Combined adsorption and degradation of the off-flavor compound 2-methylisoborneol in sludge derived from a recirculating aquaculture system

- Removal of 2-methylisoborneol (MIB) by sludge derived from an aquaculture system was examined.
- MIB removal in the sludge was driven by combined adsorption and biodegradation.
- Biodegradation of MIB enabled regeneration of the adsorption sites within sludge.
- A model was developed which accurately described MIB removal by the sludge.
- At steady state operation of the reactors, MIB removal was mainly driven by biodegradation.

Off-flavor in fish poses a serious threat for the aquaculture industry. In the present study, removal of 2-methylisoborneol (MIB), an off-flavor causing compound, was found to be mediated by adsorption and bacterial degradation in sludge derived from an aquaculture system. A numerical model was developed which augmented Langmuir equations of kinetics of adsorption/desorption of MIB with first order degradation kinetics. When laboratory-scale reactors, containing sludge from the aquaculture system, were operated in a recirculating mode, MIB in solution was depleted to undetectable levels within 6 days in reactors with untreated sludge, while its depletion was incomplete in reactors with sterilized sludge. When operated in an open flow mode, removal of MIB was significantly faster in reactors with untreated sludge. Efficient MIB removal was evident under various conditions, including ambient MIB levels, flow velocities and sludge loads. When operated in an open flow mode, the model successfully predicted steady MIB removal rates with time. During steady state conditions, most of the MIB removal was found to be due to microbial degradation of the adsorbed MIB. Findings obtained in this study can be used in the design of reactors for removal of off-flavor compounds from recirculating aquaculture systems.

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