Optimization of leachate nitrogen removal efficiency of a two-stage SBBCOR

A two-stage sequencing batch biological contact oxidation reactor （Ⅰ/Ⅱ-SBBCOR） was designed to deal with leachate and the difficulties in its biological nitrogen removal. The results showed that the biological contact oxidation process of “segmented + sequencing batch” can reasonably remove nitrogen from leachate. Hydraulic retention time （HRT） plays a crucial role in controlling the loss of biological substrates and biomass within the Ⅰ/Ⅱ-SBBCOR， as well as the timing of nitrification and denitrification reactions. The sequencing batch cycle （SBC） plays a crucial role in controlling substrate concentration gradients， hydraulic shock loads， diverse biological habitats， and microbial activity. Dissolved oxygen （DO） plays a decisive role in controlling the growth activity of nitrifying and denitrifying bacteria in nutrient/microaerophilic/anaerobic environments. Therefore， all the three are significant factors affecting the denitrification efficiency of the Ⅰ/Ⅱ-SBBCOR. The optimal operation condition for Ⅰ/Ⅱ-SBBCOR was as follows： HRT = 6 d/3 d， SBC = 6 h/6 h， DO=2.0 mg/L/2.5 mg/L，respectively. Under this condition， the nutrient ratio of effluent is more reasonable， which is beneficial to subsequent advanced treatment.