Phosphorus Removal from Static Sewage Effluent Using Duckweed1
- David L. Sutton and
- W. Harold Ornes2
Dry weights of a mixed population of duckweed (Lemna gibba L. and Lemna minor L.) grown for 2 weeks in 12 liters of 6, 12, and 25% concentrations of secondary treated sewage effluent were 16, 23, and 31% higher, respectively, than plants grown in pond water. Concentrations of sewage effluent > 25% did not increase dry weight production. A maximum yield of 28 g dry weight/m2 was estimated for 7 days beginning with the second week of an 8-week period by removing weekly one-half of the duckweed from containers filled with 760 liters of 100% sewage effluent held under static conditions. Yield dropped to 4.6 g/m2 during the last 7 days of the 8-week growing period. A 97% decrease in orthophosphate phosphorus (P) in the sewage effluent occurred during this time. Phosphorus content of duckweed was directly related to the P content in the sewage effluent up to a concentration of 2.1 µg/ml. Crude protein content of duckweed tissue removed from solutions containing 50 and 100% sewage effluent was almost three times that of plants grown in the pond water. Duckweed harvested 1 week after being planted in the containers filled with 100% sewage effluent under static conditions contained almost four times the crude protein as compared to plants harvested at the end of the 8-week growing period.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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