| Treatment
Technology: Single
pass sand filter |
Single
pass sand filter technology has been used for over 100 years
to treat both wastewater and drinking water supplies because
they are quite effective in removing bacteria. The term “sand
filter” refers to a biological and physical wastewater
treatment component consisting of an underdrained bed of
sand to which septic tank effluent is periodically applied.
Wastewater is time dosed to the top of the filter bed and
percolates down through the sand media where wastewater treatment
occurs. Filtrate is collected in the underdrain at the base
of the filter and then pressure dosed to a shallow narrow
drainfield for final dispersal. |
 Cut-away
view of the filter showing the PVC pipe distribution
system, sand media in the foreground, and the over-lying
3 inches of crushed stone. |
|
This
image shows a completed filter, which is flush with the
ground surface
and covered by grass.
|
| A
treatment train containing a single pass sand filter |
Wastewater
flows through a building sewer (A) and enters into a two-compartment
septic tank (B). Septic tank effluent is pressure dosed using
a time dosed pump located in the second compartment of the
tank. Effluent is distributed over the top of the sand filter
(C), infiltrates the sand media flowing down to the base
of the filter. Filtrate collects in a sump area in the middle
of the filter, where a second pump is located. This pump
pressure doses sand filter effluent to a shallow narrow drainfield
(D) where additional treatment and final dispersal occurs. |
|
| Treatment
performance observed for single pass sand filters in RI |
| System |
BOD5 |
TSS |
TN |
% TN Reduction |
Fecal Coliform |
Coming Soon! |
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| For
more information on single pass sand filters: |
Web
Links:These media filters have been studied under
various URI-lead projects, as well as by other onsite treatment
testing facilities. The results of URI, NEOWTC projects can be
found in various technical publications which will be online
soon at www.uri.edu/ce/wq/OWT/Research/
|
