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Abstract
Coffee processing wastewater (CPW) contains high organic loads and inhibitory compounds such as caffeine. This study assessed micro-aeration-enhanced anaerobic digestion (MA-AD) for CPW treatment, using oxidation-reduction potential controlled oxygen dosing to compare anaerobic and micro-aerobic regimes. Both MA-AD and conventional anaerobic digestion (AD) achieved similar reductions in total and soluble chemical oxygen demand (COD) and solids (>66 % and >86 %, respectively). However, MA-AD resulted in higher turbidity and total suspended solids, likely due to oxygen-induced floc disruption. pH remained stable (6.8–7.1), though MA-AD showed increased acidification. Caffeine degradation was faster under MA-AD (>85 % in 28 h), while long-term removal rates were similar. Methane production was lower under MA-AD (up to 43 % reduction), likely due to oxygen inhibition of methanogens. MA-AD shows promise for enhancing hydrolysis and removal of recalcitrant compounds in CPW, though further optimization is needed to maintain biogas quality.