Treatment of high loaded swine slurry in an aerobic granular reactor

Aerobic granular sludge grown in a sequential batch reactor was proposed as an alternative to anaerobic processes for organic matter and nitrogen removal from swine slurry. Aerobic granulation was achieved with this wastewater after few days from start-up. On day 140 of operation, the granular properties were: 5 mm of average diameter, SVI of 32 mL (g VSS)⁻¹ and density around 55 g VSS (L_granule)⁻¹. Organic matter removal efficiencies up to 87% and nitrogen removal efficiencies up to 70% were achieved during the treatment of organic and nitrogen loading rates (OLR and NLR) of 4.4 kg COD m⁻³ d⁻¹ and of 0.83 kg N m⁻³ d⁻¹, respectively. However, nitrogen removal processes were negatively affected when applied OLR was 7.0 kg COD m⁻³ d⁻¹ and NLR was 1.26 kg N m⁻³ d⁻¹. The operational cycle of the reactor was modified by reducing the volumetric exchange ratio from 50 to 6% in order to be able to treat the raw slurry without dilution.