Removal of contaminants from wastewater using the bivalve Corbicula fluminea - Comparative assessment of biofiltration and biosorption

Bivalves, such as Corbicula fluminea, and their milled shells have been shown to efficiently remove some compounds from the water, but their ability to remove contaminants of emerging concern, namely pharmaceuticals and stimulants, remains largely unknown. Hence, this study aimed to compare the efficiency of C. fluminea and the corresponding milled shells for removal of 9 common wastewater contaminants at concentrations of 0.5 and 1.0 mg.L^-1, further appraising the entailed ecotoxicity variation. After 24 h, clams removed mainly fluoxetine (≥91 %) and, to a moderate extent, paracetamol (≥26 %). Milled shells removed mainly caffeine (≥49 %), fluoxetine (≥42 %) and naproxen (≥35 % at 0.5 mg.L^-1), after 24 h of contact. Clams were more effective than shells in removing fluoxetine, paracetamol, carbamazepine, metformin and diclofenac whereas the opposite was observed for caffeine and naproxen. Despite this effectiveness, clams and shells had minor effects on ecotoxicity abatement to the microalgae Raphidocelis subcapitata and the bacteria Aliivibrio fischeri, except for fluoxetine. Indeed, the remarkable toxicity reduction to the microalgae exposed to the biofiltered fluoxetine sample matches the pronounced removal %, confirming the beneficial effect of C. fluminea on the quality of water contaminated with this compound. Although biofiltration outperformed biosorption in general, the requirements for clams' maintenance and the risk of spreading this invasive species might constitute a drawback for the use of this species for bioremediation of contaminated wastewaters, highlighting the importance of analyzing the pros and cons of these approaches for each specific application.