaning apparatuses, such that objects or materials are collected as the liquid flows through the screening devices; removing the collected objects or materials from the screening devices utilizing the self-cleaning apparatuses; and depositing the removed objects or materials onto a conveyor system for transport to one or more collection areas.

2. The method, according to claim 1, wherein the conduit is a channel, canal, or other man-made waterway.

3. The method, according to claim 1, wherein the conduit is a natural flowing waterway.

4. The method, according to claim 1, wherein each set comprises screens of the same or approximately the same size openings.

5. The method, according to claim 1, wherein a series comprises at least two sets, wherein one or more sets having the largest openings are placed in a more upstream position and sets with successively smaller openings are placed further downstream, such that one or more sets having the smallest openings are in the most downstream position.

6. The method, according to claim 5, wherein at least one set is placed facing upstream, substantially perpendicular to the liquid flow.

7. The method, according to claim 5, wherein at least one set is tilted such that the screen face forms an angle of approximately 95° to approximately 140° relative to the liquid flow.

8. The method, according to claim 5, wherein a series comprises at least one downstream set having more screens than an upstream set.

9. The method, according to claim 1, comprising independently operating bar screen devices with self-cleaning apparatuses.

10. The method, according to claim 9, wherein the self-cleaning apparatuses are screen scrapers.

11. The method, according to claim 10, further comprising a dedicated conveyor system for each set of screens for transport of collected objects or materials to a collection site.

12. The method, according to claim 11, further comprising one or more subsidiary conveyor systems for further collecting objects or materials from the dedicated conveyor systems for transport to one or more locations.

13. The method, according to claim 1, wherein the moving liquid comprises industrial fluids, human or animal food-grade fluids, pharmaceutical or biological fluids, stormwater, wastewater, combined sewer overflow, raw water, or industrial flows.

14. The method, according to claim 5, wherein a first set has openings of approximately 1.0 inch and a second set has openings of approximately 0.125 inch.

15. A system for collecting objects or materials from a conduit of liquid moving from upstream to downstream comprising: two sets of bar screen devices arranged in series by successively smaller openings, such that the bar screen set with the largest openings in the most upstream position and consists of four bar screen devices and the bar screen set with the smallest openings is in the most downstream position and consists of six bar screen devices; at least one screen scraper apparatus for automatically cleaning each bar screen device; a conveyor system dedicated to receiving and transporting objects or materials collected from each bar screen by a screen scraper to a collection area; and at least one container at each collection area for receiving objects or materials from each conveyor system.

16. The system, according to claim 15, further comprising at least one subsidiary conveyor system for receiving objects or materials, from each dedicated conveyor system, for transport to one or more collection areas.

Description:

FIELD OF THE INVENTION

This invention relates to the field of fluid screening systems and it discloses a simple and efficient method of screening solid organic and/or inorganic matter from liquids such as, but not limited to, stormwater, wastewater, combined sewer overflow, raw water, and industrial flows.

BACKGROUND OF INVENTION

There is a great need to remove solid matter from flows of liquids in many applications. The United States Congress, through the Clean Water Act Legislation of 1972, began requiring municipalities to remove certain pollutants from stormwater runoff (hereinafter “stormwater” or “runoff”) before it discharges into the nation's waters. Polluting matter that must be removed from stormwater includes, but is not limited to trash and other human produced debris, leaves, tree and bush limbs, and similar pieces of vegetation; aquatic plants, such as hyacinths, water lettuce, duckweed, various grasses and weeds, etc. growing in canals and ditches, etc.

The damage to the nation's waters and their ecosystems by human generated debris is easily apparent. Damage caused by vegetation and other organic matter is not as obvious. As the organic matter degrades in the nation's waters, it releases dissolved nutrients such as nitrogen and phosphorus that cause algae blooms that further damage the receiving water by depleting oxygen and causing fish kills and other harm. The decaying organic matter also creates muck deposits on the bottom of the receiving water, preventing the growth of native aquatic plants that are important for a healthy ecosystem.

