Effects of zero-valent iron with different particle sizes on micro-aerobic denitrification system

Abstract

A simultaneous partial nitrification, anammox and denitrification(SNAD) micro-aerobic system was constructed. The effects of different particle sizes of ZVI on the micro-aerobic system were investigated from the aspects of operation, microbial performance and community structure by adding 120 mg of zero-valent iron(ZVI) into the system. The results showed that the TIN removal rate of the system stabilized at 83.591% and the electron transport system activity(ETSA) was 1.48 times of the inoculated sludge under the domestication of ZVI with a partical size of 50 nm (50 nZVI), which was higher than the influence of other particle sizes of ZVI. The smaller the particle size, the more production of extracellular polymers promoted by ZVI, the more stable of the activated sludge structure. This was due to the fact that ZVI of smaller particle size was more easily adsorbed and utilized by microorganisms. The results of microbial community analysis showed that the smaller the particle size, the higher the diversity of the microbial community mediated by ZVI, and the more complex the community structure. ZVI mediation promoted the enrichment of microorganisms that were not sensitive to oxygen demand. Candidatus_Brocadia and Candidatus_Kuenenia, two kinds of AnAOB were the main bacteria detected in the samples with the highest abundance of 4.650% and 0.692% under the influence of 50 nZVI. Under nZVI, AnAOB acted together with two facultatively anaerobic denitrifying bacteria, Gemmobacter and norank_f_Comamonadaceae, which constituted the denitrification pathway of SNAD. In contrast, facultatively anaerobic denitrification was the main denitrification pathway mediated by mZVI.

Keywords

• micro-aerobic
• simultaneous partial nitrification anammox and denitrification
• zero-valent iron
• electron transport system activity
• biological denitrification