# Enhancing Wastewater Treatment Efficiency: Utilising Saponification Products for Sustainable Cleaning Processes

## TL;DR

This study shows that soap made from used cooking oil can be safely used in wastewater treatment, supporting microbes and producing biofuel while being cost-effective.

## Contribution

The study introduces a sustainable, low-cost method for wastewater treatment using saponification products from waste oils.

## Key findings

- Soaps from waste oils degrade effectively in both aerobic and anaerobic sludge, producing methane as a biofuel.
- No toxic effects on sludge microorganisms were observed during the treatment process.
- Biosurfactants from used oils cost 0.12–3.0 EUR/kg, significantly cheaper than chemical coagulants or synthetic surfactants.

## Abstract

This study explores the interaction of saponification products with microbial communities in aerobic and anaerobic sewage sludge from wastewater treatment plants (WWTPs). It focuses on the reutilisation of waste cooking oils into soap and evaluates the biodegradation of these products using microbial respiration activity and biological oxygen demand (BOD) as indicators. Results demonstrate that soaps degrade effectively under both aerobic and anaerobic conditions, with anaerobic degradation contributing to methane production—a valuable biofuel. Importantly, no toxic effects on sludge microorganisms were observed. The research highlights that these saponification products can be fully integrated into the wastewater treatment process without adverse effects on microbial dynamics. Moreover, the economic analysis reveals that biosurfactants derived from used oils can be produced at a cost of approximately 0.12–3.0 EUR/kg, significantly lower than the 1–20 EUR/kg typically spent on chemical coagulants or synthetic surfactants used in WWTPs. These findings support the feasibility of repurposing waste oils into environmentally friendly, cost‐effective treatment additives, enhancing microbial performance and promoting circular economy practices in wastewater management.

This study demonstrates the successful utilisation of saponification products derived from used cooking oils to enhance wastewater treatment efficiency. These products support microbial respiration and biofuel production, offering a sustainable approach to waste management and resource recovery within wastewater treatment systems.