Texas Administrative Code
Title 30 - ENVIRONMENTAL QUALITY
Part 1 - TEXAS COMMISSION ON ENVIRONMENTAL QUALITY
Chapter 217 - DESIGN CRITERIA FOR DOMESTIC WASTEWATER SYSTEMS
Subchapter H - NATURAL TREATMENT FACILITIES
Section 217.205 - Facultative Lagoons
Universal Citation: 30 TX Admin Code § 217.205
Current through Reg. 49, No. 52; December 27, 2024
(a) Configuration, Inlets, and Outlets.
(1) The length-to-width
ratio of a facultative lagoon must be 3.0 to 1.0.
(2) The flow in a facultative lagoon must be
from an inlet along one end of the lagoon to an outlet at the opposite end of
the lagoon.
(3) The length of a
facultative lagoon must be oriented in the direction of the prevailing winds
with the inlet side located such that debris will be blown toward the
inlet.
(4) A facultative lagoon
must have inlet baffles to collect floatable material when no pre-screening is
provided.
(5) An outlet must be
adjustable to allow the water level of a facultative lagoon to vary under
normal operating conditions.
(b) Depth.
(1) The deeper portion of a facultative
lagoon near the inlets must have a minimum depth of 12 feet to provide sludge
storage and anaerobic treatment.
(2) The deeper portion of a facultative
lagoon must cover at least 25% of the area of the lagoon bottom.
(3) The remainder of a facultative lagoon
must have a minimum depth of 8.0 feet.
(c) Organic loading. The organic loading must not exceed 150 pounds of five-day biochemical oxygen demand (BOD5) per acre per day based on the surface area of the facultative lagoon.
(d) Odor Control.
(1) A facultative lagoon inlet must
be at least 24 inches below the water surface to minimize odor.
(2) An outlet must be at least 12 inches
below the water surface, but not further below the water surface than a
distance equal to one-half the depth of the lagoon at the outlet.
(3) The design of a facultative lagoon must
allow for recirculation of at least 50%, but not more than 100% of the design
flow.
(4) The design of a
facultative lagoon must prevent siphoning of lagoon contents through a
submerged inlet.
(e) Removal efficiency. The design of a facultative lagoon must not be based on more than 50% removal of the influent BOD5.
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