There is also a need to remove non-biodegradable debris and organic matter from wastewater before it enters treatment units in a wastewater treatment plant. Non-biodegradable (inorganic) matter is preferably removed from the wastewater before it enters the wastewater treatment units, because it usually cannot be degraded by biological processes and further, may damage equipment in the treatment units.

It is also advantageous to remove as much of the organic load from the wastewater as practical before the wastewater enters the treatment units. The organic matter is biodegradable, meaning it can be reduced and broken down to a molecular level and consumed by various microorganisms, such as bacteria, certain types of algae, and various other single and/or multiple cell organisms. In general, the smaller an organic load to a wastewater treatment plant, the smaller the treatment units need to be, thus reducing the land, equipment, operation, and maintenance costs for the treatment facility.

In developing countries and/or areas with limited technology, a simple method to easily and efficiently remove inorganic and organic matter from wastewater can be beneficial. In these instances, such treatment can be the only wastewater treatment available, but the potential for large reductions of pollutants by the present invention is very significant and can immediately benefit the public health and welfare of such a community.

Another example of a situation that can require removal of solid matter from liquid occurs during large storm events when a sewage collection system is unable to process and/or transmit the combined flow of infiltrating stormwater and the wastewater it normally carries. In such instances, a portion of the mixed stormwater/wastewater flow may be diverted, untreated, away from the wastewater treatment plant into a river, lake, or stream, thereby significantly polluting the nation's waters.

There are many other situations in which it can be desirable or necessary to remove solid matter from various kinds of liquids. A variety of prior art techniques and methods have been devised for this. For example, several patents and published applications describe and claim devices for removing solid matter from liquids, including U.S. Pat. Nos. 6,096,201; 6,616,834; 6,679,994; 6,264,834; 3,865,727; 5,061,380; 5,064,531 and U.S. Published Application Nos. 2001/0047954 and 2001/0040124. However, most of the prior art treatment systems are unable to remove the majority of solid matter from liquids without utilizing multiple, often complex, treatment units. For example, solid matter may be removed down to a certain particle size by one device, but to achieve further reduction in particle size, another, often different and usually more complicated, device must be used. For instance, a screening device followed by a complicated device such as a vortex-type removal system may be required to remove very small particles. Further, these prior art methods and devices are often not as efficient or as cost-effective as the subject application, particularly for large flow rates.

Further, current screening technologies are usually sufficient for relatively low volume flows, but are incapable of properly screening large volume flows, such as stormwater flow rates, sufficiently to prevent overflow. Further, prior art screening techniques and methods often utilize a modified drainage “catch basin” system. For example, U.S. Published Application No. 2004/0232057 describes a series of screens for removing solid matter from liquid. However, it is designed to receive runoff water from surrounding areas before it reaches a channel or canal. The application describes the invention as receiving water at the top of the device that flows downward through a series of screens before draining into a pipe or other conduit. It is not designed to handle large flow rates and volumes, so it could not be placed within a channel or canal. Further, the screens of the device are designed to be manually removed and cleaned when they fill with or become plugged by the captured matter. Until the screens have been cleaned, stormwater or other excess water flows will bypass the screens and the device will not be capable of removing additional matter. Therefore, besides being labor intensive and thus, costly to maintain, the device may not always be capable of capturing the solid matter it is intended to remove from the liquid.

The present invention is able to fulfill a current need for a method to remove solid organic and/or inorganic matter from a liquid in a simple, efficient, and cost-effective manner. The methods and devices of the subject invention can be used in liquids flowing by gravity or moved by mechanical means at any rate or level of movement. The method of the subject invention utilizes devices having the capacity to screen large volumes of fast or slow moving liquid on a continuous basis.

