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Oklahoma Administrative Code (Last Updated: March 11, 2021) |
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TITLE 252. Department of Environmental Quality |
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Chapter 641. Individual and Small Public On-Site Sewage Treatment Systems |
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Subchapter 10. Aerobic Treatment Systems |
SECTION 252:641-10-2. Design and installation
Latest version.
- (a) Fluctuating flows. If the daily flow fluctuates so that the flow on any given day during the week exceeds the aerobic treatment unit's daily capacity, then an aerobic treatment system may not be used unless a flow equalization tank, which meets the requirements of 252:641-9, is installed between the trash tank and the aerobic treatment unit.(b) Components of aerobic treatment systems. Aerobic treatment systems shall be comprised of the following components:(1) Trash tank. There shall be a trash tank that meets the requirements of NSF/ANSI Standard 40 or 252:641-7-2. The trash tank shall:(A) be constructed to prevent sewage from leaking out of the tank and to prevent the infiltration of water into the tank;(B) have a minimum liquid capacity of three hundred (300) gallons or the average daily flow, whichever is greater, except that the minimum liquid capacity shall not be less than what was used in the NSF/ANSI certification process;(C) have a removable lid or a manhole opening of sufficient size to allow for maintenance. The lid or manhole shall be sealed to prevent leakage and extend a minimum of two inches (2") above ground elevation. The cover for the opening shall have a lock, locking bolt or some type of tamper-resistant fastener, or require a tool for removal;(D) have baffles installed at its inlet and the outlet. The baffles shall extend to within two inches (2") of the top of the trash tank; and(i) Inlet. Inlet baffles shall extend at least six inches (6") below the liquid depth of the trash tank.(ii) Outlet. Outlet baffles shall extend below the liquid level by twenty percent (20%) to forty percent (40%) of the liquid depth.(E) meet the requirements of 252:641-7-1(c).(2) Aerobic treatment unit. There shall be an aerobic treatment unit that:(A) has been tested and certified by an ANSI accredited third party certifier as meeting the most current NSF/ANSI Standard 40 and when required by waterbody restrictions NSF/ANSI Standard 245;(B) is constructed to prevent sewage from leaking out of the tank and to prevent the infiltration of water into the tank(C) is rated at or above the design daily flow and designed treatment capacity for BOD;(D) produces effluent clear enough that the bottom of the pump tank is visible when it is full; and(E) has an opening of sufficient size to allow for maintenance that extends a minimum of two inches (2") above ground elevation. The cover for the opening shall have a lock, locking bolt or some type of fastener, or require a tool for removal.(3) Method of disinfection. If spray irrigation is used as the type of dispersal, then there shall be a method to disinfect the effluent that has been tested and certified by an ANSI accredited third party certifier as meeting the most current NSF/ANSI Standard 46, between the aerobic treatment unit and the pump tank (or in the pump tank). If chlorination is used as the disinfection method, a free chlorine residual of two tenths of a milligram per liter (0.2 mg/l) must be maintained in the pump tank. All other methods of disinfection shall effectively reduce the fecal coliform count to less than two hundred colonies per one hundred milliliters (200/100 ml).(4) Pump tank. There shall be a pump tank, which shall:(A) meet the requirements of NSF/ANSI Standard 40 or 252:641-7-2;(B) have a minimum liquid capacity of seven hundred (700) gallons or, for systems with an average flow over three hundred fifty (350) gallons per day, have a liquid capacity of at least twice the average daily flow;(C) have a sampling port in the pump tank at the discharge outlet or in the treated effluent line following the pump tank;(D) have a float in the pump tank set so that the pump tank is never more than one-half (1/2) full;(E) have a high-water alarm set to activate and alert the owner/operator if the pump tank becomes more than one-half (1/2) full; and(F) have an opening of sufficient size to allow for maintenance that extends a minimum of two inches (2") above ground elevation. The cover for the opening shall have a lock, locking bolt or some type of fastener, or require a tool for removal.(5) Dispersal field. Effluent treated by an aerobic treatment unit shall be dispersed as described in Subchapter 12 of this Chapter.(c) Level. Once installed, each tank (i.e., trash tank, aerobic treatment unit and pump tank) shall have no more than one inch (1") variation in elevation from side to side and end to end.(d) Depth of aerobic treatment system components. The top of all components of the aerobic treatment system, excluding the trash tank and dispersal field, shall be covered with no more than thirty-six inches (36") of soil and have access to all serviceable parts within twenty-four inches (24") of ground level.(e) Solid pipe. The solid pipe used to connect the components of an aerobic treatment system must meet the minimum specifications listed in Appendix C.(f) Fall. Unless a lift pump is utilized, there shall be fall between:(1) the trash tank and the aerobic treatment unit; and(2) the aerobic treatment unit and the pump tank.(g) Manufacturer's specification. All aerobic treatment systems shall be installed in accordance with the manufacturer's specifications and maintained as required by the most current version of NSF Standard 40 and Standard 245.