Role of volume exchange ratio and non-aeration time in spillage of nitrogen in continuously fed and intermittently decanted sequencing batch reactor

The present approach addresses to remove all forms of nitrogen; including recalcitrant dissolved organic nitrogen (rDON) from finally treated effluents. This lab-scale study, suggests that the total nitrogen (TN) removal by continuous fill sequencing batch reactor (cSBR) may not be best as compared to SBR due to spillage of nutrients entered during settling and decantation period. The phenomenon of spillage supported by corresponding dispersion model (plug flow with mild dispersion, 0.081 ± 0.041) and stoichiometric assessment based on balanced chemical equations; revealed that the spill concentration is primarily based on volume exchange ratio, non-aeration out of total cycle time and influent soluble total Kjeldahl nitrogen (TKN). Low C/N ratio acts as limiting factor for denitrification. The C/N ratio was found to be 1.25–6.75 to give TN removals from 35-85%. The average denitrification rate of 0.24 gNO3−removed/gBOD d in cSBR as compared to 0.198 gNO3−removed/gBOD d made cSBR favourable by around 18% (stoichiometrically, 14.2%) just by virtue of availability of more BOD for denitrification due its spillage. However, the spillage of TKN reverted this advantage of cSBR, rendering SBR ahead of it with respect to TN removal.

► Study on effect of hydraulic properties on spill of contaminants.
► Stoichiometry of nitrification and denitrification is performed.
► BOD to nitrogen ratio on nitrogen removal was studied.