Oklahoma Administrative Code
Title 252 - Department of Environmental Quality
Chapter 656 - Water Pollution Control Facility Construction Standards
Subchapter 16 - Biological Treatment Standards
Section 252:656-16-2 - Attached growth systems
Universal Citation: OK Admin Code 252:656-16-2
Current through Vol. 41, No. 13, March 15, 2024
(a) Rotating biological contactors (RBC). An RBC can only be installed to replace or to add to an existing RBC.
(1)
Winter protection. Enclose RBC units in a corrosion resistant
structure to protect biological growth from cold temperatures and excessive
heat loss.
(2)
Pretreatment. Provide primary clarifiers with scum and grease
collecting devices. Bar screening and/or comminution alone are not suitable
pretreatment.
(3)
Staging. Provide at least four stages for secondary treatment
applications, with more stages for greater nitrification and BOD
removal.
(4)
Loading.
(A)
Hydraulic. Equalize flow
where the ratio of peak flow to average flow is 2.5 or greater. For secondary
treatment hydraulic loading shall be from 2 to 4
gpd/ft2 and shall not exceed 0.75 to 2.0
gpd/ft2 where nitrification is required.
(B)
Organic. First stage loading
rates shall be from 2.5 to 4.0 lbs. of soluble BOD/day/1,000
ft2. 3.0 lbs. is recommended.
(5)
Tanks. Provide at least 0.12
gal/ft2 of media for RBC tanks to maintain a
hydraulic load of 2 gpd/ft2. Provide a side water
depth of 5 feet or submerge the media at least 40%.
(b) Trickling filters. Trickling filters may be installed to pretreat high-strength waste only, or to add to or replace existing trickling filters. Provide primary clarifiers with scum and grease collecting devices before filters so the influent will be relatively free from settleable, floating, or suspended matter. Design secondary clarifiers to meet the criteria of Appendix B of this Chapter.
(1)
Design basis. Filters are
termed standard or high rate on the basis of hydraulic and biological loading.
High rate filters may be used to pretreat wastewater before further biological
treatment. High rate systems can withstand highly variable hydraulic overload
conditions without significant deterioration of the biological growth. For
design criteria, see Appendix A, Design Tables.
(2)
Hydraulics. Sewage
application shall be continuous. Provide all pump stations with a backup.
(A)
Head requirements. For
reaction type distributors, a minimum head of 24 inches above the center of the
arms is required. Design distributors to uniformly distribute wastewater over
at least 90% of the surface area.
(B)
Clearance. Provide at least
6 inches of clearance between the media and distributor arms.
(C)
Piping system. Design the
piping system, including dosing equipment and distributor, for the peak hourly
flow rate, including recirculation.
(3)
Media.
(A)
Quality. Plastic media or
its approved equivalent shall be used. Manufactured media must also be
resistant to ultraviolet degradation, disintegration, erosion, aging, common
acids and alkalies, organic compounds, and fungus and biological
attack.
(B)
Depth.
Media depth for standard rate filters must be 6 to 8 feet deep and, for high
rate filters, from 10 to 30 feet. Depths that deviate from the above criteria
must be justified by a pilot study.
(4)
Underdrain system. The
underdrain system shall cover the entire floor of the filter. Inlet openings
into the underdrains shall have an unsubmerged gross combined area at least 15
percent of the surface area of the filter.
(A)
Hydraulic capacity and
ventilation. Underdrains shall slope at least 1%. Design effluent
channels to produce a minimum velocity of 2 fps of the average daily
application rate. Design the underdrain system, effluent channels and effluent
pipe to allow free air passage. Not more than 50% of the cross sectional area
for all drains, channels and pipe may be submerged under the design hydraulic
loading.
(B)
Flushing.
Design the underdrains to be flushed.
(5)
Freeboard. Provide two feet
of freeboard to prevent splashing and to protect the distributor. Structures
taller than 25 feet shall have 4 feet of freeboard to contain windblown
spray.
(6)
Recirculation. Recirculate effluent to maintain an active
biological growth and to increase overall efficiency.
(7)
Dosing rate. The dosing rate
on a trickling filter is the depth of liquid discharged on top of the packing
for each pass of the distributor. For a standard rate filter, the dosing rate
shall be in the range of 0.4 inches per pass to 1.2 inches per pass. For high
rate filters, the rate shall be in the re range of 0.6 inches per pass to 7.0
inches per pass.
(c) Whole effluent toxicity failures. Attached growth systems may not consistently provide ammonia removal through the nitrification process so the effluent from these facilities may be toxic to aquatic life and thus cause whole effluent toxicity test failures.
Added at 23 Ok Reg 937, eff 6-15-06; Added at 28 Ok Reg 1282, eff 7-1-11
Disclaimer: These regulations may not be the most recent version. Oklahoma may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
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