Internal vs. External (Alternative) Carbon Sources for Denitrification and EBPR Accomplished by a Full-Scale Process Biomass

The efficiencies of denitrification and enhanced biological phosphorus removal (EBPR) in biological nutrient removal (BNR) activated sludge systems are strongly dependent on the availability of appropriate carbon sources. The aim of this study was to determine the immediate effects of dosing different carbon sources on the denitrification capability and EBPR interactions of a full-scale process biomass from the “Wschod” WWTP in Gdansk (Poland). The settled wastewater (without pretreatment and after coagulation-flocculation) as well as acetic acid, ethanol and by-products from a distillery were tested in three kinds of batch experiments, such as the “conventional” nitrate utilization rate (NUR) measurements, NUR measurements during anoxic P uptake and aerobic respirometric measurements. The removal of colloidal and particulate fractions by coagulation-flocculation resulted in the reduced process rates: up to 30 and 25%, respectively, for the NUR1 and NUR2 during the “conventional” NUR measurements, and up to 60% for the NUR during the anoxic PUR test. In the “conventional” batch experiments, the observed NURs with fusel oil (2.5–2.7 g N/(kg VSS·h) were higher in comparison with pure ethanol. The addition of fusel oil at the beginning of the anoxic phase (preceded by an anaerobic phase) did not appear to affect adversely the parallel P uptake rates and the observed NURs (3.5–4.3 g N/(kg VSS·h)) were comparable to the other examined carbon sources.