Section 217.207 - Stabilization Lagoons(a) Primary treatment must remove the settleable and floatable solids in the influent prior to the wastewater entering a stabilization lagoon.(b) Odor Management. (1) A stabilization lagoon must be located so that odors from the stabilization lagoon will not cause a nuisance.(2) If uncontaminated water is available, a stabilization lagoon must be pre-filled with uncontaminated water to the 2.0 foot level at start-up.(3) A stabilization lagoon system must include a piping arrangement that allows the recirculation of effluent from a final lagoon to the influent side of an initial stabilization lagoon.(4) A stabilization lagoon may return recirculation water by surface spray to assist in maintaining aerobic conditions at the lagoon surface and to reduce potential odor.(c) Minimum Number of Wastewater Stabilization Lagoons. At least two stabilization lagoons are required to comply with secondary treatment limits. The stabilization lagoons must be operated in series, following the primary treatment unit.(d) Stabilization Lagoon Design. (1) The minimum length-to-width ratio of a stabilization lagoon is 3.0 to 1.0.(2) Inlet and outlet structures must be adjustable to assist in controlling vegetative growth. Inlet and outlet structures must allow the water level to be raised and lowered by at least 6.0 inches.(e) Pipe and Hydraulic Equipment. (1) All structures and pipes in a stabilization lagoon must be sized to transport at least 250% of the wastewater treatment facility's design flow.(2) The inlet and outlet structures must be sized to convey the volume contained within the top 6.0 inches of a lagoon within a 24-hour period, based on the normal water level at design flow and the corresponding pressure head.(3) The pipe and recirculation system must allow a stabilization lagoon system to comply with the wastewater treatment facility's permitted effluent limitations, even with any one lagoon out of service.(f) Maximum Surface Organic Loading Rate for Stabilization Lagoons.(1) The maximum surface organic loading rate on a stabilization lagoon series is 35 pounds (lbs) of five-day biochemical oxygen demand (BOD5) per acre per day.(2) The maximum surface organic loading rate on the first lagoon in a stabilization lagoon series is 75 lbs of BOD5 per acre per day.(3) The surface organic loading rate applied to a stabilization lagoon series is equal to the total influent organic loading minus any reduction in organic load provided by the primary treatment units.(g) Inlet and Outlet Structures. (1) A stabilization lagoon outlet must include removable baffles to prevent floating material from being discharged, and must be constructed to operate correctly as the level of the lagoon surface varies under normal operating conditions.(2) An outlet must be at least 18 inches but not more than 24 inches below the water surface in a stabilization lagoon to control the discharge of duckweed and floating algae.(3) A multipurpose control structure may be used to facilitate normal operational functions such as drawdown, flow distribution, adjusting water depth, flow measurement, sampling, access for pump for recirculation, chemical addition, and exclusion of floating materials. A multipurpose control structure may also be used to minimize the number of special purpose structures in a stabilization lagoon.(4) A pipe embankment penetration must have a seep water-stop collar.(5) A stabilization lagoon must have a drainpipe that allows the stabilization lagoon to be emptied for maintenance and may use a pump as part of a drainage system. If a permanent drain pipe will not be installed, a temporary pipe suction station must be provided.30 Tex. Admin. Code § 217.207
The provisions of this §217.207 adopted to be effective August 28, 2008, 33 TexReg 6843; Amended by Texas Register, Volume 40, Number 47, November 20, 2015, TexReg 8329, eff. 12/4/2015