Intermittent sand filters provide
biodegredation or decomposition of wastewater constituents
by bringing the wastewater into close contact with a
well developed aerobic biological community attached
to the surfaces of the filter media. This process requires
unsaturated downward flow of the effluent through the
filter media. The filter media may be a mineral sand
or equivalently sized crushed glass meeting one of the
media specifications listed in the state guidlines,
Appendix A. The media is contained in a watertight vessel
either below the surface of the ground or wholly or
partially elevated in a containment vessel. Proper function
requires that influent to the filter be distributed
over the media in controlled, uniform doses. In order
to achieve accurate dosing, these systems require a
timer controlled pump with associated pump chambers,
electrical components and distribution network, with
a minimum of 4 doses per day spread evenly over a 24
hour period. The effluent is collected in the bottom
of the filter and discharged either by gravity or pressure
to a suitable disposal component, usually a conventional
sub-surface drainfield.
This technology is used
on sites with shallow soil conditions where treatment
must be accomplished before disposal. Sand filter effluent
may be discharged to as little as 12 inches of vertical
separation. Intermittent sand filters are also used
as part of a mitigation strategy when horizontal separations
are reduced.
To view the
complete Recommended
Standards and Guidance for Performance, Application,
Design, and Operation and Maintenance of the Intermittent
Sand Filter Systems you may follow the following links:
