Characterization of seafood processing wastewater: Processing procedures and physicochemical variability

The seafood processing industry produces large volumes of wastewater rich in organic matter, nutrients, and salts, often exceeding legal discharge limits and posing environmental risks. This review introduces a five-stage classification of seafood processing wastewater (SPW), based on key processing operations: initial washings (stage 1), filleting (stage 2), cooking and canning (stage 3), final washings (stage 4), and combined discharge (stage 5). Unlike previous reviews, this structured approach allows for a clearer link between processing steps and pollutant profiles. By adopting this structure, our review addresses a specific gap: the need for a standardized yet detailed framework to understand pollutant load variation across different seafood processing steps. Results show that stage 3 wastewater contain the highest concentrations of BOD, COD, TN, TAN, TP, and oils, followed by stage 2. In contrast, stage 1 and 4 wastewaters carry lower pollutant loads. This categorization enables identification of critical control points and supports the design of stage-specific treatment strategies. The findings highlight the necessity of distinct treatment approaches to improve resource efficiency and reduce environmental impact in seafood processing. This not only improves effectiveness of treatment, but also enables targeted circular economy interventions such as stage-specific recovery and valorisation strategies.