Ozone Oxidation Catalyzed by Activated Carbon to Remove Ammonia Nitrogen from Simulated Livestock and Poultry Farm Wastewater

Objective Ammonia nitrogen removal from high-concentration livestock and poultry farm wastewater was studied by using powdered activated carbon (PAC) or granular activated carbon (GAC) to catalyze the ozonation process.

Method pH and reaction time in ozone oxidating the simulated wastewater with addition of PAC or GAC as catalysts were optimized. Physiochemical properties of the catalysts were compared by using the Brunauer-Emmett-Teller test (BET), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron paramagnetic resonance (EPR), and infrared spectroscopy (FTIR). Factors and mechanisms associated with the ammonia nitrogen eradication from wastewater were studied.

Results The formation of hydroxyl radicals ^.OH in ozonation was significantly promoted at pH 10. In 84 h, 99.6% of NH₄⁺-N and 73.6% of total nitrogen (TN) were removed from the wastewater with the addition of 40 g PAC·L⁻¹. Those were significantly more than what provided by the added GAC at the same amount. Physiochemically, PAC had greater number of active sites with the larger specific surface area of 238.00 m²·g⁻¹, higher microporous volume of 0.082 cm³·g⁻¹, and more abundant surface oxygen-containing functional groups (i.e., O-H and C-O) than GAC, resulting in efficient oxidation due to the released ·OH from the decomposed ozone. The electron paramagnetic resonance (EPR) showed the free radical production to be more than 5 times higher and last longer (i.e., ＞60 m) than control. Naturally, the extended reaction time would allow further structural change and activity of the catalyst.

Conclusion PAC, more than GAC, significantly promoted the ozonation in the wastewater treatment through adsorption-catalysis synergism.