Effective denitrification from landfill leachate using magnetic PVA/CMC/DE carrier immobilized microorganisms

Ammonia nitrogen (NH₄⁺-N) discharge has caused eutrophication of water bodies and harm to humans and organisms. In this work, polyvinyl alcohol (PVA), sodium carboxymethyl cellulose (CMC), diatomite (DE), and Fe₃O₄ were used to prepare magnetic immobilized carriers by encapsulating microorganisms for the treatment of NH₄⁺-N wastewater. The response surface methodology was used to explore the optimal ratio of the immobilized carriers. The obtained optimal raw material ratio was 99.10 %. The obtained carriers are spherical (4–5 mm in diameter) with a rich honeycombed pore structure. The magnetic carrier improves the ammonia oxidation activity, and the carrier achieved 99.0 % of NH₄⁺-N and 86.7 % of total nitrogen (TN) removal rates from the simulated wastewater (NH₄⁺-N concentration: 300 mg/L) through nitrification and denitrification under aerobic conditions. Upon applied for a 60 days’ treatment of landfill leachate (NH₄⁺-N concentration of 300 mg/L), the daily removal rates for NH₄⁺-N and TN reached 93.7 % and 78.3 %, respectively. The analysis of the microbial community showed that the abundances of heterotrophic nitrifying-aerobic denitrifying bacteria including Enterobacter, Pseudomonas, and Bacillus increased with prolonging treatment days, which accelerated nitrification and denitrification, consequently promoting the nitrogen removal effect.