The solution lay is using low odour air from the lamella area located
in the primary treatment works. The existing ductwork system was
modified to allow this air to be supplied directly to the new secondary
treatment works, via two new centrifugal fans.
The
air was supplied to connections on the covers of the BAFF tanks and to
the inlet of the BAFF blowers. The blowers then used this low odour air
as process air to aerate the BAFF tanks.
All
the foul air was then extracted directly from the BAFF tank covers to
the existing odour extract facility located in the primary building.
By recycling the air in this way, no new odour control facility was needed for the secondary works.
It
was necessary however, to supply building ventilation for the occupants
and for any slight leakage from the covers. Supply air enters the
system through a fresh air intake louvre and vertical builders work
plenum. The air is drawn downwards through a silencer mounted
horizontally within the plenum by the supply air-handling unit mounted
at low level. This unit filters the air and heats it as required by an
electric heater battery before it is discharged by the run/standby fans
into the supply air ductwork system.
The
building general extract system is located at low level. Air is
extracted from the whole of the space via a bellmouth intake mounted at
high level. This is then drawn through a silencer and interconnecting
ductwork by the main run/standby extract fans. The air is discharged to
atmosphere through a common header duct and a series of three roof
mounted penthouse type louvers. A silencer is mounted beneath each
louvre reducing noise to the required levels.
The
MCC ROOM has been provided with duty/slave air conditioning units,
which can operate independently or together to provide boost cooling if
required. Each package system consists of a DX under ceiling mounted
fan coil unit and a matched condensing unit. These are located in an
adjacent area below the MCC, and have been specially treated against
corrosion attack by trace elements of H2S gas.
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