La. Admin. Code tit. 51 § XIII-721

Current through Register Vol. 50, No. 11, November 20, 2024

Section XIII-721 - Oxidation Ponds [formerly Section IV of Appendix A]

A. [Formerly paragraph A:4.1 of Appendix A] An oxidation pond is a shallow pond designed specifically to treat sewage by natural purification processes under the influence of air and sunlight. The stabilization process consists largely of the interactions of bacteria and algae. Bacteria digest and oxidize the constituents of sewage and render it harmless and odor free. Algae utilize carbon dioxide and other substances resulting from bacterial action and through photosynthesis produce the oxygen needed to sustain the bacteria in the treatment process. During the detention period, the objectionable characteristics of the sewage largely disappear.

B. [Formerly paragraph A:4.2 of Appendix A] The minimum surface area of an oxidation pond must be no less than 400 square feet with a 4 to 5 foot average liquid depth and vertical side walls. This minimum size pond is adequate for design flows of up to 400 gallons/day (gpd). For design flows in excess of 400 gpd, the pond area must be increased to provide sufficient volume (at the 4 foot depth) to hold 30 days worth of flow (a 30-day retention period). For wastes with high BOD loadings, special consideration for increasing pond size must be given.

C. [Formerly paragraph A:4.3 of Appendix A] Section 1501. B.5 (Figure 5) shows a typical layout for a septic tank-oxidation pond system. The actual layout of any pond system will be governed to a great extent by the topography of the particular location. However, an oxidation pond must be located so as to comply with the minimum distance requirements from water wells, lines, etc., as contained in Part XII of this Code. It is also desirable for aesthetic reasons to locate it as far as possible, but at least 50 feet from any dwelling and no less than 20 feet from the property line to water's edge at normal operating line.

D. [Formerly paragraph A:4.4 of Appendix A] As mentioned, the use of the minimum surface area of 400 square feet requires that an oxidation pond be furnished with vertical side walls so that an adequate volume for treatment is provided. Section 1501. B.6 (Figure 6) shows a type of construction utilizing treated timber which under normal soil conditions is acceptable for the vertical side walls of a 20 foot by 20 foot oxidation pond with a 5 foot average water depth. Section 1501. B.7 (Figure 7) shows a similar type of construction utilizing concrete blocks. Either of these designs requires very little maintenance.

E. [Formerly paragraph A:4.5 of Appendix A] Vertical side walls must be of cypress or treated timbers or concrete blocks and so constructed as to provide a permanent structure.

F. [Formerly paragraph A:4.6 of Appendix A] Although not encouraged, a pond may be constructed with sloping sides and earthen levees. Such a design is shown in §1501. B.8 (Figure 8). The design requires a minimum surface area of 625 square feet with a 5 foot liquid depth at the center in order to achieve the required volume. The cost of this design is less than that of the vertical wall ponds referred to above, but more space is needed and routine maintenance requirements such as levee mowing are greater. The slope of the natural earth side walls must not be shallower than one-to-one (45-degree angle) [see §1501. B.8 (Figure 8)].

G. [Formerly paragraph A:4.7 of Appendix A] A septic tank must precede the oxidation pond and must comply with the septic tank requirements presented in these regulations.

H. [Formerly paragraph A:4.8 of Appendix A] The pipe from the septic tank to the pond as well as the outfall pipe from the pond must be at least 4 inches in diameter and placed at a minimum slope of 2 inches per 100 feet. The inlet must extend 4 to 6 feet horizontally into the pond and be directed downward at least 1 1/2 to 2 feet below the liquid surface level. The outlet must extend 4 to 6 feet horizontally into the pond and consist of a tee with the invert set at the operating water level of the pond. One leg of tee must be open and extend above the water level, while the down leg is extended 1 1/2 to 2 feet below the water level. The invert of the pond outlet must be lower than the pond inlet invert [see §1501. B.8 (Figure 8)]. Additionally the invert of the pond inlet must be at least 2 inches lower than the invert of the septic tank outlet.

I. [Formerly paragraph A:4.9 of Appendix A] The pond shall be enclosed by a suitable non-climbable fence to keep out children, pets and livestock. An open type fence (woven wire) is preferable because it will not restrict sunlight and air which are necessary for the treatment. The fence shall be at least 5 feet in height and be provided with a locked gate.

J. [Formerly paragraph A:4.10 of Appendix A] Abandoned oxidation ponds (ponds no longer in active use) shall be dewatered, allowed to dry and then filled with soil to natural grade.

La. Admin. Code tit. 51, § XIII-721

Promulgated by the Department of Health and Hospitals, Office of Public Health, LR 28:1351 (June 2002).

AUTHORITY NOTE: Promulgated in accordance with R.S. 40:4(A)(6) and R.S. 40:5(9)(20).