BRIEF SUMMARY

The subject invention provides screening devices and methods of arrangement of the screening device(s) in a new and unique configuration to remove suspended or floating organic and/or inorganic solids from many kinds of liquids under varying flow ranges and suspended solids concentrations. The methods of the subject invention are particularly useful in runoff and/or overflow channels, canals, spillways, or other similarly confined, usually man-made liquid flow conduits or constructions. However, in other embodiments, the subject method and devices could be useful in rivers, streams, and other types of naturally flowing waterways.

One embodiment of the subject invention utilizes at least two sets of screening devices arranged in a series (one in front of another), such that the screen openings or mesh sizes in each set decreases in a downstream direction. In a further embodiment, each series of screening devices can consist of one or more sets of similar (but, usually not identical) screening devices. Further, each set within a series may comprise from one to any desired number of individual screening devices, which can be more or less than the preceding or succeeding set or sets. In a still further embodiment, the screen openings or mesh sizes on each set of screening devices can be of decreasing size with each subsequent downstream set, effectuating a gradual removal of smaller and smaller particles as liquid passes through each subsequent set of screening devices, until the desired solids removal target (with respect to particle size) has been reached.

The present invention provides a method that utilizes screening devices in a manner that improves and greatly simplifies the removal of a variety of organic and/or inorganic solids from any fast or slow moving liquid. The screening method of the subject invention can be utilized for a variety of situations including, but not limited to, stormwater treatment, wastewater treatment and pretreatment, treatment of combined sewer overflow, treatment of raw water for water supply facilities, industrial pollution control applications, or other areas of confined fluid flow, etc.

BRIEF DESCRIPTION OF DRAWINGS

In order that a more precise understanding of the above recited invention be obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered as limiting in scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

FIG. 1 shows a plan view of an embodiment of the subject invention utilizing two sets of screening devices.

FIG. 2 is a cross sectional side view of the embodiment illustrated in FIG. 1.

FIG. 3 shows a top plan view of an alternative embodiment of the subject invention utilizing four sets of screening devices.

FIGS. 4A and 4B are photographs of examples of sets of self-cleaning bar screen devices utilizing a screen rake and installed within a channel or canal.

DETAILED DISCLOSURE

The subject invention in general provides methods for utilizing screening devices for removing solid matter from liquid(s). More specifically, the subject invention pertains to one or more methods of arranging screening devices known in the art, or similar devices, capable of removing a variety of sizes of organic and/or inorganic material from liquids moving at various flow rates. The subject method and devices can reduce or prevent excessive hydrostatic pressure from developing on screens between screen cleaning cycles.

The subject invention is particularly useful in the field of water treatment systems, in particular to methods of using screening devices for the removal of various sized organic and/or inorganic debris or other material from a liquid, such as, by way of non-limiting examples, stormwater, wastewater, combined sewer overflow, raw water, industrial flows, etc. However, a person with skill in the art will be able to recognize numerous other uses that would be applicable to the devices and methods of the subject invention. While the subject application describes methods for screening debris and materials from a liquid, other modifications apparent to a person with skill in the art and having benefit of the subject disclosure are contemplated to be within the scope of the present invention. For example, the subject application describes the removal and disposal of debris from a liquid. However, alternative embodiments can utilize the subject invention as a method of retrieving and/or sorting objects, organisms, or other materials from a liquid. Further, while the subject application describes the use of the devices and methods of the subject invention to clean water, it should be understood that the term “liquid”, as used herein, can comprise any flowing substance, including, but not limited to, industrial fluids, human or animal food-grade fluids, pharmaceutical or biological fluids, etc.

