Aerobic granules synthesized with EPS and degrading strain Rhodococcus sp. FP1 for industrial wastewater treatment

Background: Aerobic granular sludge-sequencing batch reactors (AGS-SBR) have been introduced as a promising and innovative wastewater treatment system economically outcompeting the conventional activated sludge system. AGS is considered a special case of suspended biofilms, composed of self-immobilized microorganisms that form spherical sludge aggregates. Microorganisms are embedded in a self-produced extracellular polymeric substances matrix thus avoiding the need of any carrier. Many synthetic organic chemicals or metabolites are being released directly into the environment after wastewater treatment processes, which are not conceived to remove them from the effluents. In spite of the AGS tolerance to toxicity, the indigenous microbial communities in biotreatment processes may not be effective in removing recalcitrant pollutants. Bioaugmentation strategies, which consists of adding specific microorganisms to the system can be a solution to overcome the difficulty to eliminate certain compounds in wastewaters. However, it is still not a well-established strategy and deserves attention to become a promising alternative. This work aimed to synthesize strong aerobic granules using EPS (extracted from AGS) and a specialized bacterial strain capable of degrading 2-fluorophenol, with the aid of specific substances to increase the cross-linking potential of EPS. Conclusions: Substance 1 was not efficient in improving the strength of the granules, due to concentration or inability to promote the crosslinking of EPS; Granules from mixture 6 were the most similar in terms of strength to the Utrecht granules. The source of EPS affected the strength of the granules, even with conditions similar to mixture 6 Control beads from mixture 7 showed to be weaker than the ones from mixture 6, reinforcing that EPS was a key component to increase the strength of the produced granules. EPS composition and concentration are important to produce strong granules that can be further used in bioaugmentation.