Kinetics and Removal Efficiency of Nitrogen in Constructed Wetlands Cultivated with Different Plant Species for Treating Swine Wastewater Applied at Different Rates
2021
Fia, Fátima Resende Luiz | de Matos, Antonio Teixeira | Fia, Ronaldo | de Matos, Mateus Pimentel | Borges, Alisson Carraro | Baptestini, Gheila Corrêa Ferres
The present study sought to evaluate the efficiency and kinetics of nitrogen removal in Horizontal Subsurface Flow Constructed Wetlands (HSSF-CWs) cultivated with different plant species used in the treatment of swine wastewater (SWW), under different nitrogen loading rates (LRTKN). For this purpose, nine tanks measuring 2.0 × 0.5 × 0.6 m were used, one maintained without plants (CW₁), while in the others two plant species were evaluated: CW₃, CW₅, CW₇, and CW₉ were planted with Tifton 85 grass (Cynodon spp.) and CW₂, CW₄, CW₆, and CW₈ were planted with cattail (Typha latifolia). The CWs received TKN application rates between 110 and 413 kg ha⁻¹ day⁻¹, and the removal efficiencies ranged from 27.6 to 44.9%. The average mass removal rates (MRR) for TKN and NH₄⁺ ranged from 45.3 to 115.9 kg ha⁻¹ day⁻¹ and 28.9 to 66.5 kg ha⁻¹ day⁻¹, respectively. Tifton 85 grass and cattail contributed, respectively, to 2.22 to 8.7% and 0.03 to 1.67% of the TKN mass removed by the CWs (MRR), equivalent to extraction rates of 2.72 to 4.94 kg ha⁻¹ day⁻¹ and 0.04 to 1.11 kg ha⁻¹ day⁻¹. Coefficients estimated by conventional, modified, and residual first-order models ranged from 0.017 to 0.0187 day⁻¹, 0.0691 to 0.1285 day⁻¹, and 0.0298 to 0.0715 day⁻¹, respectively. The modified first-order model and that with residual, due to their higher R² values (R² > 93%), indicated a good fit and considerable reliability of these equations to describe the processes of nitrogen removal from swine wastewater treated in HSSF-CW, and due to their mathematical simplicity and improvements in the representation of real behavior, they should be preferred for modeling of these systems.
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