Vertical flow constructed wetland as a green solution for low biodegradable and high nitrogen wastewater: A case study of explosives industry
2021
Madeira, Luís | Carvalho, Fátima | Teixeira, Margarida Ribau | Ribeiro, Carlos | Almeida, Adelaide
The removal of nitrogen compounds from a pretreated explosives wastewater in vertical flow constructed wetland planted with Vetiveria zizanioides (0.24 m² × 0.70 m), filled with light expanded clay aggregates (Leca®NR 10/20), was studied. Experiments under constant hydraulic load, 50 ± 4 L m⁻² d⁻¹ and 83 ± 5 L m⁻² d⁻¹ without and with flooding level (25%), respectively, were made at different ammonium (3–48 mg NH₄⁺-N L⁻¹), nitrate (56–160 mg NO₃⁻-N L⁻¹) and nitrite (0.3–1.1 mg NO₂⁻-N L⁻¹) concentrations. Results indicate that without flooding level (unsaturated) the removal efficiencies obtained were 30 ± 9, 7 ± 1 and 96 ± 2%, respectively to NH₄⁺-N, NO₃⁻-N and NO₂⁻-N. When using flooding level and an external carbon source (C/N ratio from 1.3 ± 0.19 to 2.5 ± 0.20), the organic matter (COD) removal efficiencies were above 90%, 75% for NH₄⁺-N and 55% to NO₃⁻-N. Increasing the C/N ratio from 2.9 ± 0.21 to 4 ± 0.22 did not contributed to upgrade the efficiencies of COD, NH₄⁺-N and NO₃⁻-N removal. The denitrification process was occurred in aerobic conditions and nitrite production have ben occurred, probably due to the presence of aerobic conditions that inhibited partially denitrification.
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