Section 811.45. Aeration.

  Aeration treatment devices described in this section may be used for oxidation, separation of gases, or for taste and odor control. Air stripping towers shall meet the requirements of s. NR 811.53 (2) , which can be used for the removal or reduction of some volatile organic compounds. The following requirements shall be met:

(1)   Natural draft aeration. The design for natural draft aeration shall provide that:

(a) Water is distributed uniformly over the top tray.

(b) Water is discharged through a series of 3 or more trays with separation of trays not less than 6 inches.

(c) Trays are loaded at a rate of one to 5 gallons per minute for each square foot of total tray area.

(d) Trays have slotted, heavy woven wire mesh with 0.5-inch openings or perforated bottoms.

(e) Perforations are 3 / 16 to 1 / 2 inches in diameter, spaced one to 3 inches on centers, when perforations are used.

(f) Construction is of durable material resistant to the aggressiveness of the water and dissolved gasses.

(g) Contamination from sources such as those listed is sub. (7) is minimized by providing down-turned, louvered or hooded, screened air inlet or outlet openings. Screens shall be constructed of 24-mesh corrosion resistant material.

(h) Exhaust air is discharged directly to the outside atmosphere and in a location that will be protective of public health.

(2)   Forced or induced draft aeration. The design for forced or induced draft aeration shall provide that:

(a) Water is distributed uniformly over the top tray.

(b) The blower and blower motor are weatherproof and are installed in a weather-tight, screened enclosure.

(c) There is an adequate countercurrent flow of air through the enclosed aeration column.

(d) Aerator trays are loaded at a rate of one to 5 gallons per minute for each square foot of total tray area.

(e) Water will discharge through a series of 5 or more trays with separation of trays not less than 6 inches or as approved by the department.

(f) Construction is of durable material resistant to the aggressiveness of the water and dissolved gasses.

(g) The aerator is insect-proof, watertight, and light-proof.

(h) The air intake is located above grade and the air introduced into the column is as free as possible from contamination sources such as those listed in sub. (7) .

(i) The water outlet is adequately sealed to prevent unwanted loss of air.

(j) Interior and exterior sections of the aerator can be easily reached or removed for maintenance.

(k) Contamination from sources such as those listed in sub. (7) is minimized by providing down-turned, louvered or hooded, screened air inlet or outlet openings. Screens shall be constructed of 24-mesh corrosion resistant material.

(L) Exhaust air is discharged directly to the outside atmosphere and in a location that will be protective of public health.

(3)   Pressure aeration. Pressure aeration installations shall meet the following requirements:

(a) Pressure aeration may be used for oxidation purposes. Pressure aeration will not be approved for removal of dissolved gases.

(b) Filters following pressure aeration shall be provided with adequate exhaust devices for release of air.

(c) Pressure aeration devices shall be designed to cause a thorough mixing of compressed air with the water being treated.

(d) Pressure aeration devices shall provide screened and filtered air that is free of obnoxious fumes, dust, dirt, and other contaminants.

(e) Air compressors supplying pressure aerators shall be oil-less.

(4)   Other methods of aeration. Other methods of aeration may be approved by the department only if a pilot plant study conducted in accordance with s. NR 811.44 demonstrates the method's effectiveness. Methods include spraying, diffused air, and mechanical aeration. The treatment processes shall be designed to meet the particular needs of the water to be treated.

(5)   Disinfection. Aerated water other than from pressure aeration shall receive continuous disinfection treatment. A corporation stop shall be provided on the inlet piping to all non-pressure aerators to allow disinfection for emergency or maintenance purposes.

(6)   Protection from wind. Aerators that discharge through the atmosphere shall be protected by being placed in a louvered enclosure designed to provide easy access to the interior.

(7)   Protection from contamination. Aerators that are used for oxidation or removal of dissolved gases from waters that will be given no further treatment other than chlorination shall be protected from contamination from insects and birds, obnoxious fumes, all types of precipitation and condensation, and windborne debris or dust.

(8)   Bypass piping. Bypass piping and any associated valves or other appurtenances shall be installed to allow water to be bypassed around a non-pressure aerator unless the aerator is necessary to comply with primary maximum contaminant levels or the requirement is waived by the department because the water system has access to other water sources that can provide at least an average day supply of water.

(9)   Redundancy. Redundant aeration systems shall be provided for units installed to comply with primary maximum contaminant levels unless the requirement is waived by the department because the water system has access to other water sources that can provide at least an average day supply of water.

(10)   Water quality. A metal smooth-end sampling faucet installed on the aerator outlet piping and test equipment shall be provided to test for appropriate water quality parameters following aeration such as dissolved oxygen, pH, iron, manganese, radon gas, and carbon dioxide when required by the department to insure proper operation of the aeration equipment.

History: CR 09-073 : cr. Register November 2010 No. 659 , eff. 12-1-10.