Denitrification performance and in-situ fermentation mechanism of the wastepaper-flora slow-release carbon source.

[Display omitted] • Wastepaper-flora slow-release carbon was prepared for in-situ fermentation. • The prepared carbon source had self-adaptability to NO 3 –-N concentration. • A stable layered microbial structure was formed by the prepared carbon source. • The presence of the carbon source limited the growth of polysaccharides in sludge. Using wastepaper as external carbon sources is an optional way to achieve total nitrogen removal faced with low carbon to nitrogen ratio municipal sewage. Most of studies have primarily focused on using cellulose-rich wastes establishing the separate denitrification units to achieve in-situ fermentation, which can cause blockages and prolong the process chain. In response, a novel in-situ fermentation wastepaper-flora slow-release carbon source (IF-WF) was proposed using in the original denitrification unit. IF-WF could be efficiently utilized in situ and the denitrification rate increased with the increase of nitrate nitrogen. The fermentation products were highly available, but internal acidification of IF-WF inhibited fermentation. Moreover, IF-WF limited the growth of polysaccharides in the extracellular polymeric substances of denitrified sludge. IF-WF finally formed the structure dominated by nitrate-reduction bacteria outside and cellulose-degrading bacteria inside. These results provide guidance for understanding the mechanism of IF-WF for in-situ fermentation to promote nitrogen removal. [ABSTRACT FROM AUTHOR]