Phytofiltration of anaerobically digested sugarcane ethanol stillage using a macrophyte with high potential for biofuel production.

Anaerobically digested stillage (ADS) requires treatment before being discharged into water bodies or soils to avoid adverse effects. Phytofiltration systems are eco-friendly technologies for wastewater treatment, and they simultaneously serve as a source of biomass for biofuel production. The aim of the present study was to investigate the phytofiltration of ADS using Azolla sp. The effects of the ADS strength (dilutions 1: 50 and 1 : 25 v/v) and initial biomass density (IBD) [15.44 (IBD1) and 23.16 (IBD2) g dry weight (dw) m] on plant growth and pollutant removal were assessed. Productivities obtained at ADS 1: 50 (2.93 and 3.04 g m d for IBD1 and IBD2, respectively) were not significantly different from those of a synthetic medium (2.56 and 3.15 g m for IBD1 and IBD2, respectively). Higher organic matter removal was found using ADS at 1: 25 than that obtained using ADS 1: 50 (52.16-53.34 vs 32.29-38.16%), while no IBD effect was observed. The nutrient concentrations in ADS were reduced significantly, especially the concentrations of NH-N (75.11-82.54%), PO-P (88.72-92.90%) and SO-S (55.95-66.61%). The conversion of nutrients from ADS into Azolla biomass may result in an effective way to produce an attractive feedstock for biofuel production.