Fluidized bed wastewater treatment
AssigneeThe University of British Columbia
InventorsFred A. Koch, Donald S. Mavinic, Noboru Yonemitsu, Ahren T. Britton
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Abstract
A fluidized bed reactor (14) for removing phosphorus and nitrogen from wastewater has a column comprising a number of sections. (15A, 15B, 15C, 15D) The diameter of the column changes stepwise between the sections. A flow velocity in excess of 100 cm/min is maintained in a lowermost one of the sections and lower flow velocities are maintained in subsequent sections. A struvite supersaturation ratio is controlled in part by recycling wastewater from an outlet of the column. Struvite pellets are removed periodically from the bottom of the column.
Claims40
A method for extracting one or both of phosphorus and nitrogen from wastewater, the method comprising:
- introducing the wastewater into a column comprising a substantially vertically oriented conduit having a harvesting section and at least two vertically sequential sections above the harvesting section, wherein a cross sectional area of the conduit increases between adjacent ones of the sections;
- maintaining supersaturation conditions for struvite, a struvite analog, or a phosphate compound in the harvesting section;
- recycling wastewater which has passed through the column while controlling a supersaturation ratio of struvite, a struvite analog, or a phosphate compound in the harvesting section to have a value within a desired range to produce pellets of said struvite, struvite analog, or phosphate compound, wherein controlling the supersaturation ratio is performed at least in part by controlling with a process controller a recycling ratio of a rate at which wastewater is recycled into the column to a total rate at which wastewater is being introduced into the column;
- and,
- extracting from the harvesting section said pellets formed within the column.
A method for extracting one or both of phosphorus and nitrogen from wastewater, the method comprising:
- maintaining supersaturation conditions for a solid reaction product including one or both of said phosphorus and nitrogen in a substantially vertically oriented column;
- introducing the wastewater into the column and allowing particles of the reaction product to form in the column;
- maintaining the particles of the reaction product in a fluidized bed within the column, the fluidized bed spanning at least three vertically sequential zones within the column, wherein wastewater within each of the zones has a different average upward fluid velocity and the average upward fluid velocity is less in vertically higher ones of the zones than in vertically lower ones of the zones;
- allowing said particles to grow to a size sufficient to migrate downward to a harvesting zone comprising at least a portion of a lowermost one of the at least three zones;
- and,
- extracting said particles from the harvesting zone
- wherein maintaining the supersaturation conditions for the solid reaction product in the column comprises recycling wastewater which has passed through the column while controlling a supersaturation ratio of the solid reaction product in a lowermost one of the zones to have a value within a desired range to produce particles of said sufficient size, wherein controlling the supersaturation ratio is performed at least in part by controlling with a process controller a recycling ratio of a rate at which wastewater is recycled into the column to a total rate at which wastewater is being introduced into the column.
Dependencies are inferred from the claim text.