One embodiment of the subject application provides for at least two screening devices and methods of arranging the screening the devices in series, each in front of the other, that are cost effective, simple, and effective for removing solid material from liquids within water runoff channels, storm channels, canals, and other substantially defined, often man-made, waterways or other liquid conduits. The devices and methods of the subject invention are able to screen, capture, and remove organic and/or inorganic solid matter from liquids. Further, the embodiments of the subject invention are able to remove multiple sizes of debris from large debris to particles down to even the micron size range in a simple and unique manner, simply by the utilization and placement of screening devices in the configuration described herein. The configurations of the subject invention can reduce or prevent excessive hydrostatic pressure from developing across screen faces and headloss conditions that are often caused by cumulative matting of debris experienced with prior methods and devices. By gradually removing larger to smaller objects there can be minimal headloss and screen clogging.

With reference to the attached figures, which show certain embodiments of the subject invention, it can be seen that the subject invention utilizes two or more screening devices 19. There are a variety of screening devices known in the art that can be utilized with the subject invention. A person with skill in the art will be able to determine an appropriate screen or similar device suitable for use with the subject invention and the intended field of use. For example, standard industrial liquid filtration screens can be utilized with the subject invention.

In a preferred embodiment, one or more bar screens 4 and 5 are utilized with the subject invention. Bar screens are commonly used for removing organic and/or inorganic material and debris 6, such as, for example, wood, plastic, rags, aquatic plants etc., from liquid. They are known in the art and are often used to filter organic and inorganic solid matter and/or debris 6 from water in relatively defined or confined channels or canals 3, such as, for example, sewers, stormwater run-off channels, river channels, cooling water intakes, manufacturing run-off channels, or other usually man-made liquid conduits, etc. and can protect pumps, and prevent obstruction of other down stream processes.

Bar screening devices have openings 21 between bars, plates, or other parallel members 22, for example, as shown in FIGS. 1 and 3. The openings between parallel members 22 are sized to restrict a variety of solid matter that is larger than the openings and to pass liquid and solid matter of lesser size. The openings of bar screens can be varied and individual bar screens are able to filter large debris or smaller debris often of ⅛ inch and less due to matting effects on the screens. In a preferred embodiment, the subject invention utilizes at least two or more bar screening devices 19 with different size openings, for example as shown in FIG. 3, to restrict multiple sized debris.

The removal of organic or inorganic solid matter and/or debris 6 and trash from the face 23 of screening devices can be labor intensive and costly. Several self-cleaning bar screening devices, such as the one disclosed in U.S. Pat. No. 4,709,804, as well as numerous other types and brands, are known in the art that are able to remove captured material from the face of the screens, so that it is automatically discharged from each screening device. In a preferred embodiment, self-cleaning bar screens are utilized with the subject invention. In a further preferred embodiment, the captured debris material is deposited onto a conveyor system 15 that can be dedicated to each set of bar screening devices 19. In a still further preferred embodiment, the conveyor systems 15 transport and discharge the captured material to one or more central collection areas 16, where material is dumped and/or stored for ultimate disposal. Bar screen cleaning devices are well known in the art and for clarity purposes have not been shown in the drawings of the subject application. A person with skill in the art and benefit of the subject disclosure will be able to determine the appropriate type of bar screening device(s) and/or self-cleaning mechanism(s) therefor that would be appropriate for a particular situation and environment, as well as the type of debris or other material to be collected.

In a preferred embodiment of the subject invention, bar screening devices 19 can be utilized with a screen scraper mechanism (U.S. Pat. No. 5,425,875). A screen scraper apparatus utilizes scrapers or rakes (FlexRake™, Duperon Corp.) for scraping solid matter and/or debris 6 from the face 23 of a screening device 19. Usually, multiple rakes are affixed to a flexible rotating frame positioned against, or in close proximity to, the face of the screening devices. The flexible rotating frame can be continuously turned by a motor, such as, for example, a standard ⅛ horsepower electric motor, which drags the rakes in an ascending direction across the face of a bar screen. Upon reaching the top of the bar screen, material collected on the rakes is deposited on a conveyor 15 positioned at or near the top of, and parallel to, the bar screen, which then carries the deposited material to a collection area 16.

