Organophosphate pesticides in water/wastewaters in eastern Ethiopia: identification and abatement study using fenton oxidation process

This study focuses on the identification, quantification, and removal of organophosphate pesticides (OPPs) from water/wastewater sources in Haramaya Woreda (Haramaya, Ganda Hayyo, Adele, and Ganda Qallu), Eastern Ethiopia, by utilizing Fenton oxidation processes. HPLC analysis results revealed that profenofos and dimethoate in Haramaya, Ganda Hayyo, and Dangago wastewater samples were above the recommended concentration limits (0.003 mg/L and 0.02 mg/L) set by the WHO, respectively. OPPs in Khat leaves were below EU regulations, except for malathion. The study demonstrates the efficacy of Fenton oxidation in reducing OPP residues in wastewater samples. Profenofos residues in treated samples from Haramaya, Ganda Hayyo, and Adele were significantly reduced to levels below WHO's limits, with removal efficiencies of 97.6%, 92.94%, and 98.93% respectively. Similarly, dimethoate residues in treated samples were reduced below WHO's limits, with removal efficiencies ranging from 97.95% to 98.94%. Overall, OPP residues in treated samples were within EU limits, with average removal efficiencies of 98.6%. Optimization experiments focused on profenofos removal due to its higher prevalence. The study identified optimal values for pH, FeSO 4 .7H 2 O (Fe 2+ ) dose, H 2 O 2 dose, and reaction time of 3.4, 0.7 g/L, 5 g/L, and 42 min, respectively, using ANOVA analysis. A quadratic model predicted a 99.83% profenofos removal under these conditions, with actual reduction exceeding 99.52%. The results of thermodynamic parameters, Gibbs’s free energy (∆Go), enthalpy (∆Ho), and entropy (∆So) study indicated that the removal of profenofos by the Fenton process was spontaneous, endothermic, and the existence by high randomness, respectively. Finally, the economic feasibility of the proposed model was conducted. These findings demonstrate the potential of Fenton oxidation for treating OPP-contaminated water/wastewater leached from Khat farming and other liquid wastes.