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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 656. Water Pollution Control Facility Construction Standards |
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Subchapter 23. Supplemental Treatment Standards |
SECTION 252:656-23-1. Effluent filtration
Latest version.
- (1) required to have filtration to maintain OPDES permit compliance shall be sized using the design peak hourly flow; and(2) that produces Category 2 reclaimed water shall be sized using the anticipated design flow.(b) Conditions requiring pretreatment. Filtration systems shall be preceded with a pretreatment process, such as chemical coagulation and sedimentation or other acceptable process,when:(1) permit requirements for suspended solids are less than 10 mg/l,(2) effluent quality can be expected to fluctuate significantly,(3) significant amounts of algae will be present,(4) a lagoon is used for polishing effluent, which requires pilot testing for which the protocol has been pre-approved by DEQ, or(5) the systems supplies Category 2 reclaimed water for reuse.(c) Reliability. Filtration systems shall be designed and constructed with:(1) convenient access to all components and the media surface for inspection and maintenance without taking other units out of service; and(2) enclosed controls and equipment with heating and ventilation equipment to control humidity.(d) Redundancy. Filtration systems shall have at least 2 units with the capacity to handle the maximum wastewater flow in the OPDES permit and/or the anticipated design flow for reclaimed water systems with the largest unit out of service.(e) Backwash. Filtration systems shall have the capacity to backwash all filters.(1) The backwash filter unit pumps shall be designed to backwash any filter with the largest pump out of service.(2) Filtration systems shall be backwashed with filtered water.(3) Backwash wastewater shall be returned to the headworks.(4) The return rate of backwash water from filtration systems to treatment units shall not exceed 15% of the wastewater design daily average flow rate to the treatment units.(5) The hydraulic and organic load from the backwash water shall be taken into account in the overall design of the treatment plant.(6) Surge tanks, if necessary, shall hold at least 2 backwash volumes.(7) Where backwash water is pump-returned for treatment, the required pumping capacity shall be maintained with the largest unit out of service.(f) Back-up power. Filtration systems shall have a back-up power source that meets the requirements of 252:656-9-1.(g) Drain line. Each filter unit shall be equipped with a drain line at least 6 inches in diameter capable of draining the basin to the headworks.(h) Flocculation. Flocculation shall be used prior to filtration when supplying Category 2 reclaimed water for reuse. Flocculation shall:(1) include chemical feed equipment to meet the reclaimed water system's anticipated design flow and the ability to proportion chemical feed rates;(2) ensure the rapid dispersion and mixing of chemicals throughout the wastewater by providing mechanical or in-line static mixers; and(3) include a minimum of 2 flocculation basins. Each basin shall be equipped with a:(A) method to control the speed of the paddles; and(B) drain line at least 6 inches in diameter capable of draining it to the head of the plant.(i) Granular media filtration. The following are the requirements when using granular media filtration:(1) Gravity filter use. Use gravity filters where greases or similar solids are expected to be present in the wastewater.(2) Filtration rates. Filtration rates shall not exceed 5 gpm/ft at the peak hourly flow for OPDES permits or the anticipated design flow for water reuse systems with the largest unit out of service.(3) Backwash rate. The backwash rate shall be adequate to fluidize and expand each media layer a minimum of 20%. The backwash system shall provide a variable backwash rate of at least 20 gpm/ft for 10 minutes.(4) Filter media.(A) Selection. Media size will depend on the filtration rate, treatment prior to filtration, filter configuration, and effluent quality requirements.(B) Specifications. Minimum media depths and media sizes [shown in brackets], with a uniformity coefficient of 1.7 or less, are:(i) Anthracite(I) Single-medium - none(II) Dual-media - 20 inches [1.0-2.0 mm](III) Multi-media - 20 inches [1.0-2.0 mm](ii) Sand(I) Single-medium - 48 inches [1.0-4.0 mm](II) Dual-media - 12 inches [0.5-1.0 mm](III) Multi-media - 10 inches [0.6-0.8 mm](iii) Garnet or similar(I) Single-medium - none(II) Dual-media - none(III) Multi-media - 2 inches [0.3-0.6 mm](5) Filter appurtenances. Filters shall be equipped with:(A) washwater troughs,(B) surface wash or air scouring equipment,(C) flow control for effluent rate,(D) measurement and positive control of backwash rate,(E) capability to measure filter head loss,(F) positive means to shut off flow to filter during backwash,(G) filter influent and effluent sampling points,(H) a manual override for automatic controls and each individual valve essential to the filter operation,(I) an underdrain system to uniformly distribute backwash water (and air, if provided) without clogging from solids in the backwash water,(J) a method for periodic chlorination of the filter influent or backwash water to control slime growths, and(K) pressure filters with convenient access to the media for treatment or cleaning.(j) Traveling bridge filters. All of the requirements in (a) through (i) of this Section apply to traveling bridge filters with the following exceptions:(1) Filtration rates. With one cell out of service, the peak application rate to any unit shall not exceed twice the applicable design filtration rate below:(A) A single media filter shall have a maximum design filtration rate of 3.0 gpm/ft of media surface at the peak hourly flow.(B) A dual media filter shall have a maximum design filtration rate of 4.0 gpm/ft of media surfaceat the peak hourly flow.(2) Backwash system. The backwash system shall:(A) provide a minimum of 20 gpm/ftof media being backwashed at a given time;(B) have a minimum duration of at least 20 seconds for each compartment;(C) expand the media a minimum of 20%;(D) provide a backwash rate, pressure and backwash water storage based on the manufacturer's recommendations; and(E) have the ability for manual override.(3) Traveling bridge mechanism. The traveling bridge mechanism shall:(A) provide support and access to the backwash pumps and equipment;(B) be constructed of corrosion resistant materials;(C) have provisions for consistent tracking of the bridge;(D) provide support of the power cords; and(E) initiate a backwash cycle automatically when a preset head loss through the filter media occurs.(4) Floating material control. A traveling filter system shall provide for automatic and regular removal of any floating material from the surface of a filter and return the floating material to the headworks.(k) Disc filters. All of the requirements in (a) through (h) of this Section apply to disc filters with the following exceptions:(1) Provide a minimum of 2 disc filter units capable of independent operation.(2) The size of the opening in the screen material shall be a nominal 10 Fm.(3) Base the design on:(A) an average hydraulic loading rate of 3.25 gpm/ft; and(B) a peak day hydraulic loading rate of 6.0 gpm/ft.(4) Equip the filter drum motor with a variable speed drive capable of adjusting the motor speed based on the plant flow.(5) The backwash rate, pressure and backwash water storage on the disc filter shall be based on the manufacturer's recommendations.(6) The disc filter and backwash operation shall be managed according to manufacturer's recommendation with the ability for manual override.(7) Each unit shall be equipped with a level sensor to initiate the backwash cycle. The design of each unit shall also include a high water level sensor with a telemetry system capable of alerting the responsible person(s) in charge in case of equipment failure.