Potential of the bivalve Corbicula fluminea for the remediation of olive oil wastewaters

Bioremediation has been arising as a successful wastewater treatment concerning contamination events. Olive oil mill wastewaters (OOMW) are amongst the most concerning industrial wastewaters in the Mediterranean region mainly due to its seasonally intense production volumes, leading to numerous problems in recipient freshwater systems and soils. Bivalves present one of the most attractive solutions to integrate remediation strategies owing to their notable filtration capabilities and often their extensive tolerance to several chemical contaminants. The aim of this study was to explore the potential of Corbicula fluminea, a freshwater invasive bivalve, as a bioremediation agent towards OOMW. In this way, C. fluminea was exposed to a sample of this wastewater, and untreated and biotreated fractions were compared in terms of (i) their chemical composition; (ii) bioaccumulation in bivalve soft tissues and shells; and, finally, (iii) ecotoxicity, using standard organisms (bacteria, microalgae, macrophytes and cladocerans). The clam operated significant removal from OOMW of compounds holding OH and NH groups (e.g. phenols and amides) or C=O, C=C and C=N groups (e.g. protein contents), as well as aliphatic compounds by more than half of the initial levels, as read by FTIR analysis. Corresponding transference into clams' soft tissues can be suggested especially regarding proteins and phosphate groups, with metabolic transformation possibly explaining inconsistencies to some extent; the clam shells were also enriched in compounds bearing carboxyl, hydroxyl and phenol groups, to a lower extent in aliphatic compounds, proteins and polysaccharides, supporting that soft tissues and shells are proper recipients for the olive oil contaminants. Consistently, COD content was reduced by 89% and OOMW toxicity was generally reduced with the biotreatment, remarkably in tests with Lemna minor, where growth rate inhibition decreased from 100% to 60%. Overall, this study presents the first approach linking OOMW with C. fluminea as a potential bioremediation agent, with promising results regarding the use of this bivalve in remediation strategies. (C) 2019 Elsevier Ltd. All rights reserved.