Following a thorough site investigation, a biological
Sequential Reactive Barrier (SEREBAR), designed to remove
Polycyclic Aromatic Hydrocarbons (PAHs) and BTEX
compounds, was installed at a Former Manufactured Gas
Plant (FMGP) site. The novel design of the barrier
comprises, in series, an interceptor and six reactive
chambers. The first four chambers (2 nonaerated-2 aerated)
were filled with sand to encourage microbial colonization.
Sorbant Granular Activated Carbon (GAC) was present
in the final two chambers in order to remove any recalcitrant
compounds. The SEREBAR has been in continuous
operation for 2 years at different operational flow rates
(ranging from 320 L/d to 4000 L/d, with corresponding residence
times in each chamber of 19 days and 1.5 days, respectively).
Under low flow rate conditions (320−520 L/d) the majority
of contaminant removal (>93%) occurred biotically within
the interceptor and the aerated chambers. Under high
flow rates (1000−4000 L/d) and following the installation
of a new interceptor to prevent passive aeration, the majority
of contaminant removal (>80%) again occurred biotically
within the aerated chambers. The sorption zone (GAC) proved
to be an effective polishing step, removing any remaining
contaminants to acceptable concentrations before
discharge down-gradient of the SEREBAR (overall removals
>95%).