Current through Register Vol. 56, No. 18, September 16, 2024
(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.
