Before ZVI process was combined, the biofilm reactor system for
coking wastewater treatment has been continuously operated for
about 1 year. In the integrated system, HRT for each biofilm reactor
was adjusted to 15 h and the total HRT for the biofilm system was
45 h. In Reactor ZVI, 3–6 l of the biological effluent was retained
for reaction and the excess effluent was discharged. Furthermore,
recirculation of ZVI effluent to Reactor A was employed with the
ratio adjusted to 3. Moreover, the produced sludge in Reactor ZVI
was removed every 2 weeks. In this study, the effluent quality of
each reactor was detected every 2 or 3 days continuously.
To study the stability of the integrated system against the sudden
loading shock of the influent variation, the concentrations of COD
and NH3-N in the influent were increased to a jump change to about
10,000 and 1200 mg l−1 for 24 h. Then, the influent was returned to
the normal level and the effluent quality was detected to examine
the recovery ability of the integrated system.