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 217.213 - Integrated Facultative Lagoons

Current through Reg. 49, No. 28; July 12, 2024
(a)
				  Non-conforming technology. An integrated facultative lagoon is a non-conforming
				  technology and is subject to the requirements of §
										217.7(b)(2)
				  of this title (relating to Types of Plans and Specifications
				  Approvals).
(b) Integrated
				  Facultative Lagoon Design.
(1) The
				  length-to-width ratio of an integrated facultative lagoon must be 3.0 to
				  1.0.
(2) A pit must not be less
				  than 0.25 acre in total surface area.
(3) The outer lagoon area must not be less
				  than 10 times the surface area of the pit.
(4) A pit must have adequate volume to
				  contain:
(A) 0.1 cubic foot per capita per
				  year of sludge storage for a minimum of 20 years; and
(B) two days of design flow above the sludge
				  storage area.
(5) The
				  up-flow velocity in the pit must be less than 2.0 feet per day at design
				  flow.
(6) If an integrated
				  facultative lagoon has more than one pit, influent flow must be split
				  proportional to the pit volumes.
(7) An inlet must be located in the pit
				  portion of a lagoon.
(8) An outlet
				  must be at a depth of 1.0 foot from the lagoon surface.
(9) An integrated facultative lagoon must
				  meet the buffer zone requirements specified in §
											309.13
				  of this title (relating to Unsuitable Site Characteristics).
(10) Depth.
(A) A pit must be at least 15 feet deep
				  during normal operating conditions, measured from the water surface to the
				  influent inlet point.
(B) An
				  integrated facultative lagoon must have berms around the pit.
(C) The berm height must be at least 5.0 feet
				  or one-half the depth of the outer lagoon, whichever is greater.
(D) The distance from the water surface
				  elevation during normal operating conditions to the top of the berm around a
				  pit must be at least 5.0 feet.
(11) Organic Loading. The organic loading
				  into a pit must not exceed 300 pounds of five-day biochemical oxygen demand per
				  acre of total lagoon area per day.
(12) Odor Control.
(A) An inlet to a pit must be 3.0 feet above
				  the bottom of the lagoon and the influent flow must be directed
				  downward.
(B) An integrated
				  facultative lagoon must be capable of recirculating at least 50% of the design
				  flow from an outlet of the downstream lagoon.
(C) Oxygenated water from a downstream
				  stabilization lagoon must be recirculated to the surface of the integrated
				  facultative lagoon.
(D) An
				  integrated facultative lagoon must prevent siphoning of lagoon contents through
				  a submerged inlet.
(13)
				  Removal Efficiency.
(A) The design of an
				  integrated facultative lagoon must not be based on more than 60% organic
				  removal efficiency in the pit.
(B)
				  The design of an integrated facultative lagoon must not be based on a
				  subsequent organic removal efficiency of more than 50% in the outer portion of
				  the integrated facultative lagoon.
(C) The design organic removal efficiency for
				  the entire integrated facultative lagoon must not exceed 80%.
(14) Detention Time. An integrated
				  facultative lagoon must provide a minimum of 21 days hydraulic retention time
				  at design flow.