TM 5-813-3/AFM 88-10, Vol 3
very similar as far as disposal techniques are con-
crease the solids content prior to placement in a land-
fill. Inasmuch as diatomite sludges are usually rela-
cerned. Methods of brine disposal include regulated
discharge to surface waters, deep well injection,
tively innocuous, it may be possible to construct ala-
"evaporation" pond disposal, and discharge to a sani-
goon, use it until it is filled with sludge, and abandon
tary sewer. If pond disposal is utilized, the ponds must
it. This can be done only if land is readily available for
lagoons. If land is not available, lagoons must be al-
be lined to prevent seepage of brine into the ground
water, Depending on the location of the water treat-
ternatively filled, dried, and cleaned of settled diato-
ment plant and the volume of brine generated, these
mite sludge, with the removed sludge taken to a land-
fill.
methods may vary widely in cost, reliability, and en-
b. Filter wash water. Wash water volumes range
vironmental acceptability.
from about one to three percent of the raw water proc-
(1) Discharge to surface waters. Unregulated dis-
essed. Disposal of filter wash water may be by dis-
charge to surface waters is usually unacceptable. An
charge to natural receiving waters, by recovery and re-
exception is that waste brines from a desalting plant
near the ocean can probably be discharged to the ocean
use of the wash water, by lagooning, or by discharge to
a sanitary sewer,
if precautions are taken in the design of the outfall to
(1) Discharge to natural receiving waters. This
ensure that the brine is adequately diluted. On large
means of disposal may be practiced only with the ap-
rivers, it maybe possible to store wastes in watertight
proval of the appropriate State and Federal regulatory
ponds during low-flow periods and release them at a
agencies.
controlled rate during high flows. This may be an ac-
(2) Recovery and reuse. Recovery and reuse are ac-
ceptable procedure if it can be shown that the wastes
complished by mixing the filter wash water with the
do not significantly affect water quality when released
influent raw water before or at the rapid-mix basin. In
during the high-flow period.
most cases, the wash water is collected in a recovery
(2) Deep well injection. In order to determine the
basin from which it is pumped into the plant raw wa-
feasibility of using deep well injection for brine dispos-
ter inflow. Suspended solids in the wash water settle
al, it must first be ascertained whether or not a suit-
along with other solids in the plant basins and the only
able subsurface formation is present. Such a formation
wastewater discharged from the plant is that associ-
must be porous, of large extent, and completely sealed
ated with basin sludge removal. The recycling of filter
off from any potential fresh-water aquifiers. The
wash water serves as a water conservation technique
wastes may require treatment prior to injection to
and may have economic advantages over other means
avoid clogging the receiving formation. The costs of
of disposal. In some instances, the suspended particles
deep well injection are dependent chiefly on disposal
in the filter wash water may not settle out easily, and
volumes, treatment requirements, well depths, and in-
recycling may, under some circumstances, cause abbre-
jection pressures. All deep well injection projects must
viated filter runs. Another potential drawback of wash
meet appropriate State and Federal regulations.
water recycling, particularly if the raw water has a
(3) Evaporation ponds. Evaporation ponds can be
high plankton count, is a build-up of algae in the recy-
used for disposal of waste brines if evaporation rates
cled suspended matter and consequent increase of
are high, precipitation is minimal, and land costs are
taste and odor in the water.
low. This method usually involves large capital ex-
(3) Lagooning. Lagooning is an accepted means of
penditures because of the large surface areas required
managing filter wash water flows. If a separate lagoon
and also because of the pond linings required to retard
is used for the wash water, the supernatant from the
seepage. In most localities, precautions must be taken
lagoon may be recycled through the water treatment
to insure that brine ponds do not overflow or leak into
plant.
the ground water. Watertight ponds are required for
(4) Discharge to sanitary sewer. Filter wash water
most situations.
may also be discharged to a sanitary sewer. Rate of
(4) Discharge to a sanitary sewer. Disposal by
flow regulation generally will be required to avoid
regulated discharge to a sanitary sewer may be prac-
sewer surcharge. This mode of disposal is most appli-
ticed if wastewater treatment plant operating person-
cable if the characteristics of the wash water make it
nel and regulatory authorities approve. Conventional
unsuitable for recycling.
wastewater treatment processes do nothing to remove
c. Waste brines. Two types of brine flows can be
dissolved minerals from water. Hence, all of the dis-
generated at water treatment plants, regeneration
solved salts discharged to the sanitary sewer will even-
brines from cation-exchange softeners and waste
tually be present in the effluent from the wastewater
brines from desalination processes. These brines are
treatment plant.
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