N.J. Admin. Code § 7:14A-23.28 - Drying beds for residuals
(a) The following
table of requisite areas applies to domestic sewage, the sludge of which is
digested by an anaerobic method. Based upon the physical and chemical
characteristics of the residual (for example, domestic/industrial, solids
concentration, and/or method of prior stabilization) appropriate adjustments
can be made to the following table. Written justification for any adjustments
or alternative designs shall be provided in the engineer's report. However,
under most circumstances drying beds will not be approved for dewatering
unstabilized sewage sludge unless appropriate provisions to control odors have
been included.
Area in sq. ft./capita | ||
Open | Glass | |
Type of Treatment | Beds | Covered Beds |
Primary | 1.50 | 60 percent |
Standard Rate Filter | 1.75 | of the area |
High Rate Filter | 1.75 | of open |
Activated Sludge | 2.00 | beds |
Chemical Precipitation | 2.25 |
(b)
The following are minimum requirements governing the design of drying beds and
phragmites reed beds:
1. Not less than two
beds or compartments shall be provided;
2. For conventional sand drying beds:
i. Gravel shall be at least 12 inches deep
with the top at least six inches above underdrains. Gravel shall be graded from
1/8 to one inch in effective diameter; and
ii. Depth of sand shall be at least six
inches and shall consist of clean coarse sand.
3. All drying beds shall be provided with
underdrains of bell and spigot vitrified clay tile pipe, porous tile,
perforated pipe, or other suitable material or drainage. Lateral drains shall
be at least four inches in diameter laid with open joints. An acceptable
engineering fabric shall be provided around joints. Drains shall be spaced not
more than eight feet apart on center and have a minimum slope of one
percent.
4. The permeability of the
bottom and side walls shall not be greater than 1 x 10[LESS THAN]-7[GREATER
THAN] cm/sec and shall extend 15 to 18 inches above the sand surface. Walls
shall be at least six inches above the surrounding ground elevation to prevent
soil from washing on beds;
5. Means
shall be provided to facilitate the removal of dried sludge from drying
beds;
6. Influent piping shall
provide for uniform distribution of residuals across the entire drying bed
area. Splash slabs shall be provided.
7. Residual bed effluent shall be treated and
suitable means shall be provided for the satisfactory management of the
residual cake.
8. The capacity of
the beds shall be sufficient to process the residuals generated to prevent any
day to day accumulations.
9. Drying
beds 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. For Phragmites reed beds, a
minimum capacity to allow three weeks between loadings to the same bed at the
projected sludge production shall be provided. Additional capacity to allow for
bed evacuation is recommended.
Notes
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.
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