The glycerol SBR was inoculated with 1.5 L drum filter slurry from an indoor tilapia breeding farm (Dottignies, Belgium) combined with 1.5 L floc suspension from a flow through batch bio-floc reactor at our lab (5 L, 1 day hydraulic retention time) (Crab et al.,unpublished data). The latter was continuously fed with the same simulated water as mentioned before and with a pulsed daily dose of glycerol to obtain a C/N ratio of 10. During one week, the SBR was fed with glycerol at a C/N ratio of 2.5. After this period, half of the grown microbial biomass present in the reactor was used as inoculum for the acetate SBR which was fed with acetate at a C/N ratio of 2.5. The experiment was initiated following the inoculation of the acetate SBR. Afterwards, the C/N ratio was increased stepwise (Table 1). After changes in the C/N ratio were implemented, the next analysis samples were taken when stable effluent levels of ammonia nitrogen were observed. After the C/N ratio was increased to a final value of 15, increased biofilm growth was observed. Since biofilms also assimilate nitrogen but are not subject to grab sampling, the reactors were completely
cleaned on day 63. The reactors were restarted under the same conditions following day 63 with the biomass not retained on a 1 mm pore-size sieve. The next samples were taken on day 75. This explains the absence of results between days 63 and 75 in Figs. 1 and 2.
The glycerol SBR was inoculated with 1.5 L drum filter slurry from an indoor tilapia breeding farm (Dottignies, Belgium) combined with 1.5 L floc suspension from a flow through batch bio-floc reactor at our lab (5 L, 1 day hydraulic retention time) (Crab et al.,unpublished data). The latter was continuously fed with the same simulated water as mentioned before and with a pulsed daily dose of glycerol to obtain a C/N ratio of 10. During one week, the SBR was fed with glycerol at a C/N ratio of 2.5. After this period, half of the grown microbial biomass present in the reactor was used as inoculum for the acetate SBR which was fed with acetate at a C/N ratio of 2.5. The experiment was initiated following the inoculation of the acetate SBR. Afterwards, the C/N ratio was increased stepwise (Table 1). After changes in the C/N ratio were implemented, the next analysis samples were taken when stable effluent levels of ammonia nitrogen were observed. After the C/N ratio was increased to a final value of 15, increased biofilm growth was observed. Since biofilms also assimilate nitrogen but are not subject to grab sampling, the reactors were completelycleaned on day 63. The reactors were restarted under the same conditions following day 63 with the biomass not retained on a 1 mm pore-size sieve. The next samples were taken on day 75. This explains the absence of results between days 63 and 75 in Figs. 1 and 2.
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