Manhole Odor Control Units
1.A.1 – Description of the Equipment and How it Functions
The following paragraphs provide a brief description of the nine (9) Manhole Odor Control Units
installed in the Vent Structures throughout Sites 1995, Site 4, Site 17 and Site 27:
The Manhole Odor Control Units are installed inside of the manhole vent structures and are
designed to remove malodorous compounds from the foul manhole air as it is diffused from the
vent structures. As malodorous air from the manhole enters the bottom of the carbon canister
support in each manhole, it is diffused up through the activated carbon media by the ambient
pressure in the sewer vault. As the foul air is diffused through the activated carbon media, the
odorous compounds are absorbed by the activated carbon media. The carbon canisters can be
easily removed and the carbon media can be replaced as required. The pressure drop through the
carbon canister is less than 1.0 inch water column at a velocity of 35 feet per minute.
Each Manhole Odor Control Unit is comprised of four major components: the Carbon Canister,
the Carbon Media, the Canister Support Plate, and two Backdraft Dampers.
The Carbon Canister, manufactured by Bay Products, Inc., is white in color and composed of 90-
mil thick High-Density Polyethylene (HDPE). This canister has a porous bottom with a
polypropylene carbon retention screen and a closed flat top with treated air release holes. The
Carbon Canister has a 12 inch diameter top, a 10-¾ inch diameter bottom, and is 15 inches in
height.
The Carbon Media provided within the Carbon Canister is virgin, granular, bituminous coal
derived activated carbon. Please find the table below summarizing the Carbon Media
specifications:
Carbon Media (Activated Carbon) - Specifications
Volume Supplied (ft3) 0.62
Weight Supplied (lbs) 20
Butane Activity (wt. %) 15.6 (minimum)
Hardness Number 97 (minimum)
Iodine Number (mg/g) 800 (minimum)
Ash (wt. %) 7 (maximum)
Apparent Density (g/cc) 0.56 (minimum)
Mean Particle Diameter (mm) 3.7 (minimum)
Minimum Hydrogen Sulfide (H2S) Capacity (g/cc) 0.09
