| (D) Sludge removal. A splash block or slab shall be
provided at the point where digested sludge is discharged onto each
of the beds. Appropriate means shall be provided to facilitate the
removal of the dried sludge from the beds for disposal without bed
damage resulting. Every sludge drying bed should include a removal
gate or stop planks in one end to provide access for machinery and
trucks to remove and haul away the dried sludge.
(E) Media. A minimum depth of 12 inches of filtering
material, of which four to six inches is coarse sand, is required.
To exclude surface water and eroded earth, the bed shall be protected
by a permanent wall which shall extend at least 12 inches but not
more than 24 inches above the finished surface of the beds.
(2) Vacuum filters, belt filters, belt filter presses,
and other mechanical dewatering filters.
(A) Multiple units. Where dewatering of sludge is proposed,
the design engineer shall provide data to document sufficient capacity,
alternate disposal means, or storage facilities capable of maintaining
normal daily operations during breakdowns, upsets, etc.
(B) Filtrate. The filtrate from the filters shall be
returned to the head of the treatment works or to the aeration system.
Consideration shall be given to the impact of the returned filtrate
on the treatment units and to providing odor and insect control facilities.
(3) Portable dewatering units. If sludge is to be treated
using portable mechanical dewatering units, provisions shall be made
in the facility plan or preliminary engineering report for the location
and connection of the portable dewatering unit(s) during facility