Anaerobic reactor failure induced by pH and free ammonia nitrogen [FAN] as a potential inhibitor during the treatment of intermediate-stage landfill leachate

Rapid urban growth, rising standards of living, and changing consumption patterns have intensified the generation of Municipal Solid Waste [MSW]. Its improper management in landfills poses a critical environmental pollution and public health problem due to the generation of leachate with high loads of organic and inorganic contaminants. The objective of this research was to evaluate the failure of a UASB reactor treating intermediate stage leachate induced by increases in pH and Free Ammonia Nitrogen [FAN] and to determine the effect on COD removal efficiency and methanogenic activity. Results showed that during Phase IV [days 123–165] with an organic loading rate [OLR] of 2.95 ± 0.1 kg COD/m³·d, COD of 4.22 ± 0.05 g/L, Total Ammonia Nitrogen [TAN] of 1,715 mg/L, and strict pH control [7.06 ± 0.06] the Free Ammonia Nitrogen [FAN] level was maintained at 19 mg/L [a value below the lethal limit], achieving 71.9% COD removal.