Exploring the Short-Term Effect of an Additional Carbon Source in the Denitrification Coupled to Methane Oxidation Process

Abstract

Abstract This study explores the impact of glucose as a second source of organic carbon on the denitrification coupled to methane oxidation (DOM) process under anoxic conditions. For this purpose, batch tests were conducted varying the C:N ratios to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="0.25 ratio 1" display="inline" overflow="scroll"> <mml:mn>0.25</mml:mn> <mml:mo>∶</mml:mo> <mml:mn>1</mml:mn> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="1 ratio 1" display="inline" overflow="scroll"> <mml:mn>1</mml:mn> <mml:mo>∶</mml:mo> <mml:mn>1</mml:mn> </mml:math> , and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="3.8 ratio 1" display="inline" overflow="scroll"> <mml:mn>3.8</mml:mn> <mml:mo>∶</mml:mo> <mml:mn>1</mml:mn> </mml:math> . During the tests, the removal efficiencies for nitrite, nitrate, methane, and total organic carbon were monitored, and the biomass growth was observed. The highest nitrogen removal efficiency and biomass growth were obtained without glucose, with a C:N ratio of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="0.25 ratio 1" display="inline" overflow="scroll"> <mml:mn>0.25</mml:mn> <mml:mo>∶</mml:mo> <mml:mn>1</mml:mn> </mml:math> , whereas the higher C:N ratios resulted in reduced nitrite and nitrate removal rates, 54.4% and 47.9%, respectively, and lower biomass yield with longer doubling times. These findings suggest that additional organic carbon, such as glucose, may affect DOM activity, for which it is important to emphasize the need of careful control of C:N ratios for sustainable wastewater treatment applications.