Optimizing volatile fatty acids production from fish canning wastewater: the role of feeding strategies and retention time

Abstract The transition to a circular economy requires innovative strategies for wastewater valorization, particularly in water-intensive sectors, such as fish canning. Anaerobic fermentation of fish canning wastewater to produce volatile fatty acids (VFAs) is a promising alternative to reach this goal. This study evaluated the impact of two bioreactor feeding strategies (continuous (UASB) and sequential batch (SBR)) and two hydraulic retention times (HRT) (6 and 3 days) on VFA yield and product spectrum. The results showed that both feeding modes resulted in high VFA production, exceeding 30 g VFA-COD/L. It can be concluded that the feeding mode has no impact on VFA yield. However, it does exert a significant influence on the product spectrum. Sequential feeding was found to favor butyric acid production, with a 15% higher yield compared to continuous feeding. In contrast, continuous feeding promoted the formation of propionic and valeric acids, with yields 5% and 4% higher, respectively, than those observed under sequential feeding. In contrast, variations in HRT demonstrated no significant impact on either yield or product spectrum. These findings suggest that, for the scaling up of this valorization, the selection of feeding mode should be tailored to the desired objective. Furthermore, a lower HRT (3 days) may lead to financial savings and enhanced productivity without any detrimental impact on yield or product spectrum.