(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.

Source Note: The provisions of this §217.296 adopted to be effective August 28, 2008, 33 TexReg 6843; amended to be effective December 4, 2015, 40 TexReg 8254