The collection area 16 is a central area for depositing material, objects, debris, etc. collected by and cleaned from the screening devices 19. The collection area 16 can be one or more designated areas at the side of the channel, canal, conduit, etc., where collected material is deposited. In a preferred embodiment, the collection area 16 can comprise any of a variety of containers or receptacles for holding collected material or objects. For example, trash or composting containers can be used when the collected material is organic or inorganic debris. Trash and other material can be removed to a landfill or recycled and organic material, such as vegetation, can be removed and used for composting, fertilizer, animal feed, etc. However, if the screening devices are utilized as a sorting device or for collecting specific objects, then containers or receptacles specific for such use can be positioned in line with the conveyors 15 for depositing therein. For example, if the screening devices are used to sort and/or collect different size fish, or other living organisms, then tanks or other appropriate containers can be positioned in line with the conveyors 15 for depositing the collected organisms.

In preferred embodiments, each set of screening devices 19 has a dedicated conveyor system 15 for carrying the material or objects collected by each screening device to a collection area 16. In alternative embodiments, additional subsidiary conveyors can be used to further direct material or objects from the dedicated conveyors 15 to one or more centralized locations or a single collection area or container.

The unique method of the subject invention utilizes a series 20 of two or more sets of bar screens, 4 and 5, as shown, for example, in FIG. 1. Each bar screen set 4, 5 can comprise one or more bar screens. If a set comprises more than one bar screen, they can be arranged in any configuration suitable for capturing material suspended or floating in a liquid. In a preferred embodiment, the bar screens in a set of multiple bar screens are arranged side-by-side, such that the screen faces 19 are generally parallel and facing upstream of a fluid flow 1. However, alternative embodiments can position the bar screens 4, 5 of each set in a staggered, cantilevered, overlapping, etc. arrangement.

In further embodiments, one or more bar screening devices 19 can be positioned within a fluid flow 1 at any of a variety of angles 30 relative to the flow of the fluid 1, from a generally vertical 90° angle perpendicular to the liquid flow, to a more horizontal angle where the top or bottom of the bar screening device 19 tilts in the direction of the liquid flow. In a preferred embodiment, the bar screening devices 19 are angled such that the top end 32 tilts in the downstream direction of the fluid flow 1. This can facilitate the removal of debris from the face 23 of the screens. However, the angle of placement of one or more bar screening devices 19 can be dictated by the rate of liquid flow 1, the amount of debris 6 or other material to be removed from the liquid, the rate at which the screen faces 23 can be cleaned, etc. Further, each set of bar screening devices 19, or individual bar screening devices within a set 4, 5 can be positioned at different angles. In one embodiment, at least one set of bar screening devices 19 utilized with the methods of the subject invention are positioned within a liquid flow 1 with the top end 32 tilted in the downstream direction, such that the faces 23 of the screen devices 19 can form an angle of approximately 95° to approximately 140° relative to the liquid flow. In alternative embodiments, each set of screening devices is positioned at a unique angle to accommodate different liquid flow conditions.

One embodiment of the method of the subject invention, shown in FIGS. 1 and 2 utilizes a series 20 of two bar screening sets 4 and 5, where the most upstream bar screening set 4 comprises two separate screens 4A and 4B and the more downstream bar screening set 5 comprises three separate screens 5A, 5B, and 5C. In this embodiment, each set 4, 5 of screening devices consists of one or more identical or nearly identical screening devices 19 with faces positioned at angles of approximately 95° relative to the liquid flow. For example, for the first set of screening devices (4) in FIG. 1, two identical or nearly identical screening devices (4A and 4B) are shown mounted parallel and facing the liquid flow, but tilted from vertical relative to the liquid flow. In the second set of screening devices (5) in FIG. 1, three identical or nearly identical screening devices (5A, 5B, and 5C) are shown mounted parallel and facing the liquid flow, but also tilted from vertical relative to the liquid flow. As mentioned above, the number of screening devices necessary in each set (4 or 5) can be a function of various factors, specific to each application.

