Stability of aerobic granular biomass treating the effluent from a seafood industry

The aerobic granular systems represent a good alternative to substitute the conventional activated sludge process in the treatment of industrial effluents due to the lower surface requirements. In this work the effluent from a seafood industry, characterized by a high variability and the presence of residual amounts of coagulant and flocculant reagents, was used to study the development of aerobic granular biomass and its stability. In a first stage with OLRs between 2 and 5 kg COD_S/m³·d the development of aerobic granular biomass was promoted with good physical properties: SVI of 35 mL/g TSS, density of 60 g VSS/L_granule and average diameter of 2.8 mm. In a second stage the continuous change in the OLR applied from 3 to 13 kg COD_S/m³·d, to simulate the real conditions of the industry, showed that the removal of organic matter was not affected (90%) but the aerobic granules disintegrated. The maximum OLR treated in the system without granules disintegration was around 4.4 kg COD_S/m³·d. The nitrogen removal was 30% (for biomass assimilation) and the maximum ammonia removal was around 65% and depending on the solids retention time, the free ammonia concentration and the average granule diameter.