Section 910. Aeration. (Also see 12VAC5-590-970.)

Aeration treatment devices as described herein may be used for oxidation, separation of gases or for taste and odor control.

A. Natural draft aeration.

The design of natural draft aeration shall provide the following:

1. The water shall be distributed uniformly onto the top tray;

2. The water shall be discharged through a series of three or more trays with the separation of trays not less than six inches;

3. The trays shall be loaded at a rate ranging from one gallon per minute to five gallons per minute for each square foot of total tray area;

4. The trays shall have slotted, woven wire cloth, or perforated bottoms;

5. The perforations shall be 3/16 to ½ inches in diameter and spaced one to three inches on centers when perforations are used;

6. Eight to 12 inches of inert media shall be used, such as coke or limestone which shall be two to six inches in size, and will not readily disintegrate due to freezing cycles;

7. The aerated water shall receive disinfection treatment; and

8. The trays shall be designed using materials resisting deterioration with consideration being given to corrosion, slime, and algae control.

B. Forced or induced draft aeration devices shall be designed to:

1. Provide an adequate liquid distribution and countercurrent of air through the enclosed aeration column;

2. Be insectproof and lightproof;

3. Be such that air introduced into column shall be screened through insect proof screen and be as free of dust as possible;

4. Ensure that water outlet is adequately sealed to prevent unwanted loss of air; and

5. Ensure that the sections of the aerator can be easily reached and removed for maintenance.

C. Pressure aeration may be used for oxidation purposes if a pilot plant study indicates the method is applicable; it is not acceptable for removal of dissolved gases. Filters following pressure aeration shall have adequate exhaust devices for release of air. Pressure aeration devices shall be designed to:

1. Give thorough mixing of compressed air with the water being treated; and

2. Provide screened and filtered air, free of obnoxious fumes, dust, dirt, and other contaminants.

D. Other methods of aeration may be used if applicable to the treatment needs. Such methods include, but are not restricted to, spraying, diffused air, and mechanical aeration. The treatment processes shall be designed to meet the particular needs of the water to be treated and are subject to the approval of the division.

E. Aerators that discharge through the atmosphere should be protected from wind by being placed in a louvered enclosure designed to provide easy access to the interior.

F. 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.

G. Ventilation shall be provided to prevent the accumulation of released gases in the building housing the treatment facilities.

H. A bypass should be provided for all aeration units.

Historical Notes

Derived from VR355-18-009.07 § 3.28, eff. August 1, 1991.

Statutory Authority

§ 32.1-12 and 32.1-170 of the Code of Virginia.