N.J. Admin. Code § 7:14A-23.22 - Intermittent sand filters

(a) For intermittent sand filters, at least two filter units shall be provided.

(b) Sod and similar coverings over intermittent sand filters are prohibited.

(c) Loading requirements for intermittent sand filters are as follows:

1. Organic loading of five-day B.O.D. shall not exceed 3.8 pounds per 1,000 square feet per day;

2. With acceptable primary treatment of normal sewage, volumetric loading shall not exceed 2,875 gallons per 1,000 square feet per day. For stronger sewage the rate of filtration shall be proportionately lower.

3. For chemical coagulation and sedimentation the volumetric loading shall not exceed 5,750 gallons per 1,000 square feet per day.

4. For standard or high rate trickling filters or activated sludge followed by secondary settling tanks, the volumetric loading shall not exceed 9,200 gallons per 1,000 square feet per day.

5. For schools, camps, and institutions, not having a full-time treatment plant operating staff, volumetric loading should not exceed 1,150 gallons per 1,000 square feet per day for primary tank effluent.

(d) Intermittent sand filter media shall be in conformance with the following:

1. Clean graded gravel shall be placed in at least three layers over the entire floor of the bed and around the underdrains and to a depth of at least six inches. Grading for the three layers shall be 1 1/2 inches to 3/4 inch, 3/4 inch to 1/4 inch and 1/4 inch to 1/8 inch.

2. Underdrains shall have maximum spacing not exceeding six feet and shall be at least four inches in diameter, or of equivalent area.

3. Pipes shall be laid on a firm base with open joints with a space of approximately 1/4 inch between ends.

i. A single layer of muslin, cheese cloth, burlap or other suitable material shall be wrapped around each joint of open joint underdrains.

ii. Tar paper or other waterproof material may not be used.

iii. Perforated clay or other approved perforated pipe may be used for underdrains.

4. Sand with an effective size of 0.3 to 0.6 millimeters and a uniformity coefficient of not more than 3.5 shall be provided to a depth of at least 30 inches. The sand shall be free from clay, loam or silt.

(e) Intermittent sand filter dosing shall be in conformance with the following:

1. A dosing tank or its equivalent with a capacity to dose each filter at least twice a day shall be provided. Where practical, a dosing tank or equivalent shall have a maximum detention time of two hours based upon the design flow.

2. The dosing tank volume shall be such that each filter bed will be covered to a depth not less than two nor more than four inches with each dose.

3. Siphons shall have a discharge capacity, at minimum head, of at least 100 percent in excess of the maximum rate of inflow to the dosing tank, and at average head, at least one cubic foot per second per 5,000 square feet of each filter bed.

(f) Intermittent sand filter distribution shall be in conformance with the following:

1. A rotary distributor may be used if nozzles are adjusted so flow will not erode the sand bed.

2. Troughs or piping used for distribution of the settled sewage over the filter surface shall be so located that the maximum lateral travel distance is not more than ten feet. Provision shall be made at each discharge port for adjustment of the flow.

3. Splash slabs shall be provided at each point of discharge.

4. A drain opening from troughs or discharge piping shall be provided.

(g) The base of the filter shall be either enclosed with concrete or lined with a material that has a permeability no faster than 10[LESS THAN]-7 cm[GREATER THAN]/sec.

(h) Rapid sand filter design shall be in conformance with the following:

1. The use of rapid sand filters may be considered where treatment beyond secondary treatment is required and where skilled operational personnel will be present.

2. In general, rates shall not exceed three gallons per square foot per minute; backwash facilities shall be provided; the sand bed should not be less than 20 inches in depth; and suitable underdrainage of graded gravel shall be provided.

3. Operating head on the filter shall not exceed eight feet.

(i) The use of micro-strainers is acceptable when additional treatment such as reduction in B.O.D. and suspended solids is required after secondary treatment and final settling, and will be considered when accompanied by an engineer's report that contains complete data on the installation and accompanied by suitable plans.

Notes

N.J. Admin. Code § 7:14A-23.22