Evaluation of Nonionic Surfactant-Enhanced Hydrodynamic Displacement of Fat, Oil, and Grease (FOG) in Wastewater Conduit Analogs

Abstract: FOG accumulation in wastewater conduits presents a persistent operational challenge, typically addressed through high-pressure water jetting with variable efficiency. This study evaluates the effect of a nonionic surfactant, Polysorbate 20, on grease removal under controlled small-scale flow conditions. A confined cylindrical conduit analog was used to simulate distributed FOG adhesion along pipe walls. Replicated trials compared water-only flushing to aqueous solutions containing increasing surfactant concentrations. Grease removal efficiency increased from approximately 4.0% in water-only conditions to 78.8% at the highest surfactant level tested, demonstrating a strong dose-dependent response. These findings support a mechanism in which surfactant-mediated reduction in interfacial tension enhances detachment and transport of hydrophobic deposits.

• 1. Introduction

  The plumbing and wastewater industries rely heavily on mechanical shear—primarily high-pressure water jetting—to clear FOG blockages. However, water’s high surface tension and the hydrophobic nature of grease often result in "hydroplaning," where the jet stream glides over the deposit rather than entraining it. While the use of air-injection (micro-bubbles) and industrial degreasers is known in specialized sectors, there is a lack of localized, technician-level application of micellar science during the jetting process. This study investigates the efficacy of Polysorbate 20 (Tween 20) as a chemical additive to transition the removal process from mechanical displacement to physicochemical emulsification.

  
  

  2. Methodology

  To isolate the chemical variable from mechanical pressure fluctuations, a controlled low-pressure simulation was utilized.

  
  

  Conduit Model: A confined cylindrical analog (conduit) was utilized to simulate a drain line.

  
  

  FOG Composition: A standardized mixture of kitchen grease and porcine lard was mechanically distributed along the internal walls of the conduit to simulate adhered accumulation rather than a single plug.

  
  

  Procedure: * A control group used 20 mL of pure aqueous flushing.

  
  

  Experimental groups used 20 mL of aqueous solution with increasing concentrations of Tween 20 (1, 2, and 3 drops).

  
  

  Each injection was delivered via a standardized three-second plunger stroke to maintain consistent flow velocity.

  
  

  Mass Measurement: The conduit was weighed before and after flushing using a calibrated analytical scale.

  
  

  3. Results

  The data indicates a nearly twenty-fold improvement in removal efficiency when the surfactant was introduced.

  
  

  Table 1: FOG Removal Efficiency by Surfactant Concentration

• Condition Trials Avg.MassRemoved(g) Avg.RemovalEfficiency

  Water Only 4 0.075 g ~4.0%

  1dropTween20 3 0.150 g ~8.3%

  2dropsTween20 3 0.810 g ~44.2%

  3dropsTween20 3 1.453 g ~78.8%

  
  

  4. Discussion

  
  

  4.1 Mechanistic Interpretation

  
  

  The transition from 4.0% to 78.8% efficiency suggests a shift in the dominant removal mechanism.

  
  

  Adsorption: Surfactant molecules align at the grease-water interface, reducing interfacial tension.

  
  

  Wettability: The aqueous solution penetrates the gap between the grease and the conduit wall, weakening the adhesive bond.

  
  

  Micellar Solubilization: At higher concentrations, the grease loses cohesive integrity and detaches as bulk segments rather than individual molecules.

  
  

  4.2 Threshold Behavior

  
  

  The sharp increase in removal between 1 drop (~8.3%) and 3 drops (~78.8%) suggests the presence of a Threshold Concentration, potentially related to the Critical Micelle Concentration (CMC). Above this point, surfactant molecules effectively saturate the interface, enabling rapid detachment.

  
  

  5. Limitations

  
  

  Scale: The conduit model does not fully replicate the turbulent flow regimes and high-head pressures of full-scale jetting systems.

  
  

  Quantification: Surfactant dosing was approximated by drop count rather than precise molarity.

  
  

  Composition: A single grease-to-lard ratio was evaluated; aged or "calcified" FOG may respond differently.

  
  

  6. Conclusion

  The addition of a nonionic surfactant significantly enhances FOG removal in a confined conduit model. These results suggest that integrating surfactants like Polysorbate 20 into professional jetting systems could drastically reduce the time, water volume, and mechanical wear required for drain maintenance.

  
  

  References

  Rosen, M. J., & Kunjappu, J. T. Surfactants and Interfacial Phenomena, Wiley.

  
  

  Tadros, T. Emulsion Formation and Stability, Wiley-VCH.

  
  

  Myers, D. Surfaces, Interfaces, and Colloids, Wiley.

  
  

  U.S. EPA guidance on wastewater FOG management.

  
  

  Interfacial Tension and Wetting Theory, Technical Review.

  
  

  Critical Micelle Concentration in Nonionic Systems, Journal of Colloid Science.

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