In this study, the inhibition of ammonia on anaerobic digestion of butyric acid was evaluated and the potential alleviating effects of such ammonia inhibition by the addition of magnetite particles were investigated. Independent anaerobic batch tests fed with butyric acid as a sole organic source were conducted in twenty 60-mL glass bottles with 10 different treatment conditions, comprising ammonia: 0.5, 2.0, 4.0, 6.0, and 7.0 g total ammonia nitrogen (TAN)/L and magnetite particles: 0 mM and 20 mM. The increase in ammonia concentration did not cause significant inhibition on methane yield; however, a significant inhibition on lag time and specific methane production rate was observed. The IC50 in the control treatments (without magnetite addition) was estimated as 6.2654 g TAN/L. A similar inhibition trend was observed in magnetite-added treatments; however, the inhibition effect by ammonia was significantly alleviated in lag time and specific methane production rate when compared to those in the control treatments. The lag time was shortened by 1.6–46.3%, specific methane production rate was improved by 6.0–69.0%. In the magnetite-added treatments, IC50 was estimated as 8.5361 g TAN/L. This study successfully demonstrated the potential of magnetite particles as an enhancer in anaerobic digestion of butyric acid under conditions of ammonia stress.

Abstract
1. 서 론
2. 재료 및 방법
    2.1. 재료 및 장치
    2.2. 실험방법
3. 결과 및 고찰
    3.1. 부티르산 혐기성 소화에 대한 암모니아의 영향
    3.2. 자철석가루 투입에 따른 부티르산 혐기성 소화에대한 암모니아의 영향
4. 결 론
REFERENCES

• 정성윤(부경대학교 지구환경시스템과학부(환경공학전공)) | Sungyun Jung (Division of Earth Environmental System Science (Major of Environmental Engineering), Pukyong National University, Busan 48513, Korea)
• 김민재(부경대학교 지구환경시스템과학부(환경공학전공)) | Minjae Kim (Division of Earth Environmental System Science (Major of Environmental Engineering), Pukyong National University, Busan 48513, Korea)
• 이준엽(부경대학교 환경공학과) | Joonyeob Lee (Department of Environmental Engineering, Pukyong National University, Busan 48513, Korea) Corresponding author