Methods
2.1. Bacteria and growth condition
Three heterotrophic nitrification–aerobic denitrification bacteria,
named A. tumefaciens LAD9, C. testosteroni GAD3 and A. xylosoxidans
GAD4, were used in the experiment. They were isolated from
the sludge for the treatment of landfill leachate (Chen and Ni,
2011). All the strains were fermented with the synthetic mineral
medium and freeze-dried into powder. The mixture of them
(1:1:1), named PCN bacteria, were used for the inoculation.