The use of fusel oil as an ‘alternative’ carbon source for denitrification in the mainstream and sidestream treatment processes was studied. Research comprised two kinds of batch experiments as well as acclimation of process biomass to external carbon sources. In the conventional nitrate utilization rate (NUR) measurements (one-phase experiments with non-acclimated biomass), the NUR with fusel oil was 1.4–1.7 g N/(kg VSS·h which was comparable to NUR with ethanol and with slowly biodegradable fraction of the settled wastewater. When fusel oil was added at the beginning of the anoxic phase, preceded by an anaerobic phase (in two-phase experiments with non-acclimated biomass), the NURs of 2.5–2.9 g N/(kg VSS·h) were comparable to the tests without the addition of any external carbon sources. The addition of fusel oil and ethanol resulted in a significant enhancement of the denitrification efficiency in lab-scale sequencing batch reactors treating sludge reject water. The NURs continuously increased from below 1 g N/(kg VSS·h) to over 10 g N/(kg VSS·h) over the entire 4-week operational period, indicating gradual acclimation to the substrate. The overall total N removal efficiency reached ∼90%.
Keywords: activated sludge, batch test, denitrification, external carbon source, sidestream treatment