| (a) Application Rates.
(1) With one unit out of service, the peak application
rate to any multi-compartmented, low head, automatically backwashed
(multi-compartmented) filter unit must not exceed twice the design
application rate.
(2) The engineering report must include manufacturer's
recommended filtration and application rates with test data.
(3) Single Media. A single media multi-compartmented
filter must have a maximum design filtration rate of 3.0 gallons per
minute per square foot of media surface.
(4) Dual Media. A dual media multi-compartmented filter
must have a maximum design filtration rate of 4.0 gallons per minute
per square foot of media surface.
(b) Media Design. Media sizes and depths must correspond
to the values in Table G.5. in Figure: 30 TAC §217.192(b), unless
an engineer uses calculations to justify different media sizes, depths,
or both in the engineering report.
Attached Graphic
(c) Backwash System.
(1) A backwash system must provide a minimum backwash
rate of 20 gallons per minute per square foot of media.
(2) The backwash duration must last at least 20 seconds
for each compartment and must allow a fluidized media expansion of
at least 20% by volume, unless the engineering report includes the
manufacturer's recommended backwash rates with test data that supports
a shorter backwash duration or less expansion of the fluidized media.
(3) The surge control and pumping system requirements
must be the same as those detailed in §217.191(c)(2) and (3)
of this title (relating to Additional Requirements for Deep Bed, Intermittently
Backwashed, Granular Media Filters).
(d) Traveling Bridge. A traveling bridge mechanism
must:
(1) provide support and access to the backwash pumps
and equipment;
(2) be constructed of corrosion-resistant materials;
(3) have provisions for consistent tracking of the
bridge and safe support of the power cords; and
(4) initiate a backwash cycle automatically when a
preset head loss through the filter media occurs.
(e) Floating Material Control. A multi-compartmented
filter system must provide for automatic removal of any floating material
from the surface of the multi-compartmented filter and return the
floating material to the headworks of the wastewater treatment facility
for further processing.
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