N.J. Admin. Code § 7:14A-23.26

Current through Register Vol. 56, No. 21, November 4, 2024

Section 7:14A-23.26 - Anaerobic sludge digestion and management

(a) The Department does not examine plans covering fire and explosive hazards, heat controlling equipment or safety devices and such safeguards are the responsibility of the design engineer.

(b) Supernatant liquor from sludge digestion tanks shall be returned downstream of the influent monitoring points to the raw sewage except that at activated sludge plants, or other plants utilizing air as a method of biological treatment, provisions may be made for disposal in aeration or reaeration tanks. The wastewater treatment facility shall be designed to treat the increased pollutant concentration and hydraulic loading of the supernatant or means shall be provided for separate treatment.

(c) The minimum diameter of all sludge pipes shall be eight inches for gravity flow and six inches for sludge pumping.

(d) A fresh-water hydrant near the sludge digestion tanks is recommended, and, if present, shall be provided with a suitable backflow-prevention device.

(e) Provisions shall be made for the introduction of chemicals into all sludge storage or digestion tanks.

(f) Digesters which are proposed to be utilized to satisfy stabilization requirements shall be designed to meet the requirements for pathogen reduction and vector attraction reduction in accordance with N.J.A.C. 7:14A-20.

(g) Sludge digestion tanks shall be in conformance with the following:

1. Two or more separate units shall be provided, a single digestion tank may be approved if the plan and report show all emergency provisions and the proposed use is for small installations (design capacity of less than 150,000 gpd) where alternate sludge storage is available for emergency use without creating a local nuisance, and where pumps and piping are available for such emergency.

2. Suitable equipment to insure mixing or circulation of the tank contents shall be provided for primary digesters.

3. The proportion of tank depth to area shall be such as to permit the formation of a reasonable depth of supernatant liquor.

4. Tank bottoms shall slope toward the withdrawal pipe not less than three inches per foot. Flat bottom tanks will not be approved.

5. At least two access manholes of adequate size shall be provided in the top of the digester in addition to the gas dome. An access manhole in the side wall of the tank is recommended.

6. In the case of multiple tanks, a provision shall be made to direct the raw sludge to any tank. In circular tanks the raw sludge inlet shall be at a point that is removed from the overflow or supernatant draw-offs by a distance at least equal to the radius of the tank. In rectangular tanks the raw sludge inlet shall be at the opposite end from the overflow and digested sludge draw-off lines.

7. An emergency overflow shall be provided. Provisions shall be made for sampling and removal of supernatant from several levels.

8. Means shall be provided for sampling of digested sludge in accordance with 7:14A-23.14. Digested sludge withdrawal piping shall extend from the center and bottom of circular tanks. Means shall be provided for backflushing digested sludge withdrawal piping. Adequate transfer piping shall be provided.

9. Unheated primary anaerobic digestion tanks will not be approved.

10. The mixing of the contents of anaerobic digesters by air is prohibited.

(h) Separate sludge digestion capacity shall be in conformance with the following:

1. Separate sludge digestion capacity shall be as follows, unless acceptable justification is submitted for an alternate design:

Type of Plant	Minimum Cubic Feet per
Capita
Primary	2 to 3
Primary plus standard filter	2.5 to 3
Primary plus high rate filter	3 to 4
Chemical coagulation	4 to 6
Activated sludge	4 to 6

2. Larger volumes of sludge digestion capacity shall be provided for smaller plants.

3. The sludge digestion capacity shall be increased when industrial wastes and/or garbage solids are present, and may be reduced if the sludge is thickened. Volumes shall be computed on the basis of the bottom sloping up 30 degrees from the horizontal unless mechanical sludge collection is employed.

(i) Anaerobic digestor gas collection shall meet the following general requirements:

1. Waste gas burners shall be provided for excess gas.

i. Burners shall be placed at least 25 feet away from structures if placed at ground level, or may be located on roofs of buildings provided they are remote from digestion tanks.

ii. Burners shall be equipped with pilot lights and means for igniting manually, and shall be equipped with flame traps.

2. All enclosures containing gas piping or apparatus shall be equipped with forced draft ventilation either of the wind-driven or motor-operated type. If of the motor type, the design shall be such that the motor does not come in contact with gases; or spark-proof motors shall be used.

3. A gas meter shall be provided and a bypass installed.

4. Boilers utilizing gas shall be located in a separate enclosure having adequate means of ventilation and preferably located at ground level.

5. All gas lines shall have suitable flame traps and other safety equipment.

(j) Anaerobic digestor heating shall meet the following general requirements:

1. Preference shall be given to means of external heating by means of a heat exchanger. Heating capacity shall be adequate to maintain sludge at 85 to 95 degrees Fahrenheit at all times. Suitable controls shall be provided for automatic operation.

2. Thermometers shall be provided to show temperatures of sludge in the digester, and the sludge going to and from the heat exchanger. Thermometers shall also be provided to show the temperature of the water going to and from the heating coils or heat exchanger.

3. An auxiliary fuel shall be provided, such as oil or commercial gas.

N.J. Admin. Code § 7:14A-23.26

Amended by R.1997 d.107, effective 5/5/1997.
See: 28 New Jersey Register 380(a), 28 New Jersey Register 2779(a), 28 New Jersey Register 3494(a), 28 New Jersey Register 3858(a), 28 New Jersey Register 4697(a), 28 New Jersey Register 5028(a), 29 New Jersey Register 1704(a).
In (f), substituted N.J.A.C. reference for CFR, Statewide Sludge Management Plan, and U.S.C.A. references.