Abstract
Nitrogen removal is essential for a successful management approach in a marine recirculating aquaculture system (RAS) through microbial remediation. In this study, two biodegradable polymers, polycaprolactone (PCL) and polyhydroxyalkanoate (PHA), were used as a carbon source and biofilm carrier for marine RAS wastewater treatment. Results showed that the use of an artificial saltwater nitrate (ASN) medium with seeded polymers had a high nitrogen removal efficiency regardless of flow rate, with a nitrate-nitrite removal efficiency of 95.4-98.9%. The TN removal efficiency was greater with PHA (95.1-95.3%) than PCL (86.1-90.1%). TP removal efficiency was greater with the use of PCL (64.1-67.3%) than PHA (48.2-52.5%). The use of marine aquaculture effluent showed an increased TN nutrient removal efficiency with PCL having a removal efficiency of 89%, with an increased TP removal efficiency using PHA (40.4%). Microbial community analysis demonstrated the complexity of microbial consortia within marine RAS. Two major classes identified in our study were Alphaproteobacteria (2-68%) and Flavobacteriia (0.5-58%). We identified Crocinitomix, Oceanicola, Meridianimaribacter, and Ruegeria as potential PCL degraders, while Winogradskyella, Muricauda, Marinobacter, and Alteromonas were identified as potential PHA degraders. The microbial communities responded to varying water chemistry differences and developed unique consortia based on biodegradable polymer types. Biodegradable plastics can be utilized in marine RAS to treat wastewater through microbial processes.
