MIL-HDBK-1005/9A
Some common design criteria are: the soil must be
reasonably porous, and the bottom of the lagoon must be at least
18 inches (45 cm) above the maximum ground water table.
Surrounding areas must be graded to prevent surface water from
entering the lagoon. The lagoon depth should not be more than 24
inches (61 cm). At least two lagoons should be provided.
Sludge usually will not dewater in any reasonable period
of time in lagoons (to the point that it can be lifted by a fork
except in an extremely hot, arid climate). If sludge is placed in
depths of 15 inches (36 cm) or less, it may be removed and
dewatered in 3 to 5 months.
3.10.8.3 Mechanical Dewatering and Disposal. Consider filter
press equipment in locations where sludge drying beds cannot be
used.
a) Bag Filters. In smaller facilities where sludge
production is low, bag type filter presses should be considered.
They dewater by moisture displacement under pressure from influent
liquid sludge. Bag type filter presses generally dewater to about
50 percent moisture content. They are mechanically simple and
require little maintenance other than periodic cleaning. The
operation is normally manual and requires continuous operator
attention to start and stop the process, and to empty and replace
the filter bag. They are small, portable, and require little
floor space for a permanent installation.
b) Filter Press. For larger facilities with higher
sludge production, consider a plate and frame (or diaphragm)
filter press. A plate and frame press will require high lime
dosage. As an alternate, select type and feed rate of organic
polyelectrolyte. Use a diatomaceous earth precoat filter to
minimize oil blinding of the filter fabric. Consider high-
pressure air or steam cleaning of the fabric in a regular
operating cycle. Consider operational problems of media blinding
and cake handleability in selection of the filter press, as for
other mechanical dewatering equipment.
167
Previous Page