With regard to FIGS. 1 and 3, a further embodiment of the method of the subject invention utilizes two or more bar screening sets 4, 5 having bar screens of different size openings 21. So, for example, as seen in FIG. 1, screening devices 4A and 4B can have identical sized openings, which are larger than the openings in screening devices 5A, 5B, and 5C, which can also have identical sized openings. The liquid flow 1 containing solid matter 6 is moved by gravity, but alternatively by mechanical means, through an open channel or conduit 3 toward the two sets 4 and 5 of multiple screening devices.

In a preferred embodiment, an upstream screening set 4 has larger openings than the next downstream set 5. For example, in another embodiment, depicted in FIG. 3, four sets 10, 11, 12, and 13 of screening devices 19 can be installed in a series 20 within a channel, or similar liquid flow conduit, with set 10 being the most upstream set, followed by set 11, followed by set 12, followed by set 13. In this embodiment, set 10 has the largest bar screen openings, set 11 has openings smaller than set 10, but larger openings than set 12, set 12 has openings smaller than set 11, but larger than set 13, and set 13 has openings smaller than sets 10, 11, and 12 (i.e. opening size of set 13<12<11<10). In this embodiment, the flow 1 containing solid matter and/or debris 6 is moved usually by gravity, but alternatively by mechanical means, through a channel or open conduit 3 towards several sets 10, 11, 12, and 13 of screening devices 19.

With the method of installation and arrangement of screening apparatuses depicted for this invention, solid matter may easily be removed from a liquid even at high flow rates and large flow volumes. Because they are installed in series with the liquid flow and because downstream screens have smaller openings than upstream screens, the screening devices work collectively as sieves, removing at each step smaller and smaller particles until the desired particle size is removed. This can reduce or prevent excessive hydrostatic pressure from developing across the faces 23 of the screens between cleaning cycles. Therefore, referring to FIG. 1, the solids content of the liquid in area 7 is greater than the solids content of the liquid in area 8, which is greater than the solids content of the liquid in area 9. A further consideration when installing screen sets is the decrease in available liquid surface area that can funnel through a screen as the size of the screen openings decreases. It is well known in the art that as the size of openings in a screen are reduced the available surface area of liquid that can penetrate or funnel through a screen is also reduced. Thus, in certain embodiments, it may be preferable to increase the number of screens downstream or down-flow as the opening sizes decrease. Alternatively, it may be necessary to adjust the number of screens used in a series and/or the size of the openings of the screens to ensure adequate flow through the screens. Thus, for heavy flow rates and/or large debris loads it may be preferable to utilize several generally large opening screen series upstream and gradually reduce screen size openings in more downstream series to prevent head loss and hydrostatic pressure build-up. Bar screens utilized with the subject invention can be any of a variety of sizes and dimensions and have openings of any suitable size. For example, bar screens can have openings capable of screening micron-size particles and organisms to openings of several inches for capturing larger materials and organisms. A person with skill in the art would be able to determine the appropriate number of screens to use and size openings preferred for a given flow rate and expected debris load.

In one embodiment, shown for example in FIG. 1, the most upstream screen set can comprise two bar screens of approximately 1.0 inch openings and a further downstream set can comprise three or more screens having openings of approximately 0.125 inch. By increasing the number of smaller opening screens, it is possible to reduce or eliminate backwash or build-up of headwaters (i.e. headloss). Thus, this embodiment is capable of, but not limited to, treating up to approximately 300 cubic feet per second.

The system depicted is designed to be used to remove solid matter from moving liquids including, but not limited to stormwater, domestic and industrial wastewater, combined sewer overflow, raw water for water supply facilities, etc. The system is particularly suited for areas of confined fluid flow, such as, for example, channels, canals, or other usually man-made conduits. But, it could also be used in a variety of relatively confined or non-confined liquid flow areas, such as for example, rivers, streams, lakes, ponds, oceans, etc. The system can be utilized with liquids moving at any rate of flow by adjusting, if necessary, the number of screens utilized in a series, the size of the openings in the screens, and/or the number of screen series.

