The BAF start-up covered a span of about seven weeks without
the addition of ozone, as shown in Fig. 2. The inoculation sludge
from a coke factory was fed to each reactor during the start-up
period.
During the first two-week period, the influent with COD 900–
1100 mg/L and NH4 + AN 138–156 mg/L was obtained by diluting
raw coking wastewater containing about 1800 mg/L COD and
about 300 mg/L NH4 + AN, and then added to the two BAF reactors
to improve the enrichment and acclimatization of the microorganisms.
The two reactors were alternatively emptied and refilled with
diluted wastewater every 2 d. Initially, the dilution was done with
50% tap water and then decreased linearly to zero over the first
two-week period, which was also reflected by the variation of
the influent concentration.