Degradation behavior of palm oil mill effluent in Fenton oxidation

•POME degradation behavior in Fenton was studied with carbon and nitrogen balances.•Raw POME consisted of carboxylic acids to cover 88% of organic carbons.•Organics were decomposed to biodegradable acetic, formic, phthalic acids in 15 min.•TOC reduction of 91% was obtained at TOC:H2O2:Fe2+ molar ratio of 1:3.7:0.6. An in-depth study on degradation behavior of palm oil mill effluent (POME) in Fenton oxidation was accomplished with complete carbon and nitrogen balances. Experiments were conducted for real POME with a pH range of 2–5. POME contained high COD (50,000 mg/L), nitrogen (520 mg/L) and phosphorous (510 mg/L). Carboxylic acids and phenol covered 88% of organic carbons while ammonia, NO2− and NO3− contributed for 73% of nitrogen. Most of carboxylic acids and phenol were decomposed forming easily-biodegradable formic, phthalic and acetic acids, and further decomposed to carbonate and gaseous carbon dioxide. Part of carbon in liquid phase in POME transferred to solid phase by oligomerization of aromatic compounds. Ammonia was oxidized to NO2−, NO3− and gaseous N2 while, acetamide degradation led to ammonia formation. 99.9% of phosphorus was removed. Increasing H2O2 concentration elevated organic reduction and the highest TOC reduction of 91% was obtained at TOC:H2O2:Fe2+ molar ratio of 1:3.7:0.6 within 90–180 min which is extremely faster over the available biological treatments. Under the reaction conditions used in this study, Fenton oxidation at pH 3 showed the best result in terms of TOC reduction. Outcomes of this study will provide a platform for advanced oxidation processes and POME treatment.