The following example illustrates procedures for practicing the subject invention. This example is provided for the purpose of illustration only and should not be construed as limiting. Thus, any and all variations that become evident as a result of the teachings herein or from the following example are contemplated to be within the scope of the present invention.

EXAMPLE 1

Use of Method for Canal Pollution Control System

The Indian River Farms Water Control District (IRFWCD) in Indian River County (IRC), FL is an area of over 53,000 acres that is drained by an extensive network of man-made canals. The IRFWCD discharges into the Indian River Lagoon, an Estuary of National Significance and a St. Johns River Water Management District (SJRWMD) Surface Water Improvement and Management (SWIM) program priority water body. In the East Indian River County Master Stormwater Management Plan, a pollutant loading analysis showed that the three discharge canals of the IRFWCD convey large amounts of suspended solids, nutrients, and floating vegetative debris into the lagoon.

The Main Relief Canal drainage basin has a continuous flow discharge to the Indian River Lagoon that averages approximately 50 million gallons per day. During storm event periods, radial control gates are opened to release flood waters stored in approximately 150 miles of canal and ditch network in the 21,705 acre basin. Gate openings occur approximately 20 times per year and remain open 2,000 to 3,000 hours per year. Discharges following a gate opening can reach 400 cubic feet per second. Tremendous amounts of debris, both organic and/or inorganic, are carried into the Main Relief Canal during these storm event periods.

To combat this problem, a large treatment structure can be constructed in the Main Relief Canal in Vero Beach, Fla. that utilizes a pumped sedimentation sump and a series of self-cleaning bar screens to remove the suspended solids and floating vegetative debris from canal water flowing to the Indian River Lagoon. The structures are designed to treat water draining at approximately 294 cfs from a 21,705-acre basin that is 50% urban and 50% agricultural. The self-cleaning fixed bar screens can utilize a traveling rake system to remove large masses of floating and suspended vegetative debris such as hyacinths, water lettuce, duckweed, and grasses, as well as floating and suspended trash and other material before the water enters the Indian River Lagoon. A sedimentation sump preceding the bar screens can collect settleable solids that can be periodically pumped out. The project is anticipated to reduce Total Suspended Solids (TSS) by approximately 45% (or 906,000 lbs. per year), Total Phosphorus (TP) by 36% (or 11,500 lbs. per year), and Total Nitrogen (TN) by 23% (or 46,800 lbs. per year).

In light of the extremely high construction and energy costs inherent in some currently designed systems, together with the knowledge of the tremendous pollution caused to the Indian River Lagoon by the Main Relief Canal, a stormwater treatment system has been designed that is simple, easy to construct, easy to operate, easy to maintain, requires minimal power cost, and provides similar or improved pollutant removal compared to other treatment systems.

This alternative treatment system is referred to as the “bar screen system” and can utilize two sets of self-cleaning bar screens in series to remove solids from the canal. It can also incorporate a simple sedimentation basin upstream of the bar screens to collect soil particles that are transported along the canal bottom by storm flows. The collected sediment can be removed from the sedimentation basin sump by two horizontal shaft belt-driven centrifugal trash pumps.

The design is unique because it consists of bar screens in series rather than using only a single set. Similar installations using single sets of bar screens, having a single size opening, are in operation in the South Florida Water Management District (SFWMD) and other locations in Florida and nationwide. The SFWMD bar screening system installations have proven to be efficient and simplistic in operation. In the newly designed bar screen system described herein, canal water can be diverted into an off-line treatment channel that contains the bar screening system. The first set of four bar screens can have one-inch openings to remove all particles one-inch in diameter or larger. (Other systems provide, for example, one set of screens with 2-inch openings.) The removed solids can be deposited by the self-cleaning bar screens onto a conveyor that will dump them into a waste collection container for ultimate disposal in the IRC landfill. The first set of bar screens can be followed by a second set of six having ⅛-inch openings. The second set of self-cleaning bar screens will also deposit its solids onto a conveyor that dumps into another waste collection container. The system has the following attributes:

