Statutes, codes, and regulations
Wyoming Administrative Code
Agency 020 - Environmental Quality, Dept. ofSubagency 0011 - Water QualityChapter 11 - DESIGN AND CONSTRUCTION STANDARDS FOR SEWERAGE SYSTEMS, TREATMENT WORKS, DISPOSAL SYSTEMS OR OTHER FACILITIES CAPABLE OF CAUSING OR CONTRIBUTING TO POLLUTION AND MOBILE HOME PARK AND CAMPGROUND SEWERAGE AND PUBLIC WATER SUPPLY DISTRIBUTION SYSTEMS
Part B - MUNICIPAL AND DOMESTIC SEWERAGE SYSTEMS, TREATMENT WORKS, AND DISPOSAL SYSTEM
Section 11-15 - Attached Growth Systems

020-11 Wyo. Code R. § 11-15

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Current through April 27, 2019
Section 11-15 - Attached Growth Systems

(a) Pretreatment and primary treatment requirements. Attached growth systems shall be preceded by primary settling or fine screening. If fine screening is provided, the screen size shall have 0.06 inch (1.5 mm) or smaller openings.

(b) Trickling filters.

  • (i) Loading rates. Applied organic loading rates on trickling filters, where not used in series with activated sludge, shall be limited to:

    Applied Liquid Rate to Surface of Filter BOD Loading*
    (gpm/sf) (1pm/m) (lb/1000ft3/d) (kg/1000 m3/d)
    Rock Media 0.1 4.07 10 160
    0.2 8.15 12 192
    0.3 12.22 16 256
    Plastic or
    Redwood Media 20 320

    *For more than a one-stage trickling filter, the volume of all stages shall be used.

  • (ii) Recirculation. Recirculated flow to stationary media attached growth systems shall be provided. Recirculated flow shall be sufficient to provide the following minimum wetting rates:

    Media Minimum Wetting Rate
    (gpm/sf) (1pm/m2)
    Rock 0.1 4.07
    Plastic or redwood 0.75 30.5

  • (iii) Media. Media may be rock or specially manufactured material made of redwood or plastic. Rocks shall be durable and free from thin, elongated, flat pieces and should have the following size distribution:

    Passing 6-inch (15.2 cm) screen 100% by weight
    Retained on 4-inch (10.2 cm) screen 95 - 100% by weight

    Fabricated media shall be resistant to ultraviolet degradation, disintegration, erosion, aging, all common acids, alkalies, organic compounds, fungus and biological attack. Media shall be capable of supporting a man's weight.
  • (iv) Flow distribution. Wastewater shall be applied to stationary media by a rotary distributor or a fixed nozzle distribution system that provides uniform distribution. Flow distribution between multiple units of stationary or rotating media systems shall be by weirs, meters and valves, or other positive flow split device.
  • (v) Depth of media. Rock trickling filter depths shall be between five (5) to ten (10) feet (1.52 to 3.04 m), and manufactured media filter depth shall be between ten (10) to thirty (30) feet (3.05 to 9.15 m).
  • (vi) Underdrain system. The underdrainage system shall cover the entire floor of the filter. Inlet openings into the underdrains shall have an unsubmerged gross combined area equal to at least 15 percent of the surface area of the filter. Underdrains shall have a minimum slope of one percent.

    Effluent channels shall be designed to maintain minimum velocity of two (2) feet per second (0.61 mps). Drains, channels and pipe shall be designed to have maximum depth flow of 50 percent.
  • (vii) Flushing. Provide valves and structurally capable walls to permit flooding rock media filters. Access shall be provided around the periphery of the underdrain system to allow flushing the underdrains.
  • (viii) Freeboard. The clearance between rotating distributor and the media shall be at least eighteen (18) inches (0.46 m). The surrounding wall shall extend 2.5 feet (0.76 m) above the distributor.
  • (ix) Ventilation. All trickling filters shall be provided with ventilation openings to the underdrain. Ventilation openings will be provided with dampers or other adjustable devices to permit adjusting the ventilation rate opening. Ventilation openings shall be a minimum of eight (8) square feet (0.74 m²) per 1,000 lb (454 kg) BOD5/day.

    Forced ventilation providing 4,000 cfm (113 m3/min) per 1,000 lb (454 kg) BOD5/day shall be provided for covered filters.

(c) Rotating biological contactors (RBC).

  • (i) Loading rates. The organic loading rate on the first stage of an RBC shall be limited to 140 lb BOD/1,000 cu ft (2240 kg/1,000 m3) of media per day. The organic loading rate on all stages of an RBC shall be limited to 45 lb/1,000 cu ft (720 kg/1,000 m3) of media for media having a specific surface area of 35 sq ft per cu ft (114.8 sq m/m3). When more than ½ of the media has a specific surface area of 50 sq ft per cu ft (164 sq m/m3), the organic loading may be increased to 50 lb/ 1,000 cu ft (800 kg/1,000 m3).
  • (ii) Number of stages. Rotating biological contactors shall be designed with a minimum of three (3) stages in series. Baffles shall be provided between stages.
  • (iii) Velocities. The rotational speed of the contactors shall be designed to maintain at least two mg/L of dissolved oxygen in each stage at designed loading rates. Drive units shall provide a rotational speed of one rpm or more.
  • (iv) Draining. Provide drains from each contactor basin.
  • (v) Media materials. Media materials shall be special manufactured material suitable and durable for the rotating biological contactor process. Media shall be resistant to disintegration, ultraviolet degradation, erosion, aging, all common acids, alkalies, organic compounds, fungus, and biological attack. Media shafts shall be designed for unbalanced loads and cycle fatigue.
  • (vi) Housing. The housing for the RBC'S shall be designed with openings or access to allow removal and replacement of entire shafts.

020-11 Wyo. Code R. § 11-15

Amended, Eff. 6/29/2018.