(a) The requirements of this section apply to both completely mixed aerated lagoons and partially mixed aerated lagoons, unless otherwise specified.
(b) A minimum of 1.6 pounds of oxygen per pound of influent five-day biochemical oxygen demand (BOD5 ) must be maintained in an aerated lagoon system, even with the largest single aeration unit in a lagoon system out of service.
(c) The aeration equipment must have an audio-visual alarm system. If a wastewater treatment facility is not staffed 24 hours per day, the alarm system must be connected to a telemetry system, such as an auto dialer or Supervisory Control and Data Acquisition system, with battery backup.
(d) The BOD5 removal in each aerated lagoon must be calculated using the following equation:
Attached Graphic
  (1) The value of K for domestic wastewater in a completely mixed lagoon is 0.50 day-1 at 20 degrees Celsius. The value of K for domestic wastewater in a partially mixed lagoon is 0.28 day-1 at 20 degrees Celsius.
  (2) The value of K must be adjusted for the minimum monthly water temperature using the following equation:
Attached Graphic
  (3) The value of K must be determined for high-strength or industrial wastewater by either a laboratory study or an evaluation of an existing wastewater treatment facility treating wastewater with similar organic strength and industrial contributions.
(e) Aeration Equipment.
  (1) The size of the aeration equipment in an aerated lagoon must be able to supply the oxygen demand determined in subsection (b) of this section.
  (2) For the purpose of sizing aeration equipment, an aerated lagoon must comply with the mechanical and diffused air requirements in §217.155(c) of this title (relating to Aeration Equipment Sizing).
  (3) If multiple partially mixed aerated lagoons are used in series, the power input may be reduced as the influent BOD5 to each lagoon decreases.
(f) Aerated Lagoon Design Requirements. An aerated lagoon system must be designed according to the requirements for a wastewater treatment lagoon in §217.203(f) of this title (relating to Design Criteria for Natural Treatment Facilities) and §217.207(d) of this title (relating to Stabilization Lagoons).
(g) Scour Prevention. An earthen-lined aerated lagoon system must include a concrete scour pad in each area of the earthen liner that is subject to a velocity equal to or greater than 1.0 foot per second.

Source Note: The provisions of this §217.206 adopted to be effective August 28, 2008, 33 TexReg 6843; amended to be effective December 4, 2015, 40 TexReg 8254