Effective faecal sludge treatment is essential for pathogen reduction and compliance to World Health Organization standards for disposal or reuse. In developing countries, these treatments are frequently absent, ineffective, or immensely expensive. This study used an experimental research design to investigate the efficacy of lactic acid derived from selected vegetable wastes for the treatment of FS collected from an on-site sanitation system. Equal quantities of fresh cabbage, tomato, and carrot wastes were collected, pre-treated, and subjected to lacto-fermentation at 37 ℃ for six days. Daily monitoring of pH and lactic acid concentrations was performed using an electrode pH meter and a UV-Vis spectrophotometer, respectively. Gas chromatography-mass spectrometry (GC-MS) was used to identify lactic acid in the fermented vegetable wastes through a derivatization reaction. FS treatment was performed in four reactors with varying lactic acid ratios (1:1, 1:0.5, 1:0.35), and a control, with Escherichia coli (E. coli) as the pathogen indicator for faecal contamination. E. coli, total solids, volatile solids, and odour levels were monitored over a 16-day treatment period in the four reactors. The fermentation process was deemed successful as indicated by the decrease in pH levels. Successful GC-MS detection of butyl lactate, the derivatized form of lactic acid was observed in the fermented vegetable wastes. Lactic acid concentrations post fermentation were 1.39 ± 0.09 mg/mL, 1.17 ± 0.13 mg/mL, and 1.61 ± 0.34 mg/mL for cabbage, tomato, and carrot wastes respectively. Statistical analysis revealed no significant differences (p > 0.05) in lactic acid concentrations among the vegetable wastes on day six of fermentation. Consequently, cabbage waste-derived lactic acid was selected for subsequent experiments in addition to the local abundance of cabbage waste. Total solids and volatile solids decreased across all the reactors over time. From day four, E. coli was undetectable in reactor 1:1; which also showed the highest reduction in odour levels. Therefore, reactor 1:1 treatment produced the optimal E. coli elimination and odour reduction conditions. This study demonstrates the potential of cabbage waste derived lactic acid for effective FS treatment