The present invention relates to a biomass producing system and in particular to a wastewater treatment system using floating aquatic plants for removing pollutants as the water passes through the treatment system. Floating aquatic plants have been used in the treatment of wastewater and/or for improved water quality. For example, plants of the duckweed and liverwort families, water hyacinths, water chestnuts, water lettuce, heartleaf, hydrillas, and azollas have proven effective for water treatment. The duckweed family of plants provides for a biomass producing system wherein unwanted nutrients are harvested from aquatic systems by means of bioaccumulation to treat wastewater and/or improve water quality, and the plants are harvested as a cash crop. Duckweed is particularly suited to this purpose as it is native to most of the world including the United States and has the capability of rapidly taking up nutrients from an aquatic environment to provide a food source with a high nutritional and protein content. The natural development of these plants has produced strains which can grow throughout the year given an open water condition. In addition, these plants have developed a pest resistance which is missing in most other cash crops. Natural resistance to pests provides for a nearly pesticide-free and herbicide-free operation.
The use of small ponds to reduce the fetch, or linear measure of area that the wind acts on to create waves, such that the wave action is minimized, has not proven to be an effective or cost effective means of utilizing the duckweed in wastewater treatment. It has become necessary to provide containment systems for controlling the coverage of the duckweed plants. The use of a containment system also limits the fetch and reduces wave action. Such a system is disclosed in U.S. Pat. No. 4,536,988 to Hogen, dated Aug. 27, 1985 and assigned to the Lemna Corporation. The Hogen patent discloses a containment system for floating aquatic plants. The Hogen system has inherent problems in deployment, in properly containing the Lemna plants, and in withstanding a range of environmental conditions. The Hogen patent also is somewhat difficult to maintain and repair and is not well adapted for differing sizes and shapes of water areas.
An efficient channeling system for containing such a containment system has not been developed. A floating grid system which is easily deployed and easy to maintain is not yet available. Controlling the water temperature and removing dust particles and other harmful debris from the plants has also been proven to be a problem as well as bringing the waste water into contact the floating aquatic plants or treatment organisms and flora.
The present invention solves these and other problems related to using floating aquatic plants and with treatment of wastewater and enabling harvesting as a cash crop, economically.