Swine wastewater nitrogen removal at different C/N ratios using the modified Ludzack-Ettinger process

Abstract

The swine industry has been presented strong growth and thus is producing large volumes of effluents that must be correctly management. Nitritation/denitritation process can be used to improve system performance, saving the energy cost with aeration and with the external source of carbon due to the lower C/N requirement. The aim of this study was to evaluate swine wastewater Nitrification/Denitrification (NDF) and Nitritation/denitritation (NDT) processes at different C/N ratios, using the Modified Ludzack-Ettinger (MLE) process, in order to obtain a system with efficient nitrogen removal and low oxygen and carbon consumption. Four phases were conducted during the experiment: Phase I) DO between 2.0-3.0 mg L-1 of O2 and C/N 1.5 (NDF); Phase II) DO between 0.6-0.7 mg L-1 of O2 and C/N 1.5 (NDT); Phase III) DO between 0.6-0.7 mg L-1 of O2, C / N ratios of1.5, 0.9, 0.75 and 0.6 (NDT); Phase IV) DO between 2.0-3.0 mg L-1 of O2, C/N ratios of 1.5, 0.9, 0.75, and 0.6 (NDF). The best operational condition was found in the C / N ratio of 0.9 (Phase III) obtaining an optimum N removal of 86.3%. In this condition, the system saved around 26.8% in total organic carbon consumption and operated at conditions of 74% lower dissolved oxygen when compared to conventional process for N-removal. This strategy can be very useful for nitrogen removal for low carbon swine wastewater as digestate from anaerobic processes.