Abstract:
A floway system for a building roof includes a substrate for supporting a periphyton culture that removes nutrient pollution from surface water and isolates the building envelope from solar-induced heat. The substrate is seedable to form a floway. A basin is provided for holding water to be treated, and a pump for pumping water therefrom to the floway inlet. At the floway outlet is positioned an effluent-collection gutter, which channels effluent to a collection vessel. Algal biomass can be harvested. A flexible divider is positioned in the gutter along the long axis, a top edge of securable adjacent the floway outlet so that, during harvesting, algal biomass is scraped into a distal section of the gutter, and thence to a biomass collection basin. The harvester can include a scraper and mechanism for traveling down the floway. The harvester can also move between adjacent floways and to the building roof.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to provisional application Ser. No. 60/847,830, filed Sep. 28, 2006. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to systems and methods for water treatment, and, more particularly, to such systems and methods for water treatment via bioremediation, and, most particularly, to such systems and methods for water bioremediation via periphyton filtration. 
     2. Description of Related Art 
     The use of periphyton cultures to cleanse water needing treatment is well known in the art, for example, with the use of attached colonies of periphyton on sloped floways wherein water is cleansed of pollutants on its journey from an inlet at a top end of the floway to an outlet at a bottom end of the floway. Over time various refinements have been introduced to these systems in order to improve process design. 
     Nonetheless, it is believed desirable to provide additional improvements to periphyton filtration systems and methods that can address, for example, site-specific issues, culture contamination, structural integrity, and algal culture harvesting. 
     SUMMARY OF THE INVENTION 
     The present embodiments of inventions disclosed herein are directed to periphyton filtration systems and methods applicable to a plurality of sites and conditions. In a particular embodiment, a floway system and method are provided for situating on a building roof. 
     A system for water bioremediation of the present invention comprises a substrate adapted for supporting a periphyton culture and for being positioned on a roof of a building. The culture system is thermally coupled to the building interior such that the water temperature of the periphyton culture greatly influences the roof top temperature and provides significant cooling advantage to the buildings solar gain in daytime. The substrate is seedable with a periphyton culture to form a floway and has an inlet and an outlet. A basin is provided for holding water to be treated, and a pump in fluid communication with the basin is provided for pumping water therefrom to the floway inlet. 
     At the floway outlet is positioned a gutter for collecting floway effluent. When in operation, water exiting the floway outlet is channeled to a collection vessel via the gutter. When the floway has matured, algal biomass can be harvested therefrom, for example, with the use of a harvester. 
     In a particular embodiment, a divider is positioned in the gutter along the long axis of the gutter. A top edge of the divider can be secured adjacent the floway outlet so that, during harvesting, algal biomass is scraped into a distal section of the gutter, from which it can be channeled to a biomass collection basin. 
     The harvester can include an articulated scraping means and means for traveling down the floway. The harvester and the gutter can also include means for transporting the harvester between adjacent floways. The system can also include means for transporting the harvester to the building roof. 
     The features that characterize the invention, both as to organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description used in conjunction with the accompanying drawing. It is to be expressly understood that the drawing is for the purpose of illustration and description and is not intended as a definition of the limits of the invention. These and other objects attained, and advantages offered, by the present invention will become more fully apparent as the description that now follows is read in conjunction with the accompanying drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a periphyton roof system. 
         FIG. 2  is a cross-sectional view of the inlet end of the periphyton roof system with a harvester atop the floway. 
         FIG. 3  is a cross-section view of the outlet end of the periphyton roof system with a harvester atop the floway. 
         FIG. 4  is a top perspective view of a thin concrete culture surface with horizontal expansion grid that can be utilized in any periphyton system, including the system depicted in  FIG. 1 . 
         FIG. 5  is a side view of the base as formed using the system of  FIG. 4 . 
         FIG. 6  is a side schematic view of one type of harvesting implement. 
         FIGS. 7 and 8  are side and top plan views of the harvester and carriage system, respectively. 
         FIGS. 9 and 10  illustrate alternate surge devices for all types of periphyton systems, such as that shown in  FIG. 1 . 
         FIG. 11  is a side cross-sectional view of an exemplary calcium reactor. 
         FIG. 12  is a side view of a natural water intake structure capturing nutrients from a bird sanctuary device for use with any periphyton system, such as the roof system disclosed herein. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A description of the preferred embodiments of the present invention will now be presented with reference to  FIGS. 1-12 . As discussed broadly above, the embodiments of the invention are directed to systems and methods of water bioremediation using periphyton filtration techniques. 
