Crude glycerol as a carbon source at a low COD/N ratio provides efficient and stable denitritation

Abstract

The efficiency and kinetics of denitritation and sludge production in synthetic wastewater with crude glycerol as a carbon source (COD/N 3.0) and nitrite as a sole nitrogen source were determined. The influence of volumetric exchange ratio n (30, 50, and 70% cycle−1) and cycle length tc (24 and 12 h) on both processes was investigated. Denitritation effectiveness was around 100%. With tc,24 h, denitritation proceeded in fast and slow phases and n increased the process rate. In fast phase, denitritation rate increased from 46.59 to 112.19 mg N-NO2/L h (0.28–0.51 mg N-NO2/mg VSS d). With tc,12 h, process rate increased with n of 30 and 50% cycle−1. At n of 70% cycle−1, denitritation was complete less than 1 h before the end of the 12-h cycle; thus, if nitrite concentration in the influent slightly increased, tc,12 h might be insufficient to complete denitritation. Both n and tc influenced daily biomass production (24.72–111.63 mg MLSS/L d) but did not influence experimentally determined heterotrophic sludge yield YHDexp (0.14 ± 0.02g VSS/g COD).