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.

Simultaneous removal of C and N from fish effluents in filter reactors: Effect of recirculation ratio on the axial distribution of microbial communities.

We simultaneously removed carbon (C) and nitrogen (N) from fish effluents in compact filter reactors operating at different recirculation ratios (RRs) (2, 10 and without recirculation) to demonstrate microbial coexistence and determine the effect of the RR on the axial bacterial stratification. We also examined the global performance of anoxic, anaerobic and aerobic processes. Microbial communities (bacteria and archaea) were analyzed using 16s rRNA amplification followed by DGGE analyses. Their banding profiles were analyzed using ecological parameters and the most representative bands were sequenced. TOC removal was larger than 98% in the three reactors. The total N removal was 48% for the RR-2 reactor, whereas in the RR-10 reactor, there was no N removal due to the absence of nitrification in the final aerobic step. Coexistence and stratification of microorganisms were observed. The microbial communities were correlated with distinct biochemical processes in each reactor fraction. The RR had a large effect on the distribution of the microbial communities. When the RR increased from 2 to 10, the stratification decreased from 60 to 30%, suggesting a close relationship between reactor performance and the presence of nitrifiers. In the RR-10 reactor, the nitrifier concentration was only 4%. Thus, in combined processes, filter reactors should operate with a moderate RR to favor bacterial stratification and improve performance.

Simultaneous C and N removal from saline salmon effluents in filter reactors comprising anoxic-anaerobic-aerobic processes: effect of recycle ratio.

Salmon processing generates saline effluents with high protein load. To treat these effluents, three compact tubular filter reactors were installed and an integrated anoxic/anaerobic/aerobic process was developed with recycling flow from the reactor's exit to the inlet stream in order to save organic matter (OM) for denitrification. The reactors were aerated in the upper section with recycle ratios (RR) of 0, 2, and 10, respectively, at 30°C. A tubular reactor behave as a plug flow reactor when RR = 0, and as a mixed flow reactor when recycle increases, thus, different RR values were used to evaluate how it affects the product distribution and the global performance. Diluted salmon process effluent was prepared as substrate. Using loads of 1.0 kg COD m(-3)d(-1) and 0.15 kg total Kjeldahl nitrogen (TKN) m(-3)d(-1) at HRT of 2 d, 100% removal efficiencies for nitrite and nitrate were achieved in the anoxic-denitrifying section without effect of the dissolved oxygen in the recycled flow on denitrification. Removals >98% for total organic carbon (TOC) was achieved in the three reactors. The RR had no effect on the TOC removal; nevertheless a higher efficiency in total nitrogen removal in the reactor with the highest recycle ratio was observed: 94.3% for RR = 10 and 46.6% for RR = 2. Results showed that the proposed layout with an alternative distribution in a compact reactor can efficiently treat high organic carbon and nitrogen concentrations from a saline fish effluent with OM savings in denitrification.