TM 5-813-8
The area must be checked for geologic faults and any
10-3. Distillation / condensation system wastes .
manmade penetrations of the aquiclude. The brine
The
waste
stream
volume
produced
by
must contain less than 15 milligrams per liter of
distillation/condensation systems is usually less than
suspended solids, with a maximum size of 20 microns.
that produced by other desalination processes. The
Figure 10-3 shows a typical injection well.
High
vaporization process yields concentrated brine with a
construction and operating costs and the potential for
reduced liquid waste loading. The use of less extensive
serious operational problems usually cause deep-well
pretreatment requirements for these systems generally
injection to be the last process selected. If deep-well
results in a reduction of solid wastes. The cooling water
injection, evaporation, or return-to-source liquid-disposal
discharge produced by many distillation processes does
options are not possible, review the entire facility
present a separate thermal discharge problem.
location.
a. Brine return to source.
The brines from
d. Dried salts. When evaporation processes have
distillation/condensation
processes
are
highly
reduced the brines to dry salts, make evaluations to
concentrated. For this reason, brines will be discharged
determine a market value for these salts, as some salts
where contamination of the intake water will not occur.
have a value when dried. A landfill operation must be
The liquid brines will be returned to the raw water source
maintained when no market value can be assigned to
if impact studies show there will be no significant
the dried salts. An overview of brine wastes disposal is
environmental impact. Wetlands and estuarian areas
shown in figure 10-4.
that are often used for discharge are usually productive
e. Use of brine. Desalination evaporation ponds
growth sites for many valuable food species. These
make excellent solar stratification ponds. These ponds
areas are easily damaged by thermal discharges and
can be used to produce a stored thermal energy
require study to ensure that they are acceptable disposal
gradient, which can be harvested with a Rankin cycle
areas for concentrated desalination waste liquids.
engine. Electricity from such a system can be used to
b. Brine evaporation. If it is not feasible to return
electrolytically produce chlorine. The total disposal of
the brines to the raw water source, then consider the use
brine by chlorine production is not expected to ever be
of evaporation ponds to dry the liquid wastes. The
economical for the military. The internal production of
thermal
nature
of
the
brine
from
most
chlorine for water disinfection is strategic. Presently, the
distillation/condensation systems can aid evaporation of
smallest systems available produce over 22 pounds of
the wastes to dry salts. In areas where the net
chlorine per day. The brine concentration must be
evaporation rate is low, but thermal energy sources are
greater than above 35,000 milligrams of total dissolved
available, use thermal evaporation.
Thermal
solids to be practical. Any hardness in the brine limits
evaporation has high energy requirements and usually is
efficiency and causes scaling.
not cost-effective.
f. Cleaning wastes.
At regular intervals,
distillation systems must be cleaned. This usually
brine to a surface water or evaporation is impractical or
involves strong acid cleaning solutions. These solutions
uneconomical, deep-well injection of brines is possible.
must be neutralized and may require lime precipitation
The injection of liquid wastes to deep underground
of heavy metals before they can be discharged. These
formations can provide a disposal alternative where
wastes can be dried in evaporation ponds or disposed of
none was previously available. To properly design and
in injection wells. The volume of cleaning waste is small
install a deep-well injection facility, a complete geologic
enough that transportation of the cleaning wastes to
and geochemical analysis of the reservoir formation is
commercial hazardous waste disposal facilities is a third
required. Volumes of less than 53 gallons per minute
alternative. The operation of pretreatment scale control
can be disposed of practically in injection wells, while
can reduce the frequency of cleaning.
volumes in excess of 264 gallons per minute will be
g. Gases.
Gas wastes from desalination
much more difficult to dispose of by use of this method.
processes are removed from the system during
Compatibility tests must be run between the proposed
deaeration or distillation. These gases include
waste and a sample of the formation water. This test
should ensure that the two waters do not react to form
precipitates that may clog the receiving formation. The
receiving formation must be separated from any fresh
water or the desalination source water by an aquiclude
that will ensure that the brine will not contaminate them.
10-3
Previous Page
