Comparison of the Effects of Conventional and Alternative External Carbon Sources on Enhancing the Denitrification Process

Abstract

Food industry effluents are considered a potential alternative for methanol when seeking external carbon sources to enhance denitrification in municipal wastewater treatment plants (WWTPs). The aim of this study was to determine the immediate effects of dosing different carbon sources on the denitrification capability of process biomass from the Wschod WWTP in Gdansk (northern Poland). Five carbon sources, including settled wastewater, methanol, and three industrial effluents (distillery, brewery, and fish-pickling process) were tested in two kinds of batch experiments. The acclimation period of biomass to methanol also was investigated in bench-scale systems. During the conventional batch experiments, with the industrial effluents, the observed nitrate utilization rates (NURs) ranged from 2.4 to 6.0 g N/(kg VSS x h), which were only slightly lower than the rates associated with the use of the readily biodegradable fraction in the municipal (settled) wastewater [4.6 to 7.8 g N/(kg VSS x h)]. The conventional NURs observed with methanol and non-acclimated process biomass were low [i.e., 0.4 to 1.5 g N/(kg VSS x h)], and a minimum 2-week acclimation period of biomass to methanol in the bench-scale systems was needed to reach the level of 4.0 g N/(kg VSS x h). In other experiments, dosing the distillery and fish-pickling effluents at the beginning of the anoxic phase (preceded by the anaerobic phase) resulted in considerably higher (over 20%) NURs compared with the same experiments with the other carbon sources.