| Abstract |
| High-strength ammonia fermentation wastewater contains elevated concentrations of ammoniacal nitrogen and biodegradable organic matter, making stable biological nitrogen removal challenging due to the inhibitory effects of free ammonia (FA) and free nitrous acid (FNA) on nitrifying microorganisms. This study investigated the long-term performance of an integrated self-hydrolysis anaerobic digestion (SHAD)-multistage biological nitrogen removal process for treating real fermentation wastewater and evaluated the relationship between FA/FNA-associated inhibition and nitrification performance. A pilot-scale treatment system consisting of an equalization tank, a SHAD reactor, a pre-denitrification unit, three serial nitrification reactors, a post-denitrification unit, and a re-aeration/settling tank was continuously operated for 124 days. Water quality parameters, including TCODCr, SCODCr, NH3-N, NO2-N, NO3-N, sulfate, and pH, were monitored, while FA and FNA concentrations were calculated using established equilibrium equations. The SHAD reactor achieved an average SCODCr removal efficiency of 58.8% and an average biogas yield of 0.41 m³/kg CODCr removed. During ammonia shock-loading events, influent NH3-N concentrations increased to 3,400 mg/L, resulting in the selective inhibition of nitrite-oxidizing bacteria (NOB) and NO2-N accumulation of up to 990 mg/L in the third nitrification reactor. A significant negative correlation (Pearson's r = -0.81, p < 0.001) was observed between the NH3-N volumetric loading rate and nitrification efficiency. Linear regression analysis indicated that an NH3-N loading rate of approximately 0.32 kg/m³·d corresponded to a nitrification efficiency of 80%. Methanol-assisted post-denitrification removed an average of 77.7% of the residual NO2-N, and stable nitrification performance was recovered within approximately 10-14 days after major ammonia shock-loading events. These findings demonstrate that FA/FNA-based operational analysis provides a practical framework for interpreting nitrification inhibition and establishing engineering criteria for the design and operation of biological treatment systems treating high-strength ammonia fermentation wastewater. |
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| Key Words |
| Anthonisen diagram, Free ammonia, Free nitrous acid, High-strength ammonia wastewater, Nitrification inhibition, Anthonisen 다이어그램, 유리 암모니아, 유리 아질산, 고농도 암모니아성 폐수, 질산화 저해 |
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