Effective partial denitrification of biological effluent of landfill leachate for Anammox process: Start-up, influencing factors and stable operation

Partial denitrification combined with Anammox is a promising approach for simultaneous removal of ammonium and nitrate from wastewaters. In this study, the start-up, influencing factors and stable operation of partial denitrification for treating biological effluent from landfill leachate were investigated. High nitrate loads (3.85 kg N m−3 d−1) and short hydraulic retention time (0.66 h) were obtained in the partial denitrification process, yielding a suitable ratio of NO2−-N/NH4+-N in the effluent for downstream Anammox process. The study also revealed the importance of carbon sources, COD/NO3−-N ratio and salinity in the partial denitrification. Acetate-type carbon source, COD/NO3−-N ratio of about 3.0 and salinity lower than 1% favored high-efficient partial denitrification. The endogenous carbon sources from high-rate partial denitrification sludge contributed to low COD consumption in the process. During the partial denitrification, the dominant genus of Thauera was enriched, and shifted to Pseudomonas with the increase of organic removal rates. [Display omitted] •Partial denitrification of biological effluent of landfill leachate was investigated.•High nitrate load of 3.85 kg N m−3 d−1 and HRT of 0.66 h were achieved.•Carbon sources, COD/NO3−-N ratio and salinity exerted profound effects.•Dominant genus of Thauera shifted to Pseudomonas varying with operating parameters.