    • Horsepower Requirements—Horsepower requirements are minimal compared to the other systems. For this installation, there can be 10 self-cleaning bar screens, each with a ⅛ Hp motor. There can be two 3 Hp conveyors and two 5 Hp sedimentation removal system pumps. Therefore, with only one sedimentation pump operating at a time, the total required horsepower would be 12.5 Hp, which can be considerably less than other systems. Normally, only the bar screens and conveyors will be operating, representing 7.5 Hp. System operating personnel can manually operate one 5 Hp sediment pump at a time for short periods.
    • Simplicity of Design—The self-cleaning bar screens have proven themselves to be simple and efficient. SFWMD has operated some bar screens in West Palm Beach, Fla. as part of the Everglades restoration project for over 7 years, 24 hours per day, 7 days per week with no downtime due to equipment failure. The design of the subject invention has, as its most complicated piece of equipment, a conveyor system that it is in general easily accessible and relatively easy to repair. The above ground sediment removal pumps can also be located so that they are easily accessible.
    • The bar screen system controls will be the simplest possible. Controls are as follows: (1) The sediment removal pumps can be manually operated with an “on-off” switch; (2) The self-cleaning bar screens can be in operation 24 hours per day, 7 days per week. Each screen can have an “on-off” switch together with standard built-in safety controls. If a large object jams one or more screens, the screen(s) will attempt to un-jam itself three times. If after the third try it is still jammed, the screen will shut down until it is manually restarted. If a conveyor fails, the set of bar screens associated with the conveyor will shut down. (3) Each conveyor can be operated 24 hours per day, 7 days per week and will have a simple “on-off” switch together with safety controls to shut the unit off in the event of a jam. A control system cannot be simpler than this design.
    • Ease of Operation and Maintenance—The bar screen system will be easy to operate and maintain. The self-cleaning bar screens are almost maintenance free and the other equipment is simple in design and easy to repair. Staff time and personnel requirements will be a fraction of that required to operate alternative treatment systems.
    • Pollution Removal Efficiency—It is difficult to quantify the amount of pollutants that the subject bar screen system will remove. Sediment and other solids that are typically carried along the canal bottom during storm flows will deposit in the sedimentation basin and be removed daily or weekly as required, by the sediment removal pumps. IRC assumes that at least 80 percent of the trash, debris, leaves, aquatic plants, etc. that are estimated to be removed by other much more complicated and expensive systems can also be removed by this simple series bar screen design and method. Based on this estimate, approximately 5,000,000 wet pounds of aquatic vegetation alone will be removed.
    • The scraping mechanisms on the self-cleaning bar screens travel very slow, approximately 28 inches per minute. (Although this speed can be increased by utilizing a larger or more powerful motor.) This allows debris to accumulate on the screen before the next cleaning cycle. As debris accumulates, particles smaller than the bar screen opening will be trapped in the pile or matting of material, effecting short-term removal of the smaller particles. In any event, all particles ⅛-inch or larger will be removed, with many particles smaller than ⅛-inch being caught in the temporary mats and removed. Considering the uncertainty that exists with some other solids removal systems' ability to remove floatable solids and the probable sheering of soft material by certain methods, IRC believes this alternate bar screen design will remove at least 80 percent of the materials that some other much more complicated and expensive systems would remove. This represents a removal of 46,800 pounds (dry weight) of total nitrogen per year and 11,500 pounds (dry weight) of total phosphorus per year.

All patents, patent applications, provisional applications, and publications referred to or cited herein are incorporated by reference in their entirety, including all figures and tables, to the extent they are not inconsistent with the explicit teachings of this specification.

It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application.