Denitrification kinetics of simulated fish processing wastewater at different ratios of nitrate to biomass

Abstract

Denitrification was studied in anoxic batch cultures of a simulated fish processing wastewater at 37 r C and pH 7.5, using a denitrifying enrichment culture from fishery wastewater. Different initial nitrate to biomass ratios (So/Xo) were used: nitrate and biomass varied from 7.5 to 94.7 mg NO₃-N l⁻¹, and from 20 to 4300 mg volatile suspended solids l⁻¹, respectively. The specific maximum denitrification rate (r _m) and the cell yield (Y _{X / S}) depended on the So/Xo ratio under anoxic conditions: r _m increased from 1.2 to 1584 mg NO₃-N g⁻¹ VSS h⁻¹ and Y _{X / S} decreased from 42 to 0.03 mg VSS mg⁻¹ NO₃-N when So/Xo varied from 5.5 ⋅ 10^{− 3} to 9.3 mg NO₃-N/mg VSS.

Nomenclature

C_{NO3 − N} nitrate concentration, mg NO₃-N l⁻¹ K _S saturation constant, mg NO₃-N l⁻¹ r _m specific maximum denitrification rate, mg NO₃-N g⁻¹ VSS h⁻¹ So initial substrate concentration, mg l⁻¹ t time, h TOC total organic carbon VSS volatile suspended solids x biomass concentration, g VSS l⁻¹ Xo initial biomass concentration, g VSS l⁻¹ Y _X/S substrate to biomass cell yield, mg VSS/mg N Greek symbols: μ_m maximum specific growth rate of the anoxic microbial population, 1 h⁻¹