Remoção de nitrogênio de efluente suinícola a diferentes relações C/N utilizando-se o processo MLE

Abstract

The swine industry has shown strong development and, thus, has produced large volumes of effluents that must be correctly managed. Therefore, when such effluent cannot be released into soil, a treatment must be carried out to avoid environmental impacts of swine wastewater. Nitrogen is one of the elements that takes part in swine waste and it must be under constant evaluation, but, in some cases, it must be removed. Nitrification/denitrification (NDF) process is a frequent applied technology. However, when the effluent presents low C/N ratio, such as effluents after anaerobic processes, there is some decrease on denitrification efficiency and the total nitrogen removal can be affected. In this case, Nitritation/denitritation (NDT) process can be used to improve the system performance as well as save energy cost with aeration and external source of carbon due to the lower C/N requirement. Thus, this study aimed at evaluating swine wastewater based on NDF and NDT processes at different C/N ratios in order to obtain a system with efficient nitrogen removal and low oxygen and carbon consumption. Four phases were carried out during this experiment: Phase I) DO from 2.0-3.0 mgO2L-1 to 1.5 C/N; Phase II) DO from 0.6-0.7 mgO2L-1 to 1.5 C/N; Phase III) DO from 0.6 to 0.7 mgO2L-1, different C/N ratios (1.5, 0.9, 0.75 and 0.6); Phase IV) DO from 2.0 to 3.0 mgO2L-1, different C/N ratios (1.5, 0.9, 0.75, and 0.6). The best operational condition was obtained at nitritation/denitritation process, whose C/N ratio was 0.9, and the optimum N removal was 86.3%. Under this condition, the system saved almost 36.8% of total organic carbon consumption and nearly 74% of dissolved oxygen consumed when compared to the conventional process for N-removal. This strategy can be very useful for nitrogen removal with low carbon rates, as the digestate from anaerobic processes.