Influence of biomass acclimation on the performance of a partial nitritation-anammox reactor treating industrial saline effluents

The performance of the partial nitritation/anammox processes was evaluated for the treatment of fish canning effluents. A sequencing batch reactor (SBR) was fed with industrial wastewater, with variable salt and total ammonium nitrogen (TAN) concentrations in the range of 1.75–18.00 g-NaCl L⁻¹ and 112 - 267 mg-TAN L⁻¹. The SBR operation was divided into two experiments: (A) progressive increase of salt concentrations from 1.75 to 18.33 g-NaCl L⁻¹; (B) direct application of high salt concentration (18 g-NaCl L⁻¹). The progressive increase of NaCl concentration provoked the inhibition of the anammox biomass by up to 94% when 18 g-NaCl L⁻¹ were added. The stable operation of the processes was achieved after 154 days when the nitrogen removal rate was 0.021 ± 0.007 g N/L·d (corresponding to 30% of removal efficiency). To avoid the development of NOB activity at low salt concentrations and to stabilize the performance of the processes dissolved oxygen was supplied by intermittent aeration. A greater removal rate of 0.029 ± 0.017 g-N L⁻¹ d⁻¹ was obtained with direct exposure of the inoculum to 18 g-NaCl L⁻¹ in less than 40 days. Also, higher specific activities than those from the inoculum were achieved for salt concentrations of 15 and 20 g-NaCl L⁻¹ after 39 days of operation. This first study of the performance of the partial nitritation/anammox processes, to treat saline wastewaters, indicates that the acclimation period can be avoided to shorten the start-up period for industrial application purposes. Nevertheless, further experiments are needed in order to improve the efficiency of the processes.