2.2. Synthetic feed

Synthetic feed was added as a concentrated stream (2.2 mL/min) diluted with dechlorinated tapwater (4.8 mL/min) to reduce the volume of chemical feed requiring preparation. The net (diluted) feed concentrations are listed in Table 2. Influent ammonia concentrations were gradually increased from 20.5 to 200 mg NH₃–N/L during the startup phase, with the goal of maintaining effluent concentrations in the range 10–30 mg NH₃–N/L to balance the objectives of avoiding both ammonia limitation of nitrification activity and inhibition of AOBs and NOBs due to ammonia toxicity (Anthonisen et al., 1976; Kim et al., 2005; Rusten et al., 1994; Ødegaard et al., 2006). These ammonia concentrations were high relative to domestic wastewater, and were selected to produce highly nitrifying biofilms, with no organic carbon to reduce competition for space from heterotrophs.

- Synthetic feed (based on Hem et al., 1994).