Duckweed Spirodela polyrrhiza was collected from a pilot-scale
duckweed-based wastewater treatment pond at a swine farm
in Zebulon, North Carolina. Fig. 1 shows the schematic diagram
of the waste management system at the farm. The
duckweed in the pond was harvested once or twice per week
depending on its growth rate. The harvested duckweed plants
(wet size ~5mmeach frond) were air-dried for a week until the
moisture content dropped to around 10% (wet basis). The
dried duckweed plants were ground to pass through a 1 mm
sieve and stored in sealed plastic bags at room temperature.
The chemical composition of the raw dried duckweed
biomass was as follows: total reducing sugar 16.5%, protein
34.5%, lignin 7.5%, and ash 14.7% (dry basis). The chemical
oxygen demand (COD) of duckweed was 1.29 g COD g1 dry
biomass.