b. Existing or planned facilities.
Thermal discharge. A problem resulting from
all distillation/condensation facilities is thermal
of energy information.
See sample problem A-8.
discharge of liquids. Older high temperature facilities
Alternative steam sources considered in the design must
produce brine at very high temperatures. Cooling
include steam temperature, steam pressure, and
towers, heat exchangers, or similar equipment must be
available quantity of steam. The design must show
designed into the process to handle the thermal
available electrical power including voltage, amperage,
discharge from distillation/condensation facilities. More
sophisticated desalination units employ a system of heat
available electrical power.
exchange devices that use the raw feed water to cool
c. Raw water information.
One of two
the brine and reclaim this waste heat to help provide
circumstances will limit the quantity of raw water
thermal energy for system operation.
Both of these limitations must be
considered in the design:
Design analysis . When it is necessary to
-The availability of raw water may place a
review several water distillation/condensation designs,
limitation on the raw water used in the
standard dimensionless analysis will be used for design
comparison. If dimensionless correlations for particular
-The maximum amount of waste brine that
aspects of design do not exist, a bench- or pilot-scale
can be economically disposed of may
study should be done.
limit the raw water used in the process.
The principle requirement in a desalination design is an
Materials of construction .
accurate projection of the chemical makeup of the worst
nature of high-temperature brines, acid pretreatments,
quality water that will be used as raw feed water at the
and chemical scaling can cause plant failure. Presently,
site being investigated.
The design must include
the only acceptable construction materials for wetted
consideration of the maximum total dissolved solids,
surfaces in high-temperature systems are an austenitic
individual ions (see App. B), maximum amount of total
stainless steel, such as AISI Type 316L of titanium.
suspended soiled present in the feed water, maximum
Anodized aluminum and many thermoplastic materials
organic contaminant loading, and any gas or potential
are acceptable for use in low-temperature systems.
corrosive agent that may be in the feed water. All
known or anticipated future qualities of the feed water
Distillation/condensation system design .
shall be considered in the design.
Pursuant to finalized site and process selection, one
distillation/condensation system will usually be chosen.
When the process selection does not yield a single
the most economical, then the design will be limited to
process, then designs must be prepared for more than
the single process.
The process design for any
a. Identification of work. When the base site has
required input temperature and some maximum
been selected and a schedule for construction has been
required heat sink temperature. Between these two
prepared, this information will be made available to the
temperature criteria, the process must be capable of
water treatment engineer. The identification of the
producing the required product water quality and
location and the time schedule will be considered in the
quantity. When a particular metallurgy is required for
design; this includes the date the system must be online.
strategic, corrosion design, or economic reasons, this
The minimum number and minimum size of the
metallurgy shall be designated for all applicable parts,
modules will be determined.
Any restrictions that
storage will place on maximum allowable downtime will
must be included in the design. The design must show
also be determined. With distillation/ condensation
the required output water quality based on the worst raw
systems, the design must address the maximum
water input chemistry and quality. The system design
allowable total dissolved solids and, where applicable,
must be based on equipment with a history of successful
the minimum allowable rejection of distillable material.
water treatment system experience.
Distillable material is defined as nonaqueous, volatile
experience history should include a minimum of 2 years
of operating experience meeting water quality and