Effectiveness of Mechanical Aeration in Floating Aquatic Macrophyte-Based Wastewater Treatment Systems
- T. A. DeBusk *,
- K. R. Reddy and
- K. S. Clough
Outdoor tanks containing the floating aquatic macrophyte water hyacinth [Eichhornia crassipes (Mart) Solms] were provided with diffuse aeration to evaluate its effect on wastewater treatment efficiency and plant growth. Light aeration (0.003 and 0.021 L m−2 min−1) had no effect on the treatment of primary domestic effluent in the batch-fed water hyacinth tanks. Heavy aeration (1.03 and 3.53 L m−2 min−1) raised wastewater dissolved oxygen (DO) concentrations, but did not improve biochemical oxygen demand (BOD5) removal efficiency or increase plant growth rates during 21-d experiments. Heavy aeration slightly increased wastewater N removal, but the effectiveness of aeration for nutrient removal was not consistent among experiments. In continuous-flow raceways fed primary domestic effluent, vigorous aeration (6.1 L m−2 min−1) improved effluent quality, with contaminant removal rates averaging 77% (BOD5) and 76% (suspended solids [SS]) in nonaerated raceways, and 94% (BOD5) and 89% (SS) in aerated raceways. Results of this study suggest that the high aeration requirement for enhanced contaminant removal in floating aquatic macrophyte systems (FAMS) is due not only to poor O2 transfer efficiencies (1.6–4.0%), but also to the inefficient utilization of O2 for BOD5 removal. The primary benefit of moderate aeration (0.1–1.0 L m−2 min−1) in FAMS appears to be the elevation of wastewater DO concentrations (from 0.5 to 2.5 mg L−1), which may be useful for controlling odors and mosquito proliferation.
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