| (ii) The executive director may approve an alternate
method of fly control for a trickling filter that exceeds 6.0 feet
in height if the effectiveness of the alternate method is verified
at a full-scale installation and documented in the engineering report.
(B) Snails. A trickling filter system must be designed
to prevent sludge accumulation that attracts snails. A trickling filter
system must include a low-velocity, open channel between a trickling
filter and final clarifier for manual removal of snails.
(3) Corrosion Protection. A trickling filter must be
designed to prevent corrosion. Corrosion-resistant materials must
be used for all equipment and for construction of a trickling filter,
including ventilation equipment and covers.
(p) Flow Measurements. A trickling filter system must
include a means to measure the flow to each trickling filter and the
recirculation flow of each trickling filter.
(q) Odor Control. A trickling filter system must use
ventilation and periodic flushing at a higher dosing intensity to
minimize potential odor.
(1) Covers.
(A) The executive director may require an owner of
a wastewater treatment facility with prior odor complaints to install
a cover over a new or altered trickling filter.
(B) A cover must allow access to the entire top of
the trickling filter media and to the distributor for maintenance
and removal.
(C) A covered trickling filter must have a forced ventilation
system with a scrubber or an adsorption column for odor control.
(2) Stripping. A trickling filter with an influent
organic strength of BOD5 greater than
200 milligrams per liter must have forced ventilation in a down-flow
mode to minimize odor. Odorous off-gases may be:
(A) recycled through a trickling filter;
(B) used to ventilate a tertiary nitrifying trickling
filter in an up-flow mode;
(C) diffused into an aeration basin; or
(D) treated separately for odor control using a scrubber
or an adsorption column.
(r) Final Clarifiers. The size of the final clarifiers
for a wastewater treatment facility with a trickling filter must ensure
the required effluent total suspended solids removal at the peak flow
with all recirculation pumps in operation.
(s) Report Requirements.
(1) The engineering report must specify the trickling
filter efficiency formula used in the design calculations.
(2) The engineering report must include the operating
data from any existing trickling filter of similar construction and
operation to justify the projected treatment efficiency, kinetic coefficients,
and other design parameters as required in this subchapter.
(3) The engineering report may include more than one
set of applicable design equations to allow crosschecking of predicted
treatment efficiency.
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