A possible method for in situ nitrogen removal in landfills by microbial-pumping-iron behavior

Abstract

Nitrogen pollution from landfills needs urgent treatment. A batch experiment was designed to explore the possible in situ nitrogen removal in landfills based on the hypothesis of microbial-pumping-iron behavior, namely anaerobic microbial iron oxidation and reduction. The results confirm that a simultaneous Fe(II) oxidation, accompanied by nitrate (NO₃⁻-N) reduction and dissimilatory Fe(III) reduction, can happen in aged municipal solid waste (AMSW). This phenomenon can last at least 10 years after landfilling. Organics is an important intermediate medium in that process. The dynamic anaerobic Fe redox cycle has the potential of denitrification without ammonia nitrogen (NH₄⁺-N) accumulation. AMSW with deposited ages of 1–3 years is a good choice to enhance this redox cycle behavior coupled with denitrification. Conversely, AMSW with longer deposited ages (8–10 years) has a quicker iron cycle and a smaller NH₄⁺-N accumulation. This suggests a possible method for in situ nitrogen removal in landfills.