Abstract | A proof of concept was performed in order to verify if the coupling of anaerobic and aerobic conditions inside the same digester could efficiently treat a reconstituted whey wastewater at 21 ºC. The sequencing batch reactor (SBR) cycles combined initial anaerobic phase and final aerobic phase with reduced aeration. A series of 24 h cycles in 0.5 L digesters, with four different levels of oxygenation (none, 54, 108 and 182 mgO₂ per gram of chemical oxygen demand (COD)), showed residual soluble chemical oxygen demand (sCOD) of 683 ± 46, 720 ± 33, 581 ± 45, 1,239 ± 15 mg L⁻¹, respectively. Acetate and hydrogen specific activities were maintained for the anaerobic digester, but decreased by 10-25% for the acetate and by 20-50% for the hydrogen, in the coupled digesters. The experiment was repeated using 48 h cycles with limited aeration during 6 or 16 hours at 54 and 108 mgO₂gCOD⁻¹initial, displaying residual sCOD of 177 ± 43, 137 ± 38, 104 ± 22 and 112 ± 9 mg L⁻¹ for the anaerobic and the coupled digesters, respectively. The coupled digesters recovered after a pH shock with residual sCOD as low as 132 mg L⁻¹ compared to 636 mg L⁻¹ for the anaerobic digester. With regard to the obtained results, the feasibility of the anaerobic- aerobic coupling in SBR digesters for the treatment of whey wastewater was demonstrated. |
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