     In an exemplary embodiment is provided a periphyton culture system  10  adapted for implementation on a roof  11  of a building  12  ( FIGS. 1-3 ). It has been known in the art to build so-called “green roofs,” which comprise a primary membrane and a secondary containment and drainage system, including gravel and soil as ballast for supporting plants. The plants absorb radiation from sunlight, evapotranspirate water, and perform a cooling function, which can be as high as a 60° F. change (e.g., from 140° F. to 80-90° F. on a roof in Florida in summer). Green roofs can also retain storm water; however, they are known to serve as net contributors of nutrients to surface water. 
     In the present invention, the periphyton roof system  10  is integrated into the building  12  via its external envelope, mechanical, and aesthetic systems. In some buildings, rooftop mechanical components are incorporated into the culture system. Periphyton cultures  13  are synergistic with roofing systems in having similar slopes and impervious membranes  14  to keep water out of the building  12 . While periphyton  13  can be grown directly on the roof  11 , in some embodiments the system  10  can combine the architectural, structural, thermal insulation, and moisture-proofing systems so as to capitalize on synergies. The building  12  is thermally coupled to the water on the floway, thereby providing a cooling effect while radiant heat from the sun is substantially intercepted. Additionally, air from a separate system, inside or outside the building  12 , can be ventilated through an interstitial space  34  above the primary roof  11  and underneath the periphyton culture system  13 . This serves to optimize building cooling during times when the water of the periphyton culture  13  is warmer than ambient air above the periphyton culture system  13 . 
     Preferably, water is pumped  15  onto the roof structure  11  from an inlet basin  16 . The inlet basin  16  can in some embodiments include other features such as fish, macrophytes, and aquatic farming systems for food culture. The inlet basin  16  may be at grade or elevated. The inlet basin  16  may comprise, for example, an existing body of high-nutrient water, such as a lake, an estuary, an ocean, a wetland, a wildlife pond, a water feature, a retention pond, or a created basin, although these are not intended to be limiting. Ozonation as discussed in U.S. Pat. Nos. 6,723,243; 6,860,995; 7,022,232; 6,783,676; and 7,014,767 can also be applied as a pre-filtration step. 
     The water is distributed across the periphyton culture  13  at an inlet end  17  via a distribution element, which can comprise a supply pipe  18 , for example, with a substantially even flow rate, although this is not intended as a limitation. The outlet  19  for each individual floway  22  may have a manual or remotely actuated valve for allowing dewatering of the floway  22  prior to harvest. Effluent water from the culture&#39;s outlet end  19  is ultimately collected in a cleansed state in a vessel or basin, and can be subjected to further filtration and with gravity head potential while elevated. Such a filter  21  can comprise, for example, a diatom or sand filter, although these are not intended as limitations. In another embodiment, the effluent water can be used to feed a hydroponics arrangement as water falls into the outlet vessel. In another embodiment a water wheel generator can be positioned to take advantage of the energy of the elevated water and generate electricity as it falls off the periphyton culture surface and returns to the basin. In the embodiment shown here, the effluent water is channeled back to the inlet basin  16 . 
     As previously mentioned, in the simplest embodiment, the periphyton is grown directly on an enhanced roofing membrane  14 . This membrane  14  can be directly attached to a roof substrate such as lightweight concrete, and is capable of withstanding category  5  hurricane winds. Roofing systems such as the Décor system (Sika Sarnafil, Inc., Canton, Mass.) is one such system that can be used. 
     In further detail of an exemplary embodiment of the system  10 , the floway  22  atop which the periphyton culture  13  is grown is connected to an existing roof structure. In  FIG. 2  is illustrated a building&#39;s parapet  23  and blocking  24 , atop which is positioned cap flashing  25 . Additional flashing  26  has a top end interposed between the cap flashing  25  and the parapet  23 , extends downward behind and under the supply pipe  18 , and runs down into the floway channel. 
     The membrane  14  has a top end  27  positioned between the additional flashing  26  and the parapet  23 , and extends substantially parallel to the parapet  23  and underneath the floway  22 . 
     The floway  22  in this embodiment comprises a precast concrete base  28 , curved upward at the inlet end  17  to meet the supply pipe  18 , having a depth of 4-12 inches. In another embodiment, the concrete base  28 ′ can be formed ( FIGS. 4 and 5 ) atop a liner  29 . A plurality of abutting cells  30 , for example, hexagonal cells, are formed from a compressible material with cold joints therebetween. The cells  30  can have a dimension, for example, of 1 foot from the center to a point and a depth  32  of 1.5 inches. An exemplary material can comprise a plastic such as a high-density polyethylene that is ultraviolet-resistant and foamed, thereby possessing the ability to be easily compressed by expanding concrete. A fiber-reinforced mortar/concrete  33  is poured into the cells  30 , and the base  28 ′ is formed from the cells  30 , which then permit thermal expansion/contraction, a significant advancement over previously used systems wherein at least a 5-inch depth was required with added rebar for tensile strength and calked joints for thermal expansion capability. Clearly, the present system is far less expensive to fabricate, can use less expensive concrete, and weighs far less than prior systems. 
