N.J. Admin. Code § 7:14A-23.19 - Trickling filters

(a) Trickling filters of the "standard rate" or "high rate" type may be used for the treatment of sewage amenable to treatment by a biological process.

(b) Filters shall be preceded by effective preliminary treatment and shall be followed by individually controlled and mechanically cleaned settling tanks.

(c) When the average five-day B.O.D. of the raw sewage exceeds 325 parts per million, two stages of trickling filter treatment are required, with or without intermediate sedimentation. Consideration may be given to designs providing supplementary preliminary treatment in the case of strong sewages or industrial wastes.

(d) The sewage shall be distributed uniformly over the filter so that at least 95 percent of the surface area receives sewage directly.

1. Distribution devices may be actuated by twin siphons, pumps or gravity discharge from preceding treatment plant units.

(e) The filter media may be crushed rock, manufactured material, or other approved material. Manufactured media shall be resistant to ultraviolet degradation, disintegration, erosion, aging, all common acids and alkalies, organic compounds, and fungus and biological attack. In addition, manufactured media shall be structurally capable of supporting a person's weight or a suitable walkway shall be provided to allow for distributor maintenance.

1. Where applicable, the upper 18 inches of the filter bed shall have a loss, measured by the 20-cycle sodium sulfate test, of less than ten percent and the balance shall pass the 15-cycle test.

2. Wear shall not exceed 20 percent after 500 revolutions of Los Angeles Rattler Test as determined by the current ASTM Standard, Designation No. C-131.

3. Rock media shall be approximately cubical in shape, free from dust, clay, sand or fine material and of a size that passes a four-inch screen and is retained on a 2 1/2 inch screen.

4. Material shall be screened or forked, and washed to remove fine grains and shall be so placed as to avoid breaking the underdrains.

(f) The underdrainage system shall be resistant to the action of sewage wastes and shall cover the entire floor. 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. Use of half-tile for underdrains will not be approved.

1. Lateral underdrains shall have a minimum slope of one percent.

2. Main underdrains and effluent channels shall be designed to provide a velocity of not less than two feet per second.

3. The entire underdrainage system shall be designed to permit free passage of air, and be of such size that not more than 50 percent of the cross sectional area of the flow channels in the underdrains will be submerged during operation of the filter at the maximum design rate. Provisions shall be made for flushing lateral underdrains from the main drain or head channel.

(g) Standard rate trickling filters shall be designed as follows:

1. The volume of sewage to be treated by standard rate filters shall not exceed 14,400 gallons per day per 1,000 cubic feet of filtering media and the average rate of organic loading shall not exceed 15 pounds of five-day B.O.D. per thousand cubic feet per day.

2. The average rate of application during dosing periods shall not exceed 22 gallons per thousand cubic feet of media per minute. The time intervals between dosing cycles to the filter shall not exceed five minutes at design flow.

3. The minimum depth of filtering media at any point in the filter, measured from the top of the underdrains to the surface of the media, shall not be less than five feet, and the maximum depth shall not exceed eight feet.

4. Means for Psychoda fly control, such as provisions for backflooding and filter flushing, shall be provided. The application of chemicals is discouraged unless other forms of control have been ineffective and the use of chemicals shall be in conformance with all other applicable laws, ordinances and regulations.

5. Means shall be provided for recirculating a portion of the effluent from intermediate or final settling tanks during periods of low flow.

6. The Department will consider other suggested loading rates to address manufactured media if supported by appropriate engineering documentation.

(h) High rate trickling filters shall be designed as follows:

1. Organic loading to high rate filters shall not exceed 67 pounds of five-day B.O.D. per thousand cubic feet of filter media per day, based on the total volume of the filters.

2. The depth of filtering media at any point in the filter, measured from the top of the underdrain block to the surface of the media, shall not be less than five feet nor more than eight feet. The distributor shall clear the media by not less than eight to nine inches; and the filter retaining walls shall not be less than three inches higher than the media.

3. High rate trickling filters shall be equipped with rotary distributors and flushing devices shall be provided at the outer end of each distributor arm.

4. Provisions shall be made for controlled recirculation to maintain a continuous application rate of not less than 230,000 gallons per 1,000 square feet per day. Devices to measure flows to the filter and the recirculated effluent shall be provided.

5. The number and capacities of the recirculation pumps shall be such that the conditions of (h)4 above can be met if the largest pump for each point of return is out of service unless other provisions are made which will achieve adequate and effective degree of treatment if power or pump failure occurs.

6. The Department will consider other suggested loading rates to address manufactured media if supported by appropriate engineering documentation.

(i) Under conditions where treatment of unusually strong sewage is necessary and two-stage filtration is adopted, intermediate settling tanks may be required, with suitable sludge and scum removal devices to provide a detention period of one hour based upon projected flow.

Notes

N.J. Admin. Code § 7:14A-23.19