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.
iron and some activated carbon (Fe/C = 3). Industrial iron consisted
of filings and shavings which were largely free from visible rust
and retained a metallic glaze. In order to eliminate the adsorption
effect, the activated carbon was saturated with the wastewater
sample before use. In Reactor ZVI, air diffusers and inflators were
used to mix the reaction system. Descriptions about addition and
pretreatment for iron and activated carbon could refer to literature