     A drainage layer  34  is positioned beneath the base  28  that can comprise a horizontal drainage mat, which can expand horizontally and thus take up thermal expansion/contraction of the base  28 , thereby preventing undesirable bridging and concurrent vertical displacement and irregular water depth. Beneath the drainage layer  34  is an insulation layer  35 , and beneath that decking  36 . The decking  36  rests atop the building beam  37 . It is important that leakage not be able to enter the building  12 , nor condensation, which can encourage mold growth. A vent is positioned at the upstream end of the drainage layer  34  to obviate any vacuum forming and preventing drainage of water. 
     The periphyton culture  13  is grown on the base  28 , which can have an angle to the horizontal of between 0 and 60 degrees, with a flatter slope believed to be more efficient for culture productivity. In a preferred embodiment, a plurality of floways  22  are positioned in substantially parallel configuration to each other, depending upon available space on the roof  11 . In one embodiment, wherein the algal culture is positioned directly on the roofing membrane, battens are thermally welded to the membrane, which hydraulically separate the floways, allowing them to be harvested while others remain in service. 
     In a particular embodiment, the culture  13  can be adapted for drainage after harvesting algal growth, and for desiccation thereafter to control insect populations that can consume the algae. The periphyton can be pre-seeded to guide speciation towards optimal population for the climate. 
     Harvesting can occur at a climax of the standing crop prior to sloughing or loss of algae, or as mentioned in one of the inventor&#39;s previous patents. Sloughing can be utilized as a means of harvesting whereby the sloughed algae are filtered from the outflow. In the simplest embodiment, and with a specific community of algae, the mature periphyton algae can be simply scraped off the culture surface with a squeegee. Urethane elastomer rubber, as manufactured by Harkness Corporation (Cheshire, Conn.), has been used for squeegee material with superior results in abrasion resistance. As an exemplary embodiment, the hardness ratings can be between 40 A and 60 D, although this is not intended as a limitation. 
     In another particular embodiment, harvesting is accomplished by means of a harvester  40  ( FIGS. 6-8 ) having a conveyor belt  41  driven by spinning drums  42 . The harvester  40  can ride on curbs  43  on the floway  22  atop wheels  44 , with leading-edge scrapers (“squeegees”)  45  that serve to push water and harvested algae  46  ahead of them toward the outlet end  19 . 
     At the outlet end  19  is positioned a gutter system  50  ( FIG. 3 ) that is supported by a gutter support  51 , which is attached at the downstream end  52  via a cast-in embedment  153  into the building  12  positioned beneath the floway  22 . The gutter support  51  extends substantially horizontally away from the building  12  and terminates in an outer wall  54  that extends upwardly to a height approximately equal to that of the floway  22 , forming a valley in which the gutter system  50  resides. 
     The gutter system  50  comprises three sectors  51 - 53 . The first, innermost sector  51 , adjacent the building  12 , collects rain and leakage from the floway  22  and the drainage mat  34 . This is channeled to the outlet pipe  54  ( FIG. 1 ) for, in this case, return to the basin  16 . The second  52  and third  53  sectors are contiguous, and are separable by a hinged flange  55  extending upwardly from the gutter bottom  56 . Prior to harvesting, the flange  55  can be positioned substantially vertically from the bottom  56 ; during harvesting, the flange  55  is bent inwardly to be affixed adjacent the floway  22  to a downwardly depending channeling element  59 . Filtered water from the floway  22  enters the second sector  52  and is channeled to the outlet pipe  54 . Harvested biomass  46  is channeled over the flange  55  and into the third sector  53 , from which it is collected via a biomass pipe  57  into a transport vessel  58 . 
     Once a particular floway  22  is harvested, the harvester  40  can ride on a carriage  60  having wheels  61  that are positioned on rails  62  that in turn are positioned parallel to the gutters  51 - 53  and perpendicular to the floway  22 , to the next floway  22 ′ to be harvested, and moved to the top of that floway  22 ′ so that harvesting can begin ( FIGS. 7 and 8 ). During the carriage transport, the harvester&#39;s belt  41  and drums  42  are elevated to the position illustrated in  FIG. 3 , so that they do not interfere with the carriage wheels. 
     The harvester  40  can be delivered to the roof  11  in a number of ways, such as, for example, a railway-type system  63  via robotic control up the side  64  of the building  12  ( FIG. 1 ). 
