| (a) A bioassay procedure must conform to one of the
following protocols:
(1) National Water Research Institute's Ultraviolet Disinfection Guidelines for Drinking
Water and Water Reuse (3rd edition, 2012); or
(2) NSF International, The Public Health and Safety
Company, 40 CFR §35.6450 Environmental
Technology Verification Protocol (October 2002).
(b) The following minimum standards are required for
validation of a bioassay.
(1) The source of water for the test organism solution
must be identified and its UV transmittance must be recorded. If potable
water is used, the bioassay must also address how disinfectant residues
were removed.
(2) The depth of the suspension must be 1.0 centimeter.
(3) The organism density must be 105 to 107 plaque
forming units or colony forming units per milliliter.
(4) The dose response relationship must be based on
a range of five to seven exposure times.
(5) The bioassay procedure must be conducted at least
three times, each from a separate dilution of the same stock suspension.
All results must be included for a bioassay to be valid.
(6) A minimum of two controls (unexposed) must be sampled
and analyzed with each dose run. All results must be included for
a bioassay to be valid.
(7) The diameter of the collimating tube must be at
least equal to the diameter of the Petri dishes. Any difference between
the diameter of the collimating tube and the diameter of the Petri
dishes must be accounted for in the supporting calculations.
(8) The narrow band detector used for intensity determination
must be calibrated for accuracy.
(9) 254 nanometer ultraviolet must be measured and
reported as the dose response.
(10) The speed of the mixing bar must not cause spatter
or cavitation.
(11) Any difference between the velocity profile in
the bioassay and the velocity profile in the full-scale unit must
be justified.
(12) Any difference between the gallons per minute
per inch of UV lamp in the bioassay and the gallons per minute per
inch of UV lamp in the full-scale unit must be justified.
(13) The lamp intensity data obtained in the bioassay
must be used to set the operating parameters of the lamps.
(14) Lamp intensity used in the flow through test reactor
shall be set after a 100-hour burn in and stabilization period.
(15) Electrical input for 100% lamp output must be
recorded and verified.
(16) Lamp intensity in the bioassay must be measured
at the exact height of the surface of the suspension.
(17) No operating condition may be used that has not
been proven effective by the bioassay.
(18) Any variation from the criteria in this subsection
must:
(A) be justified by using industry best practices such
as Standardization of Method for Fluence
(UV Dose) Determination in Bench-Scale UV Experiments, Bolton
and Linden (2003); and
(B) approved through the variance procedures in §217.4
of this title (relating to Variances).
(19) Bioassay procedures and results must be signed
and sealed by a licensed professional engineer.
(c) Effluent percent transmission during the full scale
testing shall be established in accordance with the terms and conditions
of the wastewater treatment facility's wastewater permit.
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