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

Ammonia nitrogen (NH-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 FeO were used to prepare magnetic immobilized carriers by encapsulating microorganisms for the treatment of NH-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 NH-N and 86.7 % of total nitrogen (TN) removal rates from the simulated wastewater (NH-N concentration: 300 mg/L) through nitrification and denitrification under aerobic conditions. Upon applied for a 60 days' treatment of landfill leachate (NH-N concentration of 300 mg/L), the daily removal rates for NH-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.