     The harvested biomass can be used in a plurality of ways, such as making paper, paper pulp and paper products, textiles, fuels, and feed. Such uses can help offset the cost of operating the system  10 . 
     Another feature of the system  10  includes a surge system for effecting periodic influent surges at the floway inlet  16  ( FIGS. 9 and 10 ) and for serving as intermediate floway weirs. In a particular embodiment ( FIG. 9 ), the surge system  70  can comprise a membrane  71  positionable atop the base  28 , the membrane  71  having a cable  72  threaded through a downstream end  73 . Water  74  can enter the floway  22  atop the membrane  71 , and then the cable  72  can be raised to pull the membrane  71  up, to retain water in the trough  75  formed thereby (dotted line). Then the cable  72  can be lowered so that water in the formed trough  75  is released to flow onto the floway  22 . 
     In an alternate surge system  70 ′ ( FIG. 10 ), instead of a cable  72 , a downstream end  73 ′ of the membrane  71 ′ can be inflatable to form the trough  75 ′ and deflated to release water therefrom. The surge cycle can be automated for a predetermined period, such as, in a range of minutes, although this is not intended as a limitation. These methods are believed superior to those currently known in the art, since the trough water is released more gently, thereby causing less damage to the periphyton culture  13 . 
     An additional feature that can be included in the system  10  comprises a calcium reactor ( FIG. 11 ) positioned along the return path  81  to the inlet basin  16 . Calcium reactors have been used in aquaria to increase levels of depleted minerals including calcium. Exemplary reactors for small flows are manufactured by Schuran Plastics Processing and Seawater Equipment Company (Jülich, Germany). It is well known by those skilled in the art of calcium reactor design that an association of CO 2  and water causes an acidic environment in the presence of calcium carbonate media, which dissolves calcium and other minerals in the media into the water. By this means, CO 2  can be “fixed,” meaning it is incorporated into algal biomass. The present calcium reactor  80  is inexpensive to construct, and provides additional calcium and other missing nutrients to the system for enhancing algal growth. The calcium reactor  80  can comprise an underlying pile of limestone  82  covered with a water-impervious membrane  83 , and having an inlet  84  adjacent the top end  85 . The water level in the calcium reactor is adjustable between a first level  190  and a second level adjacent the bottom  89  of the limestone pile  82  by setting diversion valve  191 , so that the reaction can occur in the wet but drained zone, or in the flooded zone. One or more inlet channels  86  are provided for admitting carbon dioxide into the interstitial spaces in the limestone pile  82  above and below second  89  and first  190  levels. An outlet channel  87  is provided with an inlet  88  thereinto positioned adjacent the bottom  89  of the limestone pile  82 , into which calcium-enhanced water enters for channeling back to the inlet basin  16 . Limestone media can be replenished through a conduit  192 . A re-circulation pump  193  can take water from adjacent the bottom  89  of the limestone pile  82  and distribute it above the inlet channels  86 . 
     Another feature of the system  10  can include a wildlife sanctuary  90  ( FIG. 12 ) for encouraging habitation by aquatic birds  91 . A perch system  92  is positioned in the inlet basin  16  above a flotation hull  93  supported by a flotation ring  94  around its periphery. Water  95  from the inlet basin  16  can enter the water  96  contained in the flotation hull  93  via check valves that can admit, for example, fish  97  as well. The contained water  96  will become higher in nutrients than that  95  in the inlet basin  16  owing to bird deposits, and will therefore enhance algal growth. 
     In this case, water exiting the bottom  98  of the hull  93  is channeled  99  to a well  100  containing a pump  101  for transferring water to the roof  11 . Alternatively, a pump could be positioned outside the well  100  adjacent the hull  93 , with an inlet in fluid communication with the well  100 . 
     A one-acre roof-top periphyton system  10  as described above can remove nitrogen and phosphorus at a rate between 100 and 1000 times that of manmade wetlands, and can be used in an urban setting with a footprint already being taken up by the building  12  and thus adding no further land requirement. The system  10  can removes 60-100 tons of CO 2  per acre per year, as compared with a forested acre, which removes 6 tons of CO 2  per acre per year, and reduces urban heat island effect. 
     In the foregoing description, certain terms have been used for brevity, clarity, and understanding, but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art, because such words are used for description purposes herein and are intended to be broadly construed. Moreover, the embodiments of the system and method illustrated and described herein are by way of example, and the scope of the invention is not limited to the exact details of construction and use. 
     Having now described the invention, the construction, the operation and use of preferred embodiments thereof, and the advantageous new and useful results obtained thereby, the new and useful constructions, and reasonable mechanical equivalents thereof obvious to those skilled in the art, are set forth in the appended claims.