3.3. Other water quality parameters
As displayed in Fig. 2a, the BOD5 content stayed between
3 mg L
−1
and 4 mg L
−1
, while the average CODCrlevel dropped from
about 25.45 mg L
−1
to 10.54 mg L
−1
at the lowest. According to
Fig. 2b, the process resulted in a strong oxidation environment
(ORP between 191.36 mV and 207.83 mV). Especially in tank 5, the
average DO content increased to 10.10 mg L
−1
, which is higher than
the local saturation concentration (7.61 mg L
−1
at 20
◦
C).