This study determined the minimum nitrogen concentration at which the mesophilic and thermophilic upflow anaerobic filters treating a simulated papermill wastewater could operate efficiently. For this purpose, the chemical oxygen demand (COD) to nitrogen ratio in both digesters was increased in five consecutive steps, from 94 : 5 to 363 : 5. The maximum COD to nitrogen ratios that provided satisfactory operation were 283 : 5 (30mg N/L) and 363 : 5 (23 mg N/L) for the mesophilic and thermophilic reactors, respectively. The nitrogen consumption of bacteria in the thermophilic digester was lower than that in the mesophilic digester. The operational efficiency of the thermophilic digester was higher than that of the mesophilic one regardless of the COD to nitrogen ratio.
Hall ER, Anaerobic treatment of wastewaters in suspended growth and fixed film processes, In Design of anaerobic processes for the treatment of industrial and municipal wastes, J. F. Malina and F.G. Pohland Eds., Technomic Publishing Company, Inc., 1992
Anderson GK, Kasapgil B, Ince O, Environ. Technol., 17(5), 449, 1996
APHA, AWWA, and WEF, Standard methods for the examination of water and wastewater, 21st ed., Washington, D.C., 2005