N.J. Admin. Code § 7:10-11.14

Current through Register Vol. 56, No. 12, June 17, 2024

Section 7:10-11.14 - Filtration

(a) General requirements for filtration are as follows:

1. Each filter unit shall be provided with equipment which facilitates cleaning, and placing or replacing the filter medium.

2. Each filter unit shall be provided with equipment for backwash (except for slow sand filtration).

3. Surface water treatment facilities shall be equipped with a continuous or sequencing turbidity monitoring device for each filter unit and a continuous turbidity monitoring device for the plant effluent. The sequencing devices shall automatically analyze and record each filter unit effluent turbidity at least once every 15 minutes.

(b) Total filtration capacity shall be such that, with one unit out of service, the maximum filtration rate of any of the remaining units will not exceed the requirements established at N.J.A.C. 7:10- 11.14(c)2.

(c) Filter unit design requirements are as follows:

1. Filter units shall not contain any contamination hazards, single walls between treated and untreated water, or plumbing cross connections.

2. Pressure filtration rates shall not exceed a loading rate of three gallons per minute per square foot unless approved by the Department.

3. Pressure filter units shall not be used for surface water treatment.

4. The filtration rate for rapid sand and mixed media shall not exceed five gallons per minute per square foot.

5. Size requirements for filter media are as follows:

i. For rounded particles, maximum effective size shall be 0.55 mm.

ii. For angular particles, maximum effective size shall be 0.45 mm.

iii. The maximum uniformity coefficient shall be 1.6.

iv. The minimum thickness of filter media shall be 24 inches.

v. The maximum head loss through filter medium shall be eight feet of water.

6. Regulating valves shall be provided for the control of filtration rates.

7. When dual media filters with sand and anthracite beds are used, the anthracite particles may be twice the effective size required under (c)5 above. The sand bed shall be a minimum of 12 inches thick.

8. At least 12 inches of graded gravel shall be placed over the underdrains or another filter media support method specifically designed by the filter media manufacturer shall be used.

9. Slow sand filter units may be used if approved by the Department. The Department shall approve the use of slow sand filters if the applicant demonstrates the adequacy of such water treatment technology through pilot plant tests on the source of water to be treated.

(d) Granular activated carbon (GAC) may be used as a filter medium provided the filter unit meets the filter design requirements of (c) above, and adequately controls bacterial growth in the filtered water, incorporates backwash equipment, and facilitates replacement of medium when necessary.

(e) Regulations for backwash water are as follows:

1. Backwash water shall be filtered water.

2. The available wash rate shall be a minimum of 15 gallons per minute per square foot and shall provide for a minimum of 30 percent expansion of the filter medium. Supplemental washing facilities such as surface wash or air scour units shall be provided.

3. Reduced pressure zone backflow preventers shall be installed to prevent back siphonage of filter surface wash water.

4. Backwash water shall not be discharged to a sanitary sewer system except in accordance with the New Jersey Pollutant Discharge Elimination System rules, N.J.A.C. 7:10-14A, and with written approval from the appropriate sewerage authority. Direct connections between backwash water lines and sanitary or storm sewer lines are prohibited. Discharges shall be made through an above-ground air gap.

N.J. Admin. Code § 7:10-11.14

Amended by R.2000 d.354, effective 8/21/2000.
See: 31 N.J.R. 2717(b), 32 N.J.R. 3106(a).
Amended internal reference.
Amended by R.2001 d.313, effective 9/4/2001 (operative October 4, 2001).
See: 32 N.J.R. 2832(a), 33 N.J.R. 3194(a).
In (a)3, substituted "15 minutes" for "hour".