Kinetics of denitrification with crude glycerine as a carbon source in landleachate treatment

Abstract

The effect of COD/N ratio (3–15) on the kinetics and efficiency of nitrogen removal from stabilized landfill leachate with crude glycerine as a carbon source was investigated. Then, using the optimal COD/N ratio, the dependence between kinetic parameters of denitrification and the volumetric exchange ratio (n) (0.1–0.6 cycle–1) was determined. At or above the optimal COD/N ratio of 7, the effectiveness of denitrification was almost 100%. Increasing COD/N ratios above 7 not only did not improve the denitrification rate (ca. 14 mg N-NO3/L∙h and ca. 8 mg N-NOx/L∙h), but also led to higher COD in the effluent. At chosen COD/N ratio of 7, only at n in the range of 0.1–0.3 cycle–1, the denitrification rates depended on n, and increased from 6.4 to 13.6 mg N-NO3/L∙h and from 2.7 to 7.4 mg N-NOx/L∙h. Moreover, increase in each 1 mg N-NO3/L in initial concentration of N-NO3 increased the denitrification rate by 0.18 mg N-NO3/L∙h and 0.09 mg N-NOx/L∙h. Further increases in the n from 0.4 to 0.6 cycle–1 did not substantially increase the rate of denitrification. However, because the denitrification rate remained the same despite the increase in nitrate concentration at the beginning of the SBR cycle, the time needed for complete nitrogen removal increased to 21 h, which means that a 24 h SBR cycle may be too short to ensure process stability.