Sodium alginate – Tween 20 dispersant for sustainable in-sewer control of fats, oils, and grease (FOG) accumulation

The accumulation of fats, oils, and grease (FOG) in sewer systems presents a significant challenge for water utilities, often necessitating costly interventions such as rehabilitation, unclogging, and pipe recoating. Existing reactive strategies for in-sewer management provide only temporary relief, highlighting the urgent need for a sustainable, proactive solution. This study introduces a novel, environmentally friendly dispersant composed of sodium alginate (SA) and Tween 20 (SAT dispersant) for the effective management of in-sewer FOG deposits, drawing inspiration from oil spill remediation techniques. The SAT dispersant is engineered to achieve a high hydrophilic-lipophilic balance (HLB) and enhanced wettability through the incorporation of hydrophilic functional groups. Characterisation confirmed effective functionalisation, with increased HLB, surface polarity, and demonstrated full deprotonation under alkaline conditions, facilitating synergistic interactions between SA, Tween 20, and Na⁺. Dispersion efficiency, assessed through particle size distribution and apparent viscosity measurements, revealed optimal performance at 8 % Tween 20 and alkaline conditions. For dispersants containing 8 % Tween 20, median particle sizes (D50) were determined as 1.17 ± 0.0 µm at pH 7, 0.24 ± 0.01 µm at pH 9, and 0.21 ± 0.01 µm at pH 12. In addition, apparent viscosity decreased drastically from 357.8 Pa·s to 0.46 Pa·s (99.87 %) at pH 7, 0.19 Pa·s (99.95 %) at pH 9, and 0.06 Pa·s (99.98 %) at pH 12. The dispersion mechanism involves interfacial tension reduction, electrostatic repulsion, and steric stabilisation, ensuring the stable suspension of FOG particles. The SAT dispersant containing 8 % Tween 20 at pH 9 is recommended for field application based on its dispersion efficiency, alignment with typical sewer operating pH, and with regulatory discharge pH limits. Validation using real FOG deposits from a grease interceptor confirmed significant particle size reduction and long-term stability of dispersed FOG. These results establish a proof-of-concept for the application of biopolymer dispersants as a scalable and environmentally friendly strategy for proactive FOG management in sewer systems.