UFC 3-280-04
17 DEC 2003
than 1000 mg/L TSS. Precoat filters are not within the scope of this document, but are
discussed in TM 5-662.
3-3
PILOT STUDIES. No completely adequate theoretical approach is available
for the design of full-scale filters. Past experience with similar applications usually pro-
vide adequate basis for design. However, where the waste stream is unusual or experi-
ence is inadequate, pilot studies may be done to ensure that the selected design per-
forms satisfactorily. Generally, pilot studies are not done, but, when essential, they are
done by the filter manufacturer and are required as part of the specification submittal
approval process. The principal goals of the testing should be selecting filter media and
depths, determining appropriate filtration rate and terminal head loss, and establishing
the expected duration of the filter runs. Pretreatment needs may be tested via bench-top
treatability tests.
Pilot studies are often conducted on a column. Experience indicates that a
column with a diameter of at least 15 cm (6 in.) satisfactorily simulates a full-scale filter.
Columns of smaller diameter may result in wall effects and can produce data that may
not be representative of full-scale operation. A column with a diameter of at least 30 cm
(1 ft) can be used to determine backwashing characteristics. Most pilot studies have
been conducted on columns constructed of transparent rigid plastic tubes, fitted with
plastic flanges at top and bottom and a perforated-plate underdrain to support the filter
media. Column height will depend on the design depth of media. The vertical dimen-
sions should fully simulate the conditions to be expected during full-scale operation. The
testing shall be of sufficient duration to cover the range of conditions to expect (e.g.,
temperature, water quality variations). Detailed information regarding pilot testing is pre-
sented in Hudson (1997), Water Clarification Processes: Practical Design and Evalua-
tion.
Alternatively, studies may be run either on pilot filters or on the unit itself to
help optimize performance. This is the preferred method for cartridge or bag filters. In
the case of low flows (less than 15 L/s), pilot testing may not be cost effective. In such a
case, the filter design should be conservatively sized, based on previous similar experi-
ence elsewhere. Information regarding prior testing and operation may be available
from equipment vendors.
3-9
Previous Page
