1. (a) The requirements of this section apply to both completely mixed lagoons and partially mixed lagoons, unless otherwise specified.
2. (b) An aerated lagoon system must maintain a minimum of 1.6 pounds of oxygen per pound of influent five-day biochemical oxygen demand (BOD₅) with the largest single aeration unit in a lagoon system out of service.
3. (c) A lagoon system's pipes and valves must allow the flow to be proportionally rerouted.
4. (d) The aeration equipment must have an alarm that will provide sufficient notification to ensure timely repair to prevent a permit violation. If a facility is not staffed 24 hours per day, the alarm system must be connected to a telemetry system with battery backup.

5. (e) The BOD₅ removal in each lagoon must be calculated using the following equation:
   Attached Graphic
   

   1. (1) The value of K for a domestic wastewater in a completely mixed lagoon is 0.50 day^-1 at 20 degrees Celsius. The value of K for a partially mixed lagoon is 0.28 day^-1 at 20 degrees Celsius.
   2. (2) The value of K may be adjusted for the minimum monthly water temperature using the following equation:
      Attached Graphic
      
   3. (3) The value of K may be determined for high-strength or industrial wastewater by either a laboratory study or evaluation of an existing facility treating similar wastewater.

6. (f) Aeration Equipment.

   1. (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. (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. (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.
7. (g) Aerated Lagoon Design Requirements. An aerated lagoon system must be designed in accordance with requirements for a wastewater treatment lagoon in §217.203(e) of this title (relating to Design Criteria for Natural Treatment Facilities) and §217.207(d) of this title (relating to Stabilization Lagoons).
8. (h) 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.