Treatment of seafood processing wastewater toward carbon neutrality: A comparison between coagulation/flocculation, chemical oxidation and absorbent methods

Seafood processing wastewater contains many organic pollutants and nutrients that harm the environment if discharged without treatment. It is urgent to search for a solution to treat seafood processing wastewater for sustainable development purposes. This study aims to examine the different physico-chemical techniques used in seafood processing wastewater treatment, focusing on their ability to reduce pollutants with the aim of carbon neutrality. This study compares the effectiveness of coagulation-flocculation using Polyaluminium Chloride (PAC)/Anionic Polyacrylamide (APAM), chemical oxidation using Sodium hypochlorite (NaOCl), and adsorption using granular activated carbon (GAC). The results show that coagulation-flocculation with a PAC concentration of 125 mg/L after 30 minutes achieved a removal efficiency of 73.0 % for total suspended solids (TSS), 14.6 % for total dissolved solids (TDS), 65.0 % for chemical oxygen demand (COD), 50.0 % color, 10.0 % total nitrogen (TN), 1.0 % ammonium (NH₄⁺), and 10.0 % total phosphorus (TP). The addition of 62.5 mg/L APAM increased the removal efficiencies to 75.0 % TSS, 15.0 % TDS, 68.0 % COD, 50.3 % color, 10.1 % TN, 1.01 % NH₄⁺, and 10.5 % TP. pH 6.5 was ideal for the pollutant removal efficiencies in seafood processing wastewater using coagulation/flocculation. On the other hand, when using 500 mg/L of NaOCl in chemical oxidation for 15 minutes, it resulted in much lower pollutant removal efficiencies of 11.0 % TSS, 26.0 % COD, 50.0 % color, 6.80 % TN, 35.0 % NH₄⁺, while the TDS removal efficiency was not significant. Finally, using 20 g/L of GAC after 60 minutes recorded removal efficiencies of 75.0 % TSS, 18.0 % TDS, 56.8 % COD, 55.0 % color, 11.9 % TN, 20 % NH₄⁺, and 12.1 % TP. It was found that coagulation-flocculation was the most effective treatment method for seafood processing wastewater treatment when considering both the removal efficiency and cost benefit, at about 0.21 €/m³. These findings will help to develop efficient physico-chemical treatments for seafood processing wastewater with the aim of carbon neutrality.