Partial nitritation (SHARON) of nitrogen-rich refinery wastewater with high C/N ratio

In this study, a partial nitritation reactor (SHARON, Single reactor system for High Ammonium Removal Over Nitrite) was used to treat nitrogen-rich wastewater produced by the integrated gasification combined cycle (IGCC) and characterized also by a high organic carbon to nitrogen ratio (C/N up to 1.1 gC/gN). The efficacy of the SHARON reactor in reducing the content of organic matter without compromising ammonium removal was investigated, in view of its coupling with the autotrophic ANAMMOX (ANaerobic AMMonium Oxidation) process. Despite the high influent C/N ratio, the observed ammonium removal efficiency was as high as 54±10%, with a corresponding NO2-N/NH4-N ratio of 1.14±0.42. Moreover, nitrate concentration in the effluent never exceeded 30 mg/L. The organic substrate allowed the development of heterotrophic bacteria, as confirmed by the high observed dissolved organic carbon (DOC) removal efficiency (81±8%); the average C/N ratio in the outlet of the SHARON reactor was 0.1±0.06, and the effluent was suitable for the subsequent treatment by the ANAMMOX process. Such results provide useful preliminary information on the applicability of the SHARON process in combination with ANAMMOX for the treatment of IGCC wastewater as an interesting alternative to currently applied chemical-physical treatments like steam stripping, with potential considerable cost savings.